Sediment records of Sb and Pb stable isotopic ratios in Lake Qinghai

Sedimentary antimony stable isotope record of anthropogenic contamination in a karst lake in southwestern China

Anthropogenic sources of antimony (Sb) are an important driver of pollution in the Earth environment, but their roles in the historical changes of Sb pollution in lake ecosystems are currently poorly understood. This study documents the sedimentary Sb deposition fluxes in Hongfeng lake (HFL), in southwestern China during 1958-2021 and quantifies the changes of anthropogenic contributions to sediments using Sb stable isotopes. Mean Sb concentration (mean: 1.89 mg kg-1) and deposition flux (mean: 302.1 ng cm-2 a-1) in lake sediments remained relatively stable from 1958 to 1980. Sb deposition fluxes increased rapidly since 1980, peaked at 990.8 ng cm-2 a-1 in 2000, and then decreased consistently, reaching 306.9 ng cm-2 a-1 in 2021. Generally, the historical changes in Sb isotopes were anticorrelated with Sb deposition fluxes and enrichment factors, suggesting a lower ε123Sb signature in anthropogenic loading sources, and highlight the ability of Sb isotopes to distinguish anthropogenic signatures from natural processes in complex hydrological systems. Using a binary end-member mixing model, the contributions of anthropogenic sources to the accumulated of Sb in the lake sediments were estimated to be 20 % before 1980s and increased approximate 58 % during 2000-2015, then decreased to 24 % in 2021, likely reflecting the changes of degree in regional industrial activities. Our results help to better understand the response of Sb pollutions to anthropogenic activities and would in turn benefit the controls Sb contamination in lake ecosystems.

Trace elements accumulation over a century in sediment cores from a tectonic lake on the Qinghai-Tibet plateau: Source identification and risk assessment

A record of trace elements in lake sediment can help in assessing the impact of anthropogenic activities on aquatic environments. In the present work, the trace elements profiles (Cu, Cr, Pb, Zn, As, and Cd) were determined in four sediment cores (QH01, QH02, QH07, and Z04) collected in 2012 and 2014 from Lake Qinghai to reconstruct the history of anthropogenic activity in the watershed and to evaluate the pollution status and eco-environmental risks of a typical Third Pole lake environment over the past century. The concentrations of Cu, Cr, Pb, Zn, As, and Cd in these studies ranged between 19.4 and 34.2 μg g^-1, 35.6-53.6 μg g^-1, 3.10-26.8 μg g^-1, 56.4-93.5 μg g^-1, 6.20-15.3 μg g^-1, and 0.086-0.572 μg g^-1, respectively. Statistical analyses indicated that the Pb, Zn, and Cd contents combination of coal, gasoline burning, and agricultural activities in the Lake Qinghai catchment and larger-scale atmospheric inputs during the past 60 years. The enrichment factors for Pb, Zn, and Cd in the sediments of Lake Qinghai are considered to be related to the region of the Qinghai-Tibet Plateau and national socioeconomic development. Enrich factor of Cd values was higher than 3.5 and maximum values of the geo-accumulation index of Pb and Cd were observed in the top layer of the sediment (0-2 cm), indicating moderate contamination. The RI values suggest that the risks to the ecological environment of Lake Qinghai are increasing since the 1950s. The results of this study illustrate that Lake Qinghai is still experiencing high trace elements pollution pressure due to the rapid environmental changes caused by anthropogenic activities on the remote and isolated Qinghai-Tibet Plateau.

Antimony speciation in the environment: Recent advances in understanding the biogeochemical processes and ecological effects

Antimony (Sb) is a toxic metalloid, and its pollution has become a global environmental problem as a result of its extensive use and corresponding Sb-mining activities. The toxicity and mobility of Sb strongly depend on its chemical speciation. In this review, we summarize the current knowledge on the biogeochemical processes (including emission, distribution, speciation, redox, metabolism and toxicity) that trigger the mobilization and transformation of Sb from pollution sources to the surrounding environment. Natural phenomena such as weathering, biological activity and volcanic activity, together with anthropogenic inputs, are responsible for the emission of Sb into the environment. Sb emitted in the environment can adsorb and undergo redox reactions on organic or inorganic environmental media, thus changing its existing form and exerting toxic effects on the ecosystem. This review is based on a careful and systematic collection of the latest papers during 2010-2017 and our research results, and it illustrates the fate and ecological effects of Sb in the environment.

Recent atmospheric metal deposition in peatlands of northeast China: A review

China is one of the fastest-growing economies of the late 20th and early 21st centuries, and heavy metal emissions have increased in parallel with rapid industrialization and urbanization. Over the last decade, several studies of geochemical records from peat have reconstructed changes in atmospheric metal pollution in China. We review the peat records that detail the history of atmospheric metal pollution over the last two centuries in NE China. The ecological risk (ER) of accumulated metals and their potential eco-toxicological effects, through threshold and probable effect concentrations (TEC and PEC), are also evaluated. Peat records of metals show an increase of pollution loads in the environment over the pre-industrial level during the past two centuries, with an unprecedented increase in China over the last 60 years. There is generally good agreement between geochemical peat records from NE China and others records elsewhere in China. However, some discrepancies are observed especially with Hg records from lake sediments. These discrepancies could be explained by several factors, including post-depositional processes or uncertainties arising from dating methods. The ecological risk of heavy metals is found to be relatively weak in the remote and high-altitude environment in NE China. Although, most metals are under the TEC, Pb concentrations usually surpass it and are getting close to the PEC which indicates increasing ecological risks. Some areas of improvement have been highlighted such as the need for more long-term studies on atmospheric metals and a greater number of Pb isotopes records to better capture the long history of human activity and the spatial variability in metal deposition of the region.

Antimony pollution in China

Antimony (Sb) is ubiquitous throughout the environment as a result of natural processes and human activities. In China, superlarge-, large and medium-sized Sb deposits are concentrated in the Guangxi (34.4%), Hunan (21.2%), Yunnan (12.2%) and Guizhou (10.2%) provinces. Due to Sb mining and smelting processes, large quantities of Sb have been released resulting in serious Sb contamination of the local environments. Furthermore, coal combustion and Sb products consumed by the domestic market are also important potential Sb contamination sources. Here, an integrated overview of the current knowledge on the distribution of Sb in Chinese environments and the human health risk with respect to Sb contamination in Chinese mining and smelting areas are presented. The average Sb concentrations found in soils were divided into three groups. Group 1 had lower Sb concentrations of 0.5-1.5mgkg(-1), Group 2 had medium concentrations of 1.5-2mgkg(-1), and Group 3 had relatively high concentrations of over 2mgkg(-1). Soils from the Yunnan, Guangxi, Guizhou and Hunan provinces were extremely enriched in Sb. Data on the sediment and water mainly came from the Yangtze River water systems and some mining and smelting areas. The Sb concentrations in sediments were of the order of a few mgkg(-1). In water, Sb was mainly concentrated in the particle matter. Higher concentrations in water (up to 29.4mgL(-1)) and sediments (up to 1163mgkg(-1)) were mainly limited to the proximity of mining and smelting areas than the faraway places (<5.00mgL(-1) for water and <3.00mgkg(-1) for sediments, respectively). Plants growing in these contaminated soils accumulated high levels of Sb (up to 143.7mgkg(-1)) and exceeded the tolerable concentration (5mgkg(-1)), thus threatening the health of local inhabitants. The local environments around Sb mining and smelting areas were seriously contaminated.