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Ground-water quality with respect to nitrate, major inorganic constituents, pesticides, stable isotopes, and tritium was assessed in the agricultural Tangshan region in the Hai He River Basin of the People's Republic of China and compared with three similar regions in the United States: the Delmarva Peninsula of the states of Delaware, Maryland, and Virginia; and the San Joaquin and Sacramento Valleys of the state of California. These four regions are considered similar with respect to size, land use, or climate. Although the Tangshan region has been in agricultural production for a much longer time, probably several centuries, than the three regions of the United States, the widespread use of synthetic fertilizers and other soil amendments probably started at a similar time in all four regions. Median nitrate concentrations were found to be similar in the four regions in most instances, and those median concentrations were below the American nitrate drinking water standard of 10 milligrams per liter; however, higher concentrations, and a greater range of concentrations, were evident for the Tangshan region. In some water samples collected from a shallow aquifer in Tangshan, nitrate concentrations exceeded the Chinese standard of 20 milligrams per liter, whereas few comparative samples collected in the United States exceeded that standard. In Tangshan, recently recharged (early 1960s) water that was detected in wells drilled as deep as 150 meters was found to correlate with the elevated nitrate concentrations. Relatively low nitrate, which is indicative of natural water, was measured in older water of deeper wells. In addition to elevated nitrate concentrations, the agricultural area of the Tangshan region has been affected by an increase in the concentrations of total dissolved solids and iron. The increase in total dissolved solids of the Tangshan study unit could not be attributed to any one process. Increases in iron concentrations may be partly attributable to the widespread application of animal wastes and sewage as fertilizer, which could deplete oxygen concentrations in ground water and lead to dissolution of iron from various minerals. In contrast to the United States, pesticides were not detected in aquifers of the Tangshan region, which could be attributed to lower pesticide use in the People's Republic of China. Alternatively, pesticide use may be increasing in the People's Republic of China, but the pesticides would not yet have been detected in ground water because of the lag in travel time from soil horizons to the aquifer.

Comparative water-quality assessment of the Hai He River basin in the People's Republic of China and three similar basins in the United States