Nitrate-Dominated Multi-Receptor Environmental Risks and PMF Source Apportionment in Shallow and Deep Groundwater of the Baiyangdian Lake Basin, North China Plain: Implications for Multi-Scale Management

Groundwater is the main source of drinking, irrigation, and ecological water in the Baiyangdian Lake Basin (BLB), but growing human activity has raised concerns about its quality. This study assesses major ion geochemistry and multi-receptor environmental risks across the BLB using 1113 groundwater samples (983 shallow, 130 deep). Risks to drinking water supply, agricultural irrigation, and wetland health are evaluated within a single framework, and Positive Matrix Factorization (PMF) is used for quantitative source apportionment. Shallow groundwater shows markedly higher dissolved solids and nitrate than deep groundwater, with 20.7% of shallow samples exceeding the WHO nitrate guideline. Multi-receptor assessment finds that 41.2% of shallow wells pose risk to at least one endpoint and 12.5% to two or more simultaneously. PMF identifies three sources—geogenic weathering, agricultural nitrate, and wastewater discharge—with nitrate as the largest single contributor to water quality impairment. The findings point to an urgent need for targeted agricultural non-point source control and provide a basis for nested, multi-scale groundwater management in the BLB and similar intensively exploited alluvial aquifers.