珠三角土壤镉含量时空分布及风险管理

Prediction and Risk Management on Geochemical Accumulation of Soil Cadmium based on Time-Space Model in Zhujiang River Delta

基于珠三角地区98个同点位土样,探讨了土壤Cd含量的时空分布特征及风险管理策略。研究表明,两批次土壤Cd含量富集程度均很高,土壤Cd平均含量Cˉ2001和Cˉ2007均为0.28 mg/kg,是广东省土壤背景值的5倍;两者均值多重比较表明,Cd的均值变化达到显著水平。土壤Cd的变异系数分别为0.83和0.72,暗示了Cd主要来源于人为成因。经估算,土壤Cd区域性年均累积速率KC2007-C2001、KC2012-C2007分别为0.016和0.014 mg/kg。采用"时空模式"和"空时模式"模型预测土壤Cd含量的时空分布态势,在时间序列资料较少的情形下,"时空模式"预测结果较稳健。2020年研究区大部分区域土壤Cd有污染,未来的风险管理应对无污染区域采取预防策略;对有污染区域采取控制策略;对重污染区域采取修复策略。

In order to measure the contents of Cadmium （Cd）, 98 topsoil samples were collected from the same points of the Zhujiang River Delta in the years of 2001 and 2007, respectively. Based on 98 soil samples, the spatial and temporal distribution of soil Cadmium concentrations was explored, in which risk management strategies were discussed. The results showed that the extent of soil Cadmium was highly enriched, the mean concentrations of soil Cadmium in the two periods was 0.28 mg/kg, which was 5 times more than its soil back- ground values of Guangdong Province （0.06 mg/kg）; Both mean values for multiple comparisons showed that the Cadmium mean change reached a significant level. The coefficients of variation of soil Cadmium were 0.83 and 0.72, respectively, which indicated that the Cadmium sources were mainly from anthropogenic activi- ty. Based on the model of Soil heavy metal accumulation rate of two periods, the annual regional soil Cadmi- um accumulation rates from 2001 to 2007 were 0.016 mg/kg, while from 2007 to 2012 the average annual re- gional soil Cadmium accumulation rate was 0.014 mg/kg. The temporal and spatial distribution trend of soil Cadmium is predicted, using two models, namely time-space mode and space-time mode. In the case of less time-series data, time-space mode is more robust predictions. Soil in most of area will be contaminated by Cad- mium in 2020. Therefore, there are three strategies in future risk management： 1） to take preventive strategies in non-polluting area; 2） to take control strategies in the contaminated area; 3） to take repair strategies in heav- ily polluted area.