光照对近岸海水溶解气态汞产生的影响研究

发布时间：2018-03-15 03:20

本文选题：光照　切入点：近岸海水　出处：《中国海洋大学》2014年硕士论文　论文类型：学位论文

【摘要】：海洋在全球汞循环中发挥重要作用。汞的氧化还原作用是推动溶解性气态汞(DGM)产生和释放的重要过程。研究近岸表层海水中二价汞和零价汞之间相互转化的反应机制，有助于了解海洋释放对大气汞库的贡献。本文以青岛近海表层水为研究对象，研究了不同波长紫外光照下汞的还原反应和氧化还原总反应。通过测定溶解性气态汞和活性汞(RHg)的含量，探讨悬浮颗粒物(SPM)和微生物对还原反应、氧化还原总反应的影响。结果表明：还原反应： 1）近岸表层海水中DGM的释放量逐渐降低，累积释放量逐渐升高，升高速度越来越慢，最后接近稳定。UVA、UVB和黑暗条件下，还原反应在5个小时内基本完成，还原反应速率常数分别为0.983h-1、0.306h-1、0.174h-1。黑暗环境中，汞的还原反应仍旧进行。紫外光促进近岸表层海水中汞的还原反应，随着波长的增大，还原反应速率和释放量增大。 2）微生物和SPM对还原反应速率的影响：黑暗环境下，海水中SPM和微生物对还原反应速率的影响小。UVA光照下SPM和微生物对还原反应速率的影响显著。光致还原反应占66%，微生物使还原反应速率降低了22%，SPM则使还原速率提高了55%。UVB光照下SPM和微生物对还原反应速率的影响介于两者之间。光致还原反应占63%，微生物还原作用占4%，SPM使还原速率提高了32%左右。 3）水体理化性质、汞形态和含量的不同导致青岛近海和黄河口表层水中汞的还原反应存在明显差异。氧化还原反应： 1）Hg2+和Hg0的相互转化并不是简单的可逆反应，可能存在介于两者之间的中间产物。 2）微生物和SPM对近岸表层海水中氧化还原反应的影响：黑暗条件下，未知还原起主导作用，微生物抑制还原反应、促进氧化反应，SPM促进DGM的产生、抑制RHg的产生。UVA光照下，，微生物促进氧化还原反应，SPM抑制氧化还原反应。UVB光照下，微生物促进还原反应、抑制氧化反应，SPM抑制DGM的产生、促进RHg的产生。 3）自然光照条件下，近岸表层海水中DGM和RHg净含量分别在295pg/L-960pg/L和901pg/L-5912pg/L的范围内变化。DGM和RHg均随光照强度呈单峰变化，早晨、晚上含量低，中午达到峰值。DGM和RHg净含量在0.01水平上呈显著正相关性。不同波段的自然光中，DGM、RHg净含量与UVB之间的相关系数最大，与UVC的相关系数最小。
[Abstract]:Oceans play an important role in the global mercury cycle. Mercury oxidation reduction is promoting dissolved gaseous mercury (DGM) and an important process release. Reaction mechanism of mutual transformation between the two price of mercury in coastal seawater and mercury, are helpful to understand the contribution of gas mercury release marine base. This paper takes Qingdao coastal surface water as the research object, study the different wavelength UV light reduction reaction and oxidation reduction reaction. The total mercury determination of dissolved gaseous mercury (RHg) and the activity of mercury content of suspended particulate matter (SPM) and microbial reduction reaction, the influence of the redox reaction. The results showed that the total:
Reduction reaction:
1) the release amount of DGM in the coastal surface seawater decreased gradually, the cumulative release rate gradually increased, rising more slowly, and finally close to the stable.UVA, UVB and dark conditions, the basic completion of the reduction reaction in 5 hours, the reaction rate constants were 0.983h-1,0.306h-1,0.174h-1. in a dark environment, the reduction reaction of mercury is still carried out. Promote the UV reduction reaction of mercury in coastal seawater, with the increase of the wavelength, reaction rate and release amount increased.
2) effect of microbial and SPM on reaction rate: the dark environment, SPM and microbial in seawater affect the reduction reaction rate of small.UVA light SPM and microorganism had significant effects on the reaction rate. The photoreduction reaction accounted for 66%, the microbial reduction reaction rate decreased by 22%, the reduction rate of SPM improved 55%.UVB light SPM and microbial effect on reaction rate between the two. The photoreduction reaction accounted for 63%, accounted for 4% of microbial reduction, the reduction rate of SPM increased by about 32%.
3) the physical and chemical properties of the water body, the difference of mercury form and content lead to significant difference in the reduction of mercury in the surface water of the Qingdao and the Yellow River Estuary.
Redox reaction:
1) the mutual transformation of Hg2+ and Hg0 is not a simple reversible reaction, and there may be intermediate products between the two.
2) and microbial SPM reduction effect on oxidation in coastal seawater: dark conditions, unknown reduction plays a dominant role in microbial inhibition reaction, promote the oxidation of SPM, promote the production of DGM, inhibited the production of RHg.UVA light, promote microbial redox reaction, SPM inhibited the redox reaction of.UVB light under the illumination of the microbially mediated inhibition of oxidation reaction, reduction reaction, SPM inhibited the production of DGM, promote the production of RHg.
3) under natural light conditions, the net content of DGM and RHg in the coastal surface seawater were in the range of 295pg/L-960pg/L and 901pg/L-5912pg/L in the changes of.DGM and RHg decreased with the light intensity showed a unimodal curve, morning and evening peak at noon low content of.DGM and RHg net content showed a significant positive correlation at the level of 0.01 different bands. Natural light, DGM, the correlation coefficient between RHg net and the content of UVB maximum, minimum and the correlation coefficient of UVC.

【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P734.22

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