Uptake patterns for nitrogen and sulfur source by aquatic plants and various nitrogen acquisition strategies: Affected by mining activities.

Understanding the nitrogen and sulfur uptake strategies of mine plants, including sources and preferences for nitrogen forms (ammonium nitrogen (NH4+) vs nitrate nitrogen (NO3-)), is critical to improving understanding of the role of plants in participating in the biogeochemical cycles of nitrogen and sulfur in mining areas. In this study, the stable N and S isotopic compositions of two species of aquatic plants (calamus and reed) in Linhuan mining area were analyzed to determine their absorption strategies for different nitrogen and sulfur sources. The results showed that river water was the largest source of nitrogen and sulfur, contributing 54.6% and 53.9% respectively. NO3- is the main form of nitrogen uptake by reed and calamus, followed by NH4+. In order to adapt to the change of nitrogen form in the environment, reed and calamus tend to absorb and utilize NO3- to maintain their absorption of nitrogen. Mine effluents from mining activities provide at least 12.9% and 16.8% sulfate to reed and calamus respectively, and the effect of mine effluents on reed and calamus sulfur has been underestimated. This study reveals the key factors controlling plant isotope composition, and the use of nitrogen and sulfur isotope composition of aquatic plants can help quantify the level of influence of mining activities, and understand the biogeochemical cycle of nitrogen and sulfur in mining areas.

Identification of nitrate accumulation mechanism of surface water in a mining-rural-urban agglomeration area based on multiple isotopic evidence.

The accumulation of nitrate (NO3-) in surface waters resulting from mining activities and rapid urbanization has raised widespread concerns. Therefore, it is crucial to develop a nitrate transformation information system to elucidate the nitrogen cycle and ensure sustainable water quality management. In this study, we focused on the main river and subsidence area of the Huaibei mining region to monitor the temporal and spatial variations in the NO3- content. Multiple isotopes (δD, δ18O-H2O, δ15N-NO3-, δ18O-NO3-, and δ15N-NH4+) along with water chemistry indicators were employed to identify the key mechanisms responsible for nitrate accumulation (e.g., nitrification and denitrification). The NO3- concentrations in surface water ranged from 0.28 to 7.50 mg/L, with NO3- being the predominant form of nitrogen pollution. Moreover, the average NO3- levels were higher during the dry season than during the wet season. Nitrification was identified as the primary process driving NO3- accumulation in rivers and subsidence areas, which was further supported by the linear relationship between δ15N-NO3- and δ15N-NH4+. The redox conditions and the relationship between δ15N-NO3- and δ18O-NO3-, and lower isotope enrichment factor of denitrification indicated that denitrification was weakened. Phytoplankton preferentially utilized available NH4+ sources while inhibiting NO3- assimilation because of their abundance. These findings provide direct evidence regarding the mechanism underlying nitrate accumulation in mining areas, while aiding in formulating improved measures for effectively managing water environments to prevent further deterioration.

Carbon information disclosure quality, greenwashing behavior, and enterprise value.

As global warming becomes increasingly prominent, countries worldwide advocate for a low-carbon economy to cope with the pressure to reduce greenhouse gas emissions. The Chinese government has proposed a "dual carbon" goal of peaking carbon emissions by 2030 and becoming carbon neutral by 2060. The disclosure of carbon information by Chinese enterprises has attracted widespread attention from society. This study selects the constituents of the Social Responsibility Index of China Shanghai Stock Exchange from 2016 to 2020 as samples to empirically analyze the relationship between the level of carbon information disclosure and corporate value, and the moderating effect of greenwashing behavior. Results indicated that the quality of carbon disclosure is positively correlated with the enterprise value. Greenwashing behavior promotes the positive impact of carbon disclosure quality on enterprise value in the short run, but this promoting effect fades in the long run. We further found that the carbon information disclosure of non-heavy-pollution enterprises has a more obvious positive impact on enterprise value than that of heavily polluting enterprises. Additionally, the positive impact of carbon information disclosure on enterprise value is more visible among enterprises in a good legal environment than those in a poor legal environment. This study enriches the relevant literature on carbon information disclosure and enterprise "greenwashing" behavior and has practical significance for promoting China's low-carbon development in the context of ecological civilization and improving the enthusiasm for the quality of enterprise carbon information disclosure.

Copper isotope ratios allowed for quantifying the contribution of coal mining and combustion to total soil copper concentrations in China.

The most prominent source of Cu contamination in soils is metal mining and processing, partly since the Middle Age. However, coal mining and combustion can also cause (some) Cu contamination. We studied the distribution of Cu concentrations and isotope ratios in soils of the Huaibei coal mining area. The contribution of the coal mining and combustion to total Cu concentrations in soil was determined with a two-end-member mixing model based on the distinct δ65Cu values of the Cu emitted from coal mining and combustion and in native soil. The mean Cu concentration of 75 mg kg-1 exceeded the local soil background value (round to 22.13 mg kg-1). The similar δ65Cu value of grass near the coal mining and combustion operation as in gangue and flying ash indicated a superficial Cu contamination. Mining input was the dominant source of Cu in the contaminated soils, contributing up to 95% and on average 72% of the total Cu in the topsoils. The mining-derived Cu was leached to a depth of 65 cm, where still 29% of the Cu could be attributed to the mining emissions. Grasses showed lower δ65Cu values than the topsoils, because of the preferential uptake of light Cu isotopes. However, the Δ65Cugrass-soil was lower in the contaminated than the uncontaminated area because of superficial adsorption of isotopically heavy Cu from the mining emissions. Overall, in this study the distinct δ65Cu values of the mining-derived Cu emissions and the native soil allowed for the quantification of the mining-derived Cu and had already reached the subsoil and contaminated the grass by superficial adsorption in only 60 years of mining operation.

Zinc in soil reflecting the intensive coal mining activities: Evidence from stable zinc isotopes analysis.

In the mining area affected by coal mining activities for a long time, heavy metal Zn pollution poses a serious threat to soil quality and human health, and direct evidence showing the relationship between Zn accumulation mechanism in soils and mining activities is lacking. In this study, the Zn content and isotopes composition (δ66Zn) from soil and environmental samples around mining area were determined and analyzed to clarify the Zn characteristics in soil. Moreover, the distribution and source of Zn content in soil of mining area were analyzed by mathematical statistics, correlation analysis and isotope mass mixing model. The results showed that: (1) the Zn content in soil ranged from 95 to 327 mg·kg-1 (mean: 233 mg·kg-1), exceeding the control point and the soil background value of Anhui Province; (2) the results of Zn isotope analysis showed that Zn in soil mainly derived from the wind dispersion input of fine particles in gangue and fly ash, followed by the natural weathering of parent material; (3) isotopic mass mixing model can be used to distinguish the contribution of anthropogenic and natural Zn sources. Mining input was the main contribution source of Zn in soil (mean: 67%), followed by natural background (mean: 33%). The employment of Zn isotopes can effectively evaluate the impact of anthropogenic and natural long-term processes on Zn in the soil of the mining area, and provide important information for the formulation of soil metal pollution control measures.

Distribution, source and health risk assessment based on the Monte Carlo method of heavy metals in shallow groundwater in an area affected by mining activities, China.

Mining activities exert a far-reaching impact on the quality of groundwater, and health problems caused by heavy metal pollution have attracted global attention. In this study, inductively coupled plasma-mass spectrometry (ICP-MS) was employed to determine the contents of 8 heavy metals (Cd, Cr, As, Fe, Mn, Cu, Zn, and Pb) in shallow groundwater samples retrieved from a mining area in northern Anhui. Multivariate statistical methods were adopted to analyze the distribution and source of pollution and to evaluate 5% and 95% health risks based on Monte Carlo simulation. Fe, As and Cr significantly exceeded the safe drinking water standards of the World Health Organization (WHO). The average concentrations of As and Cr were as high as 46.45 µg/L and 133.96 µg/L, respectively. The correlation analysis and principal component analysis (PCA) results revealed that heavy metals are affected by complex factors, the main factor being human activities. The total carcinogenic health risks of Cr and As in adults were 2.49 × 10-3 and 3.43 × 10-4, respectively, which exceeded the maximum acceptable risk value (1 ×10-4) recommended by the United States Environmental Protection Agency (USEPA), affecting human health. According to the USEPA classification of hazardous ingestion (HI), at HI < 1, the impact of non-carcinogenic heavy metals on human health is negligible. These results indicate that local residents should strengthen the monitoring of Cr and As pollution in shallow groundwater.

Nitrate sources and transformations in surface water of a mining area due to intensive mining activities: Emphasis on effects on distinct subsidence waters.

The increase in NO3- content in surface water caused by intensive mining activities in Huainan City, China, has attracted considerable attention owing to the deterioration of water quality and the degradation of ecosystems in recent years. The Huainan mining area, which is highly disturbed by anthropogenic activities, was selected as a typical observation area, and the surface water was classified as open subsidence water (OSW), closed subsidence water (CSW), and river water (RW). Moreover, the hydrochemical parameters and the δ15N and δ18O values of nitrate were employed to quantitatively trace the sources and biochemical transformation of NO3-, and the contribution ratios of different NO3- sources were estimated using the stable isotope analysis in R based on the Bayesian model. There was evident nitrification in the study area, but no significant denitrification has occurred. A substantial portion of δ15N-NO3- demonstrated complex sources of NO3-. Compared with those of CSW, the NO3- compositions of the OSW approached to those of the RW due to river recharge and discharge, and were greatly affected by anthropogenic activities. The proportional contribution of manure and sewage in the OSW was found to be the highest with a mean value of 39.5 % ± 12.3 %, which was followed by that of mine drainage (mean: 22.1 % ± 13.1 %), chemical fertilizer (mean: 17.5 % ± 10.6 %), and soil organic nitrogen (mean: 17.5 % ± 11.6 %). In the RW, the highest mean contribution of manure sewage was 35.2 % ± 9.7 %, which was followed by that of chemical fertilizer (mean: 29.3 % ± 7.2 %), mine drainage (mean: 23.4 % ± 13.0 %), and soil organic nitrogen (mean: 10.9 % ± 8.3 %). In contrast, the contribution of chemical fertilizer to the CSW was the highest with a mean value of 33.9 % ± 13.6 %, which was followed by that of soil organic nitrogen (mean: 26.5 % ± 13.8 %), mine drainage (mean: 18.1 % ± 11.6 %). Therefore, NO3- in the surface water of the mining area primarily originates from chemical fertilizers and manure sewage. In addition, the contribution of mine drainage to nitrate in the study area indicates the potential impact of mining activities on surface water. These findings highlight the value of classifying different types of surface water in tracing NO3- contamination sources, and provide relevant theoretical basis for tracing nitrate sources in other areas.