注册 登录  
 加关注
查看详情
   显示下一条  |  关闭
温馨提示!由于新浪微博认证机制调整,您的新浪微博帐号绑定已过期,请重新绑定!立即重新绑定新浪微博》  |  关闭

吉建斌的网易博客

吉建斌

 
 
 

日志

 
 

汞元素赋存之地理环境模型(06)  

2017-11-10 08:19:53|  分类: 不归类文章 |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |

汞元素赋存之地理环境模型(06) - 不在眉头愁 - 吉建斌的网易博客

Figure 4. Nickel concentration versus pH in mercury mine drainage from silica-carbonate type and hot-spring type mercury deposits.

Total mercury concentration (dissolved and adsorbed onto particulate phases) in mine drainage shows extreme variability even within deposit type, ranging from less than 1 μg/L to over 200 μg/L (ppb) (fig. 5). The mercury concentration often exceeds the drinking water standard, 2 μg/L (ppb), and the aquatic criteria for continuous concentration, 0.012 μg/L (ppb).

汞元素赋存之地理环境模型(06) - 不在眉头愁 - 吉建斌的网易博客

Figure 5. Mercury concentration in mercury mine drainage from silica-carbonate type and hot-spring type mercury deposits.

The large range in mercury concentration is caused by several factors. The most import factors are the solubility of the mercury phases with which the mine drainage interacts and the amount and adsorption capacity of the particulate phases present. Mercury speciation, as well as the concentration of mercury in mine drainage, is also an important variable in assessing the potential environmental impact that mine drainage may have on water quality and biota. Elevated levels of mercury, as well as high sulfate concentration in mine drainage, enhance methylation of mercury by sulfate-reducing bacteria in environments impacted by mine drainage. The mercury species present in mine drainage are strongly affected by chemical processes that occur when mine drainage reacts with mine wastes and surface waters. For this reason the composition of mine drainage is discussed for three different mine environments: (1) at the point of discharge from underground mine workings; (2) mine drainage that has reacted with mine wastes; and (3) mine drainage that has mixed with stream water.

Mine Drainage from Underground Mine Workings

At the point of discharge from underground mine workings, the pH of mine drainage from silica-carbonate type mercury deposits is moderately to weakly acidic ranging from 3.1 to 6.9. The pH of hot-spring type mercury deposits is variable, because these deposits are hosted in a variety of rock types that have varying degrees of neutralizing capacity. Low pH is associated with deposits hosted in clastic sedimentary rocks, or volcanic rocks that have been intensely altered to an advanced argillic assemblage of quartz-kaolinite-cristobalite-alunite. Neutral to alkaline pH is associated with deposits hosted in mafic volcanic rocks and in recently formed deposits that contain thermal waters having a high alkalinity (Donnelly-Nolan and others, 1993: Janik and others, 1994). Some mine drainage is composed dominantly of thermal water, such as at the Elgin mine, California, where the pH is alkaline, 8.15. The iron concentration in mine drainage ranges from 0.1 to 7600 mg/L, and is present dominantly in the reduced form, Fe (II). The highest iron concentrations are associated with silica-carbonate type deposits that are localized in and adjacent to mafic intrusions where large amounts of pyrite and marcasite, up to 50 percent by volume, were introduced into the country rock. Mine drainage waters from hot-spring type deposits have lower concentrations of iron because the deposits have lower iron sulfide content. The range in total (unfiltered) mercury concentration is comparable for both deposit types ranging from .005 to 8.0 μg/L for silica-carbonate type deposits and from .01 to 10.0 μg/L for hot-spring type deposits (fig. 5). For both deposit types, filtered samples (0.45 μm) of mine drainage always have lower concentrations of mercury indicating that a significant portion of the mercury present is adsorbed onto particulate phases and colloids (fig. 5). Oxidation and weathering of iron sulfides exposed in underground mine workings and in back fill waste rock contributes to the high sulfate concentration in both deposit types. Sulfate concentration exceeds several thousand mg/L and is highest in silica-carbonate type mercury deposits that have a high iron sulfide content. Total methylmercury concentration of mine drainage ranges from <.003 to 1.26 ng/L with highest concentrations associated with silica- carbonate type deposits (fig. 6). Filtered samples of mine drainage typically contain lower concentration of methylmercury indicating that methylmercury is also adsorbed onto particulate phases and colloids (see discussion below). Highest methylmercury concentrations occur in waters with high sulfate concentration indicating that underground mines provide an environment for sulfate-reducing bacteria to methylate mercury but methylation is limited by the availability of dissolved organic carbon in this environment.

汞元素赋存之地理环境模型(06) - 不在眉头愁 - 吉建斌的网易博客

Figure 6. Methylmercury concentration in mercury mine drainage from silica-carbonate type and hotspring type mercury deposits.

Mine Drainage Composition after Reaction with Atmospheric Oxygen and Mine Wastes

After mine drainage exits the underground mine workings, reaction with atmospheric oxygen results in the oxidation of the dissolved iron (II) to iron (III) and precipitation of iron oxyhydroxide. Mine drainage from silicacarbonate type deposits that have high iron concentration can develop extreme acidity (pH as low as 2.6) (fig. 3) after reaction with atmospheric oxygen causes precipitation of iron oxyhydroxide. Mine drainage often flows over and through mercury-enriched waste rock and mine tailings, because this material typically was disposed in and adjacent to a stream channel that was closest to the mine workings. In mine tailings, mercury commonly is present in soluble phases such as mercury sulfates and oxy-chlorides that were formed during the ore-roasting process (Kim and others, 1998, 2000). As mine drainage reacts with calcines, mercury and methylmercury concentrations in the water increase dramatically, up to two orders of magnitude, because soluble mercury phases are dissolved and the addition of sulfate to the calcines allows sulfate-reducing bacteria to methylate the dissolved mercury (fig. 5) (Rytuba, 2000). Mercury-contaminated soils, especially those that are saturated with water, have been shown to provide a favorable environment for methylation of mercury (Hines and others, 1999). The saturation of mercurycontaminated soils and various types of mine wastes by mine drainage having a high sulfate concentration enhance methylation of mercury in these mine environments.

 

多膛炉设备系统设计、建造、安装工程以及废水深度处理回用相关业务,请联系:

关光(先生):北京北宇机械设备有限公司,18001368585

吉建斌(先生):18603463183,jzhx928@163.com

  评论这张
 
阅读(6)| 评论(0)

历史上的今天

在LOFTER的更多文章

评论

<#--最新日志,群博日志--> <#--推荐日志--> <#--引用记录--> <#--博主推荐--> <#--随机阅读--> <#--首页推荐--> <#--历史上的今天--> <#--被推荐日志--> <#--上一篇,下一篇--> <#-- 热度 --> <#-- 网易新闻广告 --> <#--右边模块结构--> <#--评论模块结构--> <#--引用模块结构--> <#--博主发起的投票-->
 
 
 
 
 
 
 
 
 
 
 
 
 
 

页脚

网易公司版权所有 ©1997-2018