Assessing the fate of pesticides and water-borne contaminants in agricultural crops and their environmental risks

Sustainable water management for future farming production is an urgent issue. While some regions, e.g. Scandinavian countries, with high and evenly distributed rainfall usually rely on rain fed agriculture, farmers from many other European countries are facing water shortages, and use treated wastewater for irrigation of agricultural fields. However, this may result in introduction of organic micro-pollutants like pharmaceuticals from the wastewater. On the other side, application of pesticides in agriculture is a concern due to leaching and runoff to groundwater and surface water. Riparian strips/zones are among the most important areas for protecting or lowering the impact of pesticides runoff from arable land to freshwater ecosystems. In this project, the idea was that these riparian strips can be enforced as a kind of advanced `treatment wetlands. One of the main ambitions in this WP was to provide a new solution ? a novel filter bed material mixture - to reduce runoff impact of pesticides (or other contaminants), in particular the most mobile pesticides. The novel idea was use of a superabsorbent polymer (SAP) as part of a filter material mixture. Results based on batch scale kinetic studies, planted horizontal subsurface flow constructed wetlands (CW) system, and microcosms pot experiments shows that an optimised and properly designed SAP containing filter bed system can improve retention of high mobile organic pollutants, however, careful evaluation of what is the most suitable SAP is urgent for the given situation. The selected SAP showed higher retention for neutral pesticides, imidacloprid, propiconazole and metalaxyl, whereas lower for anionic pesticides, bentazone, glyphosate and MCPA. The SAP is an anionic polymer, and the retention of anionic pesticides was less due to electrostatic repulsion. Among the neutral pesticides, metalaxyl, which has the highest water solubility, displayed lower retention than imidacloprid and propiconazole. Selection of plant species in planted bed need also consideration in the case where systemic pollinator-toxic insecticides are used, since uptake and translocation was higher in plants in filter systems than in soil. Degradation kinetics of imidacloprid, propiconazole, metalaxyl, MCPA, bentazone and pencycuron in agricultural soil during different tempetures (5, 12, 22 ?C) and at 22 ?C under aerobic and methanogenic conditions has been performed. The kinetics (d-1) and half-lives (DT50 d) obtained in the project will be support for risk evaluation and management of pesticides. Our results showed that the degradation rate of imidacloprid and metalaxyl were higher under methanogenic than aerobic conditions and the DT50 was reduced from 62 to 10 d, and from 175 to 25 d, respectively. Recycling of organic waste containing pesticides (or other emerging contaminants) is a potential risk for spreading hazard into the environment. For organic waste with organic contaminants with a higher degradability under methanogenic than aerobic conditions, used as substrate in biogas production followed by composting before used as soil improvers is an option to reduce spreading potential hazard compounds.

The project shows that an optimised and properly designed SAP containing filter bed system can improve retention of highly mobile organic pollutants, however careful evaluation of what is the most suitable SAP is urgent for the given situation. Selection of plant species in planted bed need consideration in the case where systemic pollinator-toxic insecticides are used, since high uptake and translocation were measured in filter systems (much higher than in soil). Determination of degradation kinetics of pesticides under different temperatures will be used in risk evaluation and possible also related to risk management. Recycling of organic waste containing pesticides (or other emerging contaminants) is a potential risk for spreading hazard into the environment. Our results show that organic waste with a potential threat, used as substrate in biogas production followed by composting before used as soil improvers is an option to reduce spreading potential hazard compounds.

At global scale, agriculture accounts for about 70% of the total freshwater consumption and has been identified to contribute to water pollution. A major concern is related to the application of pesticides in agriculture which manifests in groundwater contamination, surface run-off and plant uptake. Moreover, poor regional water management practices can be a further factor contributing to pollution of agricultural ecosystems. While some regions, e.g. Scandinavian countries, with high and evenly distributed rainfall usually rely on natural precipitation, farmers from many other European countries are facing increasing difficulty in supplying water demand, and use treated wastewater for irrigation of agricultural fields. However, this poses the problem of introducing organic micro-pollutants like pharmaceuticals from the wastewater into the terrestrial environment. The AWARE project will investigate uptake, metabolism, fate and risks of selected compounds in plants and also in soil or wetland systems through a multidisciplinary approach including wide expertise (environmental- and analytical chemistry, environmental toxicology, plant physiology, microbiology), various partners (academic and research institutes) and stakeholders. AWARE will close knowledge gaps and help to shape the EU regulatory framework to manage health and environmental risks. The Norwegian contribution, together with UFZ Leipzig, will be investigating fate of pesticides in mixture, particularly focus at the water soluble and mobile ones, and how to optimize for retaining and degradation of these. Isotope- and non-labelled pesticides will be used to study sorption, biodegradation and non-extractable-residue-formation in controlled laboratory and constructed wetland. Riparian strips are important areas for lowering the impact of pesticides runoff from arable land to freshwater ecosystems. A new approach for reducing pesticide runoff at riparian strips will be investigated.