Variations of soil phosphorus accumulation in Nanjing, China as affected by urban development

Human activities can affect the biogeochemical cycling of phosphorus substantially. However, the relationship between P accumulation and urban development process is largely unknown. This study investigated the influence of urban development on the P accumulation in urban and suburban soils, using Nanjing (China) as a case. Based on its urban development history, Nanjing was divided into suburban and urban area, and the urban area was subdivided into urban north and urban south. Soil total P (TP) and available P (AP) of 578 samples from 68 pedons at different locations were measured. Thickness-weighted mean P content of each pedon (P w ), P content of the surface soil layer (P s ), the highest P content of each pedon (P h ), and the lowest P content (P l ) of each pedon were selected as statistical indices. Compared with the background value, urban and suburban soils were enriched in P. The highest TP content was up to 11.14 g P kg -1 , and the highest AP content was up to 360 mg P kg -1 . However, analysis of variance (ANOVA) and multiple comparisons of P w, P s, P h, P l showed that urban south with longest residential history had the highest TP w, TP s TP h, and AP w, AP l contents, and urbanizing suburban had the lowest TP w and AP w, AP l contents. For both APs and AP h, there was no significant difference between suburban and urban area. However, significant differences between urban south and urban north were observed. The results demonstrated that urban development process, including population quantity and level of urban infrastructure, could influence soil P accumulation and distribution in urban environment. A more detailed assessment is required to avoid the potential secondary eutrophication caused by excess P release from those anthropogenic high-P soils.