Ni Contamination Research Articles

Contamination Characteristics and Source Apportionment of Potentially Toxic Elements in Soil around the Coal-fired Power Plant Using APCS-MLR and PMF Models

To investigate the characteristics and sources of potentially toxic elemental contamination in soils around the coal-fired power plant, we selected the soil around the Jingyuan power plant as the object of investigation. Thirty-six and 27 soil samples collected from the urban and farmland areas were analyzed for PTEs (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn), respectively. We employed the geoaccumulation index, single-factor pollution index, and improved Nemerow integrated pollution index to evaluate the contamination characteristics of PTEs, and combined correlation analysis with absolute principal component scores-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) receptor models were used to quantitatively analyze the pollution sources of PTEs. The results revealed that all the average concentrations of other soil metals around Jingyuan power plant exceeded their corresponding background values of Gansu Province, except for As, in agricultural soil, and Hg exhibited significant spatial non-homogeneity, and thus it was visibly affected by anthropogenic activities. The values of the single-factor pollution and geoaccumulation indices indicated that the soils of both sites were mainly contaminated with Cd, Cr, Ni, and Pb, and Hg contamination was reflected in wide areas for both sites. Additionally, the results of the improved Nemerow index demonstrated that the investigated soil was between moderately contaminated and heavily contaminated. Further, the comprehensive pollution degree of urban soil was higher than that of agricultural soil. Moreover, source apportionment revealed that PTEs in urban soil were derived from mixed sources of traffic activities and coal combustion, mixed sources of traffic activities and industrial and mining activities, and atmospheric deposition from industrial activities, with contribution rates of APCS-MLR of 35.2%, 25.1%, and 23.4%, respectively. The PMF contribution rates were 40.2%, 12.4%, and 47.7%, respectively. PTEs in agricultural soil were from one mixture source of industrial, mining, agricultural, and traffic sources, and the other mixed source was of traffic activities and coal combustion, with a APCS-MLR contribution rate of 40.3% and 35.9% and a contribution rate of PMF of 36.2% and 18.0%, respectively. In addition, another mixed source of agricultural activities and coal combustion was obtained using the PMF model, with a contribution rate of 48.5%.

An improved comprehensive model for assessing the heavy metals exposure towards waterbirds: A case report from Black-necked cranes (Grus nigricollis) in Caohai Wetland, China

Heavy metal contamination poses a significant environmental threat to wildlife on global scale, making accurate assessment of exposure risk crucial for conservation efforts, particularly for vulnerable species. Existing risk assessment models have been widely used, but their construction process lacks comprehensive considerations. In this study, we constructed an optimized health risk assessment model based on the well-established "Liu's model" and "ADI model", and applied the pollution allocation factor (AF) to accurately assess the risk of heavy metal exposure to wildlife. Our model was applied to assess exposure risk of heavy metal for the black-necked crane(Grus nigricollis), a flagship species in the alpine wetland ecosystem of Caohai Wetland. Soil, plant and black-necked crane fecal samples were collected from the Caohai Wetland and surrounding areas in Guizhou, China. We revealed varying degrees of As, Cd, Cr, Ni, Pb, and Zn contamination in soil and plants from different habitats, exceeding the background or plant limit values. This indicated that the black-necked crane and other waterbirds living in Caohai Wetland are suffering with the multi-elemental heavy metal contamination, especially in the gutterway and grassland. The exposure dose of As, Cd, Cr, Ni, Cu, and Zn toward black-necked cranes differed significantly in soil and plant pathways (P < 0.05). As, Cd, Cu, and Zn were mainly derived from plants consumption, while Cr and Ni originated from soil. Considering the contribution of soil and plant pathways to heavy metal exposure in black-necked cranes, the exposure doses of each elements calculated via food intake accounted for over half of the exposure calculated via feces (AF>0.5). The risk assessment model identified Cr and Pb were the highest risk elements for black-necked cranes, with exposure risk simulated through feces exceeding those through food. These findings suggested that current Liu's model may underestimate the effects of other pathways and medium. Therefore, we proposed a more comprehensive and accurate model for evaluating the exposure risk of black-necked cranes, incorporating AF to quantify the contribution of risk sources to black-necked cranes and understand their overall health risk. This model can serve as a useful tool for the conservation and habitat quality improvement of the black-necked cranes and other waterbirds.

Ecotoxicological risks of metals in the subsistence food garden soils of Watut River floodplains, Papua New Guinea.

Exorbitant concentrations of toxic metals in the soil from anthropogenic activities are environmental hazards and key health risk concerns to humans. The subsistence food garden soils have minimum anthropogenic interventions. The ecotoxicological risk potentials of the metals in subsistence food garden settings are unexplored. The metals (Cr, Cu, Pb, and Ni) concentration were assessed in the surface soil fractions (2mm and 0.2mm) of food gardens (N = 20) on the floodplains of Watut River, Papua New Guinea. The threshold limits, index of geo-accumulation (Igeo), contamination factor (CF), pollution load index (PLI), and potential ecological risk index (PERI) served as potential risk indicators of metals. Regardless of soil particle size, the descending order of median metals concentration was Cr > Cu > Ni > Pb. The concentration of Cu and Ni in the soil particles exceeded the WHO threshold limits in 100% and 50% of the food garden soils, respectively. Metal enrichment led to severe pollution in 100% gardens (Igeo > 5). Cr, Cu, and Ni contamination factors were > 1 in 95% of the food gardens. The PERI values indicated a lower ecological risk of the metals (PERI < 100). The median concentration of Cu, Igeo, and CF values for Cu in the 2mm soil particles were significantly greater than in 0.2mm. The results suggested exposure of subsistence food gardens soils to geogenic metal contamination and the need to carefully choose appropriate soil particle size for the soil health assessments.

Bioaccumulation and distribution of Pb, Ni, Zn and Fe in stinging nettle (Urtica dioica) tissues and heavy metal-contamination assessment in the industrial zone of smelter Ferronikeli (Drenas-Kosovo)

Here, we determined the concentrations of Pb, Ni, Zn and Fe in the soil and in vegetative organs of stinging nettle (Urtica dioica) collected from the banks of the Drenica River in the vicinity of the Ferronikeli smelter. The results were compared with samples collected from the banks 20 km (Shalë village) upriver. In addition, the bioaccumulation factor (BCF) and translocation factor (TF) were determined. Meanwhile, to evaluate the level of pollution in the study area was used the contamination factor (CF), potential ecological risk factor () and the potential ecological risk index (RI). The order of heavy metals according to their concentration in the soil samples at both sampling sites was as follows: Fe > Ni > Zn > Pb. Concentrations in excess of the limits allowed for soils in the samples collected in the vicinity of the smelter were recorded for Pb (173.13 mg kg−1), Zn (1217.48 mg kg−1), and Ni (1443.93 mg kg−1), while at the control site, Zn (270.82 mg kg−1) and Ni (375.47 mg kg−1) were found in excess concentrations. But lead (Pb) level was under allowed limit. The data showed that the stinging nettle is not a hyperaccumulator because BCF < 1 at both sites for all metals under study. Furthermore, analysis of the translocation factor (TFsteam/root) showed that at low of heavy metal concentrations, their mobility was higher (TF > 1). The lowest mobility (TF < 1) was observed at site I (Poklek), where the concentration of heavy metals was higher, except for Fe. The opposite was shown for mobility of metals from stems to leaves (TFleave/steam). The evaluation of CF showed that the area near the Ferronikeli smelter had low degree of Pb, moderate degree of Zn and considerable degree of Ni contamination. The values of RI indicate low potential ecological risk index.

Investigation of snow cover solid phase using total‐reflection x‐ray fluorescence method for an assessment of the environmental pollution

AbstractSnow cover is an important source of data for the study of environmental pollution due to its ability to accumulate atmospheric dust particles. A total reflection x‐ray fluorescence method (TXRF) was applied to assess the concentration levels of potentially toxic elements (As, Pb, Zn, Ni, Cu, Cr, V, Mn, and Sr) in samples of snow cover solid phase collected in suburban areas of the Irkutsk region with industrial activity. Suspension was chosen as an optimal sample preparation procedure for solid phases of snow samples obtained after melting and filtration. Results were compared with those obtained by wavelength‐dispersive x‐ray fluorescence spectrometry and atomic absorption spectrometry. Precision of TXRF results expressed by repeatability values was not exceeded 15% (n = 3) for most of the elements, and the trueness of the TXRF method expressed by recovery values was in the range of 87%–115% for concentration levels of 5.0–350 μg/g. Forty samples of snow cover solid phase were analyzed by TXRF method and results were compared with the background values. The investigation showed low contamination of the studied area by Pb, Cu, V, Mn, and Sr, medium contamination by Ni, As, and Cr, and high contamination by Zn. TXRF is advantageous in being rapid, cost‐efficient, and simple and can be used as a promising method for an assessment of environmental pollution.

Comparative metabolomic analysis reveals Ni(II) stress response mechanism of Comamonas testosteroni ZG2

The focus on the toxicity of nickel (Ni(II)) in animal and human cells has increased recently. Ni(II) contamination hazards to animals and humans can be reduced by bioremediation methods. However, one of the limitation of bioremediation bacteria in soil remediation is that they cannot survive in moderate and heavy contamination Ni(II)-contaminated environments. Therefore, the Ni(II) response mechanism of Comamonas testosteroni ZG2 which has soil remediation ability in high-concentration Ni(II) environment must be elucidated. The results demonstrated that the ZG2 strain can survive at 350 mg/L concentration of Ni(II), but the growth of ZG2 was completely inhibited under the concentration of 400 mg/L Ni(II) with significant alterations in the membrane morphology, adhesion behavior, and functional groups and serious membrane damage. Furthermore, the metabolic analysis showed that Ni(II) may affect the adhesion behavior and biofilm formation of the ZG2 strain by affecting the abundance of metabolites in amino acid biosynthesis, aminoacyl-tRNA biosynthesis, ABC transporter, and cofactor biosynthesis pathways, and inhibiting its growth. This study provides new evidence clarifying the response mechanism of Ni(II) stress in the ZG2 strain, thus playing a significant role in designing the strategies of bioremediation.

Spatial and temporal variations in the environmental and biological characteristics of the Turyanchay River basin, Azerbaijan

This is the first comprehensive examination of the Turyanchay River in Azerbaijan, focusing on water quality (WQ), contamination, and biodiversity at four different locations: Gabala, Agdash, Udjar and Zardab. The study analysed nutrient (nitrate, ammonium, phosphate) and metal/metalloid (Pb, Cu, Ni, Zn, Mn, Cr, Cd, Fe and Al) contamination levels, as well as the diversity of macrozoobenthos in the river, birds and vegetation. The chemical and biological oxygen demands (COD and BOD), including WQ index (WQI) were also determined for the river. The results showed no significant difference in the levels of nutrients, metal/metalloid, COD, BOD, WQI and macrozoobenthos diversity across different locations (p > .05). However, they revealed temporal fluctuations, with their highest levels being recorded during the warmer months (July and August) and the lowest during the colder months (March and November). The estimated WQI, ranging from 19.6 to 43.6, indicated that the water in the Turyanchay River is safe for household and consumption purposes. Up to 83 species of macrozoobenthos were identified, with Hydropsychidae and Chironomidae showing the highest species richness, followed by Coenagrionidae, Psychomyiidae, Ceratopogonidae, Baetidae, Naididae and Gammaridae. Eighteen bird species, consisting of 11 terrestrial and 7 aquatic birds, were recorded, with eight of these species belonging to the Order Charadriiformes. A total of 42 different plant species belonging to 17 families were identified in the Turyanchay River basin, with Fabaceae being the most widely distributed, followed by Asteraceae and Typhaceae. This study provides important baseline data for the Turyanchay River, offering insights into its freshwater environment and biodiversity, and should support future monitoring efforts.

Comprehensive assessment on groundwater quality, pollution characteristics, and ecological health risks under seasonal thaws: Spatial insights with Monte Carlo simulations

Groundwater pollution is a major environmental concern and may persist under diverse ecological conditions. This study describes the seasonal impacts on pollution characteristics coupled with the degree of human health risks in groundwater. For this purpose, a highly populated city of Pakistan, Lahore was planned and about 50 groundwater samples were collected during the summer and winter seasons in 2021 and 2022. Various physiochemical parameters (pH, EC, TDS, and hardness), cations, anions, and toxic metals (As, Cd, Co, Cr, Mn, Ni, and Pb) were analyzed to evaluate the seasonal impacts on the groundwater quality. Besides, a Monte Carlo simulation model and sensitivity analysis were performed to obtain a high-level accuracy in cancer risk estimation. Results revealed that physiochemical parameters, cations, and anions in most of the samples were within the WHO limit. However, the heavy metals concentration was higher in winter than in summer season. Most metals showed a significant spatial variability were found in older settlements and densely populated areas of the city for both seasons. Factor analysis (FA) and cluster analysis (CA) revealed a significant anthropogenic contribution to Ni, Co, Cd, Cu, Cr, and Pb contaminations in groundwater. Drinking water quality indices (DWQI) and heavy metal pollution indices (HMEI) points in both seasons revealed a poor to moderated pollution pattern. Pollution load index (PLI) and potential ecological risk index (PERI) indicated the medium pollution with low risks. Through Monte Carlo simulation at 95% confidence level revealed that carcinogenic risks associated with As, Cr, Cd, and Ni has exceeded from safer limits. Consequently, winter season was perceived more sensitive owing to the substantial increase of pollutants proclamation in groundwater and posturing a serious threat to humans. Hence, instant remedial actions are suggested to ensure safe drinking water.

Estimation of heavy metal soil contamination distribution, hazard probability, and population at risk by machine learning prediction modeling in Guangxi, China

Due to superposition of diverse pollution sources, soil heavy metal concentrations have been detected to exceed the recommended maximum permissible levels in many areas of Guangxi province, China. However, the heavy metal contamination distribution, hazard probability, and population at risk of heavy metals in the entire Guangxi province remain largely unclear. In this study, machine learning prediction models with different standard risk values determined according to land use types were used to identify high-risk areas and estimate populations at risk of Cr and Ni based on 658 topsoil samples from Guangxi province, China. Our results showed that soil Cr and Ni contamination derived from carbonate rocks was relatively serious in Guangxi province, and that their co-enrichment during soil formation was associated with Fe and Mn oxides and alkaline soil environment. Our established model exhibited excellent performance in predicting contamination distribution (R2 > 0.85) and hazard probability (AUC>0.85). Pollution of Cr and Ni exhibited a pattern of decreasing gradually from the central-west areas to the surrounding areas with the polluted area (Igeo>0) of Cr and Ni accounting for approximately 24.46% and 29.24% of total area in Guangxi province, respectively, but only 10.4% and 8.51% of total area was classified as Cr and Ni high-risk regions. We estimated approximately 1.44 and 1.47 million people were potentially exposed to the risk of Cr and Ni contamination, which were mainly concentrated in the Nanning, Laibin, and Guigang. These regions are main heavily-populated agricultural regions in Guangxi, and thus heavy metal contamination localization and risk control in these regions are urgent and essential from the perspective of food safety.

Exogenous abscisic acid fine-tunes heavy metal accumulation and plant’s antioxidant defence mechanism to optimize crop performance and secondary metabolite production in Trigonella foenum-graecum L. under nickel stress

Nickel (Ni) contamination of farming soil has become currently a recurring global menace to agriculture crop productivity. The purpose of the present study was to investigate the putative contributions of abscisic acid (ABA) to extemporize Ni tolerance in Trigonella foenum-graecum L. (fenugreek) plants. The outcomes of this study exposed that exogenous supplementation of ABA at 10, 20, 40 and 80 µM considerably enhanced the growth and physiological attributes of fenugreek under 80 mg Ni kg−1 soil, however, 40 µM of ABA exhibited the best results under normal and Ni-stressed conditions. ABA-mediated Ni tolerance was marked by reductions in Ni accumulation and consequent lowering of reactive oxygen species (ROS) like hydrogen peroxide and superoxide radicals. Contrarily, NO (nitric oxide) level increased in response to ABA application under Ni stress conditions, accompanied by promoted antioxidant activities through improved levels of secondary metabolites, proline, and perked-up ROS-detoxification enzymes activities. Exogenous ABA at 40 µM concentration applied to Ni-exposed plants (80 mg Ni kg−1 soil) improved the total content of alkaloids, phenolics, flavonoids and tannins by 14.3%, 10.2%, 15.4% and 7.0%, respectively, over Ni-stressed plants alone. Additionally, seed trigonelline content imparting several pharmacological actions to the fenugreek plant exhibited a remarkable escalation upto 3.6 and 2.6 mg g−1 DW under ‘40 µM ABA’ and ‘40 µM ABA + 80 mg Ni kg−1 soil’ treatments, respectively. The findings of the study suggest that ABA plays a key role in enhancing the overall performance of the fenugreek crop under excessive Ni stress.

Risk Assessment of Trace Metals Using Chemical Speciation, Bioavailability, and Cluster Analysis Around Wadi EL Bey (Gulf of Tunis, Tunisia)

ABSTRACT The Wadi El Bey is one of the most vulnerable areas to pollution in the northeast of Tunisia, altered by anthropogenic and natural processes. This study uses the Community Bureau of Reference (BCR) approach and statistical tools, particularly the student’s t-test and the cluster analysis, to evaluate the danger of metals zinc (Zn), nickel (Ni), lead (Pb), cadmium (Cd), and copper (Cu) pose. This work is to assess the long-term evolution and mobility of heavy metals in the core soils of the Wadi El Bey River Bed. Heavy metals in SC1 followed the descending order Fe>Cu>Zn>Ni>Pb>Cd and in SC2 it was Fe>Cu>Zn>Ni>Cd>Pb. The (BCR) procedure showed that in soil cores SC1 and SC2, Ni was mainly associated with the exchangeable fractions (F1). However, the Zn and Cu were linked to the residual fractions (F4). The student’s t-test confirmed that the difference in vertical distribution between the SC1 and SC2 of Zn and Pb is statistically significant (p-value<.05) contrary to Ni (P = .06), Cd (P = .79), Cu (P = .38) demonstrated a common origin for these metals in the Wadi El Bey. The cluster analysis revealed that pH was the main responsible factor influencing the migration of Cu, Ni, and Zn toward the labile fractions in SC1. Whereas the total organic carbon influenced the Zn fixation in the most stable fraction in SC2. The use of pollution indices showed strong contamination by Ni, Cu, and Cd and moderate contamination by Zn and Pb. The risk assessment code (RAC) showed that Zn and Cu had a low to medium risk whereas medium to high risk for Ni. For better management and better control of heavy metal pollution in ecosystems with intermittent regimes, we advise a tertiary treatment of wastewater before evacuating it in Wadi el Bey.

Using Fe biofortification strategies to reduce both Ni concentration and oral bioavailability for rice with high Ni

Due to naturally high Ni or soil Ni contamination, high Ni concentrations are reported in rice, raising a need to reduce rice Ni exposure risk. Here, reduction in rice Ni concentration and Ni oral bioavailability with rice Fe biofortification and dietary Fe supplementation was assessed using rice cultivation and mouse bioassays. Results showed that for rice grown in a high geogenic Ni soil, increases in rice Fe concentration from ∼10.0 to ∼30.0 μg g–1 with foliar EDTA-FeNa application led to decreases in Ni concentration from ∼4.0 to ∼1.0 μg g–1 due to inhibited Ni transport from shoot to grains via down-regulated Fe transporters. When fed to mice, Fe-biofortified rice was significantly (p < 0.01) lower in Ni oral bioavailability (59.9 ± 11.9% vs. 77.8 ± 15.1%; 42.4 ± 9.81% vs. 70.4 ± 6.81%). Dietary amendment of exogenous Fe supplements to two Ni-contaminated rice samples at 10–40 μg Fe g–1 also significantly (p < 0.05) reduced Ni RBA from 91.7% to 61.0–69.5% and from 77.4% to 29.2–55.2% due to down-regulation of duodenal Fe transporter expression. Results suggest that the Fe-based strategies not only reduced rice Ni concentration but also lowered rice Ni oral bioavailability, playing dual roles in reducing rice-Ni exposure.

Investigation and comparative analysis of ecological risk for heavy metals in sediment and surface water in east coast estuaries of India

The sediments and surface water from 8 stations each from Dhamara and Paradeep estuarine areas were sampled for investigation of heavy metals, Cd, Cu, Pb, Mn, Ni, Zn, Fe, and Cr contamination. The objective of the sediment and surface water characterization is to find the existing spatial and temporal intercorrelation. The sediment accumulation index (Ised), enrichment index (IEn), ecological risk index (IEcR) and probability heavy metals (p-HMI) reveal the contamination status with Mn, Ni, Zn, Cr, and Cu showing permissible (0 ≤ Ised ≤ 1, IEn ˂ 2, IEcR ≤ 150) to moderate (1 ≤ Ised ≤ 2, 40 ≤ Rf ≤ 80) contamination. The p-HMI reflects the range from excellent (p-HMI = 14.89-14.54) to fair (p-HMI = 22.31-26.56) in off shore stations of the estuary. The spatial patterns of the heavy metals load index (IHMc) along the coast lines indicate that the pollution hotspots are progressively divulged to trace metals pollution over time. Heavy metal source analysis coupled with correlation analysis and principal component analysis (PCA) was used as a data reduction technique, which reveals that the heavy metal pollution in marine coastline might originate from redox reactions (FeMn coupling) and anthropogenic sources.

Acceptable Concentrations of Cu and Ni in Corrosion Resistance of Mg–6 mass% Zn Alloy

Cu and Ni impurities in Mg alloys are deleterious contaminants that reduce the corrosion resistance of the alloy. Mg2Cu and Mg2Ni precipitates can cause significant anodic dissolution of the Mg matrix, owing to their potential difference. Suppression of these phases can prevent the deterioration of corrosion resistance. The neutralization of these impurities through the formation of Mg–Zn intermetallic phases has been studied, because the atomic radii of Cu and Ni are similar to that of Zn. As a result, the MgZn2 phase may precipitate during the rapid cooling that occurs during the solidification of the Mg–6 mass% Zn alloy, and introduce substitutional impurity atoms in the crystal lattice. Mg(Zn, Cu)2 and Mg(Zn, Ni)2 phases can be formed instead of Mg2Cu and Mg2Ni, in the presence of both of Zn and these impurities. The microstructures and corrosion properties of the Mg–6 mass% Zn alloy with various Cu or Ni concentrations are investigated in this work. The Cu and Ni impurities are concentrated into MgZn2 phase in the Mg–6 mass% Zn alloy without Mg2Cu or Mg2Ni formation when the concentrations of these impurities are within acceptable limits. Consequently, the corrosion rate of the Mg–6 mass% Zn alloy with 1.4 mass% Cu or 0.25 mass% Ni is almost the same as that of the alloy without Cu and/or Ni contaminations.

Heavy metals accumulation in soil and uptake by barley (Hordeum vulgare) irrigated with contaminated water

Impacts of nine heavy metals (Cd, Cr, Cu, Ni, Pb, K, Fe, Mn, and Zn) contamination in irrigation water on the soil, shoots, and roots of barely were investigated. Due to freshwater shortages, the use of available and inexpensive urban wastewater with input from local industrial factories containing heavy metals in irrigation is still practiced in the Middle East including Palestine. Barely was grown in plastic pots filled with sandy soil irrigated with simulated treated wastewater during two growing seasons. The metal treatments investigated include one, three, nine, and 15 multiples of the average metal content of treated effluent. Results showed that (i) Barley showed similar growth responses but different metal uptake patterns, (ii) Cd, Fe, Pb, and Zn in roots and shoots of barley were higher than WHO permissible levels, (iii) all metals accumulated in the soil had lower content than WHO permissible levels, (iv) The average value of enrichment factor (EF) for most heavy metals used was around unity indicating poor enrichment to soil and translocation to roots and shoots, (v) The highest Translocation factor (TF = 57.8) and Bioconcentration Factor (BCF = 126.8) was observed for K indicating its role in enhancing barley's tolerance to drought and its effectiveness in using barley in phytoremediation, and (vi) Barley growth and development and soil quality parameters were significantly affected by repetitive and increased irrigation with wastewater containing heavy metals.

Determination of conditioning factors for mapping nickel contamination susceptibility in groundwater in KanchanaburiProvince, Thailand, using random forest and maximum entropy.

Groundwater pollution from nickel (Ni) has been a severe concern in Kanchanaburi Province, Thailand. Recent assessments revealed that theNi concentration in groundwater, particularly in urban areas, often exceeded the permissible limit. The challenge for groundwater agencies is therefore to delineate regions with high susceptibility to Ni contamination. In this study, a novel modeling approach was applied to a dataset of 117 groundwater samples collected from Kanchanaburi Province between April and July 2021. Twenty site-specific initial variables were considered as influencing factors to Ni contamination. The Random Forest (RF) algorithm with Recursive Feature Elimination (RFE) function was used to select the fourteen most influencing variables. These variables were then used as input features to train a ME model to delineate the Ni contamination susceptibility at a high confidence (Area Under the Curve (AUC) validation value of 0.845). Ten input variables of the altitude, geology, land use, slope, soil type, distance to industrial areas, distance to mining areas, electric conductivity, oxidation-reduction potential, and groundwater depth were discovered in the most explaining the variation of spatial Ni contamination at very high (95.47 km2) and high (86.65 km2) susceptibility. This studydevises the novel machine learning approach to identify the conditioning factors and map Ni contamination susceptibility in the groundwater, which provides a baseline dataset and reliable methods for the development of a sustainable groundwater management strategy.

Phytoremediation Potential of Native Plant Species in Mine Soils Polluted by Metal(loid)s and Rare Earth Elements.

Mining activity has an adverse impact on the surrounding ecosystem, especially via the release of potentially toxic elements (PTEs); therefore, there is an urgent need to develop efficient technologies to remediate these ecosystems, especially soils. Phytoremediation can be potentially used to remediate contaminated areas by potentially toxic elements. However, in soils affected by polymetallic contamination, including metals, metalloids, and rare earth elements (REEs), it is necessary to evaluate the behavior of these toxic elements in the soil-plant system, which will allow the selection of the most appropriate native plants with phytoremediation potential to be used in phytoremediation programs. This study was conducted to evaluate the level of contamination of 29 metal(loid)s and REEs in two natural soils and four native plant species (Salsola oppositifolia, Stipa tenacissima, Piptatherum miliaceum, and Artemisia herba-alba) growing in the vicinity of a Pb-(Ag)-Zn mine and asses their phytoextraction and phytostabilization potential. The results indicated that very high soil contamination was found for Zn, Fe, Al, Pb, Cd, As, Se, and Th, considerable to moderate contamination for Cu, Sb, Cs, Ge Ni, Cr, and Co, and low contamination for Rb, V, Sr, Zr, Sn, Y, Bi and U in the study area, dependent of sampling place. Available fraction of PTEs and REEs in comparison to total concentration showed a wide range from 0% for Sn to more than 10% for Pb, Cd, and Mn. Soil properties such as pH, electrical conductivity, and clay content affect the total, available, and water-soluble concentrations of different PTEs and REEs. The results obtained from plant analysis showed that the concentration of PTEs in shoots could be at a toxicity level (Zn, Pb, and Cr), lower than toxic but more than sufficient or natural concentration accepted in plants (Cd, Ni, and Cu) or at an acceptable level (e.g., V, As, Co, and Mn). Accumulation of PTEs and REEs in plants and the translocation from root to shoot varied between plant species and sampling soils. A. herba-alba is the least efficient plant in the phytoremediation process; P. miliaceum was a good candidate for phytostabilization of Pb, Cd, Cu, V, and As, and S. oppositifolia for phytoextraction of Zn, Cd, Mn, and Mo. All plant species except A. herba-alba could be potential candidates for phytostabilization of REEs, while none of the plant species has the potential to be used in the phytoextraction of REEs.

Thermal modulation of mitochondrial function is affected by environmental nickel in rainbow trout (Oncorhynchus mykiss)

In this study, we investigated the combined effects of temperature and nickel (Ni) contamination on liver mitochondria electron transport system (ETS) enzymes, citrate synthase (CS), phospholipid fatty acid composition and lipid peroxidation in rainbow trout (Oncorhynchus mykiss). Juvenile trout were acclimated for two weeks to two different temperatures (5˚C and 15˚C) and exposed to nickel (Ni; 520 μg/L) for three weeks. Using ratios of ETS enzymes and CS activities, our data suggest that Ni and an elevated temperature acted synergistically to induce a higher capacity for reduction status of the ETS. The response of phospholipid fatty acid profiles to thermal variation was also altered under nickel exposure. In control conditions, the proportion of saturated fatty acids (SFA) was higher at 15˚C than at 5˚C, while the opposite was observed for monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA). However, in nickel contaminated fish, the proportion of SFA was higher at 5˚C than at 15˚C, while PUFA and MUFA followed the opposite direction. A higher PUFA ratio is associated with higher vulnerability to lipid peroxidation. Thiobarbituric Acid Reactive Substances (TBARS) content was higher when the PUFA were in higher proportions, except for Ni-exposed, warm-acclimated fish, in which we reported the lowest level of TBARS but the highest proportion of PUFA. We suspect that the interaction of nickel and temperature on lipid peroxidation is due to their synergistic effects on aerobic energy metabolism, as supported by the decrease in the activity of complex IV of the ETS enzyme activity in those fish, or on antioxidant enzymes and pathways. Overall, our study demonstrates that Ni exposure in heat-challenged fish can lead to the remodelling of the mitochondrial phenotype and potentially stimulate alternative antioxidant mechanisms.

Synergistic mitigation of nickel toxicity in pepper (Capsicum annuum) by nitric oxide and thiourea via regulation of nitrogen metabolism and subcellular nickel distribution.

Nickel (Ni) contamination hinders plant growth and yield. Nitric oxide (NO) and thiourea (Thi) aid plant recovery from heavy metal damage, but their combined effects on pepper (Capsicum annuum ) plant tolerance to Ni stress need more study. Sodium nitroprusside (0.1mM, SNP) and 400mgL-1 Thi, alone and combined, were studied for their impact on pepper growth under Ni toxicity. Ni stress reduces chlorophyll, PSII efficiency and leaf water and sugar content. However, SNP and Thi alleviate these effects by increasing leaf water, proline and sugar content. It also increased the activities of superoxide dismutase, catalase, ascorbate peroxidase and peroxidase. Nickel stress lowered nitrogen assimilation enzymes (nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase) and protein content, but increased nitrate, ammonium and amino acid content. SNP and Thi enhanced nitrogen assimilation, increased protein content and improved pepper plant growth and physiological functions during Ni stress. The combined treatment reduced Ni accumulation, increased Ni in leaf cell walls and potentially in root vacuoles, and decreased Ni concentration in cell organelles. It effectively mitigated Ni toxicity to vital organelles, surpassing the effects of SNP or Thi use alone. This study provides valuable insights for addressing heavy metal contamination in agricultural soils and offers potential strategies for sustainable and eco-friendly farming practices.

Content of Cadmium and Nickel in Soils and Assimilatory Organs of Park Woody Species Exposed to Polluted Air.

The rising level of pollutant emissions is becoming one of the most pressing environmental problems of our time. Therefore, this work is focused on evaluating Cd and Ni contamination of soils and assimilatory organs of two native (Acer platanoides L., Taxus baccata L.) and two non-native (Negundo aceroides Moench, Thuja occidentalis L.) woody species in urban parks of SW Slovakia. The contents of Cd and Ni in soils were determined by the AAS method and, in the assimilatory organs of trees, by the AAS-ETA method. The studied soils (Fluvisol, Phaeozem) have neutral soil reactions and a moderate organic matter content. Cadmium soil contamination is considerable to very high; in the case of Ni, it is moderate to low. Cadmium levels detected in leaves were 31% higher than in needles, while Ni levels were 27% lower. Significant ecological factors in relation to the studied woody species were evaluated using PCA. The first three principal components of PCA significantly correlated with Cd (PC1) and Ni (PC3) contents in soils and Cd content in assimilatory organs (PC2), thus suggesting that these elements could especially originate from industrial and vehicular sources. Knowledge of the factors affecting the accumulation of risk elements in the assimilatory organs of park woody species can be successfully used, especially in the assessment of the quality of the urban environment and the selection of suitable cultivars for planting in areas with air pollution.