Spatial distribution and risk assessment of phosphorus loss potential in urban–suburban soil of Lishui, China

Urban and suburban soil phosphorus (P) pools have a great impact on environmental quality. There is a critical need for a practical indicator of the potential for P movement from urban and suburban soil to surface waters. A total of 126 surface soil samples were collected from urban and suburban areas of a typical developing city (Lishui, China). The different P extraction solutions were used to predict P loss potential from the soil. For total P, over 50% of the samples were higher than the background value (661 mg kg− 1). For Olsen-P, 78.4% samples were above a recommended optimum value for plant growth (20 mg kg− 1). These results indicated an enrichment of P in urban and suburban soil, which could be attributed to anthropogenic sources. A split-line model related environmentally important CaCl2‐extractable P (CaCl2‐P) to Olsen-P, and the Mehlich 3 degree of phosphorus saturation (DPSM3) was used to predict the threshold values for P release. The change points for Olsen-P and DPSM3 are 92 mg kg− 1 and 23.6%, respectively. The area of P loss risk index was mapped using the geographic information system (GIS) based on the risk classification. The spatial distribution map obtained clearly showed that the region of high P loss risk was mainly distributed in the old and central urban region and northeast edge of the studied area. A phosphorus loss indicator combined with GIS would be helpful for the city government to best predict and manage P loss in the course of urban sprawl.

► Significant P enrichment is found in the soils of the developing city of Lishui, China. ► Olsen-P and DPSM3 could be indicators of urban–suburban soil's P losses potential. ► Areas of Olsen-P > 92 mg kg− 1 or DPSM3 > 23.6% are critical P losses sources. ► City sprawl leads to high P losses risk in intensive human activities regions.