| Various land utilizations and enormous environmental pressures are characteristics of suburban. Fully studying on suburban soil and crops pollution is necessary for city management planning and city development. In this study,167suriace soil (0-20cm) and15crops located in suburban of Beijing between the fifth and sixth ring road were sampled based on the3km×3km grids. The purpose of our investigation is to reveal the accumulating characteristics of Arsenic in Beijing suburban soils and crops. Physicochemical properties including soil texture, soil organic matter and pH which influence the absorbability and the accumulation of soil heavy metal were analyzed. Results showed that:Soil texture of Beijing suburban is loam soil type, which is suitable for farming. Meanwhile Beijing suburban soil is alkaline soil. The mean of Mn, Cu, Zn, Cr, Ni, Co, As is471.99mg-kg-1,70.59mg-kg-1,61.37mg-kg-1,26.47mg-kg-1,25.48mg-kg-1,9.43mg-kg-1,7.11mg-kg-1respectively. Compared with their background values the minimum, median, maximum and mean of Cu, Zn, Cr were all higher, but the concentration of As, Ni, Co, Mn were not obvvously enrich compared with their background values. Relationship between heavy metal and physicochemical properties of soil showed that As, Ni, Co, Mn significantly positive correlate with clay and silt and negative correlate with sand. This suggests that As, Ni, Co, Mn, Fe may have a common source.Arsenic contents in suburban soils of Beijing ranged from2.89mg-kg-1to11.38mg-kg-1, with mean of7.11mg-kg-1. The means were at the range of the background values reported in late1990s. While each quintile value was lower than the soil background values reported in early1980s. Factor analysis suggested that Arsenic in Beijing suburban soil shared the same group as those elements coming from parent materials such as Co, Mn and Ni. The spatial distribution map using Kriging interpolation showed that Arsenic contents in north-west and east and south-east parts were higher than those in north-east and south-west parts. Those plots with contents in the highest25%were all located near pollution sources, while most of those in the lowest25%contents located far from pollution sources. Comparison of Arsenic contents in different land uses showed that human activities impacted the accumulation of Arsenic in soils. Inhabitation areas and agricultural fields had higher Arsenic contents than green lands and vacant lands. Pollution sources significantly impacted the accumulation of Arsenic in soils of inhabitation areas and green lands and vacant lands. Arsenic contents in soils near factories were significantly higher than those far from factories and traffic corridors. In all, the spatial distributions of Arsenic contents in soils in Beijing suburban were generally determined by the distributions of parent materials, while human activities increased the accumulation of Arsenic in soils to some degree.Arsenic contents in suburban crops of Beijing ranged from0.003mg-kg-1to0.21mg-kg-1(fresh weight), with mean of0.039mg-kg-1. In all of the samples, Arsenic was less than the Tolerance Limit of Arsenic in Foods for China (TLAFC) of0.5mg kg’1fresh weight. The TLAFC is the maximum permissible concentration of Arsenic in crops that would be consumed by people. Arsenic contents in leaf crops were significantly higher than root crops and fruit crops. The bioconcentration factor (BCF) of Arsenic in the different varieties of crops followed the trend:leafy crops> root crops> fruit crops. The relationship between Arsenic in crops, Arsenic in soils and BCF showed that Arsenic in crops positive correlate with BCF. The probabilistic incremental lifetime cancer risks (ILCRs) of local inhabitants posed by exposure to soil. Arsenic were acceptable, ILCRs accounting for rural residents, urbanresident, children were7.43×10-6,5.51x1O-6,3.04×10-6. |
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