摘要
Groundwater comprises a large portion of irrigation for California＇s agriculture, and sustains a wide diversity of ecosystems as well as consumptive use, but pumping is occurring faster than replenishment. At the same time, contaminants from fertilizers and pesticides are infiltrating into the groundwater, becoming increasingly concentrated as water is extracted. It compared space-based observations of groundwater anomalies from California＇s San Joaquin Valley using the GRACE （gravity recovery and climate experiment） against measurements of 42 organic and inorganic chemicals from 41,667 wells in the valley from 2003 to 2010. It compared Arsenic, Boron, Cadmium, Chloride, Selenium, Trichloroethylene, and TDS （total dissolved solid） concentrations with the groundwater storage anomaly from 2003 to 2010. The results show strong correlations for groundwater depletion against increasing chloride （r2= 0.78, p 〈 0.05） and boron （r2 = 0.88, p 〈 0.05）. This indicates increasing contaminant concentrations while groundwater was depleting over the last eight years. Solubilization by complexation with Cl, CO3 and/or organic chelates may account for the increasing concentration of some heavy metals when groundwater depletion occurs. These results are the first to link space-based groundwater mass change with groundwater contaminant concentration change.
