Natural geochemical hazard as a pseudo-component of negative environmental impact of mining complexes

. The paper presents the authors’ research findings that enable to avoid unreasonable charges for negative environmental impact by applying mathematical statistics and GIS technology, modern methods of geochemical sample data processing, as well as by analysis of the dynamics of engineering-geological phenomena in the mining complexes areas. The authors ’ data on the manifestation of high concentrations of toxic elements in some landscape components on the territory of mining complexes are provided. The latter, according to the authors, are associated with the outcrop of molybdenum ore occurrences, which were previously blocked by thin Р leistocene deposits. Then, due to sloughing of these deposits, molybdenum compounds began penetrating to the environment components.


Introduction
The purpose of this paper is to show how to avoid unjustified charges for negative environmental impact using mathematical statistics [1] and GIS technology, by applying modern geochemical data processing methods, as well as analyzing the dynamics of engineering-geological conditions in mining complexes areas.The relevance of the research is explained by the fact that mining and processing complexes (MPC) are usually located in the immediate vicinity of mineral extraction and enrichment places, such as quarries, mines, tunnels, processing plants, tailings and sludge storage facilities, etc.Their operation provides for installing an environmental monitoring network [2] and its maintaining within the mining allotment boundary (i.e. the so-called local or industrial (object-based) monitoring) of mining and processing complexes, as well as in the zone of their environmental impact.The environmental monitoring program normally includes mandatory routine observations of toxic elements (TE) concentration and their compounds in surface and ground water, bottom sediments, soils and other landscape components.At the same time, the TE content, as a rule, significantly exceeds the maximum allowable concentration (MAC) value in many components of the natural environment.It refers to the chemical elements that make up the ores extracted and processed at the MPCs, as well as chemicals used for ore concentrating and processing.
The specific novelty of this research lies in the fact that the authors identify a specific component of the natural ore-caused geochemical hazard that arises due to natural enrichment of underground and surface waters, bottom sediments and other landscape components by chemical ore elements.For this purpose, it is necessary to take into account the value of the natural geochemical background, which, in ore areas is generally higher than the MAC value, due to the presence of ore elements.[3].Normalizing the indicators obtained through testing (chemical elements concentrations) to the local geochemical background just allows one to take into account fluctuations in concentrations of pollutants, which are introduced by the mining complex itself.This case excludes the pollution caused by enrichment of ore components, the higher content of which (and they may be toxic elements) is observed in the natural environment.
As is known, there are certain geochemical provinces with higher concentration of chemical elements in various landscape components, due to natural features.For example, dry steppes on salt marshes in the Altai Region tend to accumulate such toxic elements as Co, Sr, Mo and Sc [4], and in North Ossetia the accumulation of As, Tl, Cu, Zn, Pb, Ba, Mn, B, Li, etc. is observed in most of the studied landscape elements [5].Abnormal geochemical fields (AGF) of ore originated elements prevail within the MPC boundaries.Their manifestation varies in intensity, as a rule, in all geological media.Of course, they are most explicitly manifested in depositing media and, especially, in bottom sediments.
As was shown earlier [6], during the mining complexes operation, chemical elements that are not found in typomorphic ore deposit associations begin to appear as part of environment components.Most often, this is how man-caused geochemical anomalies manifest themselves.They are distinguished by high intensity and complexity.At the same time, the association of elements in the series of their accumulation and removal does not, as a rule, correspond to the ore-formation affiliation of the deposit fields being developed.In addition, man-caused abnormal geochemical fields usually have a low level of correlation of chemical elements in the soil profile [7].This factor was used by the authors to identify the share of the natural geochemical component in the MPCs' negative impact on the environment.
Geochemistry of natural and mining landscapes was studied by such well-known scientists as B.B. Polynov, A.I. Perelman N.S., Kasimov [8], V.S. Arzhanova and P.V. Elpatyevsky, M.A. Glazovskaya and many others.Among foreign scientists, made a notable contribution to the study of the behavior of heavy metals in water and in soils [9].
The method for normalizing bulk concentrations of metals dates back to the names of A.P. Solovov, A.I. Perelman and other domestic and foreign geochemists and was originally used for mineral prospecting.Later on, it began to be used in ecology.For evaluation of environmental pollution it was applied for the first time by Sayet Yu.E.He suggested a total indicator of soil pollution (which is still used in Russia -Sanitary and epidemiological rules and regulations.SanPiN 2.1.7.1287-03 "Sanitary and epidemiological requirements for soil quality"), the calculations of which are based on normalizing the ith pollutant to the background concentrations of the same substance.Then other sanitary and hygienic standards were also developed and adopted to assess the chemical anthropogenic impact of industrial facilities on the environment.
Compiling maps of natural hazards using GIS technologies was done by Galushkin I.N.[5], but mainly in the field of the dynamics of hazardous geological processes.The authors of this paper used an integrated approach combining the study of hazardous geological processes and the basics of landscape geochemistry.

Brief description of the research object
The research object of this work is the mining complex in the mineral deposit fields of the Khibiny Tundra.It includes the existing Kirovsky and Rasvumchorrsky mines (Kukisvumchorr deposits), as well as apatite-nepheline processing plants (ANOF-1, ANOF-2 and ANOF-3) and zones of their influence.All these enterprises are the production assets of JSC "Apatit" (Figure 1).These deposit fields are located on the Kola Peninsula (Murmansk Region).They are characterized by large ore reserves, a long period of their mining (more than 80 years) and a wide range of enviornment pollutants, including highly toxic elements [10].

Materials and methods
The main materials of the study were the authors' data obtained through field work in the impact zone of the Khibiny Tundra deposit fields, where lithogeochemical and hydrochemical samples were taken and field observations were carried out.Laboratory studies of samples were performed using the methods of atomic absorption for gross forms of mercury (in all samples) and mass spectrometric analysis (ICP-AES) for samples of underground and surface waters [13] and mobile forms of soil elements and bottom sediments (46 elements), gross forms were analyzed by mass spectrometry with inductively coupled plasma ICP-MS.
Office processing of materials was carried out using methods of mathematical statistics, and GIS technologies were applied for processing geochemical and mapping data with the software Argis, Exel, and Statistic.

Results and discussion
Increased concentrations of Mo were recorded by the authors in underground and surface waters, bottom sediments and soils in the zone of influence of the tailings dump of the operating apatite-nepheline processing plant of JSC "Apatit" (ANOF-3, see Figure 1).This was also confirmed by the object-based (local) monitoring of the above-mentioned environments.When mapping the territory adjacent to the mining complex, ore occurrences of this element were identified.During the engineering-geological survey of the area, it was found that before the development of the Kukisvumchorr apatite-nepheline deposit, the ore occurrences of molybdenum, being hypsometrically higher, were blocked with Pleistocene deposits.Over time, their sloughing occurred (the traces of which were recorded by the authors), the bedrock was exposed and began to collapse.Due to sheet flood and other geological processes, mainly of a gravitational nature [14], molybdenum compounds penetrated into bottom sediments.When their accumulation became critical, it contributed to secondary pollution of surface waters, which is typical of the areas of MPCs' activity, where supercritical concentrations of ore elements often accumulate in bottom sediments [7].
As the result, molybdenum (Mo) turned out to be among the pollutant elements, for excess discharge of which the company has to pay increased charges for harmful environmental impact.Of course, it is also necessary to prove that the landslides were not caused by cutting the slopes during the construction of the apatite-nepheline tailings processing plant of the second stage (ANOF-2) and not due to seismic impact from explosions at the Kirovsky mine quarries or other man-made processes.However, there are a number of counterarguments to these assumptions, and namely: the construction of the ANOF-2 tailings dump and the transition to underground mining technique (and, consequently, a significant decrease in the seismic load on the environment) occurred long before the activation of the landslides described above.On the other hand, a gradual increase in precipitation according to the Khibiny meteorological station data is observed from year to year, and this trend (climate change towards its humidification) occurs everywhere, especially in mountainous and foothill areas [15].As is known, the activation of landslides is greatly facilitated by waterlogging of slopes and, especially steep slopes, having clay or loam at the base.And it is mainly such rocks that represent moraine debris that overlapped, albeit with an insignificant cover, the bedrock of the slope.Thus, the landslide activation is most likely associated with natural phenomena and is not caused technogenically.
Then, in order to differentiate natural and man-made anomalies of chemical elements, the authors carried out a procedure for normalizing the concentrations of chemical elements in soil level B to those in soil level A over the entire research area.It means that at each sampling point the concentration value in soil level B was divided by the value in soil level A. Subsequently, by applying GIS technologies, Maps of distribution of the element concentrations ratios (in this case Mo) in B/A soil levels were compiled.Since, as a rule, ore elements accumulate in the soils of level B, and technogenically conditioned elements accumulate in soil level A, such a procedure makes it possible to identify natural accumulation (enrichment) of individual chemical elements in soil.The figure below shows such a map for molybdenum concentration values.This map shows the distribution of the molybdenum concentration ratios in the soil levels B and A and makes it possible to localize the anomaly of molybdenum of ore genesis in the immediate vicinity of the northeastern part of the tailings dump and hypsometrically above it.The latter postulate (about 'ore genesis') is also confirmed by the fact that abnormal geochemical fields (AGF) of molybdenum satellite elements (As, Ag, Zn Cu, Sb, W and a number of rare earth elements) are localized within the same contours.
In addition, to substantiate the ore genesis of a number of AGFs in the zone of influence of the Apatit Mining and Processing Complex, which is engaged in both extraction and enrichment of apatite-nepheline raw materials, the authors performed a factor analysis (FA).For this purpose, soil samples were taken within the area of activity of the above-mentioned MPC.Then, based on the results of mass spectrometric analysis ICP-MS, the FA by the principal component method was performed.This method is known to be the most convenient for 'compressing' data in order to identify generalized characteristics of the nature or phenomenon being studied.Its main condition is that the main components are independent, and their number is equal to the number of original features.
As the result of factor analysis, two bipolar associations of chemical elements were identified.The first one includes phosphorus and rare earth elements (Ho, Er, Dy, Tb and others) -typomorphic elements of mineral deposits.The second association (Mn, Fe, Mo, As, Cd and some others) combines elements that accumulate in soils in the MPC influence zone and is obviously related to ore processing.Moreover, the spatial distribution of the association of the first row of elements shows that they are located in the ore extraction zone, and the second association is manifested in the zone of ore transportation and enrichment, i.e. its nature is man-made.

Conclusion
Thus, using the authors' materials as an example, it is shown that in order to isolate the contribution of natural factors, it is possible to substantiate that the excessive charges for harmful impact of MPC on the environment are unjustified.To do this, the following actions are necessary: 1. to study archival materials and literature, as well as local monitoring data of the survey area; 2. perform geochemical sampling and engineering-geological survey of the MPC's impact area; 5. use methods of mathematical statistics (and FA in particular,) to interpret the data obtained; 6. apply GIS technologies for geochemical data processing and for compiling the maps, which allows getting a visual spatial representation of the toxic elements distribution and their normalized values.
The set of above-mentioned actions provides for avoiding unreasonably high charges for the adverse impact on the environment (if it is caused by the manifestations of toxic elements of natural genesis) in the mining and processing areas.

Fig. 1 .
Fig. 1.Location of the research objects within the area of the Apatit mining complex [10].

E3SFig. 2 .
Fig. 2. Location map of molybdenum concentration ratios in B and A soil levels (Compiled by the authors)