Source Of Pb Research Articles

Atmospheric lead pollution in a typical megacity: Evidence from lead isotopes.

Atmospheric lead (Pb) pollution has adverse health effects on humans, while the sources and atmospheric process of Pb are key scientific problems. In this study, the concentrations and isotopic composition of Pb in fine particulate matter (PM2.5), coal and street dust samples collected from a typical megacity Beijing were analyzed to identify the sources of atmospheric Pb. Results showed that the Pb concentrations in PM2.5 were high in winter (168.1±32.0ng/m3) and low in summer (27.7±9.1ng/m3), whereas Pb isotopic values presented opposite variation trends. The abnormally elevated Pb concentrations in winter were probably related to coal combustion, while declined Pb concentration in summer may be attributed to favorable meteorological parameters such as high temperature, high wind speed, and frequent rain events. Pb isotopic ratios indicated that anthropogenic sources (coal combustion and vehicle exhaust) and natural sources were the main contributors to Pb in PM2.5. Combined with the binary model, the anthropogenic sources predominantly contributed to Pb in the Beijing atmosphere by approximately 85% annually, while the natural sources accounted for the rest of 15%. More specifically, the contribution of natural sources was about 9.4% in spring, 29.7% in summer, 16.0% in autumn and 6.1% in winter, suggesting that natural sources might contribute more lead into the atmosphere during clear days. Furthermore, the contribution of the vehicle exhaust to atmospheric Pb was nonnegligible in megacity, highlighting that the ownership of motor vehicles in megacity should be regulated and more efforts should be paid to strengthen vehicle emission standard. This study may enrich the reservoir of Pb isotopic composition in nature and provides a new method to investigate the Pb migration and transformation in the environment, and also serve as a theoretical reference for pollution control measures.

Lead Distribution in Urban Soil in a Medium-Sized City: Household-Scale Analysis.

This study characterizes potential soil lead (Pb) exposure risk at the household scale in Greensboro, North Carolina, using an innovative combination of field sampling, statistical analysis, and machine-learning techniques. Soil samples were collected at the dripline, yard, and street side at 462 households (total sample size = 2310). Samples were analyzed for Pb and then combined with publicly available data on potential historic Pb sources, soil properties, and household and neighborhood demographic characteristics. This curated data set was then analyzed with statistical and machine-learning techniques to identify the drivers of potential soil Pb exposure risks and to build predictive models. Among all samples, 43% exceeded current guidelines for Pb in residential gardens. There were significant racial disparities in potential soil Pb exposure risk; soil Pb at the dripline increased by 19% for every 25% increase in the neighborhood population identifying as Black. A machine-learned Bayesian network model was able to classify residential parcels by risk of exceeding residential gardening standards with excellent reproducibility in cross validation. These findings underscore the need for targeted outreach programs to prevent Pb exposure in residential areas and demonstrate an approach for prioritizing outreach locations.

Investigation of trace metals in riverine waterways of Bangladesh using multivariate analyses: spatial toxicity variation and potential health risk assessment.

Minute quantities of trace metals have delirious effects in the human body causing acute and chronic toxicities. These trace metals have the ability to bind with enzymes and proteins causing an alteration in their activity, and, consequently, their damage. In this study, water samples were collected from five sites in Rupsa River (Bangladesh) during dry and wet seasons aiming to assess the trace metal concentration and the correlated health risk for people living in the area. Six trace metals, namely arsenic (Ar), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and nickel (Ni), were measured for further analyzing their spatial and seasonal variations. The measured trace metal concentrations followed this decreasing order: Cr > Pb > As > Cu > Ni > Cd for the dry season, and Cr > Pb > As > Cu > Ni > Cd for the wet season. Among the trace metals, As, Ni, Cr, and Pb exhibited a statistically significative variation throughout the study period. The PCA analysis accounted for 64.5% and 64.4% total variations of the trace metals in dry and wet seasons, respectively. The Euclidean distance of trace metals in water samples across five sites showed significantly different distribution patterns, which were further confirmed by PERMANOVA. Furthermore, CAP model disclosed that trace metals are source-specific: brickfields and sewage effluents were potential sources for Cd, whereas different industries were potential sources for As, Cr, Cu, Ni, and Pb. Correlation analysis showed that Ni and Cr significantly correlated with pH and electrical conductivity. Correlation among the trace metals unveiled that they depended on each other as for their origin, magnitude, and existence in the riverine waterways. As for the health risk assessment, a non-carcinogenic health hazard due to ingestion during regular activities and dermal contact during fishing activity to all kind of people (adult males, adult females, and children) in the studied area was retrieved based on the hazard index (HI) of trace metals, which was higher than the recommended value (HI > 1). Moreover, also the carcinogenic risks of Ni and As due to regular activities via ingestion and dermal contact pathways were higher than the standard value (CR > 1.0E-04), suggesting the occurrence of cancer risk to humans in the study area.

A magmatic‐hydrothermal origin of the Xinfang gold deposit, Liaodong Peninsula, China, revealed by in‐situ S–Pb isotopes and trace element analyses of pyrite

AbstractThe Xinfang deposit is a large gold deposit (>20 t of Au) on the southern edge of the Liaodong Peninsula, China. A total of 37 gold‐bearing orebodies are identified along NS‐ and NW‐striking faults and are mainly hosted by the Archean and Neoproterozoic metamorphic rocks. Three stages of hydrothermal mineralization are distinguished, including Stage I of dominant quartz ± pyrite (Py1), Stage II of quartz‐polymetallic sulfide (Py2), and Stage III of quartz‐calcite ± pyrite (Py3). Gold primarily occurs at the Stage II in association with intensive silicification, pyritization, and sericitization. Here, we report on high‐precision in‐situ LA‐MC‐ICP‐MS analyses of S and Pb isotopic compositions of the sulfide minerals and LA‐ICP‐MS analyses of trace element signature of the pyrite from the Xinfang gold deposit. The δ34S values of the sulfides range from 1.3 to 5.3‰, which is consistent with a magmatic origin of S. The sulfides yield 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb ratios of 37.497–37.773, 15.323–15.410, and 17.004–17.229, respectively, which deviate from the values of the wall rocks, suggesting an external Pb source. The in‐situ LA‐ICP‐MS spot analyses of the pyrite reveals that gold occurs in two generations of pyrite (Py2 and Py3) but at low concentrations (≤0.06 ppm for Py2, ≤0.24 ppm for Py3). Visible gold, however, only occurs in the Stage II assemblage as inclusions in pyrite and quartz, and is distributed along the margins or within the fractures of the sulfides. The Py2 shows high Co, Ni, and As concentrations and is depleted in other trace elements typical of a magmatic‐hydrothermal derivation. In contrast, Py3 exhibits low concentrations in most trace elements. Trace element mapping of Py2 revealed correlations between Fe and Co, as well as Ni and As, indicating their couped substitution in the pyrite structure. The available geological, petrographic and geochemical data consistently suggest that the Xinfang gold deposit formed during the Early Cretaceous by hydrothermal fluids of magmatic contribution.

Constraints of S–Pb–Sr Isotope Compositions and Rb–Sr Isotopic Age on the Origin of the Laoyingqing Noncarbonate-Hosted Pb–Zn Deposit in the Kunyang Group, SW China

The Laoyingqing Pb–Zn deposit is located on the southwestern margin of the Yangtze block and on the east side of the Xiaojiang deep fault in the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic triangle area (SYGT). This deposit was first discovered in the silty and carbonaceous slate of the Middle Proterozoic Kunyang Group that is structurally controlled by thrust faults and anticlines. This study is aimed at investigating whether the Laoyingqing deposit has the same ore-forming age and type as other Pb–Zn deposits related to the Pb–Zn metallogenic system and prospecting prediction of the deep and peripheral areas of the deposits in the SYGT. Based on the sphalerite Rb–Sr age dating and S–Sr–Pb isotopic composition analysis of the Laoyingqing Pb–Zn deposit, the following results were obtained. First, the Rb–Sr isochron age of sphalerite is 209.8 ± 5.2 million years (Ma), consistent with the ages of most Pb–Zn deposits in the SYGT (approximately 200Ma), thereby potentially indicating that these Pb–Zn deposits may have been formed synchronously during the late Indosinian orogeny. Second, the Pb isotopic compositions of sulfides show a linear trend on the average crustal Pb evolution curve in 207Pb/204Pb vs. 206Pb/204Pb plot. In addition, Pb isotopic ratios were consistent with the age-corrected Pb isotopic ratios of basement rocks, consequently suggesting that the source of mixed crustal Pb is mainly derived from basement rocks. Combined with the initial 87Sr/86Sr ratios of sphalerite between the (87Sr/86Sr)200Ma value of the basement rocks and that of the Upper Sinian–Permian carbonates, it can be concluded that the ore-forming metals were mainly derived from basement rocks. Third, sulfur isotopic composition of sphalerite from the Laoyingqing deposits shows δ34SCDT values that range mainly from -2.62‰ to 1.42‰, which is evidently lower than the δ34SCDT values of sulfides (8–20‰) from other Pb–Zn deposits in the SYGT. This can be interpreted as a result of mixing with reduced S that was mainly derived from the thermochemically reduced S in the overlying strata and a small amount of reduced S produced by the pyrolysis of S-containing organic matter. We conclude that the Laoyingqing deposit and most of the Pb–Zn deposits in the SYGT are Mississippi Valley-type deposits, thereby providing new ideas for investigating the deep and peripheral areas of Pb–Zn deposits.

Gut Escherichia coli expressing Pb2+-adsorption protein reduces lead accumulation in grass carp, Ctenopharyngodon idellus.

Lead (Pb2+) is easy to accumulate in fish which become a major source of Pb2+ exposure to humans. In this study, a recombinant Escherichia coli strain expressing Pb2+-specific surface-binding protein anchored by the ice nucleation protein was introduced into grass carp (Ctenopharyngodon idellus) gut to investigate its protective effect against dietary Pb2+ exposure. Pb2+ mostly precipitated on the surface of the engineered strain through Pb2+-specific surface-binding protein, with a maximum adsorption efficiency of 73% and an adsorption capacity of 163μmol/g dry cells. The Pb2+ concentration in engineered bacteria-fed grass carp was reduced significantly, and the residual level of Pb2+ in feces was increased by 76%, compared with the control group. Meantime, the engineered bacteria were able to mitigate the oxidative stress and histological alterations of intestines and dysbiosis of gut microbiota induced by Pb2+exposure. Thus, the engineered bacterium that can effectively reduce Pb2+ residue in grass carp might be a useful tool for decontamintion of lead in aquatic organisms.

Chronic Exposure to Lead and Cadmium in Residents Living Near a Zinc Smelter.

This study aimed to measure lead (Pb) and cadmium (Cd) exposure levels in residents living near a zinc (Zn) smelter in Seokpo-myeon, Bonghwa-gun, South Korea, and identify factors affecting exposure. Residents aged ≥20 years living within 3 km and ≥30 km away from the smelter were classified as the exposure group (n = 549), and the control group (n = 265), respectively. Data were obtained through a questionnaire survey. Blood Pb levels in the exposure group (4.19 µg/dL) were higher than in the control group (2.70 µg/dL). The exposure group (1.32 µg/L) also had higher urinary Cd concentrations than the control group (0.80 µg/L). Male sex, older age, previous work at the smelter, smoking, and proximity to the smelter were associated with higher blood Pb levels on multivariate analysis; urinary Cd concentration was significantly higher in women, those who were older, those with experience of working in a Zn smelter or mine, those with proximity to the Zn smelter, and those who consumed locally grown vegetables. In conclusion, Zn smelters are major source of Pb and Cd pollution and require ongoing public health management to prevent potential adverse health effects.

Assessment of Airborne Lead Provenance in Northern Ontario, Canada, Using Isotopic Ratios in Snow and Cladonia rangiferina Lichens

Fresh snow and lichens (Cladonia rangiferina) were collected along two ~300-km transects in a regional survey around two smelter areas in Northern Ontario, i.e., the Sudbury and Timmins areas, in 2009–2010, as a part of a monitoring program. The samples were analyzed for Pb isotope ratios in snow from 47 sites, and in lichens from 28 sites, for background airborne lead and to determine the influence of distance versus local sources of Pb on a regional scale. Moreover, the lichen samples were split into two portions, the top portion, corresponding to recent growth (2–4 years), and the lower portion (up to 10+ years old) to determine the regime of recent versus old deposition. The study also investigated whether the isotopic signature in fresh snow (~1–2 weeks old) could correlate to the lichens’ recent growth. The Pb isotope signatures, reported as Pb isotope ratios 208Pb/206Pb and 207Pb/206Pb, in both snow and lichen recent growth were uniform over the region, except for localized influences near Sudbury and Timmins, suggesting that the background Pb represented remote sources for most of the region. Three-isotope plots 208Pb/206Pb versus 207Pb/206Pb of snow and lichens followed a linear model typical of mixing lines between two sources. As there are no statistical differences of Pb isotope ratios between fresh snow and recent lichen growth at neighboring stations, either type of sample may be used to describe the short-term record of airborne inputs. Finally, we found a strong relationship between the Pb isotope ratios of the recent growth (upper part) and old growth (lower part) of the lichens, with a slope of 0.9 between the lichen parts. This observation suggests either an isotopic segregation or the older parts of the lichens developed under different Pb source inputs in earlier times.

Investigation of lead sources in manioc flour from riparian communities in the Tapajós Region, Brazilian Amazon

From a previous pilot study, the Tapajos River basin riparian population was found to have elevated blood lead (PbB) levels, ranging from 0.59 to 48.3 μg/dL. Preliminary analyses of these results initially pointed to the metallic plates used in the production of manioc flour as a possible source. The main objective of this study was to investigate the potential environmental sources of Pb in the manioc flour in this region. The study was carried out in eight communities on the Tapajos River, where samples of manioc flour, metal plates and soil from manioc plantations were collected. In addition, samples of deposited sediments from the Tapajos River and its tributaries and riverbank sediments were collected. The metal composition was analyzed by SEM, XRF and GFAAS. The results show that the concentrations of Pb in manioc flour ranges from 0.08 to 0.31 mg/kg and the manioc paste from 0.004 to 0.037 mg/kg. The metallic plates used in the manioc-roasting process are made of carbon steel without Pb in the bulk alloy. Pb concentrations in soils where manioc roots were cultivated range from 8.9 to 26.1 mg/kg and Zn concentrations range from 12.7 to 59.1 mg/kg, indicating a contribution of polymetallic geological deposits. The clay-rich samples have high metal contents (including Pb, Zn and Cu). The Pb content of the clay samples ranges from 10.6 to 25.1 mg/kg. These results suggest that it is unlikely that the Pb found in the manioc flour originates from the metal plates used in its roasting process, rather, it seems to be associated to environmental factors determined by the local geology and soil composition.

Health risk assessment and bioaccumulation of metals in brown and red seaweeds collected from a tropical marine biosphere reserve

In the present study, we have assessed the degree of contamination of heavy metals (Cd, Cu, Pb, and Zn) in ten species of red and brown seaweeds, the seasonal variations in the concentration of metals, and the health risk due to the seaweeds. Overall metal concentrations for red and brown seaweeds followed the order Pb > Zn > Cu > Cd and Pb > Cu > Zn > Cd, respectively. Cd and Pb levels were found to be elevated in both the red and brown seaweeds. Multivariate statistical analysis revealed that the sources of Cd and Pb are mainly anthropogenic. Despite the high concentrations of the non-essential metals (Cd and Pb) in the seaweeds, the health risk assessment revealed that they have a lower hazard index. Hence, consumption of edible red and brown seaweeds from the Tuticorin coast may not pose health hazards in humans for the time being.

Tracing the sources of bioaccessible metal(loid)s in urban environments: A multidisciplinary approach

Understanding the links between sources of magnetic particles and bioaccessibility of metal(loids) in environmental sampling media is crucial for better evaluating human health risks, although relevant information in the scientific literature is scarce. Here, soil, road and house dust samples from a heavy industrial area in Greece were characterized in a multidisciplinary study combining magnetic measurements, SEM/EDS analyses, bioaccessibility measurements and Pb isotopic analyses of bioaccessible Pb. The oral and inhalable bioaccessible fractions of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were assessed by applying simulated gastric and lung solutions. SEM/EDS analysis revealed the abundant presence of anthropogenic Fe-containing spherules of industrial origin in all sampling media, often containing minor contents of Cr, Cu, Mn, Pb and Zn. The inhalation bioaccessibility (%) in all environmental compartments was higher than the oral one for most elements analyzed in the present study. Clear associations between magnetic susceptibility and bioaccessible amounts of most of analyzed elements were encountered for the soil and road dust. The isotopic analyses of bioaccessible Pb showed that there are significant differences in the isotopic ratios between total and bioaccessible Pb. We conclude that Pb solubilized by the simulated gastric and lung extractions is principally anthropogenic, representing a mixture of industrial Pb and Pb related to the past usage of leaded petrol. Low values of 206Pb/207Pb were accompanied by high bioaccessible contents of Cd, Pb and Zn indicating that anthropogenic (mostly industrial) sources exert influence on the bioaccessible forms of these metals. Coupling magnetic and bioaccessibility measurements with stable isotopic technique of bioaccessible Pb is more reliable for determining Pb and other metal sources with high oral and inhalation bioaccessibility.

Distribution Trends of Cadmium and Lead in Timberline Coniferous Forests in the Eastern Tibetan Plateau

The concentrations of Pb and Cd in the needles and twigs of fir and spruce collected from 26 sites in the Eastern Tibetan Plateau were measured and analyzed in this study. The mean concentrations of Cd and Pb were 0.034 and 1.291 mg/kg, respectively, in the needles and 0.101 and 2.511 mg/kg, respectively, in the twigs. These concentrations increased significantly with needle and twig age and peaked at 5 years. The twigs were significantly enriched in Pb and Cd compared with the needles. The spatial distributions of Pb and Cd were determined using the inverse-distance-weighted spatial interpolation method on the basis of the mean concentration of the elements in the needles and twigs from each site. The highest concentrations of Pb and Cd in twigs and needles were found in Yunnan Province and Gongga Mountain. They showed a tendency to decline from Yunnan Province to the northern direction, as well as from Gongga Mountain to the western area. Principal component analysis showed that Pb and Cd originated from the anthropogenic activities in this area. The mining activities and climatic factors may be the main sources of Pb and Cd in this area. Combining the HYSPLIT (The Hybrid Single-Particle Lagrangian Integrated Trajectory) model and PCA, the results implied that exterior Pb and Cd sources from Southeast Asia and the eastern developed cities in China can infiltrate the ecosystem through long-range transportation and accumulate in timberline forests, with atmospheric deposition in the Eastern Tibetan Plateau. This plateau suffers from severe Pb pollution but slight Cd contamination.

A cross scale investigation of galena oxidation and controls on mobilization of lead in mine waste rock

Galena and Pb-bearing secondary phases are the main sources of Pb in the terrestrial environment. Oxidative dissolution of galena releases aqueous Pb and SO4 to the surficial environment and commonly causes the formation of anglesite (in acidic environments) or cerussite (in alkaline environments). However, conditions prevalent in weathering environments are diverse and different reaction mechanisms reflect this variability at various scales. Here we applied complementary techniques across a range of scales, from nanometers to 10 s of meters, to study the oxidation of galena and accumulation of secondary phases that influence the release and mobilization of Pb within a sulfide-bearing waste-rock pile. Within the neutral-pH pore-water environment, the oxidation of galena releases Pb ions resulting in the formation of secondary Pb-bearing carbonate precipitates. Cerussite is the dominant phase and shannonite is a possible minor phase. Dissolved Cu from the pore water reacts at the surface of galena, forming covellite at the interface. Nanometer scale characterization suggests that secondary covellite is intergrown with secondary Pb-bearing carbonates at the interface. A small amount of the S derived from galena is sequestered with the secondary covellite, but the majority of the S is oxidized to sulfate and released to the pore water.

Mapping heavy metal (Cu, Zn, and Pb) pollution and ecological risk assessment, in the surroundings of Gabes cement plant—Tunisia

The pollution and contamination assessment of three heavy metals (Cu, Pb, and Zn) in the topsoil, and common plants (Olea europaea, Prunus persica vulgaris, Ficus carica, Medicago sativa, Zygophyllum album, and Helianthemum kahiricum) were carried out at different distances from a cement plant. This evaluation was based on four evaluation methods: Bioconcentration factor, Contamination factor, Geoaccumulation Index and Potential ecological risk factor. The chlorophylls a and b contents were also analyzed. The highest levels of Cu, Zn, and Pb in the topsoil were found close to the cement factory (cluster D), and the lowest values were observed in a distant oasis (cluster H). The lowest chlorophylls values were observed in perennial plants (O. europaea and F. carica) near the cement plant. Zygophyllum album and H. kahiricum showed capability to remove Cu an Zn in contaminated locations, depending on the soil type. The spatialization of the results was essential to the understanding of the potential contribution of different sources of Cu, Zn, and Pb in the topsoil and to distinguishing different behaviors of the same plant species. Concerning H. kahiricum, further research should be undertaken since it has a high livestock acceptability index and is used in traditional medicine. Novelty statement The impact of three heavy metals (Cu, Zn, and Pb) on the topsoil and six species of plants common in Tunisia (arid climate) will be assessed, and the potential contribution of different sources to the contamination. Few studies have addressed the impact of cement dust in the topsoil and common plant species in arid rangelands, and, as far as we know, none of them have considered the spatialization of the data and results, considering the prevailing wind, plant species location, soil type, and use. Moreover, the ability of steppic vegetation to remove these three heavy metals (phytoextraction) was evaluated using the bioconcentration factor (BCF), soil pollution indices, and ecological risk. Chlorophylls a and b contents were also evaluated to establish the effect of the cement plant on the health of plants located nearby.

Application of Stable Isotopic Ratio Analysis to Identify the Cause of Acute Versus Chronic Lead Poisoning of a Tundra Swan (Cygnus columbianus): A Case Study.

We utilized lead (Pb) stable isotopes to identify the source of acute Pb poisoning in a Tundra Swan (Cygnus columbianus) and evaluated overall Pb exposure. Upon necropsy, we obtained samples of blood, liver, kidney, heart, thigh, breast, femur, and metallic objects (i.e., fishing sinker, spring and swivels) from the gizzard for Pb isotopic analysis. Pb isotope ratios of blood and soft tissues were essentially identical to the Pb ratios of the sinker, the likely source of acute poisoning. The spring and swivels had lower Pb content and ratios distinct from tissue, suggesting no significant contribution to poisoning. Femur Pb isotopic composition was the most distinct biological sample and indicative of a combination of sources. These results demonstrate isotopic analysis as a viable method for determining the source of acute Pb poisoning, and that Pb isotope ratios in bone most likely record a lifetime-averaged metric of Pb exposure.

Isotopic study of the Pb-Zn (Cu-Ag) Santa Maria Deposit, Caçapava do Sul Region, Rio Grande do Sul, Brazil

The Camaquã Mines, in the central-southern region of Rio Grande do Sul State, Brazil, contain the largest deposits of base metals (Camaquã, Cu; Santa Maria, Pb-Zn) in the Camaquã Basin. The host rocks are consisted of sandstones and conglomerates of the Santa Bárbara Group and interbedded volcanic rocks of undefined stratigraphic position. Peperitic features were identified in a mineralized trachytic sill. An age of 565 ± 5 Ma (U-Pb LA-MC-ICP-MS) was obtained for another trachytic rock, which allowed for the identification, for the first time, of the Acampamento Velho Formation in the Camaquã Mines region. Stratigraphic relations demonstrate that both rocks represent this magmatism. Data from Pb isotopes and spatial relationship observed in the field indicate a possible genetic link between Acampamento Velho Formation and Camaquã mineralization. Pb isotopic data also suggest a predominantly older crustal source (1.07 Ga model age) for Pb and possibly for the other metals, with intermediate or mixed origin, suggesting that magmatic-hydrothermal fluids leached the metals from the percolated rocks of the basement.

Evaluation and source analysis of heavy metal pollution in the soil around typical metal smelting and mining enterprises in Hunan Province

In order to understand the current situation of heavy metal pollution in soil around typical metal smelting and mining industry in Hunan Province, 30 enterprises in the metal smelting and mining industry were selected as the research objects in this study, single factor pollution index, Nemeiro pollution index, potential ecological risk index and “Agricultural Land Soil Pollution Risk Control Standards” (GB15618-2018) were used to comprehensively evaluate the polution status of the soil cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), chromium (Cr), copper (Cu), nickel (Ni), zinc (Zn), and the main components method and the correlation method are also used to explore the sources of heavy metal pollution. The results showed that: The average values of Cd, Hg, As, Cu, Pb, Cr, Zn, and Ni in the samples in the contaminated area were 3.22, 0.985, 65.63, 67.43, 165.53, 94.07, 328, 43.9 mg·kg−1, it is 2.01, 3.66, 1.89, 1.98, 1.98, 1.14, 1.58, 1.39 times of the mean value of the corresponding heavy metal elements in the control point samples; The single factor pollution index (Pi) of heavy metals is Cd>As>Pb>Zn>Cu>Ni>Cr>Hg in dry land, Cd>Hg>Pb>As>Zn>Ni>Cu>Cr in paddy fields, Cd>Zn>As>Pb>Cu>Cr>Ni>Hg in wild grassland, and the order of the heavy metal Pi in woodland is the same as that of dry land. Results of Nemeiro Comprehensive Pollution Index show that the proportion of heavy metal pollution in paddy field, dry land, wasteland and woodland is 44.4%, 48.1%, 52.4%, and 31.6% respectively. The comprehensive evaluation results of the potential ecological risk index showed that the risk levels of dryland, paddy field, wasteland and forestland were 83.3%, 74%, 71.4% and 47.4% in intensity or above. The results of the risk control standard evaluation of agricultural land found that among the 93 soil samples in the contaminated areas, the proportion of samples in the priority protection category, safe use category and strict control category was 10.8%, 50.5% and 38.7% respectively. The results of source analysis showed that Cd, As, Pb, Zn, Cu in the contaminated soil may be influenced by agricultural activities, industrial activities and transportation, Cr may come from the control of the parent material of the soil, and Hg and Ni may be affected by industrial activities. The results show that the pollution control of heavy metals in the soil around the typical metal smelting and mining industry in Hunan Province should focus on strengthening the control and treatment of pollution sources of Cd, Hg, As, Pb and Zn.

Spatial distribution and environmental risk assessment of hazardous elements (As, Hg, Pb, Cd, Cu, Cr, Zn, and Se) in wetland soils of Yellow Sea coastal area, Eastern China

ABSTRACT The spatial distribution and environmental risk assessment of eight hazardous elements in wetland soils in Yellow Sea coastal area of China were investigated. The concentrations of As, Hg, Pb, Cd, Cu, Cr, Zn, and Se varied between 6.35-46.14, 0.004-0.05, 18.90-62.07, 0.17-3.76, 11.34-76.79, 21.52-80.88, 39.25-136.86, 0.002-0.16 mg/kg, respectively. The spatial distributions analysis demonstrated that the high levels of As, Pb, Cd, and Zn were in Sheyang area. The results of correlation and PCA indicated that natural and anthropogenic source were major sources for Pb, Cr, Cu, Zn, and Se. As and Cd were from industrial and agricultural sources, and Hg was from natural source. The Cd indicated that 84% of sites experienced moderate and considerable contamination. The PER indices indicated that 68% of sites experienced considerable and high ecological risk. This study suggested that more attention should be paid to hazardous elements contamination of wetland soils in eastern China.

Correlations between 7Be, 210Pb, dust and PM10 concentrations in relation to meteorological conditions in northern Poland in 1998–2018

Analysis of a twenty-year (1998–2018) data series on 7Be concentrations in weekly collected aerosol samples in northern Poland showed a clear pattern of seasonal changes in 7Be with a maximum in the summer period associated with the most intensive thermal convection and vertical mixing. Activity concentrations of 7Be ranged from 480 μBq m−3 to 9370 μBq m−3. A strong relationship has been shown between 7Be concentrations observed in years and the activity of the Sun related to the sunspot number. Activity concentrations of 210Pb in aerosol ranged from 17 μBq m−3 to 1490 μBq m-3 with maximum occurring in the winter. The difference in the seasonal pattern in 7Be and 210Pb concentrations were directly related to the different sources of both isotopes, as an additional source of 210Pb was the products of combustion during the heating season. Similar pattern with maximum concentrations in winter was observed for PM10, as the main source is the same as in the case 210Pb. A content of PM10 was in the range from 6.5 to 81.7 μg m−3. A statistically significant correlation between both isotopes occurs. At the same time, 7Be, 210Pb and PM10 are visibly related to the dust concentrations ranged from 7.3 μg m−3 in winter to 134.8 μg m−3 in spring. Statistical analysis carried out with simple regression model, stepwise multiple regression, and Random Forest models showed that the sunspots number, air temperature and sunshine duration have the most substantial impact on transport, and hence the concentration of 7Be in the surface layer of the atmosphere. The increase in relative humidity and precipitation and higher wind speed have a statistically significant effect on the reduction of 7Be concentrations in surface air.

Accumulation of sulfides in the basement of southern Hunan Province, China: Implications for Pb–Zn mineralization related to reduced granitoids

Southern Hunan Province lies at the intersection of the Shi–Hang zone and Nanling belt, and is characterized by extensive Mesozoic igneous rocks and coeval polymetallic deposits, including early granodiorite porphyry-related Cu–Pb–Zn polymetallic mineralization (ca. 160 Ma) and late granite-related W–Sn polymetallic mineralization (ca. 155 Ma). Amongst these deposits, the Huangshaping deposit is unique for the coexistence of economic W–Mo and Pb–Zn mineralization, which is associated with reduced granitoids, including quartz porphyry, felsite, and granite porphyry. Unlike the W–Mo mineralization, which has a close temporal–spatial relationship with granite porphyry, the sources of Pb–Zn mineralization have not yet been clarified, mainly because of its distal orebodies of unknown age. Abundant granodioritic enclaves have recently been found in quartz porphyry of the Huangshaping deposit, with zircon U–Pb ages consistent with the quartz porphyry and containing abundant sulfides including chalcopyrite, sphalerite, and pyrrhotite. This study involved in situ LA–ICP–MS determinations of trace element compositions of these sulfides, for comparison with those of sulfides in distal ores and carbonate strata to elucidate the sources of Pb–Zn mineralization in this deposit. Sulfides from granodioritic enclaves have higher Co/Ni ratios, but similar Zn/Cd, Cu/In, and Pb/Sb ratios, compared with those of distal Pb–Zn ores, indicating that sulfides in both enclaves and ores were precipitated from hydrothermal fluids derived from the same single source, although with higher precipitation temperatures for the former. As sulfides in the ores have Pb isotopic compositions distinct from those of other granitoids, we suggest that intrusion of the granodiorites (~5 Myrs before the granitoids) resulted in the accumulation of ore-forming metals in the metamorphic or crystalline basement. These metals were then scavenged by hydrothermal circulation triggered by later intrusions of felsite and granite porphyry, especially fluorine-rich granite porphyry, forming the distal Pb–Zn mineralization near the surface of the deposit. The accumulation of sulfides triggered by earlier granodioritic activity was likely crucial for the formation of distal sulfide mineralization, and perhaps also for that in other W–Mo deposits related to reduced granites in southern Hunan Province.