再生水灌溉农田土壤镉累积规律模拟研究

我国农田土壤重金属污染情况严重,主要来源包括由污水灌溉、施肥和大气沉降等.由于这一过程具有小剂量长期性的特点,模型的应用相对常规检测手段能够更好地探索土壤重金属污染趋势和风险.基于STEM-profile模型,结合北京市通州凉水河农田区的实地检测,对该地区重金属Cd污染趋势进行了预测.结果表明,模型模拟结果与实测结果拟合较好,在持续现有输入的情况下,100 a之后该地区的土壤Cd污染将会超出国家土壤环境质量标准,耕作层中Cd含量达到0.866mg·kg-1.同时,通过对污染物的输入量与输入形态以及灌溉用水量对Cd的分布影响的分析发现,单独的有机肥施用和再生水灌溉均会导致Cd的累积,在地下水灌溉同时施用化肥的情况下不会造成Cd累积;当Cd的输入全部为有机结合态时,土壤耕作层中的Cd含量增加为0.943 mg·kg-1;在不改变由灌溉输入污染物的量的情况下,当灌溉量分别为0.8、1.5和2.0 ET时,土壤耕作层中金属镉的含量分别为0.952、0.784和0.638 mg·kg-1.

Modeling the Cd Accumulation in Agricultural Soil Irrigated with Reclaimed Water

Recent years, soil pollution of heavy metal has affected human life seriously, especially in farmland. Heavy metal pollution in farmland is mainly caused by irrigation, fertilizing and atmospheric fallout. As the character of heavy metal input in farmland is chronic and low dosage, application of model would be more suitable than routine methods to illustrate the dynamic changes of heavy metals in soil. In this paper, we use the model of STEM-profile to analyze and predict Cd pollution in farmland in Tongzhou, Beijing, based on the data from field survey. The results showed that: the concentration of Cd in this land would exceed the national soil environment standard after 100 years under current situations, reaching 0.866 mg·kg^-1 in plow layer. Studies of the influence of the amount and the form of inputs and the amount of irrigation water on the distribution of Cd in soil showed that irrigated with reclaimed water or fertilized with organic manure could lead to accumulation of Cd in the soil, while groundwater irrigation with inorganic fertilization would not cause accumulation of Cd in soil. When Cd inputs changed from mineral to organic form, the concentration of Cd in plow layer would be 0.943 mg·kg^-1 after 100 year. When the amount of irrigation water increased from 0.8 ET to 1.5 ET and to 2.0 ET, the plow layer Cd content would be 0.952, 0.784 and 0.638 mg·kg^-1respectively.