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Green tea has many health benefits and is the most consumed type in China. However, the heavy metals and contaminants in tea can also pose a great risk to human health. In this study, mercury (Hg) concentration in green tea collected from 11 provinces in China was examined. The leaching characteristics of Hg during brewing and the associated exposure to drinkers were also evaluated. Results indicated a low potential of Hg accumulation in green tea. The Hg content of green tea from Wanshan District, Guizhou Province—which has the largest Hg mine in China and is severely contaminated by Hg—could be limited by controlling the harvest time of tea leaves. The average Hg content of green tea from 43 tea production sites in China was only 6.3 ± 6.4 µg/kg dry weight. The brewing experiments of green tea showed that the leaching ratio of Hg was 22.61 ± 7.58% for 40 min of a single brew, and increased to 32.83 ± 12.37% after four rounds (3 min/ round) of brewing. The leaching of Hg from tea leaves was significantly affected by leaching time, temperature, and solid-liquid ratio but not by water hardness. The risk of Hg exposure from green tea intake was found to be very low, with an average hazard quotient (HQ) value of only 1.82 ± 1.85% for a single brew in 40 min and 2.64 ± 2.68% after four rounds of brewing. However, in some highly contaminated areas, with HQ values as high as 43.12 ± 2.41%, green tea intake may still pose a high risk of Hg exposure, and this risk should not be ignored. [Display omitted] • The Hg content of green tea in China ranged from 1.8 to 102.9 µg/kg. • Green tea Hg content could be control by adjusting the harvest time. • Leaching time, water temperature, and solid-liquid ratio affect the Hg leaching ratios from green tea. • Hg expose risk from green tea was low for most cases. [ABSTRACT FROM AUTHOR]

Consumption of mercury (Hg) contaminated vegetable is one important pathway of Hg expose to humans. In this study, Hg contents in a popular vegetable, Houttuynia cordata Thunb. (HCT), and its growing soils in Kaiyang county in Guizhou province of southwest China were investigated. Health risk related to Hg exposure through consumption of this vegetable was evaluated for the first time. Hg contents in HCT were found to be much higher in three towns in western Kaiyang county (42.3 ± 48.2 μg/kg, FW), where former Hg mines located, than that in other towns (7.6 ± 5.0 μg/kg, FW). Hg contents in HCT were also higher than in the other five vegetables (Chinese cabbage, Lettuce, Tomato, Carrot and White radish). Consumption of HCT may account for 37.4–61.1% of total vegetable Hg intake of local people in Kaiyang county. Hg concentration in HCT positively correlated with that in soil (r2 = 0.311, p < 0.01), especially, the labile Hg species (F C1 , r2 = 0.796, p < 0.01) and the elemental Hg that is bound to the crystalline oxides (F C3 , r2 = 0.711, p < 0.01), and negatively correlated with Hg that is bound to humic and fulvic complexes (F C2 , - 0.304). Estimated daily intake (EDI) and target hazard quotient (THQ) results shown that Hg expose risk is much higher for children than adults, likely due to their different eating habits and the amount of snack intake. Image 1 • Historical Hg mining activities greatly increased Hg content in Houttuynia cordata Thunb. (HCT). • Houttuynia cordata Thunb. (HCT) may count as high as 61% of total vegetable Hg intake of in a mining area of southwest China. • Hg in soil bound to humic and fulvic complexes negatively correlated with Hg in HCT. • Children's risk of Hg exposure though HCT intake are much higher than that of adult. • December 27, 2019. [ABSTRACT FROM AUTHOR]

Cement plants (CPs) are one of the most important anthropogenic sources of mercury (Hg) emissions in China. Over 1000 cement production lines operate in China and use various raw materials; however, little data on Hg emissions is recorded on site. This study investigated a CP in Guizhou Province that uses multiple mining and industrial wastes as part of the circular economy policy. Among the various raw materials, carbide slag had the highest Hg content (2.6 mg/kg) and contributed half of the Hg input. High Hg concentration (27 mg/kg) in the kiln tail dust and a strong Hg enrichment factor (39) was found, which was determined as the ratio of total Hg accumulated within the clinker production process to the daily Hg input from raw materials and fuel. The clinker had negligible Hg (0.001 mg/kg), while the Hg in cement products (0.04 mg/kg) mostly came from additives and retarders. The estimated atmospheric emission factor of Hg from this CP was 161.5 mg Hg/t clinker, which was much higher than those of other CPs in Guizhou that employ low-Hg raw materials. A five-step sequential extraction experiment with kiln tail dust indicates that Hg mainly existed in fraction of F4 (73–96% of the total Hg, possibly as Hg 2 Cl 2) and that some samples had high proportions of water-soluble Hg (up to 21% of the total), which may be easily released into surrounding water bodies and pose high environmental risks. Using low-Hg raw (or alternative raw) materials and conducting proper disposal of kiln tail dust will reduce the environmental risk of Hg from CPs. [Display omitted] • Mercury was extremely enriched during the clinker production process. • Carbide slag is a high-mercury-laden solid waste that provided the highest mercury input. • Atmospheric emissions of mercury were higher than at other cement plants. • Kiln tail dust poses a considerable environmental risk. [ABSTRACT FROM AUTHOR]

The early Cambrian was an important interval in Earth history, marked by significant evolution of both life and the marine environments it inhabited. While enhanced hydrothermal activity has been proposed as a trigger for ecosystem perturbations in the early Cambrian, it remains unclear how intense and how long such perturbations may have been. To address this, we examined mercury (Hg) concentrations and mercury isotopes, as well as major and trace elements, of organic-rich black shales of the lower Cambrian Niutitang Formation, in the Tongren area of Guizhou Province, South China. Our data show that Hg in these sediments is hosted dominantly by organic matter. Elevated raw and normalized Hg contents provide direct evidence of intense hydrothermal activity during the early Cambrian in South China. We suggest that high metal flux (e.g., Mo, U, and Ba) into the seawater occurred through this intense submarine volcanism, altering seawater compositions. Intense hydrothermal activity was likely a significant trigger of environmental and biological evolution during the early Cambrian in South China. • Hg concentrations and isotope evidence intense early Cambrian hydrothermal activity in Tongren area, South China. • A larger amount of elements was released to the seawater from hydrothermal sources. • Local hydrothermal activity plays significant role to the organic matter enrichments. [ABSTRACT FROM AUTHOR]

Residential coal combustion (RCC) is a major source of atmospheric mercury (Hg) in rural areas of China, but little is known about the isotope signatures of Hg from this source. In the present study, the isotope compositions of speciated Hg (Hg0, Hg2+, and Hgp) in flue gas emitted from RCC were investigated in two important coal-producing areas (Xingren (XR) and Jinsha (JS)) of Guizhou Province, Southwest China. The total Hg concentration in discharged flue gas is in the range of 1.80–9.65 μg/m3 at the two sites, and the emission ratio reaches 99.87%. Isotope signatures of total Hg in flue gas are similar to those of Hg in feed coal, with near-zero Δ199Hg and negative δ202Hg (−1.47‰ for XR and −3.00‰ for JS) in discharged flue gas. Such isotope signatures are very different from those of Hg emissions from modern coal-fired power plants with much higher δ202Hg signals. Negative shifts from Hg0 to Hg2+ in flue gas for δ202Hg (−0.94‰) and Δ199Hg (−0.51‰) were observed, suggesting that both mass-dependent fractionation and mass-independent fractionation occurred during RCC. The nuclear volume effect produced by chlorine oxidation of Hg0 to Hg2+ may play an important role in the observed mass-independent fractionation in Hg2+. Without any air pollution control devices, RCC potentially increases the atmospheric Hg levels and has a negative-shifting impact on the δ202Hg of atmospheric Hg. Image 1 • Isotope signature of total Hg is consistent between flue gas and feed coal • Obvious MDF occurred among different Hg species in the flue gas • Significant MIF is observed for Hg2+ due to the oxidation of Hg0 • RCC is an important Hg source and potentially impacts atmospheric Hg isotope composition [ABSTRACT FROM AUTHOR]

• Hg isotope signature variations in cement production are reported for the first time. • δ202Hg in stack gas of the cement plant averaged at -2.03 ± 0. 31‰. • Significant mass dependent fractionation occurred in the clinker production process. • Insignificant mass independent fractionation occurred in the production process. Characterizing the composition of mercury (Hg) isotopes in the atmospheric emissions of cement plants is critical to understand the global circulation of Hg because large quantities of Hg are released from this source annually. A pre-calciner cement plant in Guizhou Province in Southwest China was selected to investigate the mass dependent fractionation (MDF) and mass independent fractionation (MIF) of Hg in the entire production process and the speciated Hg isotope composition in stack gas. Significant MDF and insignificant MIF were observed in this cement plant. Different raw/correction materials have δ202Hg signals ranging from -1.68 to -2.19‰. Raw meal is featured with lighter Hg (δ202Hg = -2.83 ± 0.18‰) as results of Hg circulation and accumulation during the clinker production. Cement products possess negative δ202Hg values (-1.98 ± 0.02‰) due to the input of light δ202Hg isotopes through additives/retarder limestone, and fly ash and gypsum from coal-fired power plant (CFPPs). Speciated Hg isotopes in the stack gas of the kiln tail and kiln head show no significant differences, and δ202Hg and Δ199Hg in the discharged flue gas averaged at -2.03 ± 0. 31‰ and -0.03 ± 0.07‰, respectively, which has negative δ202Hg characteristics with other anthropogenic sources. [ABSTRACT FROM AUTHOR]