Mercury deposition and redox transformation processes in peatland constrained by mercury stable isotopes

Peatland vegetation takes up mercury (Hg) from the atmosphere, typically contributing to net production and export of neurotoxic methyl-Hg to downstream ecosystems. Chemical reduction processes can slow down methyl-Hg production by releasing Hg from peat back to the atmosphere. The extent of these processes remains, however, unclear. Here we present results from a comprehensive study covering concentrations and isotopic signatures of Hg in an open boreal peatland system to identify post-depositional Hg redox transformation processes. Isotope mass balances suggest photoreduction of HgII is the predominant process by which 30% of annually deposited Hg is emitted back to the atmosphere. Isotopic analyses indicate that above the water table, dark abiotic oxidation decreases peat soil gaseous Hg0 concentrations. Below the water table, supersaturation of gaseous Hg is likely created more by direct photoreduction of rainfall rather than by reduction and release of Hg from the peat soil. Identification and quantification of these light-driven and dark redox processes advance our understanding of the fate of Hg in peatlands, including the potential for mobilization and methylation of HgII.Mercury isotope signatures in groundwater, soil gas, solid peat, and atmosphere suggest that dark abiotic reduction of peat soil HgII to volatile Hg0 does not play a significant role in mobilizing Hg during peat mass los

Anaerobic copper toxicity and iron-sulfur cluster biogenesis in Escherichia coli

© 2017 American Society for Microbiology. While copper is an essential trace element in biology, pollution of groundwater from copper has become a threat to all living organisms. Cellular mechanisms underlying copper toxicity, however, are still not fully understood. Previous studies have shown that iron-sulfur proteins are among the primary targets of copper toxicity in Escherichia coli under aerobic conditions. Here, we report that, under anaerobic conditions, iron-sulfur proteins in E. coli cells are even more susceptible to copper in medium. Whereas addition of 0.2 mM copper(II) chloride to LB (Luria-Bertani) medium has very little or no effect on iron-sulfur proteins in wild-type E. coli cells under aerobic conditions, the same copper treatment largely inactivates iron-sulfur proteins by blocking iron-sulfur cluster biogenesis in the cells under anaerobic conditions. Importantly, proteins that do not have iron-sulfur clusters (e.g., fumarase C and cysteine desulfurase) in E. coli cells are not significantly affected by copper treatment under aerobic or anaerobic conditions, indicating that copper may specifically target iron-sulfur proteins in cells. Additional studies revealed that E. coli cells accumulate more intracellular copper under anaerobic conditions than under aerobic conditions and that the elevated copper content binds to the iron-sulfur cluster assembly proteins IscU and IscA, which effectively inhibits iron-sulfur cluster biogenesis. The results suggest that the copper-mediated inhibition of iron-sulfur proteins does not require oxygen and that iron-sulfur cluster biogenesis is the primary target of anaerobic copper toxicity in cells

Recent 210 Pb, 137 Cs and 241 Am accumulation in an ombrotrophic peatland from Amsterdam Island (Southern Indian Ocean)

Over the past 50 years, 210Pb, 137Cs and 241Am have been abundantly used in reconstructing recent sediment and peat chronologies. The study of global aerosol-climate interaction is also partially depending on our understanding of 222Rn-210Pb cycling, as radionuclides are useful aerosol tracers. However, in comparison with the Northern Hemisphere, few data are available for these radionuclides in the Southern Hemisphere, especially in the South Indian Ocean. A peat core was collected in an ombrotrophic peatland from the remote Amsterdam Island (AMS) and was analyzed for 210Pb, 137Cs and 241Am radionuclides using an underground ultra-low background gamma spectrometer. The 210Pb Constant Rate of Supply (CRS) model of peat accumulations is validated by peaks of artificial radionuclides (137Cs and 241Am) that are related to nuclear weapon tests. We compared the AMS 210Pb data with an updated 210Pb deposition database. The 210Pb flux of 98 ± 6 Bq·m−2·y−1 derived from the AMS core agrees with data from Madagascar and South Africa. The elevated flux observed at such a remote location may result from the enhanced 222Rn activity and frequent rainfall in AMS. This enhanced 222Rn activity itself may be explained by continental air masses passing over southern Africa and/or Madagascar. The 210Pb flux at AMS is higher than those derived from cores collected in coastal areas in Argentina and Chile, which are areas dominated by marine westerly winds with low 222Rn activities. We report a 137Cs inventory at AMS of 144 ± 13 Bq·m−2 (corrected to 1969). Our data thus contribute to the under-represented data coverage in the mid-latitudes of the Southern Hemisphere

Comment on : “A novel approach to peatlands as archives of total cumulative spatial pollution loads from atmospheric deposition of airborne elements complementary to EMEP data: Priority pollutants (Pb, Cd, Hg)” by Ewa Miszczak, Sebastian Stefaniak, Adam Michczyński, Eiliv Steinnes and Irena Twardowska

Acknowledgements We are thankful to P.G. Appleby, R. Bindler, J. Sonke, B. Smieja-Krol and three anonymous reviewers for their constructive comments.Peer reviewedPostprin

Unequal Anthropogenic Enrichment of Mercury in Earth's Northern and Southern Hemispheres

Remote Northern Hemisphere (NH) and Southern Hemisphere (SH) lake sediment and peat records of mercury (Hg) deposition have shown a ×3 to ×5 Hg enrichment since pre-industrial times (<1880 AD), leading to the perception that global atmospheric Hg enrichment is moderate and uniform across the hemispheres. Anthropogenic Hg emissions in the NH are, however, approximately 4 times higher than those in the SH. Here, we reconstruct atmospheric Hg deposition in four remote SH peatlands and review sediment and peat Hg records from both hemispheres. We observe a ×4 all-time enrichment in SH Hg deposition from pre-anthropogenic (<1450 AD) to the late 20th-century periods, which is lower than the large ×16 all-time enrichment in NH Hg deposition. We attribute this difference to lower anthropogenic Hg emissions in the SH, and higher natural atmospheric SH Hg concentrations, supported by ×2 higher natural background Hg accumulation in SH peat records. We suggest that the higher SH natural atmospheric Hg deposition reflects the SH land-ocean distribution, and is driven by important SH marine Hg emissions. Our findings indicate that atmospheric Hg background levels and anthropogenic enrichment in both hemispheres are different and should be taken into account in international Hg assessments and environmental policy

Holocene variability of atmospheric dust and mercury in the southern hemisphere

Les vents de sud-ouest (VSO) de l'hémisphère sud (HS) régularisent les cycles biogéochimiques du carbone de l'océan Austral en augmentant l'absorption du CO2 atmosphérique ou en faisant remonter les éléments nutritifs et le carbone des profondeurs de l'océan. Les changements d'intensité des VSO déterminent si l'océan Austral agit comme un puits ou une source nette de CO2, affectant ainsi la concentration de CO2 atmosphérique et donc le climat. Les VSO régularisent également la trajectoire des poussières dans l’HS et le cycle biogéochimique du mercure, ces deux paramètres pouvant donc être utilisés en retour pour suivre la dynamique des VSO. Or, les variabilités des VSO passées et sur le cycle historique du mercure sont mal connus. L'objectif de cette étude doctorale est d'améliorer la compréhension de la dynamique des VSO et du Hg atmosphérique d’abord dans un contexte de variabilité climatique naturelle puis sur une période affectée par le changement global en HS. Nous avons étudié l'enregistrement de la tourbe de l'île d'Amsterdam (AMS) ainsi que de trois autres tourbières situéesaux latitudes moyennes de l'SH, comme archives à long terme de la poussière atmosphérique et/ou du dépôt de mercure. A la limite nord des VSO et libre de perturbation anthropique, AMS est un site clé pour l'étude de la dynamique des VSO. Nous avons révélé qu’au cours de l'holocène, les dépôts de poussières et de Hg à AMS ont oscillé sur des échelles de temps millénaires. Les signatures isotopiques du Hg, sensibles aux précipitations, indiquent que des épisodes de fortes concentrations de poussières et de Hg correspondent à de faibles précipitations. Nous suggérons que ces événements ont été causés par un transfert polaire du VSO à AMS. Les dépôts de Hg reconstruits montrent également que le quadruplement du Hg anthropique observé dans l’HS depuis 1450 reste inférieur à l'enrichissement dans l'hémisphère nord, multiplié par 16 pendant la même période. Ces contributions scientifiques permettront d’améliorer les modèles climatiques et la politique environnementale internationale dans le cadre de la convention de Minamata sur le Hg.The Southern westerly winds (SWW) play an important role in regulating Southern Ocean carbon budget by enhancing the absorbance of atmospheric CO2 or resurfacing deep ocean carbon. Changes in SWW intensity are thought to determine whether Southern Ocean acts as a net CO2 sink or source, thereby affecting atmospheric CO2 concentration and then global climate. SWW also affect Southern Hemisphere (SH) dust trajectory and mercury biogeochemical cycling, which in turn can be used to trace SWW dynamics. Less is known about the past SWW variabilities and historical mercury cycle. The aim of this PhD study is to improve our understanding of the SWW trend and mercury deposition in the Holocene at remote SH sites by using geochemical and isotopic proxies in peat archives. We investigated Amsterdam Island (AMS) peat record coupled with three other peatlands in the SH mid latitudes as long-term archives of atmospheric dust and/or mercury deposition. At the northern edge of SWW and free from anthropogenic disturbance, AMS is a key site to study SWW dynamics. We find that during the Holocene, dust and mercury deposition at AMS oscillated on millennial time scales. Mercury isotope signatures, which are sensitive to rainfall inputs, indicate that high dust, high mercury events correspond to low rainfall. We suggest that these events were caused by a poleward shift of the SWW at AMS. The peat mercury records also inform on recent, human perturbation of the natural mercury cycle in the SH. We find however that the 4-fold anthropogenic mercury enrichment we observe in the SH since 1450AD, is smaller than the 16-fold enrichment in the northern hemisphere. These scientific contributions should help improve global climate models and international environmental policy under the Minamata convention on mercury

Variabilité Holocène des poussières atmosphériques et du mercure dans l’hémisphère Sud

The Southern westerly winds (SWW) play an important role in regulating Southern Ocean carbon budget by enhancing the absorbance of atmospheric CO2 or resurfacing deep ocean carbon. Changes in SWW intensity are thought to determine whether Southern Ocean acts as a net CO2 sink or source, thereby affecting atmospheric CO2 concentration and then global climate. SWW also affect Southern Hemisphere (SH) dust trajectory and mercury biogeochemical cycling, which in turn can be used to trace SWW dynamics. Less is known about the past SWW variabilities and historical mercury cycle. The aim of this PhD study is to improve our understanding of the SWW trend and mercury deposition in the Holocene at remote SH sites by using geochemical and isotopic proxies in peat archives. We investigated Amsterdam Island (AMS) peat record coupled with three other peatlands in the SH mid latitudes as long-term archives of atmospheric dust and/or mercury deposition. At the northern edge of SWW and free from anthropogenic disturbance, AMS is a key site to study SWW dynamics. We find that during the Holocene, dust and mercury deposition at AMS oscillated on millennial time scales. Mercury isotope signatures, which are sensitive to rainfall inputs, indicate that high dust, high mercury events correspond to low rainfall. We suggest that these events were caused by a poleward shift of the SWW at AMS. The peat mercury records also inform on recent, human perturbation of the natural mercury cycle in the SH. We find however that the 4-fold anthropogenic mercury enrichment we observe in the SH since 1450AD, is smaller than the 16-fold enrichment in the northern hemisphere. These scientific contributions should help improve global climate models and international environmental policy under the Minamata convention on mercury.Les vents de sud-ouest (VSO) de l'hémisphère sud (HS) régularisent les cycles biogéochimiques du carbone de l'océan Austral en augmentant l'absorption du CO2 atmosphérique ou en faisant remonter les éléments nutritifs et le carbone des profondeurs de l'océan. Les changements d'intensité des VSO déterminent si l'océan Austral agit comme un puits ou une source nette de CO2, affectant ainsi la concentration de CO2 atmosphérique et donc le climat. Les VSO régularisent également la trajectoire des poussières dans l’HS et le cycle biogéochimique du mercure, ces deux paramètres pouvant donc être utilisés en retour pour suivre la dynamique des VSO. Or, les variabilités des VSO passées et sur le cycle historique du mercure sont mal connus. L'objectif de cette étude doctorale est d'améliorer la compréhension de la dynamique des VSO et du Hg atmosphérique d’abord dans un contexte de variabilité climatique naturelle puis sur une période affectée par le changement global en HS. Nous avons étudié l'enregistrement de la tourbe de l'île d'Amsterdam (AMS) ainsi que de trois autres tourbières situéesaux latitudes moyennes de l'SH, comme archives à long terme de la poussière atmosphérique et/ou du dépôt de mercure. A la limite nord des VSO et libre de perturbation anthropique, AMS est un site clé pour l'étude de la dynamique des VSO. Nous avons révélé qu’au cours de l'holocène, les dépôts de poussières et de Hg à AMS ont oscillé sur des échelles de temps millénaires. Les signatures isotopiques du Hg, sensibles aux précipitations, indiquent que des épisodes de fortes concentrations de poussières et de Hg correspondent à de faibles précipitations. Nous suggérons que ces événements ont été causés par un transfert polaire du VSO à AMS. Les dépôts de Hg reconstruits montrent également que le quadruplement du Hg anthropique observé dans l’HS depuis 1450 reste inférieur à l'enrichissement dans l'hémisphère nord, multiplié par 16 pendant la même période. Ces contributions scientifiques permettront d’améliorer les modèles climatiques et la politique environnementale internationale dans le cadre de la convention de Minamata sur le Hg

Psychometric Properties and Measurement Invariance of the Brief Symptom Inventory-18 Among Chinese Insurance Employees

This study aimed to examine the psychometric properties and factorial invariance of the Brief Symptom Inventory-18 (BSI-18). Confirmatory factor analyses (CFAs) were performed to verify the BSI-18’s factor structure in a large sample of Chinese insurance professionals (N = 2363, 62.7% women; age range = 19–70). Multigroup CFA were performed to test the measurement invariance of the model with the best fit across genders. In addition, structural equation modeling was conducted to test the correlations between the BSI-18 and two covariates – social support perception and grit trait. Results indicated that the bi-factor model best fit the data and was also equivalent across genders. The BSI-18’s general factor, and somatization and depression dimensions were significantly related to social support perception and grit trait, whereas the anxiety dimension was not. Overall, our findings suggested that the BSI-18’s can be a promising tool in assessing general psychological distress in Chinese employees

A fast and accurate identification model for Rhinolophus bats based on fine-grained information

Abstract Bats are a crucial component within ecosystems, providing valuable ecosystem services such as pollination and pest control. In practical conservation efforts, the classification and identification of bats are essential in order to develop effective conservation management programs for bats and their habitats. Traditionally, the identification of bats has been a manual and time-consuming process. With the development of artificial intelligence technology, the accuracy and speed of identification work of such fine-grained images as bats identification can be greatly improved. Bats identification relies on the fine features of their beaks and faces, so mining the fine-grained information in images is crucial to improve the accuracy of bats identification. This paper presents a deep learning-based model designed for the rapid and precise identification of common horseshoe bats (Chiroptera: Rhinolophidae: Rhinolophus) from Southern China. The model was developed by utilizing a comprehensive dataset of 883 high-resolution images of seven distinct Rhinolophus species which were collected during surveys conducted between 2010 and 2022. An improved EfficientNet model with an attention mechanism module is architected to mine the fine-grained appearance of these Rhinolophus. The performance of the model beat other classical models, including SqueezeNet, AlexNet, VGG16_BN, ShuffleNetV2, GoogleNet, ResNet50 and EfficientNet_B0, according to the predicting precision, recall, accuracy, F1-score. Our model achieved the highest identification accuracy of 94.22% and an F1-score of 0.948 with low computational complexity. Heat maps obtained with Grad-CAM show that our model meets the identification criteria of the morphology of Rhinolophus. Our study highlights the potential of artificial intelligence technology for the identification of small mammals, and facilitating fast species identification in the future

A Holocene geochemical peat record for paleo-dust tracing in NE China

International audienc