PWC-based evaluation of groundwater pesticide pollution in the Júcar River Basin

Exploration of a comprehensive versus a regulatory-oriented modeling framework for field pesticide transport assessment

Numerous computer models have been developed for simulating pesticide fate and transport. It is usually hard to choose which model is the best for a particular research or regulatory purpose. Currently, the PRZM (Pesticide Root Zone Model) model is widely used for regulatory purposes regarding runoff and erosion. However, it simplifies many hydrological processes and management practices which affect pesticide fate simulations. In this study, the APEX (Agricultural Policy / Environmental eXtender model) model, which is more comprehensive and may provide a more realistic representation of pesticide fate, was compared with the PRZM model regarding methods and capabilities of characterizing hydrology, management, and pesticide transport. Four case studies were used to compare the performances of the two models for simulating surface runoff, sediment yield, pesticide in runoff, and pesticide in sediment. Results showed that the APEX model performed better than the PRZM model for simulating surface runoff and sediment yield, and performed similarly to the PRZM model for simulating pesticide loads in runoff and erosion. Both models have limitations for capturing the runoff events caused by high intensity rainfall. APEX is superior to PRZM in simulating detailed management operations, considering more hydrological processes, and achieving spatially distributed simulation, but it requires a higher number of inputs and user-selected parameters compared to PRZM. With further validations of the capabilities of APEX in pesticide modeling and the development of web-based platforms to facilitate the set up and use of comprehensive models, a more accurate and reliable pesticide assessment scheme is anticipated by using comprehensive models like APEX.

Human Exposure to Pesticides in Dust from Two Agricultural Sites in South Africa

Over the last decades, concern has arisen worldwide about the negative impacts of pesticides on the environment and human health. Exposure via dust ingestion is important for many chemicals but poorly characterized for pesticides, particularly in Africa. We investigated the spatial and temporal variations of 30 pesticides in dust and estimated the human exposure via dust ingestion, which was compared to inhalation and soil ingestion. Indoor dust samples were collected from thirty-eight households and two schools located in two agricultural regions in South Africa and were analyzed using high-performance liquid chromatography coupled to tandem mass spectrometry. We found 10 pesticides in dust, with chlorpyrifos, terbuthylazine, carbaryl, diazinon, carbendazim, and tebuconazole quantified in >50% of the samples. Over seven days, no significant temporal variations in the dust levels of individual pesticides were found. Significant spatial variations were observed for some pesticides, highlighting the importance of proximity to agricultural fields or of indoor pesticide use. For five out of the nineteen pesticides quantified in dust, air, or soil (i.e., carbendazim, chlorpyrifos, diazinon, diuron and propiconazole), human intake via dust ingestion was important (>10%) compared to inhalation or soil ingestion. Dust ingestion should therefore be considered in future human exposure assessment to pesticides.