冻融过程对铁磁性生物炭同步稳定化土壤镉砷效果的影响

Effect of freeze-thaw process on the synchronous stabilization of cadmium and arsenic in soil by ferromagnetic biochar

明确冻融过程对我国北方寒冷地区污染土壤重金属长期稳定化状态的影响是修复技术筛选的重要依据。本研究以多年原位重金属污染土壤为对象,针对Cd和As同步处理效果良好的富铁磁性生物炭(F-MBC),探究冻融过程中冻融频次与初始含水量对铁磁性生物炭同步稳定化土壤镉砷效果的影响。结果表明:随着冻融频次的增加,土壤pH和电导率呈先上升后下降的趋势,但均高于冻融前;同样冻融频次下,初始含水量的增加未对F-MBC处理土壤pH产生显著影响,但土壤电导率呈下降趋势。与冻融前相比,有效态Cd和As含量在冻融开始后经历了先上升后下降的过程,但均显著高于冻融前土壤;初始含水量增加导致土壤有效态Cd含量持续下降且显著低于未冻融对照,有效态As含量先上升后下降且高于未冻融对照。研究说明,经冻融过程后F-MBC仍可对Cd、As污染土壤实现同步稳定化修复,但As的污染再风险增加,为优化寒冷地区镉砷复合污染土壤的稳定化修复技术提供理论支持。

Understanding the impacts of freeze-thaw processes on the long-term stabilization of heavy metals in polluted soil in cold regions of northern China is an important basis for screening remediation techniques.In this study,we examined the effects of freeze-thaw frequency and water content on the synchronous stabilization of cadmium and arsenic in soil by ferromagnetic biochar(F-MBC)in the freeze-thaw process,taking the soil contaminated by in-situ heavy metals for many years as the object.The results showed that as the frequency of freeze-thaw increased,soil pH and electrical conductivity showed a trend of first increasing and then decreasing,but both were higher than that before freeze-thaw.Under the same freeze-thaw frequency,the increase in initial water content did not have a significant impact on soil pH under F-MBC treatment,but soil electrical conductivity showed a downward trend.Compared with those before freeze-thaw,the contents of available Cd and As in soil experienced a pattern of first increasing and then decreasing during the freeze-thaw process,but both were significantly higher than those before freeze-thaw in the soil.With the increases of initial water content,soil available Cd content continued to decrease and was significantly lower than that in the control(non-freeze-thaw).Available As content first increased and then decreased,and was higher than that in the control(non-freeze-thaw).Our results demonstrate that F-MBC can still achieve synchronous and stable remediation of Cd and As contaminated soil after the freeze-thaw process,but the risk of As pollution would increase.These results provide theoretical support for optimizing the stabilization and remediation technology of cadmium and arsenic composite contaminated soil in cold regions.