Distribution of heavy metals and total petroleum hydrocarbons in soils near a petrochemical complex in Guangzhou, China
Li J.; Shim H.
Source PublicationHeavy Metal Sediments
PublisherNova Science Publishers, Inc.

The influence of an industrialized environment on the accumulation of heavy metals and total petroleum hydrocarbons (TPH) in agricultural soils as well as the mobility and availability of metals from soil to vegetation were investigated. Seventy soil samples collected from the soil surface layers and horizons of five selected pedons in the vicinity area of a petrochemical complex in Guangzhou, China were analyzed for Zn, Cu, Pb, Cd, Hg, and As and TPH concentrations. The levels of metals in vegetation (lettuce, scallion, celery, tomato, carambola, wampee, and longan) were also evaluated. The horizontal and vertical variations of metals and TPH were assessed and the geographical information system (GIS)-based mapping techniques were applied to generate the spatial distribution maps. Results showed that the mean concentrations of heavy metals in top soils did not exceed the maximum allowable concentrations for the agricultural soil of China, with the exception of Hg. Significant differences were found depending on the land-use type. The concentrations of Cu, Pb, Cd, Hg, and As for vegetable field and orchard were significantly higher than for woodland, showing the metal concentrations in top soils strongly influenced by agricultural practices and soil management, while the TPH concentration in top soils was in the reverse order compared to the soil metal concentrations, in the order of woodland> orchard> vegetable field, implying strong influences of storage tank and pipeline leakage, accidental spills, and improper waste disposal practices. The concentrations of Zn, Cu, Pb, Cd, Hg, and As in five pedons, particularly in cultivated vegetable field and orchard, decreased with the soil depth, indicating these elements mainly originated from the anthropogenic sources, while the vertical variation of TPH concentrations showed increasing with the depth. The spatial distribution maps further allowed the identification of hot-spot areas with high contaminant concentrations. In addition, the similar spatial distribution pattern among metals reflected the similar sources. In comparison to the spatial distribution of TPH, metals showed very different patterns, corresponding to the differences in land-use types and vertical variation tendency. The major sources of elevated metals and TPH concentrations in soils were human activities, with metals mainly from wastewater irrigation and intensive application of sewage sludge and various agricultural chemicals and TPH mainly from storage tank and pipeline leakage, accidental spills, and improper waste disposal practices. When the modified European Community Bureau of Reference (BCR) three-step sequential extraction procedure was applied to determine the concentration of metal fractions in soils, the distribution of Zn, Cu, Pb, and Cd in four fractions significantly varied among soil samples, and 18.8% and 5.8% of vegetable and fruit samples for Cd and Pb, respectively, exceeded the maximum permissible levels for food-crops in China. The soil-to-vegetation transfer coefficients were in the order of Cd> Zn> Cu> Hg> As> Pb, suggesting Cd being the most mobile and available to plants among those metals studied. The principal component analysis (PCA) indicated that metal fractions and soil physicochemical properties (pH, organic matter, cation exchange capacity, clay content, and electrical conductivity) affected the metal uptake by plants. Effective measures should be taken to avoid or minimize further heavy metal contamination of soils and to remediate the contaminated areas in order to prevent pollutants from affecting human health through the agricultural products.

KeywordBioavailability Guangzhou Heavy Metals Petrochemical Complex Spatial Distribution Tph
URLView the original
Fulltext Access
Document TypeBook chapter
AffiliationDepartment of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macau SAR, Macau
First Author AffilicationFaculty of Science and Technology
Recommended Citation
GB/T 7714
Li J.,Shim H.. Distribution of heavy metals and total petroleum hydrocarbons in soils near a petrochemical complex in Guangzhou, China:Nova Science Publishers, Inc.,2011:1-34.
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