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Microplastic pollution in soils is a recent environmental problem and the lack of knowledge about the impacts and the extent of the problem are raising questions and concerns among researchers and politicians. Using a normative simulation model, we assess the extent of microplastic pollution in German agricultural soils originating from the land application of sewage sludge and compost. We estimate the microplastic concentration in German agricultural soils, the area of polluted land, and we compare the efficiency and effectiveness of some selected abatement measures. For 2020, we estimate that microplastic concentration in agricultural soil reaches a maximum concentration of between 30 and 50 mg/kg dry weight on 2% of utilised agricultural area and a marginal concentration on 22% of utilised agricultural area. Without the implementation of abatement measures, we expect the microplastic concentration to increase two to three times by 2060. Assessing the abatement measures, we find that for sewage sludge, thermal recycling is a more efficient and effective than equipping washing machines with microplastic-filters in private households. The use of plastic detection systems in the biowaste collection process reduces the plastic content of the compost and thus the release of microplastic into the soil. Detection systems are a more efficient measure for compost than thermal recycling. Concerning sludge, the findings indicate that the German strategy of thermally recycling sewage sludge is an efficient and effective measure to reduce microplastic pollution in soils. Reducing the plastic content of collected biowaste complies with the principles of a circular economy. [ABSTRACT FROM AUTHOR]

Microplastic pollution has recently gained the attention of the public media, politics and research. Microplastics (i.e., plastic particles less than 5mm in size) have been identified as a global environmental threat for terrestrial and aquatic ecosystems and human health. Agriculture is assumed to be both victim and polluter. Agricultural soils receive microplastic immissions from tire wear and fragmented macroplastic that enters the environment through littering. Furthermore, farmers who fertilize their arable land with sewage sludge and compost unintentionally apply the microplastic particles contained in these biosolids. On the other hand, agricultural soils may emit microplastics into aquatic environments. Because of this ambivalent position as both victim and polluter, the information on microplastic pollution is of current interest for agricultural production and might become a relevant topic for agro-environmental policies in the future. Our research aims to quantify the microplastic immissions into agricultural soils and emissions from agricultural soils into aquatic systems. We use different analysis approaches and interdisciplinary modelling to address these aims for two case studies in Germany. Because research in microplastics is a relatively new concern, we combine different methodological approaches in a complementary way. [ABSTRACT FROM AUTHOR]

Even though perfluoroalkyl substances (PFAS) are mainly used in industrial processes and consumer products, they have often been detected in agricultural environments and groundwater in recent years. While some sources are directly connected to contamination events (such as PFAS from fire-fighting foam), other sources may be more continuous. Especially soil melioration by applying sewage sludge and compost may provide long-term input into the agricultural environment. However, it is unclear if all PFAS are available in sewage sludge and compost or if their occurrence is selective. Therefore, we investigated 201 samples of sewage sludge and 45 samples of biowaste for their concentrations of 14 different PFAS. The results suggests that sewage sludge functions as a sink for long-chain PFAS, and the plants preferentially take up short-chain PFAS from the sludge/soil, as seen by the concentrations found in biowaste. This behaviour may be an effect of substance adsorption, which is stronger for long-chain and weaker for short-chain PFAS. Our results also indicate that about 15 kg of PFAS are spread onto agricultural fields in Germany each year via sewage sludge.Following application, the behaviour of PFAS in soils is still poorly understood. While there is evidence that they behave similarly to other organic agrochemicals such as pesticides, their partial dissipation during soil passage was rather attributed to irreversible adsorption than biodegradation. In order to test the applicability of well-known environmental fate process descriptions, we used the pesticide leaching model MACRO for the simulation of the two lead substances of PFAS: perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). The model was set up by using soil and crop rotation data of a long-term field lysimeter study investigating the leaching of PFOS and PFOA over a period of eight years. Irreversible adsorption was mimicked in the model by degradation in the adsorbed phase. Using this setup, the MACRO model was able to reproduce water and substance leaching within parameter ranges taken from the literature. The dynamics of plant uptake could only partially be reproduced. Concluding, PFAS leaching may be estimated using similar environmental fate descriptions than pesticides.In order to examine the groundwater contamination potential resulting from leaching of different PFAS, we sampled 364 groundwater monitoring wells in the federal state of Hesse, Germany, from 2009 – 2016 for 21 PFAS, which resulted in 32800 concentration values. Positive PFAS values were found in about 90 % of the investigated monitoring wells. PFOA and PFOS were found in 45 % (average of 1.2 ng/l), the short-chain PFAS in 29 % (average of 0.7 ng/l) and the long-chain PFAS in 5 % (average of 0.07 ng/l) of the samples. This shows, that more mobile PFAS (short-chain) and PFAS with the highest usage (PFOS and PFOA) are most likely found in groundwater, whereas long-chain PFAS may be mostly retained in the soils during leaching.These studies suggest that, even though PFAS are not deliberately introduced into the environment, their mode of application, their behaviour in agricultural soils and their ubiquitous occurrence in groundwater is similar to other organic agrochemicals. [ABSTRACT FROM AUTHOR]