水分管理对污染土壤中砷锑形态及有效性的影响

Influence of Wetting-Drying and Flooding Water Managements on Forms and Availability of Arsenic and Antimony in Polluted Soils

结合传统的化学消化法、原位微束X射线荧光扫描图谱(μ-XRF)和微束X射线近边结构分析(μ-XANES)等技术,分析了湖南锡矿山地区高砷(As)/锑(Sb)污染土壤中As和Sb的形态;结合室内培养和传统离位化学提取法研究了淹水和干湿交替处理对该土壤As和Sb形态及有效性的影响,并对其作用机制进行了阐述。结果表明:供试污染土壤中As主要以As(Ⅴ)价态存在,且土壤中As的元素分布与铁(Fe)、钙(Ca)、硫(S)的分布呈显著正相关(相关系数r分别为0.15、0.32、0.38,P<0.05);与干湿交替处理相比,淹水处理使得土壤溶液中As和Sb浓度分别提高了71.7%~4409%和3.53%~77.1%;土壤中无定形铁氧化物含量增加了13.8%,Fe结合态As和Sb含量分别增加了17.6%和32.33%,无定形铁氧化物含量与Fe结合态As和Sb含量呈显著正相关(决定系数r2分别为0.75、0.70,P<0.05)。尽管淹水处理下土壤中无定形氧化铁对As和Sb有较强的吸附作用,能增加As和Sb的固定,但铁锰氧化物的还原溶解而释放As、Sb对土壤溶液中As、Sb的含量影响更大,因此淹水较干湿交替提高了As、Sb的移动性和有效性。

Xikuangshan is the world′s largest antimony(Sb)mine and the surrounding soils are heavily contaminated with Sb, usually along with arsenic(As) as an associated pollutant. In this study, traditional chemical extraction methods and in-situ synchrotron-based tech-niques such as μ-XRF and μ-XANES were used to reveal forms and availability of As and Sb in the soil from Xikuangshan area. An indoor experiment was also conducted to investigate the effects of water managements(flooding and wetting-drying)on forms and availability of As and Sb. μ-XRF and μ-XANES analyses indicated that in the tested soil, arsenic mainly existed in penta-valent form and the As distribu-tion was significantly correlated with soil Fe, Ca, and S(correlation coefficients being 0.15, 0.32, and 0.38, respectively, P<0.05). Compared with alternative wetting-drying, flooding treatment resulted in a large amount of As and Sb release to soil solutions, with 71.7% ~4409% increase of As and 3.53% ~77.1% rise of Sb in the soil solutions, respectively. Furthermore, flooding treatment caused non-crystalline Fe oxides to increase by 13.8%, leading to increases in content of As and Sb associated with Fe oxides by 17.6% and 32.33%, respectively. A linear correlation was found of Fe-As and Fe-Sb with non-crystalline Fe oxides(r2=0.75 and r2=0.70, respectively, P<0.05),indicating a stronger influence of non-crystalline Fe oxides on As and Sb adsorption. Increased surface areas during transition from crystalline Fe oxides to non-crystalline Fe oxides promoted adsorption, and thus reduced the mobility and availability of As and Sb. However,enhancement of reductive dissolution of Fe/Mn oxides under flooding condition resulted in more As and Sb released to solution. Therefore,alternative wetting-drying treatment increased the adsorption and fixation of As and Sb, while flooding treatment generally increased their mobility and availability.