H2S Release Research Articles

Novel controlled and targeted releasing hydrogen sulfide system exerts combinational cerebral and myocardial protection after cardiac arrest

BackgroundCardiac arrest (CA) is a leading cause of death worldwide. Even after successful cardiopulmonary resuscitation (CPR), the majorities of survivals are companied with permanent myocardial and cerebral injury. Hydrogen sulfide (H2S) has been recognized as a novel gasotransmitter exerting multiple organ protection; however, the lacks of ideal H2S donors which can controlled release H2S to targeted organs such as heart and brain limits its application.ResultsThis work utilized mesoporous iron oxide nanoparticle (MION) as the carriers of diallyl trisulfide (DATS), with polyethylene glycol (PEG) and lactoferrin (LF) modified to MIONs to acquire the prolonged circulation time and brain-targeting effects, and a novel targeted H2S releasing system was constructed (DATS@MION-PEG-LF), which exhibited excellent biocompatibility, controlled-releasing H2S pattern, heart and brain targeting features, and the ability to be non-invasive traced by magnetic resonance imaging. DATS@MION-PEG-LF presented potent protective effects against cerebral and cardiac ischemic injury after CA in both in vitro hypoxia/reoxygenation models and in vivo CA/CPR models, which mainly involves anti-apoptosis, anti-inflammatory and anti-oxidant mechanisms. Accordingly, the cardiac and cerebral functions were obviously improved after CA/CPR, with potentially improved survival.ConclusionsThe present work provides a unique platform for targeted controlled release of H2S based on MIONs, and offers a new method for combinational myocardial and cerebral protection from ischemic injury, bringing considerable benefits for CA patients.

H2S prevents peripheral immune cell invasion, increasing [Ca2+]i and excessive phagocytosis following hypoxia-ischemia injury in neonatal mice

We previously reported that L-Cysteine, H2S donor, remarkably attenuated neuroinflammation following hypoxia-ischemia (HI) brain injury in neonatal mice. However, its anti-inflammatory mechanism for HI insult is still unknown. The study focus on the effects of L-Cysteine on immune cell populations, Ca2+ mobilization and phagocytosis after neonatal HI. We found that L-Cysteine treatment skewed CD11b+/CD45low microglia and CD11b+/CD45high brain monocytes/macrophages towards a more anti-inflammatory property 72 h after HI-injured brain. Moreover, L-Cysteine treatment reduced cerebral infiltration of CD4 T cells 7 days following HI insult. Furthermore, CD4 T cell subset analysis revealed that L-Cysteine treatment decreased Th1 and Th2 counts, while increased Th17/Th2 ratio. Moreover, L-Cysteine treatment suppressed LPS-induced cytosolic Ca2+ and LPS-stimulated phagocytosis in primary microglia. The anti-inflammatory effect of L-Cysteine was associated with improving neurobehavioral impairment following HI insult. Our results demonstrate L-Cysteine treatment suppressed the invasion of peripheral immune cells, increasing [Ca2+]i and excessive phagocytosis to improve neurobehavioral deficits following hypoxia-ischemia injury in neonatal mice by H2S release.

Evaluation of thionolactones as a new type of hydrogen sulfide (H2S) donors for a blood pressure regulation

Hydrogen sulfide (H2S) is a gaseous molecule that exhibits various biological effects. For example, H2S has been recognized as a blood pressure-lowering agent. Presented in this report is a new modifiable platform for H2S supply, its preparation and H2S release kinetics from a series of structurally diversified thionolactones. Furthermore, the properties of the obtained H2S donors were evaluated in both in vitro and in vivo studies. The kinetic parameters of H2S release were determined and compared with NaHS and pyrrolidine-2-thione, a thiolactame analog, using a fluorescence detection method based on 7-azido-4-methyl-2H-chromen-2-one probe. We have shown that H2S release rates from the developed compounds are controllable through structural modifications. This study shows that both the thiono-lactone ring's size and the presence of a methyl group in the thiono-lactone ring significantly influenced the rate of H2S release. Finally, we have found a significant hypotensive response to intravenous administration of the developed donors in anesthetized rats.

A cysteine-triggered fluorogenic donor base on native chemical ligation for tracking H2S delivery in vivo.

A hydrogen sulfide (H2S) donor is a fundamental molecular tool used as an exogenous source in biological studies and therapies. However, finding a controllable and visual fluorescent H2S donor is difficult. We report a new H2S donor, HSD560, the H2S release of which is triggered by cysteine. Importantly, the H2S generation is accompanied with enhanced green fluorescence, which could be utilized to track H2S release in cells using microscopy. H2S release from HSD560 undergoes a non-enzymatic native chemical ligation (NCL) process, which provides an accurate match with activated fluorescence and localization of H2S in zebrafish.

A novel dendritic mesoporous silica based sustained hydrogen sulfide donor for the alleviation of adjuvant-induced inflammation in rats

Purpose S-propargyl-cysteine (SPRC), an excellent endogenous hydrogen sulfide (H2S) donor, could elevate H2S levels via the cystathionine γ-lyase (CSE)/H2S pathway both in vitro and in vivo. However, the immediate release of H2S in vivo and daily administration of SPRC potentially limited its clinical use. Methods To solve the fore-mentioned problem, in this study, the dendritic mesoporous silica nanoparticles (DMSN) was firstly prepared, and a sustained H2S delivery system consisted of SPRC and DMSN (SPRC@DMSN) was then constructed. Their release profiles, both in vitro and in vivo, were investigated, and their therapeutical effect toward adjuvant-induced arthritis (AIA) rats was also studied. Results The spherical morphology of DMSN could be observed under scanning Electron Microscope (SEM), and the transmission electron microscope (TEM) images showed a central-radiational pore channel structure of DMSN. DMSN showed excellent SPRC loading capacity and attaining a sustained releasing ability than SPRC both in vitro and in vivo, and the prolonged SPRC releasing could further promote the release of H2S in a sustained manner through CSE/H2S pathway both in vitro and in vivo. Importantly, the SPRC@DMSN showed promising anti-inflammation effect against AIA in rats was also observed. Conclusions A sustained H2S releasing donor consisting of SPRC and DMSN was constructed in this study, and this sustained H2S releasing donor might be of good use for the treatment of AIA.

Optimisation of the operational parameters for a comprehensive bioelectrochemical treatment of acid mine drainage

Bioelectrochemical systems provide a promising tool for the treatment of acid mine drainage (AMD). Biological sulphate reduction powered with electrical energy consumes acidity and produces sulphide, which can precipitate metals. However, the produced sulphide and the changes in pH resulting from the biological processes affect the efficiency and the environmental impacts of this treatment significantly. In this work, the effects of pH and sulphur speciation on the sulphate reduction rate (SRR) and comprehensive AMD treatment were evaluated in two-chamber microbial electrolysis cells at a cathode potential of −0.8 V vs. NHE. The increase of initial sulphate concentration from below 1000 mg to above 1500 mg S-SO42–/L increased SRR from 121 ± 25 to 177 ± 19 mg S-SO42–/L/d. SRR further increased to 347 mg S-SO42–/L/d when the operation mode was changed from batch to periodical addition of sulphate and acidity (363 mg S-SO42–/L/d and 22.6 mmol H+/L/d, respectively). The average SRR remained above 150 mg S-SO42–/L/d even at pH above 8.5 and with the total dissolved sulphide concentration increasing above 1300 mg S-TDSu/L. Operation at pH above 8 enabled the recovery of over 90% of the sulphur as dissolved sulphide and thus assisted in minimising the formation and release of toxic H2S.

Microfluidic fabrication of inhalable large porous microspheres loaded with H2S-releasing aspirin derivative for pulmonary arterial hypertension therapy

Hydrogen sulfide (H2S) has recently emerged as a novel gaseous mediator with protective actions in the treatment of pulmonary arterial hypertension (PAH). However, the therapeutic potential of H2S in PAH has been substantially hampered due to the lack of appropriate donors that could mimic the slow and continuous generation of H2S in vivo. Large porous microspheres (LPMs) have low density and large surface area leading to excellent absorption capabilities and aerodynamic properties. They are extensively studied as pulmonary delivery carriers for controlled and sustained release of drug molecules in the treatment of pulmonary disorders. Therefore, we hypothesized that LPMs containing H2S-releasing aspirin derivative (ACS14), a novel synthetic H2S donor may be a feasible option to facilitate the use of H2S in PAH treatment. LPMs were prepared with a biodegradable polymer, poly(lactic-co-glycolic acid) (PLGA) by a microfluidic technique. Surface morphology, lung deposition characteristics, safety and H2S release profiles of the formulation were evaluated. The resulting ACS14-containing LPMs (ACS14 MSs) displayed excellent aerodynamic properties (mass median aerodynamic diameter of 4.4 ± 0.4 μm), desirable drug loading and entrapment efficiency (25.8 ± 2.7% and 77.4 ± 6.9%, respectively) with slow and sustained H2S release for 24 h and negligible cytotoxicity (~95% cell viability). Daily intratracheally administered with ACS14 MSs elicited improvement in the severity of PAH in a rat model of monocrotaline-induced PAH, with comparable efficacy to oral administration with sildenafil, a conventional PAH treatment. It also inhibited the process of endothelial-to-mesenchymal transition (EndMT), an important process in vascular remodeling of PAH by suppressing the induction of NF-κB-Snail pathway. Moreover, ACS14 MSs dose-dependently inhibited TGF-β1-induced EndMT and the activation of NF-κB-Snail pathway in human pulmonary artery endothelial cells. In conclusion, our findings demonstrated that the designed microfluidics-assisted ACS14-containing LPMs have shown great potential to be used as an inhalable and efficacious H2S donor in the treatment of PAH.

Treatment of halitosis with photodynamic therapy in older adults with complete dentures: A randomized, controlled, clinical trial.

Halitosis of oral origin is mainly caused by the release of H2S (hydrogen sulfide) by bacteria lodged on the tongue. Antimicrobial photodynamic therapy (aPDT) has been evaluated for the treatment of halitosis, but there are no previous reports of the use of this treatment modality in older people with dentures. The aim of the present study was to compare the effect of aPDT and tongue scraping (standard treatment) in older people with complete dentures diagnosed with halitosis (H2S gas concentration>112 ppb). The participants were divided into two groups: G1- treatment with a tongue scraper (n = 20); G2- treatment with aPDT (n = 20). Halimeter testing was performed before and after treatments using gas chromatography and was repeated after seven days. After treatment, the group treated with aPDT had a lower mean concentration of H2S gas (18.5 ppb) than the tongue scraping group (185.3 ppb). After one week, the mean concentration of H2S increased to 218.2 ppb in the tongue scraping group and 39 ppb in the PDT group. Both treatments were able to reduce the concentration of H2S but only treatment with aPDT was able to decrease halitosis to socially unnoticeable levels. Moreover, this normal breath condition remained for seven days only in the aPDT group.

Pyrolysis of vulcanized styrene-butadiene rubber via ReaxFF molecular dynamics simulation

Styrene-butadiene rubber (SBR) is widely used in tires in the automotive segment and vulcanization using sulfur is a common process to enhance its mechanical properties. However, the addition of sulfur as the cross-linking agent usually results in impurities in pyrolysis products during rubber recycling, and thus the desulfurization during tire pyrolysis attracts much attention. In this work, the pyrolysis of vulcanized SBR is studied in detail with the help of ReaxFF molecular dynamics simulation. A series of cross-linked SBR models were built with different sulfur contents and densities. The following ReaxFF MD simulations were performed to show products distributions at different pyrolysis conditions. The simulation results show that sulfur products distribution is mainly controlled by sulfur contents and temperatures. The reaction mechanism is proposed based on the analysis of sulfur products conversion pathway, where most sulfur atoms are bonded with hydrocarbon radicals and the rest transfer to H2S. High sulfur contents tend to the formation of elemental sulfur intermediate, and temperature increase facilitates the release of H2S.

A Dinuclear Persulfide‐Bridged Ruthenium Compound is a Hypoxia‐Selective Hydrogen Sulfide (H2S) Donor

AbstractHydrogen sulfide (H2S) is a gaseous molecule that has received attention for its role in biological processes and therapeutic potential in diseases, such as ischemic reperfusion injury. Despite its clinical relevance, delivery of H2S to biological systems is hampered by its toxicity at high concentrations. Herein, we report the first metal‐based H2S donor that delivers this gas selectively to hypoxic cells. We further show that H2S release from this compound protects H9c2 rat cardiomyoblasts from an in vitro model of ischemic reperfusion injury. These results validate the utility of redox‐activated metal complexes as hypoxia‐selective H2S‐releasing agents for use as tools to study the role of this gaseous molecule in complex biological systems.

Hydrogen sulfide facilitates reprogramming and trans-differentiation in 3D dermal fibroblast.

The efficiency of cell reprogramming in two-dimensional (2D) cultures is limited. Given that cellular stemness is intimately related to microenvironmental changes, 3D cell cultures have the potential of overcoming this limited capacity by allowing cells to self-organize by aggregation. In 3D space, cells interact more efficiently, modify their cellular topology, gene expression, signaling, and metabolism. It is yet not clear as how 3D culture environments modify the reprogramming potential of fibroblasts. We demonstrate that 3D spheroids from dermal fibroblasts formed under ultra-low attachment conditions showed increased lactate production. This is a requisite for cell reprogramming, increase their expression of pluripotency genes, such as OCT4, NANOG and SOX2, and display upregulated cystathionine-β-synthase (CBS) and hydrogen sulfide (H2S) production. Knockdown of CBS by RNAi suppresses lactic acid and H2S production and concomitantly decreases the expression of OCT4 and NANOG. On the contrary, H2S donors, NaHS and garlic-derived diallyl trisulfide (DATS), promote the expression of OCT4, and support osteogenic trans-differentiation of fibroblasts. These results demonstrate that CBS mediated release of H2S regulates the reprogramming of dermal fibroblasts grown in 3D cultures and supports their trans-differentiation.

Investigation of the influencing factors in odor emission from wet-end white water

Emission of malodorous gases, such as volatile organic compounds (VOCs), hydrogen sulfide (H2S), and ammonia (NH3) during pulping and papermaking has caused certain harm to the air environment and human health. This paper investigated the influencing factors of odor emission from wet-end white water during the pro-duction of bobbin paper in a papermaking mill using old corrugated containers (OCC) as raw material. The concentration of malodorous gases emitted from wet-end white water was determined with pump-suction gas detectors. The results indicated that low temperature could limit the release of malodorous gases from white water. Specifically, no total volatile organic compounds (TVOC), H2S, and NH3 was detected at a temperature of 15°C. The concentrations of malodorous gases were slightly increased when temperature increased to 25°C. When temperature was 55°C, the released concentrations of TVOC, H2S, and NH3 were 22.3 mg/m3, 5.91 mg/m3, and 2.78 mg/m3, respectively. Therefore, the content of malodorous gases significantly increased with the temperature increase. The stirring of white water accelerated the release of malodorous gases, and the release rate sped up as the stirring speed increased. However, the total amount of malodorous gases released were basically the same as the static state. Furthermore, the higher the concentration of white water, the greater the amount of malodorous gases released. The pH had little influence on the TVOC release, whereas it significantly affected the release of H2S and NH3. With the increase of pH value, the released amount of H2S and NH3 gradually decreased. When pH reached 9.0, the release amount of H2S and NH3 was almost zero, proving that an alkaline condition inhibits the release of H2S and NH3.

Specific H2S Release from Thiosulfate Promoted by UV Irradiation for Removal of Arsenic and Heavy Metals from Strongly Acidic Wastewater.

The removal of arsenic and heavy metals (HMs) from strongly acidic wastewater by hydrogen sulfide (H2S) is an efficient method. However, traditional sulfuration reagents (Na2S, FeS, CaS, etc.) rapidly release H2S under acidic conditions via spontaneous hydrolysis, leading to serious H2S pollution. Herein, a H2S release process employing thiosulfate as a sulfuration reagent was proposed to eliminate H2S pollution. We found that thiosulfate can release H2S with specificity both in the dark and under ultraviolet (UV) irradiation under acidic conditions. In the absence of arsenic/HMs, H2S is not released because the formed H2S is consumed by a thiosulfate decomposition product, sulfite, or by its photolysis. In the presence of arsenic/HMs, H2S is released because the formed H2S immediately reacts with arsenic/HMs to generate sulfide precipitates rather than being consumed. The efficiency of transforming thiosulfate to H2S under UV irradiation is 2.5-fold the efficiency in the dark, because UV irradiation promotes the transformation of "effective sulfur" in thiosulfate molecules to form H2S through the transformation of HS· and S2O3• - radicals. Moreover, more than 99.9% of arsenic/HMs were removed from strongly acidic wastewater without producing H2S pollution under UV irradiation. This thiosulfate-based H2S-specific release process solves the problem of H2S pollution under acidic conditions.

Intelligent H2S release coating for regulating vascular remodeling

Coronary atherosclerotic lesions exhibit a low-pH chronic inflammatory response. Due to insufficient drug release control, drug-eluting stent intervention can lead to delayed endothelialization, advanced thrombosis, and unprecise treatment. In this study, hyaluronic acid and chitosan were used to prepare pH-responsive self-assembling films. The hydrogen sulfide (H2S) releasing aspirin derivative ACS14 was used as drug in the film. The film regulates the release of the drug adjusted to the microenvironment of the lesion, and the drug balances the vascular function by releasing the regulating gas H2S, which comparably to NO promotes the self-healing capacity of blood vessels. Drug releasing profiles of the films at different pH, and other biological effects on blood vessels were evaluated through blood compatibility, cellular, and implantation experiments. This novel method of self-assembled films which H2S in an amount, which is adjusted to the condition of the lesion provides a new concept for the treatment of cardiovascular diseases.

Tuning small molecule release from polymer micelles: Varying H2S release through crosslinking in the micelle core

Polymer micelles, used extensively as vehicles in the delivery of active pharmaceutical ingredients, represent a versatile polymer architecture in drug delivery systems. We hypothesized that degree of crosslinking in the hydrophobic core of amphiphilic block copolymer micelles could be used to tune the rate of release of the biological signaling gas (gasotransmitter) hydrogen sulfide (H2S), a potential therapeutic. To test this hypothesis, we first synthesized amphiphilic block copolymers of the structure PEG-b-P(FBEA) (PEG = poly(ethylene glycol), FBEA = 2-(4-formylbenzoyloxy)ethyl acrylate). Using a modified arm-first approach, we then varied the crosslinking percentage in the core-forming block via addition of an O,O'-alkanediyl bis(hydroxylamine) crosslinking agent. We followed incorporation of the crosslinker by 1H NMR spectroscopy, monitoring the appearance of the oxime signal resulting from reaction of pendant aryl aldehydes on the block copolymer with hydroxylamines on the crosslinker, which revealed crosslinking percentages of 5, 10, and 15%. We then installed H2S-releasing S-aroylthiooxime (SATO) groups on the crosslinked polymers, yielding micelles with SATO units in their hydrophobic cores after self-assembly in water. H2S release studies in water, using cysteine (Cys) as a trigger to induce H2S release from the SATO groups in the micelle core, revealed increasing half-lives of H2S release, from 117 ± 6 min to 210 ± 30 min, with increasing crosslinking density in the micelle core. This result was consistent with our hypothesis, and we speculate that core crosslinking limits the rate of Cys diffusion into the micelle core, decreasing the release rate. This method for tuning the release of covalently linked small molecules through modulation of micelle core crosslinking density may extend beyond H2S to other drug delivery systems where precise control of release rate is needed.

Case study of H2S release and transport in a trunk sewer with drops.

Field work was performed to investigate the release of hydrogen sulphide (H2S) and its transport in the sewer trunk with drops in the Bonnie Doon area in Edmonton, Alberta, Canada, in order to develop a proper odor control strategy. The liquid sulfide concentration in the upstream trunk was low (less than 1.0 mg/L), and no H2S gas was detected in the head space under this low concentration. However, high H2S gas concentration was detected in the middle reach of the trunk due to the stripping effect of the three drops (2.7 m, 5.2 m and 2.0 m) along the trunk. The released H2S at drops was then transported in the sewer system and emitted at various locations and caused odor concerns. These drops played an important role in H2S release, and the overall H2S mass transfer coefficient at drops was much higher than that in normal gravity sewers. The overall oxygen and H2S mass transfer coefficient (KLa) was estimated to be around 200 h-1 and 300 h-1 at the first two drops, respectively. Field sampling of biofilm indicates that Desulfomicrobium was identified as the sulfate-reducing bacteria (SRB) responsible for sulfide generation in sewer wall biofilm and Thiobacillus was the only predominant member in manhole wall biofilm contributing to sewer manhole corrosion.

Emission of Hydrogen Sulfide from Falling Droplets in Sewage Drop Structures

Hydrogen sulfide (H2S) is the primary cause of odor and corrosion in sewer systems. When wastewater breaks up into small droplets in drop structures, the emission of H2S is expected to be significantly enhanced relative to that of the continuously falling sewage. However, limited studies have been conducted on the mass transfer coefficient, KL, of dissolved gas in falling water droplet emissions into air. In this study, laboratory experiments of falling liquid droplets in air were conducted with two gases: H2S and carbon dioxide (CO2). In the droplet diameter (3.02–4.68 mm) and free-falling height (0.1–1.5 m) testing ranges, the KL value at 20°C was found to be 0.9–4.5×10−4 m/s, which increased with the falling height (or velocity) and decreased with the droplet size. Existing prediction equations show a great range (up to 10 times) for KL and cannot accurately predict the experimental results. Therefore, a modified equation was proposed to better predict KL. In addition, CO2 was found to be a suitable surrogate for H2S in mass transfer due to the toxicity of H2S. Finally, the research results were applied in large and small sewage drop structures. More than 70% of H2S emission to equilibrium could be achieved after falling 15 m in large drop structures depending on droplet sizes. In small drop structures, the results of free-falling water droplets were found to approximately model the complex H2S emission process. This study provides new insights into the physical process and modeling of H2S release in sewage drop structures, which are useful for odor and corrosion control in municipal drainage systems.

Ammonia and hydrogen sulphide odour emissions from different areas of a landfill in Hangzhou, China

This study examined the release characteristics of malodorous ammonia (NH3) and hydrogen sulphide (H2S) gases in different areas of a full-capacity operational landfill in Hangzhou, China. Gas samples were collected using static boxes from exposed working areas (EWAs), temporarily covered areas (TCAs), and final closure areas (FCAs), and were analysed using spectrophotometric methods. Gas release increased in the following order: TCA > EWA > FCA. The average concentrations of released NH3 in these areas were 2763, 1171, and 27 mg m-3, respectively, and those of H2S were 2481, 631, and 10 mg m-3, respectively. The concentrations of gases released from holes in the film in the temporarily covered and EWAs were significantly higher than the AEGL-3 level values specified by the Acute Exposure Guideline Levels (AEGL) Advisory Committee. EWAs were identified as key for odour control, where the highest NH3 release was recorded at approximately 12:00. The diurnal variation in H2S release was insignificant (p > 0.05). Therefore, the study shows that working in EWAs should be avoided at approximately noon. Adverse impacts on human health can be reduced by standardising procedures, using higher-quality films, and improving film installation procedures. The results of this study serve as a valuable reference for odour control in operational landfills.

Subtill nonglacial deposits and their climatic implications for the Last Interglacial (MIS 5e), Hudson Bay Lowlands, Canada

In Hudson Bay Lowlands (HBL), the Wisconsinan tills are often underlain by organic-bearing nonglacial deposits formed during episodes of significant reduction of ice volumes or complete ice-free conditions in this region. The subtill nonglacial deposits, often correlated with the Missinaibi Formation, are beyond the method limit of radiocarbon dating in general. As such, they have been a subject of debates for their stratigraphy and associated climatic conditions owing to poor age constraints. Extensive studies were undertaken on a subtill argillaceous lacustrine deposit uncovered recently on the Winisk River. This 9 m thick organic-rich deposit, referred to as the Webequie Beds, was dated at 121 ± 9 ka, 126 ± 24 ka and 105 ± 11 ka using optically stimulated luminescence (OSL) dating method and correlated with the Last Interglacial (LIG) or Marine Isotope Stage (MIS) 5e. Pollen and plant macrofossils suggest spruce boreal forests along with extensive wetlands, not unlike what exists in the HBL today. Of particular note is the sporadic rise of birch in the upper part of the pollen sequence, interpreted as a response to the availability of frequent forest clearance by fires under a warmer climate. The birch zone is noteworthy because it corresponds to the development of conspicuous S-rich, ferromagnetic nodules (0.125–1.5 mm diameter) in the lake sediment. The nodules comprise native sulphur and greigite (Fe3S4), along with iron oxyhydroxide goethite and lepidocrocite. They likely resulted from significant warming during this interval that enhanced microbial sulphate reduction and increased the release of H2S, an essential component for the formation of the S minerals in the lake. Besides the strengthened microbial metabolization, a prolonged summer lake stratification and development of an anoxic bottom water also likely promoted the sulphate reduction. Although confirmation is needed, the warming probably linked to the LIG thermal maximum (∼120 ka) when a climate with a higher summer temperature than today prevailed. A similar subtill nonglacial deposit on the Little Current, a tributary of the Albany River, was also examined for comparison. Apart from a similar pollen flora, S-rich nodules were also recovered near a horizon OSL dated at 118 ± 13 ka comparable to the LIG thermal maximum. Results of this study provide new insights into the stratigraphy and climatic conditions of the LIG in the HBL but also help better understand the behavior and dynamics of the Laurentide Ice Sheet during the Late Pleistocene.

Investigation and modeling of odors release from membrane holes on daily overlay in a landfill and its impact on landfill odor control

In the present work, we studied the NH3 and H2S odor fluxes between the exposed working area and the HDPE covering film holes of the daily overlay in an actual landfill site with a daily operating area of 1600 m2 in Hangzhou, China. We showed that the odors were released from the membrane pores and the average concentrations of NH3 and H2S release reached 109.6 ± 56.6 and 86.0 ± 31.1 mg/m2/s, respectively. These concentrations are 43.8 and 57.3 times the exposed working surface. Furthermore, mathematical modeling based on the total amount of odor release revealed that there was a linear positive correlation between the total odor amount and the landfill operation area. However, the maximum number of film holes allowed on the covering layer has nothing to do with the working area and exposed working time, which is mainly determined by the HDPE film width in terms of ensuring the deodorizing effect of the covering operation. If the HDPE film with a width of more than 4 m is used, the number of film holes allowed within 100 m is more than 8. Therefore, in order to reduce the odor, the appropriate film width should be selected according to the actual operating conditions such as the mechanical operation level at the time of welding, the design of the landfill site, and the operational norms. This study explores the effect of film hole quantity of the daily cover in the landfill on the odor release from the landfill, which can provide an important reference for the design, operation, and decision-making of the daily cover operation of the sanitary landfill.