Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Quantifying the impact of socioeconomic development and climate change on Escherichia coli concentrations in the Pakistani Kabul River
Iqbal, Shahid - \ 2017
University. Promotor(en): Rik Leemans, co-promotor(en): Nynke Hofstra. - Wageningen : Wageningen University - ISBN 9789463434478 - 183
escherichia coli - rivers - climatic change - socioeconomics - water quality - regression analysis - water pollution - health - rivieren - klimaatverandering - sociale economie - waterkwaliteit - regressieanalyse - waterverontreiniging - gezondheid

Clean water is indispensable for the sustenance of life and maintenance of health. However, water quality is threatened by changes in socio-economic developments (population growth, urbanisation, livestock increase and sanitation) and climate (surface air temperature and precipitation patterns). Major water quality contaminants include microorganisms, such as fecal coliforms, Escherichia Coli (E.coli) and pathogens. Microbial contamination poses serious health risks in developing countries like Pakistan, where people do not have access to clean water due to lack of waste water treatment and thorough manure management. Therefore, to reduce the present and future health risk, it is important to understand the impacts of socio-economic development and climate-change on microbial fate and transport in surface water resources in the Kabul River Basin in Pakistan.

The objective of this study is quantifying the impact of socio-economic development and climate change on E.coli concentrations in the Pakistani Kabul River. To reach the objective, I sampled E.coli concentrations at several locations in Kabul River, applied statistical and process based modelling, developed future global change scenarios and analysed the impact of these scenarios on E.coli concentrations. I focus on E.coli rather than pathogens, because sampling of pathogens and its chemical analysis are expensive. Kabul River Basin is a tributary of the Indus river and is located in the Hindukush-Karakoram-Himalayas (HKH) and suffers from floods every year. The population suffers from a high risk of waterborne diseases. The water is contaminated by direct sewage inputs from large cities, like Peshawar, direct manure inputs from animal sheds along the river and indirect manure inputs from the land.

Kabul River Basin is subjected to hazardous levels of microbiological pollution. The concentration of micro-organisms is influenced by hydro-climatic variables, such as water and surface air temperature, precipitation and discharge. However, the net effect of these variables remains thus far unclear. High concentrations of E.coli were found in the main stream and its tributaries (Chapter 2). Samples were collected along the Kabul river and drinking water samples from the city of Nowshera (April 2013 to July 2015) and all surface water samples violate the bathing water criteria and all drinking water samples violate the drinking water criteria. The correlation between hydro-climatic variables and E.coli concentration was analysed. Water temperature and surface air temperature were positively correlated, most likely because high temperatures coincide with high precipitation and discharge. Precipitation and river discharge data were also positively correlated with E.coli concentrations. This shows that precipitation, which increases the surface runoff, transports E.coli and other waterborne pathogens to the river nearby (correlation with precipitation) and further upstream (correlation with discharge). A regression model was also applied that explained 61% of the E.coli variability in surface water and 55% of E.coli variability in drinking water resources, even when other factors, such as location and land-use variables are ignored (Chapter 2).

To better understand the hydrology in the basin, the current and future flows of Kabul river were modelled using the Soil and Water Assessment Tool (SWAT), which serves as a basis for the process-based E.coli model. Flash floods occur every year in the basin as a result of increased discharge due to snow and glacier melt together with monsoon precipitation. The Kabul River Basin is one of the most vulnerable regional basin to climate change. The hydrological model was calibrated and validated for the full Kabul River Basin and performed well (NSE equals 0.77 and 0.72 respectively). Flood frequency and expected return period were analysed for a contemporary period (1981-2000) and two future periods (i.e. 2031-2050 and 2081-2100) using the Representative Concentration Pathway (RCP) 4.5 and RCP8.5 scenarios based on four bias-corrected downscaled climate models (Chapter 3). The flood frequency analysis shows that the present day’s one-in-a-fifty year event could occur between once in every 3 year (EC-EARTH and MIROC climate-models) and once in every 24 years (IPSL climate-model). This study presents climate-change impact assessment in the Kabul River Basin. The selected approach is in general well accepted in the scientific community and the results can be useful in flood management in the region. Outcomes of this study can be helpful for regions that have similar hydro-climatological conditions.

To better understand the fate and transport of bacteria from land to water resources and to assess source contribution, the SWAT model was calibrated and validated for E.coli. Our study is the first bacterial modelling study for the Kabul River Basin (Chapter 4). The simulated concentrations have slightly lower variability than the observed concentrations. The model performance could be improved further by using more input E.coli data, but the current model results agree well enough with our measured E.coli concentrations (NSE equals 0.69 and 0.66 for calibration and validation respectively). Based on the pathogen source estimations, point (direct) sources are identified to be the most important microbial pollution sources. Pollution from upstream areas is also important, while non-point (diffuse) sources play a role mostly during the periods with high discharge. Our study underlines the importance of wastewater treatment and manure management both in and upstream of the study area. Studies like ours were lacking in developing countries like Pakistan and can be used for scenario analyses in the region (Chapter 4). The model can be useful in microbial water quality assessments in other watersheds and for pathogenic microorganisms, such as Cryptosporidium and Rotavirus.

The calibrated and validated SWAT bacterial model (Chapter 4) was used to assess E.coli concentrations in a comprehensive scenario analysis (Chapter 5). We developed two future scenarios based on state-of-the-art approaches, using the Shared Socio-economic Pathways (SSPs), RCPs and own assumptions in line with the SSP storylines. We took the modelled E.coli concentrations from Chapter 4 as baseline scenarios and defines two future scenarios as Scenario_1 (sustainability scenario) and Scenario_2 (uncontrolled scenario). These scenarios represent different socio-economic development and climate change. The two scenarios were developed by combining SSP1, a sustainable, equitable and environmentally focussed world with RCP4.5 (limed climate change) in Scenario_1, and SSP3 (a divided world, with no interest in the environment) with RCP8.5 (strong climate change) in Scenario_2. Currently, no wastewater treatment plant exists in the basin, because the 2010 floods destroyed the available plants. We assumed excellent and poor wastewater and manure treatment for 2050s and 2100s for Scenario_1 and Scenario_2 respectively, in line with the storylines. Scenario_2 resulted in higher E.coli concentrations compared to the baseline scenarios due to high population growth, poor wastewater and manure treatment and land-use changes. However, microbial water quality was found to improve under Scenario_1. This was achieved by implementing improved and technologically advanced wastewater treatment and manure management. Future concentrations were found to be between 0.6% and 7% of the baseline concentrations depending on the treatment technology used (Chapter 5). This study highlights the need for substantial improvements in wastewater and manure treatment systems in the Kabul River Basin to assure future E.coli concentrations in water sources will be within the limits of WHO and US-EPA regulations for drinking and bathing water quality. The primary treatment facility that is currently installed is a good start, but insufficient to strongly reduce concentrations. Hence major investments are required to install technologically advanced wastewater treatment and manure treatment plants to cut-down the current contamination level of Kabul river.

My PhD thesis provides a base for devising optimal coping strategies that are essential for the sustainability of hydrological resources under socio-economic developments and climate-change impacts. The results of our research are helpful to further assess alternative water quality management options. The outcomes of this study also increase the knowledge in the field of microbial fate and transport in water resources in a developing country like Pakistan, where such studies are lacking. A limited number of previous studies on global change impacts on microbial contamination of surface water in other areas of the world focused only on the climate-change impacts on microbial water quality. This is the first study to evaluate the influence of combined socio-economic and climate-change impacts on E.coli concentrations in the Kabul River Basin. The developed SWAT model and scenario analysis can be used for other contaminants, such as nutrients, pesticides and heavy metals. Our study can be a first step to improve water quality of the Kabul River Basin by providing tools for water managers and health specialists to improve the water quality and reduce the risks related to the use of contaminated water resources. This study will be useful not only in this region, but also for other regions of the world with similar microbial water contamination issues.

Assessing the impact of socio-economic development and climate change on faecal indicator bacteria in the Betna River, Bangladesh
Islam, Majedul - \ 2017
University. Promotor(en): Rik Leemans, co-promotor(en): Nynke Hofstra. - Wageningen : Wageningen University - ISBN 9789463436304 - 137
climatic change - environmental impact - water quality - rivers - contamination - bacteria - coliform bacteria - faecal coliforms - bangladesh - south asia - klimaatverandering - milieueffect - waterkwaliteit - rivieren - besmetting - bacteriën - coliformbacteriën - fecale coliformen - zuid-azië

Consumption of water that is contaminated with pathogens still causes high numbers of death and disease. Understanding the factors that influence the dynamic distribution of waterborne pathogens is important, as this will help understanding improvements and possible solutions. Such understanding is particularly important in a developing country like Bangladesh, where large proportions of the population often have little or no access to clean water. Despite the high relevance for public health, few studies currently exists on the fate and transport of pathogens and the so-called Faecal Indicator Bacteria (FIB, e.g. E. coli, enterococci) in (sub)tropical systems. FIB are susceptible to shifts in water flow and quality. The predicted increases in rainfall and floods due to climate change will exacerbate the faecal contamination scenarios. This could be further compounded by the rapid change in socio-economic conditions (population growth, urbanization, sanitation and agricultural management) in the developing countries. Therefore, to reduce future health risks, understanding the influence of changes in socio-economic conditions and climate on microbial dynamics is important.

Very few studies have quantified the relationship between the waterborne pathogens/FIB concentrations and climate and socio-economic changes. In this study a process-based model was developed and a scenario analysis was performed based on the new combined climate and socio-economic changes scenarios, to assess the present and future river hydrodynamics, FIB sources, die-off processes and concentrations. We used FIB, because measuring FIB are cheaper than pathogens. FIB are usually not pathogenic but their presence indicates the likely presence of waterborne pathogens. These pathogens are expected to respond to climate change in a comparable way to FIB. The present study is based on the Betna River basin in southwestern Bangladesh, where faecal contamination is not monitored and very little knowledge exists on the distribution of contaminants.

First of all, FIB concentrations of the river water were measured to identify the river’s faecal contamination levels that can be used to validate the water-quality model. In the study area, wastewater is not treated and this untreated wastewater is discharged directly into the river. This is evident from the measured FIB data. In 88% of the E. coli and all enterococci samples, the USEPA bathing water quality standards were violated (Chapter 2). Such violation indicates potential health risks associated with the use of the river water for domestic, bathing and irrigation purposes. The correlation between environmental variables (water temperature, precipitation and salinity) and FIB concentrations was also determined. A positive correlation was found with water temperature and precipitation, and a negative correlation with salinity. The positive correlation with temperature is due to the co-occurrence of high summer temperature with abundant monsoon rainfall. The positive correlation with precipitation can be explained by the increased runoff from agricultural lands and urban areas. This runoff contains many bacteria. In the study area, during the rainy season (July to September) precipitation increases and as a result water salinity decreases. The observed negative correlation with salinity is more likely due to the typical weather patterns during the rainy season when low salinity coincides with increased precipitation and high temperature, than to salinity dependent die-off of bacteria. A regression model was applied that explained almost half of E. coli and enterococci variability in river water. This, however, only considers water temperature and precipitation (Chapter 2).

Then, the present and future hydrodynamics of the river were simulated using a two dimensional hydrodynamic model (MIKE 21 FM). Although the main goal of this thesis is to assess the river’s present and future FIB concentrations, the reasons for this hydrodynamic modelling are twofold. Firstly, outputs of the hydrodynamic model are used as input into the water-quality model (Chapter 4). Secondly, hydrodynamics (i.e. water level and discharge) are simulated because increased water level and discharge together with sea level rise stimulate floods in the river basin. These floods are related to outbreaks of waterborne diseases. The modelled results corresponded very well with the measured water levels and discharges. The model was applied to simulate baseline and future water levels and discharge for Representative Concentration Pathway RCP4.5 and RCP8.5 scenarios using bias-corrected downscaled data from two climate models (IPSL-CM5A and MPI-ESM). The model results showed an expected increase in water level up to 16% by the 2040s and 23% by the 2090s (Chapter 3). The monsoon daily maximum discharge was expected to increase up to 13% by the 2040s and 21% by the 2090s. These model results also showed that the duration of the water level above the danger level and extreme discharge periods can increase by half a month by the 2040s and over a month by the 2090s. The coincidence of the water danger level with extreme discharge may cause disastrous floods in the study area.

Next, the hydrodynamic model was coupled with a water-quality module (ECOLab). The fate and transport of FIB was simulated, the influence of different processes tested and the contribution from different sources to the total contamination quantified (Chapter 4). The model outputs corresponded very well with the measured FIB data. The present river microbial water quality based on measured and simulated results indicated, once again, noncompliance with bathing water standards. Primary and secondary levels of wastewater treatment were not sufficient to reach the standards most of the time, and discharges from sewer drains and incoming concentrations from the upstream boundary were found to be a major cause of water contamination. Tide, wind and diffuse sources (urban and agricultural runoff) contributed little. The high FIB inputs from the upstream open boundary come from untreated point source discharges from upstream urban areas and accumulation of diffuse contaminants from the large upstream areas. Therefore, this study underlines the need for establishment of wastewater treatment plants both in the studied basin and upstream urban areas. This study provides insight into bacterial fate and transport mechanisms, contribution of different sources to the faecal contamination and applicability of wastewater treatment in a river of a subtropical developing country where this type of study is lacking. Uncertainties are related to the lack of high temporal resolution measured FIB data and the lack of available data for contaminant loads from septic tank leakages, open defecation and sediment resuspension. However, the model well captured the measured FIB variability, suggesting that it can be applied for microbial water quality assessments in other watersheds of the world with similar characteristics.

The developed model could be an ideal tool to forecast future impacts of climate and socioeconomic changes on FIB fate, transport and dynamics. Finally, future FIB concentrations were simulated using the coupled hydrodynamic and microbial model (MIKE 21 FM-ECOLab) and scenario analysis (Chapter 5). Scenarios have been developed building on the most recent Shared Socio-economic Pathways (SSPs) and Representative Concentration Pathways (RCPs) scenarios from the Intergovernmental Panel on Climate Change (IPCC). We developed a baseline scenario (October 2014–September 2015) reflecting the current conditions and two future scenarios, S1 (sustainability scenario) and S2 (uncontrolled scenario) mimicking different future developments of socio-economic (population, urbanization, sanitation, wastewater treatment development, land use) and climate-change factors (temperature, precipitation and sea-level rise). In S1 RCP4.5 was combined with socio-economic scenarios SSP1, and for S2 RCP8.5 was combined with SSP3 (S2). Assumptions on sanitation, waste water treatment and agricultural management in line with the storylines were made to quantify future changes in FIB concentrations and consequent health risk. Different future scenarios were found to have substantial impact on FIB concentrations in the river. By the 2090s, FIB concentrations are expected to decrease by 98% or increase by 75% for the sustainability scenario and uncontrolled scenario respectively. An uncontrolled future resulted in a deterioration of microbial water quality due to socio-economic developments, such as higher population growth, land-use change and increased sewage discharges and changes in rainfall patterns. Microbial water quality strongly improved under a sustainable climate and improved sewage treatment. FIB concentrations were much more sensitive to changes in socio-economic factors than to changes in climatic factors. This underlines the importance of socio-economic factors in assessing and improving microbial water quality.

The results show the importance of improvements in sanitation and wastewater treatment in the Bangladeshi Betna River basin to ensure that future FIB concentrations in the river comply with the US-EPA bathing water quality standards. Major investments to construct wastewater treatment plants are necessary to compensate for the population growth and increased the volume of wastewater treatment. Although the current level of contamination is already too high, without wastewater treatment the water quality will further deteriorate.

The thesis assesses the present and future FIB dynamics in the Betna River through sampling, statistical and process-based modelling, and scenario analysis. The results contribute to increase the knowledge base on the dynamic distributions of the FIB in surface water in a developing country and in a subtropical system, where this type of study is lacking. It also reduces the knowledge gaps regarding future flooding scenarios at the local scale. While some earlier studies focused on only assessing climate-change impacts on microbial water quality, this study for the first time assessed the influence of combined climate and socio-economic scenarios (using scenarios based on the new SSP-RCP scenario matrix) on river FIB concentrations. This combined modelling and scenario approach enables the assessment of faecal contamination sources and dynamics at present and in the future. The developed model and scenario analysis approach provides a basis for the water managers to reduce the widespread faecal contamination and the risks of waterborne disease outbreaks, which are still a leading cause of deaths in developing countries.

Feeds, water quality, gut morphology and digestion in Nile tilapia (Oreochromis niloticus)
Trần Ngọc Thiên Kim, Kim - \ 2017
University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama; Arjen Roem. - Wageningen : Wageningen University - ISBN 9789463431484 - 127
tilapia - oreochromis niloticus - feeds - fish feeding - water quality - digestion - digestibility - intestines - morphology - fish culture - aquaculture - voer - visvoeding - waterkwaliteit - spijsvertering - verteerbaarheid - darmen - morfologie - visteelt - aquacultuur

Diet composition, ingredient and nutrients, are important to consider for maintaining intestinal functions. Studies on both positive (using feed additives) and negative effects (using high inclusion of plant ingredients) of fish feeds are numerous, however, between studies results are often highly variable, both in type of response and in significance. The central hypothesis of this study was that adverse environmental conditions may aggravate negative effects of plant ingredients on the intestinal functions to the extent that mild effects become severe and perceptible. To do so, dietary factors and environmental conditions were evaluated and the interaction between diet composition and environmental conditions were studied in Nile tilapia.

In Chapter 2, six common raw materials including hydrolysed feather meal (HFM), soybean meal (SBM), rice bran (RB), rapeseed meal (RM), sunflower meal (SFM) and dried distiller grains with solubles (DDGS) were chosen to determine the effect of nutrient digestibility, nitrogen/energy balance and changes in intestinal morphology. The study demonstrated that feed ingredients do have an impact on the alteration in intestinal parameters, but also on the nutrient digestibility and the nitrogen/energy balance. Although being well digested, soybean meal caused the most obvious alteration in the intestinal morphology. These alterations were not related to the nutrient digestibility nor to nitrogen/energy balance parameters. Soybean meal, causing the most alterations in the intestinal morphology, was further used in all subsequent chapters of this thesis.

Chapter 3 and 4 described the interaction between diet composition and environmental conditions on the intestinal functions. This was studied with two different environmental conditions, dissolved oxygen (Chapter 3) and salinity (Chapter 4). These two chapters evaluated whether suboptimal environmental conditions (low dissolved oxygen or elevated salinity in water) may interact with a soybean meal based diet in nutrient digestion and intestinal morphology of tilapia. The study demonstrated that environmental stressors can aggravate/reveal the negative intestinal morphology changes induced by a soybean meal based diet. However, these effects of adverse environmental conditions on the intestinal functions were not homogenously dispersed over the whole intestinal length. The effect of salinity on the intestinal morphology occurred predominantly in the distal intestine, whereas the effect of low oxygen concentration was more visible at the proximal intestine. Alterations in the intestinal morphology, as found in this study, have wider effects on the performance of the affected fish. In Chapter 3, the protein digestibility decreased under hypoxic conditions at week 8, which parallels with the time related alteration in intestinal morphology. Chapter 4 showed that when fish were raised at 15 ‰ salinity, nutrient digestibility increased; however, this positive effect decreased when the intestinal morphology changed. The study also found that the combined effect of a soybean meal based diet and hypoxia was stronger compared to the combination with elevated salinity. Therefore, the combination with hypoxia was further used in the next study of this thesis.

In Chapter 5, the combination of hypoxic condition and a soybean meal based diet was chosen to test the hypothesis that only under stressful conditions, the effects of feed additives can be noticed. The impact of two dietary organic acids, formic acid and butyric acid, on nutrient digestibility and intestinal morphology was determined under optimal (normoxia) and suboptimal conditions (hypoxia). The results showed that although organic acids did not significantly improve growth performance and nutrient digestibility under normoxic condition, they did so under hypoxic conditions. Fish fed organic acid supplemented diets all showed improvements in the morphology of intestine under normoxic conditions, and these effects were more enhanced under hypoxic conditions. This indicates that environmental conditions can alter the effect of organic acid on nutrient digestibility and intestinal morphology in tilapia.

Finally, Chapter 6 provided a synthesis of the main findings, and a reflection on the methodologies used in Chapters 2-5 as well as a discussion on the relevance of this study to aquaculture. It is concluded that although being well digested, soybean meal caused the most obvious alteration in intestinal morphology. The adverse environmental conditions aggravated negative effects of soybean meal based diets on the intestinal functions to the extent that mild effects become severe and visible. The negative effect on intestinal morphology of soybean meal in the diet is enhanced at low oxygen level and at elevated salinity. The effect of salinity on the intestinal morphology occurs predominantly in the distal intestine, whereas the effect of low oxygen concentration is more visible at the proximal intestine. The thesis indicated that the impact of organic acids on intestinal functions is dependent on environmental conditions, being more pronounced under challenging conditions (e.g. hypoxia). Therefore, studies on both positive (using feed additives) and negative effects (using high inclusion of plant ingredients) of dietary factors should be done under suboptimal conditions.

Eco-engineering for clarity : clearing blue-green ponds and lakes in an urbanized area
Waajen, Guido W.A.M. - \ 2017
University. Promotor(en): Marten Scheffer, co-promotor(en): Miguel Lurling. - Wageningen : Wageningen University - ISBN 9789463431095 - 306
ponds - lakes - ecological engineering - urban areas - cyanobacteria - eutrophication - water quality - water management - plassen - meren - natuurtechniek - stedelijke gebieden - cyanobacteriën - eutrofiëring - waterkwaliteit - waterbeheer

Small lakes and ponds are common features in urban areas and they contribute to the quality of citizens’ life. A poor water quality, however, can easily give rise to nuisance. A major cause for a poor water quality is a high concentration of plant-nourishing nutrients, eutrophication. In (semi-)standing waters, eutrophication often results in a high biomass of blue-green algae (cyanobacteria), turbid water and the disappearance of submerged aquatic plants. The cyanobacterial blooms can be accompanied with fish kills due to anoxia, the development of unpleasant surface scums and malodors. As cyanobacteria can produce potent toxins, they impose a serious risk for citizens’ health, pets and wildlife. The cyanobacterial blooms hamper the anthropogenic use of the water and can have negative economic impacts. Water managers experience that the reduction of cyanobacterial nuisance is arduous. As long-term positive effects of management interventions are not often achieved, there is need for effective approaches.

The objective of this study was to investigate the efficacy of promising methods to reduce cyanobacterial nuisance in city waters, targeting the clear water state and promoting the growth of aquatic plants. Various methods were tested, in the laboratory, in small and large compartments and were eventually applied in whole ponds and lakes. It is widely accepted that the reduction of nutrient inputs is essential for long-term positive effects. This study focused on the reduction of the input and the availability of the key-nutrient phosphorus. It was shown that cyanobacterial nuisance was wide spread in urban ponds and lakes in the Dutch province of North Brabant. The phosphorus inputs of four urban lakes in this province were addressed. The study lakes differed greatly in the phosphorus sources and loads, depending on site-specific characteristics. These differences affected the selection of measures. It was shown that in-lake measures were effective in realizing the long-term abatement of the cyanobacterial nuisance, provided the external phosphorus input was limited. If the external phosphorus input could not be limited sufficiently, in-lake measures did not result in the long-term reduction of cyanobacterial nuisance.

To reduce the bioavailable phosphorus stock in the lake with in-lake measures, sediment capping with a phosphorus-binding agent (lanthanum-modified bentonite, LMB) can be effective and cheaper than sediment removal by dredging. The additional use of a flocculant may have added value and suppressed cyanobacterial blooms quickly and effectively. Aquatic plants and macroinvertebrates responded positively to the achieved improvement of the water quality. Accumulation of lanthanum was shown in aquatic plants and fish, following LMB exposure. No toxic effects of lanthanum from LMB were observed. Depending on site-specific characteristics, dredging or LMB did not suffice to limit the available phosphorus stock in the lake. For this situation, the additional capping of the sediment with sand was tested and subsequently applied in a lake. Management of the fish biomass and lake reconstruction can support rehabilitation. The results of this study underpin the importance of a site-specific diagnosis (water system analysis). The diagnosis clarifies the underlying causes of cyanobacterial nuisances and is essential for a site-specific tailored set of measures. This study showed that a site-specific set of measures reduced cyanobacterial nuisance effectively for a long term.

As eutrophication control is not always feasible or might be effective only in the long run, curative measures are needed for symptom relief. Several curative end-of-pipe measures that are often suggested were evaluated: effective microorganisms (EM®), golden algae, plant extracts, ultrasound and artificial mixing of non-stratifying waters. No strong support for the efficacy of these measures could be shown. Next to the above mentioned application of flocculant, the use of freshwater quagga mussels is promising. The efficacy of the mussels was experimentally tested and it was shown that the introduction of mussels in a hypertrophic urban pond reduced the phytoplankton biomass, including cyanobacteria, and induced a clear water state. The quagga mussel is an invasive alien species and new introductions should be considered carefully.

Based on the results from this study, the thesis provides a road map for water managers for the reduction of cyanobacterial nuisances in urban ponds and lakes.

Effecten van het mestbeleid op landbouw en milieu : Beantwoording van de ec-postvragen in het kader van de evaluatie van de meststoffenwet
Velthof, G.L. ; Koeijer, T. ; Schröder, J.J. ; Timmerman, M. ; Hooijboer, A. ; Rozemeijer, J. ; Bruggen, C. van; Groenendijk, P. - \ 2017
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2782) - 139
kunstmeststoffen - mest - landbouw - mestbeleid - oppervlaktewater - waterkwaliteit - fertilizers - manures - agriculture - manure policy - surface water - water quality
Ex-ante-evaluatie van de mestmarkt en milieukwaliteit : evaluatie van de meststoffenwet 2016
Schoumans, O.F. ; Blokland, P.W. ; Cleij, P. ; Groenendijk, P. ; Koeijer, T.J. de; Luesink, H.H. ; Renaud, L.V. ; Roovaart, J. van den - \ 2017
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2785) - 93
kunstmeststoffen - wetgeving - mest - mestbeleid - nitraten - waterkwaliteit - oppervlaktewaterkwaliteit - fosfaten - uitspoelen - bemesting - fertilizers - legislation - manures - manure policy - nitrates - water quality - surface water quality - phosphates - leaching - fertilizer application
Voor de ex-ante-evaluatie van de meststoffenwet in 2016 is een analyse uitgevoerd van de gevolgen van drie mestbeleidscenario's voor de meststromen in de landbouw en van de milieukwaliteit.
Fate of nano- and microplastic in freshwater systems: A modeling study
Besseling, Ellen ; Quik, Joris T.K. ; Sun, Muzhi ; Koelmans, Bart - \ 2017
Environmental Pollution 220 (2017)Part A. - ISSN 0269-7491 - p. 540 - 548.
microplastics - particles - water pollution - water quality - sedimentation - fresh water - hydrodynamics - deeltjes - waterverontreiniging - waterkwaliteit - sedimentatie - zoet water - hydrodynamica
Riverine transport to the marine environment is an important pathway for microplastic. However, information on fate and transport of nano- and microplastic in freshwater systems is lacking. Here we present scenario studies on the fate and transport of nano-to millimetre sized spherical particles like microbeads (100 nm–10 mm) with a state of the art spatiotemporally resolved hydrological model. The model accounts for advective transport, homo- and heteroaggregation, sedimentation-resuspension, polymer degradation, presence of biofilm and burial. Literature data were used to parameterize the model and additionally the attachment efficiency for heteroaggregation was determined experimentally. The attachment efficiency ranged from 0.004 to 0.2 for 70 nm and 1050 nm polystyrene particles aggregating with kaolin or bentonite clays in natural freshwater. Modeled effects of polymer density (1–1.5 kg/L) and biofilm formation were not large, due to the fact that variations in polymer density are largely overwhelmed by excess mass of suspended solids that form heteroaggregates with microplastic. Particle size had a dramatic effect on the modeled fate and retention of microplastic and on the positioning of the accumulation hot spots in the sediment along the river. Remarkably, retention was lowest (18–25%) for intermediate sized particles of about 5 μm, which implies that the smaller submicron particles as well as larger micro- and millimetre sized plastic are preferentially retained. Our results suggest that river hydrodynamics affect microplastic size distributions with profound implications for emissions to marine systems.
Financiële prikkels in de landbouw voor verbetering van de waterkwaliteit
Bergevoet, Ron ; Bondt, Nico ; Lauwere, Carolien de; Buurma, Jan ; Linderhof, Vincent ; Rijk, Piet - \ 2016
Wageningen : LEI Wageningen UR (Rapport / LEI Wageningen UR 2016-033) - ISBN 9789462577794 - 89
waterkwaliteit - waterverontreiniging - landbouw - financiële ondersteuning - emissie - nederland - water quality - water pollution - agriculture - financial support - emission - netherlands
While many instruments have already been implemented in various chains in order to limit the emission of pollutants into water, only a fraction of the existing instruments are economic in nature, and very few are geared towards the ‘polluter pays’ principle (as applied in this study). Despite this, agriculture and horticulture in general, and certain sectors in particular, incur expenses in their limiting of noxious substances. There is nevertheless potential to utilize new instruments in order to give further effect to the ‘polluter pays’ principle. These instruments could be most effectively implemented on a company level and/or during the removal of pollutants. New instruments must not be introduced in isolation; instead, an optimum mix must be created in conjunction with other instruments, both existing and new. Further research ought to shed light on the compatibility of proposed instruments within existing policy frameworks as well as in which areas there is a need for entirely new instruments to be developed.
Making eco logic and models work : an integrative approach to lake ecosystem modelling
Kuiper, Jan Jurjen - \ 2016
University. Promotor(en): W.M. Mooij, co-promotor(en): J.H. Janse; Jeroen de Klein. - Wageningen : Wageningen University - ISBN 9789462579446 - 192
ecology - models - ecosystems - modeling - aquatic ecology - water management - water quality - databases - ecologie - modellen - ecosystemen - modelleren - aquatische ecologie - waterbeheer - waterkwaliteit - databanken

Dynamical ecosystem models are important tools that can help ecologists understand complex systems, and turn understanding into predictions of how these systems respond to external changes. This thesis revolves around PCLake, an integrated ecosystem model of shallow lakes that is used by both scientists and water quality managers to understand and predict eutrophication effects in shallow lake ecosystems. Shallow lakes provide some of the clearest examples of alternative stable states in natural systems. PCLake can be used to calculate the critical nutrient loading, that is, the nutrient loading where an abrupt regime shift occurs from a clear aquatic plant dominated state to a turbid phytoplankton dominated state, or vice versa. Four different aspects of modelling with PCLake are addressed in this thesis: (1) making the model better accessible for the modelling community, (2) improving the model, (3) developing scientific theory, and (4) exploring new applications for water quality management.

Following a general introduction to the thesis in chapter 1, the Database Approach To Modelling (DATM) is introduced in chapter 2. DATM is invented to make dynamic models more accessible. The idea of DATM is that the mathematical equations of a model are stored in a database independently of program language and software specific information. From the database, the information can be automatically translated, augmented and compiled into working model code of various different modelling frameworks (software programs).

In chapter 3 the weak link between ecosystem models and real ecosystems is discussed in relation to model calibration and improvement. In a previous stage PCLake has been calibrated using data of more than 40 lakes to obtain a best overall fit, which has greatly increased the scope of the model by making it suitable for more generalized studies on temperate shallow lakes. However, because of this calibration, adding missing functional components to the model at a later stage does not automatically increase the validity of the model, as it may bring the model ‘out of balance’. This is exemplified by adding filter feeding zoobenthos to PCLake, which were previously ignored.

In chapter 4, the relation between food-web theory and alternative stable states theory is scrutinized. Both theoretical paradigms are highly influential in modern ecology as they help scientists understand how stability emerges in complex natural ecosystems. Unfortunately, they developed independently and it is largely unclear how the resilience of a food web relates to the stability of the complete ecosystem. For this study PCLake was used as a virtual reality from which ‘empirical’ information is sampled to parameterize a food web model, following traditional food web methods. This allowed calculating the stability of the food web along a gradient of environmental change, knowing that the complete ecosystem shows a regime shift once the critical nutrient loading is exceeded.

In chapter 5 the question is asked to what extent models of a different form can be used to describe the same natural phenomenon, and hence, how these models can be used for a better understanding of such natural phenomena. Using three classical extensions of the famous Lotka-Volterra equations, which unlike PCLake can be fully mathematically understood, we analyze the consequence of changing a system with a sophisticated functional response term (e.g. Holling type II or III) into a system with a simpler functional response term while maintaining equilibrium densities and material fluxes. These results give new insight into when empirical data can be linked to mathematical models to estimate the stability properties of real ecosystems.

Although PCLake is predominantly applied in the context of ecosystem restoration of turbid phytoplankton dominated lakes, chapter 6 focusses on the clear water state after the reestablishment of aquatic plant dominance as occured. Dense stands of aquatic plants easily cause nuisance, and hence the removal of aquatic plants is an emerging management issue. Yet, because aquatic plants play an important role in stabilizing the clear water state, the removal of plant biomass can potentially trigger a critical transition back to the turbid water state. Currently there is only limited empirical and theoretical understanding of how harvesting of aquatic plants affects ecosystem functioning, which frustrates effective and efficient ecosystem management. With PCLake the impact of harvesting is evaluated, in terms of reducing nuisance and ecosystem stability, for a wide range of external nutrient loadings, mowing intensities and timings. Additionally, the model is used to estimate how much phosphorus is removed from the system during harvesting.

In chapter 7 I discuss the added value of taking an integrative approach to modelling, and discuss the integrated nature of the studies presented in this thesis. It’s also important to note that these studies were part of a larger research project with the overall aim of increasing the usefulness and the validity of PCLake and its twin model PCDitch, and to enhance the confidence in the models among water quality managers. A synopsis of the overarching collaborative research project on PCLake and PCDitch is presented in chapter 8.

Achtergrond : boeren! : valt daar mee te praten dan?
Aarts, Frans - \ 2016
water management - water quality - farmers - agricultural sector - polder boards - drinking water
Ze hebben veel gezamenlijke belangen, maar in de praktijk verloopt de samenwerking tussen agrariërs en de watersector niet altijd soepel. Boeren zien waterschappen als bolwerken van bureaucratie en waterschappen vinden boeren maar een stelletje zeuren. Twee werelden… and never the twain shall meet? Nee, zo erg is het niet, want soms gaat het ook wél goed.
Koeien & Kansen werkt aan beter waterbeheer
Verloop, J. ; Haan, M.H.A. de; Hoving, I.E. ; Noij, I.G.A.M. - \ 2016
V-focus 13 (2016)4. - ISSN 1574-1575 - p. 34 - 36.
melkveehouderij - waterbeheer - agrarische bedrijfsvoering - waterkwaliteit - waterschappen - dairy farming - water management - farm management - water quality - polder boards
Waterbeheer heeft een grotere rol gekregen in het project Koeien & Kansen. In samenwerking met waterschappen werkt Koeien & Kansen aan een instrument waarmee de melkveehouder het waterbeheer op zijn bedrijf in beeld brengt en op een hoger plan kan tillen: de BedrijfsWaterWijzer. Dat is nodig omdat nog te veel kansen worden gemist in het waterbeheer op en rond het melkveebedrijf.
'Met goede monitoring verdien je je geld dubbel en dwars terug'
Mooij, Wolf ; Verdonschot, Piet - \ 2016
water quality - monitoring - water management - aquatic ecology - water systems

Drie dagen congresseren over waterkwaliteitsmonitoring. Je moet wel lef hebben, vond Inge Diepman, dagvoorzitter van de eerste dag van het driedaagse STOWA-congres ‘Goede monitoring, effectief waterkwaliteitsbeheer’, dat plaatsvond op 19, 20 en 21 april 2016 in Arnhem. Want valt er over monitoring wel zoveel te zeggen, en hoe belangrijk is het eigenlijk? Heel belangrijk, zo bleek tijdens het congres. Daarom staan we er in deze editie van de STOWA ter Info nog een keer uitgebreid bij stil.

Effect van klimaatverandering en vergrijzing op waterkwaliteit en drinkwaterfunctie van Maas en Rijn
Sjerps, Rosa M.A. ; Laak, T.L. ter; Zwolsman, G.J. - \ 2016
H2O online (2016)augustus.
climatic change - drinking water - water quality - surface water - pesticides - radiography - drug residues - water pollution - river meuse - river rhine - prognosis - klimaatverandering - drinkwater - waterkwaliteit - oppervlaktewater - pesticiden - radiografie - geneesmiddelenresiduen - waterverontreiniging - maas - rijn - prognose
Door de vergrijzing zal de emissie van geneesmiddelen en röntgencontrastmiddelen naar het oppervlaktewater toenemen. De effecten van toenemende emissies op de waterkwaliteit worden versterkt bij lage rivierafvoeren, die naar verwachting steeds vaker en langduriger zullen optreden in een veranderend klimaat. In deze studie zijn prognoses gemaakt van de toekomstige concentraties van een aantal relevante organische microverontreinigingen in de Rijn en Maas in het jaar 2050. De voorspelde concentraties van diverse geneesmiddelen en röntgencontrastmiddelen in de Rijn en de Maas overschrijden de ERM-streefwaarden voor oppervlaktewater als bron van drinkwater. Sporen van enkele organische microverontreinigingen kunnen doordringen in het drinkwater.
Invloed van beekbegeleidende bomen op de ecologische kwaliteit van Noord-Brabantse beken
Verdonschot, R.C.M. ; Brugmans, Bart ; Scheepens, Mark ; Coenen, Daniël ; Verdonschot, P.F.M. - \ 2016
H2O online (2016)28 juli.
aquatische ecologie - waterlopen - bomen - noord-brabant - monitoring - beschaduwen - gegevensanalyse - waterschappen - vegetatie - waterplanten - waterkwaliteit - aquatic ecology - streams - trees - shading - data analysis - polder boards - vegetation - aquatic plants - water quality
Monitoringsdata van Brabantse beken laat zien dat bomen belangrijk zijn voor het halen van ecologische doelen. Echter, voor maximale effectiviteit met betrekking tot vegetatieontwikkeling en koeling van het beekwater voldoet alleen de zwaarste beschaduwingsklasse (>70%) en moet gestreefd worden naar lange beschaduwde trajecten. Macrofauna profiteert vooral via de door bomen gegenereerde substraatdifferentiatie. Het toepassen van beschaduwing brengt voor de waterschappen wel grote uitdagingen met zich mee. Verder blijkt uit de data-analyse dat jaarrond voldoende stroming een vereiste is voor de ecologische doelrealisatie in de trajecten.
Uitloging en effecten van metalen uit staalslakken beoordeeld in mesocosms
Foekema, E.M. ; Heuvel-Greve, M.J. van den; Sonneveld, C. ; Hoornsman, G. ; Blanco Garcia, A. - \ 2016
Den Helder : IMARES Wageningen UR (Rapport / IMARES C063/16) - 102 p.
mesocosmossen - oosterschelde - zware metalen - zuurgraad - erosiebestrijding - waterkwaliteit - mesocosms - eastern scheldt - heavy metals - acidity - erosion control - water quality
Het doel van dit project was vast te stellen in welke mate zware metalen uit in zee gebrachte staalslakken bij een voor de Oosterschelde realistische en een worst-case waterverversingssnelheid: - uitlogen naar de waterkolom; - opgenomen worden door schelpdieren (mossel), wieren (Zee-eik), zakpijpen en sponzen; - negatieve effecten veroorzaken bij bovengenoemde organismen en op het mesocosm ecosysteem. De resultaten van de staalslakken zijn vergeleken met breuksteen, het materiaal dat traditioneel voor dijkverzwaring gebruikt wordt en maasgrind als referentiemateriaal met naar verwachting weinig of geen uitloging.
Landbouwpraktijk en waterkwaliteit op landbouwbedrijven aangemeld voor derogatie in 2014
Lukács, S. ; Koeijer, T.J. de; Prins, H. ; Vrijhoef, A. ; Boumans, L.J.M. ; Daatselaar, C.H.G. - \ 2016
Bilthoven : Rijksinstituut voor Volksgezondheid en Milieu (RIVM rapport 2016-0052) - 118 p.
dierlijke meststoffen - graslanden - nitraten - grondwaterkwaliteit - monitoring - eu regelingen - mest - waterkwaliteit - landbouwbedrijven - animal manures - grasslands - nitrates - groundwater quality - eu regulations - manures - water quality - farms
De Europese Nitraatrichtlijn verplicht lidstaten om het gebruik van dierlijke mest te beperken tot 170 kg stikstof per hectare. Landbouwbedrijven in Nederland met ten minste 70 procent grasland mochten onder bepaalde voorwaarden van deze norm afwijken en in 2013 250 kilogram per hectare gebruiken (derogatie). Nederland is verplicht om op 300 bedrijven die derogatie inzetten de bedrijfsvoering en waterkwaliteit te meten en deze resultaten jaarlijks aan de EU te rapporteren. LEI Wageningen UR en het RIVM stellen jaarlijks deze rapportage op. Dit rapport beschrijft de situatie in 2013 en de trends voor de periode tussen 2006 en 2014. Uit de resultaten blijkt dat de nitraatconcentratie in het grondwater in deze periode, afhankelijk van de regio, is gedaald of gelijk is gebleven.
The neurotoxin BMAA in aquatic systems : analysis, occurrence and effects
Faassen, E.J. - \ 2016
University. Promotor(en): Marten Scheffer, co-promotor(en): Miguel Lurling. - Wageningen : Wageningen University - ISBN 9789462577855 - 194 p.
cum laude - neurotoxins - aquatic environment - urban areas - effects - environmental impact - daphnia magna - elisa - water quality - analytical methods - aquatic ecology - neurotoxinen - aquatisch milieu - stedelijke gebieden - effecten - milieueffect - waterkwaliteit - analytische methoden - aquatische ecologie

Eutrophication is a major water quality issue and in many aquatic systems, it leads to the proliferation of toxic phytoplankton species. The neurotoxin β-N-methylamino-L-alanine (BMAA) is one of the compounds that can be present in phytoplankton. BMAA has been suggested to play a role in the neurodegenerative diseases Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis, although this hypothesis still needs to be confirmed. It is expected that the main human exposure pathways to BMAA are through direct contact with BMAA containing phytoplankton and through ingestion of BMAA contaminated food, such as fish and shellfish. However, reports on the occurrence of BMAA in aquatic systems have been conflicting and the cause of these reported differences was heavily debated. The use of different analytical methods seems to play a crucial role in the observed discrepancies, but initially, there was little consensus on which method produced most reliable results. The objectives of the work presented in this thesis therefore were to find out what has caused the differences in published results on BMAA concentrations, and to identify and produce reliable data on the presence of BMAA in aquatic systems. In addition, I aimed to determine the effect of BMAA exposure on a key species in many freshwater ecosystems, the grazer Daphnia magna.

The performances of different analytical techniques were compared, and LC-MS/MS analysis, either preceded by derivatisation or not, was found to produce most reliable results. LC-FLD and ELISA should not be used for BMAA analysis, as both methods risk misidentifying BMAA or overestimating its concentrations due to their low selectivity. When reviewing literature on the presence of BMAA in aquatic systems, it was found that the observed discrepancies in results could be explained by the use of unselective analytical methods in some studies, and by severe reporting deficiencies in others. When only studies that used appropriate analytical techniques and that correctly reported their work were taken into account, it was shown that BMAA could be present in phytoplankton and higher aquatic organisms, in concentrations of µg/g dry weight or lower. These results are in agreement with our findings of BMAA in cyanobacterial scums from Dutch urban waters. In a 2008 screening, BMAA was found to be present in 9 out of 21 analysed cyanobacterial scums, at concentrations ranging from 4 to 42 µg/g dry weight. When this screening was repeated 8 years later with 52 similar samples, BMAA was detected below the quantification limit in one sample and quantified in another sample at 0.6 µg/g dry weight.

In order to perform the work presented in this thesis, sensitive and selective analytical methods, mostly based on LC-MS/MS analysis without derivatisation, were developed. This resulted in a standard operating procedure for the underivatised LC-MS/MS analysis of BMAA in cyanobacteria. Also, a CYANOCOST initiated workshop was given, in which a group of scientists from 17 independent laboratories evaluated LC-MS/MS based methods in different matrices. A bound BMAA from found in the supernatant was the most abundant fraction in the positive samples that were tested: cycad seed, seafood and exposed D. magna. In addition, it was found that the deuterated internal standard used for quantification was not a good indicator for the release of BMAA from bound forms, resulting in unprecise quantification of total BMAA.

BMAA was found to reduce survival, somatic growth, reproduction and population growth in D. magna. Animals did not adapt to BMAA exposure: exposed animals born from exposed mothers had a lower brood viability and neonate weight than animals exposed to BMAA, but born from unexposed mothers. In addition, D. magna was shown to take up BMAA from the growth medium and to transfer it to its offspring. D. magna therefore might be an important vector for BMAA transfer along the pelagic food chain, but whether BMAA plays a role in preventing zooplankton from controlling cyanobacterial blooms needs further investigation.

Although BMAA research has much progressed between the start of this thesis’ work and its completion, some important questions still require an answer. Most urgently, it should be determined whether BMAA is indeed involved in the neurological diseases mentioned above, and if so, which doses trigger the onset of these diseases. Human exposure pathways should then be more systematically quantified, and it might be prudent to investigate if the occurrence of BMAA is restricted to aquatic systems, or whether sources from terrestrial systems contribute to BMAA exposure as well.

Quantifying potential sources of surface water contamination with Campylobacter jejuni and Campylobacter coli
Mughini-Gras, Lapo ; Penny, Christian ; Ragimbeau, Catherine ; Schets, Franciska M. ; Blaak, Hetty ; Duim, Birgitta ; Wagenaar, Jaap A. ; Boer, Albert de; Cauchie, Henry-Michel ; Mossong, Joel ; Pelt, Wilfrid Van - \ 2016
Water Research 101 (2016). - ISSN 0043-1354 - p. 36 - 45.
campylobacter - surface water - water quality - pollution - water pollution - microbiology - wild birds - poultry - campylobacter jejuni - campylobacter coli - netherlands - luxembourg - oppervlaktewater - waterkwaliteit - verontreiniging - waterverontreiniging - microbiologie - wilde vogels - pluimvee - nederland - luxemburg
Campylobacter is the most common causative agent of human bacterial gastroenteritis and is frequently found in surface water, where it indicates recent contamination with animal faeces, sewage effluent, and agricultural run-off. The contribution of different animal reservoirs to surface water contamination with Campylobacter is largely unknown. In the Netherlands, the massive poultry culling to control the 2003 avian influenza epidemic coincided with a 44–50% reduction in human campylobacteriosis cases in the culling areas, suggesting substantial environment-mediated spread of poultry-borne Campylobacter. We inferred the origin of surface water Campylobacter jejuni and Campylobacter coli strains in Luxembourg and the Netherlands, as defined by multilocus sequence typing, by comparison to strains from poultry, pigs, ruminants, and wild birds, using the asymmetric island model for source attribution. Most Luxembourgish water strains were attributed to wild birds (61.0%), followed by poultry (18.8%), ruminants (15.9%), and pigs (4.3%); whereas the Dutch water strains were mainly attributed to poultry (51.7%), wild birds (37.3%), ruminants (9.8%), and pigs (1.2%). Attributions varied over seasons and surface water types, and geographical variation in the relative contribution of poultry correlated with the magnitude of poultry production at either the national or provincial level, suggesting that environmental dissemination of Campylobacter from poultry farms and slaughterhouses can be substantial in poultry-rich regions.
Ecologische kantelpunten in de Nederlandse grote wateren : Discussie memo over recente inzichten, voorbeelden en onderzoeksvragen
Veraart, J.A. ; Reijers, Valerie ; Lange, H.J. de; Nes, E.H. van; Kosten, S. ; Baptist, M.J. ; Noordhuis, Ruurd ; Platteeuw, M. - \ 2016
- 33 p.
aquatische ecologie - watersystemen - waterbeheer - waterkwaliteit - aquatische ecosystemen - aquatic ecology - water systems - water management - water quality - aquatic ecosystems
Deze memo beschrijft recente inzichten op het terrein van ecologische kantelpunten die zijn opgedaan in onderzoek en bij Rijkswaterstaat. Gegeven de korte projectduur (twee maanden) is er niet gestreefd naar volledigheid, maar zijn er inzichten bijeengebracht die behulpzaam zijn om de discussie aan te zwengelen over wat de kantelpuntentheorie kan betekenen voor het beheer, evaluatie en monitoring van de grote wateren. In het sterk gemodificeerde Nederlandse watersysteem is het moeilijk om vast te stellen of alternatieve evenwichten onder gelijke condities mogelijk zijn en dat kantelpunten hiertussen plaatsvinden. Alternatieve evenwichten en terugkoppelingsmechanismen zijn het best onderbouwd en omschreven in de literatuur voor de Waddenzee en Veluwemeer. In de estuaria zijn er veel indicaties maar ook veel onzekerheden. In het rivierengebied is het de vraag of alternatieve evenwichten kunnen bestaan. Het beter begrijpen van terugkoppelingsmechanismen in de Nederlandse zoete en zoute wateren, en de interacties hiertussen, wordt echter breed onderschreven. Terugkoppelingsmechanismen
zijn met het kantelpuntenconcept goed te onderzoeken voor alle watersystemen en een beter begrip hierover is nuttig voor beleidsevaluaties, het inschatten van het effect van ecologische ingrepen en monitoringsplannen. Het is belangrijk om ook rekening te houden met ‘onbekende’ en niet kwantificeerbare factoren die de veerkracht van een ecosysteem kunnen beïnvloeden. Er is nog niet veel bekend over de invloed van microverontreinigingen, trofische cascades (vissen, vogels), microbiële bodemactiviteit en de rol van hydromorfologische dynamiek in rivieren en estuaria op de ecologische veerkracht van een watersysteem. Het is aan te bevelen om eerst met een aantal casestudies te
verkennen wat de mogelijkheden en datavereisten zijn om met langjarige tijdreeksen (ecologie, waterkwaliteit) indicatoren te bepalen die iets zeggen over verandering in ecologische veerkracht. Voorts doen wij de aanbeveling om het begrip ' Safe operating Space’ beter hanteerbaar te maken voor wateren natuurbeheerders.
'Standaard Water’ voor toetsing zuiveringstechnologie voor de glastuinbouw
Ruijven, Jim van; Blok, C. ; Beerling, E.A.M. ; Os, E.A. van - \ 2016
Wageningen UR - 3 p.
waterzuivering - pesticiden - glastuinbouw - waterverontreiniging - waterkwaliteit - water treatment - pesticides - greenhouse horticulture - water pollution - water quality
Het is noodzakelijk zuiveringstechnieken op een objectieve manier te toetsen op effectiviteit in de verwijdering van gewasbeschermingsmiddelen uit glastuinbouw lozingswater met water dat representatief is voor de glastuinbouw. Hiervoor is het in dit document beschreven ‘Standaard Water’ ontwikkeld. Dit water wordt gebruikt om op een gestandaardiseerde en reproduceerbare manier technologieën te beoordelen en heeft daarom een vastgestelde samenstelling. Het water dient als standaard voor lozingswater uit zowel substraat- als grondgebonden teelten en bevat nutriënten en sporenelementen, organische en minerale vervuiling en gewasbeschermingsmiddelen.
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