Pb Inputs Research Articles

Status of Sustainable Balance Regulation of Heavy Metals in Agricultural Soils in China: A Comprehensive Review and Meta-Analysis

To control heavy metal pollution effectively, prevention of heavy metal accumulations in agricultural soils should be the priority rather than remediation of heavy metal contamination. In this research, papers which contained input and output fluxes of Cd, As, Cr, Hg, and Pb in topsoil (the plough layer) of agricultural lands in Hunan, Zhejiang, the Yangtze River Delta, Hainan, and China as a whole were explored. Fluxes of heavy metal species were recalculated, and future trends of pollution were predicted. Also, cases regarding the application of technologies to control the input and output of heavy metals were analyzed. Results indicated that atmospheric decomposition was the dominant input source of heavy metals in all study sites except Hainan. The relative contributions of fertilizers, irrigation water, and straw returning fluctuated greatly among different sites. Cd pollution in all sites was the most serious, followed by Cr and Pb. In Hunan, Cd has already exceeded the maximum limit value and needs to be controlled urgently. The input of heavy metals from irrigation water, fertilizers, and straw returning could be controlled by proposing more policies to manage their quality and application amounts. The amount of heavy metals absorbed by plants could be increased by cultivating crops with hyperaccumulators and high-biomass plants.

Variability of rare earth and heavy metal elements in a representative alluvial depositional system.

Heavy metals (Ni, Cr, W, Cd, and Pb) and rare earth elements (REE) were investigated in the flood plain sediments of an island of the lower Yangtze River near Nanjing to determine how the vertical distribution of heavy metals could be affected by natural sedimentation processes and anthropogenic contamination. Stratigraphic analyses of magnetic susceptibility and the mean grain size distribution of the deposits enabled us to identify layers associated with a relatively high influx of suspended sediments that resulted in sudden changes in the concentrations of heavy metals. The results show that layers associated with high sediment influx (0.8m depth) displayed low concentrations of Cr, Ni, W, and Cd that were mainly lithogenic in origin. The Post Archean Australian Shale (PAAS) normalized REE patterns in the flood plain cores were enrichment in Ce and Eu relative to PAAS, indicating that the sediments were most likely derived from a mixture of sediments and not from an anthropogenic source. Sharp increases in Y/Ho ratios, as well as heavy metal (Cd, Cr, Ni, and W) and Y concentrations were observed in the uppermost layer that could have been deposited from the rapid transport of sediment-laden, contaminated waters. The temporal (vertical) trends in Pb concentrations may be strongly influenced by coal burning. Elevated Pb concentrations (350ppm and 1000ppm) correlate with high magnetic susceptibility (> 200 m3 × kg-1) and the history of thermal power plant (1910-2002) activity. The anthropogenic inputs of Pb were, however, not diluted by high suspended sediment loads, which supports the argument that Pb was derived from fly ash.

Recent decline in atmospheric Pb deposition and isotopic constraints on changes in source contributions in snow from northwestern Greenland

We present lead (Pb) concentrations and isotope ratios in a continuous series of 38 snow samples from a 1.9-m snow pit, covering the period from winter 2012 to summer 2017, at the East Greenland Ice-core Project (EGRIP) ice core drill site in northwestern Greenland. Pb concentrations were highly variable, ranging from 1.53 to 94.9 pg g−1 (mean value of 10.6 pg g−1), with higher concentrations during winter and spring and lower concentrations during summer and fall. Our results show a substantial reduction in the Pb concentration of ∼50% between the 2000s and 2010s, reaching a level close to that observed in the mid-18th century, that is, the time of the Industrial Revolution. Remarkably low radiogenic Pb isotope compositions were observed in our samples compared to previously reported values during the 2000s. The Pb isotope mixing model results indicated a decreasing Chinese contribution from the 2000s onwards, while Europe/Russia emerged as a relatively more important contributor to the anthropogenic Pb input to central Greenland during the corresponding period. Thus, we hypothesized that the reduction in Pb pollution in central Greenland is largely due to a decreasing contribution from Chinese sources in response to the effectiveness of stringent emission control measures in China.

Determination of Some Heavy Metals Concentrations in Water and Irrigation Farms along Wulmi River in Pankshin Local Government, Plateau State, Nigeria

Levels of four heavy metals (Co, Cu, Pb and Cd) and three physico-chemical parameters (pH, temperature, total dissolved solids) were determined from Wulmi River at five sampling points (S1-S5) at an interval of 200m between points using atomic absorption spectrophotometer (AAS) and approved standard procedures respectively, and the control site located about 1000 meters away from the study area. Sampling was done monthly in wet season from May-December 2017. The weighted means of physico-chemical parameters determined at each sampling point in the river were in the range 6.53±0.21 - 6.85±0.17 for pH. 25.35±0.79 0C - 25.92±2.310C for temperature which is within the permissible limit of 300C (USEPA,2002), 9.43±3.90 mg/l - 26.71±2.75 mg/l for TDS which is also within the permissible limit of 1000 mg/l (USEPA,2002). The weighted mean of heavy metal concentrations in water at sampling points in the river ranged between 0.11±0.07 mg/l - 0.29 ± 0.19 mg/l for copper, 1.17±0.39 mg/l - 1.76± 0.31 mg/l for cadmium, 0.08 ± 0.05 mg/l - 0.91±0.03 mg/l for lead, 1.53± 0.39 mg/l - 6.48± 3.36 mg/l for cobalt. The soil samples from five irrigation farmlands (F1-F5) around the Wulmi River were also analysed for the heavy metals concentrations. The heavy metals concentrations in the soil ranged between 12.27 ± 3.46 μg/g - 28.05 ± 1.99 μg/g for copper, 5.49 ± 3.09 μg/g - 17.92 ± 2.18 μg/g for cadmium, 2.24 ± 0.02μg/g - 9.85 ± 1.43 μg/g for Lead, 13.48 ± 3.72 μg/g - 27.82 ± 2.65 μg/g for cobalt .Lead and cobalt concentrations in the soils are within the permissible limit set by USEPA (2002) and WHO [1] of 10μg/g and 50μg/g respectively. All the metals under investigation have geo-accumulation input in soils around Wulmi River, except in irrigation farms 2 and 4 which have geo-accumulation input of Pb to be 0.00. Analysis of variance indicates that there is significant difference in pH, concentrations of TDS, Cd, and Co from one sampling point to another throughout the periods of analyses. The data generated will be used to develop a computer based time series model, which can be used to predict the concentrations of the heavy metals in the near future at these sampling points in Wulmi River.

Fractionations of heavy metals and their correlations with magnetic susceptibility in soil from a typical alluvial island in the lower yangtze river, China

The use of magnetic susceptibility (χ) as a means of assessing heavy metal pollution in soils has been explored by researchers, yielding varying results in terms of the correlations between χ with heavy metals. The efficacy of χ as an indicator of soil heavy metal pollution remains a topic of debate. This study aims to elucidate the inter-relationships between χ, iron oxides, and heavy metals in soil through the application of a modified 5-step sequential extraction procedure (SEP), and to identify an effective approach for assessing metal concentrations in soil using magnetic susceptibility measurements. The soil samples were collected from a typical alluvial island in the lower Yangtze River, China, and a total of 6 forms (exchangeable and acid soluble fraction, easily reducible fraction, oxidizable fraction, amorphous iron oxide, crystallized iron oxyhydroxides and residual fraction) were partitioned and their heavy metal concentrations and χ were analyzed. The results show that crystalline Fe oxyhydroxides and residual fractions are the two uppermost fractions of heavy metals. By combining the fractionation of elements with the variation of χ of the soil during the processing of SEP, it was inferred that the external input of Fe, Pb, Cr and Cd in the soil likely originated from the vicinal steel production. The correlation analysis revealed a significant correlation between heavy metal concentrations and χ in the residual fraction, whereas no significant correlations were observed between the concentrations of heavy metals and χ in the bulk soil samples. It is recommended that the evaluation of heavy metal contamination in the soil neighboring industrial sites can be conducted via magnetic susceptibility measurements subsequent to the elimination of crystalline iron oxyhydroxides.

Metals and metalloids in high-altitude Pyrenean lakes: sources and distribution in pre-industrial and modern sediments.

High-altitude Pyrenean lakes are ecosystems far from local pollution sources, and thus they are particularly sensitive to the atmospheric deposition of metals and metalloids. This study aims to quantify the effect of human activity in 18 lakes located in both side of the France-Spain frontier. Sediment cores were collected in summer 2013, sampled at a 1cm resolution and the concentration of 24 elements was measured by ICP-MS. Statistic and chemometric analysis of the results highlights the influence of the geographical position and lithogenic features of each lake basin on trapping pollutants. More than the 80% of the lakes showed values of enrichment factor (EF) above 2 for at least one of the elements investigated in at least one core interval, which corroborates the existence of historical anthropogenic inputs of elements in the studied area. The results demonstrate the natural origin of As and Ti in Pyrenees, together with the significant anthropogenic inputs of Cd, Pb, Sb and Sn from ancient times. The data set points mining activities as the main historical source of pollution and illustrate the large impact of the industrial revolution. The regional variability could reflect also differential long-range transport, followed by dry or wet deposition.

Identification and contribution of potential sources to atmospheric lead pollution in a typical megacity: Insights from isotope analysis and the Bayesian mixing model

Atmospheric particulate matter (PM) enriched with lead (Pb) has severe irreversible effects on human health. Therefore, identifying the contribution of Pb emission sources is essential for protecting the health of residents. Using the Pb isotopic tracer method, this study explored the seasonal characteristics and primary anthropogenic Pb sources for atmospheric PM in Tianjin in 2019. We calculated the contribution of Pb sources using the end-member and MixSIAR models. The results showed that Pb loaded in PM10 was more abundant in January than in July, and was strongly influenced by meteorological conditions and anthropogenic emissions. The primary Pb sources of the aerosol samples originated from coal combustion and vehicle and steel plant emissions, mainly originating from local Pb emission sources in Tianjin. The PM10-bond Pb in January was influenced by regional transportation and local sources. The MixSIAS model calculated the contribution of coal combustion as approximately 50 %. Compared with that in January, the contribution of coal combustion decreased by 9.6 % in July. Our results indicate that some of the benefits of phased-out leaded gasoline have been short-lived, whereas other industrial activities releasing Pb have increased. Furthermore, the results emphasise the practicability of the Pb isotope tracer source approach for identifying and distinguishing between different anthropogenic Pb inputs. Based on this study, scientific and effective air pollution prevention and control programs can be formulated to provide decision support for the guidance and control of air pollutant emissions.

The Atmospheric Input of Dissolvable Pb Based on the Radioactive 210Pb Budget in the Equatorial Western Indian Ocean

To estimate the atmospheric deposition flux of 210Pb in the equatorial western Indian Ocean, we determined the dissolved (<0.45 μm) and particulate 210Pb (>0.45 μm) in the water column. In addition, we calculated the atmosphere-derived dissolvable Pb in seawater using the budget of 210Pb. The dissolved 210Pb and total 210Pb were higher in the surface layer and, overall, showed a decreasing distribution with depth. In particular, radioactive 210Pb activities in the surface-to-upper layer (<1000 m depth) were 1.5 to 2 times higher than those reported in the 1970s (in nearby regions), suggesting that there has been additional 210Pb input in recent years. Based on the mass balance of the total 210Pb budget in the water column, we estimated the atmospheric deposition flux of 210Pb and the residence time of Pb for the first time in this region. The atmospheric deposition flux of 210Pb was estimated to be 0.1–0.5 dpm cm−2 yr−1, and these values agreed with the general global estimations for the major oceans (0.1–0.7 dpm cm−2 yr−1). Considering the residence time of 210Pb (29–41 years) in the water column (estimated from the 210Pb inventory and 234Th-based Pb scavenging rate), the atmospheric input of seawater-dissolvable Pb was quantified to be 0.08–0.1 nmol cm−2 yr−1, which is about eight times higher than the estimated input in the early 1990s in the region. Therefore, these results imply that radioactive 210Pb could be a useful tracer for quantifying Pb flux in seawater.

Chemically Catalyzed Phytoextraction for Sustainable Cleanup of Soil Lead Contamination in a Community Garden in Jersey City, New Jersey

Soil lead (Pb) contamination in Pb paint-contaminated homes is a serious health risk in urban areas. Phytoextraction is a green and sustainable technology for soil Pb remediation, but its efficiency depends on the geochemical partitioning of Pb in soil. Following successful laboratory, greenhouse, and panel experiments, a field study was conducted to demonstrate the effectiveness of a chemically catalyzed phytoextraction model for Pb removal. A biodegradable chelating agent, ethylenediaminedisuccinic acid (EDDS) was applied during Pb phytoextraction by vetiver grass (Chrysopogon zizanioides) in a Pb-contaminated community garden in Jersey City, New Jersey. Results showed that soil Pb concentration was reduced from 1144 to 359 mg/kg in 3 years, despite ongoing Pb input to the field plots from a nearby construction site. EDDS was effective in converting non-plant-available forms of Pb (i.e., carbonate-bound, oxide-bound, and organic-bound forms) to plant-available forms (i.e., water-soluble and exchangeable forms). With EDDS application, vetiver roots accumulated 532, 231, and 401 mg/kg of Pb in Years 1, 2, and 3, respectively, which were higher than the values obtained without EDDS applications (228, 154, and 214 mg/kg). This field study demonstrated the effectiveness of a chemically catalyzed phytoextraction model for Pb removal from urban soils.

Exchange of Pb from Indian to Atlantic Ocean is driven by Agulhas current and atmospheric Pb input from South Africa

Using a spatiotemporal dataset of dissolved lead (dPb) from the subtropical oceans surrounding South Africa, this study quantifies the exchange of dPb between the Indian and Atlantic Oceans. Despite the absence of a major Pb source within the South Atlantic sector and the complete phase-out of leaded petroleum in Southern Africa, the ecologically important southeast Cape Basin shows an elevated surface dPb concentration (21–30 pmol kg−1). We estimated up to 90% of the measured dPb in surface waters of the Cape Basin was delivered from the Indian Ocean via the Agulhas Current (AC). Eddy dynamics and leakage at Agulhas retroflection result in an increased Pb flux from winter to summer, while a long-term (2008–2019) temporal change in dPb in the AC-derived water of Cape Basin was contemporaneous to a change in atmospheric Pb emissions from South Africa. The South African-origin atmospheric Pb, however, contributes first to the Agulhas waters in the West Indian Ocean, which is then transported to the South Atlantic, thereby regulating the dPb inventory of the Cape Basin. This indirect mechanism of Pb transfer emphasizes the importance of regulating Pb emissions from Southern Africa to protect rich fishing grounds associated with the Benguela marine ecosystem.

Quantitative Source Apportionment of Potentially Toxic Elements in Baoshan Soils Employing Combined Receptor Models.

Arable soils are crucial for national development and food security; therefore, contamination of agricultural soils from potentially toxic elements (PTEs) is a global concern. In this study, we collected 152 soil samples for evaluation. Considering the contamination factors and using the cumulative index and geostatistical methods, we investigated the contamination levels of PTEs in Baoshan City, China. Using principal component analysis, absolute principal component score-multivariate linear regression, positive matrix factorization, and UNMIX, we analyzed the sources and quantitatively estimated their contributions. The average Cd, As, Pb, Cu, and Zn concentrations were 0.28, 31.42, 47.59, 100.46, and 12.36 mg/kg, respectively. The Cd, Cu, and Zn concentrations exceeded the corresponding background values for Yunnan Province. The combined receptor models showed that natural and agricultural sources contributed primarily to Cd and Cu and As and Pb inputs, accounting for 35.23 and 7.67% pollution, respectively. Industrial and traffic sources contributed primarily to Pb and Zn inputs (47.12%). Anthropogenic activities and natural causes accounted for 64.76 and 35.23% of soil pollution, respectively. Industrial and traffic sources contributed 47.12% to pollution from anthropogenic activities. Accordingly, the control of industrial PTE pollution emissions should be strengthened, and awareness should be raised to protect arable land around roads.

Sources and historical records of metal(loid)s in river sediments from an agricultural tributary of Tuojiang river: Evidence from geochemical analyses and Pb isotope

Clarifying the sources and historical variation of metal(loid)s in agricultural river sediments is vital for watershed contamination control and environmental improvements. In this study, a systematical geochemical investigation of Pb isotopic characteristics and the spatial-temporal distribution of metal(loid)s abundances was conducted to delineate the origins of metal(loid)s (Cd, Zn, Cu, Pb, Cr, and As) in sediments from an agricultural river, Sichuan Province, Southwest China. The results showed significant enrichment of Cd and Zn in the whole watershed, with substantial anthropogenic contributions of 86.1% and 63.1% for the surface sediments, and 79.1% and 67.9% for the core sediments, respectively. As was mainly derived from natural sources. Cu, Cr, and Pb were originated from the mixing sources of natural and anthropogenic processes. The anthropogenic origin of Cd, Zn, and Cu in the watershed was closely correlated with agricultural activities. The profile of EF-Cd and EF-Zn displayed an increasing trend from the 1960s–1990s, and then kept a high value, which was consistent with the development of national agricultural activities. Pb isotopic signatures suggested multiple sources of the anthropogenic Pb contamination, including industrial/sewage discharge, coal combustion, and vehicle exhaust. The average anthropogenic 206Pb/207Pb ratio (1.1585) approximated that of local aerosols (1.1660), suggesting aerosol deposition was a crucial pathway of anthropogenic Pb input to sediment. Furthermore, the anthropogenic Pb percentages (mean of 52.3 ± 10.3%) from the EF approach were in line with that from the Pb isotopic method (mean of 45.5 ± 13.3%) for sediments under intense anthropogenic impacts.

Heavy Metal Pollution in Soil and Surface Sediments of Meycauayan River, Philippines and Their Relationship to Environmental Indicators

ABSTRACT The City of Meycauayan is an industrial powerhouse in the Philippines. It is considered as one of the most polluted cities in the developing world on the account of industrial discharges of toxic materials to the environment. This work investigated the sources of the heavy metal pollution in Meycauayan by analyzing soil and sediment samples for heavy metals like Chromium (Cr), Mercury (Hg), Nickel (Ni), and Lead (Pb) together with selected environmental indicators such as Total Nitrogen (TN), Total Organic Matter (TOM), and Total Phosphorus (TP) located along the Meycauayan River. Hierarchical cluster analysis (HCA), principal components analysis (PCA), and Pearson correlation analysis (CA) were used to identify the sources of the metals. Our results show delineated locations of severe levels of heavy metal pollution downstream of the river because of the concentration of industrial activities. Cr is due to proliferation of tanneries discharging untreated wastewaters to the river. Significant input of Pb and Hg from Pb-acid battery recycling and gold smelting industries were also found. The risk assessments also indicate severe levels of heavy metal pollution in locations where industrial activities are concentrated. Our findings indicate that the heavy metals have similar impacts to K, TN, TOM, and TP in the soil and sediments. Our study shows the serious need to address heavy metal pollution in Meycauayan aside from the ongoing cleanup of solid wastes as part of rehabilitation efforts by the local government.

Anthropogenic impacts on the temporal variation of heavy metals in Daya Bay (South China)

A detailed study of a sediment core from Daya Bay (South China) has revealed three stages of heavy metal deposition over the past century. Prior to the 1980s, heavy metal concentrations were low with limited influence by human activities. From the 1980s to 2000, metal pollution intensified, and anthropogenic activities, such as oil and petrochemical industries, and fuel combustion, had the greatest direct influence on Hg, Ni, Pb, and Zn concentrations, whereas atmospheric deposition and mariculture were also contributors to the continued increase in Cr, Cu, Pb, Zn, and Ni. Since the year 2000, heavy metal concentration has declined and stabilized. It is noteworthy that anthropogenic input of Cu and Pb is ongoing and may result in a moderate pollution risk. Both modified pollution index (MPI) and modified ecological risk (MRI) consistently indicate that the ecological risk in terms of heavy metals in Daya Bay has remained moderate over the past 70years.

Trace Elements in Sediments of Two Lakes in the Valley of the Middle Courses of the Ob River (Western Siberia)

Lake sediments accumulate various pollutants and act as efficient natural archives suitable for reconstruction the environmental conditions of the past. In contrast to fairly good knowledge of mineral sediments in lakes of European and North America boreal lakes, Siberian lakes of the boreal zone remain quite poorly studied. In this work, two cores of lake sediments of the Ob River valley were investigated. Elemental analyses were carried out on the sediments, losses on ignition were determined, and the rate of sedimentation was measured from the activity of Pb-210 and Cs-137. According to the content of organic matter, bottom sediments belong to different types: clastic (Lake Inkino, located in the Ob River floodplain) and organogenic (Lake Shchuchie on the second terrace). The rate of sedimentation in Lake Shchuchie is several times higher than that in Lake Inkino. The sediments of Lake Inkino are similar in composition (including the pattern of rare earth elements) to the suspended particulate matter of the Ob River as well as to average detrital matter of the upper continental crust. Sediments of Lake Shchuchie (sapropels) are enriched in a number of heavy metals. Based on the elemental composition, signs of diagenetic processes and authigenic mineral formation were determined, such as accumulation of carbonates and the formation of manganese oxides and hydroxides. There is an enhanced recent input of Cr, Co, Cu, Zn, Cd, Sb, Pb, and Bi in the upper layers of sediments as a result of atmospheric anthropogenic pollutant deposition.

Unexpectedly high dissolved210Pb in coastal groundwaters: Is submarine groundwater discharge important in coastal sea?

Estimating 210Pb sources/sinks is significant for understanding the transport processes and chronology of sediment in coastal seas. Although submarine groundwater discharge (SGD) has been recognized as an important pathway for the transport of terrestrial chemical components, the 210Pb source in coastal seas from SGD is generally ignored. In the present work, we built the 210Pb budget by analyzing the 210Pb activity concentrations in submarine groundwater (i.e., coastal well water and pore water), river water, and seawater in a typical aquaculture bay along the Chinese coast in the Beibu Gulf (Qinzhou Bay). The results showed that the 210Pb activity concentrations (Bq/m3) in well water, porewater, seawater and river water were 6.0 ± 3.6 (n = 13), 3.8 ± 0.4 (n = 2), 1.2 ± 0.3 (n = 4), and 1.9 ± 0.6 (n = 3), respectively. The SGD-derived 210Pb flux was calculated to be (3.3 ± 0.4) × 1010 Bq/yr (approximately 1.4 times the river input flux), which accounted for ∼18% of the total 210Pb sources in Qinzhou Bay. Although most of the 210Pb (>66%) would be buried into the sediment of this coastal bay, SGD-discharged dissolved 210Pb can account for approximately half of the ocean mixing, which is the second most important 210Pb sink in Qinzhou Bay. Therefore, based on these estimates, we have shown that the 210Pb input from SGD can be an important source at the coastal sea scale and needs to be accounted for in coastal sea areas.

Sources and trends of trace elements and polycyclic aromatic hydrocarbons in a shallow lake in the Mediterranean area from sediment archives of the Anthropocene

In this study, the anthropogenic contamination in Trasimeno lake (Central Italy) was investigated using three sediment cores spanning over the last 150 years (Anthropocene) to identify the primary sources of pollution and quantify the level of contaminant enrichment in the basin. First, based on the relative cumulative frequency and linear regression methods, we obtained a geochemical baseline for the lake using the deeper parts of the sediment cores. The geochemical baseline allowed us to determine the values of trace elements enrichment factors. On this knowledge, as a second result, we were able to reconstruct the natural sources and the anthropogenic impact on the lake with a biennial resolution. This goal has been obtained by combining different inorganic and organic chemical proxies such as trace elements, polycyclic aromatic hydrocarbons, and lead isotope ratios and exploiting both principal component and factor analysis to associate chemical proxies to human-driven contamination processes. Five different groups of elements have been identified, one of which is of natural origin and four of anthropogenic origin. In particular, it was possible to identify the times and impacts of the industrial activities during the Second World War, which dispersed heavy metals in sediments. Moreover, we found evidence of the recent human activities that have characterized the surroundings of the basin, such as Pb inputs related to the use of gasoline and the enrichment of certain elements generally used in agricultural activities (such as P, Cu, and Mn) due to the development of this sector in the last 40 years.

Lead isotopic fingerprinting as a tracer to identify the sources of heavy metals in sediments from the Four Rivers’ inlets to Dongting Lake, China

In this study, Pb isotopic composition of bulk sediments and 1 M HCl leachates/residues of samples from the Four Rivers’ inlets to Dongting Lake (China) was determined to identify and differentiate the source of Pb inputs. Results highlighted that Xiangjiang river (XY-QS) sediments were highly enriched in Pb with less radiogenic Pb isotopes (e.g., 206Pb/207Pb ratios of 1.1830 ± 0.003), indicating the predominance of anthropogenic Pb inputs. In contrast, sediments of the Zijiang, Yuanjiang and Lishui rivers (ZD-LH) were moderately enriched in Pb and exhibited more radiogenic Pb (e.g., 206Pb/207Pb ratios of 1.1880 ± 0.008). Results from 1 M HCl extraction of XY-QS sediments illustrated that anthropogenic Pb was removed, which resulted in differentiation of 206Pb/207Pb isotope ratios between leachates (1.1740 ± 0.005) and residues (1.1846 ± 0.008), however, this difference was not observed in ZD-LH sediments (leachates: 1.1887 ± 0.009; residues: 1.1887 ± 0.008). Residual Pb isotope ratios suggested that Pb isotopic composition of lithologically inherited Pb in inlet sediments was similar, which was attributed to mixing, hydrological sorting, and averaging of different Pb sources from diverse geological settings. Pb isotopic tracing showed that Pb in XY-QS sediments resulted from the mixing of two end member sources, an anthropogenic source (less radiogenic Pb) from downstream ore smelting and upstream ore mining activities (53%) and a lithological source (37%) from granite through weathering. In contrast, Pb in ZD-LH sediments resulted from the mixing of multiple sources including Pb from upstream mining activities (20%), coal combustion (20%), and lithologically inherited Pb (60%) while surface sediments from the Yuanjiang river contained Pb from diesel oil usage (50%). Results from this study highlight the utility of a Pb isotope approach for identifying and differentiating Pb source inputs in diverse sediments from the Four River inlets to Dongting Lake (China).

Interannual variation and sources identification of heavy metals in seawater near shipping lanes: Evidence from a coral record from the northern South China Sea

Heavy metal pollution is a serious environmental problem in the marine ecosystem. Thereinto, marine transportation activities have gradually become an important source of heavy metals in seawater. However, the lack of studies on the temporal dynamics of seawater heavy metals in marine shipping areas has hindered our understanding of the sources and transport mechanisms of heavy metals in seawater of hectic shipping waters. Therefore, we investigated the interannual resolution variation of heavy metals in Porites lutea skeletons during the past 32 years under the rapid development of the shipping sector near Weizhou Island from the northern South China Sea. Results show that most heavy metal concentrations with higher coefficients of variation (≥100 %) in the Porites coral skeletons were higher than those in the uncontaminated or less anthropogenic waters. The results of principal component analysis and multiple linear regression showed that the interannual variations of Ni, V, Cr, Co, Zn, Cu, Mn, Fe and Mo were mainly impacted by marine oil extraction and oil spills generated by shipping activities, accounting for 51.58 %. The effect of sea surface temperature accounts for 13.44 %, and controls the interannual variations of Ba and Sr. The effect of industrial pollution accounts for 13.27 %, and explains the interannual variations of Cd and Y. The fuel consumption of marine shipping accounted for 8.76 %, explaining the interannual variations of Pb. The total contribution of anthropogenic activities reached 73.61 %. The interannual variation of heavy metals indicates that hectic marine shipping activities are the dominant cause of Ni, V, Pb, Cr, Co, Zn, Cu, Mn, Fe and Mo input to surface seawater around Weizhou Island. This provided valuable data for understanding the temporal dynamics and potential sources of heavy metals in the marine environment by using coral skeletons as a high-resolution recording vehicle.

Characteristics, sources, and risk assessment of thallium and associated with metal(loid)s in the Yarlung Tsangpo River Basin, southern Tibetan Plateau.

The Tibetan Plateau (TP) is known as the water tower of Asia, and the water quality has long been a focus of public concern, especially in the Yarlung Tsangpo River Basin (YTRB), a unique area that is climate-sensitive, geologically complex, eco-fragile, and densely populated. Thallium (Tl) is a typical metal that is more toxic than Pb, Cd, and As and often occurs in sulfide minerals. Although large-scale polymetallic sulfide mineralization developed in the YTRB, the geochemical dispersion and potential risk of Tl in aquatic environments of the YTRB remain poorly understood. In this study, the concentration, distribution, source, and health risk of Tl and associated metal(loid)s in the hot springs and surface water in the YTRB were systematically analyzed. The results showed that the trace elements (Cd, Cr, Zn, Cu, Al, Sr, Ni, Co, Mn, Pb) in water environments are within the recommended limits, except for Tl and As. Principal component analysis (PCA) and correlation analysis (CA) showed that the elements of Tl and As were positively related to each other in either both hot spring water and surface water, indicating their common origin. Spatial variations suggested that high levels of Tl and As observed in the north YTRB, which may be relevant to the reduction-dissolution of Tl (As)-bearing minerals and the magmatic hydrothermal system formed in the shallow part of the northern YTRB. Furthermore, source apportionment identified natural sources of Cu, Ni, Cr, Co, Mn, Zn, and Cd and anthropogenic inputs of Al and Pb. Exposure assessment studies have found that ingestion is the primary route of As and Tl exposure to local population, and balneological and bathing purposes do not constitute a human health concern. This study offers valuable insights into the risk of naturally occurring Tl enrichment being hidden in As-rich hydrosphere in the YTRB and other regions with similar geoenvironmental contexts.