基于加速碳化的农田土壤重金属钝化长期稳定性评估

Long Term Stability Assessment of Heavy Metal Passivation in Farmland Soil Based on Accelerated Carbonation

土壤重金属污染已严重影响我国农田安全利用及人体健康,农田重金属污染治理已成为亟须解决的重大环境问题。采用土壤修复工程中常用的无机修复药剂熟石灰、硫化钠和磷酸氢二钾对铜锌铅镉复合污染土壤进行钝化处理,通过加速碳化试验,考察了二氧化碳对常用无机药剂钝化铜、锌、铅、镉等重金属的长期稳定性的影响。结果表明,在不考虑碳化作用的情况下,添加上述3种无机修复药剂可大幅降低受污染农田土壤浸出液中重金属的含量,降低重金属污染风险。经加速碳化后,熟石灰处理的浸出液中,铜、镉的含量显著升高,铅、锌的含量基本不变;硫化钠处理的浸出液中,铜、锌、铅和镉的含量均出现一定程度的升高;磷酸氢二钾处理的浸出液中,铜、铅的含量基本不变,锌的含量出现轻微下降,镉的含量出现轻微上升。在采用钝化技术实施土壤重金属污染修复工程时,除了需根据重金属类型选择合适添加量的药剂外,还应结合加速碳化试验,明确污染因子在碳化作用下的稳定性变化情况,以保证修复效果。

Soil heavy metal pollution has seriously affected the safe utilization of farmland and human health in China,and the control of heavy metal pollution in farmland has also become a major environmental problem that needs to be solved.The commonly used inorganic remediation agents in soil remediation engineering,such as hydrated lime,sodium sulfide,and potassium hydrogen phosphate,are used to passivate copper zinc lead cadmium contaminated soil.Through accelerated carbonation tests,the effect of carbon dioxide on the long-term stability of commonly used inorganic agents in passivating heavy metals such as copper,zinc,lead,and cadmium is investigated.The results indicate that,without considering carbonation,the addition of the three inorganic remediation agents mentioned above can significantly reduce the content of heavy metals in the leachate of contaminated farmland soil and lower the risk of heavy metal pollution.After accelerated carbonation,the contents of copper and cadmium in the leachate treated with hydrated lime significantly increased,while the contents of lead and zinc unchanged.In the leachate treated with sodium sulfide,the contents of copper,zinc,lead,and cadmium all showed a certain degree of increase.In the leachate treated with potassium hydrogen phosphate,the contents of copper and lead remain unchanged,and the content of zinc slightly decreased and the content of cadmium slightly increased.When implementing soil heavy metal pollution remediation projects using passivation technology,in addition to selecting appropriate amounts of remediation agents based on the type of heavy metal,accelerated carbonation tests should also be combined in order to clarify the stability changes of pollution factors under carbonation,and ensure the remediation effect.