沈抚灌区耕地重金属Cd、Pb的变化特征分析

Analysis on the variation character of heavy metals Cd and Pb in the cultivated land of Shenfu sewage irrigation district

选择沈抚灌区东部13个自然村庄的农业种植区,以1500 m间距网格化布点29处,调查研究区历史耕作情况,选取18个停灌时间不同的耕地样点,每个样点按0~20、20~40、40~60 cm采集3层土壤样品,分析测定重金属Cd、Pb的全量及化学形态,并测定了地上作物的茎叶、籽粒中重金属含量,探究研究区不同停灌时间及利用类型耕地土壤中Cd、Pb的分布特征及变化规律。结果表明:0~20、20~40、40~60 cm土壤中Cd含量分别为0.65~1.57、0.66~1.18、0.61~1.18 mg·kg^-1,停灌20~25年的土壤0~20 cm土层Cd含量最高,为1.57 mg·kg^-1;各土层Pb变化范围分别为21.07~38.59、14.97~30.59、15.71~25.66 mg·kg^-1,未随停灌时间发生明显变化;Cd在20~40、40~60 cm土层迁移率分别为0.42~0.50、0.46~0.52,而Pb仅为0~0.34、0~0.68;玉米茎叶、籽粒中Cd含量分别为0.33~0.47、0.02~0.07 mg·kg^-1,水稻茎叶、籽粒中Cd含量分别为0.33~0.89、0.02~0.09 mg·kg^-1,Pb含量分别为1.51~2.32、0.47~0.62mg·kg^-1,Cd、Pb在作物茎叶、籽粒中未随不同耕作方式及停灌时间表现出明显差异;水田土壤可交换态Cd含量占总量的37.33%,旱田可交换态Cd含量占总量的7.82%~13.95%;水田土壤可交换态Pb含量占总量的9.03%,旱田占总量的0.87%~4.18%。研究结果可为重金属污染耕地的利用管理及污染修复提供依据。

In selected farmland, including 13 natural villages, in the eastern part of the Shenfu sewage irrigation district, twenty-nine 1500 m squares were gridded, and historical farming in the study area was investigated. Furthermore, 18 soil sampling points with different irrigation times were selected. Here, soil samples were collected from 0~20, 20~40 cm and 40~60 cm depth. To study the distribution characteristics and the variations of soil Cd and Pb in the study area for different irrigation stop times and different types of farmland, the total amount and chemical forms of Cd and Pb were analyzed, and the content of heavy metals in the stems or leaves and seeds of the ground crops was also determined. The results showed that the content of Cd in the soils of 0~20, 20~40 cm, and 40~60 cm was 0.65~1.57, 0.66~1.18 mg·kg^-1, and 0.61~1.18 mg·kg^-1, respectively. The soil Cd at 0~20 cm reached a maximum of 1.57 mg·kg^-1 at 20~25 years of irrigation stop time. The range of soil Pb in the three soil layers was 21.07~38.59, 14.97~30.59 mg·kg^-1, and 15.71~25.66 mg·kg^-1, which changed less with the irrigation stop time. The migration rate of Cd between the soil layers was 0.42~0.50 and 0.46~0.52, and Pb was 0~0.34 and 0~0.68. The range of Cd content in maize stems or leaves and seeds was 0.33~0.47 mg·kg^-1 and 0.02~0.07 mg·kg^-1, respectively,which was significantly lower than that in rice stems or leaves and seeds, at 0.33~0.89 mg·kg^-1 and 0.02~0.09 mg·kg^-1, respectively. There was no significant difference in Cd or Pb content under different irrigation times. The proportion of exchangeable Cd in total Cd in paddy farmland was 37.33%, and the exchangeable Cd in total Cd in dry farmland was 7.82%~13.95%. The exchangeable Pb content in paddy farmland was 9.03% of the total amount, and for dry farmland was 0.87%~4.18%. The results can help in the use, management, and restoration of farmland that has been contaminated by heavy metals.