Total Sulfide Research Articles

Hypoxic conditions in stormwater retention ponds: potential for hydrogen sulfide emission

ABSTRACTImproper design and maintenance of stormwater ponds (SWPs) may lead to hypoxic conditions, poor water quality and the production of hydrogen sulfide (H2S). The objective of this study is to develop a comprehensive understanding of hypoxic conditions of SWPs, with a focus on the potential for H2S production and emission. This study was conducted at two retention SWPs in Ottawa, Canada; a problematic pond with the propensity for H2S emission and a reference pond that did not demonstrate H2S emission. The investigation illustrated a significant impact of low dissolved oxygen (DO) concentrations, hypoxic conditions, on the concentration of total sulfides in the water column. Both ponds were shown to periodically experience hypoxic conditions at depth, especially during summer periods with less precipitation and across longer periods of winter, ice-covered conditions. The problem pond, however, was shown to experience lower DO and longer hypoxic conditions than the reference pond in both non-ice-covered and ice-covered conditions due to greater depth and a longer hydraulic retention time. Hypoxic conditions were initiated at the deepest locations in the problem pond and subsequently were spread across the entirety of the pond under winter, ice-covered conditions. Algal biomass (Chlorophyll-a) and soluble biochemical oxygen demand concentrations were shown to not likely be significant factors in the development of hypoxia in the H2S-generating pond. Algal blooms of colonial Chrysophyceae, Synura, a known mixotroph, were observed during ice-covered conditions in the problem pond possibly due to stress-coping mechanisms of algae.

Biological removal of gaseous sulfur dioxide through the reduction to hydrogen sulfide by means of Desulfovibrio desulfuricans

The biological removal of gaseous sulfur dioxide using the sulfate reducing bacteria Desulfovibrio desulfuricans is studied. Laboratory-scale bioreactors were designed to generate sulfur dioxide in them through a chemical reaction. To evaluate the biological reduction, three kinetics (in triplicate) were taken in batch mode with loads of 15, 20 and 25 mmol of SO2 generated in the gas phase per liter of culture medium in the liquid phase. Lactate was used as substrate (electron donor) and carbon source. The experimental results showed a 100% SO2 reduction for all the evaluated loads. The tests lasted 24, 72 and 192 h, with lower, intermediate and higher loads, respectively. The total sulfide (S2−) produced varied between 75 and 126 mg for the tests with lower and higher load, respectively. These amounts were composed of a fraction in the aqueous phase (287 and 533 mg of S2−/L) and another in the gas phase (0.9 × 108 and 2.7 × 108 μg H2S/m3). The mass ratio between product formation (sulfide) and electron donor consumption (expressed as COD) ranged from 81% to 90% of the theoretical value (0.67 mg of sulfide produced per mg of COD consumed).

Synergistic Effect of Sulfide and Ammonia on Anaerobic Digestion of Chicken Manure

The effect of the sulfur load on anaerobic digestion of chicken manure (CM) was investigated in a laboratory scale anaerobic mono-digester at high total ammonia nitrogen (TAN) concentrations. The digester was operated for 268 days by increasing the organic loading rate from 0.5 to 2.5 kg-VS/m3/day and the total Kjeldahl nitrogen up to 5050 mg/l. The CH4 yield of 0.36 ± 0.02 m3/kg-VS was achieved at 2.5 kg-VS/m3/day of loading rate without any inhibition. The results showed that, anaerobic mono-digestion of chicken manure was applicable with the acclimation of microbial consortium to high TAN concentrations. However, when the sulfur content of the CM fed to the digester increased suddenly by coincidence, the CH4 yield decreased about 25% from 0.36 ± 0.02 to 0.27 ± 0.03 m3/kg-VS. As a result, the acetic acid concentration increased from 130 to 1700 mg/l showing that the acetate consuming methanogens were detrimentally affected from TAN and total sulfide concentrations above 4000 and 100 mg/l, respectively.

Modeling Spatio-vertical Distribution of Sulfate and Total Sulfide along the Mangrove Intertidal Zone

Modeling Spatio-vertical Distribution of Sulfate and Total Sulfide along the Mangrove Intertidal Zone

Role of thiosulfate in hydrogen sulfide-dependent redox signaling in endothelial cells.

Recent reports have revealed that hydrogen sulfide (H2S) exerts critical actions to promote cardiovascular homeostasis and health. Thiosulfate is one of the products formed during oxidative H2S metabolism, and thiosulfate has been used extensively and safely to treat calcific uremic arteriopathy in dialysis patients. Yet despite its significance, fundamental questions regarding how thiosulfate and H2S interact during redox signaling remain unanswered. In the present study, we examined the effect of exogenous thiosulfate on hypoxia-induced H2S metabolite bioavailability in human umbilical vein endothelial cells (HUVECs). Under hypoxic conditions, we observed a decrease of GSH and GSSG levels in HUVECs at 0.5 and 4 h as well as decreased free H2S and acid-labile sulfide and increased bound sulfide at all time points. Treatment with exogenous thiosulfate significantly decreased the ratio of GSH/GSSG to total sulfide of HUVECs under 0.5 h of hypoxia but significantly increased this ratio in HUVECs under 4 h of hypoxia. These responses reveal that thiosulfate has different effects at low and high doses and under different O2 tensions. In addition, treatment with thiosulfate also diminished VEGF-induced cystathionine-γ-lyase expression and reduced VEGF-induced HUVEC proliferation under both normoxic and hypoxic conditions. These results indicate that thiosulfate can modulate H2S metabolites and signaling under various culture conditions that impact angiogenic activity. Thus, thiosulfate may serve as a unique sulfide donor to modulate endothelial responses under pathophysiological conditions involving angiogenesis.NEW & NOTEWORTHY This report provides new evidence that different levels of exogenous thiosulfate dynamically change discrete sulfide biochemical metabolite bioavailability in endothelial cells under normoxia or hypoxia, acting in a slow manner to modulate sulfide metabolites. Moreover, our findings also reveal that thiosulfate surprisingly inhibits VEGF-dependent endothelial cell proliferation associated with a reduction in cystathionine-γ-lyase protein levels.

Sulfide effects on the anaerobic metabolism of polyphosphate-accumulating organisms

Sulfate rich wastewaters can be generated from industry, use of seawater in urban environments, or by saline water infiltration into the sewerage. Under anaerobic conditions sulfate can be converted to sulfide, which may affect micro-organisms performing biological nutrient removal. The objective of this study was to evaluate the effect of sulfide on the activity of polyphosphate-accumulating organisms (PAO) in the anaerobic stage of the enhanced biological phosphorus removal process (EBPR). In this regard, a highly enriched culture of PAO was exposed in short-term activity tests to a range of sulfide concentrations at different operational pH values. The PAO activity was mainly affected by un-dissociated H2S. The specific acetate uptake rate was inhibited by 50% at around 60mg H2S.L−1. With increasing H2S concentrations, higher phosphate release rate to acetate uptake rate ratios were observed, possibly due to increased energy requirements for cell detoxification. Mathematical expressions were developed, which satisfactorily described the sulfide effects on the acetate uptake rate and phosphate release rate. The results show that, dependent on the pH, EBPR might be negatively affected by total sulfide concentrations exceeding 275mg SO4.L−1 at pH 6.5 or 1200mg SO4.L−1 at pH 7.8mg SO4.L−1 or when freshwater is partially replaced by seawater more than 45% (pH 7.8) or 10% (pH 6.5) used as secondary quality water. The findings of this study imply that sulfide, which is commonly found in different type of wastewaters, affects the anaerobic metabolism of PAO and may play an important role in the process performance of treatment plants treating wastewaters with high sulfide content.

A model of phototrophic sulfide oxidation in a stratified estuary

AbstractSulfide accumulated as a result of microbial sulfate reduction in sediments and the bottom waters of stratified systems can be re‐oxidized via an array of biotic and abiotic reactions. A one‐dimensional diffusion‐reaction model was developed and applied to 4 yr of physical and chemical data from the stratified water column of the Chesapeake Bay in order to quantify the impact of different sulfide oxidation processes at the redox interface during slack tide. This dataset and the model simulations highlight short‐term and interannual variation in the physical structure and the distribution of key redox species (O2, H2S, S0, Fe2+, Mn2+, FeOOH, MnO2) throughout the water column. The model evaluates links between oxygen, sulfur, iron and manganese cycling, and includes the novel consideration of sulfide oxidation by phototrophic sulfide oxidizing bacteria (PSOB), which are a common component of the Bay. Model simulations demonstrate that phototrophic sulfide oxidation can account for up to 58% of total sulfide oxidation, depending upon the depth of the oxic/anoxic interface. The results of this study yield an approach to parameterizing PSOB activity, and quantify the variable role that PSOB play in sulfide oxidation in the Chesapeake Bay as redox conditions in the water column change, which has applications for both modern and ancient environments.

Recovered Gases and Bacteria from the <i>Clostridium</i> Genus as Ecological Condition Indicators of Bottom Sediments of the Eastern Donbass Small Rivers

The results of determination of methane, total hydrogen sulfide and sulfite reducing clostridia in bottom sediments of small rivers and reservoirs of the Eastern Donbass are presented. The horizontal and vertical distribution of levels of reduced gases in bottom sediments is analyzed. The ecological condition of the bottom sediments was estimated by the clostridia titer and the methane index. The ranking of the ecological condition of bottom sediments according to the content of total hydrogen sulfide in them is performed. The relationship between pH and Eh values, methane and hydrogen sulfide concentrations and the number of sulfite reducing clostridia was studied, which allowed to discover new sides of the metabolic cycle of reduced gases in bottom sediments of freshwater ecosystems located in the zone of anthropogenic influence. The researches carried out allow to draw a conclusion about significant prolonged anthropogenic impact, mainly of domestic and industrial wastewater on water objects of the Eastern Donbass.

Bacterial community composition shifts in sediments influenced by fish feeds

This study investigated the influence of fish feed deposition on the microbial community of sediments in a coastal lake. Microcosms were designed to simulate the addition of fish feeds to the sediment, and physicochemical factors as well as composition of microbial assemblages were analysed. Although total organic carbon and total organic nitrogen did not significantly increase, redox potential and total sulphides showed a transition of sediment environments into anaerobic condition due to the addition of fish feeds. The bacterial community composition shifted with fish feed deposition as revealed by the band profiles of denaturing gradient gel electrophoresis, Sørensen's similarity indices and cell numbers of sulphate-reducing bacteria. Occurrence of anaerobic bacteria (sulphate and nitrate reducers) and disappearance of strictly aerobic bacteria were observed with fish feed inputs. The results clarify the succession of the microbial flora and suggest negative impact of uneaten fish feeds on the microbial community in sediment and resultant environmental deterioration of fish-farming areas.

Bacterial and archeal community composition in hot springs from Indo-Burma region, North-east India.

Bacterial and archaeal diversity of two alkaline Indian hot springs, Jakrem (Meghalaya) and Yumthang (Sikkim), were studied. Thirteen major bacterial phyla were identified of which Firmicutes, Chloroflexi and Thermi were dominant in Jakrem and Proteobacteria in Yumthang. The dominant genera were Clostridium, Chloroflexus and Meiothermus at Jakrem (water temperature 46 °C, pH 9) and Thiobacillus, Sulfuritalea at Yumthang (water temperature 39 °C, pH 8) hot springs. The four Euryarchaeota taxa that were observed in both the hot springs were Methanoculleus, Methanosaeta, Methanosarcina and Methanocorposculum. Elstera litoralis, Thiovirga sp., Turneriella sp. were observed for the first time in association with hot springs along with Tepidibacter sp., Ignavibacterium sp., Teribacillus sp. and Dechloromonas sp. Individual bacterial phyla were found to be specifically correlated with certain physico-chemical factors such as temperature, dissolved SiO2, elemental S, total sulphide, calcium concentrations in hot spring water. Bacterial reads involved in sulfur cycle were identified in both16S rRNA gene library and sulfur metabolism may play key physiological functions in this hot spring. Members within Desulfobacterales and Thermodesulfovibrionaceae were identified and hypothesized their role in regulating sulfur cycle. The presence of many taxonomically unsolved sequences in the 16S rRNA gene tag datasets from these hot springs could be a sign of novel microbe richness in these less known hot water bodies of Northeastern India.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0284-y) contains supplementary material, which is available to authorized users.

Evaluation of biogeochemical reactivity of fresh and weathered contaminated dredged sediments

Metal mobility in contaminated marine sediments is largely controlled by low-soluble sulfides. In dredged sediments exposed to air and water, geochemical and microbial-mediated processes may enhance the weathering and leaching of hazardous contaminants, especially trace metals. The objective of the present study was to thoroughly characterize and assess the biogeochemical reactivity of marine-dredged sediments. Two samples of dredged sediments, one stored (to preserve anoxic conditions) and another exposed to the air, were assessed in the perspective of their long-term management. Biogeochemical reactivity was evaluated, especially by a qualitative assessment of aerobic iron- and sulfur-oxidizing bacteria activity. Despite the high content of total sulfides (2 to 3.5 wt.% S), the acid-volatile fraction was low (4.3 × 10−3 vs. 9.4 × 10−5 g S kg−1 in raw and weathered sediments, respectively), as an indication of the high degree of crystallinity of sulfide minerals present in samples. The raw sediment was reactive, particularly to aerobic bacteria that decreased the pH from 7.0 to 4.2, for neutrophilic sulfur-oxidizing bacteria, and from 4.5 to 2.5, for acidophilic iron-oxidizing, within only 18 days. Even though only neutrophilic sulfur-oxidizing bacteria seem reactive in the aged sediment, they countered the major buffering effect due to the high amount of carbonates. Important differences in the temporal evolution of pH and Eh of the raw and aged sediments support these results. Neutrophilic sulfur-oxidizing bacteria showed to be the most reactive in both sediments. Finally, despite the sharp pH decrease over time, acidophilic bacteria activity does not seem to be particularly enhanced.

Geochemical characterization of two distinctive systems with evidence of chemosynthetic activity, explored at the SE Pacific margin off Chile (46°S and 33°S)

This study presents the geochemical composition of superficial sediment under oxic and suboxic bottom water conditions along the Chilean continental margin (SE Pacific), where evidence for benthic chemosynthetic activity associated with diffuse seeping of chemically reduced fluids has been reported. The exploration was carried out at: (1) the Chilean Triple Junction (CTJ), at a water depth of ∼2900m, with the additional indication of hydrothermal activity near a methane-rich cold-seep area (46°S) (German et al., 2010); and (2) the El Quisco methane seep site (EQSS), at ∼340mwater depth (33°S) (Melo et al., 2007; Krylova et al., 2014). While the deeper CTJ is located within an oxic environment (dissolved oxygen in the bottom waters: 164μM), the shallower EQSS lies within a suboxic environment (dissolved oxygen in bottom water: 23μM), located within the lower limit of the SE Pacific oxygen minimum zone (OMZ).Pore water from short cores was analyzed for dissolved major, minor, and trace elements (Cl, Na, Mg, K, Ca, Sr, Si, B, P, Ba, Pb, Mn, Fe, Cd, U, and Mo), δ13DIC, sulfide, sulfate, and methane. The solid sediment fraction was likewise analyzed for total organic carbon (TOC), metals, and redox potential. Elevated sediment temperatures were found in superficial sediments (5–13°C) at the CTJ site, which could be due to warm fluids associated with the proximity of the ridge, where hydrothermal vents may occur. Reduced fluids were also present here, indicated by higher Mn fluxes toward the water column even in oxidized sediments (RPD>8cm), which contrasted with the lower fluxes in reduced sediments of the EQSS site (RPD∼2cm). 13C-depleted DIC, anomalously low pore water Cl (∼15ppb), and low concentrations of other major elements may be the result of dilution by fluid seeping and precipitation of major elements, producing authigenic enrichment (Ca, Mg, Sr). The fluid could also: (a) be diluted by pure water produced during methane hydrate dissociation, as observed in other cold-seep areas; and (b) correspond to clay mineral dehydration, as reported in plate subduction systems. The reducing conditions established at the CTJ conduct the Cd enrichment at a similar magnitude of that seen at the shallower suboxic site (EQSS). Evidence of chimney or vent fauna was not observed. At the EQSS, higher TOC and total sulfide contents were consistent with enhanced deposition of organic matter and reducing conditions developed in the OMZ, favoring the authigenic enrichment of Cd, U and Pb. The geochemical evidence, based only on methane concentrations and δ13DIC, is insufficient to establish the presence of methane seeps, as previously reported.

Determination of Sulfide and Total Sulfur in Ore by Wavelength-Dispersive X-ray Fluorescence

ABSTRACTThis paper describes the determination of total sulfur and sulfide in ore by X-ray fluorescence. The X-ray emission spectra of sulfur were measured by a wavelength-dispersive spectrometer. The samples were prepared as pressed powder pellets on boric acid substrates. The SKα1,2 line was used to determine total sulfur. The ratio between sulfide and total sulfur was measured by the ratio of satellite SKβ′ and SKβ1,3 line intensities. The total relative standard deviation (SD) of the measurements and preparation repeatability was less than 2%. Sample preparation was contributed to the error of the analysis. To determine total sulfur, the calibration curve was obtained from the samples of certified reference materials of gold-bearing sulfide-containing ore. The accuracy was verified by comparison with a gravimetric method. The relative SD was 6% for sulfur concentrations from 1 to 8 wt%. The calibration curve was defined using pure reagents to determine sulfide. The ore was analyzed by a gravimetric procedure with a relative SD of 6.5% for the sulfide concentration from 1 to 6 wt%.

Physicochemical Characteristics of River Water Downstream of a Large Tropical Hydroelectric Dam

Water quality in the downstream river of a hydroelectric dam may be affected by the structural design and operation. To date, little is known about the water quality downstream of the largest dam in Malaysia, the Bakun hydroelectric dam. Therefore, the objective of the study was to determine the water quality downstream of the dam when the spillway was closed and when it was opened. Results of the study indicate that the dam plays a significant role in regulating the water quality downstream of it. When the spillway was closed, pH and oxygen were lower in the river where DO was below 5 mg/L. When the spillway was opened, the water quality improved in terms of oxygen content (>8.0 mg/L), total sulphide (TS), and chemical oxygen demand (COD) but deteriorated in terms of five-day biochemical oxygen demand (BOD5), total ammonia nitrogen (TAN), and total phosphorus (TP). Additionally, the intensity of the impacts, particularly BOD5, COD, and TAN, shows a declining trend as distance from the dam increases. This study shows that impacts on the water quality extend to a distance of 32 km from the dam particularly turbidity and DO and opening the spillway changes the water quality significantly.

Immediate results of photodynamic therapy for the treatment of halitosis in adolescents: a randomized, controlled, clinical trial.

Light with or without chemical agents has been used to induce therapeutic and antimicrobial effects. With photodynamic therapy, the antimicrobial effect is confined to areas covered by a photosensitive dye and irradiated with light. The aim of the present study was to evaluate the effect of photodynamic therapy for the treatment of halitosis in adolescents through the analysis of volatile sulfur compounds, especially sulfide. A controlled, clinical trial was conducted with 45 adolescents randomly allocated to three groups: group 1, photodynamic therapy administered to the dorsum of the tongue; group 2, treatment with a tongue scraper; and group 3, treatment with a tongue scraper combined with photodynamic therapy. The diagnosis of halitosis was performed using gas chromatography before and after treatment. Comparisons were made using the Kruskal-Wallis test followed by the Student-Newman-Keuls test, with the level of significance set at 5% (p < 0.05). After treatment, a statistically significant reduction in halitosis was found in all groups (p < 0.001). The greatest reduction in total sulfides (median = 0) occurred with the combination of tongue scraper and photodynamic therapy. The present study describes a novel option for the treatment of halitosis in adolescents with an immediate effect that does not involve the mechanical aggression of the lingual papillae that occurs with conventional treatment. Photodynamic Therapy in Adolescents Halitosis ( https://clinicaltrials.gov/ct2/show/NCT02007993?term=NCT02007993&rank=1 )Number: NCT02007993FUNDING:FAPESPNumber: 2013/13032-8.

Geochemistry of two shallow CO2 seeps in Shikine Island (Japan) and their potential for ocean acidification research

Shallow CO2 seeps, where CO2 gas is venting underwater, offer great potential for studies into the effects of ocean acidification at the ecosystem level. To our knowledge, only two tropical system and two temperate systems of such seeps have been described worldwide. Here we describe two new temperate systems: the Mikama Bay and Ashitsuke sites, located on Shikine Island, Japan. The Mikama Bay site is located in a shallow bay. Investigation of the gas and water chemistry showed that the gas contained 98% CO2 and up to 90 ppm H2S. Total alkalinity was constant in time and space with an average of 2265±10 μ mol kg−1. Mapping of Eh and pH showed that the low pH zones were the largest when currents were moderate. Under moderate currents, Eh values were globally higher and total sulfides concentration lower, supporting that a longer residence time of the bay water allow the oxidation of the sulfides to sulfates. Zones suitable for acidification studies: with a pH lower than 8.0, low saturation state of calcite and aragonite, and non-detectable sulfide concentration, can be defined a few meters from the main venting zone. The second site, Ashitsuke, is located in the inter-tidal zone on a shore composed of boulders. Several areas showed reduced pH sometimes restricted to a few meters and up to 20 m long along the shoreline. Temperature was higher in some of the reduced pH zones suggesting the presence of hot springs in addition to vents. This paper also highlights the need for discovering additional CO2 seeps, which by their nature often lack comparable replicates and can be confounded by factors other than CO2. In this regard, Japan offers great potential as it is home to numerous active volcanoes, representing potential venting sites in climates ranging from tropical to sub-polar.

Abstract 453: Hydrogen Sulfide Increases Endothelial Permeability through Sulfane Sulfur Modification of Occludin

Objective: Hydrogen sulfide (H2S) is an endogenous signaling molecule which exists in three biological pools, namely free H2S, sulfane sulfur and acid labile sulfur. H2S also regulates protein function by protein sulfuration. Fine tuning endothelial permeability is crucial for vascular functions. Therefore, we sought to determine how sulfane sulfur and sulfuration of cell junction proteins alters endothelial permeability. Methods: Endothelial permeability was evaluated by albumin leakage or transendothelial electrical resistance (TEER) in transwell inserts. Exogenous H2S was studied by treating human umbilical vein endothelial cells (HUVECs) with H2S donors including sodium sulfide (Na2S), diallyl trisulfide (DATS). To investigate the effect of endogenous H2S, endothelial cells were isolated from aorta (MAECs) of wild type and CSE knockout mice. Biological pools of H2S were measured using monobromobimane followed by detection of sulfide-dibimane with reverse phase HPLC. Protein sulfhydration is determined by 2-methylsulfonyl benzothiazole (MSBT)/cyanoacetate tag-switch assay. Results: DATS treatment elevated sulfane sulfur and induced rapid albumin leakage through HUVEC monolayer. Comparatively, Na2S increased permeability only at later time points and to a lesser extent. Total sulfide and sulfane sulfur were reduced in CSE deficient MAECs. Moreover, MAECs lacking CSE showed enhanced barrier function compared to wild-type MAECs, characterized by decreased albumin leakage and increased of TEER. The tag-switch assay showed increased sulfuration of occludin in HUVECs. In conclusion, H2S bioavailability regulates endothelial solute permeability.

Sulphur Species Corrosivity in Refinery Feed Stock

High temperature sulphide corrosion and equipment failures have been reported in several crude and condensate processing facilities of petroleum refineries. Affected materials were carbon and low alloy steels operated in temperatures ranging from 200 to 300°C.These failures were attributed to specific sulphur species and were not anticipated by corrosion prediction tools used for their material selection. The corrosion mechanisms of these species are not fully understood. This paper presents Takreer Research Centre (TRC) research work for isolating the active sulphur species responsible for the corrosion. Two condensate samples were first analysed for total sulphur, hydrogen sulphide (H2S), Mercaptans (RSH) and other impurities. Using Gas Chromatograph with Sulphur Chemilumenesence Detector (SCD), it was possible to identify Mercaptans and sulphides from the process samples. Laboratory corrosivity testing of condensate sample using carbon steel and low alloy steel coupons at 275°C indicated that the corrosion rate was mainly related to the Mercaptans species within the Total Sulphur. The results concluded that specific dissociation temperature of respective Mercaptans is a useful tool in predicting the possibility and extent of corrosion and its vulnerable process loop.

Determination of total cyanides and sulfides in wastewater using ion chromatography coupled with ultraviolet photo-dissociation/gas-membrane diffusion

An automated system for the determination of total cyanides and sulfides in wastewater has been developed using flow injection, ultraviolet (UV) photo-dissociation, gas-membrane diffusion, column trapping, ion chromatography separation and pulsed amperometric detection. When the sample was mixed with sulfuric acid and hypophosphorous acid medium containing the appropriate amount of sulfamic acid, ascorbic acid, EDTA and citric acid, metal-cyanide complexes such as Fe (CN)3-(6) can be photo-dissociated by 312 nm UV light, which results in hydrogen cyanide ( HCN) and similarly, sulfides release hydrogen sulfide (H2S). These products were diffused through a 0.45 µm hydrophobic porous polypropylene membrane and were then absorbed in the dilute NaOH solution, concentrated with a Metrosep A PCC 1 HC/4.0 column, separated on an IonPac AS7 column, and finally detected by the pulsed amperometric detector with Ag electrode. The total cyanides and sulfides were good linear in the range of 0.5-1,000 µg/L with correlation coefficients of 0.998 9 and 0.999 7 respectively. The recoveries were 93%-102% and the limits of detection were 0.5 µg/L for total cyanides and 1.0 µg/L for sulfides under the conditions of the sample volume of 100 µL and the signal to noise ratio of 5. The sample throughput of the system was six samples per hour. The results from this new method have been compared with the ones obtained with the standard method, which shows a good agreement.

A survey on characteristics of leachate pond in an offshore municipal solid waste disposal site

Leachate from a landfill is collected and flowed in leachate accumulation pond, and sent to treatment facility. However, leachate in the pond can be a source of complaints from residents due to off coloration or odor, particularly near heavily populated urban areas. In this study, for the purpose of appropriate control of leachate pond, pond water and sediment were sampled in an offshore municipal solid waste disposal site 2 years after the disposal site was closed, and analyzed some parameters to estimate their properties. The pond water had high alkalinity due to the disposal of incineration residues, and EC and CODMn were also high. On the other hand, Cr, Mn, Fe, Cu, Zn, Cd, and Pb did not exceed the Japanese effluent water standards. Total sulfide was detected from all sediment samples during the sampling period, and values in the summer were slightly higher than at other times. To investigate the stabilization of targeted disposal site, the relationships among cumulative liquid/solid ratio (L/S) with pH and Cl− elution after closing the site were examined. Both parameters showed a direct relationship with cumulative L/S ratio, which can be anticipated to continue increasing in the future.