A GIS technology based potential eco-risk assessment of metals in urban soils in Beijing, China

Ecological risks of heavy metals in urban soils were evaluated using Beijing, China as an example. Cadmium, Cu, Zn, Pb, Cr and Ni contents of 233 surface soils sampled by 1 min latitude × 1 min longitude grid were used to identify their spatial distribution patterns and potential emission sources. Throughout the city, longer the duration of urbanization greater was the accumulations of heavy metals especially, Cd, Cu, Pb, and Zn. The soil Zn mainly came from the wears of vehicular tires. Point source emissions of heavy metals were few and far in the downwind south-east quadrant of Beijing. The calculated risk indices showed potential median eco-risks in the ancient central city. No potential high eco-risk due to soil-borne heavy metals was found. The potential medium eco-risk areas in Beijing would expand from the initial 24 to 110 km(2) if soil pH were to reduce by 0.5 units in anticipation.