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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Cost-effective management of coastal eutrophication : A case study for the yangtze river basin
Strokal, M. ; Kahil, T. ; Wada, Y. ; Albiac, J. ; Bai, Z. ; Ermolieva, T. ; Langan, S. ; Ma, L. ; Oenema, O. ; Wagner, F. ; Zhu, X. ; Kroeze, C. - \ 2020
Resources, Conservation and Recycling 154 (2020). - ISSN 0921-3449
Cost-effective management - Eutrophication - Integrated modelling - Nitrogen and phosphorus - Nutrient management - Waste recycling

Many water resources are threatened with nutrient pollution worldwide. This holds for rivers exporting increasing amounts of nutrients from the intensification of food production systems and further urbanization. This riverine nutrient transport causes coastal eutrophication. This study aims to identify cost-effective management options to simultaneously reach environmental targets for river export of nitrogen and phosphorus by the Yangtze River (China) in 2050. A newly developed modelling approach is used that integrates the Model to Assess River Inputs of Nutrients to seAs (MARINA) with a cost-optimization procedure, and accounts for socio-economic developments, land use and climate changes in a spatially explicit way. The environmental targets for river export of nutrients aim to reduce the gap between baseline and desirable nutrient export. Our baseline is based on MARINA projections for future river export of nutrients, while the desirable nutrient export reflects a low eutrophication potential. Results show the possibilities to close the gap in river export of both nutrients by 80–90% at a cost of 1–3 billion $ per year in 2050. Recycling of animal waste on cropland is an important cost-effective option; reducing synthetic fertilizer inputs provides an opportunity to compensate for the additional costs of the recycling and treatment of manure and wastewater. Our study provides new insights on the combination of cost-effective management options for sub-basins of the Yangtze. This can support the design of cost-effective and sub-basin specific management options for reducing future water pollution.

From sustainable drinking water to tsunami hazards : modelling water science for impact
He, Xiaogang ; Student, Jillian ; Kroeze, Carolien - \ 2019
Journal of integrative Environmental Sciences 16 (2019)1. - ISSN 1943-815X - p. 157 - 161.
Water pollution from food production: lessons for optimistic and optimal solutions
Li, Ang ; Kroeze, Carolien ; Kahil, Taher ; Ma, Lin ; Strokal, Maryna - \ 2019
Current Opinion in Environmental Sustainability 40 (2019). - ISSN 1877-3435 - p. 88 - 94.

Food production is a source of various pollutants in aquatic systems. For example, nutrients are lost from fertilized fields, and pathogens from livestock production. Water pollution may impact society and nature. Large-scale water pollution assessments, however, often focus on single pollutants and not on multiple pollutants simultaneously. This study draws lessons from air pollution control for large-scale water quality assessments, where multi-pollutant approaches are more common. To this end, we present a framework for future water pollution assessments searching for optimistic and optimal solutions. We argue that future studies could shift their focus to better account for societal and economic targets. Participatory approaches can help to ensure the feasibility of future solutions to reduce water pollution from food production.

Increasing nitrogen export to sea: A scenario analysis for the Indus River
Wang, Mengru ; Tang, Ting ; Burek, P. ; Havlík, Petr ; Krisztin, Tamás ; Kroeze, Carolien ; Leclère, D. ; Strokal, Maryna ; Wada, Yoshihide ; Wang, Yaoping ; Langan, S. - \ 2019
Science of the Total Environment 694 (2019). - ISSN 0048-9697
Indus River - Nitrogen sources - Representative concentration pathways - River export of nitrogen (N) - Shared socio-economic pathways - Sub-basins

The Indus River Basin faces severe water quality degradation because of nutrient enrichment from human activities. Excessive nutrients in tributaries are transported to the river mouth, causing coastal eutrophication. This situation may worsen in the future because of population growth, economic development, and climate change. This study aims at a better understanding of the magnitude and sources of current (2010) and future (2050) river export of total dissolved nitrogen (TDN) by the Indus River at the sub-basin scale. To do this, we implemented the MARINA 1.0 model (Model to Assess River Inputs of Nutrients to seAs). The model inputs for human activities (e.g., agriculture, land use) were mainly from the GLOBIOM (Global Biosphere Management Model) and EPIC (Environmental Policy Integrated Model) models. Model inputs for hydrology were from the Community WATer Model (CWATM). For 2050, three scenarios combining Shared Socio-economic Pathways (SSPs 1, 2 and 3) and Representative Concentration Pathways (RCPs 2.6 and 6.0) were selected. A novelty of this study is the sub-basin analysis of future N export by the Indus River for SSPs and RCPs. Result shows that river export of TDN by the Indus River will increase by a factor of 1.6–2 between 2010 and 2050 under the three scenarios. >90% of the dissolved N exported by the Indus River is from midstream sub-basins. Human waste is expected to be the major source, and contributes by 66–70% to river export of TDN in 2050 depending on the scenarios. Another important source is agriculture, which contributes by 21–29% to dissolved inorganic N export in 2050. Thus a combined reduction in both diffuse and point sources in the midstream sub-basins can be effective to reduce coastal water pollution by nutrients at the river mouth of Indus.

How to avoid coastal eutrophication - a back-casting study for the North China Plain
Li, Ang ; Strokal, Maryna ; Bai, Zhaohai ; Kroeze, Carolien ; Ma, Lin - \ 2019
Science of the Total Environment 692 (2019). - ISSN 0048-9697 - p. 676 - 690.
China - Coastal eutrophication - Manure management - MARINA 1.0 model - Nutrients - River pollution

Eutrophication is a serious problem in Chinese seas. We explore possibilities to avoid coastal eutrophication without compromising food production in the North China Plain. We used the Model to Assess River Inputs of Nutrient to seAs (MARINA 1.0) for back-casting and scenario analysis. Avoiding coastal eutrophication by 2050 implies required reductions in river export of total nitrogen (TN) and phosphorus (TP) by 50–90% for the Hai, Huai and Huang rivers. We analyzed the potential to meet these targets in 54 scenarios assuming improvements in manure recycling, fertilizer application, animal feed and wastewater treatment. Results indicate that combining manure recycling while reducing synthetic fertilizer use are effective options to reduce nutrient inputs to seas. Without such options, direct discharge of manure are important sources of water pollution. In the 7–25 scenarios with the low eutrophication potential, 40–100% of the N and P in untreated manure is recycled on land to replace synthetic fertilizers. Our results can support the formulation of effective environmental policies to avoid coastal eutrophication in China.

Multi-scale Modeling of Nutrient Pollution in the Rivers of China
Chen, Xi ; Strokal, Maryna ; Vliet, Michelle T.H. Van; Stuiver, John ; Wang, Mengru ; Bai, Zhaohai ; Ma, Lin ; Kroeze, Carolien - \ 2019
Environmental Science and Technology 53 (2019)16. - ISSN 0013-936X - p. 9614 - 9625.
Chinese surface waters are severely polluted by nutrients. This study addresses three challenges in nutrient modeling for rivers in China: (1) difficulties in transferring modeling results across biophysical and administrative scales, (2) poor representation of the locations of point sources, and (3) limited incorporation of the direct discharge of manure to rivers. The objective of this study is, therefore, to quantify inputs of nitrogen (N) and phosphorus (P) to Chinese rivers from different sources at multiple scales. We developed a novel multi-scale modeling approach including a detailed, state-of-the-art representation of point sources of nutrients in rivers. The model results show that the river pollution and source attributions differ among spatial scales. Point sources accounted for 75% of the total dissolved phosphorus (TDP) inputs to rivers in China in 2012, and diffuse sources accounted for 72% of the total dissolved nitrogen (TDN) inputs. One-third of the sub-basins accounted for more than half of the pollution. Downscaling to the smallest scale (polygons) reveals that 14% and 9% of the area contribute to more than half of the calculated TDN and TDP pollution, respectively. Sources of pollution vary considerably among and within counties. Clearly, multi-scale modeling may help to develop effective policies for water pollution
Impact hotspots of reduced nutrient discharge shift across the globe with population and dietary changes
Wang, Xu ; Daigger, Glen ; Vries, Wim de; Kroeze, Carolien ; Yang, Min ; Ren, Nan Qi ; Liu, Junxin ; Butler, David - \ 2019
Nature Communications 10 (2019)1. - ISSN 2041-1723

Reducing nutrient discharge from wastewater is essential to mitigating aquatic eutrophication; however, energy- and chemicals-intensive nutrient removal processes, accompanied with the emissions of airborne contaminants, can create other, unexpected, environmental consequences. Implementing mitigation strategies requires a complete understanding of the effects of nutrient control practices, given spatial and temporal variations. Here we simulate the environmental impacts of reducing nutrient discharge from domestic wastewater in 173 countries during 1990–2050. We find that improvements in wastewater infrastructure achieve a large-scale decline in nutrient input to surface waters, but this is causing detrimental effects on the atmosphere and the broader environment. Population size and dietary protein intake have the most significant effects over all the impacts arising from reduction of wastewater nutrients. Wastewater-related impact hotspots are also shifting from Asia to Africa, suggesting a need for interventions in such countries, mostly with growing populations, rising dietary intake, rapid urbanisation, and inadequate sanitation.

Seasonality in river export of nitrogen : A modelling approach for the Yangtze River
Chen, Xuanjing ; Strokal, Maryna ; Kroeze, Carolien ; Ma, Lin ; Shen, Zhenyao ; Wu, Jiechen ; Chen, Xinping ; Shi, Xiaojun - \ 2019
Science of the Total Environment 671 (2019). - ISSN 0048-9697 - p. 1282 - 1292.
Diffuse and point sources - MARINA model - Nitrogen - Sub-basins - Water quality - Yangtze River

In China, many estuaries suffer from eutrophication problems such as green tides and hypoxia. This is often a result of human activities on land leading to increased nutrient exports by rivers. River pollution shows seasonal trends that are not well understood. Therefore, the main objective of this study is to improve our understanding of the seasonal variation in river export of dissolved inorganic nitrogen (DIN) by source and at the sub-basin scale. To this end, we modified the existing MARINA model 1.0 (Model to Assess River Input of Nutrient to seAs) to account for seasonality in river export of DIN, and applied it to the Yangtze River. The resulting MARINA model version 1.1 takes a mass-balance approach and accounts for seasonality in human activities (e.g., crop planting and fertilization) and meteorology. The model distinguishes four seasons: winter (December–February), spring (March–May), summer (June–August) and fall (September–November). Our results for Yangtze indicate that N inputs to land and river export of DIN to sea are higher in summer and lower in winter. In spring, summer and fall, diffuse sources from agriculture contribute 43–85% to DIN export. In spring and fall, use of synthetic N fertilizers in cropland is an important source of DIN. In summer, both atmospheric N deposition and synthetic N fertilizers dominate. Animal manure is typically applied on land in spring and fall, contributing then to DIN. In winter, point sources of animal manure are responsible for 34–74% of DIN river export. In general, more DIN is exported to the sea from activities in middlestream and downstream sub-basins. Our results can serve as an example for other large rivers worldwide, and support the formulation of effective strategies to reduce seasonal eutrophication.

Re-evaluating safety risks of multifunctional dikes with a probabilistic risk framework
Marijnissen, Richard ; Kok, Matthijs ; Kroeze, Carolien ; Loon-Steensma, Jantsje Van - \ 2019
Natural Hazards and Earth System Sciences 19 (2019)4. - ISSN 1561-8633 - p. 737 - 756.

It is not uncommon for a flood defence to be combined with other societal uses as a multifunctional flood defence, from housing in urban areas to nature conservation in rural areas. The assessment of the safety of multifunctional flood defences is often done using conservative estimates. This study synthesizes new probabilistic approaches to evaluate the safety of multifunctional flood defences employed in the Netherlands and explores the results of these approaches. In this paper a case representing a typical Dutch river dike combining a flood safety function with a nature and housing function is assessed by its probability of failure for multiple reinforcement strategies considering multiple relevant failure mechanisms. Results show how the conservative estimates of multifunctional flood defences lead to a systematic underestimation of the reliability of these dikes. Furthermore, in a probabilistic assessment uncertainties introduced by multifunctional elements affect the level of safety of the dike proportional to the reliability of the dike itself. Hence, dikes with higher protection levels are more suitable to be combined with potentially harmful uses for safety, whereas dikes with low protection levels can benefit most from uses that contribute to safety.

Modelling global river export of microplastics to the marine environment : Sources and future trends
Wijnen, Jikke van; Ragas, Ad M.J. ; Kroeze, Carolien - \ 2019
Science of the Total Environment 673 (2019). - ISSN 0048-9697 - p. 392 - 401.
Coastal seas - Future scenarios - GREMiS model - Microplastics - Plastic soup - River transport

Microplastics, transported by rivers to oceans, are triggering environmental concern. This study aims to better understand river export of microplastics from land to sea. We developed the Global Riverine Export of Microplastics into Seas (GREMiS) model, a global, spatially explicit model for analysing the annual microplastics export to coastal seas. Our results indicate that riverine microplastics export varies among world regions, with several hotspots, e.g., South East Asia, and, depending on the 2050 scenario, may be doubled (‘Business as usual’) or halved due to improved waste management (‘Environment profits’). Globally, our model simulations indicated fragmentation of macroplastics as the main source of microplastics, but this result heavily depends on the assumed fragmentation rate. Sewerage discharges contributed only 20%, ranging from 1% (Africa) to 60% (OECD countries) and decreasing by 2050 as a result of improved sanitation. We conclude that, combating microplastics in the aquatic environment requires more region-specific analyses.

Scenarios for withdrawal of oil palm plantations from peatlands in Jambi Province, Sumatra, Indonesia
Afriyanti, Dian ; Hein, Lars ; Kroeze, Carolien ; Zuhdi, Mohammad ; Saad, Asmadi - \ 2019
Regional Environmental Change 19 (2019)4. - ISSN 1436-3798 - p. 1201 - 1215.
Carbon emission - Mitigation - Oil palm - Peatlands - Restore - Withdrawal
In Indonesia, peatlands are still being converted into oil palm plantations. The associated fires and peat oxidation result in smoke and large carbon emissions. In the medium term, peatlands should be used for production systems that do not require (or require much less) drainage. In this context, this study aims to explore scenarios for the withdrawal of oil palm plantations from peatlands in Jambi province and the associated carbon emissions in the coming decades. We first analyzed past land-use change trends in Jambi peatlands. Then, we analyzed three scenarios for the future: (1) a baseline scenario, assuming further expansions by smallholders, but not by companies, (2) a scenario assuming withdrawal from peat by companies only, and (3) a scenario assuming withdrawal from peat by companies and smallholders. In both scenarios 1 and 2, it is assumed smallholders keep on expanding oil palm plantations in peatlands up to 2020 but not thereafter. To accommodate economic interests of growers, withdrawal of oil palm plantations is assumed to only take place when the palm trees are 25 years old and their productivity starts declining. Our study shows that there has been a rapid expansion of oil palm plantations in peatlands of Jambi from 30,000 ha in 1987 to 483,000 ha in 2014. In our baseline scenario, involving commitments from companies but not from smallholders, the area of oil palm further increases by 20% between 2014 and 2040; this implies that by 2040, almost all peatlands, including those in the buffer zone of Berbak National Park, will have been converted to plantations. The corresponding greenhouse gas emissions are 53 Mt CO 2 -equivalent per year (from both peat decomposition and fires). In the scenario assuming withdrawal of company plantations from peatlands, the plantation area will be reduced to half that in the baseline scenario in 2040. This would decrease CO 2 -equivalent emissions in 2040 to below 2010 levels (27.9 Mt per year). Our study shows that a substantial decrease in emissions is only possible in scenario 3 with an almost full withdrawal of plantations from peatlands by 2040. This reduces CO 2 -equivalent emissions to the level of 2000 (4.3 Mt per year) and leads to safeguarding the remaining pristine peat swamp forest in Berbak National Park.
Editorial overview : Water quality: A new challenge for global scale model development and application
Hofstra, Nynke ; Kroeze, Carolien ; Flörke, Martina ; Vliet, Michelle T.H. van - \ 2019
Current Opinion in Environmental Sustainability 36 (2019). - ISSN 1877-3435 - p. A1 - A5.
Editorial
Kroeze, Carolien ; Moll, Henri C. ; Student, Jillian - \ 2019
Journal of integrative Environmental Sciences 16 (2019)1. - ISSN 1943-815X - p. i - iii.
Excess nutrient loads to Lake Taihu : Opportunities for nutrient reduction
Wang, Mengru ; Strokal, Maryna ; Burek, Peter ; Kroeze, Carolien ; Ma, Lin ; Janssen, Annette B.G. - \ 2019
Science of the Total Environment 664 (2019). - ISSN 0048-9697 - p. 865 - 873.
Critical nutrient loads - MARINA-Lake - Nutrient sources - PCLake model - River export of nutrients - Sub-basins

Intensive agriculture and rapid urbanization have increased nutrient inputs to Lake Taihu in recent decades. This resulted in eutrophication. We aim to better understand the sources of river export of total dissolved nitrogen (TDN) and phosphorus (TDP) to Lake Taihu in relation to critical nutrient loads. We implemented the MARINA-Lake (Model to Assess River Inputs of Nutrients to seAs) model for Lake Taihu. The MARINA-Lake model quantifies river export of dissolved inorganic and organic N and P to the lake by source from sub-basins. Results from the PCLake model are used to identify to what extent river export of nutrients exceeds critical loads. We calculate that rivers exported 61 kton of TDN and 2 kton of TDP to Lake Taihu in 2012. More than half of these nutrients were from human activities (e.g., agriculture, urbanization) in Sub-basins I (north) and IV (south). Most of the nutrients were in dissolved inorganic forms. Diffuse sources contributed 90% to river export of TDN with a relatively large share of synthetic fertilizers. Point sources contributed 52% to river export of TDP with a relatively large share of sewage systems. The relative shares of diffuse and point sources varied greatly among nutrient forms and sub-basins. To meet critical loads, river export of TDN and TDP needs to be reduced by 46–92%, depending on the desired level of chlorophyll-a. There are different opportunities to meet the critical loads. Reducing N inputs from synthetic fertilizers and P from sewage systems may be sufficient to meet the least strict critical loads. A combination of reductions in diffuse and point sources is needed to meet the most strict critical loads. Combining improved nutrient use efficiencies and best available technologies in wastewater treatment may be an effective opportunity. Our study can support the formulation of effective solutions for lake restoration.

Cryptosporidium concentrations in rivers worldwide
Vermeulen, Lucie C. ; Hengel, Marijke van; Kroeze, Carolien ; Medema, Gertjan ; Spanier, J.E. ; Vliet, Michelle T.H. van; Hofstra, Nynke - \ 2019
Water Research 149 (2019). - ISSN 0043-1354 - p. 202 - 214.
Global - Model - Pathogens - Surface water - Transport - Water quality

Cryptosporidium is a leading cause of diarrhoea and infant mortality worldwide. A better understanding of the sources, fate and transport of Cryptosporidium via rivers is important for effective management of waterborne transmission, especially in the developing world. We present GloWPa-Crypto C1, the first global, spatially explicit model that computes Cryptosporidium concentrations in rivers, implemented on a 0.5 × 0.5° grid and monthly time step. To this end, we first modelled Cryptosporidium inputs to rivers from human faeces and animal manure. Next, we use modelled hydrology from a grid-based macroscale hydrological model (the Variable Infiltration Capacity model). Oocyst transport through the river network is modelled using a routing model, accounting for temperature- and solar radiation-dependent decay and sedimentation along the way. Monthly average oocyst concentrations are predicted to range from 10−6 to 102 oocysts L−1 in most places. Critical regions (‘hotspots’) with high concentrations include densely populated areas in India, China, Pakistan and Bangladesh, Nigeria, Algeria and South Africa, Mexico, Venezuela and some coastal areas of Brazil, several countries in Western and Eastern Europe (incl. The UK, Belgium and Macedonia), and the Middle East. Point sources (human faeces) appears to be a more dominant source of pollution than diffuse sources (mainly animal manure) in most world regions. Validation shows that GloWPa-Crypto medians are mostly within the range of observed concentrations. The model generally produces concentrations that are 1.5–2 log10 higher than the observations. This is likely predominantly due to the absence of recovery efficiency of the observations, which are therefore likely too low. Goodness of fit statistics are reasonable. Sensitivity analysis showed that the model is most sensitive to changes in input oocyst loads. GloWPa-Crypto C1 paves the way for many new opportunities at the global scale, including scenario analysis to investigate the impact of global change and management options on oocysts concentrations in rivers, and risk analysis to investigate human health risk.

Bridging global, basin and local-scale water quality modeling towards enhancing water quality management worldwide
Tang, Ting ; Strokal, Maryna ; Vliet, Michelle T.H. van; Seuntjens, Piet ; Burek, Peter ; Kroeze, Carolien ; Langan, Simon ; Wada, Yoshihide - \ 2019
Current Opinion in Environmental Sustainability 36 (2019). - ISSN 1877-3435 - p. 39 - 48.

Global water quality (WQ) modeling is an emerging field. In this article, we identify the missing linkages between global and basin/local-scale WQ models, and discuss the possibilities to fill these gaps. We argue that WQ models need stronger linkages across spatial scales. This would help to identify effective scale-specific WQ management options and contribute to future development of global WQ models. Two directions are proposed to improve the linkages: nested multiscale WQ modeling towards enhanced water management, and development of next-generation global WQ models based-on basin/local-scale mechanistic understanding. We highlight the need for better collaboration among WQ modelers and policy-makers in order to deliver responsive water policies and management strategies across scales.

Nutrient losses to surface waters in Hai He basin : A case study of Guanting reservoir and Baiyangdian lake
Yang, Jing ; Strokal, Maryna ; Kroeze, Carolien ; Wang, Mengru ; Wang, Jingfei ; Wu, Yihong ; Bai, Zhaohai ; Ma, Lin - \ 2019
Agricultural Water Management 213 (2019). - ISSN 0378-3774 - p. 62 - 75.
Agriculture - Baiyangdian lake - Guanting reservoir - MARINA model - Scenarios - Water pollution

Hai He basin is located in the densely populated North China Plain that is providing food to more than 100 million people. The fast developing agriculture and urbanization in Hai He basin have resulted in discharging nutrient-rich wastewater into lakes and reservoirs, leading to eutrophication and water scarcity such as in Guanting reservoir and Baiyangdian lake. In this study we analyzed future trends in nutrient inputs into Guanting reservoir and Baiyangdian lake by applying the MARINA (Model to Assess River Inputs of Nutrients to seAs) model. We analyzed trends between 2012 and 2050 for a business-as-usual scenario (SSP3) and a scenario based on Current Environmental Policies (CEP). In addition, we assessed future impacts of two important events on river export of nutrients: the 2022 Olympic Winter Games in the Guanting basin (OLY scenario), and the development of Xiong'an in the Baiyangdian basin (URB scenario). Finally, we assumed implementation of advanced technologies to reduce nutrients in rivers (OLY+ and URB+). Our study has five main findings. First, nutrients in Guanting reservoir and Baiyangdian lake were mainly from agriculture in 2012. Second, nutrient export doubles between 2012 and 2050 in SSP3. Third, effective implementation of current environmental policies could reduce the future pollution to levels below that in 2012. Fourth, improved sewage systems associated with the 2022 Winter Olympic Games could not reduce nutrient pollution effectively in Guanting reservoir, indicating that reducing nutrient losses from agriculture may be more effective to improve water quality than urban waste water treatment. Fifth, urbanization in the Baiyangdian basin may increase river export of nutrients to the lake by 28-43% compared to the CEP scenario (URB scenario). Highly effective waste treatment is needed not only in Xiong'an but also in surrounding areas to ensure the availability of clean water (URB+ scenario). Our results could improve our understanding of nutrient management for specific lakes and reservoirs, and highly relevant for policy making for effective environmental policies.

Global multi-pollutant modelling of water quality: scientific challenges and future directions
Strokal, M. ; Spanier, Emiel ; Kroeze, C. ; Koelmans, A.A. ; Florke, Martina ; Franssen, W.H.P. ; Hofstra, N. ; Langan, Simon ; Ting, Tang ; Vliet, M.T.H. van; Wada, Yoshihide ; Wang, M. ; Wijnen, Jikke van; Williams, R. - \ 2019
Current Opinion in Environmental Sustainability 36 (2019). - ISSN 1877-3435 - p. 116 - 125.
Assessing global water quality issues requires a multi-pollutant modelling approach. We discuss scientific challenges and future directions for such modeling. Multi-pollutant river models need to integrate information on sources of pollutants such as plastic debris, nutrients, chemicals, pathogens, their effects and possible solutions. In this paper, we first explain what we consider multi-pollutant modelling. Second, we discuss scientific challenges in multi-pollutant modelling relating to consistent model inputs, modelling approaches and model evaluation. Next, we illustrate the potential of global multi-pollutant modelling for hotspot analyses. We show hotspots of river pollution with microplastics, nutrients, triclosan and Cryptosporidium in many sub-basins of Europe, North America and South Asia. Finally, we reflect on future directions for multi-pollutant modelling, and for linking model results to policy-making.
Modeling nutrients in Lake Dianchi (China) and its watershed
Li, Xiaolin ; Janssen, Annette B.G. ; Klein, Jeroen J.M. de; Kroeze, Carolien ; Strokal, Maryna ; Ma, Lin ; Zheng, Yi - \ 2019
Agricultural Water Management 212 (2019). - ISSN 0378-3774 - p. 48 - 59.
Critical loading - MARINA nutrient model - Mining - PCLake ecosystem model - River export of nutrients

Lake Dianchi suffered from severe eutrophication for decades. Past efforts to reduce the eutrophication were not very effective. The objective of this study is to improve our understanding of nitrogen (N) and phosphorus (P) loadings and to analyze to what extent they exceed critical nutrient loadings of Lake Dianchi. To this end, we applied the nutrient MARINA model and the ecosystem model PCLake. Results show that river export of dissolved N and P was high in 2012. About 6 209 ton of total dissolved N (TDN) was exported to the lake (i.e. 23.6 kg ha−1), of which more than two-thirds in the form of dissolved inorganic N. For total dissolved P, this export was about 413 ton (i.e. 1.6 kg ha−1), of which 75% dissolved inorganic P. Urban sewage is a major source of nutrients in rivers in the northern sub-basins. In southern sub-basins, agriculture is an important source of both N and P, while P mining and processing is a major source of dissolved inorganic P. Nutrient inputs to the lake are particularly high from urbanization sub-basins draining into the northern part of the lake (Caohai). Critical nutrient loadings for the northern part of the lake (Caohai) are 0.34 mg P m−2d−1 (3.06 mg N m−2d−1) and for the southern part (Waihai) 0.38 mg P m−2d−1 (3.42 mg N m−2d−1). Actual loadings exceed the critical nutrient loadings by 82 times and 17 times of Caohai and Waihai, respectively. Our study illustrates how linking MARINA with PCLake helped to quantify the causes of lake eutrophication and to identify critical loadings for N and P in the lake. Our study can assist local authorities to formulate management options to reduce nutrient pollution in Lake Dianchi in the future.

Causal relationship in the interaction between land cover change and underlying surface climate in the grassland ecosystems in China
Li, Zhouyuan ; Wang, Zezhong ; Liu, Xuehua ; Fath, Brian D. ; Liu, Xiaofei ; Xu, Yanjie ; Hutjes, Ronald ; Kroeze, Carolien - \ 2019
Science of the Total Environment 647 (2019). - ISSN 0048-9697 - p. 1080 - 1087.
Cause-effect - Correlation analysis - Eco-climatology - Grassland - Land-climate - Remote sensing

Land-climate interactions are driven by causal relations that are difficult to ascertain given the complexity and high dimensionality of the systems. Many methods of statistical and mechanistic models exist to identify and quantify the causality in such highly-interacting systems. Recent advances in remote sensing development allowed people to investigate the land-climate interaction with spatially and temporally continuous data. In this study, we present a new approach to measure how climatic factors interact with each other under land cover change. The quantification method is based on the correlation analysis of the different order derivatives, with the canonical mathematical definitions developed from the theories of system dynamics and practices of the macroscopic observations. We examined the causal relationship between the interacting variables on both spatial and temporal dimensions based on macroscopic observations of land cover change and surface climatic factors through a comparative study in the different grassland ecosystems of China. The results suggested that the interaction of land-climate could be used to explain the temporal lag effect in the comparison of the three grassland ecosystems. Significant spatial correlations between the vegetation and the climatic factors confirmed feedback mechanisms described in the theories of eco-climatology, while the uncertain temporal synchronicity reflects the causality among the key indicators. This has been rarely addressed before. Our research show that spatial correlations and the temporal synchronicity among key indicators of the land surface and climatic factors can be explained by a novel method of causality quantification using derivative analysis.

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