Earth Surface Processes
MA Jian-hua, WANG Xiao-yun, HOU Qian, DUAN Hai-jing
Many studies have been undertaken on heavy metal pollution of surface dust or street dust in many cities, but very few studies have been done on the pollution and potential ecological risk of kindergarten dust. Thirty-one surface dust samples were collected from kindergartens in one of cities located in the east of Henan Province, China. Concentrations of Pb, Zn, Cr, Cu and Ni in the samples were determined using F-AAS (flame atomic absorption spectrophotometry). Pollution and potential ecological risk of heavy metals in the samples were discussed with geoaccmulation index (Igeo) and potential ecological risk index (RI) respectively. The results show that average concentrations of Zn, Pb, Cr, Cu and Ni in kindergarten dust in urban area of the city are 311.84, 256.15, 89.17, 52.47 and 40.79 mg/kg respectively, and 1.93, 2.13, 5.45, 1.90 and 0.98 times of the control samples respectively. The heavy metals can be classified into two groups: anthropogenic source metals and mixed source metals. The first group of metals, Pb, Zn, Cr and Cu, is mainly derived from urban industries, traffic, domestic wastes, religion activities etc; while the second group, Ni, is from both human activities and soil parent material around the city. All the samples are polluted by Pb seriously with the degrees above moderate level; most samples are polluted by Ni and Zn with the degrees of slight or moderate levels, while they are polluted by Cu and Cr with a degree of slight level. The levels of integrated ecological risks of heavy metals in urban kindergarten dust are all above the strong risk with the average RI of 78.87. Lead in dust is an uppermost factor of potential ecological risk, because the average Epb contributes 70.34% to RI. Applying the method of RI proposed by Hkanson in 1980 to estimate potential ecological risk of pollutants, the RI standards for different risk levels should be modified according to the pollutant numbers studied and their toxic-response factors.