Evaluation of geo-environmental risks in the influence zones of oil and gas industry in the Russian Arctic

Acid precipitation monitoring in the Russian Arctic is important due to the crossboundary pollution (circumpolar transfer of pollutants from the west), and the development programs for the extraction of hydrocarbons on the continental shelf, in particular, on the platform “Prirazlomnaya” owned by “Gazprom Neft” — a subsidiary of JSC “Gazprom”. In the short term perspective, oil and gas exploration is going to be possible in the Kara Sea, the Gulf of Ob and in the Pechora Sea [1].

In the longer term perspective, oil and gas companies of JSC “Gazprom” and “Rosneft” consider the Barents Sea as perspective from the exploration point of view. Acid precipitation monitoring should be done after the extraction and transportation of the hydrocarbons in the Arctic and should be accompanied by quantitative risk assessment of acidification and eutrophication of terrestrial and marine ecosystems based on international approaches to calculation of critical load (CL) using the other relevant established international approaches [2, 3,

• 4]    and the results of the research, some of which are citied in the sources we use for the article [5—18].

Therefore, managing the risks of lower environmental quality of terrestrial and marine ecosystems in the expansion of oil and gas production in the Polar Regions becomes an urgent task as well as the studies of the biogeochemical fundamentals of terrestrial and marine ecosystems of the Arctic during the emission of acids in the areas of oil and gas industries [6].

Proposed methods and approaches to reach the goal are: 1. Quantitative assessment of the acid precipitation in the Arctic areas with current or panned oil and gas extraction activity. 2. Monitoring the changes in biogeochemical parameters of terrestrial and marine ecosystems in the Arctic areas where the influence of oil and gas production and transportation of hydrocarbons is observed. 3. The calculation of CL values of acidifying and eutrophying compounds of acidic emissions (nitrogen oxides) for the ecosystems in the areas of production and transportation of hydrocarbons. 4. Quantitative assessment of geo-ecological risks (GER) and the forecast of geo-ecological situation with identification of factors for cross-boundary transportation of acid precipitation and local emissions.

The concept of the GER assessment using the methodology of the CL pollutants

Under the proposed approach, the GER is defined as dimensional figure, characterized by the probability of negative changes in the state of ecosystems as recipients and the magnitude of such changes. Quantitative evaluation of the GER is based on distribution and spatial analysis of the exceedances of pollutant CL X (Ex (X)) within the boundaries of the zone of influence of the designed object. Excess of the CL reflect the ratio between the size of exposition (actual value or predicted pollutant load) and the safe level of exposure (the value of the critical load of pollutant). The value of influence for ecosystem is suggested to be calculated as the CL exceeds percentage of the total area selected (for example, of the sanitary protection zone of designed or existing object). Choice of criteria of acceptability of expected changes depends on the nature of the affected ecosystems. For ecosystems with the status of particularly valuable or vulnerable, the value of the CL should not be exceeded 100% of their area. In other cases, we are invited to follow the principle of “95% protection” of the ecosystems, according to which a level of acceptable load of pops is the level when 95% of the studies area is Ex (X) ≤0.

Calculation of GER should be done with the help of probabilistic modeling for the CL exceeds based on the Monte Carlo method. Unlike traditional method for calculation the CL exceeds, the input data for the model is not individual values of biogeochemical parameters

(default values or average values), but — arrays of their values. Array input data may be prepared on the basis of field data and the results of the analysis of objects-analogues. As a result, each individual receptor site receives a set of values for Ex (X) indicator. The frequency distribution of these values allows us to calculate the probability of P (from 0 to 100%) to achieve positive value of Ex (X) for each singled within the calculated area. Each value of P (Ex (X)> 0) will correspond to the value of M (Ex (X)> 0) — the total area of allotments with CL excess. Based on arrays of values (M; P) the risk function (R (X)) reveals:

R(X)=F{M,P}=F{M(E_x (X) >O,P(E_x(X) >O}, where M - the area of allotments with excess CL (Ex (X)> 0); P — the probability of exceeding the CL.

The GER function is a function of the distribution. With a large number of receptor plots an array of values (M; P) is well approximated by a continuous function of the normal distribution. If the number of allotments is small, then the transition to a normal distribution is impossible and the function will have a stepped form (Pic. 1).

Picture 1. Functions of the GER (R(X)) based on the stepped form of distribution (I) and the continuous function of the normal distribution (II)

The distribution function allows us to calculate the probability of exceeding P1 CL on the territory that is smaller than M1 and for a given range of values M (M1 ≤ Mi ≤ M2): P = P2 - P1.

The procedure of the GER evaluation based on the CL methodology

The GER assessment based on the CL pollutants means following the formal risk assessment procedures. At the stage of the risk identification we should be define the sources of emissions to determine possible scenarios of anthropogenic impact and make a complete list of pollutants contained in the emissions of the projected enterprise. In addition, it is necessary to outline the circle of potential recipients of impact (ecosystems within the zone of influence of the designed object) and classify them. On the basis of available information on the risks and its recipients it is necessary to make a qualitative description of impacts and to define the list of pollutants for a detailed risk assessment (priority pollutants). Exposure assessment should include a detailed description of the recipient (incl., the recipient ecosystems and receptor sites) with the establishment of a background and predicted load level of priority pollutants — quantities of pollutants (g / ha per year or the equivalent / ha per year). During the geoecological effects evalua-tion stage, there should be carried out a mapping and calculation of the CL values of priority pollutants characterizing maximum level of load on the selected recipients. Description of the GER should include calculations of the recipient’s changes, their probability, as well as the definition of the acceptability of such changes according to the selected criteria. It is proposed to make a risk description in two stages. The first step is a calculation of the CL exceeds based on the averaged input data. Then, in the case of receptor sites with Ex (X)> 0, it is advisable to evaluate the GER and use the models discussed below.

Studies evaluating the GER should be ended by the uncertainty analysis of results. In order to do so, it is necessary to describe the sources of uncertainty in each stage of the risk assessment and to evaluate the reliability of the calculations. The GER evaluation results GER are supposed to be used to rank individual project alternatives and developing the approaches to soften the impacts on the environment within the evaluation of environmental impact of planned economic activity.

Conclusion

The proposed risk assessment methodology for the ecosystems affected by the emissions of pollutants produced by the oil and gas industry, allows quantifying not only the values of changes in ecosystems, but also their probability. It is possible to make a detailed description of ecosystems as the objects of technogenic impact. In addition, this method takes into account the close relationship between individual components of the terrestrial and maritime ecosystems, and variation of natural parameters usual of these ecosystems. The GER assessment could be done when preparing environmental reports for oil and gas industry, located in areas with a high degree of uncertainty, including the Arctic region.

Currently, these studies made within cooperation between the Institute of Physical, Chemical and Biological Problems of Soil of the RAS/FASO, JSC “Gazprom” and NArFU. Approaches to monitoring acid precipitation, evaluation of biogeochemical transformation of the polar ecosystems and quantitative evaluation of the GER have been developed. Similar studies are carried out in a number of Scandinavian countries and Canada within the framework of the UN Convention on Long-range Transboundary Air Pollution. V.N. Bashkin had been a deputy Chairman of the Scientific Committee of the Convention for a long time.

The GER evaluation is carried out by the JSC “Gazprom” [6], and its continued use in the practice of other oil and gas companies will let to evaluate the probability of these risks when developing Arctic deposits and identify ways to manage these risks, through the environmental insurance system [1, 2, 5, 14, 16,18].