摘要
全球农业土壤普遍面临镉(Cd)与砷(As)两类典型重金属的复合污染挑战。由于Cd通常以可移动阳离子(Cd2+)存在,而As以含氧阴离子(H_(2)AsO_(4)^(−)或HAsO_(4)^(2−))形态存在,两者截然相反的化学行为使得传统单一污染修复策略在应对Cd-As复合污染时效率低下。为解决这一关键技术瓶颈,提出并验证了“微生物诱导缓释铁磷协同稳定化”新策略。首先利用土著溶磷菌(PSB)高效活化土壤顽固态磷库,72 h内生成50 mg/L的有效磷(AP),进而与Cd形成稳定磷酸镉沉淀固定镉;同时,通过零价铁(ZVI)的缓释氧化作用持续提供Fe^(2+),处理24 h后,生物有效态Fe^(2+)含量显著提升342.7%,促进砷酸铁矿物形成并增强铁氧化物对砷的吸附,从而实现砷固定。双路径协同机制在15 d的处理周期内展现了高效性,环境有效态Cd和As的稳定率分别达83.8%和68.1%,且两者均显著向高度稳定的残渣态转化,占比分别提升至总Cd的88.9%(提升19.3个百分点)和总As的72.5%(提升17.9个百分点),这种转化主要源于原本结合在无定形和晶质铁铝氧化物上的金属向残渣态的迁移。机制研究表明,Fe^(2+)可显著刺激(p<0.01)溶磷功能基因的表达,微生物介导的AP浓度也与矿化途径基因丰度显著相关(p<0.01),但低土壤pH环境(r=-0.68)会抑制磷活化。该技术通过定向调控功能微生物活性和强化铁磷循环协同转化,成功克服了单一稳定化材料修复复合污染效率低下的难题,为同步固定土壤中阴阳离子特性迥异的Cd和As提供了有效方案。
Agricultural soils worldwide face significant pollution challenges,among which cadmium(Cd)and arsenic(As)stand out as two of the most prevalent heavy metal contaminants.Remediating soils co-contaminated with both Cd and As presents a particularly formidable challenge due to the starkly contrasting chemical behaviours exhibited by these elements:Cd typically exists as a mobile cation(Cd2+),while As commonly occurs as an oxyanion(e.g.,H_(2)AsO_(4)^(−)or HAsO_(4)^(2−)).This inherent chemical divergence renders conventional remediation strategies,often designed for single contaminants,largely ineffective or inefficient when addressing their combined presence.To overcome this critical technical bottleneck,this study introduces and validates a novel remediation concept termed"microbial-induced slow-release iron-phosphorus synergistic stabilisation".The core premise leverages biological and chemical processes to concurrently immobilise both cationic Cd and anionic As within the soil matrix.The approach strategically employs indigenous phosphate-solubilising bacteria(PSB)as a key biological driver.These microorganisms act upon endogenous,recalcitrant phosphorus pools naturally present in the soil,converting them into plant-available phosphorus(AP).This solubilisation process proved highly efficient,achieving a dissolved AP concentration of 50 mg/L within a 72-hour period.The newly liberated AP facilitates the formation of insoluble,stable Cd-phosphate complexes,thereby effectively immobilizing cadmium.Concurrently,the remediation strategy integrates zero-valent iron(ZVI)coupled with a controlled slow-oxidation mechanism.This designed process enables the sustained release of Fe^(2+)ions over time.The impact of this Fe^(2+)release is substantial and rapid,inducing a remarkable 342.7%increase in bioavailable ferrous iron content within the first 24 h of treatment.This surge in Fe^(2+)is crucial for arsenic fixation,primarily by promoting the formation of arsenic-bearing iron oxide minerals(e.g.,ferric arsenates)and enhancing arsenic adsorption onto the surfaces of newly formed or existing iron oxides.This dual-pronged approach synergistically addresses the immobilisation needs of both contaminants through distinct chemical pathways.The efficacy of this synergistic stabilisation technology was rigorously assessed over a reaction period of 15 d.The results demonstrate high immobilization efficiencies:the stabilisation rates for the environmentally available(labile)fractions of Cd and As reaches 83.8%and 68.1%,respectively.Subsequent chemical fractionation analysis reveals a profound transformation in the speciation of the heavy metals post-remediation.Both Cd and As are predominantly converted into the highly stable residual forms,representing 88.9%of total Cd and 72.5%of total As.These percentages signify significant increases of 19.3 and 17.9 percentage points,respectively,compared to their initial levels before treatment.This conversion predominantly results from the transformation of metals previously bound in less stable forms,specifically those associated with amorphous iron-aluminium oxides and crystalline iron-aluminium oxides,into the stable residual phases.Mechanistic investigation into the iron-phosphorus coupling interactions provides further critical insights.Statistical analysis reveals that the presence of Fe^(2+)exerts a significant stimulatory effect(p<0.01)on the expression or activity of functional phosphate-solubilising genes within the microbial community.Furthermore,the concentration of microbially generated AP is found to be significantly correlated(p<0.01)with the abundance or activity of genes involved in mineralisation pathways.It is noteworthy,however,that a low soil pH environment(correlation coefficient r=-0.68)is identified as an inhibitory factor for the phosphorus activation process.In summary,this technology successfully overcomes the problem of low efficiency in repairing complex pollution using a single stabilising material by directingly regulating the activity of functional microorganisms and strengthening the synergistic conversion of iron-phosphorus cycles,providing an effective solution for simultaneously fixing Cd and As,which have vastly different cation and anion characteristics,in soil.
作者
李琦
李嘉欣
司梦莹
廖骐
杨志辉
胡晓先
杨卫春
LI Qi;LI Jiaxin;SI Mengying;LIAO Qi;YANG Zhihui;HU Xiaoxian;YANG Weichun(School of Metallurgy and Environment,Central South University,Changsha 410083,China;Chinese National Engineering Research Center for Control&Treatment of Heavy Metal Pollution,Changsha 410083,China;Henan Key Laboratory of Water Pollution Control and Rehabilitation Technology,Henan University of Urban Construction,Pingdingshan 467036,Henan,China)
出处
《有色金属(冶炼部分)》
北大核心
2025年第10期112-119,共8页
Nonferrous Metals(Extractive Metallurgy)
基金
湖南省自然科学基金资助项目(2023JJ10065)
国家自然科学基金重大项目(22494684)
河南省科技攻关项目(242102321078)。
关键词
镉和砷
解磷菌
缓释铁磷
协同稳定化
cadmium and arsenic
dephosphorylating bacteria
slow-release iron phosphorus
synergistic stabilization
