Sewage sludge application as a vehicle for microplastics in eastern Spanish agricultural soils
Berg, Pim van den; Huerta-Lwanga, Esperanza ; Corradini, Fabio ; Geissen, Violette - \ 2020
Environmental Pollution 261 (2020). - ISSN 0269-7491
Agricultural soils - Microplastics - Sewage sludge
Microplastic pollution is becoming a major challenge with the growing use of plastic. In recent years, research about microplastic pollution in the environment has become a field of study with increased interest, with ever expanding findings on sources, sinks and pathways of microplastics. Wastewater treatment plants effectively remove microplastics from wastewater and concentrate them in sewage sludge which is often used to fertilise agricultural fields. Despite this, quantification of microplastic pollution in agricultural fields through the application of sewage sludge is largely unknown. In light of this issue, four wastewater treatment plants and 16 agricultural fields (0–8 sewage sludge applications of 20–22 tons ha−1 per application), located in the east of Spain, were sampled. Microplastics were extracted using a floatation and filtration method, making a distinction between light density microplastics (ρ < 1 g cm−3) and heavy density microplastics (ρ > 1 g cm−3). Sewage sludge, on average, had a light density plastic load of 18,000 ± 15,940 microplastics kg−1 and a heavy density plastic load of 32,070 ± 19,080 microplastics kg−1. Soils without addition of sewage sludge had an average light density plastic load of 930 ± 740 microplastics kg−1 and a heavy density plastic load of 1100 ± 570 microplastics kg−1. Soils with addition of sewage sludge had an average light density plastic load of 2130 ± 950 microplastics kg−1 and a heavy density plastic load of 3060 ± 1680 microplastics kg−1. On average, soils’ plastic loads increased by 280 light density microplastics kg−1 and 430 heavy density microplastics kg−1 with each successive application of sewage sludge, indicating that sewage sludge application results in accumulation of microplastics in agricultural soils. Microplastics concentrations in soils are highly proportional to the number of sludge applications.
Short term changes in the abundance of nitrifying microorganisms in a soil-plant system simultaneously exposed to copper nanoparticles and atrazine
Parada, J. ; Rubilar, O. ; Sousa, D.Z. ; Martínez, M. ; Fernández-Baldo, M.A. ; Tortella, G.R. - \ 2019
Science of the Total Environment 670 (2019). - ISSN 0048-9697 - p. 1068 - 1074.
Agricultural soils - Atrazine - Combined pollution - Copper nanoparticles - Pesticides
Copper nanoparticles (NCu) may co-exist with other pollutants in agricultural soils, such as pesticides. However, this has been little evaluated yet. Thus, possible effects of the simultaneous applications of pesticides and NCu on biogeochemical cycles are expected, for example on the nitrogen cycle. Therefore, the aim of this work was to evaluate the effect of simultaneous application of the herbicide atrazine (ATZ) and NCu on the abundance of total bacteria and nitrifying communities: ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Moreover, the ATZ dissipation was evaluated. A soil-plant system containing ATZ at field dose (3 mg a.i. kg −1 ) was mixed with two doses of NCu (0.05% or 0.15% w/w). Changes in the abundance of 16S rRNA and ammonia monooxygenase (amoA) genes of AOA and AOB were evaluated by real-time quantitative PCR (qPCR) at three sampling times (1, 15 and 30 days). The residual ATZ and nitrate production were also measured. The results showed significant differences in microbial composition and abundance over the 30 days of the experiment. Particularly, an initial decrease was observed in total bacterial abundance due to the presence of ATZ and NCu respect to ATZ alone (~60%). The abundance of AOA was also remarkably reduced (~85%), but these communities gradually recovered towards the end of the experiment. Conversely, AOB abundance initially increased (>100%) and remained mainly unaltered in soil exposed to ATZ and NCu 0.15% w/w, where nitrate formation was also constant. Moreover, NCu decreased the ATZ dissipation, which was translated in a 2-fold increase on the ATZ half-life values (T 1/2 ). This study demonstrates that the simultaneous presence of NCu and ATZ may represent a risk for the total bacteria present in soil and sensitive microorganisms such as nitrifying communities, and changes in the dissipation of the pesticide could influence this process.
Digging deeper : Understanding the contribution of subsoil carbon for climate mitigation, a case study of Ireland
Simo, I. ; Schulte, R. ; O'Sullivan, L. ; Creamer, R. - \ 2019
Environmental Science & Policy 98 (2019). - ISSN 1462-9011 - p. 61 - 69.
Agricultural soils - Soil carbon mapping - Soil organic carbon stocks
In an attempt to counter the progress of climate change, the European Commission 2030 climate and energy framework developed a binding target to cut GHG emissions within the territory by at least 40% below 1990 levels, by 2030. In the past, this did not include the role of soils in providing a sink for carbon. As of 2014, the European Commission legislative proposed to integrate greenhouse gas emissions and removals from LULUCF in the 2030 climate and energy framework, allowing for the contribution of carbon sinks in national inventories. To calculate the potential of these sinks it is essential to firstly understand what stocks exist at a national scale and identify the so-called ‘carbon hotspots’ in the landscape to reduce the potential leaks in the system. This is further enhanced by identifying soils which provide the potential for further sequestration of carbon, due to their soil texture and aggregate composition. Moreover, deeper soil horizons may have a high capacity to sequester significant amounts of SOC as the turnover time and chemical recalcitrance of soil organic matter (SOM)increases with depth (Lorenz and Lal, 2005). This study highlights the need to dig deeper and assess soil carbon stocks below the standard 30 cm depth, applied in many calculations and models, in order to derive sufficiently accurate estimations of soil organic carbon (SOC)stocks and the total quantity of stable SOC at depth. Using Ireland as a case study, SOC stock maps are produced with the objective of identifying and securing existing information for SOC and to show the spatial distribution and geographical variation of SOC stock at different depths. Using empirical data from a national soil survey, SOC measurements from the surface 30 cm, 50 cm and 1 m were compared across all soil types. The results indicate a large variation between soils when comparing the SOC of the first 30 cm only, while the proportion of total SOC stock contained within 0–50 cm was more consistent within subgroups of soil types, and accounts for 90% of the carbon found to 1 m. Luvisols and Stagnosols have been previously identified as soils capable of sequestering larger stores of SOC in their subsoils. These soil types were spatially mapped and the stock converted to CO 2 emission equivalents. On average, up to 40 t ha −1 of stable SOC is contained at a depth below 30 cm. At national level, this adds up to 69 Mt of SOC. This research provides a spatially targeted approach that combines efforts to reduce CO 2 emissions from carbon hotspots while also augmenting the sequestration of stable carbon at depth in soils with clay illuviation and wetness (stagnic)diagnostic horizons.
Pesticide residues in European agricultural soils – A hidden reality unfolded
Silva, Vera ; Mol, Hans G.J. ; Zomer, Paul ; Tienstra, Marc ; Ritsema, Coen J. ; Geissen, Violette - \ 2019
Science of the Total Environment 653 (2019). - ISSN 0048-9697 - p. 1532 - 1545.
Agricultural soils - European Union - Mixtures of pesticide residues - Predicted environmental concentrations in soil (PECs) - Risk assessment
Pesticide use is a major foundation of the agricultural intensification observed over the last few decades. As a result, soil contamination by pesticide residues has become an issue of increasing concern due to some pesticides' high soil persistence and toxicity to non-target species. In this study, the distribution of 76 pesticide residues was evaluated in 317 agricultural topsoil samples from across the European Union. The soils were collected in 2015 and originated from 11 EU Member States and 6 main cropping systems. Over 80% of the tested soils contained pesticide residues (25% of samples had 1 residue, 58% of samples had mixtures of two or more residues), in a total of 166 different pesticide combinations. Glyphosate and its metabolite AMPA, DDTs (DDT and its metabolites) and the broad-spectrum fungicides boscalid, epoxiconazole and tebuconazole were the compounds most frequently found in soil samples and the compounds found at the highest concentrations. These compounds occasionally exceeded their predicted environmental concentrations in soil but were below the respective toxic endpoints for standard in-soil organisms. Maximum individual pesticide content assessed in a soil sample was 2.05 mg kg−1 while maximum total pesticide content was 2.87 mg kg−1. This study reveals that the presence of mixtures of pesticide residues in soils are the rule rather than the exception, indicating that environmental risk assessment procedures should be adapted accordingly to minimize related risks to soil life and beyond. This information can be used to implement monitoring programs for pesticide residues in soil and to trigger toxicity assessments of mixtures of pesticide residues on a wider range of soil species in order to perform more comprehensive and accurate risk assessments.
A comparison of disaggregated nitrogen budgets for Danish agriculture using Europe-wide and national approaches
Kros, Johannes ; Hutchings, Nicholas J. ; Kristensen, Inge Toft ; Kristensen, Ib Sillebak ; Børgesen, Christen Duus ; Voogd, Jan Cees ; Dalgaard, Tommy ; Vries, Wim de - \ 2018
Science of the Total Environment 643 (2018). - ISSN 0048-9697 - p. 890 - 901.
Agricultural soils - Budgets - Disaggregation - Modelling - National - Nitrogen
Spatially detailed information on agricultural nitrogen (N) budgets is relevant to identify regions where there is a need for a reduction in inputs in view of various forms of N pollution. However, at the scale of the European Union, there is a lack of consistent, reliable, high spatial resolution data necessary for the calculation of regional N losses. To gain insight in the reduction in uncertainty achieved by using higher spatial resolution input data. This was done by comparing spatially disaggregated agricultural N budgets for Denmark for the period 2000–2010, generated by two versions of the European scale model Integrator, a version using high spatial resolution national data for Denmark (Integrator-DK) and a version using available data at the EU scale (Integrator-EU). Results showed that the national N fluxes in the N budgets calculated by the two versions of the model were within 1–5% for N inputs by fertilizer and manure excretion, but inputs by N fixation and N mineralisation differed by 50–100% and N uptake also differed by ca 25%, causing a difference in N leaching and runoff of nearly 50%. Comparison with an independently derived Danish national budget appeared generally to be better with Integrator-EU results in 2000 but with Integrator-DK results in 2010. However, the spatial distribution of manure distribution and N losses from Integrator-DK were closer to observed distributions than those from Integrator-EU. We conclude that close attention to local agronomic practices is needed when using a leaching fraction approach and that for effective support of environmental policymaking, Member States need to collect or submit high spatial resolution agricultural data to Eurostat.
Advantages and limitations of chemical extraction tests to predict mercury soil-plant transfer in soil risk evaluations
Monteiro, R.J.R. ; Rodrigues, S.M. ; Cruz, N. ; Henriques, B. ; Duarte, A.C. ; Römkens, P.F.A.M. ; Pereira, E. - \ 2016
Environmental Science and Pollution Research 23 (2016)14. - ISSN 0944-1344 - p. 14327 - 14337.
Agricultural soils - Chemical availability - Mercury - Plant uptake - Risk assessment - Soil tests
In this study, we compared the size of the mobile Hg pool in soil to those obtained by extractions using 2 M HNO3, 5 M HNO3, and 2 M HCl. This was done to evaluate their suitability to be used as proxies in view of Hg uptake by ryegrass. Total levels of Hg in soil ranged from 0.66 to 70 mg kg−1 (median 17 mg kg−1), and concentrations of Hg extracted increased in the order: mobile Hg <2 M HNO3 <5 M HNO3 <2 M HCl. The percentage of Hg extracted relative to total Hg in soil varied from 0.13 to 0.79 % (for the mobile pool) to 4.8–82 % (for 2 M HCl). Levels of Hg in ryegrass ranged from 0.060 to 36 mg kg−1 (median 0.65 mg kg−1, in roots) and from 0.040 to 5.4 mg kg−1 (median 0.34 mg kg−1, in shoots). Although results from the 2 M HNO3 extraction appeared to the most comparable to the actual total Hg levels measured in plants, the 2 M HCl extraction better expressed the variation in plant pools. In general, soil tests explained between 66 and 86 % of the variability of Hg contents in ryegrass shoots. Results indicated that all methods tested here can be used to estimate the plant total Hg pool at contaminated areas and can be used in first tier soil risk evaluations. This study also indicates that a relevant part of Hg in plants is from deposition of soil particles and that splashing of soil can be more significant for plant contamination than actual uptake processes. [Figure not available: see fulltext.]
Selenium speciation and extractability in Dutch agricultural soils
Supriatin, Supriatin ; Weng, Liping ; Comans, Rob N.J. - \ 2015
Science of the Total Environment 532 (2015). - ISSN 0048-9697 - p. 368 - 382.
Agricultural soils - Organic carbon - Selenium - Soil extraction - Speciation
The study aimed to understand selenium (Se) speciation and extractability in Dutch agricultural soils. Top soil samples were taken from 42 grassland fields and 41 arable land fields in the Netherlands. Total Se contents measured in aqua regia were between 0.12 and 1.97mgkg-1(on average 0.58mgkg-1). Organic Se after NaOCl oxidation-extraction accounted for on average 82% of total Se, whereas inorganic selenite (selenate was not measurable) measured in ammonium oxalate extraction using HPLC-ICP-MS accounted for on average 5% of total Se. The predominance of organic Se in the soils is supported by the positive correlations between total Se (aqua regia) and total soil organic matter content, and Se and organic C content in all the other extractions performed in this study. The amount of Se extracted followed the order of aqua regia>1M NaOCl (pH8)>0.1M NaOH>ammonium oxalate (pH3)>hot water>0.43M HNO3>0.01M CaCl2. None of these extractions selectively extracts only inorganic Se, and relative to other extractions 0.43M HNO3 extraction contains the lowest fraction of organic Se, followed by ammonium oxalate extraction. In the 0.1M NaOH extraction, the hydrophobic neutral (HON) fraction of soil organic matter is richer in Se than in the hydrophilic (Hy) and humic acid (HA) fractions. The organic matter extracted in 0.01M CaCl2 and hot water is in general richer in Se compared to the organic matter extracted in 0.1M NaOH, and other extractions (HNO3, ammonium oxalate, NaOCl, and aqua regia). Although the extractability of Se follows to a large extent the extractability of soil organic carbon, there is several time variations in the Se to organic C ratios, reflecting the changes in composition of organic matter extracted.