Sulfur Release Research Articles

Nitrogen and sulphur release dynamics and kinetics in soils incubated with sulphur-augmented nitrogen sources

The study investigated N and S release dynamics and kinetics in soils incubated with sole and sulphur-augmented N fertilizer sources to evaluate their release patterns, potentially releasable quantities, and release rate constants. 50g of soil samples (from Ibadan and Ogbomoso, Nigeria) were measured into incubation cups and treated with Cattle Manure (CM) at 90 kg Nha-1, CM at 90 kg Nha-1+sulphur powder (SP) at 30 kg Sha-1, Cocoa Pod Powder (CPP) at 90 kg Nha-1, CPP at 90 kg Nha-1+SP at 30 kg Sha-1, NPK 20-10-10 at 90 kg Nha-1, NPK 20-10-10 at 90 kg Nha-1+SP at 30 kg Sha-1 and No Fertilizer Treatment (NFT). The incubated soils were moistened with distilled water at 60% field capacity thrice per week throughout a 105-day incubation period under ambient laboratory conditions and were analysed for N and S contents at 21, 42, 63, 84, and 105 days. The experiment was a completely randomized design with three replicates. Data on N and S release were evaluated, and fitted into zero, first- and second order kinetics equations. Release dynamics of N followed the order; NPK+SP/NPK/CPP+SP/CPP>CM+SP/CM>NFT in soils of both locations, while orders of S release were CPP+SP/CPP>CM+SP>CM/NPK+SP>NPK>NFT and CPP+S/CPP/CM+SP>CM>NPK+SP>NPK>NFT in soils of Ibadan and Ogbomoso, respectively. The release of N and S conformed to zero, first, and second order kinetics with coefficients of determination (R2), ranging from 0.20 to 0.99. Therefore, soil incorporation of sole and sulphur-augmented CM and CPP could be substituted for sole and sulphur-augmented NPK 21 days before planting of N and S-demanding crops.

Upgrading of kraft lignin pyrolysis products: Managing sulfur impurities

Pyrolysis stands as a powerful method for the valorization of biomass like kraft lignin, an aromatic-rich and sulfur-containing polymeric by-product from the pulping industry. Sulfur in the raw matrix is released during thermal processes and is redistributed in pyrolysis products. However, the presence of sulfur lowers the quality of products due to its corrosive and toxic character. In this work, commercial activated carbons have been used as adsorbents to remove the main sulfur compounds from the gas phase (i.e., CH3SH, COS, H2S). The analysis of sulfur content in biochar has been performed through SEM-EDXS, while the sulfur content in oils has been obtained by GC–MS analysis. The adsorption of sulfur on the activated carbon bed results in an enhancement of the release of sulfur in the gas phase from 34 % without activated carbon to 44 %. Up to 88 % of H2S removal is achieved after the adsorption step, together with a reduction of the overall sulfur content in the bio-oil rich in intermediates such as guaiacols and alkylated phenols. The residual sulfur contained in the liquid product is lowered to 3 % of the total sulfur in the system, thus improving the quality of the liquid pyrolysis product. This process limits the amount of sulfur in the gas and improves its quality and market value. At the same time, this results in a redistribution of sulfur in pyrolysis products such as bio-oil, improving its range of application as a source of chemical intermediates from kraft lignin.

Comparative experimental study on the co-firing characteristics of water electrolysis gas (HHO) and lean coal/lignite with different injection modes in a one-dimensional furnace

Zero-carbon fuels (H2/NH3) replacing coal co-firing is a promising way to address carbon emissions. Hydrogen co-firing helps improve combustion stability at low loads and control pollutant emissions. This study used a safer water electrolysis gas (HHO) for the multi-coal co-firing adaptability test. The effects of HHO injection mode and flow rate on combustion intensity, flue gas emissions, and fly ash characteristics were investigated. The results showed that HHO and lean coal/lignite co-firing could significantly increase the combustion temperature. The maximum temperature increases after co-firing were 108 °C and 95 °C. As the HHO increased, the CO2 in lignite co-firing increased, and CO and unburnt carbon decreased, while the opposite results were observed for lean coal (LC). At the 2200L/h HHO co-firing, CO2 decreases by 14.46 % and 27.22 % for LC premixed co-firing (PC) and staged co-firing (SC). Compared to SC, PC is more conducive to promoting the complete combustion of coke. The NOX emissions of HHO/LC co-firing are lower than those of pure coal, reaching the lowest value of ∼ 9 ppm under SC. As the HHO increases, the NOX of Lignite-PC first increases and then slowly decreases, while Lignite-SC has the opposite effect. Although various NOX emission trends are observed under different conditions, the results are dominated by a common mechanism − the competition between NOX reduction caused by HHO gas and the increase in co-firing temperature on NOX generation. The NOX of SC is all lower than that of PC. The SO2 emission from the LC co-firing decreases with the increase of HHO, while the SO2 from lignite increases. The SO2 of LC-SC can be reduced from ∼ 142 ppm to 0 ppm. HHO gas injection inhibits the release and oxidation of sulfur in lean coal. The differences in coal types lead to different changes in SO2 of co-firing. HHO gas reduced the SO3 content of lignite fly ash by 38.01 %. The high-temperature reduction atmosphere promotes the decomposition of sulfates and increases SO2 emissions. HHO co-firing refines the particle size of fly ash. The ultra-fine and micron particle matter (PM) increases, and the content of PM>100μm in Lignite-SC decreased by 10.32 %.

An ALCHEMI inspection of sulphur-bearing species towards the central molecular zone of NGC 253

Context. Sulphur-bearing species are detected in various environments within Galactic star-forming regions and are particularly abundant in the gas phase of outflow and shocked regions in addition to photo-dissociation regions. Thanks to the powerful capabilities of millimetre interferometers, studying sulphur-bearing species and their region of emission in various extreme extra-galactic environments (e.g. starburst and active galactic nuclei) and at a high-angular resolution and sensitivity is now possible. Aims. In this work, we aim to investigate the nature of the emission from the most common sulphur-bearing species observable at millimetre wavelengths towards the nuclear starburst of the nearby galaxy NGC 253. We intend to understand which type of regions are probed by sulphur-bearing species and which process(es) dominate(s) the release of sulphur into the gas phase. Methods. We used the high-angular resolution (1.6″ or ∼27 pc) observations from the ALCHEMI ALMA Large Program to image several sulphur-bearing species towards the central molecular zone (CMZ) of NGC 253. We performed local thermodynamic equilibrium (LTE) and non-LTE large velocity gradient (LVG) analyses to derive the physical conditions of the gas where the sulphur-bearing species are emitted, and their abundance ratios across the CMZ. Finally, we compared our results with previous ALCHEMI studies and a few selected Galactic environments. Results. To reproduce the observations, we modelled two gas components for most of the sulphur-bearing species investigated in this work. We found that not all sulphur-bearing species trace the same type of gas: strong evidence indicates that H2S and part of the emission of OCS, H2CS, and SO are tracing shocks, whilst part of SO and CS emission rather traces the dense molecular gas. For some species, such as CCS and SO2, we could not firmly conclude on their origin of emission. Conclusions. The present analysis indicates that the emission from most sulphur-bearing species throughout the CMZ is likely dominated by shocks associated with ongoing star formation. In the inner part of the CMZ where the presence of super star clusters was previously indicated, we could not distinguish between shocks or thermal evaporation as the main process releasing the S-bearing species.

Performance and mechanism of arsenic-metal separation in copper smelting flue gas regulated by chalcopyrite

To reduce the release of arsenic from non-ferrous metal (especially copper) smelting flue gases as well as to recover arsenic, the dry quenching process has been successfully applied to remove arsenic. However, the formation of arsenate hindered the separation of arsenic, thus reducing the collection efficiency. To tackle the bottleneck, the strategy of mineral phase regulation was proposed by the conversion from arsenate to sulfate, metal sulfate and gaseous arsenic were formed and separated each other. Chalcopyrite served as a potential sulfation regulator due to the gradual production of active sulfur (S2 dimer and S monomers) at high temperatures. At a chalcopyrite dosage of 60 %, the separation efficiency of arsenic from the metals reached 93.78 % and the residual arsenic content in the arsenic-copper particulate matter was decreased from 40.38 % to 3.12 % at 700 °C. The separation of arsenic and metal was attributed to the release of active sulfur from chalcopyrite, which enhanced the conversion of arsenate to sulfate. The separated arsenic enters the following section in the form of gaseous As2O3, which is beneficial to the dry quenching collection of arsenic. This provides theoretical and technical support for the clean production of nonferrous metal smelting and the control of arsenic pollution in flue gas.

Effect of long-term tillage practices on soil nitrogen, phosphorus and sulfur release under different nitrogen management options

The conservation agriculture (CA), presents a promising alternative for restoring soil health and achieving sustainable crop production. In addition, one cannot follow the same nitrogen management of conventional framing in the CA as the crop residue retained leads to N mineralization/immobilization. Hence, the present research was aimed to determine the effect of CA and nitrogen managements on soil nitrogen, phosphorus and sulfur release and the enzymes involved in their mineralization. The results revealed that the CA practice significantly enhanced the mineral N, Olsen P and CaCl2–S release and the soil enzymes involved in this mineralization cycles compared to CT + R plots. Similarly, all the nitrogen fertilizer receiving subplots also recorded significantly higher mineral N, Olsen P and CaCl2–S release and the enzymes involved compared to the control. Furthermore, throughout the incubation period the Urea super granule + Greenseeker treatment significantly outperformed the RDN plot with respect to NO3–N and CaCl2–S release. Whereas, the Urea + Greenseeker treatment registered significantly higher NO3–N and CaCl2–S over RDN plot from 30 and 45 days after incubation, respectively. The NH4–N and Olsen P release had increasing trend up to 45 days after incubation and thereafter it decreased. In nutshell, the research emphasizes the significance of CA alongside optimum nitrogen management approaches in enhancing the soil enzymatic activities and nutrient mineralization. These outcomes hold significance for both farmers and researchers seeking ecologically sound and productive agricultural methods to enhance crop output and maintain soil quality.

Sulfur release behavior and sulfur fixation mechanism during biomass microwave co-pyrolysis of Ascophyllum and rice straw

Co-pyrolysis with low-sulfur biomass is expected to improve the yield and quality of bio-fuels, without the usage of calcium-based desulfurizer. Sulfur transformation during microwave fluidized-bed co-pyrolysis between terrestrial and marine biomass (Ascophyllum, AS; Rice straw, RS) was investigated. Sulfur release was promoted during biomass co-pyrolysis, but it was inhibited during pyrolysis between AS and low-sulfur char. Thermal cracking of biomass was promoted during co-pyrolysis between biomass, accelerating the combination of H atoms and −SH radicals. Introduction of low-sulfur bio-char (CA) inhibited the generation of bio-char and the release of sulfur. Released sulfur was captured by –OH/C = C functional groups on bio-char through dehydration reactions/addition reactions, forming mercaptan in bio-char. Furthermore, introduction of microwave and bio-char promoted the cyclization and aromatization reaction, converting mercaptan to thiophene and improving the thermal stability of solid sulfur, and thus increasing in-situ sulfur fixation rate.

MODELING OF COAL-BASED COMPOSITE BRIQUETTES IN ORDER TO REDUCE SULFUR EMISSIONS INTO THE ATMOSPHERE

The tendency to abolish, to obtain heat from coal in order to reduce atmospheric pollution, leads to the closure of coal deposits. The alternative for obtaining heat, especially in the category of heating smaller residential buildings, with wood pellets, although acceptable from an ecological point of view, has its drawbacks, if one takes into account the scale of the required amount of energy and the role of the forest in purifying the air. Wood pulp and coal as basic energy carriers have hydrocarbon compounds. So, in both cases COx and NOx gases appear as gaseous products. The difference is in their scale. Unlike wood, coal also contains sulfur compounds, which makes it an environmentally unacceptable fuel. By adding a certain amount of wood pulp and additives to the coal mass, in this work, pyrophyllite shale, the impact on the energy and ecological aspects of heat release of such a complex fuel mixture was investigated. The ecological aspect is accentuated through the release of sulfur from coal. The mixture was subjected to the briquetting process, and the obtained samples were tested with relevant parameters, primarily the obtained lower heat value and sulfur content (SOx) in these products. The obtained results are very optimistic with both parameters mentioned above and can be a guide for further research for this idea. Key words: coal, wood sawdust, briquette, calorific value, sulfur, ecology.

Effect of lignin, cellulose and hemicellulose from biomass on sulfur release behavior from dyeing sludge combustion

Co-combustion with biomass is recommended for treating dyeing sludge (DS) from the view of minimizing sulfur emissions. However, the sulfur emission from DS combustion depends on the lignin (L)/cellulose (C)/hemicellulose (H) ratio in the biomass, which is frequently overlooked. This study reveals the effect of biomass on the combustion characteristics and sulfur evolutions of DS combustion using triphenylmethyl mercaptan (TM) and L/C/H as model representative compounds of DS and biomass, respectively. Results indicated that the combustion behavior of the TM–biomass mixture was dominated by TM and secondarily by L/C/H. Although L/C/H brought forward the TM combustion, these biomass components (especially L) deteriorated the combustibility and burnout performances of the combustion. L/C/H promoted CH3SH and SO2 release at low temperatures but inhibited these emissions at high temperatures. The sulfur retention ratios of L, C, and H were 7.53 %, −5.75 %, and 0.17 %. TM–L interaction initially promoted and later inhibited the co-combustion process and the CH3SH and SO2 release. L/C/H addition reduced the E values of the mixtures and the co-combustion kinetics were dominated by Dn models. Residue analysis also indicated a dominant role of L in sulfur fixation, mainly because L additive created abundant adsorption sites in the co-combustion residue.

Exposure of polyethylene microplastics affects sulfur migration and transformation in anaerobic system

Polyethylene (PE) microplastic, which is detected in various environmental media worldwide, also inevitably enters wastewater treatment plants, which may have an impact on anaerobic processes in wastewater treatment. In this work, the effect of PE microplastics on anaerobic sulfur transformation was explored. Experimental results showed that PE microplastics addition at 0.1%− 0.5% w/w promoted H2S production by 14.8%−27.4%. PE microplastics enhanced the release of soluble organic sulfur and inorganic sulfate, and promoted the bioprocesses of organosulfur compounds hydrolysis and sulfate reduction. Mechanism analysis showed that PE microplastics increased the content of electroactive components (e.g., protein and humic acids) contained in extracellular polymeric substances (EPS). In particular, PE microplastics increased the proportion and the dipole moment of α-helix, an important component involved in electron transfer contained in extracelluar protein, which provided more electron transfer sites and promoted the α-helix mediated electron transfer. These enhanced the direct electron transfer ability of EPSs, which might explain why PE microplastics facilitated the bioprocesses of organosulfur compounds hydrolysis and sulfate reduction. Correspondingly, metagenomic analysis revealed that PE microplastics increased the relative abundance of S2- producers (e.g., Desulfobacula and Desulfonema) and the relative abundance of functional genes involved in anaerobic sulfur transformation (e.g., PepD and cysD), which were beneficial to H2S production in anaerobic system.

Study on the Migration and Release of Sulfur during the Oxidizing Roasting of High-Sulfur Iron Ore

In China, most of the high-sulfur iron ores have not been fully developed and utilized due to the lack of breakthrough progress in the research on the sulfur migration and the desulfurization mechanism during the roasting process. This study will focus on revealing the release and fixation mechanisms of sulfur during the roasting process to achieve the transformation of desulfurization from terminal treatment to process control. Experimental results show that as the roasting temperature increases, the release rate of SO2 also increases, reaching the maximum release rate at 900 °C. Simultaneously, it is found that at the same roasting temperature, the release rate and amount of SO2 under the O2/N2 atmosphere is significantly greater than that under the pure N2 and air atmospheres. Meanwhile, X-ray diffraction (XRD) is utilized to explore the phase composition of the roasted product and the sulfur release mechanism. In addition, the adsorption energy, stability and electron transfer of SO2 on the CaO surface are calculated through density functional theory (DFT), and the optimal adsorption active site perpendicular to the O atom (O-top) is also determined. Finally, the sulfur fixing agent CaO is used to study the SO2 fixation mechanism. When the concentration reaches 10%, the sulfur fixation efficiency reaches more than 80%. Therefore, this work will present basic knowledge and systematic guidance for the sulfur migration and release of high-sulfur iron ore under the oxidizing roasting process.

Cloudlet capture model for the accretion streamer onto the disc of DG Tau

ABSTRACT DG Tau is a nearby T Tauri star associated with a collimated jet, a circumstellar disc, and a streamer a few hundred au long. The streamer connects to the disc at ∼50 au from DG Tau. At this location SO emission is observed, likely due to the release of sulphur from dust grains caused by the shock of the impact of the accretion streamer onto the disc. We investigate the possibility that the DG Tau streamer was produced via cloudlet capture on the basis of hydrodynamic simulations, considering a cloudlet initiating infall at 600 au from DG Tau with low angular momentum so that the centrifugal force is smaller than the gravitational force, even at 50 au. The elongation of the cloudlet into a streamer is caused by the tidal force when its initial velocity is much less than the free-fall velocity. The elongated cloudlet reaches the disc and forms a high-density gas clump. Our hydrodynamic model reproduces the morphology and line-of-sight velocity of CS (5 − 4) emission from the northern streamer observed with Atacama Large Millimeter/submillimeter Array. We discuss the conditions for forming a streamer based on the simulations. We also show that the streamer should perturb the disc after impact for several thousands of years.

Volcanic forcing of high-latitude Northern Hemisphere eruptions

High-latitude explosive volcanic eruptions can cause substantial hemispheric cooling. Here, we use a whole-atmosphere chemistry-climate model to simulate Northern Hemisphere (NH) high-latitude volcanic eruptions of magnitude similar to the 1991 Mt. Pinatubo eruption. Our simulations reveal that the initial stability of the polar vortex strongly influences sulphur dioxide lifetime and aerosol growth by controlling the dispersion of injected gases after such eruptions in winter. Consequently, atmospheric variability introduces a spread in the cumulative aerosol radiative forcing of more than 20%. We test the aerosol evolution’s sensitivity to co-injection of sulphur and halogens, injection season, and altitude, and show how aerosol processes impact radiative forcing. Several of these sensitivities are of similar magnitude to the variability stemming from initial conditions, highlighting the significant influence of atmospheric variability. We compare the modelled volcanic sulphate deposition over the Greenland ice sheet with the relationship assumed in reconstructions of past NH eruptions. Our analysis yields an estimate of the Greenland transfer function for NH extratropical eruptions that, when applied to ice core data, produces volcanic stratospheric sulphur injections from NH extratropical eruptions 23% smaller than in currently used volcanic forcing reconstructions. Furthermore, the transfer function’s uncertainty, which propagates into the estimate of sulphur release, needs to be at least doubled to account for atmospheric variability and unknown eruption parameters. Our results offer insights into the processes shaping the climatic impacts of NH high-latitude eruptions and highlight the need for more accurate representation of these events in volcanic forcing reconstructions.

Electroluminescence efficiency and stability of near ultraviolet organic light-emitting diodes based on BCPO luminous materials

To date, in the traditional method of obtaining near-ultraviolet (NUV) light, mercury atoms, which can create a highly toxic heavy metal contaminant, have been used. Therefore, it is an important issue to obtain NUV light by using new environmentally friendly devices. In the last decade, the fabrication of near ultraviolet organic light-emitting diodes (NUV-OLEDs) has become a research hotspot in the field of organic electronics. However, when the electroluminescence wavelength is extended to shorter than 400 nm, higher requirements are put forward for the materials used for each functional layer in these devices. In this work, a wide bandgap small molecule material of BCPO is used as the luminescent layer. The electron-transporting and hole-transporting materials are determined based on the overlaps between absorption spectra of these materials and emission spectrum of BCPO. And NUV-OLEDs with electroluminescent peak wavelength at 384 nm are prepared. By using the optimal device structure, the maximum external quantum efficiency of the device reaches 2.98%, and the maximum radiance of the device reaches 38.2 mW/cm<sup>2</sup>. In the electroluminescence spectrum, NUV light with wavelengths below 400 nm accounts for 57% of the light emission. In addition, the device demonstrates good stability when biased at two different constant voltage modes. The multiple key factors which affect the stability of the device are analyzed in detail. Firstly, it is found that the high glass transition temperature (<i>T</i><sub>g</sub>) of hole-transporting material is very important for the long-time stability of this device. The poor device stability is closely related to the low <i>T</i><sub>g</sub> temperature of hole-transporting material. Secondly, due to the widespread use of PEDOT:PSS as hole injection material in OLEDs, the electron leakage from the hole-transpor layer into the PEDOT:PSS layer may cause significant damage to the conducting polymer. When bombarded with low energy electrons, bond breakage occurs on the surface of PEDOT:PSS, followed by the release of oxygen and sulfur, resulting in changes in conductivity and oxidation reactions with molecules of hole transport material. Thirdly, the photoelectrical stability of organic molecules is the most fundamental reason that restricts the device lifetime. The aging process of material or device is directly relevant to the bond dissociation energy (BDE) of organic molecule. Generally, the BDE value of organic molecule is not high enough. As a result, molecules are prone to chemical bond breakage during electrochemical or photochemical aging. In summary, highly stable NUV-OLEDs should be fabricated by using hole-transporting materials with high <i>T</i><sub>g</sub> temperature, sufficient electron-blocking capacity, and large BDE value.

Effect of rock phosphate and bacteria solubilizing nutrients soil application on yield and fruit quality of olive trees cv. “Picual” under the arid zones

This study was carried out throughout two seasons and Located in a private olive grove on Cairo-Ismailia Desert Road in Egypt. The aim of this experiment was to use different amounts of rock phosphate (1, 2 or 3 kg/tree) with different time of additions (2 or 3 times) for phosphorous and sulfur release bacteria to form 6 treatments beside the control (untreated trees) on the mineral contents of the leaves, the vegetative growth, the yield, and the quality of the fruit of Picual olive trees planted in sandy soil and watered with drip irrigation for two seasons. The outcomes demonstrated that application of 2 or 3 kg rock phosphate per tree for two or three times of phosphorus and sulfur release bacteria gave the highest yield and improves fruit quality. Generally, the treatment of 2 kg rock phosphate for three times of P and S release bacteria is recommended due to its clear effect among all treatments on the abovementioned parameters.

Coupled Simulation of Chemical Membrane Degradation and Oxygen Crossover in PEM Water Electrolysis

The membrane of polymer electrolyte membrane water electrolysis (PEMWE), as one of the lifetime limiting components, does not only have an impact on performance, but also plays an important role for safety issues over time. Membrane thinning is a key phenomenon caused by chemical membrane degradation and directly affects the conductivity and gas crossover. Therefore, a chemical membrane degradation model based on Fenton equations [1,2] coupled with a gas crossover model [3] is presented in this work. The presence of Oxygen at cathode side is considered by oxygen crossover, which is strongly enforced by supersaturation effects. Specifically, this cathode-side oxygen is conducive to hydrogen peroxide formation. In interaction with metal ions, e.g. iron, from the feed water, which partially migrate through the membrane, hydroxyl radicals can be formed. These attack the polyfluorinated sulfonicacid (PFSA) membrane at different points, releasing sulfon acid head groups (SO3H-) and fluride ions (F-), which can be measured as sulfur release rates (SRR) and fluride release rates (FRR) in the effluent water, respectively. The degradation model provides concentration profiles for the relevant species involved in the process, which, e.g., influence the thickness and conductivity of the membrane via structure-function relations. In particular, the changed thickness again influences the crossover effect, which itself represents an input for the degradation model. Through this coupling, both models can be updated at specific times. Implications of the model-based analysis on the mechanistic understanding of chemical membrane degradation by radical attack in PEMWE are discussed. Furthermore, the model results can be verified and calibrated by experimental data in combination with adapted accelerated stress tests (AST) and also encourage their enhancement.

Delayed recovery of surface water chemistry from acidification in subtropical forest region of China

The three largest acid rain regions of current earth are located in northern and western Europe, eastern North America, and East Asia. Sulfur and nitrate concentrations in headwater streams in Europe and North America decreased as atmospheric sulfur and nitrogen deposition decreased, albeit with a considerable delay. However, how water chemistry responds to the declining sulfur and nitrogen deposition in China is unclear. The regional survey of surface water chemistry during 2010 and 2018 within the Sichuan Basin in southwestern China showed that the recovery of the surface water chemistry was delayed for at least 5 years owing to the release of previously deposited sulfur and nitrogen stored in the soil. After sulfur deposition declined from its peak value, the subregions of purplish soil with low sulfate adsorption capacity still exhibited a net sulfur release in 2010, but this release was no longer evident by 2018. The subregions with the red and yellow soils, which have a high sulfate adsorption capacity, operated as sulfur sinks during 2010 and 2018, indicating a continuous immobilization process through sulfate reduction despite a decrease in sulfur deposition. Additionally, this sulfate reduction countered the release of sulfate caused by sulfur desorption. There was a substantial nitrogen sink within the Sichuan Basin. Nitrogen leaching decreased slowly with the declined nitrogen deposition, except in regions where nitrogen deposition exceeded the critical threshold. Compared to temperate forest regions in Europe, the Sichuan Basin and its surrounding areas have experienced higher decline rates in the leaching of sulfur and nitrogen, highlighting that the subtropical forest region undergoes a faster restoration of surface water chemistry.

Study of the Release of Agricultural Sulfur and Sulfur Associated with Natural Gas under the Influence of Different Temperatures, Incubation Times and Soil Texture

laboratory experiment was carried out to study the effect of temperature (25, 35, and 45 °C) and incubation duration (15, 30, 45, 60, 90, and 120 days) with the addition of two sulfur sources (agricultural sulfur and sulfur associated with natural gas) at a level of 2000 mg S kg-1 in dissolved sulfur soil concentration in sandy loam and clay loam soils, with choosing the best temperature to be applied in the kinetic model of sulfur in soil. The temperature and incubation duration results indicated an increase in dissolved sulfur in the agricultural sulfur treatment in both study soils. Also, the 35 °C treatment gave the highest dissolved sulfur compared to the other temperatures, and the incubation period of 120 days recorded the highest amount of dissolved sulfur released. The dual interaction treatment of the sandy loam soil at a temperature of 35 °C and the fertilizer source (agricultural sulfur) gave the largest values of dissolved sulfur in the soil solution, which reached 12.60 mmol S L-1. While clay loam soil at a temperature of 35 °C gave agricultural sulfur the highest values, amounting to 30.68 mmol S L-1.

Prominent Role of Sulfate Reduction in Considerable Sulfur Retention in a Subtropical Soil

AbstractThe sulfur biogeochemical cycle controls the sulfur dynamics in the soil. In contrast to almost all deposited sulfur leaching out in temperate catchments, approximately 80% of the deposited S is retained in the catchments in subtropical regions. However, the mechanisms for sulfur retention were unclear, hindering the understanding of potential threats of legacy sulfur with environmental changes. Here, we demonstrated that sulfate reduction (as sulfide fixed in soil) was a prominent yet overlooked mechanism for sulfur retention in addition to the widely recognized sulfate adsorption in soil, based on a study on soil sulfur storage and stable isotope signatures within entire soil profiles in a typical subtropical catchment in China. Using a dual‐isotopic model, the sulfate reduction flux was further determined to be 30% of the S deposition. Due to a lot of deposited sulfur fixed via sulfate reduction, the release of soil legacy sulfur would be less in response to decreasing sulfur deposition compared to the projections only considering adsorption. However, the remobilization of large amounts of reduced S should be regarded as a threat to the environment under climate change in the future.

Effect of electromagnetic induction drying on the drying–incineration process of dyeing sludge: focus on migration and conversion of sulfur

Secondary sulfur pollution in dyeing sludge (DS) during drying and incineration is a major environmental problem necessitating in-situ control. To robustly immobilise sulfur during drying–incineration, the authors introduce an electromagnetic induction (EMI) drying method and reveal the corresponding migration and conversion of sulfur in DS. The EMI-drying efficiency reached 10.69%/min, five times that of thermal drying. EMI drying increases the relative sulfoxide ratio from that of thermal drying. In a sludge–sulfur model, the proposed treatment promoted the oxidation and decomposition of organic sulfur without noticeably affecting the inorganic sulfur. The selective oxidation process during EMI drying promotes sulfur stabilisation in dried DS, decreasing the performance and stability of DS combustion. The sulfur-containing pollutants released during the incineration of DS mainly contain H2S, followed by CH3SH and SO2. EMI drying increases the outputs of SO2 and CH3SH but decreases the outputs H2S and total sulfur compared with the outputs of thermal drying. Under the sulfur-model conditions, EMI promoted the conversion of inorganic sulfur to sulfur-containing gases (especially H2S) during incineration. In contrast, the sulfur stabilised by partial oxidation of organic sulfur in the EMI-dried DS was not easily converted to gaseous sulfur during subsequent combustion. Overall, EMI inhibits the release of sulfur during the combined drying–incineration process of DS.