Research On Abiotic Methylation Of Mercury By Organic Complexs And Their Influencing Factors

Mercury is a global pollutant toxic, because of the long-range transport and volatile widely present in the environment.Environmental sources of mercury contamination are mining metallurgy, coal combustion, such as chlor-alkali industry and waste pile, mercury can build another more toxic mercury compound methylmercury through biological and non-biological way, methylmercury can enlarge enriched through the food chain and ultimately exist in vivo, methylmercury is highly lipophilic and neurotoxicity, would cause deadly harm to the organism, so for a and its compounds in the environment has been testing and source control become a hot issue of global concern. As a major mercury compounds with very low solubility, mercuric sulfide is widely present in the ore, sediment and soil. Methylmercury in the environment exists widely in water, soil and sea sediments, because these environments rich in a lot of organic matter and organic complexes, and therefore capable of generating mercury methylation of methylmercury by microorganisms and non-biological.Mercury migration and transformation of the complex has an important relationship with the complex, chelate, mercury and organic complexes to generate a new stable complex compound by the reaction process, the structure of some of the reducing group may thus effectively reducing the mercury hindered the rate of mercury methylation, with a certain sense of methylation of mercury.The main contents and results of the article are as follows:1. The experiment selected two inorganic mercury compounds HgCl2 and HgS to study the different effects of the complex process of methylation of mercury, because S2" in the mercury sulfide binding firm with mercury, therefore, it is widely found in water and sediment deposition matter rather easy migration. Due to the low solubility of mercuric sulfide, free state of the system and therefore generate less mercury ions is much smaller than the amount of methylmercury mercuric chloride. The results showed that the highest rate of methylation of mercury sulfide only 0.6%, while mercuric chloride reached 77.84%. Three complexes can be effective to promote solid mercuric sulfide dissolved sulfide of mercury methylation rates, three organic complexes affect the rate of non-biological methylation of HgS is L-cysteine> EDTA> citric acid.2.The experiment selected three different organic complexes of citric acid, EDTA, L-cysteine to investigate the effect of methylation of mercury.Experimental results showed that the type of organic complexes on the effects of mercury methylation differ. With the increase of the concentration of organic complexes, the amount of methylmercury reduce the concentration of the complex when 2mg·L-1 methylation rate of mercury is obvious, when the concentration of 10mg·L-1, the methylmercury the least amount. And three organic complexes because of their different with capacity for mercury methylation affect rate is L-cysteine> EDTA> citric acid. Compared to EDTA and L-cysteine, citric acid in the minimum, because EDTA is a very strong complexing agent effective, it is possible to generate a stable chelate compound with the mercury, and mercury aminoxatyl complex structure thiol group has a strong binding capacity, thus less mercury in the free state, effectively inhibited the rate of methylation of mercury.3. The influence of Fe (II) and organic complexes on abiotic mercury methylation rates. The results also proved that Fe (II) and three organic complexes can form a new organic complexes, and have varying degrees of impact on mercury methylation rates, the Fe (II) concentrations remain unchanged case, the complex Fe (II) with L-cysteine for the formation of the highest mercury reduction efficiency, the minimum amount of generated methylmercury, during the three kinds of Fe (II) complex condition, the generating of methylmercury are L-cysteine<EDTA<citric acid. Similarly, in the case of complexes of the same concentration, when the concentration of Fe (II) is higher, the smaller generation amount of methylmercury.4.The methylation of mercury has also received many environmental factors influence, the results show that the methylmercury generate under acidic conditions is significantly higher than amount of alkaline, under the pH of 3.0,5.0,7.0,9.0 solution system, when the pH is 3.0, has the highest rate of methylation of mercury, pH 9 is the least. Selected methyl cobalamin methyl donors and riboflavin in two different experiments methyl donor, since the methyl cobalamin methyl donor is most effective early reports of mercury methylation, the results show that under the conditions of methyl cobalamin methylation of mercury higher than riboflavin.S2- concentration will affect the rate of methylation HgCl2, and with the system S2- concentration increased, the less the amount of methylmercury generated.