Vulnerability of shallow ground water and drinking-water wells to nitrate in the United States: Model of predicted nitrate concentration in shallow, recently recharged ground water -- Input data set for population density (gwava-s_popd)
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This data set represents 1990 block group population density, in people per square kilometer, in the conterminous United States. The data set was used as an input...
本数据集涵盖美国本土（conterminous United States）范围内1990年普查街区组（block group）的人口密度数据，统计单位为每平方公里人口数。该数据集曾作为输入数据用于……
