Delivery of Agricultural Chemicals to Surface and Groundwaters

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Behaiviors of agricultural chemicals in a basin level have not been studied much. Especially, flow path of the chemicals through the basin to river should be studied intensively. In this study, behaviors of nitrate and PCNB in the Sugadaira Basin of Nagano Prefecture, especially during storm events, were studied. The results are summarized as follows :1. Nitrate and sulfate are dominant anions in groundwater of agricultural lands whose composition depends on its hydrologeologic conditions or oxdation-reduction conditions.2. Patterns of concentration changes of river water during storm discharge are classified into four, which reflect sources and flow path of the chemicals.3. During storms, chemical compositions of river water are unified from upstream to downstream and shown to be an agricultural type with high concentrations of nitrate and calcium, which shows that sources of chemicals are mainly from surrounded agricultural lands including ex-wetland.4. Concentrations of PCNB during storms show a different pattern from other chemicals such as nitrate and PCNB is supposed to be brought by suspended materials through surface runoff.