膨润土中硫酸盐还原菌对As和N的还原作用

Bio-reduction of arsenic and nitrogen by sulfate-reducing bacteria in bentonite

通过微宇宙实验,探究厌氧条件下不同硫酸盐还原菌(Desulfovibrio vlugaris Miyazaki,SRB)活性、外源氮添加量和有机物对膨润土固-液体系中砷(As)和氮(N)形态及浓度的影响,以及二者间的联系。结果表明:与超纯水环境相比,在适宜SRB生长的标准培养液中,As(Ⅴ)从第0天就开始还原成As(Ⅲ),在第7天时As(Ⅲ)达到1 947μg·L^(-1),明显高于超纯水环境中的As(Ⅲ)浓度(1 341μg·L^(-1))。同时,生物还原作用下3种不同细菌生长环境中的NO^(-)_(2)和NH^(+)_(4)都有升高的趋势。在没有外源N添加的控制组,几乎检测不到As(Ⅲ),而在低氮和高氮两种N水平的实验组中,As(Ⅲ)浓度分别高达427μg·L^(-1)和1 341μg·L^(-1),成铵作用和反硝化作用随着N源的输入也变得明显。高低两种水平乙酸钠的添加极大地提高了As(Ⅴ)的还原量,得到的平均As(Ⅲ)浓度分别为控制组的2.0倍和2.5倍。但腐植酸的加入使得As(Ⅴ)还原量减少。进一步实验探究NO^(-)_(2)和As(Ⅲ)的关系,其实验结果显示:亚硝酸钠直接加入As(Ⅴ)溶液共存体系后,可在5 h内将As(Ⅲ)的浓度由低于检测范围提高至14.6μg·L^(-1),因此NO^(-)_(2)可以作为反应中的电子供体,直接参与As(Ⅴ)还原反应。

This paper investigates the effects of the sulfate-reducing bacteria(SRB),Desulfovibrio vulgaris Miyazaki,exogenous N addition amount,and organic matter on the species and concentration of arsenic(As)and nitrogen(N)molecules in the bentonite solid-liquid system under anaerobic conditions,as well as the relationship between them through microcosmic experiments.The results showed that As(Ⅴ)was reduced to As(Ⅲ)from day zero,reaching 1947μg·L^(-1) on day seven,in the standard culture medium suitable for SRB growth.This is markedly higher than As(Ⅲ)concentration(1341μg·L^(-1))in ultra-pure water.Biological reduction increased NO^(-)_(2) and NH^(+)_(4) in three different bacterial growth conditions.In the control group without nitrogen addition,As(Ⅲ)was almost undetectable.However,in the experimental groups with low and high nitrogen levels,As(Ⅲ)concentrations were 427μg·L^(-1) and 1341μg·L^(-1),respectively,and ammonium formation and denitrification was evident with the addition of nitrogen.The addition of high and low levels of sodium acetate markedly increased the amount of As(Ⅴ)available for reduction.The average As(Ⅲ)concentrations obtained were 2.0 and 2.5 times higher than those of the control group,respectively.However,the addition of humic acid increased the amount of As(Ⅴ)being reduced.Further experiments to explore the relationship between NO^(-)_(2) and As(Ⅲ)show that the concentration of As(Ⅲ)can be increased from below the detection range to 14.6μg·L^(-1) within 5 hours after sodium nitrite is directly added to As(Ⅴ)solution coexistence system,therefore NO^(-)_(2) can serve as an electron donor in the reaction and directly participate in As(Ⅴ)reduction reaction.