One century sedimentary record of lead and zinc pollution in Yangzong Lake, a highland lake in southwestern China

Source apportionment, source-specific health risks, and control factors of heavy metals in water bodies of a typical karst basin in southwestern China

Studying the apportionment of source-specific health risks and control factors for heavy metal pollution in karst regions is crucial for prevention and management. A typical karst basin was chosen in this study to investigate the pollution characteristics of heavy metals, source-specific health risks, and control factors. The results indicate that during the rainy season, As, Cd, and Pb, as well as As during the dry season, were the primary elements responsible for water pollution in the watershed. Comparative analyses showed that the absolute principal component-multiple linear regression (APCS-MLR) model better identifies and quantifies the sources of heavy metals in karst basin waters. The analysis of health risks revealed that during the dry season, heavy metals in the basin posed a moderate cancer risk to adults (10-4 < total cancer risk (TCR) < 10-3), whereas during the rainy season, these heavy metals posed a non-cancer risk (total hazard index (THI) > 1) and a moderate to high cancer risk (10-4 < TCR < 10-2). The APCS-MLR model combined with the health risk analysis showed that Industrial waste discharge sources are the main contributors to the health of basin residents (29.39%-52.57%), making dry season As a non-cancer risk for basin residents, as well as rainy season As and Cd a non-cancer risk and a high cancer risk for basin residents. Therefore, reasonable planning for upstream industrial production should be developed, and priority should be given to monitoring and treating As and Cd pollution in water. Analyses also showed that input pathways, dilution effects, and hydrochemical characteristics may influence the spatial and temporal variability of heavy metals in the basin. The results provide essential information and significant reference for prioritising and managing the health risks associated with heavy metal pollution in water bodies in karst areas.

Reservoirs as high-efficacy sentinels of regional atmospheric pollution and precipitation: magnetic and chemical evidence from a typical subtropical reservoir in South China

While there is a general sense that reservoirs can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. Here multiple-proxy analyses including 210Pb, grain size, heavy metals, magnetic parameters, and spheroidal carbonaceous particles (SCPs) were conducted for a sediment core from a typical subtropical reservoir in South China (Huangkeng Reservoir). 210Pb dating revealed that the core spans from ~ 1964 to 2019, with the sedimentary rate increasing during recent years. The sedimentary environment was mainly influenced by natural process (especially precipitation), along with the accumulation of Cr, Ni, Cu, V, As, Sb, and Co and most magnetic particles. However, four heave metals (Cd, Pb, Tl, and Zn) were found mainly from atmospheric deposition from industrial/agricultural activities in Huizhou City, which was also indicated by SCPs, S-ratio, and χARM/SIRM. According to temporal variation of SCPs, the atmospheric pollution history of nearby city (Huizhou City as the most close one) from 1964 was reconstructed. The study shows that reservoir sediments, especially in areas with few or no natural lakes, are high-efficacy and high-resolution achieves for research on environmental evolution in the Anthropocene related to global change and intensifying human activities.

Distinct lake sedimentary imprints of earthquakes, floods and human activities in the Xiaojiang Fault zone: Towards a quantitative paleoseismograph in the southeastern Tibetan Plateau

Lake sediments that widely distributed in the active and complicated fault zones have been recently showing great potential for paleoseismic reconstruction. However, flood events and human activities may make the seismic signal unrecognizable. In this study, high-resolution analyses of sedimentary structure, physical and chemical proxies, as well as absolutely radioactive dating were conducted on seven representative sediment cores from the depocenter, nearshore and inlet areas of Yangzong Lake, a typical fault lake in the Xiaojiang Fault zone, southeastern Tibetan Plateau (TP). These new data were calibrated by historical documents, suggesting that seismically induced mass-transport deposits (MTDs, i.e., turbidites) were massive and/or amalgamated (earthquake doublet), became fining and thickening towards the lake center (without changing lake morphology), and occasionally exhibited soft sediment deformation structures (SSDs, i.e., microfaults). These sediments were relatively poorly sorted and instantaneously deposited from slope failures within the lake. An extremely strong earthquake could cause coseismic subsidence of the lake basin and destruct the local hydrological system, resulting in exceptionally high Mn and total inorganic carbon (TIC) contents in the lake center. In contrast, flood deposits were thinner with horizontal beddings, had higher terrestrial organic matter (higher C/N ratios), and distributed locally in the lake inlet area. Human activities-induced sediments were inversely graded, poorly sorted and gradually deposited, had horizontal beddings and no erosive base, and exhibited high carbon, Pb and Zn contents and low C/N ratios. In addition, macroseismic investigations and statistical results from intensity prediction equations (IPEs) provided a conservative threshold of ∼8 Modified Mercalli Intensities (MMI) for triggering turbidites, and a ∼ 10 MMI for inducing coseismic subsidence and hydrological destruction. This study was among the first attempts to establish a quantitative lacustrine paleoseismograph in the southeastern TP, and the new results would greatly improve the valid assessment of geohazard risks.

Combining Contamination Indices and Multivariate Statistical Analysis for Metal Pollution Evaluation during the Last Century in Lacustrine Sediments of Lacu Sărat Lake, Romania

Integrated study of both water and sediment in lakes provides important information regarding the human impact on the environment. The current work is focused on the correlation between age, source, composition, and degree of human intervention over the last 178 years and health impact of sediments from Lacu Sărat Lake (Romania), one of the most important balneo-climateric resorts in the country. The novelty relies on the fact that this is the first time the temporal patterns of metal contamination and the human health effects associated with the metal exposure from sediment core samples have been assessed. The sediment contamination status was determined by evaluating several indices, such as the enrichment factor, geo-accumulation index, metal pollution index, and potential ecological risk index, etc. Results showed a significant accumulation of Cd, Cr, As and Ni and a major contribution of Pb, Zn, Cd, Hg, Cr as well as Cu to the potential acute toxicity. The sediment quality guidelines emphasized a risk concerning the life and proper development of benthic organisms in Lacu Sărat Lake. Moreover, the incidental ingestion lifetime carcinogenic risk values for As and Cr suggest a potential risk of developing cancer. A strong human impact was observed especially between 1950 and 1990, which can be attributed to the rapid economic growth and intensive industrial development strategies pursued by the communist political regime in Romania.

Contamination and eco-risk assessment of toxic trace elements in lakebed surface sediments of Lake Yangzong, southwestern China

Toxic trace elements represent an ongoing environmental problem in aquatic ecosystems. However, a lack of quantitative analysis and accurate evaluation has led to unguided control and water management strategies. Lake Yangzong is the main freshwater resource for nearly one million people in Yunnan Province in southwestern China. It has been heavily contaminated in recent years by significant anthropogenic activities including an industrial phosphor-gypsum spill, sewage effluent, and chemical remediation processes. Herein, we combine eco-environmental indices with multiple statistical analyses to determine the ecological risk and degree of contamination of 11 toxic trace elements in the upper sediments of the lakebed. Local geochemical background concentrations were determined using robust regression models developed from sediment core data. Pollution indices (EF/PLI) indicate that severe As contamination was centralized in the southwestern part of the lake. Other toxic trace elements (e.g., Cd, Cu, Pb) are slightly to moderately enriched, and progressively decrease from the northwestern to the southeastern areas of the lake. A more accurate and sensitive index (PCR) was proposed herein, suggesting that contamination was dominated by As and Pb in different lake sections. The northern section of the lake and the southwestern bay exhibited higher contaminant levels than other regions of the lake. Bio-toxic indices (ERF/PERI) indicate that As and Cd pose a high ecological risk, whereas Cu and Pb pose a low risk to biota. Statistical analyses (PCA/PMF) demonstrate that metal contaminants originated from three types of anthropogenic sources: the smelting of metal ores, the leakage of tailings effluent, and coal consumption.

Contrasting ecosystem responses to climatic events and human activity revealed by a sedimentary record from Lake Yilong, southwestern China

Global climate change and human activities have significantly impacted lake ecosystems at an accelerating rate in recent decades, but the differences between the responses of lake ecosystems to these two stressors remain unclear. Thus an improved understanding of the long-term influences of climatic and anthropogenic disturbances is necessary for the management of lake ecosystems. In order to address these issues, a sedimentary record was obtained from Lake Yilong in Yunnan Province in southwestern China, where the climate and natural environment are dominated by the Indian Summer Monsoon and there is a long history of human occupation and intensive human activity. The chronology is based on AMS ¹⁴C dates from 13 samples of plant macrofossils and charcoal, which show that the record spans the last ~12,000 yr. Geochemical indices were used to reconstruct hydro-climatic variations and lake ecosystem responses. The results indicate that a cold and humid climate prevailed from the late Pleistocene to the beginning of the Holocene, which was interrupted by an abrupt decrease in precipitation during 9.7-8.7 ka (1 ka = 1000 cal yr BP, corresponding to the 9.3 ka event). A persistent drying trend occurred during the middle and late Holocene, and there was an increase in the intensity of human activity during the past 1500 years. A comparison of the effects of a natural climatic event and human disturbance reveals contrasting lake ecosystem responses. The lake ecosystem was resilient to the 9.3 ka event and subsequently recovered; however, long-term human activity in the watershed, including deforestation and cultivation, reduced the stability of the lake ecosystem and positive feedback effects were strengthened, leading to the deviation of the system far from its previous stable state. It is concluded that, compared to climate change, human activities have had a much more serious impact on lake ecosystem.

Comprehensive assessment of heavy metal pollution and ecological risk in lake sediment by combining total concentration and chemical partitioning

Total concentration and chemical partitioning of heavy metals are commonly used in environmental quality assessment; however, their comparability and comprehensive application are far less discussed. Herein, bioavailability, pollution and eco-risk of As, Cd, Cr, Cu, Ni, Pb and Zn in surface sediments of Erhai Lake were evaluated referring to multiple indices following the experimental methods of complete digestion, optimized Community Bureau of Reference (BCR) and 1.0 M HCl extractions. Results of bioavailability for most metals were similar and comparable from BCR and HCl extractions. While bioavailable concentrations of Cd and Pb from HCl extraction were significantly (p < 0.01) lower than those from BCR extraction, indicating BCR extraction is more efficient. Results of enrichment factor (EF) and concentration enrichment ratio (CER) suggested that Cd was the highest polluted element followed by As, Pb and Zn, whereas Cr, Cu and Ni were mainly natural in origin. Similar concentrations of anthropogenic As from EF and CER assessments indicated anthropogenic As mainly existed in bioavailable form. However, anthropogenic Cd, Pb and Zn existed in both bioavailable and residue forms, resulting in the underestimation of anthropogenic metals by the CER assessment. The sediment quality guidelines (SQGs), potential ecological risk index (Er) and risk assessment code (RAC) showed inconsistent eco-risks for each of the metals except Cd. Combining pollution level and chemical partitioning with SQGs, Er and RAC assessments, high eco-risk of Cd, moderate eco-risk of As and Pb, and low eco-risk of Cr, Cu, Ni and Zn were graded. Our study highlights the limitation of single index and the necessity of integrating multiple indices following total concentration and chemical partitioning in metal pollution and eco-risk assessments.

Complex relationship between the diversity and stability of chironomid assemblages in the recent sediments of two large alpine lakes in SW China

There is no doubt that the diversity and stability of freshwater ecosystems have suffered dramatic changes as a result of intensified human activities. However, the relationship between community diversity and stability is still debated. In this study, we used biological and geochemical records from the recent sediments of two lakes to test the hypothesis that different aspects of the diversity of the chironomid community have different relationships with community stability. Yangzong Lake (YZ) and Chenghai Lake (CH) are large and deep alpine lakes in SW China. We conducted a multi-proxy study of the sedimentary records spanning the last 200 years from the two lakes. Our focus was on subfossil chironomid remains, but analyses of chemical elements, total organic carbon (TOC) and total nitrogen (TN) were also conducted. The principal results are as follows: 1) Both nutrient and chironomid assemblages underwent a critical transition in 1990 at YZ and in 1998 at CH. 2) The response of species richness varied between the two lakes, but the trends of their respective β diversity indices are consistent, despite the fact that the contributors to β diversity are different. 3) The stability of the chironomid communities has decreased in both lakes since the mid-20th century. 4) The relationship between diversity and stability varies in relation to the type of diversity. Overall, our results emphasize the importance of considering the complex nature of diversity and stability when studying community assemblages.

Centennial records of cadmium and lead in NE China lake sediments

Cores (15 to 40 cm of depth) were collected from 11 lakes of the Songnen Plain in northeastern China to reconstruct changes in potentially harmful trace element (PHTE) inputs as tracers of human activities. In each profile, most PHTE enrichment factors do not differ significantly from the pre-industrial values (EF < 1.5), except for Cd (EF = 2-5.5). This shows that detrital material accounts for a large part of the PHTE supply to the Songnen Plain lakes. Radiometric dating of the cores (²¹⁰Pb, ¹³⁷Cs) showed that Cd contamination started from the mid-20th century and sharply increased in the 1980s', a pattern that matches the rapid economic and industrial growth of China. Comparison with other records in China suggests that a large part of the anthropogenic Cd in these lakes is likely local in origin. Although the Cd inputs, controlled by carbonate minerals, probably originated from a combination of sources, an intensification in agricultural practices, through the use of chemical fertilizers, manure and wastewater would explain these discrepancies between records. These findings highlight the importance of local factors on the Cd geochemical cycle in China. The large anthropogenic component of the Cd inventory compared to other PHTEs (Cu, Ni, Pb, Sb, V, Zn) and its high toxicity indicate that it should be prioritized in future environmental management.

An ESIPT based chromogenic and fluorescent ratiometric probe for Zn2+ with imaging in live cells and tissues

A benzothiazole based fluorescent probe for selective and efficient detection of Zn²⁺ showing potential application in human breast cancer cells.

Sediment evidence of industrial leakage-induced asynchronous changes in polycyclic aromatic hydrocarbons and trace metals from a sub-trophic lake, southwest China

It has been well established that regional patterns of atmosphere-borne polycyclic aromatic hydrocarbons (PAHs) and trace metals were predominantly associated with the trajectory of socio-economic development; however, they could be potentially modulated by anthropogenic fingerprint of local sources such as industrial spill. Here, we established historical pollution data of both PAHs and trace metals from a well-dated sediment core from Yangzong Lake of Southwest China, which experienced a severe tailing leakage accident derived from a zinc concentrate smelting plant in 2007, aiming to evaluate the heterogeneity in their temporal trajectories and their sources of contamination in the context of regional deposition patterns. Sedimentary records show that the concentrations and fluxes of both PAHs and trace metals remained a consistently low level before the 1950s. An increasing trend and the synchronous changes of both PAHs and trace metals during ~ 1950-2002 were well consistent with the temporal pattern of socio-economic development in western China, with coal combustion and smelting industries as the main sources of contamination in this region. However, arsenic (As) and PAHs exhibited a concurrent spike for the period of ~ 2007-2013, contrasting strongly to the regional pattern of these contaminants. The modern concentrations of As revealed a 5- to 14-fold increase over the pre-1950 level, with the contemporary concentrations of PAHs rising by ~ 10-14 times. The sediment records reveal that local fingerprints of smelting activities in the catchment of Yangzong Lake have overridden the temporary pattern of regional atmosphere-borne As and PAHs over the last decade. This highlights the important role of local pollution sources in modulating or even overriding the regional pattern of anthropogenic contamination in highly impacted systems.

Reconstruction of atmospheric trace metals pollution in Southwest China using sediments from a large and deep alpine lake: Historical trends, sources and sediment focusing

Atmospheric pollution, one of the leading environmental problems in South and East Asia, and its impact on the terrestrial environmental quality remain poorly understood particularly in alpine areas where both historical and present-day mining and smelting operations might leave an imprint. Here, we reconstructed atmospheric trace metals pollution during the past century using core sediments from a large and deep alpine lake in Southwest China. The implication of in lake and/or in watershed sediment focusing in pollution quantification is discussed by analyzing 15 sediment cores. Factor analysis and enrichment factor indicated Cd, Pb and Sb as the typical pollutants. Distinct peaks of Pb and Sb pollution were observed around the 1920s, but little Pb pollution was detected in recent decades, different from other studies in similar regions. Cadmium pollution was observed until the mid-1980s synchronized with Sb. The distinctive variations in atmospheric trace metal pollution process in Southwest China highlight the regional and sub-regional sources of metal pollutants, which should be primarily attributed to non-ferrous metal smelting emissions. Both natural and anthropogenic metals showed wide concentration ranges though exhibited similar temporal trends in the 15 cores. Spatial variations of anthropogenic metals were influenced by the in-watershed pollutants remobilization, whereas, natural metals were regulated by the detrital materials in the sub-basin. In-lake sediment focusing had little influence on the spatial distributions of all metals, different from the traditional sediment focusing pattern observed in small lakes. Anthropogenic Cd accumulation in sediments ranged from 1.5 to 10.1mgm^-2 in a specific core with an average of 6.5mgm^-2 for the entire lake, highlighting that a reliable whole-lake pollutant budget requires an analysis of multiple cores. Our study suggests that the management of aquatic ecosystem health should take the remobilization of in-watershed stored pollutants into consideration especially under increasing human perturbation.

Reconstruction of historical lead contamination and sources in Lake Hailing, Eastern China: a Pb isotope study

The history records of lead and its stable isotopic ratios were determined in a sediment core to receive anthropogenic impacts on the Lake Hailing in eastern China. The sediment core was dated based on (210)Pb, (137)Cs, and (239+240)Pu. The historical changes of Pb/Al and Pb isotope ratios showed increasing trend upward throughout the core, suggesting changes in energy usage and correlating closely with the experience of a rapid economic and industrial development of the catchment, Linyi City, in eastern China. Based on the mixing end member model of Pb isotope ratios, coal combustion emission dominated anthropogenic Pb sources in the half part of the century contributing 13 to 43 % of total Pb in sediment. Moreover, contributions of chemical and organic fertilizer were 1-13 and 5-14 %, respectively. In contrast, the contribution of leaded gasoline was low than 8 %. The results indicated that historical records of Pb contamination predominantly sourced from coal combustion and chemical and organic fertilizer in the catchment. In addition, an increase of coal combustion source and fertilizers was found throughout the sediment core, whereas the contribution of leaded gasoline had declined after 2000s, which is attributed to the phaseout of leaded gasoline in China.

Industrial arsenic contamination causes catastrophic changes in freshwater ecosystems

Heavy metal pollution is now widely recognized to pose severe health and environmental threats, yet much of what is known concerning its adverse impacts on ecosystem health is derived from short-term ecotoxicological studies. Due to the frequent absence of long-term monitoring data, little is known of the long-tem ecological consequences of pollutants such as arsenic. Here, our dated sediment records from two contaminated lakes in China faithfully document a 13.9 and 21.4-fold increase of total arsenic relative to pre-1950 background levels. Concurrently, coherent responses in keystone biota signal pronounced ecosystem changes, with a >10-fold loss in crustacean zooplankton (important herbivores in the food webs of these lake systems) and a >5-fold increase in a highly metal-tolerant alga. Such fundamental ecological changes will cascade through the ecosystem, causing potentially catastrophic consequences for ecosystem services in contaminated regions.

Environmental legacy of copper metallurgy and Mongol silver smelting recorded in Yunnan Lake sediments

Geochemical measurements on well-dated sediment cores from Lake Er (Erhai) are used to determine the timing of changes in metal concentrations over 4500 years in Yunnan, a borderland region in southwestern China noted for rich mineral deposits but with inadequately documented metallurgical history. Our findings add new insight into the impacts and environmental legacy of human exploitation of metal resources in Yunnan history. We observe an increase in copper at 1500 BC resulting from atmospheric emissions associated with metallurgy. These data clarify the chronological issues related to links between the onset of Yunnan metallurgy and the advent of bronze technology in adjacent Southeast Asia, subjects that have been debated for nearly half a century. We also observe an increase from 1100 to 1300 AD in a number of heavy metals including lead, silver, zinc, and cadmium from atmospheric emissions associated with silver smelting. Culminating during the rule of the Mongols, known as the Yuan Dynasty (1271-1368 AD), these metal concentrations approach levels three to four times higher than those from industrialized mining activity occurring within the catchment today. Notably, the concentrations of lead approach levels at which harmful effects may be observed in aquatic organisms. The persistence of this lead pollution over time created an environmental legacy that likely contributes to known issues in modern day sediment quality. We demonstrate that historic metallurgical production in Yunnan can cause substantial impacts on the sediment quality of lake systems, similar to other paleolimnological findings around the globe.

Coumarin based dual switching fluorescent ‘turn-on’ chemosensor for selective detection of Zn2+ and HSO4−: an experimental and theoretical study

A coumarin based fluorescence ‘turn-on' chemosensor (HL) for the selective detection of Zn²⁺ and HSO^4¬ has been developed. Emission intensity of HL is enhanced by 27 and 17 fold in presence of Zn²⁺ and HSO^4¬ respectively. Theoretical study interprets the electronic structure and sensing mechanism of HL.

Historical reconstruction of atmospheric lead pollution in central Yunnan province, southwest China: an analysis based on lacustrine sedimentary records

Atmospheric lead (Pb) pollution during the last century in central Yunnan province, one of the largest non-ferrous metal production centers in China, was reconstructed using sediment cores collected from Fuxian and Qingshui Lakes. Lead concentrations and isotopic ratios ((207)Pb/(206)Pb and (208)Pb/(206)Pb) were measured in sediment cores from both lakes. The operationally defined chemical fractions of Pb in sediment core from Fuxian Lake were determined by the optimized BCR procedure. The chronology of the cores was reconstructed using (210)Pb and (137)Cs dating methods. Similar three-phase variations in isotopic ratios and enrichment factors of Pb were observed in the sediment cores from both lakes. Before the 1950s, the sediment data showed low (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios and enrichment factors (EFs=~1), indicating that the sedimentary Pb was predominantly of lithogenic origin. However, these indices were increased gradually between the 1950s and the mid-1980s, implying an atmospheric Pb deposition. The EFs and isotopic ratios of Pb reached their peak during recent years, indicating aggravating atmospheric Pb pollution. The average anthropogenic Pb fluxes since the mid-1980s were estimated to be 0.032 and 0.053 g m(-2) year(-1) recorded in Fuxian and Qingshui cores, respectively. The anthropogenic Pb was primarily concentrated in the reducible fraction. Combining the results of Pb isotopic compositions and chemical speciations in the sediment cores and in potential sources, we deduced that recent aggravating atmospheric Pb pollution in central Yunnan province should primarily be attributed to regional emissions from non-ferrous metal production industries.