Mercury Exchange at the Air-Water-Soil Interface: An Overview of Methods

An attempt is made to assess the present knowledge about the methods of determining mercury (Hg) exchange at the air-water-soil interface during the past 20 years. Methods determining processes of wet and dry removal/deposition of atmospheric Hg to aquatic and terrestrial ecosystems, as well as methods determining Hg emission fluxes to the atmosphere from natural surfaces (soil and water) are discussed. On the basis of the impressive advances that have been made in the areas relating to Hg exchange among air-soil-water interfaces, we analyzed existing problems and shortcomings in our current knowledge. In addition, some important fields worth further research are discussed and proposed

Interactions of socioecological factors on the supply–demand balance of ecosystem services in the Yangtze River Economic Belt, China

A comprehensive understanding of how socioecological factors influence multiple ecosystem services (ESs) may provide stakeholders with a management tool to coordinate economic development and environmental protection. However, previous studies have focused more on the supply side compared with the demand of ESs. Furthermore, the underlying mechanisms for the changes in the supply–demand balance of ESs and their multiple drivers remain unclear. Therefore, in this study, an integrated theoretical framework was developed to assess the interactions of socioecological factors, including land use and cover, the social economy, climate, and topography, with the variations in ES supply, demand, and balance, which were mapped at the city scale in the Yangtze River Economic Belt (YREB). A variance inflation factor (VIF) was employed to detect the multicollinearity of the factors, and the sum of Akaike weights was used to simplify the driving factors and identify essential driving factors. We employed variation partitioning analysis (VPA) to reveal the effects of unique and combined drivers on ES supply, demand and balance. The results revealed that undersupply cities (11.93% of the area) were concentrated within the three national urban agglomerations and increased in area from upstream to downstream, whereas oversupply cities (88.07%) were distributed mainly in the surroundings of the urban agglomerations. According to the VPA, the essential driving factors effectively explain the variation in the ES supply, demand, and balance in the YREB. More importantly, these driving factors were simplified with no significant decrease in explanatory power. In oversupply cities, the ES changes were determined based on socioeconomic factors (urbanization rate and population density), land use/land cover (cropland, woodland, and unused land), and their interactions. In undersupply cities, population density (PD) explained the majority of the variation in ESs. However, the effects of climate and topography on ESs were more prominent at the scale of all cities in the YREB. In addition, PD displayed a significant negative correlation with ES supply and balance, but was positively related to ES demand in the undersupply cities. These findings contribute to a comprehensive understanding of the effects of the interactions among socioecological factors on the supply–demand balance of ESs. This study is informative for human well-being and sustainable socioeconomic development in the region

Differentiation between wild and artificial cultivated Stephaniae tetrandrae radix using chromatographic and flow-injection mass spectrometric fingerprints with the aid of principal component analysis

High-performance liquid chromatographic (HPLC) and flow-injection mass spectrometric (FIMS) fingerprinting profiles were used to differentiate between wild and artificial cultivated Stephaniae tetrandrae Radix samples. HPLC and FIMS fingerprints of 15 wild S. tetrandrae Radix samples and 12 artificial cultivated S. tetrandrae Radix samples were obtained and analyzed with the aid of principal component analysis (PCA). PCA of the fingerprints showed that the chemical differences between wild and artificial cultivated S. tetrandrae Radix samples could be differentiated by either HPLC or FIMS fingerprints. The HPLC fingerprints provided more chemical information but required longer analytical time compared with FIMS fingerprints. This study indicated that the wild samples contained higher concentrations of almost all of the major compounds than the cultivated samples. Three characteristic compounds which were responsible for the differences between the samples were tentatively identified with the aid of MS data. Furthermore, these three compounds, tetrandrine (TET), fangchinoline (FAN), and cyclanoline (CYC), were quantified. The HPLC and FIMS fingerprints combined with PCA could be used for quality assessment of wild and artificial cultivated S. tetrandrae Radix samples

Proper MgO/Al2O3 Ratio in Blast-Furnace Slag: Analysis of Proper MgO/Al2O3 Ratio Based on Observed Data

With the gradual depletion of high-quality iron-ore resources, ironmaking blast furnaces have gradually shifted to using high-content Al2O3 iron ore. Under this condition, the addition of MgO in the slag is adopted to alleviate operation problems caused by the high content of Al2O3. However, the proper value of the MgO/Al2O3 ratio for blast-furnace slag systems (Al2O3 = 8–25%) is not systematically studied. In this paper, we discuss the proper MgO/Al2O3 ratio on the basis of blast-furnace slag systems under different Al2O3 contents. On the basis of thermodynamics and phase-diagram analysis, it could be concluded that: (1) the MgO/Al2O3 ratio is not limited when Al2O3 in slag is less than 14%, (2) the MgO/Al2O3 ratio is required to be in the range of 0.40–0.50 when Al2O3 in the slag is 15–17%, and (3) the MgO/Al2O3 ratio should be 0.45–0.55 when Al2O3 in the slag is larger than 18%. The proper MgO/Al2O3 ratio value has been established in various industries, and it has achieved significant economic and social benefits

Rapid determination of plutonium isotopes in small samples using single anion exchange separation and ICP-MS/MS measurement in NH₃–He mode for sediment dating

To accurately determine ultra-trace Pu isotopes in small environmental samples, we explored ICP-MS/MS in NH3-He mode, and investigated mechanism of U-238 interference removal and measurement sensitivity improvement for plutonium isotopes. The interference of uranium and uranium hydrides was effectively eliminated using 0.4 mL/min NH3 as reaction gas by shifting them to U(NHm)(n)(+) and UH(NHm)(n)(+). The overall interference of uranium was reduced to <2.4 x 10 (-7), while remaining excellent Pu-239 sensitivity (13,900 Mcps/(mg/L)) mainly due to ion focusing effect of Pu by helium gas. On this basis, the purification of plutonium using a single AG1- x 4 column was proved to be sufficient for accurate determination of plutonium isotopes by the developed detection method, and the detection limits for the method were estimated to be 0.16 fg (0.4 mu Bq) for Pu-239, 0.046 fg (0.4 mu Bq) for Pu-240 and 0.039 fg (0.15 mBq) for Pu-241. The method was validated by analyzing plutonium isotopes in certificated reference materials and reported environmental samples of only 1-2 g. The analytical results of ultra-trace Pu isotopes in small amounts (similar to 1 g) of lake sediments obtained by the developed method were successfully applied to sediment dating

Spatiotemporal Distribution and Evolution of Digestive Tract Cancer Cases in Lujiang County, China since 2012

This study aims to analyze the spatiotemporal distribution and evolution of digestive tract cancer (DTC) in Lujiang County, China by using the geographic information system technology. Results of this study are expected to provide a scientific basis for effective prevention and control of DTC. The data on DTC cases in Lujiang County, China, were downloaded from the Data Center of the Center for Disease Control and Prevention in Hefei, Anhui Province, China, while the demographic data were sourced from the demographic department in China. Systematic statistical analyses, including the spatial empirical Bayes smoothing, spatial autocorrelation, hotspot statistics, and Kulldorff&rsquo;s retrospective space-time scan, were used to identify the spatial and spatiotemporal clusters of DTC. GM(1,1) and standard deviation ellipses were then applied to predict the future evolution of the spatial pattern of the DTC cases in Lujiang County. The results showed that DTC in Lujiang County had obvious spatiotemporal clustering. The spatial distribution of DTC cases increases gradually from east to west in the county in a stepwise pattern. The peak of DTC cases occurred in 2012&ndash;2013, and the high-case spatial clusters were located mainly in the northwest of Lujiang County. At the 99% confidence interval, two spatiotemporal clusters were identified. From 2012 to 2017, the cases of DTC in Lujiang County gradually shifted to the high-incidence area in the northwest, and the spatial distribution range experienced a process of &ldquo;dispersion-clustering&rdquo;. The cases of DTC in Lujiang County will continue to move to the northwest from 2018 to 2025, and the predicted spatial clustering tends to be more obvious

Greenhouse Gas Emissions from a Main Tributary of the Yangtze River, Eastern China

Rivers and streams are recognized as potential greenhouse gas (GHGs: CO2, CH4, and N2O) sources, contributing to global warming. However, GHG emissions from rivers and streams have received insufficient attention compared to other ecosystems (forests, grasslands, wetlands, etc.). In this study, dissolved GHG concentrations were measured in the Qingyijiang River, the longest tributary in the lower reaches of the Yangtze River, during two campaigns in September 2020 and April 2021. Our results showed that the Qingyijiang River was oversaturated with dissolved GHGs. The dissolved GHG concentration in the surface river water ranged from 8.70 to 67.38 μM CO2, 0.03 to 2.06 μM CH4, and 12.30 to 32.22 nM N2O. The average diffusive GHG emission rates were 31.89 ± 22.23 mmol CO2 m−2 d−1, 697.22 ± 939.82 μmol CH4 m−2 d−1, and 18.12 ± 7.73 μmol N2O m−2 d−1. The total emissions (CO2-e) were CO2 (58%) dominated, while CH4 (38%) played a moderate role in total emissions. Temporally, average GHG concentrations and fluxes from the studied river in April were higher than those in September. The concentration and flux of CH4 exhibited high spatial variability, similar to those in most rivers. In contrast, we found that there was no obvious spatial variability in CO2 and N2O concentrations but a significant difference among reaches in N2O fluxes. We found that water temperature and flow velocity were the potential drivers for the regulating spatial variability in GHGs. However, no other observed limnological parameters were found in governing the spatial patterns of GHGs, suggesting a complex combination of factors governing GHG fluxes; thus, these inconspicuous mechanisms underscore the need for further research. Overall, our study suggests that this river acts as a minor source of GHGs relative to other rivers, and CH4 cannot be ignored when considering aquatic carbon emissions

Greenhouse Gas Emissions from a Main Tributary of the Yangtze River, Eastern China

Rivers and streams are recognized as potential greenhouse gas (GHGs: CO2, CH4, and N2O) sources, contributing to global warming. However, GHG emissions from rivers and streams have received insufficient attention compared to other ecosystems (forests, grasslands, wetlands, etc.). In this study, dissolved GHG concentrations were measured in the Qingyijiang River, the longest tributary in the lower reaches of the Yangtze River, during two campaigns in September 2020 and April 2021. Our results showed that the Qingyijiang River was oversaturated with dissolved GHGs. The dissolved GHG concentration in the surface river water ranged from 8.70 to 67.38 &mu;M CO2, 0.03 to 2.06 &mu;M CH4, and 12.30 to 32.22 nM N2O. The average diffusive GHG emission rates were 31.89 &plusmn; 22.23 mmol CO2 m&minus;2 d&minus;1, 697.22 &plusmn; 939.82 &mu;mol CH4 m&minus;2 d&minus;1, and 18.12 &plusmn; 7.73 &mu;mol N2O m&minus;2 d&minus;1. The total emissions (CO2-e) were CO2 (58%) dominated, while CH4 (38%) played a moderate role in total emissions. Temporally, average GHG concentrations and fluxes from the studied river in April were higher than those in September. The concentration and flux of CH4 exhibited high spatial variability, similar to those in most rivers. In contrast, we found that there was no obvious spatial variability in CO2 and N2O concentrations but a significant difference among reaches in N2O fluxes. We found that water temperature and flow velocity were the potential drivers for the regulating spatial variability in GHGs. However, no other observed limnological parameters were found in governing the spatial patterns of GHGs, suggesting a complex combination of factors governing GHG fluxes; thus, these inconspicuous mechanisms underscore the need for further research. Overall, our study suggests that this river acts as a minor source of GHGs relative to other rivers, and CH4 cannot be ignored when considering aquatic carbon emissions