Experiences from phasing out the use of mercury in Sweden

The Swedish parliament has decided that the use of mercury (Hg) in society should be phased out by the target year 2000 and substituted with alternative, less harmful elements or compounds. This is to reduce exposure to the toxic heavy metal, levels of which have increased two to seven times in the Swedish environment during the last century. Mercury in products and goods in use in Sweden has been estimated at 100 tonnes Hg, which will slowly be released into the environment if no preventative measures are taken. To avoid handing over unsolved environmental problems and connected costs to future generations, the Swedish government commissioned the Swedish Environmental Protection Agency (EPA) to improve the efficiency of Hg collection and to find a solution for terminal storage of the waste. The result is that the Swedish EPA considers deep storage in rock, accompanied by technical measures to further reduce the risk of future Hg emissions to be the safest method. It has funded approximately 50 projects with the goal of spreading information about the Hg problem and removing Hg from society. The projects have focused on areas where there is a great risk of Hg in products and goods entering the environment. About 6 tonnes Hg has so far been collected in these projects – end of 1999 – and the cost of the Hg collected has varied between 70 and 1300 US$ kg^–1 Hg. The projects were more cost-effective than traditional inspection by an official due to local participation, use of Hg-tracker dogs, and employment of professional electricians in the search for Hg. The involvement of school children and the public has resulted in an increased awareness of environmental matters, and, together with the emptying of water seals, reduced Hg levels in municipal sewage sludge. Electronic Publication     

Effects of sulfate-reducing bacteria on methylmercury at the sediment–water interface

Sediment cores(containing sediment and overlying water) from Baihua Reservoir(SW China)were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria(SRB) on mercury(Hg) methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury(DMe Hg) in the overlying water of the control cores with bioactivity maintained(BAC) and cores with only sulfate-reducing bacteria inhibited(SRBI) and bacteria fully inhibited(BACI) were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations(r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively). The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster(hgc AB), besides SRB,causing Hg methylation in the sediment–water system.     

1株兼具好、厌氧汞甲基化能力细菌的分离鉴定

从三峡水库重庆段忠县石宝寨消落带土壤中,分离纯化后获得1株在好氧和厌氧条件下均能将Hg2+转化成甲基汞的细菌,经过对该菌株的形态特征、理化特征检测及16S r DNA序列分析,初步鉴定其为γ-变形菌纲的荧光假单胞菌,并命名为Pseudomonas fluorescens XD-Me Hg-B2(Gen Bank登录号:KU954349).通过汞敏感性试验发现该菌对Hg2+极敏感,汞甲基化试验表明,在初始Hg2+浓度为200 ng·L-1的PBS缓冲液中,接种XD-Me Hg-B2对数生长期菌悬液,有氧条件下,30℃孵育60 min后,溶液中甲基汞浓度呈指数增高,并在160 min时达到最大,约为3.85 ng·L-1±0.33 ng·L-1,最大汞甲基化率为1.93%;而在厌氧条件下,XD-Me Hg-B2同样表现出汞甲基化能力,但其甲基汞的生成较好氧处理显著滞后,且汞甲基化转化率较低,在180min左右甲基汞浓度达到最大,为2.86 ng·L-1±0.73 ng·L-1,最大汞甲基化率为1.43%.综上所述,P.fluorescens XDMe Hg-B2是1株对Hg2+极敏感,兼具好、厌氧汞甲基化能力的细菌,可望为消落带土壤汞生物甲基化的机制研究提供候选菌株,从而为深入研究汞生物地球化学循环、以及正确评价三峡水库蓄水运行后可能带来的汞生态风险评价提供理论依据.     

土壤中总汞的不同测定方法对比分析研究

对土壤中总汞的两种不同测定方法进行了对比分析.通过方法检出限、精密度、准确度和加标回收率的对比,结果表明,水浴消解-原子荧光光谱法检出限为2.1 ng/g,精密度为2.52～4.63％,加标回收率介于94％～ 104％;汞分析仪直接测定法检出限为0.08 ng/g,精密度为2.89～ 5.61％,加标回收率介于90％～102％.相比水浴消解-原子荧光法,直接测定法操作更加简单、便捷,而且无繁琐的前处理环节,适于大批量土壤中总汞的分析测定,是一个比较理想的分析方法.     

全自动甲基汞分析仪测定水源水中甲基汞实验研究

建立了全自动甲基汞分析仪测定水源水中甲基汞的方法,过程简单,可获得较理想的结果.实验采用直接法测定水源水中的甲基汞含量,优化仪器分析条件;在0 ～1 000 pg的范围内,标准工作曲线线性良好;仪器检测限达到0.003 ng/L,低于水源水中限量要求;实际水样加标回收率在86.5％ ～935％之间;标准样品分析合格;测定标准样品的相对误差为1.4％;运用适当的质控手段,可较好的满足水源水中痕量甲基汞的测定需求.     

燃煤电厂非颗粒态汞的捕集技术概述

基于燃煤电厂现有设备,根据不同形态汞的特殊物化性质,分别介绍了湿法脱硫系统和选择性催化还原脱硝装置对元素态汞的氧化、湿法脱硫系统固定氧化态汞等技术的研究现状。文章分析了WFGD中氧气、SCR催化剂组分等因素对氧化Hg~0的影响,阐述了不同添加剂对于抑制脱硫浆液中Hg~(2+)再还原的效果。最后根据燃煤电厂烟气脱汞技术的发展需要,提出发展设备分工式脱除非颗粒态汞的研究方向。     

基于人工神经网络的燃煤烟气脱汞效率预测

针对燃煤烟气单质汞(Hg0)的脱除效率,采用神经网络遗传算法模拟寻优的方法获得最佳运行参数,并探讨多影响因子同时改变时脱汞效率的变化规律。利用田口试验方法设计试验,在固定床试验台架上考察负载量、煅烧温度、反应温度对脱汞效率的影响;采用64组试验数据对设计的多层神经网络进行训练、验证及测试,关联系数(R)在0.96以上,均方误差(Mean Squared Error,MSE)为0.007;对训练后的神经网络采用遗传算法进行多影响因子极值寻优。结果表明:采用硝酸锰浸渍催化剂的最优脱汞效率为95.1%;负载量为15%时,最佳脱汞效率、反应温度、煅烧温度分别为94.6%、141.8℃、445.2℃,进一步用试验验证了寻优结果的准确性。     

我国电石法生产聚氯乙烯行业汞排放清单

提出了我国电石法聚氯乙烯(PVC)生产全生命周期汞排放清单的计算方法。采用低汞触媒有盐酸脱吸工艺、高汞触媒有盐酸脱吸工艺、高汞触媒无盐酸脱吸工艺的汞输入因子分别为0.045 g/kt、0.091 g/kt和0.122 g/kt,回收产品的汞输出分布因子分别为95.37%、81.97%和97.18%。估算得到:2010年我国电石法PVC生产汞输入量792.8~814.8 t;回收的产品汞705.9~724.4 t,通过大气无组织排放、管道残留以及其他未知途径汞排放79.6~82.8 t;废水汞排放1.3 t;固体废物汞排放3.6~3.7 t;废酸汞排放2.5~2.6 t。回收的产品汞是汞输出的主要途径。     

烟气脱硫液中共存离子对汞稳定化的影响

利用湿法烟气脱硫技术(Wet Flue Gas Desulfurization,WFGD)同步除汞被认为是最经济的燃煤烟气脱汞方式,但进入脱硫液的Hg~(2+)易被还原并再次释放进入大气,造成二次污染.针对这一问题,本研究选择了常用的Na2S、三巯基均三嗪三钠盐(TMT)、二硫代氨基甲酸盐(DTC)等系列重捕剂,考察了投加量对Hg~(2+)去除效果的影响,并筛选出了去除效果较好的3种类型重捕剂,探究了脱硫液中主要的阴阳离子(SO_2-4、NO-3、Ca~(2+)、Mg~(2+))及重金属离子等共存离子对Hg~(2+)去除效果的影响.结果表明:Na2S、TMT类重捕剂TMT-18和DTC类重捕剂DTCR-2的去除效果相对较好;SO_2-4、NO-3会抑制TMT-18和Na2S对Hg~(2+)的去除,对DTCR-2稍有促进作用;Ca~(2+)、Mg~(2+)对TMT-18去除Hg~(2+)有促进作用,而对Na2S有抑制作用;重金属离子会抑制重捕剂对Hg~(2+)的去除效果,Cu~(2+)和Pb~(2+)对Hg~(2+)螯合去除效果的影响较Ni~(2+)和Zn~(2+)要大,随着Cu~(2+)和Pb~(2+)浓度的增加,DTCR-2对Hg~(2+)的去除显著降低,Cu~(2+)浓度的影响尤为显著.本研究可为解决Hg~(2+)在脱硫液中的还原再释放及二次污染问题,同时也为湿法烟气脱硫同时脱汞的工业应用提供理论依据.     

松花江鱼类系污染现状研究

松花江主要工业汞源根治后,该江吉林市至三岔河口和三岔河口至同江江段总汞与甲基汞已分别降到轻、中度污染水平。各江段鱼类总汞与甲基汞污染水平均表现出：肉食性鱼类＞杂食性鱼类＞植物食性鱼类;底层鱼类＞中、上层鱼类;无鳞鱼类＞有鳞鱼类。各江段每种鱼类肌肉中甲基汞含量与总汞含量之间呈明显的正相关关系,与脲酶、乳酸脱氢酶活力之间呈明显的负相关关系。鱼类肌肉中总汞含量与江水中总汞含量之间呈明显的多元直线、多元对数和多元指数回归关系;鱼类肌肉中甲基汞含量与江水中甲基汞含量之间呈明显的多元对数回归关系。