Wanshan Area Research Articles

Mercury Biogeochemical Cycle in Yanwuping Hg Mine and Source Apportionment by Hg Isotopes.

Although mercury (Hg) mining activities in the Wanshan area have ceased, mine wastes remain the primary source of Hg pollution in the local environment. To prevent and control Hg pollution, it is crucial to estimate the contribution of Hg contamination from mine wastes. This study aimed to investigate Hg pollution in the mine wastes, river water, air, and paddy fields around the Yanwuping Mine and to quantify the pollution sources using the Hg isotopes approach. The Hg contamination at the study site was still severe, and the total Hg concentrations in the mine wastes ranged from 1.60 to 358 mg/kg. The binary mixing model showed that, concerning the relative contributions of the mine wastes to the river water, dissolved Hg and particulate Hg were 48.6% and 90.5%, respectively. The mine wastes directly contributed 89.3% to the river water Hg contamination, which was the main Hg pollution source in the surface water. The ternary mixing model showed that the contribution was highest from the river water to paddy soil and that the mean contribution was 46.3%. In addition to mine wastes, paddy soil is also impacted by domestic sources, with a boundary of 5.5 km to the river source. This study demonstrated that Hg isotopes can be used as an effective tool for tracing environmental Hg contamination in typical Hg-polluted areas.

Impact of low-level mercury exposure on intelligence quotient in children via rice consumption

Wanshan is a city in southwest China that has several inactive mercury (Hg) mines. The local population are exposed to methylmercury (MeHg) due to the consumption of Hg contaminated rice. The relationship between Hg exposure and the cognitive functions of local children is unknown. This study investigated the relationship between hair Hg concentrations and the intelligence quotient (IQ) of 314 children aged 8-10 years, recruited from three local primary schools in Wanshan area in 2018 and 2019. IQ was evaluated using Wechsler Intelligence Scale for Children - Fourth Edition (WISC-IV). The average THg concentration in children's hair samples was 1.53μgg-1 (range: 0.21-12.6μgg-1), and 65.6% exceeded the United States Environment Protection Agency (USEPA) recommended value of 1μgg-1. Results of logistic regression analysis showed that children with hair Hg≥1μgg-1 were 1.58 times more likely to have an IQ score <80, which is the clinical cut-off for borderline intellectual disability (R2=0.20, p=0.03). Increasing of 1μgg-1 hair Hg resulted in 1 point of IQ loss in Wanshan children, which was.much higher than that via fish consumption. The economical cost due to Hg exposure was estimated to be $69.8 million (9.43% of total GDP) in the Wanshan area in 2018.

Preliminary calibration results for Jason-3 and Sentinel-3 altimeters in the Wanshan Islands

We present preliminary calibration results for Jason-3 and Sentinel-3A altimeters that we set up in the Wanshan Islands in Guandong Province, China. Two campaigns were carried out in 2018, from March 8 to April 16 and from November 3 to December 11, 2018. Three GPS reference stations and tide gauges were established on the islands of Zhiwan, Dangan, and Wailingding during the campaigns. The in-situ sea surface height (SSH) of the altimeter footprint was determined using the tide gauge. The tidal and geoid connection between the tide gauge locations and the altimeter footprints were computed with the NAO.99Jb tidal prediction system and the EGM 2008 geoid, respectively. The data of the tide gauges were defined using the GPS buoy and GPS reference stations during the campaigns. The results show that the waveform of the altimeters was slightly contaminated by the small islands. The bias associated with Jason-3 and Sentinel-3A amounted to approximately +20.7±49.7 mm and +30.1±39.4 mm, respectively, which agreed well with the results from other in-situ calibration fields. This indicates that the Wanshan area was very suitable as an in-situ calibration/validation field. The wet zenith delay (WZD) determined from the Microwave Radiometer (MWR) and the GPS measurements diff ered from each other for the Jason-3 and Sentinel-3A by -6.6±7.4 mm and 0±6.8 mm, respectively.

Measurement of the sea surface using a GPS towing-body in Wanshan area

Wanshan area has been chosen to be the specified field to calibrate and validate (Cal/Val) the HY-2 altimeter and its follow-on satellites. In March 2018, an experiment has been conducted to determine the sea surface height (SSH) under the HY-2A ground track (Pass No. 203). A GPS towing-body (GPS-TB) was designed to measure the SSH covering an area of about 6 km×28 km wide centered on the HY-2A altimeter satellite ground track. Three GPS reference stations, one tide gauge and a GPS buoy were placed in the research area, in order to process and resolve the kinematic solution and check the precision of the GPS-TB respectively. All the GPS data were calculated by the GAMIT/GLOBK software and TRACK module. The sea surface was determined by the GPS-TB solution and the tide gauge placed on Zhiwan Island. Then the sea surface of this area was interpolated by ArcGIS 10.2 with ordinary Kriging method. The results showed that the precision of the GPS-TB is about 1.10 cm compared with the tide gauge placed nearby, which has an equivalent precision with the GPS buoy. The interpolated sea surface has a bias of −1.5–4.0 cm with standard deviation of 0.2–2.4 cm compared with the checking line. The gradient of the measured sea surface is about 1.62 cm/km along the HY-2 orbit which shows a good agreement compared with the CLS11 mean sea surface (MSS). In the Cal/Val of satellites, the sea surface between the tide gauge/GPS buoy and the footprint of altimeter can be improved by this work.

Maternal inorganic mercury exposure and renal effects in the Wanshan mercury mining area, southwest China.

This study evaluated the relationship between urine mercury (UHg) concentrations and renal function (serum creatinine (SCr) and blood urea nitrogen (BUN)) in delivery women in the Wanshan mercury (Hg) mining area. Leishan County was selected as the control area. 165 and 65 maternal samples were collected from the Wanshan and Leishan area, respectively. The geometric means of UHg concentrations were 1.09 and 0.29μg/L in Wanshan and Leishan subjects, respectively. Significant differences (p<0.01) of UHg were observed between the two populations, indicating the potential risks of inorganic Hg exposure in the Wanshan population. The median (interquartile range) values of SCr were 69.1 (12.5) μmol/L and 46.0 (11.0) μmol/L for the Wanshan and Leishan populations, respectively, indicating significant differences (p<0.01) between the two groups. However, no significant differences among BUN values for the two groups were observed. A significant positive correlation (r=0.385, p<0.001) was observed between UHg concentration and SCr in the study population. The odds ratio (OR) value of UHg in Wanshan area was 9.29 times higher than that in Leishan area (95% confidence interval (CI): 3.58-24.1). The OR value of SCr decrease in patients with low UHg was 0.32 times higher than that in patients with high UHg (95% CI: 0.19-0.55). The OR value of SCr decrease in the population with fish consumption was 0.71 times higher than that of the population without fish consumption (95% CI: 0.58-0.88). In conclusion, maternal IHg exposure caused impaired renal function and fish consumption may play a role in preventing Hg-induced nephrotoxicity.

Evaluation of the potential risks of heavy metal contamination in rice paddy soils around an abandoned Hg mine area in Southwest China

To assess the potential ecological and health risks of trace elements (Hg, Cd, As, Mn, Sb, Pb, Cu, Ni, Cr, and Zn), a total of 138 soil samples from rice paddies were collected during the rice harvest season in the Wanshan mining area, Guizhou Province, Southwest China. Factors of the pollution load index (PLI), geo-accumulation index (I-Geo), enrichment factor (EF), and risk index (RI) were determined. High concentrations of Hg, Sb, As, Zn, Cd, Cu, and Mn were observed in the soils. The PLI, I-Geo, and EF results all showed high levels of contamination by Hg and Sb and moderate levels of contamination by As, Pb, Zn, Cu, Cd, and Mn. There was no significant contamination from Ni and Cr. The RI was very high, with Hg as the dominant pollutant, as expected, indicating that the historical large-scale Hg mining, as well as artisanal mining, has had a significant impact on the Wanshan area. Moreover, coal combustion, manganese factories, and the use of agrochemicals by the local population could also have an impact on the soil through the introduction of heavy metal loads. To address the current state of contamination, pollutant remediation and the regulation control of the anthropogenic activities in Wanshan are urgently needed.

Lidar mapping of atmospheric atomic mercury in the Wanshan area, China

A novel mobile laser radar system was used for mapping gaseous atomic mercury (Hg0) atmospheric pollution in the Wanshan district, south of Tongren City, Guizhou Province, China. This area is heavily impacted by legacy mercury from now abandoned mining activities. Differential absorption lidar measurements were supplemented by localized point monitoring using a Lumex RA-915M Zeeman modulation mercury analyzer. Range-resolved concentration measurements in different directions were performed. Concentrations in the lower atmospheric layers often exceeded levels of 100 ng/m3 for March conditions with temperature ranging from 5 °C to 20 °C. A flux measurement of Hg0 over a vertical cross section of 0.12 km2 resulted in about 29 g/h. Vertical lidar sounding at night revealed quickly falling Hg0 concentrations with height. This is the first lidar mapping demonstration in a heavily mercury-polluted area in China, illustrating the lidar potential in complementing point monitors.

Understanding the paradox of selenium contamination in mercury mining areas: High soil content and low accumulation in rice

Rice is an important source of Se for billions of people throughout the world. The Wanshan area can be categorized as a seleniferous region due to its high soil Se content, but the Se content in the rice in Wanshan is much lower than that from typical seleniferous regions with an equivalent soil Se level. To investigate why the Se bioaccumulation in Wanshan is low, we measured the soil Se speciation using a sequential partial dissolution technique. The results demonstrated that the bioavailable species only accounted for a small proportion of the total Se in the soils from Wanshan, a much lower quantity than that found in the seleniferous regions. The potential mechanisms may be associated with the existence of Hg contamination, which is likely related to the formation of an inert Hg–Se insoluble precipitate in soils in Wanshan.

Thiosulphate assisted phytoextraction of mercury contaminated soils at the Wanshan Mercury Mining District, Southwest China

Wanshan, known as the “Mercury Capital” of China, is located in the Southwest of China. Due to the extensive mining and smelting works in the Wanshan area, the local ecosystem has been serious contaminated with mercury. In the present study, a number of soil samples were taken from the Wanshan mercury mining area and the mercury fractionations in soils were analyzed using sequential extraction procedure technique. The obtained results showed that the dominate mercury fractions (represent 95% of total mercury) were residual and organic bound mercury. A field trial was conducted in a mercury polluted farmland at the Wanshan mercury mine. Four plant species Brassica juncea Czern. et Coss.var. ASKYC (ASKYC), Brassica juncea Czern. et Coss.var.DPDH (DPDH), Brassica juncea Czern. et Coss.var.CHBD(CHBD), Brassica juncea Czern. et Coss.var.LDZY (LDZY) were tested their ability to extract mercury from soil with thiosulphate amendment. The results indicated that the mercury concentration in the roots and shoots of the four plants were significantly increased with thiosulphate treatment. The mercury phytoextraction yield of ASKYC, DPDH, CHBD and LDZY were 92, 526, 294 and 129 g/ha, respectively.

Structural Change of Human Hair Induced by Mercury Exposure

Mercury is one of the most hazardous pollutants in the environment. In this paper, the structural change of human hair induced by mercury exposure was studied. Human hair samples were, respectively, collected from the normal Beijing area and the Hg-contaminated Wanshan area of the Guizhou Province, China. Inductively coupled plasma mass spectroscopy was used to detect the element contents. A small angle X-ray scattering technique was used to probe the structural change. Three reflections with 8.8, 6.7, and 4.5 nm spacing were compared between the normal and the Hg-contaminated hair samples. The results confirm that the 4.5 nm reflection is from the ordered fibrillar structure of glycosaminoglycan (GAG) in proteoglycan (PG) that composes the matrix around the intermediate filaments. The increase of Ca content makes the regular oriented fibrillar structure of GAG transform to a random oriented one, broadening the angular extent of the reflection with 4.5 nm spacing. However, overdose Hg makes the core proteins where the ordered fibrils of GAG are attached become coiled, which destroys the ordered arrangements of fibrillar GAG in PG, resulting in the disappearance of the reflections with 4.5 nm spacing. The disappearance of the 4.5 nm reflection can be used as a bioindicator of overdose Hg contamination to the human body. A supercoiled-coil model of hair nanoscale structure and a possible mechanism of mercury effect in human hair are proposed in this paper.

Organic Selenium Supplementation Increases Mercury Excretion and Decreases Oxidative Damage in Long-Term Mercury-Exposed Residents from Wanshan, China

Due to a long history of extensive mercury mining and smelting activities, local residents in Wanshan, China, are suffering from elevated mercury exposure. The objective of the present study was to study the effects of oral supplementation with selenium-enriched yeast in these long-term mercury-exposed populations. One hundred and three volunteers from Wanshan area were recruited and 53 of them were supplemented with 100 μg of organic selenium daily as selenium-enriched yeast while 50 of them were supplemented with the nonselenium-enriched yeast for 3 months. The effects of selenium supplementation on urinary mercury, selenium, and oxidative stress-related biomarkers including malondialdehyde and 8-hydroxy-2-deoxyguanosine were assessed. This 3-month selenium supplementation trial indicated that organic selenium supplementation could increase mercury excretion and decrease urinary malondialdehyde and 8-hydroxy-2-deoxyguanosine levels in local residents.

Mercury distribution and speciation in water and fish from abandoned Hg mines in Wanshan, Guizhou province, China

Concentrations of total mercury (Hg T), methylmercury (MeHg), and its speciation in water samples as well as fish collected from abandoned Hg mines in Wanshan, Guizhou province, China, were measured to show regional dispersion of Hg contaminations that are not well known. High Hg T and MeHg T (total methylmercury) concentrations obtained in waters from mining areas, ranged from 15 to 9300 ng/l and 0.31 to 25 ng/l, respectively. MeHg T were not correlated with Hg T, whereas, peak values in both cases were in accord with high concentrations of particulate fraction, which appeared to be enhanced during high-flow regime with ratios reaching to 99%. Elevated Hg concentrations in the particulate form indicated that particles released from Hg mining tailings (calcines) might be an important pathway of Hg to the aquatic system. The concentrations of total Hg in fish muscle were elevated ranging from 0.061 to 0.68 mg/kg, but MeHg were generally low ranging from 0.024 to 0.098 mg/kg with a mean ratio of 28%. The concentrations and distribution patterns of Hg in aquatic systems suggested derivation from historic Hg mining sites in the Wanshan area.

Oxidative stress on domestic ducks ( Shaoxing duck) chronically exposed in a Mercury–Selenium coexisting mining area in China

The Wanshan mercury mine is the largest mercury deposit in Guizhou Province, China. Few attempts have been made to study the toxic effects of mercury on biota in this mining area. This study was the first to investigate the oxidative stress on domestic ducks (Shaoxing duck) chronically exposed to mercury in the Wanshan mining area. Chemical analyses revealed higher concentrations of both, mercury and selenium in samples from the Wanshan area. Total mercury and selenium concentrations in duck tissues varied from 0.073 to 4.465 mg/kg and from 1.073 to 6.35 mg/kg, respectively. Analysis of covariance revealed that there were significant effects of zone on accumulation of mercury and selenium in all duck tissues ( P < 0.01 ). Moreover, analysis of covariance indicated that mercury content significantly affected the accumulation of selenium in duck muscle, brain, and liver ( P < 0.01 ). Mercury and selenium were also highly correlated in Wanshan duck liver, muscle, brain, and lung. The statistical analysis suggested that selenium might be an interactive factor in mercury toxicity. As for the biochemical analyses, it was observed that selenium-dependent glutathione peroxidase and superoxide dismutase activities and glutathione (GSH) content were significantly increased in the livers and brains of Wanshan ducks ( P < 0.01 , 0.05). However, no significant changes were observed in malondialdehyde content ( P > 0.05 ). Although the results indicated that adaptive responses of the redox-defense system are associated with the increased enzyme activities and GSH content, the most likely explanation is that selenium plays a critical role. Therefore, the effects of the interaction environmentally occurring selenium and mercury on public health in the Wanshan area should be examined in further studies.

Mercury and methylmercury in riparian soil, sediments, mine-waste calcines, and moss from abandoned Hg mines in east Guizhou province, southwestern China

Concentrations of total Hg and methylmercury (MMHg) in riparian soil, mine-waste calcine, sediment, and moss samples collected from abandoned Hg mines in Wanshan district, Guizhou province, China, were measured to show regional dispersion of Hg-contamination. High total Hg and MMHg concentrations obtained in riparian soils from mined areas, ranged from 5.1 to 790 mg kg −1 and 0.13 to 15 ng g −1, respectively. However, total Hg and MMHg concentrations in the soils collected from control sites were significantly lower varying from 0.1 to 1.2 mg kg −1 and 0.10 to 1.6 ng g −1, respectively. Total Hg and MMHg concentrations in sediments varied from 90 to 930 mg kg −1 and 3.0 to 20 ng g −1, respectively. Total Hg concentrations in mine-waste calcines were highly elevated ranging from 5.7 to 4400 mg kg −1, but MMHg concentrations were generally low ranging from 0.17 to 1.1 ng g −1. Similar to the high Hg concentrations in soil and sediments, moss samples collected from rocks ranged from 1.0 to 95 mg kg −1 in total Hg and from 0.21 to 20 ng g −1 in MMHg. Elevated Hg concentrations in mosses suggest that atmospheric deposition might be an important pathway of Hg to the local terrestrial system. Moreover, the spatial distribution patterns of Hg contamination in the local environment suggest derivation from historic Hg mining sites in the Wanshan area.

The geochemical characteristics of mine-waste calcines and runoff from the Wanshan mercury mine, Guizhou, China

Mercury and other geochemical parameters were measured in mine-waste calcines, stream sediments and surface waters from the Wanshan Hg district in the Guizhou Province of China to evaluate adverse effects of Hg to the surrounding environment. Wanshan ore is dominantly cinnabar, and lacks other sulfide minerals and as a result, heavy metals other than Hg are rare in the calcines and mine-water runoff. Host rocks in the Wanshan area are dominantly carbonates, which upon weathering, produces alkaline-water runoff. Surface waters emanating from calcine piles have water pH varying from 10.6 to 11.8, contain high EC values, and variable major element geochemistries. Dissolved Hg concentration decreases from 300 to 1900 ng/l in mine water to 72 ng/l in stream water collected significantly downstream from the mine. High concentrations of Hg in mine-waste calcines and alkaline surface water are the major threats to the surrounding environment. Alkalinity is also naturally attenuated downstream from the Wanshan mine. However, erosion and transport of Hg in sediment and water and highly alkaline mine-water runoff, may adversely affect sediment, aquatic and biological columns downstream from the Wanshan mine area.

Distribution and speciation of mercury in surface waters in mercury mining areas in Wanshan, Southwestern China

Reactive, dissolved, particulate and total Hg concentrations were measured in surface waters originated from mercury mining areas to evaluate Hg contamination in fluvial systems in Wanshan district, Guizhou, China. Concentrations of total Hg in water samples varied from 17.3 to 585.8 ng/l and were elevated comparing to total mercury concentrations in natural water. The total dissolved Hg concentrations usually ranged from 12.5 to 52.0 ng/l, reactive Hg varied from 1.2 to 5.3 ng/l, and particulate Hg changed between 3.5 and 533.8 ng/l. The highest value of total Hg content occurred in a stream which is contaminated by leachate from the historic abandoned gangue piles was up to 585.75 ng/l. It is suggested that the fluvial systems in Wanshan area were heavy contaminated due to long life of the mining operation and to Hg release from the waste even after the mining activity has been ceased.