椭圆小球藻对水体汞光还原的影响
Effects of Chlorella ellipticus on the photoreduction of Hg2+ in water body
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摘要: 为明确椭圆小球藻对水体中Hg2+光还原反应的影响，采用室内模拟实验，以不同波长紫外灯及氙灯（可见光）为光源，探讨不同丰度活、死椭圆小球藻在各光照条件下对Hg2+光还原反应的影响及动力学特征.结果表明，当藻丰度为1×106 cells·mL-1时，在可见光照射下，活藻、死藻处理Hg0的释放量分别为3.733 ng、3.749 ng，Hg2+的还原率分别为18.66%、18.75%；在紫外光（UV）照射下，活藻、死藻处理Hg0的释放量最高为2.312 ng、2.373 ng，Hg2+的还原率最高为11.56%、11.86%.在可见光、UVA、UVB和黑暗条件下，当藻丰度为0 cells·mL-1时，Hg2+的还原率分别为21.45%、22.86%、26.75%、20.41%；随藻丰度的增加，Hg2+的还原率逐渐下降；当藻丰度为10×106 cells·mL-1时，活藻处理Hg2+的还原率分别降至17.70%、10.28%、9.962%、9.774%，死藻处理的降至18.15%、10.83%、10.77%、10.39%.可见，椭圆小球藻对Hg2+的光还原反应起抑制作用，藻丰度越高抑制作用越强烈；可见光对含藻处理Hg2+的光还原起主要作用，其次为紫外光.动力学研究表明，UV照射下椭圆小球藻对Hg2+光还原反应可用Langmuir-Hinshelwood模型进行描述，反应速率常数k为（0.6893—1.473）×10-4 ng·L-1·min-1，Langmuir吸附系数KL为（1.063—1.080）×10-2 L·ng-1.Abstract: Laboratory simulation experiments were conducted to investigate the effects of Chlorella elliptica on the photoreduction of Hg2+ in water body. Different wavelengths of ultraviolet (UV) lamp and xenon lamp (visible light) were used as light sources. Chemical kinetic characteristics were analyzed for the experiments using different concentrations of living/dead Chlorella elliptica and under various light conditions. The results indicated that when the abundance of algae was 1×106 cells·mL-1, the release of Hg0 from living and dead algae treatment were 3.733 ng and 3.749 ng, respectively. The reduction rates of Hg2+ were 18.66% and 18.75% for living and dead algae treatment under visible light irradiation, respectively. Under UV light irradiation, the flux of Hg0 from living and dead algae treatment were the highest at 2.312 ng and 2.373 ng respectively, and the highest reduction rates of Hg2+ were 11.56% and 11.86%, respectively. When the abundance of algae increased from 0 cells·mL-1 to 10×106 cells·mL-1, under the visible light, UVA, UVB and dark conditions, the reduction rates of Hg2+ contained with living algae decreased from 21.45%, 22.86%, 26.75%, and 20.41% to 17.70%, 10.28%, 9.962% and 9.774%, respectively. For the dead treatments, the reduction rates decreased from 21.45%, 22.86%, 26.75%, and 20.41% to 18.15%,10.83%, 10.77%, and 10.39%, respectively. Therefore, Chlorella elliptica inhibited the photoreduction of Hg2+ and the inhibition was increased with the increase of the abundance of algae. Visible light played a major role in the Hg2+ photoreduction contained with algae, followed by UV light. The kinetics of photoreduction of Hg2+ by Chlorella elliptica under UV irradiation can be described by the Langmuir-Hinshelwood model. The rate constant k and Langmuir adsorption coefficient KL were calculated to be (0.6893-1.473)×10-4 ng·L-1·min-1 and (1.063-1.080)×10-2 L·ng-1, respectively.
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Key words:
- Chlorella ellipticus /
- mercury /
- photoreduction /
- wavelength /
- ultraviolet light
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