淹水条件下硝酸根对土壤中砷溶出过程的影响与机制  

Effect and mechanism of nitrate on arsenic dissolution in flooding soil

作　　者：刘晓凯 顾雪元[1] LIU Xiaokai;GU Xueyuan(School of Environment,State Key Laboratory of Pollution Control and Resource Reuse,Nanjing University,Nanjing,210023,China)

机构地区：[1]南京大学环境学院,污染控制与资源化国家重点实验室,南京210023

出　　处：《环境化学》2023年第12期4205-4216,共12页Environmental Chemistry

基　　金：国家重点研发计划项目(2020YFC1807701);国家自然科学基金(42177188)资助.

摘　　要：本文通过对3种土壤投加低浓度(10 mmolL^(-1))或高浓度(100 mmol:L^(-1))的NO_(3)^(-),进行100d的淹水实验,探究厌氧条件下NO_(3)^(-) 对土壤中As溶出的影响.结果表明,NO_(3)^(-) 对土壤As溶出过程的影响与NO_(3)^(-)的还原过程相耦合,当NO_(3)^(-) 未消耗完全时,铁氧化物和As的还原溶出受到抑制;仅当NO_(3)^(-) 消耗完全时,铁氧化物才开始大量还原溶出.研究还观察到某些土壤溶液中残留的NO_(3)^(-) 还原产物可能会氧化溶出的Fe(Ⅱ),导致溶液中的Fe(Ⅱ)TFe远低于空白对照组,并同时抑制了As的溶出.如淳安土的低浓度NO_(3)^(-) 处理组的第60、80、100天样品中Fe(I)/TFe值分别为23.6%、44.4%、63.7%,远低于空白对照组,而此时As的溶出被推迟.随着铁氧化物的溶出,与铁氧化物相结合的As也开始溶出,但由于之前NO,抑制了固相上As(V)的还原,导致液相As(V)TAs值较高,且As(V)因受NO_(3)^(-) 的还原产物的影响而难以被还原.对于土壤固相,NO_(3)^(-) 降低了固相各组分的Fe(Ⅱ)或As(Ⅲ)含量,对于Fe或As固相分布的影响则与土壤种类和投加的NO_(3)^(-) 浓度有关.The effects of NO^(-)_(3)on As dissolution in soil under anoxic conditions were investigated by a 100-day flooding experiment at low(10 mmol·L^(-1))or high(100 mmol:L1)concentration of NO^(-)_(3)in three soils.The results showed that the dissolution of As was coupled with the reduction process of NOz.When NO^(-)_(3)was not completely consumed,it inhibited both the reduction of iron oxides and the dissolution of As.Only when NO^(-)_(3)was completely consumed,iron oxides began to be reduced and dissolved on a massive scale.In addition,the reduction products of NO^(-)_(3)in soil solution may also oxidize dissolved Fe(Ⅱ),resulting in a low Fe(Ⅱ)/TFe ratio in soil solution.For example,in the 1ow NO^(-)_(3)treatment of Chun'an soil,the Fe(Ⅱ)/TFe ratio was 23.6%,44.4%and 63.7%on the 60th,80th,and 100th day,respectively,much lower than those in the control group.The dissolution of As was also delayed during this period.With the dissolution of iron oxides,As bound to iron oxides began to dissolve.However,since NO^(-)_(3)had inhibited the reduction of As(V)in solid phase and the possible influence of the reduction products of NO^(-)_(3),a high As(V)/TAs ratio in the liquid was observed.Moreover,the effects of NO^(-)_(3)on the distribution ofFe or As in the solid phase was related to soil type and NO^(-)_(3)concentration.

关 键 词：硝酸根 砷 厌氧 还原 

分 类 号：X131.3[环境科学与工程—环境科学]