Fibre-optic sensor arrays for testing of water contamination

汞等重金属污染环境是对人类健康和生态系统的持续威胁。燃煤电厂是汞排放的主要来源，在美国每年产生约35万磅汞。这些发电厂中的许多自上世纪60年代以来一直在运行，完全没有减少排放的设备，但它们以世界上最便宜的工艺生产了美国53%的电力。全球二氧化碳排放量接近1200万磅/年，预计随着中国和印度电力需求的增加和基础设施的老化，二氧化碳排放量还会增加。汞以外的污染物可以通过多种途径进入地下水。为了防止污染，在工业和军事场所、废物管理场所以及节水和取水区域周围进行监测至关重要。法规要求在垃圾填埋场关闭后的25年内，在填埋场周围的5个地点检测地下水样本。然而，分析成本（每口井每个样品至少250美元）限制了每年仅进行四次测试的频率。如果垃圾填埋场的渗滤液进入地下水供应系统，这种不频繁的检测不允许进行快速干预。我们计划开发一种廉价、便携、实时的传感器，用于监测各种地下水污染物。传感器的关键部分是一根定制的光纤电缆，可以控制光纤芯中通常包含的一些光的损耗。光损失的数量受到电缆外部环境的影响。洛克和布朗已经证明，选择性吸收有机污染物（如芳香烃）的聚合物可以放置在电缆的外部，从而检测甲苯和其他碳氢化合物。同样的测量原理也适用于金属离子的检测。克鲁登、洛克和布朗目前正在测试有机/无机复合材料，这种材料含有大量已知能与汞结合的硫醇基团。已知相关复合材料每克材料含有高达0.7克汞

Contamination of the environment with heavy metals such as mercury is a continuing threat to human health and the ecosystem.  Coal-fired plants are the main source of mercury emissions, producing an estimated 350,000 lbs/year in the US.  Many of these plants have been in operation since 1960's and have absolutely no equipment to reduce emissions, but they produce 53% of the electricity in the US by a process that is among the world's cheapest.  Global emissions are at almost 12 million lbs/year, predicted to increase along with China and India's increasing electricity needs and aging infrastructure. Pollutants other than mercury can enter groundwater by a variety of pathways.  In order to prevent contamination, monitoring around industrial and military sites, waste management sites, and water conservation and intake areas is critical.  Regulations require testing of groundwater samples at 5 locations around a landfill, for 25 years after it has been closed.  However, the cost of the analysis (minimum $250 per sample per well) limits the frequency of the testing to only four times a year.  Such infrequent testing does not allow for fast intervention should leachate from a landfill enter the ground water supply. We plan to develop an inexpensive, portable, real-time sensor for a large variety of ground water contaminants.  The key part of the sensor is a fibre optic cable that is customized to allow a controlled loss of some of the light normally contained within the fibre core.  The amount of light lost is affected by the environment immediately outside the cable.  Loock and Brown have shown that polymers that selectively absorb organic contaminants such as aromatic hydrocarbons can be placed on the exterior of the cable, resulting in detection of toluene and other hydrocarbons.  The same measurement principle can be applied to the detection of metal ions.  Crudden, Loock and Brown are currently testing organic/inorganic composites, which contain a large proportion of thiol groups known to bind mercury.  Related composites are known to bind up to 0.7 grams of mercury per gram of material