Evaluation of environmental contamination by toxic trace elements in Kazakhstan based on reviews of available scientific data

PGPR-driven phytoremediation and physiobiochemical response of Miscanthus × giganteus to stress induced by the trace elements

The effect of inoculation of Miscanthus × giganteus Greef et Deu by the plant growth promoting rhizobacteria (PGPRs) to the phytoremediation process and physio-biochemical plant's parameters was investigated in soil contaminated with the trace elements (TEs) from the Tekeli mining complex, Kazakhstan. Yeast Trichosporon sp. CA1, strains Rhizobium sp. Zn1-1, Shinella sp. Zn5-6, and Pseudomonas sp. CHA1-4, resistant to Zn and Pb, were isolated from the rhizosphere of M × g when the plant was cultivated in the same contaminated soil. Results illustrated that inoculation improved M × g adaptability to TEs toxicity by increasing the tolerance index to 2.9. The treatment enhanced the aboveground biomass yield by up to 163%, root biomass by up to 240%, chlorophyll content by up to 30%, and Chla/b ratio by up to 21%. Through M × g active growth and development, the peak activity of antioxidant enzymes was observed: activity of superoxide dismutase and glutathione reductase was induced, while the activity of catalase and ascorbate peroxidase was inhibited. Based on bioconcentration and translocation factors it was revealed that PGPRs selectively increased the uptake of TEs or stabilised them in the M × g rhizosphere. Inoculation with PGPRs increased the stabilization of Pb, V, Cr, Co, Ni, Cu, Cd, As, and Ba in the soil and plant tissues. Further research should focus on ex situ experiments using isolated PGPRs.

Optimal ranges of social-environmental drivers and their impacts on vegetation dynamics in Kazakhstan

Kazakhstan is part of the Eurasian Steppes, the world's largest contiguous grassland system. Kazakh grassland systems are largely understudied despite being historically important for agropastoral practices. These grasslands are considered vulnerable to anthropogenic activities and climatic variability. Few studies have examined vegetation dynamics in Central Asia owing to the complex impacts of moisture, climatic and anthropogenic forcings. A comprehensive analysis of spatiotemporal changes of vegetation and its driving factors will help elucidate the causes of grassland degradation. Here, we investigated the individual and pairwise interactive influences of various social-environmental system (SES) drivers on greenness dynamics in Kazakhstan. We sought to examine whether there is a relationship between peak season greenness and its drivers - spring drought, preceding winter freeze-thaw cycles, percent snow cover and snow depth - for Kazakhstan during 2000-2016. As hypothesized, snow depth and spring drought accounted for 60 % and 52 % of the variance in the satellite-derived normalized difference vegetation index (NDVI) in Kazakhstan. The freeze-thaw process accounted for 50 % of NDVI variance across the country. In addition, continuous thawing during the winter increased vegetation greenness. We also found that moisture and topographic factors impacted NDVI more significantly than socioeconomic factors. However, the impacts of socioeconomic drivers on vegetation growth were amplified when they interacted with environmental drivers. Terrain slope and soil moisture had the highest q-values or power of determinant, accounting for ~70 % of the variance in NDVI across the country. Socioeconomic drivers, such as crop production (59 %), population density (48 %), and livestock density (26 %), had significant impacts on vegetation dynamics in Kazakhstan. We found that most of the pairwise interactive influences of the drivers exhibited bi-factor enhancement, and the interaction between soil moisture and elevation was the largest (q = 0.92). Our study revealed the optimal ranges and tipping points of SES drivers and quantified the impacts of various driving factors on NDVI. These findings can help us identify the factors causing grassland degradation and provide a scientific basis for ecological protection in semiarid regions.

Phytoremediation of Soil Contaminated by Organochlorine Pesticides and Toxic Trace Elements: Prospects and Limitations of Paulownia tomentosa

Paulownia tomentosa (Thunb.) Steud is a drought-resistant, low-maintenance and fast-growing energy crop that can withstand a wide range of climatic conditions, provides a high biomass yield (approximately 50 t DM ha^-1 yr^-1), and develops successfully in contaminated sites. In Kazakhstan, there are many historically contaminated sites polluted by a mixture of xenobiotics of organic and inorganic origin that need to be revitalised. Pilot-scale research evaluated the potential of P. tomentosa for the phytoremediation of soils historically contaminated with organochlorine pesticides (OCPs) and toxic trace elements (TTEs) to minimise their impact on the environment. Targeted soils from the obsolete pesticide stockpiles located in three villages of Talgar district, Almaty region, Kazakhstan, i.e., Amangeldy (soil A), Beskainar (soil B), and Kyzylkairat (soil K), were subjected to research. Twenty OCPs and eight TTEs (As, Cr, Co, Ni, Cu, Zn, Cd, and Pb) were detected in the soils. The phytoremediation potential of P. tomentosa was investigated for OCPs whose concentrations in the soils were significantly different (aldrin, endosulfans, endrin aldehyde, HCB, heptachlor, hexabromobenzene, keltan, methoxychlor, and γ-HCH) and for TTEs (Cu, Zn, and Cd) whose concentrations exceeded maximum permissible concentrations. Bioconcentration (BCF) and translocation (TLF) factors were used as indicators of the phytoremediation process. It was ensured that the uptake and translocation of contaminants by P. tomentosa was highly variable and depended on their properties and concentrations in soil. Besides the ability to bioconcentrate Cr, Ni, and Cu, P. tomentosa demonstrated very encouraging results in the accumulation of endosulfans, keltan, and methoxychlor and the phytoextraction of γ-HCH (TLFs of 1.9-9.9) and HCB (BCFs of 197-571). The results of the pilot trials support the need to further investigate the potential of P. tomentosa for phytoremediation on a field scale.

Essential Trace Elements in Scalp Hair of Residents across the Caspian Oil and Gas Region of Kazakhstan

Most of the country’s oil and gas fields are situated in West Kazakhstan, mainly on the Caspian Sea coast, causing significant damage to the local environment and contributing to an imbalance in the trace element composition of the human body. The study is aimed to evaluate the relationship between the concentration of essential trace elements in scalp hair of the western Kazakhstan adult population and the remoteness of their residence from oil and gas fields. The concentration of essential trace elements (Co, Cu, Fe, I, Mn, Se, Zn) in the hair of 850 individuals aged 18−60 years was determined by inductively coupled plasma mass spectrometry. In residents of settlements located at a distance of >110 km from oil and gas fields, the concentration of Cu and I in hair was significantly higher than in those closer to 110 km (p < 0.001). The content of Cu and I were associated with the distance to oil and gas fields (0.072 (95% CI: 0.050; 0.094)) and (0.121 (95% CI: 0.058; 0.185)), respectively. We detected a significant imbalance in the distribution of some essential trace elements in residents’ scalp hair from the Caspian region of western Kazakhstan, living near oil and gas fields. The concentrations of Cu and I were significantly interrelated with the distance to oil and gas fields. The level of copper in the hair of both inhabitants of the area most remote from oil and gas facilities and the entire population of western Kazakhstan as a whole remains significantly low. The data obtained provide evidence of the possible impact of pollutants generated by the oil and gas facilities on a shortage of essential trace elements and associated subsequent health risks.

A review of water pollution arising from agriculture and mining activities in Central Asia: Facts, causes and effects

Central Asia is one of many regions worldwide that face severe water shortages; nevertheless, water pollution in this region exacerbates the existing water stress and increases the risk of regional water conflicts. In this study, we perform an extensive literature review, and the data show that water pollution in Central Asia is closely linked to human activities. Within the Asian Gold Belt, water pollution is influenced mainly by mining, and the predominant pollutants are heavy metals and radionuclides. However, in the irrigated areas along the middle and lower reaches of inland rivers (e.g., the Amu Darya and Syr Darya), water pollution is strongly associated with agriculture. Hence, irrigated areas are characterized by high concentrations of ammonia, nitrogen, and phosphorus. In addition, the salinities of rivers and groundwater in the middle and lower reaches of inland rivers generally increase along the flow path due to high rates of evaporation. Soil salinization and frequent salt dust storms in the Aral Sea basin further increase the pollution of surface water bodies. Ultimately, the pollution of surface water and groundwater poses risks to human health and deteriorates the ecological environment. To prevent further water pollution, joint monitoring of the surface water and groundwater quantity and quality throughout Central Asia must be implemented immediately.