Pesticide behavior in modified water-sediment systems

Abstract

The standardized laboratory water-sediment study in darkness is utilized as primary information on pesticide behavior to assess its ecotoxicological impacts in the edge-of-field water bodies. The half-lives of pesticide in water and sediment are key parameters to predict its environmental concentration, and its metabolic profiles help to avoid overlooking unexpected toxicological impacts from metabolites. However, no consideration of environmental factors such as sunlight and aquatic macrophytes is included, and this may lead to a conservative assessment. We review the experimental factors in the existing standardized design and then the effects of illumination and aquatic macrophytes introduced to the water-sediment system. The effects of temperature and the water-sediment ratio should be investigated in more detail and the pesticide behavior is possibly modified by illumination via photodegradation and/or metabolism in phototrophic microorganisms. Aquatic macrophytes play a major role as an additional sorption site and in further pesticide metabolism.

Phase Transfer and Biodegradation of Pesticides in Water–Sediment Systems Explored by Compound-Specific Isotope Analysis and Conceptual Modeling

“…Pesticide biodegradation rates derived from laboratory experiments usually serve to predict the pesticide behavior in the environment . However, concerns have been recently raised about the representativeness of the study conditions, claiming that the derived pesticide biodegradation rates may be biased if co-occurring dissipation processes are not considered. , Recently, a conceptual model to evaluate the processes contributing to pesticide dissipation has been validated for a broad spectrum of compounds and study conditions. , The model considers phase transfer between the water phase with freely dissolved species and the sediment phase including species sorbed on particles or dissolved organic carbon (DOC). However, knowledge of the contribution of pesticide biodegradation and phase transfer to the overall pesticide dissipation in surface water remains scarce, although this information is crucial for both sediment and water management.…”

Inverse analysis to estimate site‐specific parameters of a mathematical model for simulating pesticide dissipations in paddy test systems

“…The potential problem of our approach is that the model was over‐calibration of the parameters regarding the interfacial transport such as K d and k SORP since the pesticide concentration in soil was not available in the experimental design like this study. Parameterization by the laboratory water‐sediment study and its inverse modeling using tested soils is expected to reduce this risk as well as deriving reliable k DEG‐PSL and k DIFF uncalibrated in this study.…”

Theoretical and organic chemical approaches to environmental behavior and metabolism of pesticides

“…In the natural environment, the overlying water is diurnally exposed to sunlight. 5) In order to examine the illumination effect on the pesticide behavior, we conducted water-sediment studies not only in darkness but also with exposure to simulated sunlight ( Fig. 9) for several pesticides with different physicochemical properties and abiotic degradation profiles, as listed in Table 2.…”

“…3) A water-sediment study examines multiple processes, such as partition, hydrolysis and microbial metabolism, at the same time, but either the dark condition or the absence of algae/aquatic plants may lead to pesticide behavior different from that in the aquatic environment. 4,5) Additionally, the standard studies examining physicochemical properties and environmental fate are conducted for an active ingredient, and so the effect of formulation on the pesticide behavior cannot be examined. 6) Second, multiple reactions proceed simultaneously in the environment, in contrast to many standardized studies.…”