The perchlorate record during 1956-2004 from Tienshan ice core, East Asia

Perchlorate in foodstuffs from South China and its implication for human dietary exposure

Perchlorate, an aqueous-soluble compound resistant to degradation, is mainly used in the synthesis of pyrotechnics, herbicides, and other products. It serves as a pivotal component in the production of fireworks, rocket fuel, and explosives. Perchlorate was recognized as a pollutant owing to the potential toxic risk to thyroid function, which could pose a potential threat to the nervous system of infants and pregnant women. Some study had found that perchlorate existed in food, water and air. This study aimed to investigate the levels of perchlorate in six types of foods (n = 570) from South China, and evaluate potential exposure risks for residents. Vegetables were found to have the highest median levels of foods, attributed to elevated water content in leafy vegetables and facile solubility of perchlorate in water. The relatively low levels of perchlorate in food compared to other studies could attribute to the fact that the period of food we purchased in this study was during the wet season while the contaminants, such as perchlorate, were diluted. The maximum hazard quotient (HQ) values for all residents consuming different foods and water were all higher than 1 This suggested that there is a potential health risk of perchlorate to residents in South China. Those may be attributed to the high levels of perchlorate in some individual samples of meat and eggs. However, the 95th percentile of HQ values in all residents was less than 1, indicating that there is no potential health risk of perchlorate to most residents in South China.

Isotopic Evidence for Microbial Nitrogen Cycling in a Glacier Interior of High-Mountain Asia

Glaciers are now acknowledged as an important biome globally, but biological processes in the interior of the glacier (englacial) are thought to be slow and to play only a minor role in biogeochemical cycles. In this study, we demonstrate extensive, microbially driven englacial nitrogen cycling in an Asian glacier using the stable isotopes (δ15N, δ18O, and Δ17O values) of nitrate. Apparent decreases in Δ17O values of nitrate in an 8 m shallow firn core from the accumulation area indicate that nitrifiers gradually replaced ∼80% of atmospheric nitrate with nitrate from microbial nitrification on a decadal scale. Nitrate concentrations did not increase with depth in this core, suggesting the presence of nitrate sinks by microbial assimilation and denitrification within the firn layers. The estimated englacial metabolic rate using isotopic mass balance was classified as growth metabolism, which is approximately 2 orders of magnitude more active than previously known cold-environment metabolisms. In a 56 m ice core from the interior of the ablation area, we found less nitrification but continued microbial nitrate consumption, implying that organic matter is microbially accumulated over centuries before appearing on the ablating surface. Such englacial microbial products may support supraglacial microbes, potentially promoting glacial darkening and melting. With predicted global warming and higher nitrogen loads, englacial nutrient cycling and its roles may become increasingly important in the future.

Presence of perchlorate in marine sediments from Antarctica during 2017-2020

Perchlorate of natural origin is a persistent pollutant that affects thyroid function by inhibiting iodine uptake, and this pollutant is frequently detected in different ecosystems at concentrations that can harm human health. In this study, we measured the perchlorate concentrations in 3,000 marine sediment samples from January to March in 2017, 2018, 2019, and 2020 during the 3^rd, 4^th, 5^th, and 6^th Colombian Scientific Expeditions to Antarctica. The sampling zones were located at 15 different points on the South Shetland Islands and Antarctic Peninsula, and they were measured using a selective perchlorate electrode. The concentration data indicate that perchlorate reached a minimum concentration of 90 ppm on Horseshoe Island and a maximum concentration of 465 ppm on Deception Island, suggesting a spatial variation in perchlorate concentrations that can be attributed to the natural formation of this pollutant due to volcanic eruptions. Additionally, homogeneous distribution of perchlorate was not observed in Antarctica.

Perchlorate occurrence, sub-basin contribution and risk hotspots for drinking water sources in China based on industrial agglomeration method

Perchlorate is a persistent inorganic contaminant which has attracted wide attention because of its harmful effects on physical health. Despite the potential adverse effects to humans via drinking water, related research at the national scale in China are scarce. In this study, the occurrence of perchlorate in major river basins in China was investigated from 2009 to 2020. Generally, except for the Yangtze River Basin, perchlorate concentrations in the surface water of other river basins were low, ranging from < 0.01 to 8.53 μg/L. The results of a specialized field sampling and tracking program in the Yangtze River Basin in 2019 showed that the Xiangjiang River basin is the greatest contributor of perchlorate in the Yangtze River Basin, accounting for 58.63% of the total perchlorate input. Furthermore, based on correlation analysis between production enterprise information and measured concentrations in sampled sites, fireworks and explosives production industries were identified as the major sources of perchlorate contamination in surface water. The risk map showed that the central-southern part of China and the central part of Xinjiang province were risk hotspots for perchlorate contamination. The results gave insights into how to conduct more precise risk assessment and policy intervention towards prevention of perchlorate contamination.

Perchlorate - properties, toxicity and human health effects: an updated review

Interest in perchlorate as environmental pollutant has increased since 1997, when high concentrations have been found in the waters of the Colorado River, USA. Perchlorate is very persistent in nature and it is slowly degraded. Although harmful effects of large doses of perchlorate on thyroid function have been proven, the environmental effects are still unclear. The primary objective of the present review is to collect prevailing data of perchlorate exposure and to discuss its impact on human health. The results show that more than 50% of reviewed works found significant associations of perchlorate exposure and human health. This review consists of the following sections: general information of perchlorate sources, its properties and determination methods, role and sources in human body including food and water intake, overview of the scientific literature on the research on the effect of perchlorate on human health from 2010 to 2020. Finally, conclusions and recommendations on future perchlorate studies concerning human exposure are presented.