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Through microscopic analyses (e.g., organic macerals, thin section observation, scanning electron microscope (SEM) imaging of fresh bedding planes via argon ion milling, and energy spectrum tests) combined with Rock-Eval analyses, this study systematically investigated the organic matter and pyrites in the continental shales in the 3rd submember of the Chang 7 Member (Chang 7³ submember) in the Yanchang Formation, Ordos Basin and determined their types and the formation and evolutionary characteristics. The results are as follows. The organic matter of the continental shales in the Chang 7³ submember is dominated by amorphous bituminites and migrabitumens, which have come into being since the early diagenetic stage and middle diagenetic stage A, respectively. The formation and transformation of organic matter is a prerequisite for the formation of pyrites. The Ordos Basin was a continental freshwater lacustrine basin and lacked sulphates in waters during the deposition of the Chang 7 Member. Therefore, the syndiagenetic stage did not witness the formation of large quantities of pyrites. Since the basin entered early diagenetic stage A, large quantities of sulfur ions were released as the primary organic matter got converted into bituminites and, accordingly, pyrites started to form. However, this stage featured poorer fluid and spatial conditions compared with the syndepositional stage due to withdraw of water, the partial formation of bituminites, and a certain degree of compaction. As a result, large quantities of pyrrhotite failed to transition into typical spherical framboidal pyrites but grew into euhedral monocrystal aggregates. In addition, pyrites are still visible in the migrabitumens in both microfractures and inorganic pores of mudstones and shales, indicating that the pyrite formation period can extend until the middle diagenetic stage A. [ABSTRACT FROM AUTHOR]

• Stable isotopes of riverine sulfate in arid environment were investigated. • Contributions of riverine sulfate sources were identified by an inverse model. • Evaporites dissolution dominates riverine sulfate source with spatial variations. • Lithology, precipitation and temperature dominate sulfur behaviors in river basins. The fate of riverine sulfate ion (SO 4 2-) and its environmental effects in arid environment are difficult to evaluate due to its complicated sources and strongly coupled behaviors with water cycle which is significantly modified by humans. To understand the sulfur cycle in aquatic systems in arid environment, the chemical and sulfur and oxygen isotopic compositions (δ34S SO4 and δ18O SO4) of major rivers around the Badain Jaran Desert, northwestern China, were investigated. These rivers had averaged SO 4 2- content at 1336 µmol/L, over 10 times higher than the global average. The δ34S SO4 and δ18O SO4 values ranged from -5.3‰ to +11.8‰ and +1.6‰ to +12.8‰, respectively. The end-member analysis and the inverse model showed that riverine sulfate was mainly derived from evaporites dissolution (0-87%), sulfide oxidation (13%-100%) and precipitation (0-33%), indicating heterogeneity in sulfur sources and behaviors along the river drainage with the lithology variations and climate gradients. Multiple isotopic tools combining with hydro-chemistry compositions could be applied to reveal sulfur cycle in arid environment. Based on the calculation, sulfide oxidation plays the primary role in the headwater and upstream in the Qilian-Mountains area, where sulfide is widely exposed. While the proportion of evaporites dissolution contributing to riverine sulfate is much higher in downstream in a drier environment. Besides, less precipitation and higher temperature can lead to more intensive evaporation, affecting the process of sulfide oxidation and enhancing the rates of evaporites dissolution and sulfate precipitation in the basin. [Display omitted] [ABSTRACT FROM AUTHOR]

To explore the deformation behavior and failure strength of sulfate saline silty clay at a temperature of -10℃ and confining pressures of 6~10 MPa, we have performed low-temperature triaxial shear tests on sulfate saline silty clay in Hexi region of Gansu province, China. The variation trend of deviatoric stress, volumetric strain and initial deformation modulus with confining pressure were analyzed. The results demonstrated that the stress-strain curve of frozen sulfate saline silty clay was hyperbolic and the deviatoric stress increased as the axial strain increased and was eventually constant. Owing to particle breakage and melting of ice, when the confining pressure, σ3>6 the strength decreased as the confining pressure increased and the sample exhibited volumetric shrinkage throughout the entire confining-pressure range. A constitutive model of frozen sulfate saline silty clay under high confining pressure has been proposed in combination with the Duncan Chang model and the validity of the model has been confirmed by comparison with test data. [ABSTRACT FROM AUTHOR]

Sulphate (SO42−) is a main component of PM2.5 in China. The chemical formation mechanisms of sulphate are complex, and many air quality models have been used to analyse these mechanisms. To improve the accuracy of Weather Research Forecast-Chemistry (WRF-Chem) on sulphate, an alternative method is proposed in this paper. Moreover, data assimilation is performed to adjust the chemical reaction rates of sulphate. Based on the original reactions, a new sulphate parameterisation scheme, which includes two hypothetical reactions and six undetermined parameters, was added. Based on the WRF-Chem/DART (Data Assistance Research Testbed) system, the near-ground concentrations of SO42−, SO2, NO2, O3 and particulate matter are assimilated to adjust the six parameters. After adjusting the parameters, the new scheme can effectively solve the underestimation of SO42− and overestimation of SO2. The simulation of SO42− improved as the mean bias changed from −13.1 µg m−3 to 3.5 µg m−3 while SO2 improved from 17.0 µg m−3 to 6.3 µg m−3. The temporal and spatial variation characteristics predicted by the new scheme are consistent with the theoretical research results, indicating that the complex mechanism of sulphate formation could be replaced by the temporal and spatial variation characteristics predicted by the new scheme and that the parameters can be adjusted by data assimilation. Furthermore, the reaction rates of the SO42− parameterisation scheme of the WRF-Chem model are improved in this study, and a new method for improving the accuracy of the air quality model is provided. [ABSTRACT FROM AUTHOR]

Supergene hydrous sulfate minerals form through the oxygenation and weathering of primary sulfides. In the Qinghai–Tibet Plateau region, with an alpine and dry environment, hydrous sulfate minerals oxidized from pyrite-bearing ore bodies provide important clues regarding the mineralization and environment. The Tuolugou sedimentary-exhalative (SEDEX) Co-Au deposit is located in the East Kunlun metallogenic belt of the northern Qinghai–Tibet Plateau in China. In the mining district, pyrite is the prevalent Co-hosting sulfide mineral, and is partially exposed on the surface to weathering and oxidation. Herein, we document the mineral assemblages in the supergene oxidation zone in the Tuolugou deposit, probe the genesis of supergene assemblage, and explore the implications for exploration. Three zones can be recognized in the oxidation zone of the Tuolugou deposit, including the outer zone (natrojarosite), intermediate zone (rozenite and aplowite), and inner zone (roemerite and melanterite). The mechanism of oxidation under aerobic and anaerobic conditions, as well as zoning with different oxidation degrees, are described in detail. Hydrous sulfates such as natrojarosite can be used as possible indicators of the exploration of albitite-related SEDEX deposit in this region. [ABSTRACT FROM AUTHOR]

The strongly 13C-depleted calcite in the Doushantuo cap dolostones (∼635 Ma) of South China is considered to form via thermochemical or biological oxidation of methane by sulfate in an environment with sulfate concentrations close to that of modern seawater (∼28 mM). Here we demonstrate that the coeval seawater sulfate levels were indeed low (∼1 to 3 mM) because all bulk δ34S values of pyrites are close to and higher than the coeval seawater, with only a few showing a wide in situ δ34S range from 5 to 62‰. Such low sulfate concentrations were initially consumed by sulfate reducing microorganisms to extremely low levels (<∼0.2 mM), and thus Mn-driven anaerobic oxidation of methane (AOM) by sulfate occurred in pore water to produce H 2 S, which was in turn oxidized by Mn oxides back to sulfate. Consequently, with increasing Mn reduction and decreasing sulfate concentrations in pore waters, the produced pyrite shows an increase of in situ δ34S values, and is in association with calcite with more negative δ13C values, and an inherited positive Ce anomaly from Mn oxides. Finally, the pyrite with the highest δ34S value may have co-precipitated with the 13C-depelted calcite (with a nadir of −58‰), and thus show similarly high Mn concentrations (∼20000 μg/g). This is the first report of sulfate-dependent AOM driven by Mn- or Fe- oxides from the entire Precambrian record. Such a previously unrecognized biogeochemical cycling during Marinoan global deglaciation may serve as the mechanism for major methane sink during the Proterozoic and Archean with low sulfate concentrations in the oceans. [ABSTRACT FROM AUTHOR]

The Ediacaran–Cambrian (E–C) transition was a critical period in Earth's history, and it was characterized by variable but potentially significant increases in atmospheric oxygen levels (pO2). Sulfate is an essential oxidant and plays a key role in regulating Earth's surface redox conditions. However, there is uncertainty regarding seawater sulfate levels during the E–C transition. To address this issue, organic carbon (δ13Corg) and pyrite sulfur isotope (δ34Spy) analyses of the Heyu section (the Dengying Formation) in the Sichuan Basin, South China, were carried out. The δ13Corg varies between −36.4‰ and −27.4‰, and δ34Spy ranges from −6.6‰ to 27.3‰. The TOC and pyrite content ranges from 0.13 wt.% to 4.28 wt.% and from 0.01 wt.% to 0.94 wt.%, respectively. The marine sulfate concentration was modeled using a one-dimensional diffusion–advection–reaction model (1D-DAR). The modeling results indicate that the seawater sulfate level remained at a relatively low level of ~2–6 mM. The increased pyrite burial at extensive marine anoxia during the terminal Ediacaran period was likely a driver of such a low sulfate level. [ABSTRACT FROM AUTHOR]

This study addresses the ongoing debate concerning the origin of ambient sulfate in northern China, and provides more evidence for primary sulfate from the perspective of source emission. An extensive field experiment was conducted, involving the collection of size-segregated particulate matter emitted under various coal types and combustion conditions for subsequent analysis. Our findings reveal that residential coal combustion (RCC) emits significant amounts of primary sulfate, constituting approximately 26.48 ± 15.43% of the particulate mass. Moreover, these emissions exhibit a strong association with NH 4 +, leading to the formation of stable ammonium sulfate compounds. The emission of sulfate is intricately linked to both coal quality and combustion conditions. Notably, the oversight of δ34S isotope enrichment in RCC particulate matter, which distinctly differs from the raw coal, introduces uncertainties in the quantitative assessment of sulfate sources and formation pathways. Therefore, more in-depth explorations are necessary to elucidate the precise processes involved in RCC sulfate transformation and to accurately determine its environmental impact. • Increase knowledge of RCC sulfate emission characteristics and influences. • Demonstrate RCC emits stable primary sulfate from multiple evidences. [ABSTRACT FROM AUTHOR]

Bacterial sulfate reduction (BSR) is the interaction between sulfates and organic matter that bacteria participate in during the early diagenetic stage. It is one of the important biogeochemical processes that affect the formation of sulfides and sulfur cycling. Due to the lack of sulfate in the lakes, there is relatively little research on lacustrine bacterial sulfate reduction (LBSR), and related research mainly focuses on marine sedimentation. Marine incursion and volcanic ash may bring sulfate to lakes, providing a possibility for the occurrence of LBSR. The process, main influencing factors, and identification methods of BSR are summarized systematically. Through comprehensive analysis, it is believed that the occurrence depth of LBSR is relatively shallow (about 10 cm). Sulfate concentration, total organic matter, and sulfate reducing bacteria activity are the main controlling factors of BSR. The petrological and geochemical characteristics of the product are commonly used indicators to determine whether BSR occurs. The Jimsar Sag is one of the important shale oil rich areas in China. Taking Jimsar Sag as an example, the identification of LBSR was attempted. Based on the characteristics of framboidal pyrite, columnar calcite, and fine-grained dolomite, comprehensive analysis suggests that LBSR has occurred in the Lucaogou Formation of the Jimsar Sag. BSR has a significant effect on the degradation of organic matter, and TOC is usually lower in areas with higher intensity. Therefore, BSR has impact on the enrichment of organic matter in shale. The relevant research may have reference significance for the enrichment of lacustrine organic matter and shale oil exploration. • The impact of marine incursion and volcanic ash on the sulfate content of lakes is considered. • Lacustrine bacterial sulfate reduction is identified and its intensity is analyzed in Jimsar Sag, the Junggar Basin. • The effects of lacustrine bacterial sulfate reduction on organic matter degradation is analyzed. [ABSTRACT FROM AUTHOR]

A series of dramatic oceanic and atmospheric events occurred in the immediate aftermath of the Marinoan “snowball Earth” meltdown ∼635 My ago. However, at the 10- to 100-ky timescale, the order, rate, duration, and causal-feedback relationships of these individual events remain nebulous. Nonetheless, rapid swings in regional marine sulfate concentrations are predicted to have occurred in the aftermath of a snowball Earth, due to the nonlinear responses of its two major controlling fluxes: oxidative weathering on the continents and pyrite burial in marine sediments. Here, through the application of multiple isotope systems on various carbon and sulfur compounds, we determined extremely 13C-depleted calcite cements in the basal Ediacaran in South China to be the result of microbial sulfate reduction coupled to anaerobic oxidation of methane, which indicates an interval of high sulfate concentrations in some part of the postmeltdown ocean. Regional chemostratigraphy places the 13C-depleted cements at the equivalent of the earliest Ediacaran 17O-depletion episode, thus confining the timing of this peak in sulfate concentrations within ∼50 ky since the onset of the deglaciation. The dearth of similarly 13C-depleted cements in other Proterozoic successions implies that the earliest Ediacaran peak in marine sulfate concentration is a regional and likely transient event. [ABSTRACT FROM AUTHOR]

Thermochemical sulfate reduction (TSR) commonly occurred in the dolostone reservoirs of the Upper Permian Changxing Formation (P3c) in the Yuanba (YB) gas field, Sichuan Basin, yet controversy remains regarding the source of sulfate required for TSR. To trace the source of the sulfate, sulfur and strontium isotopic compositions were measured for three diagenetic celestite (SrSO4) samples found in the P3c dolostone reservoirs in the YB gas field. In addition, the sulfur isotopic compositions of Carbonate-associated sulfates (CAS) from the P3c carbonates and spheroidal pyrites in dolomicrites from the P/T boundary (PTB) in the YB gas field were measured for comparative studies. The results show that the sulfur isotopic compositions of celestites are significantly heavier than those of the contemporaneous seawater, and these celestites have strontium isotopic values consistent with those of the host dolostones and contemporaneous seawater. The −33.68‰ fractionation in average δ34S values between pyrites and celestites indicated that their formation was likely to be related to bacterial sulfate reduction (BSR). During the P/T extinction event that accompanied the end-Permian regression, the reflux of brine directly precipitated 34S-rich celestites in the fractures and vugs of the dolostone reservoirs due to the BSR and the evaporation of seawater. These 34S-rich celesites and associated pore fluids provide a new explanation for the source of sulfate required for the late TSR. [ABSTRACT FROM AUTHOR]

In the construction industry, it is imperative to replace natural sand with manufactured sand. The environment in northwest China is very complex and harsh. The application of manufactured sand concrete in such a harsh environment needs scientific and comprehensive research to meet the requirements. However, there is a gap in the study of sulfate freeze-thaw resistance of manufactured sand concrete in the complex environment of Northwest China. Therefore, this study investigated the northwest environment, designed an indoor sulfate freeze-thaw cycle experiment system close to the real environment, and designed a conductive titration method to test the sulfate ion content in hardened concrete. The influence of the freeze-thaw cycle on the diffusion depth of sulfate ions in manufactured sand concrete was studied. Finally, the following conclusions are obtained: In the process of conductometric titration, hydrochloric acid is used as the dissolution solution, Ag 2 O and CO 2 are used as neutralizers, and Ba(NO 3) 2 is used as the titration solution, which can perfectly eliminate the significant influence ions in the test solution, and can accurately test the content of sulfate ions in hardened concrete. The sulfate ion content of concrete at different depths was tested, and it was found that the two sides of sulfate erosion caused by freeze-thaw cycles were mainly reflected in about 100 freeze-thaw cycles. The limit number of freeze-thaw cycles N 0 and the limit diffusion depth X 0 are proposed, and the diffusion equation of manufactured sand concrete under the action of sulfate freeze-thaw cycles is derived. The proposed diffusion parameter v is unique to the concrete, which can well judge the sulfate freeze-thaw resistance of the concrete. When v is closer to 0, it shows that the resistance of concrete to sulfate freeze-thaw erosion is better. For the northwest environment of China, the manufactured sand concrete should ensure v < 6; the environment in Northwest China has a very complex multi-factor erosion environment. It is worth noting that this study is only applicable to laboratory conditions. To improve the accuracy and reference value of experimental research, future research needs to add more comprehensive environmental impact factors and collect actual data in the northwest environment of China for verification. • A detailed conductivity test method for sulfate ion content in hardened concrete was designed. • The diffusion equation of manufactured sand concrete under sulfate freeze-thaw cycles is derived by proposing the limit number of freeze-thaw cycles N 0 and the limit diffusion depth X 0. • The diffusion parameter v proposed by is a new concept, which can be used to judge the key index of sulfate freeze-thaw damage, and is of great significance for evaluating the frost resistance of manufactured sand concrete in the northwest environment of China. [ABSTRACT FROM AUTHOR]

In this study, we designed a sensitivity test using the half number concentration of sulfate in the nucleation calculation process to study the aerosol-cloud interaction (ACI) of sulfate on clouds, precipitation, and monsoon intensity in the summer over the eastern China monsoon region (ECMR) with the National Center for Atmospheric Research Community Atmosphere Model version 5. Numerical experiments show that the ACI of sulfate led to an approximately 30% and 34% increase in the cloud condensation nuclei and cloud droplet number concentrations, respectively. Cloud droplet effective radius below 850 hPa decreased by approximately 4% in the southern ECMR, while the total liquid water path increased by 11%. The change in the indirect radiative forcing due to sulfate at the top of the atmosphere in the ECMR during summer was − 3.74 W·m−2. The decreased radiative forcing caused a surface cooling of 0.32 K and atmospheric cooling of approximately 0.3 K, as well as a 0.17 hPa increase in sea level pressure. These changes decreased the thermal difference between the land and sea and the gradient of the sea-land pressure, leading to a weakening in the East Asian summer monsoon (EASM) and a decrease in the total precipitation rate in the southern ECMR. The cloud lifetime effect has a relatively weaker contribution to summer precipitation, which is dominated by convection. The results show that the ACI of sulfate was one possible reason for the weakening of the EASM in the late 1970s. [ABSTRACT FROM AUTHOR]

The origins of atmospheric sulfate production have previously been explained by focusing on air quality models and complex chemical reaction processes. Here, we first report direct observations of sulfate production in stack plumes discharged from coal‐fired power plants, industrial boilers, and sintering plants equipped with wet desulfurization systems. Less than one third of the particulate SO42− in plumes is attributed to dust‐SO42− and SO3 measured in stacks. The SO2 aqueous‐phase oxidation process is critical in explaining the unknown sulfate formation in plume droplets with pH values ranging from 2.3 to 2.8. When the rapidly formed sulfate in wet plumes is included, a notable amount of underestimated sulfate (∼0.24 Tg in 2017) is emitted from industrial stacks in China and can partially explain the "missing sulfate" on driving most particle pollution episodes. Policy‐making targeting particulate emissions is suggested to substantially reduce sulfate emissions for further air quality improvement. Plain Language Summary: Sulfate aerosols are well known as an important atmospheric aerosol component, especially during haze periods. Their production pathway remains a mystery, and they are also referred to as missing sulfate. We show that sulfuric acid droplets are readily produced in wet plumes emitted from typical coal‐fired stationary sources. The freshly formed sulfate originates from the condensation and absorption of SO2 and SO3 emitted from stacks when the discharged flue gas cools in ambient air. We discover that the fast‐formed sulfate aerosols in the wet plumes from industrial stacks account for ∼31.4% of the directly emitted sulfate aerosols in China. This study advances our understanding of industrial particulate emissions and their contribution to atmospheric sulfate. Key Points: Acidic droplets with pH <3 formed in wet plumes are emitted from coal‐fired stationary sourcesThe SO42− concentrations in plumes grow explosively and are 2.8∼3.3 times higher than those in stacksSO2 aqueous‐phase oxidation process is critical in sulfate aerosol formation via plume droplets [ABSTRACT FROM AUTHOR]

Cracks will be introduced into mortar specimens and embedded copper sheets to simulate fractured concrete according to the designed 20 mm crack lengths and angles. By taking into consideration the actual environment of a hydro-fluctuation belt for a typical bank slope in the Three Gorges Reservoir Region of the Yangtze River, China, a dry–wet cycle testing program will be designed to study the mechanical properties of the fracture mortar specimens immersed in different sulfate solutions. The failure characteristics and modes of the fracture mortar specimens will be measured and analyzed. The tests results show that the strength initially decreased and then increased with an increasing crack angle from 0° to 90°, and this was the smallest for the specimens with a 45° angle. Deterioration occurred in the specimens subjected to dry–wet cycles in different sulfate solutions. The damage extent is expressed as the change in elasticity. A formula for damage evolution of the fracture specimens will be proposed and the relationship between the deformation properties and damage properties of the specimens will be developed for the combined action of dry–wet cycles and sulfate attack. Based on the proposed damage model, the damage evolution equation and elastic damage constitutive model will be derived under the combined action of dry–wet cycles and sulfate attack, and this damage constitutive relation could be used to the study damage evolution for the fracture mortar specimens under the combined effects of dry–wet cycles and sulfate attack. [ABSTRACT FROM AUTHOR]

The estimated contribution of "primary" combustion sulfate to the total atmospheric sulfate flux is inconsistent, hindering our interpretation of the atmospheric "missing sulfate". We expect combustion sulfate to inherit the characteristic triple oxygen isotope composition of air O 2 to variable degrees. To test the hypothesis, we extracted sulfate from soot samples collected from 48 residential chimneys throughout China. The mean sulfate's Δ′17O 0.5305 and δ18O values are −0.27 ± 0.06‰ and 12.8 ± 3.6‰, respectively, and the Δ′17O 0.5305 and δ18O values correlate negatively and extend to air O 2 's triple oxygen isotope composition as an endmember, suggesting that combustion sulfate is generated dominantly by S(IV) multiphase oxidation via O 2 in the plume, with possible additional pathways through •OH in aqueous films or droplets and NO 2 at soot surface. Oxygen sources (i.e., air O 2 , fuel, ambient moisture) and oxidation kinetics determine the triple oxygen isotope composition of combustion sulfate. The characterization of combustion sulfate's triple isotope composition helps to improve global and regional atmospheric sulfur chemistry models. • Triple oxygen isotope composition of combustion sulfate has an average value of −0.27‰ for the Δ′17O and 12.8‰ for the δ18O. • Oxygen sources (O 2 , fuel, water) and oxidation kinetics determine combustion sulfate's triple oxygen isotope composition. • The "primary" combustion sulfate is in fact "secondary" sulfate formed in chimney conduits and hot plumes. [ABSTRACT FROM AUTHOR]

• Concrete with a recycled aggregate content greater than 50% has a significant deterioration in its antifreeze performance and cannot meet its frost resistance requirements. • The Weibull model can better describe the damage variation of recycled concrete. • When the recycled aggregate content is 100%, it is only 40% of the antifreeze life of ordinary concrete. • It is suggested that the proportion of recycled aggregate should not be more than 30%. To study the frost resistance of recycled concrete in a sulfate-rich environment, we prepared recycled concrete with 0%, 30%, 50%, and 100% recycled aggregate replacement rate. The physical and mechanical properties of the recycled concrete in the coupled action of freeze-thaw cycles and a sulfate environment for different replacement rates of aggregate was then studied. We analyzed the micro-structure and the reaction products of the recycled concrete. We used a two-factor Weibull distribution model to establish the damage equation, then predict the service life of the recycled concrete. The results show that when the replacement rate of recycled aggregate increases, the physical and mechanical properties of the recycled concrete gradually deteriorate in the later stages of the freeze-thaw test. When the number of freeze-thaw cycles increases, ettringite and gypsum are gradually formed due to the reaction with sulfate. The Weibull model accurately describes the damage variation in the recycled concrete. Through the prediction of the service life of the recycled concrete, we found that the durability was reduced. Given our analysis, we found that the proportion of recycled aggregate should not exceed 30% to meet the requirements for durability design of a concrete structure in China (GB/T 50746-2008). [ABSTRACT FROM AUTHOR]

Marine evaporitic sulfates (gypsum and anhydrite) can record ancient seawater sulfur isotopic data; however, these records are scarce and widely dispersed owing to both restricted environments in which they form and their propensity to be eroded. The late Neoproterozoic–early Cambrian transition was a pivotal timeframe in Earth's history, witnessing the early evolution of animal life and major environmental changes. Seawater chemistry changed abruptly during this interval, including significant changes to the sulfur cycle as evidenced by unusually high sulfur isotopic values. This positive sulfur excursion, termed the Yudomski Event, has been reported previously from early and middle Cambrian units in Siberia, Iran, Australia, and India. In this study, we provide the first report of the Yudomski Event in early and middle Cambrian evaporites from the Tarim Basin, northwestern China. Our data support this event having been of global significance. We additionally report early and middle Ordovician sulfur data from China, which constrain the decline of the Yudomski Event to the late Cambrian. [ABSTRACT FROM AUTHOR]

• The driving damage mechanism for partially immersed cement mortars was examined. • Lowering the RH would accelerate physical sulfate attacks in drying parts. • An intermediate temperature of 35 °C causes more serious degradation than 20 and 50 °C. Concrete structures in salt lakes of western China and South China Sea deteriorate dramatically because of the aggressive salt, high temperature and low relative humidity (RH). In order to study the deterioration mechanism of cement-based materials in these severe environments, the damage progress of mortar specimens that partially exposed to sulfate solutions and under different ambient RH and temperatures was examined. The results indicate that the driving deterioration mechanism for cement mortars that partially exposed to Na 2 SO 4 solution is physical attacks in drying portions, while it is chemical attacks in immersed portions for cement mortars that partially exposed to MgSO 4 solution. Besides, lowering the ambient RH (e.g., from 80% to 50% and 30%) would promote a narrow but supersaturated evaporation interface zone, which accelerates the salt crystallization and eventually surface scaling. While the relatively high ambient RH (80%) causes a broad diffusion zone where the chemical related expansion and cracking formed. Moreover, an intermediate temperature of 35 °C is proved to produce the most severely deterioration when compared to the temperature of 20 and 50 °C. [ABSTRACT FROM AUTHOR]

Sulfate plays an important role in atmospheric haze in China, which has received considerable attention in recent years. Various types of parameterization methods and heterogeneous oxidation rates of SO 2 have been used in previous studies. However, properly representing heterogeneous sulfate formation in air quality models remains a big challenge. In this study, we quantified the heterogeneous oxidation reaction using experimental results that approximate the haze conditions in China. Firstly, a series of experiments were conducted to investigate the heterogeneous uptake of SO 2 with different relative humidity (RH) levels and the presence of NH 3 and NO 2 on natural dust surfaces. Then the uptake coefficients for heterogeneous oxidation of SO 2 to sulfate at different RH under NH 3 and NO 2 coexistence were parameterized based on the experimental results and implemented in the Community Multiscale Air Quality modeling system (CMAQ). Simulation results suggested that this new parameterization improved model performance by 6.6% in the simulation of wintertime sulfate concentrations for Beijing. The simulated maximum growth rate of SO 4 2− during a heavy pollution period increased from 0.97 μg m−3 h−1 to 10.11 μg m−3 h−1. The heterogeneous oxidation of SO 2 in the presence of NH 3 contributed up to 23% of the sulfate concentration during heavy pollution periods. Image 1 • Uptake coefficients of SO 2 on dust with coexistence of NH 3 and NO 2 were obtained. • New parameterization was proposed based on experimental results under different RHs. • The new parameterization can improve sulfate simulation in wintertime in CMAQ. • Impact of NH 3 on heterogeneous formation of sulfate in wintertime is non-negligible. [ABSTRACT FROM AUTHOR]

Understanding the primary emissions of sulfate (SO 4 2−), nitrate (NO 3 −), and ammonium (NH 4 +) (SNA) from solid fuels (coal and biomass) combustion is important to study their roles in haze formation and particle growth. In this study, direct emissions of SNA and other inorganic ions (including Na+, K+, Mg2+, Ca2+, and Cl−) in fine particulate matter (PM 2.5) from residential coal combustion (RCC) and biomass burning (BB) were quantified through combustion chamber experiments. Emission factors (EFs) of the total quantified ions for the five types of solid fuels are in the range of 178–3880 mg/kg, accounting for 5.8%–41.1% of the emitted PM 2.5 mass. The average proportions of SO 4 2−, NO 3 −, and NH 4 + in PM 2.5 emitted from RCC are 3.7%, 0.9%, and 1.0%, respectively, in comparison to 1.3%, 0.8%, and 0.1%, respectively, for BB. Despite the variations of SNA proportions seen among the solid fuel types, SO 4 2− is the most dominating inorganic ion, consistent with the emission profiles shown in other literatures. Similar mass fraction and its range of SO 4 2− are found between RCC and ambient in the northern cities, implying that the primary emission from RCC is a significant source contributor to atmospheric SO 4 2−, particularly in wintertime. According to the EFs and mass fractions of SNA determined for the solid fuels, the contribution of secondary formation to atmospheric SO 4 2− should be overestimated in ambient PM 2.5 source apportionment. [Display omitted] • Primary emission from RCC is a significant source of SO 4 2− in northwest China. • Atmospheric NH 4 + and NO 3 − are more influenced by sources rather than RCC and BB. • Secondary SO 4 2 formation might be overestimated. [ABSTRACT FROM AUTHOR]

The non-linear relationship between particle sulfate and SO 2 is still unclear. Continuous observations were conducted in a typical city in Northern China from 2017 to 2020. SO 2 concentration continually decreased, however, the SO 4 2− concentration and the sulfur oxidation ratio increased in 2018–2019. The major reason might be the variations of sulfate formation by the aqueous-phase reactions, especially for the O 2 + TMI oxidation (oxygen catalyzed by transition-metal ions). Particle pH, SO 2 , and Mn concentration were the main factors affecting the O 2 + TMI reaction rate. Sensitivity analysis indicated that the decrease of the O 2 + TMI reaction rate caused by SO 2 or Mn concentration dropping by half can only offset the increased rate caused by a 0.1 unit decrease in particle pH. Considering the actual atmospheric environment in Northern China, if the particle pH continues to drop, the slow decline of SO 2 and Mn concentration may not prevent the increase in the O 2 + TMI oxidation rate. In addition to meteorological parameters, the concentrations of SO 4 2−, crustal elements, and total ammonium were the primary factors for the decrease in particle pH in the past 3 years. Therefore, the impact of pH on sulfate formation must be considered when controlling dust and ammonia emissions. [Display omitted] • Changes in O 2 + TMI reaction rates partly explained the non-linear relationship between SO 4 2− and SO 2 ; • If the pH continues to drop, the slow decline of SO 2 and Mn may not offset the increase in the O 2 + TMI oxidation rate. • The concentrations of SO 4 2−, crustal elements and total ammonium were the primary factors for the decrease in particle pH. [ABSTRACT FROM AUTHOR]

Epiphyton, Renalcis, and Girvanella are ubiquitous genera of calcified cyanobacteria/algae from Early Paleozoic shallow-marine limestones. One genus, Epiphyton, is characterized by a particular dendritic outline, and extensive research has revealed the morphology of calcified remains although little information on cellular structure is known. The mass occurrence of calcified Epiphyton in microbialites from Cambrian Miaolingian, the Mianchi area of North China is preserved as black clots within thrombolites and have dendritic and spherical outlines when viewed with a petrographic microscope. These remains, visible under scanning electron microscope (SEM), also comprise spherical or rectangle capsules. These capsules are made up from external envelopes and internal calcite with numerous pits, which closely resemble modern benthic coccoid cyanobacteria. These pits are between 2 μm and 4 μm in diameter and are interpreted here to represent the remnants of degraded coccoid cells, while the calcite that surrounds these pits is interpreted as calcified thin extracellular polymeric substances (EPS). In contrast, associated capsular envelopes represent thick EPS mineralized by calcium carbonate with an admixture of Al-Mg-Fe silicates. Dendritic ‘thalli’ are typically stacked apically because of the repeated growth and calcification of these capsules. Carbon and oxygen isotope results are interpreted to indicate that both photosynthesis and heterotrophic bacterial metabolism (especially sulfate reducing bacteria) contributed to carbonate precipitation by elevated alkalinity. Epiphyton are therefore here interpreted as colonies of calcified coccoid cyanobacteria, and the carbonate-oversaturated seawater during the Cambrian was conducive to their mineralization. [ABSTRACT FROM AUTHOR]

The adverse respiratory health effects of PM 2.5 have been studied. However, the epidemiological evidence for the association of specific PM 2.5 sources with health outcomes is still limited. This study investigated the association between PM 2.5 components and sources with a biomarker of acute respiratory inflammation (FeNO) in guards. Personal exposure was estimated by microenvironment samplers and FeNO measurements were carried out before, during and after the Victory Day Military Parade in Beijing. Four sources were determined by factor analysis, including urban pollution, dust, alloy steel abrasion and toxic metals. A mixed-effect model was used to estimate the associations of FeNO with PM 2.5 sources and chemical constituents, controlling for age, BMI, smoke activity, physical activity, waist circumference, temperature and relative humidity. In summary, large concentration decreases in PM 2.5 concentration and PM 2.5 chemical constituents were observed in both roadside and indoor environments during the air control periods, immediately followed by statistically significant decreases in FeNO of roadside guards and patrol guards. Besides, statistically significant increases in FeNO were found to be associated with interquartile range (IQR) increases in some pollutants, with an increase of 1.45 ppb (95% CI: 0.69, 2.20), 0.65 ppb (95% CI: 0.13, 1.17), 1.48 ppb (95% CI: 0.60, 2.35), 0.82 ppb (95% CI: 0.44, 1.20), 0.77 ppb (95% CI: 0.42, 1.11) in FeNO for mass, sulfate, BC, Ca 2 + and Sm, respectively. In addition, compared to alloy steel abrasion and toxic metals, urban pollution and dust factors were more associated with acute airway inflammation for highly-exposed populations. [ABSTRACT FROM AUTHOR]

Zhundong coal as a high quality steam coal has not been widely utilized due to severe fouling and slagging problems during combustion. It is crucial to reveal the slagging and fouling mechanisms in a boiler burning Zhundong coal. In this paper, the properties of ash deposits collected from various heat transfer surfaces in a 330 MW boiler were characterized by ICP-OES, SEM−EDX, and XRD. These results were also verified by an experiment burning Zhundong coal in a drop-tube furnace and thermodynamic calculation by the software FactSage. The results indicated the ash deposited on different heat transfer surfaces in 330 MW boiler burning Zhundong coal could be classified into silicates and sulfates based on their elemental and mineral analysis. Further, the ash deposited on the division panel superheater is obviously divided into three layers. In the first layer, wollastonite and sodium silicate are the main minerals with the contents of quartz and feldspar being relatively small. The types of mineral in the second layer are the same with the first layer, but their contents are different from the first layer. Meanwhile, the amount of crystalline phase in the third layer is lower than that of the first and second layer. In addition, the temperature of the flue gas or the tube played an important role in the mechanism of ash deposition. Thermodynamics calculation also shows CaSO 4 can be formed at all temperatures and there only exists CaSiO 3 formed in the range 900–1200 °C. The ash deposits along the flue gas flow attributes to sulfates, silicates and sulfates, respectively. The result of the thermodynamic calculation is in accordance with the experiment results obtained in the drop-tube furnace. [ABSTRACT FROM AUTHOR]

The crystal structure of goldichite KFe(SO4)2⋅4H2O was determined on a single crystal from the Baiyinchang copper deposit, Gansu, China. [P121/c1, a = 10.395(2), b = 10.475(2), c = 9.0875(18) Å, β = 101.65(3)°, V = 969.1(3) Å3, Z = 4]. All non-H atoms were refined with anisotropic displacement parameters and positions of H-atoms were determined by difference Fourier methods and refined from X-ray diffraction data. The crystal structure of goldichite consists of corrugated sheets parallel to the (100) plane by sharing corners between FeO6 octahedra and SO4 tetrahedra. The interstitial potassium atom exhibits a [KO7(H2O)2] nine-fold coordination, which shares edges to form a column parallel to the c-axis and to build a slab with the corrugated sheet. These slabs are linked in the [100] direction through a network of hydrogen bonds. Three types of hydrogen bonds involve links of slabs: Ow(3)-H(3B)···O(1), Ow(6)-H(6B)···O(11) and Ow(9)-H(9B)···O(11). The FTIR spectrum of goldichite shows a strong absorption between ~3384 cm−1 and ~3592 cm−1, which is in accordance with the O-H···O distances derived from structure data. [ABSTRACT FROM AUTHOR]

Mining activity is an increasingly important stressor for freshwater ecosystems. However, the mechanism on how sulfate-rich mine drainage affects freshwater ecosystems is largely unknown, and its potential ecological risk has not been assessed so far. During 2009–2016, water and macroinvertebrate samples from 405 sample sites were collected along the mine drainage gradient from circum-neutral to alkaline waters in Hun-Tai River, Northeastern China. Results of linear regressions showed that sulfate-rich mine drainage was significantly positively correlated with the constituents typically derived from rock weathering (Ca 2 + , Mg 2 + and HCO 3 – + CO 3 2 − ); the diversity of intolerant stream macroinvertebrates exhibited a steep decline along the gradient of sulfate-rich mine drainage. Meanwhile, stressor-response relationships between sulfate-rich mine drainage and macroinvertebrate communities were explored by two complementary statistical approaches in tandem (Threshold Indicator Taxa Analysis and the field-based method developed by USEPA). Results revealed that once stream sulfate concentrations in mine drainage exceeded 35 mg/L, significant decline in the abundance of intolerant macroinvertebrate taxa occurred. An assessment of ecological risk posed by sulfate-rich mine drainage was conducted based on a tiered approach consisting of simple deterministic method (Hazard Quotient, HQ) to probabilistic method (Joint Probability Curve, JPC). Results indicated that sulfate-rich mine drainage posed a potential risk, and 64.62–84.88% of surface waters in Hun-Tai River exist serious risk while 5% threshold (HC 05 ) and 1% threshold (HC 01 ) were set up to protect macroinvertebrates, respectively. This study provided us a better understanding on the impacts of sulfate-rich mine drainage on freshwater ecosystems, and it would be helpful for future catchment management to protect streams from mining activity. [ABSTRACT FROM AUTHOR]

Sulfate and nitrate formed on dust aerosols can considerably affect particles' physicochemical properties due to their high hygroscopicity. Dust reverse-transport (DRT) events can occur in eastern China when dust plumes undergo a distinct turn caused by Asian highs or cyclones, resulting in the re-appearance of the dust plume in one place but with anthropogenic pollutants mixed in. In this study, three DRT events were identified at a coastal city, Qingdao. The secondary sulfate and nitrate in PM 2.5 collected during the DRT events were estimated according to the mass concentration of water-soluble ions and dust tracer metal. Several key factors, including heterogeneous reactions on aerosols, photochemical conversions in the air, and precursors' abundance in dust plumes, affected the aging of dust plumes. In the presence of adequate ammonium and high-level oxidants in the air, sulfate and nitrate were efficiently produced under moderate/high humidity conditions when DRT events occurred to the south of Qingdao. The proportions of the secondary sulfate/nitrate in total concentrations exceeded 90%, in which 20.8%–43.1% of secondary nitrate was formed on dust particles. In contrast, when the DRT occurred to the north of Qingdao with low relative humidity and low [NH 4 +]/[SO 4 2−] ratio, the growth of sulfate and nitrate was small. This study reveals a manner of efficient sulfate and nitrate formation in dust plumes in the continental atmosphere. • Dust reverse-transport phenomena were used to study the aging process of dust plumes. • East Asian dust plumes were prone to aging when transported to the south of Qingdao. • Secondary sulfate/nitrate formation was strongly influenced by the precursors' concentrations on dust transport pathways. [ABSTRACT FROM AUTHOR]

Sediment bacteria communities in shrimp pond are intricately linked to ecosystem function and the provision of services, such as nutrient cycling and excess nutrient metabolism in sediment. However, little is known about the main factor (assembly processes) governing abundant and rare bacterial diversity in land-based shrimp ponds. This study quantified the composition, spatial distribution, and assembly mechanisms of bacterial communities sampled from the sediment of 78 land-based shrimp ponds distributed along approximately 1700 km of the southeastern coastal zone of China. This was done using 16S rRNA gene amplicon sequencing. The bacterial community similarities decreased with spatial distance. Variation of bacterial community was mostly attributed to deterministic (environmental filtering) processes. Sediment sulfate concentrations regulated the balance between stochastic and deterministic bacterial community assembly processes, as indicated by the negative relationship between the stochasticity ratio, and network analysis highlighted increasingly sparse interconnections and less frequent co-occurrences among bacterial communities under greater sulfate concentrations. Our results demonstrate the negative impacts of sulfates associated with coastal aquaculture on sediment bacterial community dynamics, community assembly, and ecosystem function. • Sediment sulfate concentrations regulate balance between stochastic and deterministic bacterial community assembly processes. • Increasing sulfate concentration reduces network complexity or connectivity. • Sulfate content is an important environmental factor influencing bacterial richness [ABSTRACT FROM AUTHOR]

• We build a satellite-driven machine learning model to predict particulate sulfate concentrations across China using atmospheric big data from 2005 to 2018. • Our daily and monthly mean sulfate predictions agree well with ground observations with an out-of-bag cross-validation R2 of 0.68 and 0.93, respectively. • Population-weighted national annual mean sulfate concertation was relatively stable before the enforcement of the Air Pollution Prevention and Control Action Plan in 2013, then significantly decreased by 28.7% from 2013 to 2018. • The national annual mean total non-accidental and cardiopulmonary deaths attributed to sulfate decreased by 40.7% and 42.3% from 2013 to 2018, respectively. Ambient fine particulate matter (PM 2.5) pollution is a major environmental and public health challenge in China. In the recent decade, the PM 2.5 level has decreased mainly driven by reductions in particulate sulfate as a result of large-scale desulfurization efforts in coal-fired power plants and industrial facilities. Emerging evidence also points to the differential toxicity of particulate sulfate affecting human health. However, estimating the long-term spatiotemporal trend of sulfate is difficult because a ground monitoring network of PM 2.5 constituents has not been established in China. Spaceborne sensors such as the Multi-angle Imaging SpectroRadiometer (MISR) instrument can provide complementary information on aerosol size and type. With the help of state-of-the-art machine learning techniques, we developed a sulfate prediction model under support from available ground measurements, MISR-retrieved aerosol microphysical properties, and atmospheric reanalysis data at a spatial resolution of 0.1°. Our sulfate model performed well with an out-of-bag cross-validation R2 of 0.68 at the daily level and 0.93 at the monthly level. We found that the national mean population-weighted sulfate concentration was relatively stable before the Air Pollution Prevention and Control Action Plan was enforced in 2013, ranging from 10.4 to 11.5 µg m−3. But the sulfate level dramatically decreased to 7.7 µg m−3 in 2018, with a change rate of −28.7 % from 2013 to 2018. Correspondingly, the annual mean total non-accidental and cardiopulmonary deaths attributed to sulfate decreased by 40.7 % and 42.3 %, respectively. The long-term, full-coverage sulfate level estimates will support future studies on evaluating air quality policies and understanding the adverse health effect of particulate sulfate. [ABSTRACT FROM AUTHOR]

The rapid increase in urbanization and intensive coal mining activities have accelerated the deterioration of surface water quality. Environmental problems caused by the accumulation of nitrate and sulfate from natural, urban, and agricultural sources have attracted extensive attention. Information on nitrate and sulfate sources and their transformations is crucial for understanding the nitrogen and sulfur cycles in surface water. In this study, we monitored nitrate and sulfate in three representative rivers in mining cities in northern China. The main pollution sources and biogeochemical processes were identified by using stable isotopes (δD, δ18O H2O , δ15N, δ18O NO3 , δ34S and δ18O SO4) and hydrochemistry. The contribution of natural and anthropogenic sources was quantitatively estimated based on a Bayesian mixed model. The results indicated a large variation in sulfate and nitrate sources between the different rivers. Nitrate in the Tuohe River mainly derived from manure/sewage (57.9%) and soil N (26.9%), while sulfate mainly derived from manure/sewage (41.7%) and evaporite dissolution (26.8%). For the Suihe River, nitrate was primarily sourced from chemical fertilizer (37.9%) and soil nitrogen (34.8%), while sulfate was mainly sourced from manure/sewage (33.1%) and chemical fertilizer (21.4%). For the Huihe River, nitrate mainly derived from mine drainage (56.6%) and manure/sewage (30.6%), while sulfate predominantly originated from mine drainage (58.3%) and evaporite dissolution (12.9%). Microbial nitrification was the major pathway for the migration and transformation of nitrate in the surface water. However, denitrification and bacterial sulfate reduction (BSR) did not play a significant role as aerobic conditions prevailed. In this study, we elucidated the sources and transformation mechanisms of nitrate and sulfate. Additionally, we provided a reference for formulating a comprehensive strategy for effective management and remediation of surface water contaminated with nitrate and sulfate in mining cities. [Display omitted] • Natural and anthropogenic sources of nitrates and sulfates were quantified. • Water from the Tuohe, Suihe, and Huihe Rivers and a subsidence zone were studied. • Nitrification was the major pathway for nitrate transformation in surface water. • Multiple sources of pollutants could be identified simultaneously. • Denitrification and bacterial sulfate reduction (BSR) were not observed. [ABSTRACT FROM AUTHOR]

To provide more reasonable references for remedying underground water, fuel leak was simulated by establishing an experimental model of a porous-aquifer sand tank with the same size as that of the actual tank and by monitoring the underground water. In the tank, traditional gasoline and ethyl alcohol gasoline were poured. This study was conducted to achieve better understanding of the migration and distribution of benzene, toluene, ethyl benzene, and xylene (BTEX), which are major pollutants in the underground water. Experimental results showed that, compared with conventional gasoline, the content peak of BTEX in the mixture of ethyl alcohol gasoline appeared later; BTEX migrated along the water flow direction horizontally and presented different pollution halos; BTEX also exhibited the highest content level at 45 cm depth; however, its content declined at the 30 and 15 cm depths vertically because of the vertical dispersion effect; the rise of underground water level increased the BTEX content, and the attenuation of BTEX content in underground water was related to the biodegradation in the sand tank, which mainly included biodegradation with oxygen, nitrate, and sulfate. [ABSTRACT FROM AUTHOR]

In recent years in a few Chinese megacities, fog events lasting one to a few days have been frequently associated with high levels of aerosol loading characterized by high sulfate (as high as 30 μg m-3), therefore termed as haze-fog events. The concomitant pollution characteristics include high gas-phase mixing ratios of SO2 (up to 71 ppbv) and NO2 (up to 69 ppbv), high aqueous phase pH (5-6), and smaller fog droplets (as low as 2 μm), resulting from intense emissions from fossil fuel combustion and construction activities supplying abundant Ca2+. In this work, we use an observation-based model for secondary inorganic aerosols (OBM-SIA) to simulate sulfate formation pathways under conditions of haze-fog events encountered in Chinese megacities. The OBM analysis has identified, at a typical haze-fogwater pH of 5.6, the most important pathway to be oxidation of S(IV) by dissolved NO2, followed by the heterogeneous reaction of SO2 on the aerosol surface. The aqueous phase oxidation of S(IV) by H2O2 is a very minor formation pathway as a result of the high NOx conditions suppressing H2O2 formation. The model results indicate that the unique cocktail of high fogwater pH, high concentrations of NO2, SO2, and PM, and small fog droplets are capable of greatly enhancing sulfate formation. Such haze-fog conditions could lead to rapid sulfate production at night and subsequently high PM2.5 in the morning when the fog evaporates. Sulfate formation is simulated to be highly sensitive to fogwater pH, PM, and precursor gases NO2 and SO2. Such insights on major contributing factors imply that reduction of road dust and NOx emissions could lessen PM2.5 loadings in Chinese megacities during fog events. [ABSTRACT FROM AUTHOR]

• A numerical model is applied to constrain seawater sulfate levels. • Low seawater sulfate concentrations at the onset of Marinoan glaciation. • Weak oxidative weathering is responsible for sulfate deficient ocean. The microbial sulfate reduction plays a significant role in regulating marine organic matter degradation. Thus the variation of ancient marine sulfate levels is closely coupled with the changes in global organic carbon burials and Earth's surface redox evolution in geological time. It is widely assumed that seawater sulfate concentration was deficient during the anoxic Cryogenian Marinoan glaciation (ca.650–635 Ma) which represents the most extreme icehouse condition in Earth's history. However, such a low seawater sulfate level has not been explicitly confirmed. To address this, here we carried out pyrite content and sulfur isotope (δ34S py) analysis of the Cryogenian non-glacial (the Datangpo Formation) and the Marinoan glacial successions (the Nantuo Formation) in South China. The Datangpo and Nantuo Formation show relatively high values of δ34S py , ranging from +19.9 ‰ to +32.9 ‰, and low values of pyrite content (mean = 0.72 wt%). These pyrites are dominated by euhedral crystals with a rare occurrence of framboids, indicating an early diagenetic origin, i.e., pyrite formed in sediments with sulfate supplied from seawater. Using and a one-dimensional diffusion–advection-reaction (DAR) model, we calculate marine sulfate levels. The modeling results show that the seawater sulfate concentration is <1 mM during the transition from the top Datangpo to the basal Nantuo Formation, suggesting a shrink of the marine sulfate reservoir at the onset of Marinoan glaciation. We propose that the low marine sulfate concentration was resulted from a decrease in continental chemical weathering. This study provides a quantitative constraint on marine sulfate levels during the Cryogenian snowball Earth event, and it may shed new light on our understanding of the marine biogeochemical changes in the Neoproterozoic. [ABSTRACT FROM AUTHOR]

A durability investigation has been conducted on the actual tunnels locating at Kunming Section of Chengkun railway line. Appearance of concrete deterioration was recorded by a Nikon camera. In some representative locations, concrete cores were taken from Shot-concrete or bulk concrete with a hand-held coring rig. The eroded residuals and water around the coring site were collected for further investigations in laboratory. XRD and EPMA analyses were conducted to identify the facts of destructive course. Site investigation shows the lining concrete is subjected to a serious deterioration including salt crystallisation, leaking, surface powdered and flaked, etc. Further investigations in laboratory corroborate the major deterioration, i.e. carbonisation, the chemical erosion and physical attack by sulphate ions, etc. Elements distributions declare that carbonisation has notable evolvement of concrete properties and leads to the movements of sulphur and sodium elements. The sulphur migrates from neutralised area to alkaline area while the sodium moves along the opposite direction. EPMA analysis identifies that the aggressive sulphur ions are sourced from the external environment. [ABSTRACT FROM AUTHOR]

Marine sediments are the main sink for seawater sulfate and bacterial sulfate reduction is a major component of the global sulfur cycle. Nevertheless, the factors controlling sulfate reduction in the coastal estuary sediments that undergo spatial and temporal variations are still not fully understood. In this study, we measured the concentrations of SO 4 2− , Cl − , CH 4 , and DIC, and the δ 13 C of DIC in the pore water of five sampling stations surrounding the Qi'ao Island, Pearl River Estuary, Southern China during the dry season in November 2011 and during the wet season in May 2012. The results showed that the dilution-mixing of the Pearl River with low-concentration sulfate significantly affects the downcore profiles of the sulfate concentrations in the pore water of these estuary sediments. During the wet season, the dilution-mixing of the layers from the top of the sediments to a depth of 14–18 cm occurred at the different sampling stations. In this layer, the sulfate reduction is not appreciable based on the plot of the pore water Cl − and SO 4 2− . Below the dilution-mixing layers, however, sulfate reduction that is driven by the anaerobic oxidation of methane (AOM) occurs. In our comparison, it appeared that the AOM played more important role in the consumption of the pore water sulfate in May 2012 than in November 2011. Meanwhile, we observed a relatively good correlation ( r 2 =0.64) between the depth of the sulfate–methane interface (SMI) and the sulfate concentration in the pore water of the top sediments in dry season, indicating that the pore water sulfate concentration appears to be a primary controlling factor for the depth of the SMI in this estuary. These results highlight the need for an integrated analysis of the hydrologically driven the variations in the sulfate profiles to improve our understanding of the biogeochemical cycling of C, Fe and S and their budgets in estuarine environments. [ABSTRACT FROM AUTHOR]

Summary Seasonal hydrochemical monitoring has been conducted at a well-known arsenic (As) contaminated site to understand the critical controlling processes on As mobilization and enrichment in groundwater. The hydrochemical results indicate that the water chemistry at the studied site is mainly controlled by evaporates dissolution, and redox reactions during irrigation and non-irrigation periods, respectively. The measured redox-sensitive components indicate that the groundwater experienced periodic redox changes from irrigation to non-irrigation periods and that an enhanced reducing environment prevailed during the non-irrigation period. The observed high As concentration and the strong positive correlation between As and Fe support the conclusion that the Fe oxides/hydroxides reduction and Fe sulfide oxidation releases As during the irrigation period. However, the relatively low As concentration and the close inverse correlation between As, Fe and SO 4 2− show that Fe(III) and SO 4 2− reduction accompanied by the formation of Fe sulfide precipitates, retains As during the non-irrigation periods. The geochemical inverse modeling performed for the selected wells confirms that Fe oxide/hydroxide and Fe sulfide dissolution as well as siderite precipitation are the dominant processes related to the mobilization of As during the water evolution from the pre-irrigation to irrigation period, while Fe sulfide precipitation immobilize As during the groundwater evolution from the irrigation to the post-irrigation period. In general, the combined results of the hydrochemical monitoring and the geochemical inverse modeling support the conclusion that the Fe(III)–SO 4 2− redox cycling induced by periodic irrigation practices controls the mobilization of As in groundwater at this site. [ABSTRACT FROM AUTHOR]

Highlights: [•] We observed strong variability of ocean chemistry in early Cambrian South China. [•] We proposed a redox-stratified ocean model for explaining the variability. [•] Lines of evidence support sulfate spatiotemporally controlled mid-depth euxinia. [•] Our findings highlight low sulfate and high heterogeneity in early Cambrian oceans. [ABSTRACT FROM AUTHOR]

Over the vast Northwest China, arid desert contains high concentrations of sulfate, chloride, and other chemicals in the ground water, which poses serious challenges to infrastructure construction that routinely utilizes portland cement concrete. Rapid industrialization in the region has been generating huge amounts of mineral admixtures, such as fly ash and slags from energy and metallurgical industries. These industrial by-products would turn into waste materials if not utilized in time. The present study evaluated the suitability of utilizing local mineral admixtures in significant quantities for producing quality concrete mixtures that can withstand the harsh chemical environment without compromising the essential mechanical properties. Comprehensive chemical, mechanical, and durability tests were conducted in the laboratory to characterize the properties of the local cementitious mineral admixtures, cement mortar and portland cement concrete mixtures containing these admixtures. The results from this study indicated that the sulfate resistance of concrete was effectively improved by adding local class F fly ash and slag, or by applying sulfate resistance cement to the mixtures. It is noteworthy that concrete containing local mineral admixtures exhibited much lower permeability (in terms of chloride ion penetration) than ordinary portland cement concrete while retaining the same mechanical properties; whereas concrete mixtures made with sulfate resistance cement had significantly reduced strength and much increased chloride penetration comparing to the other mixtures. Hence, the use of local mineral admixtures in Northwest China in concrete mixtures would be beneficial to the performance of concrete, as well as to the protection of environment. [ABSTRACT FROM AUTHOR]

The authors analyze the sensitivities of source regions in East Asia to PM2.5(particulate matter with an aerodynamic diameter of ≤2.5 µm) concentration at Fukue Island located in the western part of Japan by using a regional chemical transport model with emission sensitivity simulations for the year 2010. The temporal variations in PM2.5concentration are generally reproduced, but the absolute concentration is underestimated by the model. Chemical composition of PM2.5in the model is compared with filter sampling data in spring; simulated sulfate, ammonium, and elemental carbon are consistent with observations, but mass concentration of particulate organic matters is underestimated. The relative contribution from each source region shows the seasonal variation, especially in summer. The contribution from central north China (105°E–124°E, 34°N–42°N) accounts for 50–60% of PM2.5at Fukue Island except in summer; it significantly decreases in summer (18%). Central south China (105°E–123°E, 26°N–34°N) has the relative contribution of 15–30%. The contribution from the Korean Peninsula is estimated at about 10% except in summer. The domestic contribution accounts for about 7% in spring and autumn and increases to 19% in summer. We also estimate the relative contribution to daily average concentration in high PM2.5days (>35 μg m−3). Central north China has a significant contribution of 60–70% except in summer. The relative contribution from central south China is estimated at 46% in summer and about 30% in the other seasons. The contributions from central north and south China on high PM2.5days are generally larger than those of their seasonal mean contributions. The domestic contribution is smaller than the seasonal mean value in every season; it is less than 10% even in summer. These model results suggest that foreign anthropogenic sources have a substantial impact on attainment of the atmospheric environmental standard of Japan at Fukue Island.Implications: The contribution from several source regions in East Asia to PM2.5 concentration at Fukue Island, a remote island located in the western part of Japan and close to the Asian continent, is estimated using a three-dimensional chemical transport model. The model results suggest that PM2.5 that is attributed to foreign anthropogenic sources have a larger contribution than that of domestic pollution and have a substantial impact on attainment of the atmospheric environmental standard of Japan at Fukue Island. [ABSTRACT FROM AUTHOR]

Abstract: Thermochemical sulfate reduction is considered to result in H2S >10% and high dryness coefficient values in the Lower Triassic and Upper Permian carbonate reservoirs in the NE Sichuan Basin. The gases produced from gas–water transition and water intervals were measured to have H2S higher than 30%, and are calculated to have significantly higher H2S and CO2 contents than a gas produced from a gas interval, and thus are not used to reflect TSR extents. Methane and ethane were shown to shift positively in carbon isotopes as a result of TSR. However, the fractionation has not quantitatively described. A logarithmic relationship is found to give the best fit for methane δ13C1 and [1 − H2S/(∑C1–6+H2S)] for all the gases with an equation of δ13C1, t = −16.6lnx − 33.0, indicating a closed system Rayleigh distillation with a kinetic fractionation factor αC of 1.0166. Ethane shows similar δ13C2 shift to methane (6.1‰ vs 5.5‰) for H2S/[H2S + ∑C1–6] = 0.2 in the NE Sichuan Basin. The δ13C2 deviation is significantly less than that of Mobile Bay Jurassic Norphlet Fm TSR-altered ethane (+16‰) for H2S/[H2S + ∑C1–6] = 0.1 (Mankiewicz et al., 2009). The ethane in association with high H2S (>10%) in NE Sichuan Basin shows slightly lighter δ13C values than those of the potential source rocks. Thus, it is possible for small amounts of gas derived from cracking of the source rocks to have mixed with TSR-altered gas in the high H2S pools. [Copyright &y& Elsevier]

To investigate the long-term trends and variations of the levels, compositions, size distribution and sources of particulate matter (PM), long-term monitoring campaigns of PM10 and PM2.5 were performed in a megacity in China (Chengdu) during the period from 2009 to 2011. The average concentration of PM10 was 172.01±89.80μg/m3 and that of PM2.5 was 103.15±59.83μg/m3, with an average PM2.5/PM10 of 0.60. Enrichments of the important species indicated that the fractions of crustal elements were higher in PM10 than those in PM2.5, while the abundance of organic carbon (OC) and secondary ions was enriched in the fine PM. Quantitative source apportionments of both PM10 and PM2.5 were performed by PMF. PM10 and PM2.5 in Chengdu were influenced by similar source categories, and their percentage contributions were in the same order: crustal dust was the highest contributor, followed by vehicular exhaust, secondary sulfate, secondary nitrate and cement dust. Crustal dust and cement dust contributed a higher percentage to PM10 than to PM2.5, while vehicular exhaust and secondary particles provided higher percentage contributions to PM2.5. In addition, PMF–HCA was performed to investigate the characteristics of the sources of the clustered samples, identifying three periods: crustal dust dominant-period, secondary sulfate dominant-period and comprehensive source influenced-period. Planting, reduction of precursors, and banning high-emission vehicles should be implemented to control crustal dust, secondary particles and vehicular exhaust in Chengdu. Furthermore, the size-resolved and the period-resolved control would be more effective. [ABSTRACT FROM AUTHOR]

Highlights: [•] A significant correlation is between δ34SSO4 and δ18OSO4 of the Heihe River. [•] δ34SSO4 and δ18OSO4 values of the Heihe River increase downstream. [•] Sulfate sources of the Heihe River are affected by mixing of groundwater. [•] Hydrological processes control on sulfate sources and S cycling in the basin. [ABSTRACT FROM AUTHOR]

Understanding the changes in the sulfate (SO 4 2−) formation pathway is important to further control particle pollution owing to the significant reduction of SO 2 emission and enhanced atmospheric oxidation. This study applied the Community Multiscale Air Quality (CMAQ) model coupled with the sulfur tracking model (STM) to quantify sources of atmospheric SO 4 2− in China and their changes during 2008–2016. The results showed that the surface SO 4 2− concentration decreased by 51.1%, 40.8%, 37.5%, and 36.2% for Beijing–Tianjin–Hebei (BTH), Yangtze River Delta (YRD), Pearl River Delta (PRD), and Sichuan Basin (SCB), respectively. In addition, the SO 4 2− formation pathways also changed in a sustained manner. The gas-phase reaction of SO 2 with OH (SO 4 _GAS) and the reaction catalyzed by Fe3+ and Mn2+ (SO 4 _FEMN) decreased significantly (63.4% and 61.7%), whereas the aqueous-phase reaction of SO 2 with O 3 (SO 4 _O 3) increased by 39.9% from 2008 to 2016. Primary SO 4 2− emission (SO 4 _EMIS) played an important role in autumn and winter with over 30% contribution, whereas SO 4 _GAS and the aqueous-phase reaction of SO 2 with H 2 O 2 (SO 4 _H 2 O 2) dominated in spring and summer, respectively. The sensitivity simulation results showed that sharp SO 2 reduction significantly decreased SO 4 _GAS (over 60%); however, it was less sensitive to SO 4 _O 3 (8%–11%). In addition, the SO 2 emission reduction resulted in a large increase in atmospheric NH 3 concentrations due to less neutralization reaction, thus increasing NO 3 − concentration in some regions. These results suggest that multi-pollutants control for SO 2 -NOx-VOC should be implemented to prevent the enhanced atmospheric oxidation furtherly deteriorating secondary air pollution, particularly in spring and summer. In addition, limiting primary emissions from residential combustion in winter is important to achieve coordinated control of SO 2 and SO 4 2− in northern China. [Display omitted] • SO 4 2− formation characteristics have changed sustainably during 2008–2016 in China. • SO 2 reduction aggressively decreased the SO 4 2− level from the gas-phase formation. • Targeted control should be executed for further mitigating SO 4 2− in specific regions. [ABSTRACT FROM AUTHOR]

It is hard to distinguish pyrites generated by microbial sulfate reduction (MSR) from thermochemical sulfate reduction (TSR). The upper Ediacaran Dengying Formation (ca 551–541 Ma) of Sichuan basin is chosen to study for this purpose by means of petrological, bulk and micrometer-scale analyses on barite, pyrite, calcite, and dolomite for carbon and sulfur isotope and rare earth elements and yttrium (REY) compositions. We find that MSR-derived pyrites precipitated from near-surface to shallow burial settings are characterized by seawater-like REY patterns and superchondritic Y/Ho ratios (74.3 ± 9.5), and have δ34S pyrite values in a wide range from −36.8‰ to 34.8‰, positively correlated with arsenic contents, likely through cryptic sulfur cycles driven by arsenic. In contrast, TSR-derived pyrites generated during deep burial settings have REY characterized by non-seawater-like patterns and chondritic Y/Ho ratios (33.6 ± 5.1), and show small sulfur isotopic fractionations (~10.5‰). TSR-pyrites yield both U-shaped and bell-shaped δ34S transects compared with U-shaped distributions of MSR-pyrites. The calcites associated with the TSR-pyrites show LREE enrichment, elevated Y/Ho ratios (85.8 ± 14.2) and negative δ13C values, likely resulting from decomposition of organic matter. This study highlights a combination method from REY patterns, δ13C and δ34S values from analyses on micro-sized pyrite and the associated calcites can be used to effectively distinguish MSR from TSR. [Display omitted] • MSR-pyrites have different petrology, REY and δ34S patterns from TSR-pyrites. • Cryptic sulfur cycles are likely driven by redox-sensitive metals such as arsenic. • TSR-calcites show LREE enrichment, elevated Y/Ho ratios and negative δ13C values. [ABSTRACT FROM AUTHOR]

• New carbonate associated sulfate (CAS) δ 34 S data across the end-Permian extinction. • CAS δ 34 S at South China localities varies by up to 20‰ within single hand samples. • Disagreement with evaporite δ 34 S suggests a diagenetic origin for CAS δ 34 S scatter. • Models & context indicate that sediment redox changes can explain CAS δ 34 S scatter. • New framework for interpreting CAS δ 34 S records is presented. The dynamics of the marine sulfur cycle across the End-Permian Mass Extinction (EPME) have been obscured by disagreement between sulfur isotopic records from different archives. Here, we attempt to resolve this disagreement with new measurements of carbonate associated sulfate (CAS) δ 34 S (i.e., δ 34 S CAS) from three Permian-Triassic boundary (PTB) sections in South China. We observe substantial δ 34 S CAS variation within single hand samples, with most samples having a δ 34 S CAS range exceeding 5‰ and some reaching ∼20‰. We also find evidence for mixing between low CAS abundance, high δ 34 S CAS and high CAS abundance, low δ 34 S CAS phases. A simple model of reduced sulfur oxidation and incorporation as CAS suggests that sedimentary redox oscillations may plausibly explain the δ 34 S CAS heterogeneity within many EPME carbonates; rapid variation in the δ 34 S of the marine SO 4 2 − reservoir is not necessary. Additional work to examine how synchronous changes in organic carbon fluxes, sedimentation rates, or other parameters that impact sediment redox and sulfur diagenesis is needed to evaluate the environmental implications of the δ 34 S CAS heterogeneity. [ABSTRACT FROM AUTHOR]

In recent decades, surface water and groundwater in the Jinan spring catchment have become increasingly contaminated by sulfate due to the expansion of urbanization and the increasing intensity of anthropogenic activities. In this study, ten surface water samples and forty-three groundwater samples were collected in the catchment from June to September 2019, and their hydrochemistry and stable isotopes (δ34S SO4 , δ18O SO4 , δD H2O and δ18O H2O) combined with a Bayesian isotope mixing model were used to identify sources and transformations and to quantitatively evaluate the contribution of sulfate from multiple potential sources of pollution. The dual isotopes of sulfate and the isotope mixing model showed that sulfate in the surface water was mainly derived from evaporite dissolution (32.6%), sewage (18.8%), soil sulfate (15.4%) and sulfide oxidation (10.2%), while that in the groundwater was mainly derived from soil sulfate (32.4%) and sewage (30.6%). In groundwater, the proportions of sewage and evaporite dissolution increased from the indirect recharge area to the discharge area, while the contribution of soil sulfate and sulfide oxidation decreased. In regard to surface waters, the contribution proportion of evaporite dissolution to SO 4 2− in June was 40.9%, which was significantly higher than 24.2% in September, but the proportion of sewage, soil sulfate and sulfide oxidation was lower in June (13.7, 12.9 and 9.5%, respectively) than in September (23.8, 17.8 and 10.8%, respectively). There was no significant correlation between the ratio of SO 4 2−/Cl− and δ34S SO4 and δ18O SO4 in surface water and groundwater, indicating that bacterial sulfate reduction did not play a major role. This study can provide a reference for the development of effective pollution management strategies for water resources in karst areas of northern China. • The accuracy of sulfate tracing can be improved by combining multiple isotopes with land use and water chemistry. • A Bayesian isotope mixing model (Simmr) was employed to quantity SO 4 2− source. • Major sulfate sources of surface water were evaporite dissolution, sewage, soil-derived sulfate and sulfide oxidation; while for groundwater were soil sulfate and sewage. • Sulfate pollution in karst groundwater and surface water might be the coupling result of natural input and anthropogenic activities. [ABSTRACT FROM AUTHOR]

Carbonate associated sulfate (CAS) is widely used to reconstruct the deep time seawater sulfate sulfur isotopic composition (δ34S sw) and marine sulfur cycle. However, δ34S CAS normally shows substantial stratigraphic and spatial variations, casting doubt on its validity in recording δ34S sw. To understand the origin of δ34S CAS oscillation, we measured sulfur isotopic compositions of CAS (δ34S CAS) extracted from ribbon rock samples collected from the middle Cambrian Xuzhuang and Zhangxia formations in North China. The limestone layers have consistently higher δ34S CAS values but lower CAS contents than the marlstone layers. Sulfate oxygen isotope data (δ18O CAS , Δ17O CAS) suggest that such isotopic differences can neither be explained by contamination of secondary atmospheric sulfate (SAS) nor oxidation of pyrite. Instead, the different trends of modification on δ34S CAS values in marlstone and limestone layers may reflect two predominant processes. Low δ34S CAS of the marlstone might mainly result from the influence of benthic H 2 S flux. Oxidation of H 2 S in the seafloor would generate 34S-depleted sulfate that is subsequently taken in carbonate precipitated in the seafloor. In contrast, the limestone might have precipitated in more oxic seafloor and was mainly sourced from seawater, with less influence of benthic flux. The diagenetic dissolution and reprecipitation of limestone within MSR zone accounts for the higher δ34S CAS and lower CAS contents. Finally, our study suggests that δ34S CAS record δ34S sw only when the influence of both benthic flux and early diagenesis was insignificant. [ABSTRACT FROM AUTHOR]

Abstract: Clouds play an important role in the oxidation of sulfur dioxide to sulfate, since aqueous phase sulfur dioxide oxidation is typically much faster than oxidation in the gas phase. Important aqueous phase oxidants include hydrogen peroxide, ozone and oxygen (catalyzed by trace metals). Because quantities of emitted sulfur dioxide in China are so large, however, it is possible that they exceed the capacity of regional clouds for sulfate production, leading to enhanced long-range transport of emitted SO2 and its oxidation product, sulfate. In order to assess the ability of regional clouds to support aqueous sulfur oxidation, four field campaigns were conducted in 2007 and 2008 at Mt. Tai in eastern China. Single and 2-stage Caltech Active Strand Cloudwater Collectors were used to collect bulk and drop size-resolved cloudwater samples, respectively. Key species that determine aqueous phase sulfur oxidation were analyzed, including cloudwater pH, S(IV), H2O2, Fe, and Mn. Gas phase SO2, O3, and H2O2 were also measured continuously during the campaigns. A wide range of cloud pH values was observed, from 2.6 to 7.6; 60% of cloud samples had a pH between 3 and 5. H2O2 was found to be an important sulfur oxidant, especially at cloudwater pH lower than 5. H2O2 was the most important oxidant in 68% of the cloud sampling periods. High concentrations of residual H2O2 were observed in many periods, especially in summer, implying a substantial capacity for additional sulfur oxidation. O3 was an important oxidant when cloudwater pH was higher than approximately 5–5.3, and was the most important oxidant in 20% of the studied periods. Aqueous sulfur oxidation by O2 (catalyzed by Fe and Mn) was found to be the fastest sulfate production pathway in 12% of the cases. Observed chemical heterogeneity among cloud drop populations was found to enhance rates of S(IV) oxidation by ozone and enhance or slow metal-catalyzed S(IV) autooxidation rates in some periods. These effects were found to be only of minor importance for the total S(IV) oxidation rate, however, as H2O2 was the dominant S(IV) oxidant during most periods. [Copyright &y& Elsevier]

Abstract: Nitrate and sulfate account for a significant fraction of PM2.5 mass and are generally secondary in nature. Contributions to these two inorganic aerosol components from major sources need to be identified for policy makers to develop cost effective regional emission control strategies. In this work, a source-oriented version of the Community Multiscale Air Quality (CMAQ) model that directly tracks the contributions from multiple emission sources to secondary PM2.5 is developed to determine the regional contributions of power, industry, transportation and residential sectors as well as biogenic sources to nitrate and sulfate concentrations in China in January and August 2009. The source-oriented CMAQ model is capable of reproducing most of the available PM10 and PM2.5 mass, and PM2.5 nitrate and sulfate observations. Model prediction suggests that monthly average PM2.5 inorganic components (nitrate + sulfate + ammonium ion) can be as high as 60 μg m−3 in January and 45 μg m−3 in August, accounting for 20–40% and 50–60% of total PM2.5 mass. The model simulations also indicate significant spatial and temporal variation of the nitrate and sulfate concentrations as well as source contributions in the country. In January, nitrate is high over Central and East China with a maximum of 30 μg m−3 in the Sichuan Basin. In August, nitrate is lower and the maximum concentration of 16 μg m−3 occurs in North China. In January, highest sulfate occurs in the Sichuan Basin with a maximum concentration of 18 μg m−3 while in August high sulfate concentration occurs in North and East China with a similar maximum concentration. Power sector is the dominating source of nitrate and sulfate in both January and August. Transportation sector is an important source of nitrate (20–30%) in both months. Industry sector contributes to both nitrate and sulfate concentrations by approximately 20–30%. Residential sector contributes to approximately 10–20% of nitrate and sulfate in January but its contribution is low in August. [Copyright &y& Elsevier]