天津市郊不同利用方式农田土壤镉的累积特征及生态风险评估

Cadmium Accumulation Characteristics and Potential Ecological Risk Assessment in Suburban Farmland Soils of Tianjin

为揭示天津市郊不同土地利用方式下农田土壤镉的积累特征及其生态风险,对天津市郊西青、东丽、北辰和津南四区不同土地利用方式下的330个农田土壤样品中的Cd含量进行了分析测试。结果表明,天津市郊四区中土壤Cd含量范围在0.07-3.89 mg/kg,均值含量为0.33 mg/kg,高于天津土壤Cd背景水平,已经有明显的积累现象。四区不同土地利用类型中北辰所有土地利用类型中土壤Cd含量的变异系数普遍较小,为0.24-0.34,而东丽菜田、大田和津南菜田、园田土壤Cd含量变异系数较高,均在0.9以上,各样点之间土壤Cd含量变化较大。方差分析结果表明,不同区域内同一种土地利用类型下土壤Cd含量分布表现出较为明显的差异性,同一区域的不同土地利用类型下土壤Cd含量也具有一定程度的差异。采用Hakanson潜在生态危害指数法对四区不同土地利用类型下农田土壤Cd潜在生态危害进行计算,结果表明在全部监测点位中,有4%的监测点位处于轻微的潜在生态风险,36.3%的土壤Cd处于中等生态风险水平,而16.2%和15.9%的土壤Cd达到了强和很强的生态风险水平,7.6%则达到了极强的生态风险水平,应采取积极措施对强生态风险水平以上的农田土壤区域进行治理和修复。

In order to explore the accumulation characteristics and potential ecological risk assessment of soil cadmium in suburban farmland soils of Tianjin, cadmium contents of 330 soil samples collected from fields in four suburban areas of Tianjin were analyzed. Results showed that, in the four suburban areas, soil cadmium concentration was in the range of 0.07-3.89 mg/kg and was 0.33 mg/kg on average, indicating the soil was in an obvious cadmium accumulation degree. Soil cadmium variation coefficients in all the soil in Beichen area were in the range of 0.24-0.34. At the same time, the cadmium variation coefficients of vegetable field and dry land in Dongli and vegetable field and garden soil in Jinnan were higher than 0.9. Variance analysis showed that there was significant difference in the same land use type of different areas and different land use types of the same area. Hakanson potential ecological hazard index was used to calculate the potential ecological risk of different land use types in the four areas. In all the monitoring point, the results showed that 4%, 36.3%,16.2%, 15.9% and 7.6% of the sampling points were at the potential risk level of light ecological risk level, medium risk level, strong risk level, very strong risk and extremely high ecological risk, respectively. Active measures should be taken to control and remedy polluted soil in areas above the strong ecological risk level.