Shakhawat Chowdhury, Tahir Husain, Neil Bose
Faculty of Engineering & Applied Science, Memorial University of Newfoundland, St. John's, NL A1B3X5, Canada.
J Environ Radioact. 2006;89(1):1-17. doi: 10.1016/j.jenvrad.2006.03.002. Epub 2006 May 26.
Produced water, discharged from offshore oil and gas operations, contains chemicals from formation water, condensed water, and any chemical added down hole or during the oil/water separation process. Although, most of the contaminants fall below the detection limits within a short distance from the discharge port, a few of the remaining contaminants including naturally occurring radioactive materials (NORM) are of concern due to their bioavailability in the media and bioaccumulation characteristics in finfish and shellfish species used for human consumption. In the past, several initiatives have been taken to model human health risk from NORM in produced water. The parameters of the available risk assessment models are imprecise and sparse in nature. In this study, a fuzzy possibilistic evaluation using fuzzy rule based modeling has been presented. Being conservative in nature, the possibilistic approach considers possible input parameter values; thus provides better environmental prediction than the Monte Carlo (MC) calculation. The uncertainties of the input parameters were captured with fuzzy triangular membership functions (TFNs). Fuzzy if-then rules were applied for input concentrations of two isotopes of radium, namely (226)Ra, and (228)Ra, available in produced water and bulk dilution to evaluate the radium concentration in fish tissue used for human consumption. The bulk dilution was predicted using four input parameters: produced water discharge rate, ambient seawater velocity, depth of discharge port and density gradient. The evaluated cancer risk shows compliance with the regulatory guidelines; thus minimum risk to human health is expected from NORM components in produced water.
从海上油气作业中排放的采出水，含有来自地层水、冷凝水以及井下或油水分离过程中添加的任何化学物质。尽管大多数污染物在离排放口很短的距离内就会降至检测限以下，但包括天然放射性物质（NORM）在内的一些残留污染物因其在介质中的生物可利用性以及在供人类食用的鱼类和贝类中的生物累积特性而受到关注。过去，已经采取了多项举措来模拟采出水中NORM对人类健康的风险。现有风险评估模型的参数在本质上不精确且稀少。在本研究中，提出了一种基于模糊规则建模的模糊可能性评估方法。由于可能性方法本质上较为保守，它考虑了可能的输入参数值；因此，与蒙特卡罗（MC）计算相比，能提供更好的环境预测。输入参数的不确定性通过模糊三角隶属函数（TFN）来捕捉。应用模糊条件规则，针对采出水中和总体稀释中存在的两种镭同位素，即镭 - 226（²²⁶Ra）和镭 - 228（²²⁸Ra）的输入浓度，来评估供人类食用的鱼类组织中的镭浓度。使用四个输入参数预测总体稀释情况：采出水排放速率、环境海水流速、排放口深度和密度梯度。评估的癌症风险表明符合监管指南；因此，预计采出水中的NORM成分对人类健康的风险最小。
