EFFECTS, FATE AND UPTAKE OF NANOPESTICIDES IN THE TERRESTRIAL ENVIRONMENT

Over the past few decades a significant body of work has been done to understand the ecological and health risks of synthetic pyrethroid pesticides (SPs). Recently the use of nano-encapsulated SPs has been proposed. As nanoparticles can behave very differently from dissolved chemicals, it is possible that the effects, fate and uptake of these nano-formulated pesticides could be very different from the conventional SPs. This study therefore investigated the effects of nano-encapsulation on the fate and uptake of bifenthrin, a widely used third generation synthetic pyrethroid, in soil systems. Studies were performed, using Organisation for Economic Co-operation and Development (OECD) Guidelines and similar methods, on five soil types with different properties (total organic carbon and texture) to determine dissipation half-lives in soil, soil-water partition coefficients and uptake and depuration in the earthworm Eisenia fetida using analytical grade bifenthrin, a conventional bifenthrin formulation (Capture LFR) and two nano-formulations. Persistence, sorption and uptake behavior of all the study materials varied across soil types. Generally, the persistence, sorption and uptake of bifenthrin in the conventional formulation were similar to the behavior of the non-formulated active ingredient. However, nanoencapsulation significantly affected the behavior of the bifenthrin. Results for the two nanoformulations were similar to each other but these showed enhanced persistence, decreased sorption and increased rates of uptake and depuration in the earthworms compared to the analytical grade material and the conventional formulation. We therefore anticipate that the distribution and impacts of the nanoformulation in natural soil systems will be different from currently used formulations. The observed differences in persistence and sorption behavior are possibly due to the polymer capsule ‘protecting’ the active ingredient from microbes and soil binding sites. Differences in uptake might be explained by differences in distribution of the bifenthrin within the organism (i.e., the nanoformulation is accummulating in the earthworm gut while bifenthrin in the conventional and non-formulated treatments is being internalised).