Sulfur Deposition Research Articles

Spatiotemporal variations of wet and dry Sulfur deposition in Yangtze River Delta, China

Spatiotemporal variations of wet and dry Sulfur deposition in Yangtze River Delta, China

Agricultural Sci-Tech Innovation Assistance for Food Security and Sustainability to Taal Volcano’s Internally Displaced Population in Batangas

On 12 January 2020, the Department of Science and Technology’s Philippine Institute of Volcanology and Seismology (PHIVOLCS) raised Alert Level from 1 to 4 (out of 5) after increasing activity of Taal Volcano in Batangas. The eruption has resulted in development challenges and problems such as increased poverty, limited livelihood opportunities faced by farmers which manifest the serious impact of the eruption on the ways of living and the livelihood activities. Thus, this project formulated in which a series of workshop and training skills where conducted to assess, develop and implement an action plan for rehabilitating the farm of the affected residents of Batangas, primarily at the municipality of Talisay, Balete, San Nicolas, Laurel, Agoncillo, and Ibaan. The participants were chosen by the Local Government Unit and composed mostly of members of 4P’s and farmers. The beneficiaries were already in a difficult situation not only because of the recent eruption of Taal Volcano that rendered some of them homeless and unemployed but also because of the COVID-19 which aggravated the situation. Based on the initial assessment, it was found out that agricultural livelihood and property were heavily damaged by the eruption. Moreover, the said assessment led the project team to identify initial livelihood training’s that can be introduced to the affected communities. These trainings’ included household opportunities through vegetable production, processing and organic concoction production to rehabilitate the soil from acidity due to sulfur deposition during volcanic eruption. Rehabilitation and recovery plan were also considered to capacitate the farmers.

Molecular Polymorphism of tau aggregates in Pick's disease.

Tau protein plays a central role in many neuropathies. The trajectory by which tau spreads through neural networks is disease-specific but the events driving progression are unknown. This is due in part to the challenge of characterizing tau aggregates in situ. We address that challenge using in situ micro-x-ray diffraction (µXRD) and micro-X-ray fluorescence (μXRF) to examine tau lesions in the brain of a 79-year-old male with dementia. Neuropathological examination revealed classical forms of tau in the hippocampal formation: extensive Pick bodies in the granular layer; modest numbers of neurofibrillary tangles and dystrophic neurites in the CA4 and hilus. µXRD indicated that Pick bodies are low in fibril content, whereas neurofibrillary lesions within adjacent tissue exhibit far greater density of fibrillar tau. μXRF demonstrated elevated levels of zinc, calcium and phosphorous in all tau-containing lesions whereas sulfur deposition was greatest in lesions exhibiting high fibrillar content. Correlation of lesion morphology with anatomical localization, tau fibrillation and differential elemental accumulation suggests tau fibrils generate biochemically distinct microenvironments that influence lesion morphology, tau seed formation and spreading.

Atmospheric Sulfur and Nitrogen Deposition in Five Nature Reserves of Sichuan Basin to Qinghai-Tibetan Plateau Transect Region, Southwestern China

Atmospheric Sulfur and Nitrogen Deposition in Five Nature Reserves of Sichuan Basin to Qinghai-Tibetan Plateau Transect Region, Southwestern China

From Structure to Strength: Analyzing the Impact of Sulfuric Acid on Pig Bone Demineralization Through FTIR, LIBS, and AAS.

The present research aimed to investigate the demineralizing effects of sulfuric acid on pig bone. Alterations in collagen and phosphate contents and changes in the elemental composition of the bone during the 14-day-long immersion in sulfuric acid solutions of different concentrations were estimated using ATR-FTIR, LIBS, and AAS. FTIR spectra at amide I (1800-1600 cm-1) and phosphate ν1/ν3 (PO43-) (1300-900 cm-1) domains were scrutinized using the deconvolution method for monitoring changes in the protein secondary structure and mineral content. The results implicated sulfuric acid as a powerful demineralization agent and effective in targeting mineral components, such as hydroxyapatite, while leaving the collagen matrix relatively preserved with a complex secondary structure. Collagen maturity marker values gave valuable insights into the structural integrity of the bone. LIBS and AAS indicated changes in bone hardness; phosphorous-to-carbon ratio; and calcium, phosphorous, and magnesium content in the solutions left after the immersion period. The changes in the ratio of ionic-to-atomic calcium lines in the LIBS spectra indicated hardening of the bone, with increasing acid concentration and prolonged action, due to the deposition of calcium sulfate on the surface. The calcium concentration in the solutions decreased with increased acid concentration, while the change in phosphorus and magnesium concentrations was reversed.

Regional variation in growth and survival responses to atmospheric nitrogen and sulfur deposition for 140 tree species across the United States

Atmospheric deposition of nitrogen (N) and sulfur (S) alter tree demographic processes via changes in nutrient pools, soil acidification, and biotic interactions. Previous work established tree growth and survival response to atmospheric N and S deposition in the conterminous United States (CONUS) data by species; however, it was not possible to evaluate regional variation in response using that approach. In this study, we develop species- and region-specific relationships for growth and survival responses to N and S deposition for roughly 140 species within spatially demarcated regions of the U.S. We calculated responses to N and S deposition separately for 11 United States Forest Service (USFS) Divisions resulting in a total of 241 and 268 species × Division combinations for growth and survival, respectively. We then assigned these relationships into broad categories of vulnerability and used ordinal logistic regressions to explore the covariates associated with vulnerability in growth and survival to N and S deposition. As with earlier studies, we found growth and survival responses to air pollution differed by species; but new to this study, we found 45%−70% of species responses also varied spatially across regions. The regional variation in species responses was not simply related to atmospheric N and S deposition, but was also associated with regional effects from precipitation, soil pH, mycorrhizal association, and deciduousness. A large amount of the variance remained unexplained (total variation explained ranged from 6.8%−13.8%), suggesting that these or additional factors may operate at finer spatial scales. Taken together, our results demonstrate that regional variation in tree species' response has significant implications for setting critical load targets, as critical loads can now be tailored for specific species at management-relevant scales.

Passivation of Cadmium and Arsenic in Acidified Paddy Soil by Calcium Fertilizer with Biochar-ferromanganese Composites

Due to the aggravation of atmospheric nitrogen and sulfur deposition and the unreasonable application of fertilizer, soil acidification is becoming increasingly serious. In heavy metal-contaminated soils, acidification not only seriously affects fertility but also the effectiveness and sustainability of conventional passivation remediation materials such as biochar. The application of calcium fertilizer may improve soil acidification, alleviate the aging of biochar materials in soil, and improve its remediation ability to composite polluted soil. However, the mechanism of its effect is still unclear. Based on this, this study selected iron-manganese oxide （FM） and hickory cattails biochar （BC） to prepare biochar-ferromanganese composites （BFM） and conducted simulated acidification on it. Through characterization and an aqueous adsorption test, the changes in physicochemical properties and adsorption properties of the material after acidification were explored. Then, orthogonal tests were carried out to explore the effects of the combination of BFM and calcium fertilizer on soil pH and the availability of Cd and As under acidification conditions and to obtain the best combination scheme. The results showed that the optimal ratio of BC and FM in BFM was 7∶3 （quality ratio）, the removal rates of Cd（Ⅱ） and As（Ⅲ） were as high as 94.58% and 97.14%, respectively, and the adsorption capacities were 120.74 mg·g-1 and 129.29 mg·g-1 （solid-liquid ratio 1∶500）. After acidification treatment, the pore structure of BFM surface decreased, and the types and quantities of functional groups changed, resulting in the removal rates of Cd（Ⅱ） and As（Ⅲ） in aqueous solution decreasing by 73.97%-92.84% and 73.56%-93.61%, respectively. The combined application of calcium fertilizer and BFM could significantly increase soil pH, with an increase range of 3.06%-37.84%. The effect of increasing pH decreased with the increase in culture time and acidification degree. Compared with that in the blank control, the content of available Cd in soil was significantly reduced by 22.67%-97.78%. The content of available As in soil was generally stable. According to the effect curve analysis of the orthogonal test results, under the condition of weak acidification degree （pH=5.6）, the application of 2% supplemental amount with 2% silica-calcium fertilizer and 2% calcium-magnesium phosphate fertilizer had a good passivation effect on soil Cd. Under the condition of strong acidification degree （pH=4.0）, the application of 2% supplemental amount and 2% silica-calcium fertilizer had a good passivation effect on soil As. In summary, simulated acidification will affect the adsorption performance of BFM, and calcium fertilizer combined with it can increase soil pH, improve soil acidification, alleviate the aging of BFM in acidified soil, and improve its repair ability to heavy metal-polluted soil.

Ore sulfur of Golovnin Volcano, Kunashir Island

Research subject. Hydrothermal deposits of Golovnin Caldera. Aim. To study the epithermal volcanogenic ore formation. Key points. Until now, there has been a consensus on the exogenous sedimentary (colloidal) genesis of sulfur in volcanic lakes. Our observations and microstructure studies indicate the presence of sulfur melt at the bottom of Kipyaschee Lake. Drops of this melt are carried to the surface of the lake as part of a light gray foam. The significant differences of sulfur spherules in the concentration of sulfide mineralization, in its composition, as well as in the presence or absence of numerous opal inclusions are most simply explained by the capture of droplets in various parts of the sulfur melt and their subsequent movement by a gas stream passing through the melt. Elemental sulfur condensate is formed in bottom sediments as a result of forced cooling of endogenous gas flows by lake water. The main condensation of sulfur occurs here (96% or more of the total potential of fluid sulfur). Residual condensation of sulfur occurs in the aquatic environment. Finely dispersed sulfur condensate in a mixture with water is unstable and breaks down over time with the release of hydrogen sulfide and the formation of sulfurous and sulfuric acids. The activity of bottom hydrotherms and coastal unrest prevents the formation of colloidal sulfur sediment at the bottom of lakes. In the crater depressions at the bottom of the lakes of the Golovnin Caldera, sulfidization of its melt occurs simultaneously with the condensation of sulfur itself. Gravitational deposition of sulfides in the sulfur melt leads to their enrichment of the root parts of crater depressions, where pyrite ore bodies are formed in real time. Terrestrial sulfur deposits, together with the modified rocks overlying them, demonstrate the full profile of endogenous apical oxidation under gas-hydrothermal action: sulfur and sulfur-opal rocks up the section are replaced by gypsum-jarosite rocks and, further, by an “iron hat” of limonite-cemented breccias of the dome mantle. Conclusions. Observations, microstructure studies and molecular chemical modeling indicate the endogenous condensate origin of ore sulfur in the Golovnin Caldera and exclude its exogenous sedimentary genesis.

Structure dependence of the enhanced sulfur tolerance of core–shell CoMn oxides for benzene oxidation: Discrepant sulfur species and less affected reactant activation

Effective reduction of VOCs emissions in practical gas requires low-temperature catalysts with remarkable SO2 tolerance. Here via simply mixing CoCO3 into the precursors of α-MnO2, a core–shell CoMn composite was developed. The leading one with CoCO3 addition of 3 g (Co3Mn) achieved 100 % C6H6-to-CO2 conversion at ≥250 °C under 120 L/g/h, and still the CO2 yield over the sulfurized Co3Mn (simulated by H2SO3 vapor pretreatment) was maintained 100 %. However, with respect to the case of fresh MnO2, the CO2 production at 250 and 300 °C over the sulfurized MnO2 was decreased by 26 % and 8 %, respectively, and in the meantime, a larger amount of CO was detected. The dominant formation of abundant MnSO4 species due to sulfur poisoning led to the deactivation of pure MnO2, while over Co3Mn the formation of MnSO4 was significantly inhibited because of (i) the electron transfer from Co2+ to Mn4+ restraining that from S4+ to Mn4+ and (ii) the stronger alkalinity of Co species making the acidic H2SO3 preferentially anchor on Co as CoSO4. Along with the sacrificial role, another way cobalt alleviated sulfate toxicity was through transiting the aggregated sulfate deposition into scattered state. Investigations conducted primarily with UV–vis DRS and temperature-programmed techniques further reveal that neither MnO2 nor Co3Mn could escape from the sulfur-induced adversity on activation of O2 and benzene, but the sulfurized Co3Mn was much less affected, thus sustaining the deep benzene oxidation. Finally, reaction routes were unraveled according to the phenol, benzoquinone, maleic acid and acetic acid intermediates.

Several Mechanisms Drive the Heterogeneity in Browning Across a Boreal Stream Network

AbstractOver the past few decades, many catchments in Northern hemisphere have experienced increases in dissolved organic carbon (DOC) concentrations, resulting in a brownish color of the water, known as aquatic browning. Several mechanisms have been proposed to explain browning, but consensus regarding the relative importance of recovery from acid deposition, climate change, and land management remains elusive. To advance our understanding of browning mechanisms, we explored DOC trends across 13 nested boreal catchments, leveraging concurrent hydrological, chemical, and terrestrial ecosystem data to quantify the contributions of different drivers on observed trends. We first identified the related environmental factors, then attributed the individual trends of DOC to potential drivers across space and time. Our results showed that all catchments exhibited increased DOC trends from 2003 to 2021, but the DOC response rates differed by five‐fold. No single mechanism could fully explain the browning; instead, sulfate deposition, climate‐related factors, and site properties jointly controlled the variation in DOC trends. Specifically, the long‐term increases in DOC were primarily driven by recovery from sulfate deposition, followed by increases in terrestrial productivity, temperature, and discharge. However, catchment area and landcover type also regulated the response rate of DOC to these drivers, creating spatial heterogeneity in browning among sub‐catchments despite similar deposition and climate forcing. Interestingly, browning has weakened in the last decade as sulfate deposition has fully recovered and other current drivers are insufficient to sustain the long‐term increases. Our results highlight that multifaceted, spatially structured, and nonstationary drivers must be accounted for to predict future DOC changes.

Redox ability dependent SO2 tolerance for low-temperature NH3-SCR of MnO2@MeOX (Me = Ti, Ce, Cu) catalysts

Elucidating the deposition behavior of sulfates on catalysts of low-temperature ammonia-assisted selective catalytic reduction (NH3-SCR) helps improve their SO2 tolerance and applicability. Therefore, this study aimed to explore the impact of the redox properties of low-temperature NH3-SCR catalysts on their catalytic activity and SO2 tolerance. Oxidizing Mn@Ce, neutral Mn@Ti, and reducing Mn@Cu catalysts were prepared, and their NH3-SCR activities and SO2 tolerances were evaluated. Subsequently, the characteristics of the catalyst poisoned by SO2 over time and the deposition behavior of sulfates on the catalyst were analyzed to determine the reaction pathway between SO2 and the NH3-SCR catalyst. The SO2 tolerance of the catalysts decreased in the following order: oxidizing Mn@Ce > neutral Mn@Ti > reducing Mn@Cu. Combined with the characteristic results, we found that the amount of shell-metal sulfate increased with SO2 poisoning time, indicating it was the dominant factor in catalyst deactivation. Specifically, the amount of shell-metal sulfate followed the order Mn@Cu-S12 (31.4 µmol) > Mn@Ti-S12 (24.9 µmol) > Mn@Ce-S12 (9.5 µmol). Additionally, the increasing SO42− ratio from Mn@Me-S4 to Mn@Me-S12 followed the order Mn@Cu (6.7%) > Mn@Ti (4.4%) > Mn@Ce (1.7%), implying that the reduction of Mn@Cu favors chemical SO2 poisoning pathway and facilitates the deposition of copper sulfate. In contrast, Mn@Ce with its strong oxidation properties, is beneficial for inhibiting the chemical poisoning pathway of SO2 and alleviating the deposition of cerium sulfate. Consequently, this study demonstrates that the redox ability of catalyst regulates the SO2 poisoning pathways, aiding the development of low-temperature NH3-SCR catalysts with high SO2 tolerance.

Modulating NH3 oxidation and inhibiting sulfate deposition to improve NH3-SCR denitration performance by controlling Mn/Nb ratio over MnaNbTi2Ox (a = 0.6-0.9) catalysts

The MnaNbTi2Ox (a = 0.6–0.9) catalysts for NH3 selective catalytic reduction denitration were prepared using the co-precipitation method. Among them, Mn0.7NbTi2Ox exhibits well low-temperature catalytic performance, wide activity temperature range (180–480 ℃), and worthy resistance to SO2 even with H2O. XRD was used to investigate the structure of MnaNbTi2Ox, in which Mn and Nb oxides highly dispersed in the MnaNbTi2Ox catalysts and Nb can dope into the crystal lattice of TiO2. XRF and XPS results show Nb can affect the transfer of electrons to Mn4+, and changing the Mn/Nb ratio can regulate the Mn4+ content on the MnaNbTi2Ox catalysts. H2-TPR, NH3 and NO oxidation results verify that Nb inhibits the oxidation capacity of MnaNbTi2Ox, and altering the Mn/Nb ratio can get appropriate oxidation property, which facilitates low-temperature NH3 activation and limit non-selective oxidation for NH3. In-situ DRIFTS results show Nb-OH bonds can provide new Brønsted acid sites, and both Lewis and Brønsted acid sites are active. Furthermore, Nb addition prevents sulphate deposition on the catalyst. The effect of Mn/Nb on catalytic performance, N2O formation and inhibition, SO2 poisoning, SO2 effect on NH3-SCR, and the enhancement of SO2 tolerance are also analyzed.

A Multifunctional Secondary Based on Heterogeneous Co-MnO@NC for Depth-Induced Deposition and Conversion of Polysulfides in Li─S Batteries.

The conductive carbon-based interlayer, as the secondary current collector in the self-dissolving battery system, can effectively capture escaping cathode active materials, inducing deep release of remaining capacity. In the multi-step reactions of Li─S batteries, the environmental tolerance of the conductive carbon-based interlayer to polysulfides determines the inhibition of shuttle effects. Here, a modified metal-organic framework (Mn-ZIF67) is utilized to obtain nitrogen-doped carbon-coated heterogeneous Co-MnO (Co-MnO@NC) with dual catalytic center for the functional interlayer materials. The synergistic coupling mechanism of NC and Co-MnO achieves rapid deposition and conversion of free polysulfide and fragmented active sulfur on the secondary current collector, reducing capacity loss in the cathode. The Li─S battery with Co-MnO@NC/PP separator maintains an initial capacity of 1050mAhg-1 (3C) and excellent cycle stability (0.056% capacity decay rate). Under extreme testing conditions (S load = 5.82mgcm-2, E/S=9.1µLmg-1), a reversible capacity of 501.36mAhg-1 is observed after 200 cycles at 0.2C, showing good further practical reliability. This work demonstrates the advancement application of Co-MnO@NC bimetallic heterojunctions catalysts in the secondary current collector for high-performance Li─S batteries, thereby providing guidance for the development of interlayer in various dissolution systems.

Legacy effect of 25 years reduced atmospheric sulphur deposition on spruce tree nutrition

AbstractBackgroundSince the mid‐1990s, sulphur (S) pollution was drastically reduced in Central Europe. Over time, this has led to a distinct reduction in S availability for Norway spruce (Picea abies Karst.), which is still the most important timber species in Central European forestries.AimsDetermination of the Norway spruce nutritional status of former strongly affected areas by S pollution (Saxony) with different degrees of liming by assessing their foliar element contents and comparing them to regions remote from historical high S deposition.MethodsSites were selected based on levels of S deposition in the 1970–1990s with historical high deposition in Saxony (NE Germany), low deposition at Schluchsee (SW Germany) and Davos (Switzerland) as a clean air reference. Needles were sampled in late autumn 2019/2020 and elemental contents determined. Additional historical data on foliar S contents were available.ResultsHistorical data showed a clear decrease in foliar S contents in the Saxonian sites over the last 25 years, independent of liming. No difference between all study sites was found in the most recent sampling, whereas S together with other macronutrients strongly indicates deficiencies for forest growth and health.ConclusionsAfter 25 years of reduced S deposition, S nutrition became low for Norway spruce trees in Saxony, whereas soil parent material determines the overall tree nutritional status with respect to other nutrients. As such, no difference between sites with historical high, low or no S deposition was found. Further studies should focus on the mineralization of organic S in the topsoil to understand if S is effectively recycled within the forest ecosystem and on the effect of other diminishing nutrients such as Mg and P.

Optimal liquid sulfur deposition dynamics for fast-charging Li-S batteries

It is urgent to develop fast-charging batteries to eliminate the charging concerns when using electric vehicles. The fluid nature of liquid sulfur was found to enhance areal capacities and contribute to lithium-sulfur (Li-S) fast-charging batteries. However, the deposition kinetics of liquid sulfur in Li-S batteries remain underexplored. This study uses a micro-battery device to track the in-situ deposition of liquid sulfur on carbon film. Surprisingly, slower reaction and sulfur growth kinetics were observed even under high overpotential and high-conductivity substrates, indicating that excessive sulfur droplet formation impedes both reaction and growth kinetics. This insight guided the tailoring of carbon nanofiber cathodes, resulting in 94 % capacity retention even with a significant increase in charging rate (from 1 C to 8 C). This research advances our understanding of liquid sulfur in Li-S batteries and provides guidance for designing high-performance, fast-charging cathodes.

Optimization of fracturing parameters for horizontal wells in high-sulfur gas reservoirs considering the effect of sulfur deposition

During the development of high-sulfur gas reservoirs, the precipitation and deposition of elemental sulfur can lead to a reduction in reservoir porosity and permeability. Previous studies focus on the well production with optimized operational parameters, but the effect of sulfur deposition is not included, which impacts fracturing parameters, well production, and economic evaluation. Therefore, this work proposes a reasonable approach for parameter optimization considering sulfur. The variation of porosity and permeability are first evaluated during sulfur deposition. After that, fracture half-length, fracture spacing, fracture conductivity, and fracture distribution are optimized with orthogonalization factor analysis, and the influence of sulfur deposition on different fracture parameters are detailed analyzed. The results shown that the fracture half-length and fracture conductivity are greatly affected by sulfur deposition. Finally, net profit value is applied to obtain the optimal fracture spacing interval. With economic evaluation, the optimal fracture spacing interval of 125 m∼ 150 m is determined considering the net profit and the payback period. This work provides a useful economic method for fracture parameter optimization high-sulfur gas reservoirs, which benefits for the development and production of gas reservoirs.

Phasing and climate forcing potential of the Millennium Eruption of Mt. Baekdu

The Millennium Eruption of Mt. Baekdu, one of the largest volcanic eruptions in the Common Era, initiated in late 946. It remains uncertain whether its two main compositional phases, rhyolite and trachyte, were expelled in a single eruption or in two. Investigations based on proximal and medial ash have not resolved this question, prompting us to turn to high-resolution ice-core evidence. Here, we report a suite of glaciochemical and tephra analyses of a Greenlandic ice core, identifying the transition from rhyolitic to trachytic tephra with corresponding spikes in insoluble particle fallout. By modeling annual snow accumulation, we estimate an interval of one to two months between these spikes, which approximates the hiatus between two eruptive phases. Additionally, negligible sulfur mass-independent fractionation, near-synchroneity between particle and sulfate deposition, and peak sulfur fallout in winter all indicate an ephemeral aerosol veil. These factors limited the climate forcing potential of the Millennium Eruption.

Total deposition of sulphur to coniferous forests in Sweden - Taking canopy exchange into account

In the low deposition situation of today at many of the long-term Swedish forest monitoring sites, the deposition measured as precipitation to the open field, i.e. bulk deposition of oxidized sulphur (S) is often higher or equal to deposition of S sampled under the forest canopies, i.e. as throughfall. This suggests that the total S deposition estimated using throughfall is underestimated. The reason for this is direct exchange of S with the forest canopies, leading to an underestimation which becomes evident in low-deposition areas. We describe a new method to estimate the dry deposition of S to coniferous forest based on measurements with Teflon string samplers as surrogate surfaces, in combination with measurements of the net throughfall for sodium (throughfall subtracted with wet deposition). The wet deposition was estimated from bulk deposition measurements on the open field, corrected for dry deposition to the collectors. The method was applied for Norway spruce forests at monitoring sites across Sweden during nine years 2014–2022, and total deposition was calculated based on wet deposition and the estimated dry deposition. The estimated annual total deposition of S as a mean value for coniferous forests ranged between 0.8 and 5.2 kg S ha−1 yr−1 with lowest values in northern Sweden and highest in southwest Sweden. The share of dry deposition of the total S deposition was between 20 and 53%. The mean annual deposition of S measured as throughfall during 2014–2022 for three different regions in Sweden was between 16 and 41% lower compared to the corresponding total deposition estimated with the new method. The canopy exchange of S was analyzed on a monthly basis as the difference between the estimated total deposition and the measured throughfall deposition of S. At most sites, there was a canopy uptake of S during the summer months and a leakage of S during the winter months. This indicates that the canopy exchange of S is a phenomenon that involves some biological activity.

Interfacial properties of CO2 and liquid sulfur in high-sulfur gas fields: Molecular simulations on carbonate mineral surfaces

As the global energy landscape transforms, the development of high-sulfur natural gas has become increasingly critical. However, sulfur deposition during these gas field developments significantly affects operational efficiency. This study employed molecular dynamics simulation to explore the effectiveness of CO2 in alleviating sulfur deposition on carbonate rock reservoirs. Specifically, it examined the interfacial tension between liquid sulfur and CO2, the wettability of sulfur on carbonate rock mineral surfaces, and the kinetics of CO2 displacing liquid sulfur. Results show that as CO2 pressure increases from 10 MPa to 60 MPa, the interfacial tension between liquid sulfur and CO2 decreases by 84 %, from 35.54 mN/m to 5.53 mN/m. The contact angles of sulfur droplets on calcite and dolomite surfaces stabilize at 41.82° ± 2.10° and 44.33° ± 3.27°, respectively, indicating greater sulfur spread on calcite surfaces. With higher CO2 pressures, sulfur deposition on mineral surfaces and interfacial tension both decrease significantly, while the wetting angle of liquid sulfur increases, particularly on dolomite. At 60 MPa CO2 pressure, the adsorption energy of dolomite for liquid sulfur drops from 364.56 kcal/mol to 25.46 kcal/mol, a 93 % reduction, suggesting CO2′s dual role in displacing sulfur and promoting its desorption from mineral surfaces. Furthermore, the efficiency of sulfur deposition alleviation in carbonate rock slit structures improves and stabilizes at around 40 MPa CO2 pressure. This study presents a potential environmentally friendly approach for efficiently developing high-sulfur gas fields, and its findings provide practical insights for optimizing CO2 injection strategies to mitigate sulfur deposition.

Total mercury and methylmercury in lake water in years before and after removal of mercury-polluted pulp fiber sediment

There is an elevated presence of mercury (Hg) in the biosphere because of anthropogenic activities. The resulting damage to ecosystems and human health increases dramatically when microorganisms produce highly toxic methylmercury (MeHg). Total Hg (THg), MeHg and ancillary water chemistry were measured in two connected lakes, separated by a short stream stretch, before (1996, 1998 and 2003) and after (2007, 2009 and 2010) the removal of Hg-polluted pulp fiber sediment. Over the study period, there was a decrease in sulfate in the surface water of both lakes, presumably because of declining atmospheric sulfate deposition. Together, the reductions in OM, sulfate, and Hg, resulted in decreased MeHg concentrations as well as decreased MeHg:THg ratios in the bottom water overlying the sediment. There was also a reduction in zooplankton MeHg and fish total Hg in both lakes. Multiple regressions, using the bottom water data before and after remediation from both lakes, indicated that both the yearly maximum MeHg concentration [MeHgmax] and MeHgmax:THg correlated positively with the simultaneously measured sulfate deficit (a proxy for microbial sulfate reduction) and inorganic Hg concentration (IHg = THg – MeHg). This may suggest that the removal of Hg and the decreased sulfate reduction not only led to a decrease in available Hg substrate for methylation but also disfavored the Hg methylation process. As opposed to sulfate deficit, other measurements reflecting heterotrophic microbial activity such as inorganic carbon (IC), ammonium (NH4+), and iron (Fe) did not show significant correlations with MeHg or MeHg:THg when the data from both lakes were combined.