Assessing annual, seasonal and spatial trends in copper sediment concentrations from a California agricultural waterbody.

The objective of this study was to assess annual, seasonal and spatial trends in copper sediment concentrations in an agricultural California stream (Cache Slough) based on sampling 12 sites over two seasons (spring and fall) in 2012, 2013 and 2014. The relationship between copper sediment concentrations and precipitation was also evaluated. The results from this study showed that copper sediment concentrations from Cache Slough ranging from 19 to 63 ug/g dw were similar to concentrations reported in European agricultural streams. Copper sediment concentrations were not reported to increase over time in this agricultural waterbody where copper was used as a fungicide. However, spatial differences in copper sediment concentrations were reported among sites with the highest concentrations in the middle waterbody section. Seasonal analysis showed no significant difference in copper sediment concentrations for both spring and fall for 2012 and 2013 but 2014 spring concentrations were statistically higher than fall concentrations when precipitation was lower than the two previous years. There were no statistically significant relationships between copper sediment concentrations and precipitation for the three-year period based on an analysis by year and season.