Heavy metal and petroleum product concentrations in waters at the Obskaya 1 drill site

During recent years, the basins of the Kara Sea (Kamennomysskaya, Obskaya, and Chugor'yakhinskaya structures) in the Russian Federation have been considered as promising regions for oil and gas exploration and, simultaneously, as possible paths of relatively cheap pipeline and tanker transportation of hydrocarbons projected for recovery. On the other hand, exploration operations, recovery, and transportation of gas pose a considerable risk of accidents and environmental pollution, which causes a justified concern about the future state of the ecological system of the Gulf of Ob and the adjoining parts of the Kara Sea. Therefore, regular combined environmental investigations (monitoring) are the most important factor for estimating the current state and forecasting the dynamics of the development of estuary systems. The program of investigations (schedule, station network, and measured parameters) is standardized in accordance with the international practice of such work and accounts for the experience of monitoring studies of Russian and foreign researchers. Two measurement sessions were performed during ecological investigations in the region of exploration drilling: at the beginning at final stage of drilling operations and borehole testing; in addition, natural parameters were determined in various parts of the Ob estuary before the beginning of investigations. Hydrophysical and hydrochemical characteristics of the water medium were determined and bottom sediments and water were analyzed for various pollutants (petroleum products, heavy metals, and radionuclides). The forms of heavy-metal occurrence in river and sea waters were determined by the method of continuous multistep filtration, which is based on water component fractionation on membrane filters of various pore sizes. These investigations revealed environmental pollution by chemical substances during the initial stage of drilling operations, when remains of fuels, oils, and solutions could be spilled, and part of the chemical pollutants could enter the environment. Owing to horizontal and vertical turbulent diffusion, wave mixing, and the effect of the general direction of currents in the Ob estuary from south to north, areas are formed with elevated concentrations of the analyzed elements and compounds. However, the concentration levels of chemical pollutants are practically no higher than the maximum admissible concentrations, and their substantial dissipation to the average regional background contents can be expected in the near future. Our investigations allowed us to determine in detail the parameters of anthropogenic pollution in the regions affected by hydrocarbon exploration drilling in the Obskii and Kamennomysskii prospects in the Gulf of Ob and estimate their influence on the ecological state of the basin of the Ob River and the Kara Sea on the whole.

近年来，俄罗斯联邦境内喀拉海（Kamennomysskaya、Obskaya及Chugor'yakhinskaya构造）盆地被视为极具潜力的油气勘探区域，同时也被规划为拟开采烃类物资的低成本管道与油轮运输通道。另一方面，天然气的勘探作业、开采与运输存在较高的事故与环境污染风险，这引发了人们对鄂毕湾及毗邻喀拉海海域生态系统未来状态的合理担忧。因此，常态化联合环境调查（监测）是评估河口系统现状、预测其发育动态的核心要素。本次调查方案（含采样计划、测站网络与测量参数）参照国际同类工作惯例制定，并整合了俄国内外研究者的监测研究经验。勘探钻井区域的生态调查共开展两期测量：分别于钻井作业的初期与末期及井筒测试阶段进行；此外，在调查启动前，已对鄂毕河口各区域的自然参数完成测定。本次研究测定了水体的水物理与水化学特征，并对底沉积物及水体中的各类污染物（石油产品、重金属、放射性核素）开展分析。研究采用连续多步过滤法，通过不同孔径的膜滤器对水体组分进行分级分离，以此测定河海水体中重金属的赋存形态。调查结果显示，钻井作业初期存在化学物质污染环境的情况：此时燃料、油品及作业溶液可能发生泄漏，部分化学污染物由此进入环境。受鄂毕河口水平与垂直湍流扩散、波浪混合，以及整体自南向北的流场影响，部分区域的被测元素与化合物浓度出现升高。但化学污染物的浓度水平均未超过最大允许浓度，预计短期内其浓度可大幅衰减至区域平均背景值水平。本次研究详细明确了鄂毕湾内鄂毕斯卡亚与卡缅诺梅斯卡亚油气勘探区块受钻井活动影响的人为污染参数，并评估了这些污染对鄂毕河流域及喀拉海整体生态状态的影响。