Spatial distribution patterns of phosphorus in top-soils in London urban area

The spatial distribution patterns of phosphorus (P) concentration in soils of the London urban area was investigated based on 6467 samples from the London Earth soil geochemical survey of the Greater London area of British... [ view full abstract ]

The spatial distribution patterns of phosphorus (P) concentration in soils of the London urban area was investigated based on 6467 samples from the London Earth soil geochemical survey of the Greater London area of British Geological Survey. Both the results of analysis of variance (ANOVA) and GIS mapping implied that the P distribution showed a strong geogenic control with elevated concentrations in areas of alluvium and river terrace deposits. The P distribution demonstrated strong association with riverine areas, especially accumulated along the River Thames, the River Lea and the Grand Union Canal. However, the P concentrations decreased dramatically below Woolwich Reach of Thames estuary where the soils were gradually dominated by bed-load transport from the sea. Besides the natural control, P soil content was also strongly impacted by human activities, including three main types of sources: sewage treatment works (STWs), septic tanks and agriculture. The optimized hot spot analysis showed that two STWs, Beddington and Deephams, had high concentrations where water flows often exceeded the capacity of the treatment plants during heavy rain events. The patterns shown by cluster and outlier analysis matched well with London population density. Heathrow airport, Stockley and Bexley heath Golf Course showed high levels of P. The spatial patterns of P controlled by parent material (PM) have are still clearly seen even in the metropolitan urban area where anthropogenic activity is high. The identified P hotspots suggest places where attention needs to be paid to soil quality.
Key words: London; phosphorus; GIS; hotspots; sewage; Thames