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Purpose: The purpose of the present study are to analyze the temporal and spatial trends of the pesticide use on almond crops and assess their associated risk to soil, surface water, and air, and to investigate the impacts of pesticide risk on biodiversity. Materials and methods: California Pesticide Use Report database was used to determine the organophosphate (OP) and pyrethroid use trends in the San Joaquin Valley for almonds from 1992 to 2005. Environmental potential risk indicator for pesticides model was employed to evaluate associated environmental relative risks in soil and in surface water. Emission potential of pesticide product was used to estimate the air relative risk. Geographical Information System was used to delineate the spatial distribution patterns of environmental risk evaluation in almonds and biodiversity. Results and discussion: OP pesticide use has been declined in any measurement in almonds. However, a converse result was found for pyrethroid pesticide. Pesticide use trends reflect the profound changes in pest management strategies in the California almond farm community. The model results in this study showed evidence that pyrethroid posed less environmental risks to soil, air, and water resources than OP. The physiochemical properties of pyrethroid reflect a strong tendency to adsorb to organic carbons, and therefore, potentially move off-site attached to sediment. Once in sediments, they can be bioavailable to the aquatic food web. So, more future study on environmental model should address pyrethroid environmental risk on sediment. Ecologists revealed that endangered species diversity has good correlation with total species diversity, so we developed a biodiversity index by using the survey data of endangered and rare animals in California. The results showed a negative relationship between count of animal occurrence and predicted environmental risk. This result would be useful to help conserve California's biological diversity by providing information to promote agricultural management and land-use decisions. Conclusions: Pesticide use trend is directly related to environmental risk. Pyrethroid posed less environmental risk than OP in this study. And also, this study got a noticeable result that pesticide uses in intensive agriculture and their associated environmental risks pose negative impacts on biodiversity. [ABSTRACT FROM AUTHOR]

Abstract: The hydrology, sediment, and pesticide transport components of the Soil and Water Assessment Tool (SWAT) were evaluated on the northern San Joaquin Valley watershed of California. The Nash–Sutcliffe coefficients for monthly stream flow and sediment load ranged from 0.49 to 0.99 over the watershed during the study period of 1992–2005. The calibrated SWAT model was applied to simulate fate and transport processes of two organophosphate pesticides of diazinon and chlorpyrifos at watershed scale. The model generated satisfactory predictions of dissolved pesticide loads relative to the monitoring data. The model also showed great success in capturing spatial patterns of dissolved diazinon and chlorpyrifos loads according to the soil properties and landscape morphology over the large agricultural watershed. This study indicated that curve number was the major factor influencing the hydrology while pesticide fate and transport were mainly affected by surface runoff and pesticide application and in the study area. [Copyright &y& Elsevier]

Abstract: In the last decade, the detection of organophosphate (OP) pesticides in the San Joaquin River watershed has raised concerns about water quality. This study examined the influences of almond pest management practices (PMPs) on water quality. The Soil and Water Assessment Tool (SWAT) model was employed to simulate pesticide concentration in water as affected by different PMPs. California Pesticide Use Reporting (PUR) data were used to investigate PMP use trends. Stepwise regression analysis was performed to test the correlation between specific PMP use and pesticide concentrations in surface water and sediment. Our results showed an increasing use of reduced risk pesticides and pyrethroids on almonds. SWAT simulation over the period of 1992–2005 showed decreases in OP concentrations in surface water. High OP and pyrethroid use in dormant sprays was associated with high pesticide concentrations in water and sediment. Almond pesticide use was proved to have significant impacts on the pesticide load in the San Joaquin River watershed. The PMP which combines the use of reduced risk pesticides with no dormant spray was recommended for almond orchard use. This paper presented a novel method of studying the environmental impacts of different agricultural PMPs. By combining pesticide use surveys with watershed modeling, we provided a quantitative foundation for the selection of PMPs to reduce pesticide pollution in surface water. [Copyright &y& Elsevier]