Fibre-optic sensor arrays for testing of water contamination

汞等重金属对环境的污染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350，000磅汞。 这些工厂中的许多自20世纪60年代以来一直在运营，并且完全没有减少排放的设备，但它们通过世界上最便宜的工艺生产了美国53%的电力。 全球排放量接近1200万磅/年，预计随着中国和印度日益增长的电力需求和老化的基础设施，排放量将沿着增加。汞以外的污染物可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、废物管理场所以及水源保护和取水区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，对垃圾填埋场周围5个地点的地下水样本进行测试。 然而，分析费用（每孔每个样品最低250美元）将测试频率限制为每年仅四次。 这种不经常进行的测试不允许在垃圾填埋场的沥滤液进入地下水供应时进行快速干预。我们计划开发一种廉价，便携式，实时传感器的各种地下水污染物。 传感器的关键部分是一根光纤电缆，它是定制的，可以控制通常包含在光纤芯内的一些光的损失。 损失的光量受电缆外部环境的影响。 Loock和Brown已经表明，可以将选择性吸收有机污染物（如芳香烃）的聚合物放置在电缆的外部，从而检测到甲苯和其他碳氢化合物。 同样的测量原理也可以应用于金属离子的检测。 Crudden、Loock和Brown目前正在测试有机/无机复合材料，这些复合材料含有大比例的已知可与汞结合的巯基。 已知相关的复合材料每克材料结合多达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