Natural Background Levels Research Articles

Seasonal variations of vitamins A, E and carotenoids in eelpout (Zoarces viviparus) from a Danish fjord, in relation to reproductive cycle

Retinoids (vitamin A) and tocopherols (vitamin E) are essential for key biological functions in vertebrates, including cell growth, cell death and differentiation, embryonic development, reproduction and vision. In fish, however, much less is known about the retinoid functions, although retinoic acid has been shown to be involved in embryonic development. In this study, we quantified the levels of different retinoids, carotenoids and vitamin E in various tissues of both adult and embryos of the viviparous fish eelpout (Zoarces viviparus). Our results demonstrate clear seasonal differences in the levels of these vitamins in the liver of the female fish as well as in its ovarian tissues, eggs and/or embryos. Overall, this study is a baseline assessment and describes the annual variations in the vitamin status by comparing the tissue distribution of retinoids, carotenoids and vitamin E. This baseline study investigates the natural background levels of these compounds and relates their seasonal fluctuations to the reproductive cycle in the viviparous eelpout. The results of this study strengthen the current evidence base necessary to understand retinoid pathways during fish development. This understanding is crucial for utilizing retinoid composition in fish as a biological response to exposure to environmental pollution with hazardous substances in the marine environment.

Chemical composition of sediment and macrozoobenthos of small urban lakes, the Republic of Karelia, Russia

Assessing the benthic communities in water bodies under increasing anthropogenic pressure seems to be an urgent task of scientific research aimed at short-term and long-term monitoring of water bodies. This study focuses on the chemical composition of modern sediment and the current state of macrozoobenthos of small lakes in the Republic of Karelia (Kitaiskoe and Plotichie) influenced by anthropogenic factors. It was discovered that the lakes of Medvezhyegorsk have a higher concentration of heavy metals (such as lead (Pb), cadmium (Cd), molybdenum (Mo), and antimony (Sb),) compared to the Earth’s crust and natural background levels. The current study established the significant impact of industry and transportation on the movement and build up of pollutants in these lakes. The qualitative and quantitative parameters analysed for the benthic communities in the littoral and profundal zones included the species diversity, the structure of dominant species, and their percentage in the samples. According to the level of macrozoobenthos development, both reservoirs (lakes) were classified as mesotrophic, and according to the values of the chironomid index “K” as moderately polluted. The Pantle–Buck method (saprobic index) showed that the lakes can be classified as polluted (water quality class 4). Macrozoobenthos groups most tolerant to environmental conditions, for example, Chironomidae larvae, prevailed in the studied urban lakes. The economic development of the lakes leads to ecosystem transformation and long-term eutrophication over time affecting the biotic indicators of surface water quality. The results obtained can serve as a basis for complex environmental monitoring of the urbanized territories in the taiga zone.

Analysis of Posidonia oceanica's Stress Factors in the Marine Environment of Tremiti Islands, Italy.

Posidonia oceanica significantly contributes to the health of oceans and coastal areas; however, its progressive decline is becoming an increasing source of concern. The present preliminary study aims to assess the chemical parameters that describe the state of preservation of the aforementioned plant meadows located in the Tremiti Islands archipelago. To better understand the plants' response to external factors, the emission of biogenic volatile organic compounds (BVOCs) was investigated using Posidonia oceanica as a biological indicator. Subsequently, the heavy metal concentrations (Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Sn, Ti, Tl, V, Zn) in sediments, leaves, and seawater were determined and pollution indicators were calculated to assess the deviation from the natural background levels of sediments. The dimethyl sulfoniopropionate (DMSP) to dimethyl sulfoxide (DMSO) ratio was calculated to evaluate the oxidative stress levels in the meadows because the DMSP naturally present in Posidonia oceanica is oxidized to DMSO and decreases the ratio of DMSP/DMSO. BVOC analysis revealed dimethyl sulphide (DMS) as the most abundant molecule. Morphological features led to variations in metal concentrations across sampling sites, with sheltered bays displaying a higher metal content. Degradation is indicated by a greater DMSO content in the outer leaves. In accordance with the metal content, the bioindicator ratio confirms greater degradation on the south side, which aligns with increased oxidative stress.

Natural background level, source apportionment and health risk assessment of potentially toxic elements in multi-layer aquifers of arid area in Northwest China

Groundwater contaminated by potentially toxic elements has become an increasing global concern for human health. Therefore, it is crucial to identify the sources and health risks of potentially toxic elements, especially in arid areas. Despite the necessity, there is a notable research gap concerning the sources and risks of these elements within multi-layer aquifers in such regions. To address this gap, 54 phreatic and 24 confined groundwater samples were collected from an arid area in Northwest China. This study aimed to trace the sources and evaluate the human health risks of potentially toxic elements by natural background level (NBL), positive matrix factorization (PMF) model, and health risk model. Findings revealed exceeding levels of potentially toxic elements existed in phreatic and confined aquifers. Source apportionment and NBL results indicated that mineral dissolution, evaporation, redox reactions, and human activities were the main factors for elevated concentrations of potentially toxic elements. High Fe and Mn concentrations were attributed to reduction environments, while F accumulation resulted from slow runoff, and irrigation from the Yellow River. Due to high F levels, more than one-third of groundwater samples (phreatic: 33.14 %, confined: 56.22 %) posed non-carcinogenic health risks to population groups. Adults displayed higher carcinogenic risks (phreatic: 19.47 %, confined: 34.16 %) than infants (phreatic: 0 %, confined: 0 %) and children (phreatic: 1.26 %, confined: 7.97 %) owing to the toxic elements of Cr. The confined aquifer presented greater health risks than the phreatic aquifer. Consequently, controlling the levels of F and Cr in multi-layered aquifers is key to reducing health risks. These findings provide valuable insights into protecting groundwater from contamination by potentially toxic elements in multi-layered aquifers worldwide.

Elevated Heavy Metal(loid) Blood and Feather Concentrations in Wetland Birds from Different Trophic Levels Indicate Exposure to Environmental Pollutants

The research assessed the exposure to total mercury (THg), lead (Pb), and arsenic (As) in Colombian wetland species of different trophic levels Platalea ajaja, Dendrocygna autumnalis and Nannopterum brasilianus. The results show high THg blood levels in P. ajaja (811.00 ± 349.60 µg L–1) and N. brasilianus (209.50 ± 27.92 µg L–1) with P. ajaja possibly exhibiting adverse effects. Blood Pb concentration was high in D. autumnalis (212.00 ± 208.10 µg L–1) and above the threshold for adverse effects, suggesting subclinical poisoning. Levels of blood As were below the assumed threshold for detrimental effect (20 μg L−1). The mean concentration of feather THg was below the assumed natural background levels (5 µg g−1) for all three species. Feather Pb levels exceeded the levels for assumed threshold effects in all sampled N. brasilianus (7.40 ± 0.51 µg g–1). Results for feather As concentration were below the threshold for adverse impacts in all species, although a positive correlation between As and THg concentrations was detected in P. ajaja feathers. The overall results could help understand how metal(loid)s biomagnify through trophic levels and how wetland species may serve as environmental indicators. By exploring the interactions of metal(loid)s within different matrices and body, this study offers insights into the dynamics of contaminant accumulation and distribution in the environment. This concept can be applied to wetlands worldwide, where bird species can serve as indicators of ecosystem health and the presence of contaminants such as heavy metals and metalloids.

Natural background levels and driving factors of aluminum in shallow groundwater of an urbanized delta: Insight from eliminating anthropogenic-impacted groundwaters.

Knowledge on natural background levels (NBLs) of aluminum (Al) in groundwater can accurately assess groundwater Al contamination at a regional scale. However, it has received little attention. This study used a combination of preselection and statistic methods consisting of the oxidation capacity and the boxplot iteration methods to evaluate the NBL of shallow groundwater Al in four groundwater units of the Pearl River Delta (PRD) via eliminating anthropogenic-impacted groundwaters and to discuss driving factors controlling high NBLs of Al in groundwater in this area. A total of 280 water samples were collected, and 18 physico-chemical parameters including Redox potential, dissolved oxygen, pH, total dissolved solids, HCO3 -, NH4 +, NO3 -, SO4 2-, Cl-, NO2 -, F-, K+, Na+, Ca2+, Mg2+, Fe, Mn, and Al were analyzed. Results showed that groundwater Al NBLs in groundwater units A-D were 0.11, 0.16, 0.15, and 0.08 mg/L, respectively. The used method in this study is acceptable for the assessment of groundwater Al NBLs in the PRD, because groundwater Al concentrations in various groundwater units in residual datasets were independent of land-use types, but they were opposite in the original datasets. The dissolution of Al-rich minerals in sediments/rocks was the major source for groundwater Al NBLs in the PRD, and the interaction with Al-rich river water was secondary one. The high groundwater Al NBL in groundwater unit B was mainly attributed to the acid precipitation and the organic matter mineralization inducing the release of Al in Quaternary sediments. By contrast, the high groundwater Al NBL in groundwater unit C mainly was ascribed to the release of Al complexes such as fluoroaluminate from rocks/soils into groundwater induced by acid precipitation, but it was limited by the dissolution of Mg minerals (e.g., dolomite) in aquifers. This study provides not only useful groundwater Al NBLs for the evaluation of groundwater Al contamination but also a reference for understanding the natural geochemical factors controlling groundwater Al in urbanized deltas such as the PRD. PRACTITIONER POINTS: The natural background level (NBL) of groundwater aluminum in the Pearl River Delta (PRD) was evaluated. The dissolution of aluminum-rich minerals in sediments/rocks was the major source for groundwater aluminum NBLs in the PRD. The acid precipitation and organic matter mineralization contribute to high groundwater Al NBL in the groundwater unit B. The acid precipitation contributes to high groundwater Al NBL in the groundwater unit C, while dissolution of magnesium minerals limits it.

Hydrochemie podzemní vody Pražského hradu a okolí

The study examines the groundwater around Prague Castle as an example of an extreme urban environment that has been influenced by human activity since the Neolithic period. The long-term human activity, including several still-functioning drainage adits, resulted in a number of aggradation and degradation processes that have significantly impacted the groundwater regime. Furthermore, building development, particularly large-scale concrete structures, has had a notable effect on groundwater chemistry. This paper presents results of available archival chemical analyses from the area of interest (Fig. 1), along with our own groundwater chemical analyses. The results of recovery test in the anthropogenic alluvium well underneath the courtyard III of Prague Castle (Weiss et al. 2024) indicate that the transmissivity of saturated alluvium is low (8–10 m2/day). However, it is reasonable to assume a higher transmissivity for the entire area. The clayey anthropogenic alluvium near the surface likely has a much lower permeability than the underlying fractured zone of the Letná Formation made of shales (Late Ordovician). Field reconnaissance in the drainage adits indicates that groundwater flows directly from the historic alluvium (presence of bones and other organic remains) into the Ordovician strata. The existence of a clay aquitard, as mentioned by some authors (e.g. Kos 1965), between the historical alluvium and the underlying Ordovician is thus unlikely. The analysed water samples from selected objects can be classified into three distinct groups based on their pH levels: slightly acidic (precipitation water, and the well in the St. George’s Convent – V4), neutral (majority of samples), and alkaline (the environment underneath the courtyard III of Prague Castle). Slightly acidic pH level only applies to samples from precipitation or probable seepage (V4). The concentration of Cl- in the majority of the analysed groundwater samples is higher than the natural background level of around 8–10 mg/l, which indicates an anthropogenic source. The major source of these ions in the area is likely the use of NaCl to salt roads and sidewalks during the winter months, which has been a common practice for decades. The overall analysis of the studied samples identified two main hydrochemical types of water: Type A and Type B. Type A is represented by moderately alkaline water that is rich in sulphate and calcium/magnesium. Type B, on the other hand, is represented by strongly alkaline water rich in hydrogencarbonate and calcium, found mainly under the courtyard III of Prague Castle, which stands on a concrete structure. Type A is the predominant type and is typical of water originating in the pyrite-bearing shales of the Letná Formation. The high sulphate content of these waters may cause “sulphate attack” of concrete, leading to its decomposition and thus affecting the durability of building structures. This study provides valuable insights into groundwater chemistry in urban environments that can be applied to other similar sites.

Understanding arsenic and manganese enrichment in the aquifers of the Ghaghara river basin, Middle Gangetic Plain (MGP), India: A multivariate statistical, compositional data analysis (CoDA), and receptor model approach

The focus of this study was to comprehend the spatial distribution, source apportionment, evaluation of natural background level (NBL), and mobilization mechanisms of arsenic (As) and manganese (Mn) in the Ghaghara river basin, located in the middle Gangetic plain (MGP) of India. A combination of analytical tools was employed, including multivariate statistical analysis (MSA), correlation analysis, and receptor models such as positive matrix factorization (PMF) and principal component analysis-multi linear regression (PCA-MLR). Taking into consideration the compositional constraints of the geochemical data, compositional data analysis (CoDA) methods were applied on the raw data prior to the correlation analysis and MSA. The results of MSA, correlation analysis and receptor models showed that major ion chemistry and As, Mn enrichment in groundwater were largely controlled by carbonate weathering, Fe and Mn oxyhydroxides dissolution. Anthropogenic activities, such as the infiltration of dissolved organic matter-rich water from local surface water bodies used as dumping sites and the infiltration of fertilizer-rich water from agricultural lands, were found to notably impact the groundwater geochemistry and release of As in the research area. The lower NBL of As (5.92 μg/L) compared to its mean concentrations (17.9 μg/L) in the study area also indicated that the rate of As release in groundwater through natural processes was comparatively low but various anthropogenic activities operating in the study region possibly acted as a trigger for the mobility of As from the mineral phases of the subsurface sediments. This study also highlighted the significance of applying CoDA techniques on geochemical data prior to statistical analysis, and the importance of receptor models, to better understand the nature and contribution of various natural and anthropogenic processes governing the hydrochemistry of groundwater in the alluvial aquifers.

Natural background levels, source apportionment and health risks of potentially toxic elements in groundwater of highly urbanized area

Identifying the natural background levels (NBLs), threshold values (TVs), sources and health risks of potentially toxic elements in groundwater is crucial for ensuring the water security of residents in highly urbanized areas. In this study, 96 groundwater samples were collected in urban area of Sichuan Basin, SW China. The concentrations of potentially toxic elements (Li, Fe, Cu, Zn, Al, Pb, B, Ba and Ni) were analyzed for investigating the NBLs, TVs, sources and health risks. The potentially toxic elements followed the concentration order of Fe > Ba > B > Al > Zn > Li > Cu > Ni > Pb. The NBLs and TVs indicated the contamination of potentially toxic elements mainly occurred in the northern and central parts of the study area. The Positive Matrix Factorization (PMF) model identified elevated concentrations of Fe, Al, Li, and B were found to determine groundwater quality. The primary sources of Fe, Al, Pb, and Ni were attributed to the dissolution of oxidation products, with Fe additionally affected by anthropogenic reduction environments. Li and B were determined to be originated from the weathering of tourmaline. High levels of Ni and Cu concentrations were derived from electronic waste leakage, while excessive Ba and Zn were linked to factory emissions and tire wear. The reasonable maximum exposure (RME) of hazard index (HI) was higher than safety standard and reveal the potential health risks in the southwestern study area. Sensitivity analysis demonstrated the Li concentrations possessed the highest weight contributing to health risk. This study provides a valuable information for source-specific risk assessments of potentially toxic elements in groundwater associated with urban areas.

Characterization of heavy metal contamination in wetland sediments of Bosten lake and evaluation of potential ecological risk, China

In November 2023, twenty-two sediment samples were collected from the Bosten Lake wetland in Xinjiang to determine the concentrations of eight heavy metals: arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn). This data was used to assess heavy metal contamination and potential ecological risks in the sediments using the Pollution Load Index (PLI) and the Potential Ecological Risk Index (RI). Additionally, multivariate statistical analysis and Positive Matrix Factorization (PMF) were employed to elucidate potential sources and their contributions to contamination. The following are the main conclusions: (1) average concentrations of Zn, Cd, Cr, Pb, and Hg in the sediments surpassed Xinjiang soil background levels by factors of 1.01, 3.58, 1.32, 1.94, and 1.53, respectively. (2) Sediments demonstrated severe pollution with Cd, slight pollution with Zn, Cr, Pb, and Hg, while Cu and Ni indicated mild pollution and As showed non-polluted levels. The overall PLI average (1.01) suggested slight contamination. (3) The descending order of average single ecological risk values were Cd, Hg, Pb, Cu, Ni, Cr, As, and Zn, with a comprehensive RI averaging at 184.07, signaling a moderate ecological risk. (4) Source apportionment revealed that Zn, Cu, Pb, and Ni were influenced by transportation and household waste emissions, while Cr and As were dictated by natural background levels. Hg predominately originated from fossil fuel combustion and Cd from agricultural activities. (5) Mixed sources accounted for the following percentage contributions to sediment heavy metal content: transportation and domestic waste (30.41%), natural background (25.88%), fossil fuel combustion (22.40%), and agricultural activities (21.31%). With anthropogenic inputs exceeding those of natural origins, it is imperative to prioritize the management of Cd, Hg, and Pb as primary pollutants within the region.

Source Analysis and Contribution Estimation of Heavy Metal Contamination in Agricultural Soils in an Industrial Town in the Yangtze River Delta, China

Farmland soil quality is a crucial determinant for agricultural productivity, food safety, and human well-being. Among the various contaminants, heavy metals have emerged as pervasive factors significantly impacting farmland quality, attracting widespread societal concern. In this study, we systematically applied multivariate statistical analysis, geostatistical methods, and the positive matrix factorization (PMF) source apportionment technique to elucidate the sources and contributions of eight heavy metals (Cd, Hg, As, Pb, Cr, Cu, Zn, Ni) in farmland soils within an industrialized town. Our findings reveal that Cd, Hg, Pb, and Zn exhibit pollution or enrichment in farmland soils compared to natural background levels, with Hg and Cd surpassing 164.3% and 50.2%, respectively. Notably, Zn demonstrates discernible point-source pollution. Source apportionment results highlight industrial point sources, coal combustion, and agriculture as the primary anthropogenic contributors to heavy metal contamination, with zinc-plating enterprises being the predominant industrial point sources. Addressing the specific issue of point-source pollution from Zn in industrial activities, further analysis establishes a correlation between soil Zn content and the distance from zinc-plating enterprises. Utilizing an atmospheric transport model, we observe that the impact of industrial activities on soil Zn is limited when the distance exceeds 1.5 km, emphasizing the importance of monitoring Zn pollution within areas less than 1.5 km. This study pioneers a progressive source apportionment approach, considering the origins of different heavy metals, pollution levels, distance factors, and the cost-effectiveness of environmental measures. The insights gained provide scientifically sound strategies for future decision making in environmental protection.

Validation of the intrinsic vulnerability to pollution of fractured siliciclastic aquifers using natural background levels

Aquifers are important water reserves in water-scarce areas. However, uncontrolled human activities and lack of knowledge of aquifer characteristics increase their vulnerability to pollution. Assessing intrinsic vulnerability is essential for improving groundwater management. However, traditional tools, such as DRASTIC, ignore relevant parameters that, in particular contexts, lead to underestimating vulnerability. This work assesses the intrinsic vulnerability to pollution of a siliciclastic aquifer system (Shallow and Upper) by comparing the DRASTIC and modified DRASTIC methods. Modified DRASTIC included parameters such as Land Use and fracturing patterns relevant in populated areas where hydrogeological configurations involve highly cemented and fractured siliciclastic rocks with secondary porosity that define the main pathways for transporting contaminants from the surface. The intrinsic vulnerability was validated using Natural Background Levels (NBLs) of contaminant indicator ions (NO3−, PO43− and SO₄2-) to identify areas where the concentration of these indicators surpassed the NBLs. These areas were compared with the vulnerability classes from DRASTIC methods. NBLs were: 2.12 mg/l, 0.05 mg/L and 26.77 mg/L (Shallow aquifer), and 3.17 mg/L, 0.17 mg/L and 5.06 ml/L (Upper aquifer) for the ions of NO3−, PO43− and SO₄2-, respectively. The ion concentrations surpassing NBLs were spatially distributed, being more notable in the dry season and showing a greater coincidence with the high vulnerability class of the Modified DRASTIC. Thus, the modified DRASTIC better represented the high vulnerability of the aquifer system to pollution and the negative effect of anthropic activities. Additionally, Pearson's coefficients were calculated between the concentrations of contaminant indicator ions and intrinsic vulnerability indices of DRASTIC methods. However, the coefficients lack statistical significance. These results support the relevance of adding land use and fracturing patterns to assess the intrinsic vulnerability of fractured, siliciclastic aquifers in populated regions and show NBLs as a better validation method than Pearson's coefficients in data-scarce contexts.

Incipient Salinization: A Case Study of the Spring of Asclepieion in Lentas (Ancient Lebena), Crete

Sanctuaries devoted to Asclepius were established and operated for almost a thousand years in various Greek and Roman cities throughout the Mediterranean region. The Asclepieion sanctuary in Lentas (formerly known as Ancient Lebena) in Crete was famous for receiving water from a sacred spring. In Ancient Lebena, Levinaion was a famous centre for hydrotherapy, physiotherapy, and a psychiatric hospital. In the present paper, we aim to assess the hydrochemical status of this sacred spring that holds a prominent position in archaeological and historical studies. The main objectives of this study are: Initially, to present supervisory evidence (archaeological, geological, hydrochemical) of an area that was a water resource management model for many centuries, carrying out therapeutic work. The second objective is to present and compare hydrochemical data in the last century, i.e., from 1915 to 2021. The third objective is to highlight and warn of an incipient saltwater intrusion in the area along the Lentas coast. The fourth objective is to propose an alternative and sustainable form of water resources management in the region that requires the study and rational utilization of the sporadic small water springs in the region. Our study focuses on a basic hydrochemical analysis of spring and borehole water in the remains of Levinaion in the Lentas region, and their comparison with sparse historical data of the sacred spring water, aiming to interpret the impact of the changes in the spring water resources that occurred in recent decades due to urban modernization. Our results highlight (i) visible fluctuations in chemical composition of borehole water samples; (ii) a neutral to alkaline pH in borehole waters and an alkaline pH in spring waters; (iii) undetectable arsenic in Lentas borehole water, unlike historical data of Lentas spring water; (iv) low values of dissolved radon in Lentas borehole water and the spring water of Kefalovrysa; and (v) a timeless constant and hypothermic nature of the water of both the sacred spring and borehole of Lentas, and also of the Kefalovrysa spring. The recorded historical data, i.e., from 1915 to 1957, due to the absence of substantial anthropogenic activity in the area, can be used as reference values (natural background levels, NBLs) for the Lentas area. Our findings emerge with the need to bring again the flowing spring water of the sacred spring of Lentas in its original form through sustainable management and re-discover its beneficial therapeutical effects.

Determine the hazards of radioactive elements and radon gas manufacturing processes in an Egyptian fertilizer factory

This study investigated the levels of radioactivity in soil surrounding a phosphate fertilizer factory in Egypt, aiming to assess potential risks to the population exposed to radiation. Concentrations of 238U, 226Ra, 232Th, and 40K were measured in soil samples collected from two subsites: one near the factory (subsite 1) and another further away (subsite 2). Two different systems were used for measuring radioactivity, a high-purity gamma ray spectroscopy system with an HPGe detector for gamma-emitting isotopes and a CR-39 solid nuclear track detector for alpha-emitting radon gas. Subsite 1, located close to the factory, displayed significantly elevated levels of 226Ra compared to global background levels (514 and 456 Bq/kg vs. 35 Bq/kg). Additionally, the concentrations of 238U (241.06 Bq/kg vs. global average 35 Bq/kg), 232Th (16.15 Bq/kg vs. global average 30 Bq/kg), and 40K (146.36 Bq/kg vs. global average 400 Bq/kg) were all above global averages. Furthermore, a high concentration of radon gas (337.06 μSv/y) was measured at subsite 1. The strong positive correlation observed between 226Ra and 238U (0.96256) provides further evidence of potentially elevated radioactivity levels near the factory. In contrast, subsite 2, situated farther from the factory, exhibited natural radioactive background levels within international limits. Quantitative analysis revealed that gamma ray absorbed doses for 226Ra and 232Th exceeded global averages in some samples. Specifically, 226Ra doses ranged from 7.8 to 46.26 ppm (exceeding the 20 ppm global average in some cases), and 232Th doses ranged from 1.98 to 9.14 ppm (exceeding the 10 ppm global average in some cases). The concentration of 40K, however, remained within the global range (0.07%–0.69 %). The observed imbalances in the ratios of Th/U (0.17–0.24 Bq/kg and 0.73–0.24 ppm) and U/Ra (0.81–0.73 Bq/kg and 0.73–0.17 ppm), both of which are significantly lower than their respective global averages of 4 and 2.4, point towards the presence of fertilizer-derived contamination. This conclusion is further supported by the high phosphate concentrations detected in the samples. Overall, this study suggests that radioactive contamination near the phosphate fertilizer factory significantly exceeds global background levels and international limits in some cases. This raises concerns about potential risks posed to surrounding agricultural land and crops.

Quantitative source identification and determination of natural background levels for typical ions in groundwater of the Huaibei Plain, China

Quantitative source identification and determination of natural background levels for typical ions in groundwater of the Huaibei Plain, China

Ecological Risk Evaluation of Heavy Metals in Soils near a Water Dam in Baljurashi, KSA, and Their Accumulation in Dodonaea viscosa

Soil’s contamination with heavy metals is a serious issue, and assessing their levels, regulating their sources, and finding cost-effective technology to limit their toxic effect and soil cleanup are of high priority. The focus of this study was to find out the extent of priority hazard heavy metal contamination in soils close to the Al-Janabeen water reservoir dam in Baljurashi, KSA, and the extent of their accumulation in the Dodonaea viscosa Tacq plant. Soil and plant samples were analyzed for heavy metal concentration using inductively coupled plasma spectroscopy (ICPS). Quantitative single and integrated contamination indices were used to characterize and evaluate the degree of heavy metal contamination in soils. The biological concentration factor (BCF) and the translocation factor (TF) were utilized to determine the extent of transfer and accumulation of heavy metals in the D. viscosa plant. Soil analysis showed the presence of Mn, Cu, Zn, Co, Cr, and Pb among the prioritized heavy metals with Cu, Zn, and Pb values being higher than those in natural background levels. The mean concentration order was Fe > Mn > Zn > Cu > Pb > Cr > Ni > Cr > Co. The single contamination indices’ quantification indicated marked contamination due to Mn, Zn, Cu, Co, Cr, and Pb elements. While integrated contamination factors’ computation showed low ecological risk due to accumulative metals of concern, Nemerow’s index (NI) showed that Cu, Zn, and Pb were the three most abundant pollutants in the examined soils. Analysis of plant parts showed the presence of Mn, Cu, Ni, Zn, Co, Cr, Cd, and Pb at varying quantities in various plant sections. Both BCF and TF factors were less than one, indicating that the D. viscosa plant was limited in its ability to phytoextract and accumulate the metals from the soil. This study suggests more research to locate suitable native plants for phytoremediation and soil cleaning is required in addition to the appropriate planning and management of landfills in order to ensure agricultural sustainability.

Climate warming enhances chemical weathering in permafrost-dominated eastern Siberia

Understanding the impacts of climate warming on hydrogeochemical processes, particularly in areas dominated by permafrost, is crucial. However, the natural background levels of chemical components in eastern Siberian rivers from permafrost-dominated regions and their responses to climate warming have not been adequately quantified. This study aims to address this knowledge gap by using a comprehensive river water chemistry database (n = 1264) spanning from 1940 to 2019. Our results reveal that the concentration of total dissolved solids (TDS), a key parameter of drinking water quality, in river basins predominantly free of permafrost (194.6 ± 256.4 mg/L) is approximately 2.3 times higher than in permafrost-dominated river basins (83.7 ± 35.8 mg/L) in eastern Siberia. These observations imply potential shifts in freshwater quality resulting from permafrost degradation. We further detect that carbonate weathering, which plays a fundamental role in the global carbon cycle, is a predominant process controlling hydrogeochemical cycles. (Ca2+ + Mg2+) concentrations as a proxy for carbonate weathering intensity are sensitive to climate warming, increasing at a rate of 0.10 mmol/(L·°C). This finding provides evidence that the current acceleration of carbonate weathering, driven by climate warming, is already influencing local water quality. Additionally, (Ca2+ + Mg2+) concentrations and TDS are highly interrelated with temperature-dependent variables (e.g., active layer thickness of permafrost and leaf area index) and basin erosion-controlling factors (e.g., precipitation, elevation and slope of basin). Under a warming climate, river chemical fluxes (e.g., export of TDS and major ions) increase notably, especially during the winter, indicating an increase in mineral-laden groundwater discharge to rivers due to permafrost degradation. Our results demonstrate that climate warming is accelerating hydrogeochemical processes in permafrost-dominated Arctic basins.

Agricultural activity on the Mun River basin: insight from spatial distribution and sources of dissolved rare earth elements in northeast Thailand.

Rare earth elements (REE) are emerging pollutants of concern, impacted by intensive fertilizer use and discharge of human and animal waste into agricultural watersheds. However, the natural values and potential anthropogenic enrichment of REE in aqueous systems of the agricultural basins remain poorly understood. This study investigated the spatial variation of dissolved REE in a predominantly agricultural river (Mun River) in northeast Thailand. Dissolved ΣREE concentrations in the Mun River ranged from 5.08 to 272.91 ng/L, with the highest concentrations observed in the middle reaches where agricultural fertilizers and wastewater increased dissolved REE concentrations. The PAAS-normalized patterns and dissolved Eu anomaly jointly reveal that the dissolved ΣREE mainly originated from local rocks and agricultural fertilizers. The dissolved REE in the Mun River is characteristic of a depleted light REE relative to heavy REE, slightly negative Ce anomaly, positive Eu anomaly, and positive Gd anomaly in a punctate distribution. The correlation analysis of (La/Yb)N with fluvial pH and HCO3- indicates that the water environment characteristics of the Mun River control dissolved REE fractionation. The Ce anomaly is associated with the oxidation environment, whereas the Eu anomaly is linked to the lithologic inheritance. Positive punctate Gd anomalies are influenced by human-caused wastewater discharge and applying fertilizers, raising Gd concentrations beyond natural background levels. This study has suggested that the geochemical characteristics of dissolved REE are affected by agricultural disturbances, and future environmental research on dissolved REE is essential to clarifying the impacts of REE on agriculture, the environment, and human health.

Review on metal contamination in equatorial estuaries in the Brazilian Northeast

The present study provides an overview and assessment of the metals and trace metals registered in water, sediment, and biota in estuaries of the Equatorial Zone of the Brazilian Northeast (EZBN). The study aims to compare the degree of contamination and highlight necessary complementary research. The EZBN is characterized by the transition between the humid and hot Amazonian climate and the hot and dry semiarid climate. The spatial distribution identified enrichment for Cu, Pb, Zn, Hg, and Fe in the sediment, and sequential extraction of metals suggested low to medium mobility of metals along the environments. The Parnaíba River Delta, Curimataú, and the Anil and Bacanga estuaries were the environments with the lowest sediment quality for Pb, Zn, Cu, and Fe, identified by the geoaccumulation index (Igeo). The deposits in these estuaries were related to anthropogenic contributions from domestic sewage and inadequate disposal of wastewater from shrimp farms. However, more studies to determine the natural background levels based on sediment cores and metal speciation are necessary to better differentiate between natural and anthropic sources. Oysters, carnivorous fishes, and crustaceans had the best feedback as biomonitors for Cu, Pb, Zn, and Hg, but the application of biomonitoring needs to be expanded and maintained so that the potential for environmental degradation, which can have significant consequences both for the ecosystem and for human health, can be closely monitored in the EZBN estuaries.

Evaluating natural background levels of heavy metals in shallow groundwater of the Pearl River Delta via removal of contaminated groundwaters: Comparison of three preselection related methods

Assessing natural background levels (NBLs) in groundwater is a global concern. Knowledge on groundwater NBLs in urbanized areas is challenging due to the impact of complex human activities. Preselection related methods are common ones for assessing groundwater NBLs. The present study used three preselection related methods to assess groundwater heavy metals (lead, zinc, barium) NBLs in four groundwater units of the Pearl River Delta (PRD) where urbanization continues, and to identify the best one for assessing groundwater NBLs in urbanized areas. Here, methods include a preselection method (method–P), a preselection dominated method (method–PD), and a statistic dominated method (method–SD). Results showed that the method–PD was better than other two methods for assessing groundwater NBLs of heavy metals in the PRD. This is supported by the evidence that differences among heavy metals concentrations in various land-use types in residual datasets formed by the method–PD were insignificant. NBLs of lead in groundwater units I to IV assessed by the method–PD were 2.8 μg/L, 5.9 μg/L, 5.8 μg/L, and 2.6 μg/L, respectively. NBLs of zinc in groundwater units I to IV assessed by the method–PD were 30 μg/L, 180 μg/L, 160 μg/L, and 100 μg/L, respectively. NBLs of barium in groundwater units I to IV assessed by the method–PD were 120 μg/L, 120 μg/L, 90 μg/L, and 50 μg/L, respectively. Compared to the method–PD, the method–SD often underestimates groundwater NBLs of heavy metals because of using the experiential evaluation for residual datasets. The method–P also has an inaccurate evaluation of groundwater NBLs of heavy metals in comparison with the method–PD, owing to both of using the experiential evaluation and the absence of a function for outliers test. The method–P combining with an outliers test would be better than itself for assessing groundwater NBLs. Therefore, the method–PD is the first choice to be recommended for assessing groundwater NBLs in urbanized areas such the PRD. However, this method should not be taken into account for assessing groundwater NBLs in areas where groundwater Cl/Br mass ratios are invalid. Instead, the method–SD and the method–P combining with one outliers test may be choices, because no constraint for these two methods.