[Total contents of heavy metals and their chemical fractionation in agricultural soils at different locations of Beijing City].
In this study, 23 groups of suited typical soil-wheat grain samples were collected from different locations of Beijing city (central city, suburban plain and exurban plain), the accumulation, chemical forms and bioavailability of heavy metals in arable soils under different human activity intensity were analyzed, and their source identifications and health risk were discussed. The results showed that (1) Urban soils exhibited Pb contamination with an average concentration (35.59 mg x kg(-1)) above the WHO limit, probably due to the emission of traffic activities and industrial processes. In addition, long-term sewage irrigation and other agricultural activities led to local metal contamination in the suburban agricultural soils. (2) Cu, Zn and Pb were predominantly associated with the residual (35%-75%) and organic (23%-53%) fractions, followed by Fe/Mn oxide (1%-19%), and very small proportion of carbonate (n. d.-5%) and exchangeable (n. d.-2%) fraction. Furthermore, compared with the suburban agricultural soils, Pb, Zn and Cu in the urban agricultural soils showed higher mobility, whereas the exurban agricultural soils presented the lowest mobility. For Cd, the order was contrary. Besides, Cd showed the highest bioavailability among the four metals in suburban and exurban arable soils due to its considerable proportion of exchangeable (13% -31%) and carbonate fractions (11%-27%). (3) Cd and Zn contents in wheat grains were largely dependent on the Fe/Mn ox. fractions in the studied soils (P < 0.05, r were 0.43-0.7). (4) Pb and Zn concentrations in wheat grains in some of the urban and suburban agricultural soils were above the standard limit, which might bring potential risk for the health of the local residents.
Institute of Resources and Environment, Henan University, Kaifeng 475004, China. pingfan0604@yahoo.cn
Zhi-Fan
ZF
Chen
Ye
Y
Zhao
Ting-Zhong
TZ
Guo
Shui-Feng
SF
Wang
Qing
Q
Tian
D005591:Chemical Fractionation; D002681:China; D002947:Cities; D018556:Crops, Agricultural / Q000254:growth & development; D004784:Environmental Monitoring; D019216:Metals, Heavy / Q000032:analysis* / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*
D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants