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为研究硝酸根(NO3-)对水体中甲基汞(MMHg)光化学降解的影响,采用室内模拟试验,验证了不同波长光照条件下,NO3-在MMHg光化学反应中的作用,探讨了NO3-浓度对MMHg光解速率及产物的影响,并根据溶液中Hg2+的浓度分析了MMHg光解反应的进行程度.结果表明,在自然光(NL)和紫外光(UV)条件下,只加入了NO3-的处理MMHg光降解速率分别为0.10、0.046 L.(ng·h)-1,Hg0的释放通量分别为1.05、1.27 ng,Hg2+的最终浓度分别为16.97、28.92 ng·L-1;在未加入NO3-和加入了C6H5COOH的条件下,MMHg的剩余浓度相差不大,其光降解速率也分别在0.052、0.015 L.(ng·h)-1左右,Hg0的释放通量分别为23.81、15.38 ng,Hg2+的浓度均小于10 ng·L-1,且呈现先增加后减小趋势.在可见光(VL)照射下,各处理下MMHg的光降解速率无显著性差异(P=0.56),为0.003 L.(ng·h)-1左右,Hg0的释放通量均为5 ng左右,Hg2+的浓度未超过3 ng·L-1,也呈现出先增加后减小的趋势.在NL条件下,随浓度NO3-的增加,MMHg的光降解速率也增加,且各处理间存在显著性差异(P<0.05),Hg0的生成量随NO3-浓度的增加而减少,而Hg2+的浓度也随NO3-浓度的增加而增加.可见在有紫外光的条件下,NO3-对MMHg光降解反应历程、反应速率以及产物有重要影响.
In order to study the effect of nitrate (NO3-) on the photochemical degradation of methylmercury (MMHg) in water, the effect of NO3- on the photochemical reaction of MMHg under different light conditions was verified by laboratory simulation. The effects of NO3- On the rate of photodegradation of MMHg and its products, and according to the concentration of Hg2 + in the solution, the degree of photodegradation of MMHg was analyzed. The results showed that under the conditions of natural light (UV) and UV light, NO3- The photodegradation rates of MMHg were 0.10,0.046 L. (ng · h) -1, the release fluxes of Hg0 were 1.05 and 1.27 ng, respectively. The final concentrations of Hg2 + were 16.97 and 28.92 ng · L-1, respectively. Under the condition of adding NO3- and C6H5COOH, the residual concentrations of MMHg were similar and their photodegradation rates were about 0.052,0.015 L. (ng · h) -1 respectively. The release fluxes of Hg0 were 23.81 and 15.38 ng , And Hg2 + concentrations were all less than 10 ng · L-1, and then increased firstly and then decreased.The photodegradation rate of MMHg under each treatment showed no significant difference (P = 0.56) under the visible light (VL) irradiation, which was 0.003 L (ng · h) -1, the releasing flux of Hg0 was about 5 ng and the concentration of Hg2 + did not exceed 3 ng · L-1, which also increased first and then decreased Under the condition of NL, the photodegradation rate of MMHg also increased with the increase of NO3- concentration, and there was a significant difference among treatments (P <0.05). The amount of Hg0 decreased with the increase of NO3- concentration The concentration of Hg2 + also increased with the increase of NO3- concentration, which shows that under the condition of UV light, NO3- has an important influence on the photodegradation process of MMHg, the reaction rate and the product.