Natural Geochemical Anomalies Research Articles

Establishing geochemical background levels of selected trace elements in areas having geochemical anomalies: The case study of the Orbetello lagoon (Tuscany, Italy)

The determination of background concentration values (BGVs) in areas, characterised by the presence of natural geochemical anomalies and anthropogenic impact, appears essential for a correct pollution assessment. For this purpose, it is necessary to establish a reliable method for determination of local BGVs. The case of the Orbetello lagoon, a geologically complex area characterized by Tertiary volcanism, is illustrated. The vertical concentration profiles of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn were studied in four sediment cores. Local BGVs were determined considering exclusively samples not affected by anthropogenic influence, recognized by means of multivariate statistics and radiochronological dating (137Cs and 210Pb). Results showed BGVs well-comparable with mean crustal or shale values for most of the considered elements except for Hg (0.87 mg/kg d.w.) and As (16.87 mg/kg d.w.), due to mineralization present in the catchment basin draining into the lagoon.

Аккумуляция тяжелых металлов в растениях Южного Дагестана в условиях природной геохимической аномалии

Аккумуляция тяжелых металлов в растениях Южного Дагестана в условиях природной геохимической аномалии

Chemical composition of waters in a former Cu-As mine: water–rock interaction, REE systematics and stability of secondary copper minerals

Waters in the vicinity of natural geochemical anomalies such as hydrothermal ore deposits potentially mobilize heavy metals by interaction with primary hydrothermally formed minerals. On the other hand, secondary alteration minerals can retain some of these heavy metals and effectively immobilize them. In order to understand the chemical evolution of waters in such a system, the best way is to compare different waters from various sample locations in a well-defined locality. Thereby one can compare the importance of parameters such as variable flow paths, flow velocities, fluid-host rock interaction and the various sources and sinks of major and trace elements. This was done for the Cu and As deposit of Neubulach in the northern Schwarzwald, Germany. Flowing and dripping waters from three sites in the abandoned mine were sampled monthly over 14 months. The waters were analyzed with respect to their major and trace element concentrations including rare earth elements (REE) to evaluate their seasonal and spatial variation. The three sample types collected from different depths in the mine have different flow paths and are influenced to different extents by the sandstone host rocks, by overlying carbonates and by the hydrothermal barite quartz vein with Cu-Bi-As ores, mainly tennantite, exploited from the former mine. The sample site in the upper part of the mine (“HGS water”) is about 30 m below surface and the amount of water dripping from the roof of the adit is strongly dependent on the precipitation. By contrast, the water collected in the lower part of the mine (about 100 m below surface) is dripping constantly throughout the year and forms abundant calcite sinters (“sinter water”). A third sample was collected monthly from the mine drainage adit (again about 100 m below surface), that collects water from the entire mine (“flowing water”). Elevated Cl and Na concentrations and increased Cl/Br ratios in the HGS waters taken in the winter months during snow melt indicate input of road salt and therefore show the direct influence of surface runoff. By contrast, the sinter water compositions do not show any variation during the year, which suggests that these waters are unaffected by short-time input from the surface; their chemical composition is determined by water-rock interaction only. Rare earth element patterns and Rb/Cs values indicate interaction with clay minerals whereas Cu and As systematics show that tennantite dissolution is incongruent. Although inverse modelling shows that reaction of surface water with the observed phases in the host rocks and in the hydrothermal vein nicely explains the water compositional variations, speciation modeling and calculations of thermodynamic stabilities of various Cu arsenates suggest that secondary alteration minerals may form metastably.

Soil pollution related to mercury-mining activities in the proximity of Usagre (Badajoz, SW Spain)

Usagre (Badajoz, SW Spain) mercury mine was active for an undetermined time until its closure in 1971. The ore exploited in this mine was cinnabar (red HgS), and metallurgy was also performed locally by means of primitive furnaces of the Bustamante type. Since the closure of the mine, reclamation measures have not been carried out at the site, and actual passives include a mine shaft, an accessible descending gallery and a mine dump adjacent to the descending gallery. In the work described here, data from two soil geochemistry surveys were combined and analysed. The surveys were separated by a period of 32 years. Measurements of total gaseous mercury (TGM) in the underground mine and its surroundings were also considered. The soil geochemistry included mercury, lead, zinc and copper. The results indicate that soil pollution is mostly related to the trace mineralisations on the surface and they can therefore be interpreted as natural geochemical anomalies. TGM concentrations are extremely high inside the mine but are of very low concern outside the mine.

Microbial effects on the release and attenuation of arsenic in the shallow subsurface of a natural geochemical anomaly

Critical factors leading to arsenic release and attenuation from the shallow subsurface were studied with multidisciplinary approach in the natural gold–arsenic geochemical anomaly at Mokrsko (Czech Republic). The results show that microbial reduction promotes arsenic release from Fe(III) (hydr)oxides and Fe(III) arsenates, thereby enhancing dissolved arsenic in the shallow groundwater at average concentration of 7.76 mg/L. In the organic-rich aggregates and wood particles, however, microbial sulfate reduction triggers the formation of realgar deposits, leading to accumulation of As in the distinct organic-rich patches of the shallow subsurface. We conclude that precipitation of realgar in the shallow subsurface of soil/sediment depends on specific and non-trivial combination of water and rock chemistry, microbial community composition and spatial organisation of the subsurface zone, where speciation in saturated environments varied on a centimeter scale from reduced (decomposed wood, H2S and realgar present) to oxidized (goethite and arsenate minerals are present).

ADAPTATION OF SMALL MAMMALS TO CONDITIONS OF BIOGEOCHEMICAL PROVINCE WITH THE INCREASED LEVEL OF HEAVY METALS

At present, the natural non-endemic geochemical anomalies impacts on biota are not studied enough. The purpose of this work was to study effects of the natural geochemical anomaly with high content of nickel, cobalt and chrome on animals. The anomalous environment accounts for low abundance of small mammals, changes in the interior weight characteristics, alterations in the adrenal cortex structure, and reproductive function modifications. Natural anomalies serve as a factor of the additional functional load upon reproductive and endocrine systems.

Analysis of meiotic chromosome aberrations in Siberian spruce (Picea obovata Ledeb.) under conditions of natural and technogenic stress

Meiotic abnormalities have been studied in Siberian spruce growing in the Southern Urals under different ecological conditions: in contrasting natural landscapes (high mountains, plains, river valleys and floodplains), in zones of natural geochemical anomalies, and in areas with different levels of industrial pollution. The results provide evidence for an adverse effect of technogenic pollution and extreme environmental factors on the process of microsporogenesis in the species studied.

Udokan sulphide ore oxidativ leaching with acting oxygen compounds of nitrogen in the cryogenic conditions

Sulfide mining wastes, as well as the natural geochemical anomalies, represent an uncontrolled sources of heavy metals into the environment. As a result of a complex multifactorial process of chemical and biochemical weathering of ore minerals in these landscapes there is a formation of aggressive sulfuric acid solution (upto pH <1) promoting the mobilization of Fe, Cu, Zn and other elements [Nordstrom, 1991]. During the last decade a large number of works cover the development of geotechnical methods of migratory flows management in the fields of waste storing on the basis of experimental studies of the interaction of sulfide minerals with the components of the environment [Alekhin ,et al., 2006]. It is known that the processes of chemical weathering with atmospheric oxygen are limited by the activation phase О2 (Е = + 1.23 В) and noticeably accelerated in the presence of catalysts, whose role in the oxidative horizon of sulphide dumps along with ions, Fe, Cu is acted by nitrogen oxycompounds coming from atmosphere in the form of acid deposition (dry and wet) [Ptitsyn, et al., 2009]. From the point of view of thermodynamics, nitric oxides and products of their interaction with water have higher oxidation potential (Е = + 0.85  + 1.77 В) than univalent copper ions (Е = 0.15 В) and ferric (Е = + 0.77 В). The mechanism of catalysis is extremely complex and currently do not have details. During oxidation in the system there is a number of nitrogen compounds (NO, N2O3, NO2, N2O4, HNO2, NO2, HNO3, NO3, NO, NO2 etc.) with different catalytic activity and varying concentrations. According to numerous experimental studies kinetically most chemically responsive form is the nitrous acid and its dissociation products. At low concentrations (< 0.1 M) the activating effect of HNO2 exceeds the catalytic activity of all other nitrogen oxycompounds by several times. The complete opening of sulfides does not require significant amounts of activator, because the escaping nitric oxides are easily oxidized in the presence of oxygen, and again form nitric acid.

Forecasting of technogenic placer dynamics in the shore zone of the sea on the basis of numerical modeling: The case of the Val’kumei deposit

As natural placer and primary ore deposits are exhausted, the role of technogenic deposits is increasingly growing. In some cases, technogenic components accumulate in the shore zone of the shelf. The proposed numerical dynamic model is based on data concerning the technogenic tin deposit formed as a product of 50 years of operations at the Val’kumei Mining and Concentrating Combine, which disposed of tin ore flotation tailings in the coastal zone of the Chaun Gulf of the East Siberian Sea. The developed model describes adequately the current placer dynamics and forecasts a change in the morphology and geochemical parameters of a technogenic fan, opening the way to modeling behavior of natural geochemical anomalies in the coastal zone under conditions of active lithodynamics.

Role of recessive and dominant mutations in adaptation the genus Rana to recent biosphere

The populations of three anuran amphibian species (Amphibia, Anura) of the genus Rana (R. ridibunda Pall., R. arvalis Nilss. and R. temporaria L.) inhabiting the Yekaterinburg urban agglomeration were examined. The frequencies of two traits, morph striata and iris depigmentation, were estimated in these populations. The former trait, so-called morph striata, is phenotypically expressed as a light dorsomedial stripe. It is controlled by a dominant allele of autosomal diallelic gene striata in some species of Rana genus, exhibiting complete dominance. Striata individuals have a number of physiological features that confer them an advantage under conditions of natural and artificial geochemical anomalies. The second trait, iris depigmentation, is the result of a recessive mutation. The individuals homozygous for this trait have low viability. Thus, the dominant mutations promote rapid adaptation of their carriers. Conversely, the recessive mutations may reduce viability of an individual.

Metal content in river suspended particulate matter: data on Po River.

The present study summarizes the last ten years of literature on heavy metal distribution in Suspended Particulate Matter (SPM) and dissolved phase in the Po River (Italy). The work compares different methodologies employed to collect, concentrate and fractionate the samples. The importance of metal speciation as a function of particle size is underlined and two approaches to metal speciation in the colloidal fraction of Po River SPM are presented: Sedimentation Field-Flow Fractionation (SdFFF) and pH-dependent extractions. Finally, emphasis is placed on the need for comparison with a reference "natural background level" of the metal load in Po River particulate matter in order to determine the real human contribution to river pollution. The high values of some trace transition elements, such as Cr and Ni, have been compared with clay sediments around Ferrara and with bricks in historic buildings. The highly comparable natural concentration of these metals in Po fine sedimentary rocks and in historic brick buildings of Ferrara (XII-XVI centuries) can provide information on natural geochemical anomalies.

Heavy Metals in the Soil–Plant–Animal System in the Area of Natural Geochemical Anomaly

Heavy Metals in the Soil–Plant–Animal System in the Area of Natural Geochemical Anomaly