Effect of Exogenous and Endogenous Sulfide on The Production and The Export of Methylmercury by Sulfate Reducing Bacteria

Mercury (Hg) is a global pollutant of environmental and health concern; its methylated form, methylmercury (MeHg) is a potent neurotoxin. Sulfur-containing molecules play a role in MeHg production by microorganisms. While sulfides are considered to limit Hg methylation, sulfate and cysteine were shown to favor this process. However, these two forms can be endogenously converted by microorganisms into sulfide. Here, we explore the effect of sulfide (produced by the cell or supplied exogenously) on Hg methylation. For this purpose, Pseudodesulfovibrio hydrargyri BerOc1 was cultivated in non-sulfidogenic conditions with addition of cysteine and sulfide as well as in sulfidogenic conditions. We report that Hg methylation depends on sulfide concentration in the culture rather than on the initial form of sulfur (cysteine, sulfide or sulfate) added, and was independent of hgcA expression. Interestingly, MeHg production was maximal at 0.1-0.5 mM of sulfides. Besides, a strong positive correlation between MeHg in the extracellular medium and the increase of sulfide concentrations was observed, suggesting a facilitated MeHg export with sulfide and/or higher desorption from the cell. We demonstrate that sulfides (exogenous or endogenous) play a key role in controlling mercury methylation, and should be considered when investigating the impact of Hg on natural environments.

Mercury Accumulation in Terrestrial Food Chains of the Liaohe Estuary Wetlands

Mercury is a global pollutant that can accumulate in organisms and endanger human health. This paper studied the soil, plants and animals in the light beach, Suaeda wing wetland, reed wetland and rice field in the Liaohe Estuary in 2018 and 2019, and determined the stable carbon and nitrogen isotopes of animals and plants to construct the food chain. The results show that from 2018 to 2019, the accumulation of mercury in the soil of the light beach, Suaeda winged wetland and reed wetland of the Liaohe Estuary continued to increase, but the accumulation of mercury in paddy soil showed a decreasing trend; the mercury content in plant samples also showed a certain degree There is a positive correlation between the accumulation of mercury in the food chain and the construction of trophic levels in the food chain. Mercury can carry out efficient biomagnification and bioaccumulation through the food chain.

Gaseous Elemental Mercury Exchange Fluxes over Air-Soil Interfaces in the Degraded Grasslands of Northeastern China

Mercury (Hg) is a global pollutant that may potentially have serious impacts on human health and ecologies. The gaseous elemental mercury (GEM) exchanges between terrestrial surfaces and the atmosphere play important roles in the global Hg cycle. This study investigated GEM exchange fluxes over two land cover types (including Artemisia anethifolia coverage and removal and bare soil) using a dynamic flux chamber attached to the LumexR RA915+ Hg analyzer during the growing season from May to September of 2018, in which the interactive effects of plant coverage and meteorological conditions were highlighted. The daily mean ambient levels of GEM and the total mercury concentrations of the soil (TSM) were determined to be 12.4 ± 3.6 to 16.4 ± 5.6 ng·m−3 and 32.8 to 36.2 ng·g−1, respectively, for all the measurements from May to September. The GEM exchange fluxes (ng·m−2·h−1) during the five-month period for the three treatments included the net emissions from the soil to the atmosphere (mean 5.4 to 7.1; range of −27.0 to 47.3), which varied diurnally, with releases occurring during the daytime hours and depositions occurring during the nighttime hours. Significant differences were observed in the fluxes between the vegetation coverage and removal during the growing months (p < 0.05). In addition, it was determined that the Hg fluxes were positively correlated with the solar radiation and air/soil temperature levels and negatively correlated with the air relative humidity and soil moisture under all the conditions (p < 0.05). Overall, the results obtained in this study demonstrated that the grassland soil served as both a source and a sink for atmospheric Hg, depending on the season and meteorological factors. Furthermore, the plants played an important inhibiting role in the Hg exchanges between the soil and the atmosphere.

Impacts of additional noise on the social interactions of a cooperatively breeding fish

Anthropogenic noise is a global pollutant known to affect the behaviour of individual animals in all taxa studied. However, there has been relatively little experimental testing of the effects of additional noise on social interactions between conspecifics, despite these forming a crucial aspect of daily life for most species. Here, we use established paradigms to investigate how white-noise playback affects both group defensive actions against an intruder and associated within-group behaviours in a model fish species, the cooperatively breeding cichlid Neolamprologus pulcher . Additional noise did not alter defensive behaviour, but did result in changes to within-group behaviour. Both dominant and subordinate females, but not the dominant male, exhibited less affiliation and showed a tendency to produce more submissive displays to groupmates when there was additional noise compared with control conditions. Thus, our experimental results indicate the potential for anthropogenic noise to affect social interactions between conspecifics and emphasize the possibility of intraspecific variation in the impacts of this global pollutant.

Microplastics in Surface Waters and Sediments from Guangdong Coastal Areas, South China

Microplastic is an emerging global pollutant that have attracted a great deal of attention from researchers and the public. Guangdong Province has a large population and a relatively well-developed economy, but lacks a modern pollution control system. Guangdong has a long coastline with varying levels of pollution, and little research has been conducted on microplastics. Therefore, we investigated the level of microplastic pollution in coastal areas of Guangdong Province, and the abundance of microplastics in surface waters and sediments at 13 sampling sites. The abundance of microplastics in surface water and sediment samples ranged from 850 to 3500 items/L and 433.3 to 4166.3 items/kg, respectively. Fiber is the main type of microplastics in both surface water and sediment. The sampled microplastics were typically transparent. Raman results show that the surface water sample mainly includes rayon (38.2%), polyethylene terephthalate (16.4%), and ethylene/vinyl acetate copolymer (12.7%). This study used the pollution load index method to evaluate the pollution risk of microplastics along the coast of Guangdong, and provided the basis for the formulation of environmental policy.

Substantial Nitrogen Oxide Pollution Is Embodied in the Bilateral Trade between China and the European Union

Against the backdrop of globalization and trade facilitation, the products consumed by a country are more and more relying on the importation of those products from other countries. Therefore, the pollutant emissions of products associated are transferred from consuming countries to exporting countries, which significantly changes the spatial distribution of global pollutant emissions. The objective of this research is to analyse the embodied nitrogen oxide (NOx) emissions in the trading process between China and the European Union (EU) and to further trace the interindustry and intercountry transfer paths. This study constructs a multiregional input–output (MRIO) model based on the latest EORA global supply chain database. The MRIO model quantitatively analyses the total NOx emissions from the production and consumption ends of China and the EU from 1995 to 2014. Important findings are derived from the empirical results as follows. (1) In 2014, China’s production end emissions were 1824.38 kilotons higher than those of the consumption end. By contrast, the situation in the EU was the opposite, i.e., production end emissions were 1711.97 kilotons lower than those of the consumption end. (2) In the trade between China and the EU, the EU is a net importer of embodied NOx, and China is a net exporter of embodied NOx. In 2014, 2.55% of China’s domestic NOx emissions were transferred to the EU in China-EU trade, accounting for 2.75% of China’s domestic consumption demand. (3) In 2014, Electricity, Gas and Water (397.75 kilotons), Transport (343.55 kilotons), Petroleum, Chemical and non-metallic Products (95.9 kilotons), Metal Products (49.88 kilotons), Textiles and Apparel (26.19 kilotons), are among the industries with the most embodied NOx emissions from China’s net exports during its two-way trade with the EU. (4) In the bilateral trade between the EU and China, many countries are in the state of embodied NOx net import. The top three net importers in 2014 were Germany (169.24 kilotons), Britain (128.11 kilotons), France (103.21 kilotons).

A novel cell membrane-targeting fluorescent probe for imaging endogenous/exogenous formaldehyde in live cells and zebrafish

Formaldehyde (FA) is not only an economic chemical but also a global pollutant. Although it brings economic development, it poses a threat to human health. It is also a kind...

Development of Method for Discontinuing Mercury-Containing Waste Including the Method of Analysis of Residual Concentrations

Environmental safety is one of the most important international and national tasks when using chemicals such as mercury, its compounds and mercury containing waste. Mercury (Hg) is a global pollutant. Constant anthropogenic mercury emissions and its presence in food chains affects human and ecosystem health and cause serious concerns. When released into the atmosphere with various emissions, mercury is deposited on the ground or water surface. Due to the global transport of mercury in the environment, its release is possible near sources of pollution, as well as at a remote distance. Keywords: mercury–containing wastes, Minamata Convention, immobilization