Oxidation Of Acid-volatile Sulfide Research Articles

Remediate black-odorous sediment by slow-release calcium nitrate: Migration, transformation and microbial succession

Calcium nitrate has been widely used in-situ remediation of black-odorous sediment, which microorganisms mainly utilized nitrate to redox substances through denitrification. However, this technique has the problem that the local nitrate concentration was too high to inhibit the activity of functional microorganisms, which affected the oxidation effect and caused the abnormal release of inorganic nitrogen from the sediment. The slow release of calcium nitrate by tube dosing can effectively solve this disadvantage. However, the specific layout of the dosing method needs further research. Therefore, a method of tube-dosing distribution points was proposed by explored the migration and transformation laws of N-S-Fe in the vertical and horizontal directions of the sediment and the changes in the microbial community structure after the fixed-point dosing of calcium nitrate in this study, which further optimized the calcium nitrate dosing process and provided a new dosing method and idea in practical application. Within one month, nitrate migrated and transformed vertically and horizontally, accompanied by the accumulation of nitrite, oxidation of acid volatile sulfide (AVS) and ferrous iron. Among them, within the nitrate migration distance of 0–6 cm (vertical) and 0–8 cm (horizontal), the removal rate of AVS reached 100% and ferrous iron was effectively oxidized. In addition, in the process of vertical and horizontal migration, bacteria closely related to sulfide and ferrous iron-driven denitrification, such as Thiobacillus, Sulfurimonas and Thioalkalispira, were found to be dominant. These results demonstrate that after exploring the vertical and horizontal migration and transformation laws of nitrate in different contaminated sediments remediated, the reasonable layout of dosing methods can be carried out in practical application.

Sustained-release nitrate combined with microbial fuel cell: A novel strategy for PAHs and odor removal from sediment

Nitrate addition is a biostimulation technique that can improve both the oxidation of acid volatile sulfide (AVS) through autotrophic denitrification and the biodegradation of polycyclic aromatic hydrocarbons (PAHs) via heterotrophic denitrification. However, during the remediation, parts of the dissolved nitrate in the sediment migrates from the sediment to the overlying water, leading to the loss of effective electron acceptor. To overcome this limitation, a combined approached was proposed, which involved nitrocellulose addition and a microbial fuel cell (MFC). Results indicated the nitrate could be slowly released and maintained at a higher concentration over long term. In the combined system, the removal efficiencies of PAHs and AVS were 71.56% and 89.76%, respectively. Furthermore, the voltage attained for the MFC-nitrocellulose treatment was maintained at 146.1 mV on Day 70, which was 5.37 times higher than that of the MFC-calcium nitrate treatment. Sediments with nitrocellulose resulted in lower levels of nitrate and ammonium in the overlying water. Metagenomic results revealed that the combined technology improved the expression of nitrogen-cycling genes. The introduction of MFC inhibited sulfide regeneration during incubation by suppressing the enzyme activity like EC4.4.1.2. The enhanced biostimulation provided potential for in-situ bioremediation utilizing MFC coupled with slow-released nitrate (i.e., nitrocellulose) treatment.

Coupling oxidation of acid volatile sulfide, ferrous iron, and ammonia nitrogen from black-odorous sediment via autotrophic denitrification-anammox by nitrate addition

The coupling removal of acid volatile sulfide (AVS), ferrous iron, and ammonia nitrogen has been applied for black-odorous sediment remediation. In this study, calcium nitrate with different N/(S + Fe) ratios (0.45, 0.90, 1.20 and 1.80) was added into black-odorous sediment in four systems named R1, R2, R3, and R4. Results showed that the removal rate of AVS was 76.40% in the R1, which was lower compared with rates in R2–R4 around 96.70%. The ferrous oxidation rate was approximately 87.00% in R2–R4, which was considerably higher than that in the R1 (24.62%). And the ammonia was reduced by 81.02%, 88.00%, 100%, and 57.18% in R1, R2, R3 and R4, respectively. During the reaction, nitrite accumulation was observed, indicating partial denitrification. Moreover, microbes related to autotrophic denitrification (e.g., genus Thiobacillus, Dok59, GOUTA19, Gallionella, with the highest abundance of 15.40%, 13.21%, 8.79%, 9.44%, respectively) were detected in all systems. Furthermore, the anammox bacteria Candidatus_Brocadia with the highest abundance of 3.44% and 4.00% in R2 and R3, respectively was also found. These findings confirmed that AVS, ferrous iron, and ammonia nitrogen could be simultaneously removed via autotrophic denitrification coupled with anammox in black-odorous sediment by nitrate addition.

Effects of nitrate dosing on the migration of reduced sulfur in black odorous river sediment and the influencing factors

At present, nitrates were widely used to remediate sulfur-rich sediment in black odorous rivers. However, the optimal nitrate dosage and influencing factors during remediation have not been fully investigated. In this study, various nitrate dosages and possible influencing factors were investigated for their efficiency in treating sulfur-rich sediment. The results indicated that acceptable remedial efficiency (the percentage of acid volatile sulfide (AVS) oxidation and the residual ammonium production) can be achieved when 1.6 times the theoretical nitrate dosage is used. Large amounts of AVS cannot be oxidized if too little nitrate is used and will regenerate after several days of remediation. Conversely, high concentrations of ammonium will form if too much nitrate is used. The results of this study indicated that a rapid AVS oxidation rate will be achieved in higher temperatures; no significant treatment efficiency was found when temperatures were in the range of 15–35 °C. Organic matter slowed the rate of nitrate reduction but did not affect its remedial efficiency for AVS oxidation in sediment. A high concentration of ferrous iron primarily influenced nitrate treatment efficiency in the oxidation of AVS in sediment, simultaneously causing the production of a high ammonium concentration. This study once again proved that microbial mediation of the autotrophic sulfide-driven denitrification dominates AVS oxidation in sediment. This study indicated that a universal nitrate dosage calculation equation should be established, and that factors such as ferrous iron concentration should be considered in future remediation of black odorous rivers.

Effect of autotrophic denitrification on nitrate migration in sulfide-rich marine sediments

This study aims to investigate how NO3 − reduction affects the migration of NO3 − in marine sediments and evaluate whether the overlying seawater would be contaminated by NO3 − injection for in situ bioremediation. The migration of NO3 − in sandy silt sediment with high acid volatile sulfide (AVS) content and in clayey silt sediment with relatively low AVS content was investigated through column experiments with 5 weeks of incubation. Results showed that NO3 − reduction through autotrophic denitrification contributed to 93.1 and 48.9 % of total NO3 − reduction in sandy silt and clayey silt sediments, respectively. In sandy silt sediment with high AVS content, NO3 − tended to migrate upwards through gas cavities formed during the movement of N2 gas produced by NO3 − reduction. Meanwhile, greater NO3 − consumption by AVS oxidation can effectively prevent the NO3 − release into seawater. In clayey silt sediment with relatively low AVS content, few gas cavities produced due to insignificant NO3 − reduction and high density of NO3 − solution made the downward NO3 − migration more significant. Without great NO3 − consumption, NO3 − from clayey silt sediment was found to be present in the seawater after 5 weeks of incubation. Autotrophic denitrification has a significant impact on NO3 − reduction in marine sediments. The reduction of NO3 − resulting from autotrophic denitrification can influence its preferential migration path in marine sediment and the possibility of its release into seawater.

Oxidation of acid-volatile sulfide in surface sediments increases the release and toxicity of copper to the benthic amphipod Melita plumulosa

Acid-volatile sulfides (AVS) are an important metal-binding phase in sediments. For sediments that contain an excess of AVS over simultaneously extracted metal (SEM) concentrations, acute or chronic effects should not result from the metals Cd, Cu, Ni, Pb and Zn. While AVS phases may exist in surface sediments, the exposure to dissolved oxygen may oxidize the AVS and release metals to more bioavailable forms. We investigated the role of oxidation of AVS, and specifically copper sulfide phases, in surface sediments, in the toxicity to juveniles of the epibenthic amphipod, Melita plumulosa. Sediments containing known amounts of copper sulfide were prepared either in situ by reacting dissolved copper with AVS that had formed in field sediments or created in sediments within the laboratory, or by addition of synthesised CuS to sediments. Regardless of the form of the copper sulfide, considerable oxidation of AVS occurred during the 10-d tests. Sediments that had a molar excess of AVS compared to SEM at the start of the tests, did not always have an excess at the end of the tests. Consistent with the AVS–SEM model, no toxicity was observed for sediments with an excess of AVS throughout the tests. However, the study highlights the need to carefully consider the changes in AVS concentrations during tests, and that measurements of AVS and SEM concentrations should carefully target the materials to which the organisms are being exposed throughout tests, which in the case of juvenile M. plumulosa is the top few mm of the sediments.

Effect of Resuspension on the Release of Heavy Metals and Water Chemistry in Anoxic and Oxic Sediments

AbstractTwo types of river sediments with contrasting characteristics (anoxic or oxic) were resuspended and the release of heavy metals and changes in water chemistry were investigated. During resuspension of the anoxic sediment, the dissolved oxygen (DO) concentration and redox potential of the water layer decreased abruptly within the first 1 min, followed by increases toward the end of the resuspension period. Heavy metals were released rapidly in the first 6 h, probably due to the oxidation of acid volatile sulfide (AVS) of the anoxic sediment, and then the aqueous phase concentrations of the heavy metals decreased due to resorption onto the sediment until the 12‐h point. During resuspension of the oxic sediment, the DO concentration and redox potential remained relatively constant in the oxic ranges. The heavy metals were released from the oxic sediment gradually during a 24‐h resuspension period. The temporal maximum concentrations of Ni, Cu, Zn, and Cd in the aqueous phases in both experiments frequently exceeded the USEPA water quality criteria or the water quality guidelines of Australia and New Zealand. This suggests that a resuspension event could bring about temporal water quality deterioration in the two sediment environments.

Effects of cyclic changes in pH and salinity on metals release from sediments

The effects of dynamic changes in pH and salinity on metal speciation and release are investigated with sediments posed in a simulated estuarine environment. The release of Zn, Cd, Mn, and Fe was studied using sediment from the Anacostia River (Washington, DC, USA) spiked with freshly precipitated amorphous cadmium sulfide to increase Cd content. The sediment was exposed to salt water (high pH, ionic strength) and freshwater (neutral pH, minimal ionic strength) continuously and alternately (to mimic tidal changes) in small microcosms over 100 d. At the conclusion of the experiments, the vertical profiles of acid volatile sulfide (AVS) and simultaneously extracted metals (SEM) as well as porewater metals and anion concentrations were characterized. Acid volatile sulfide oxidation at the sediment surface led to a commensurate increase in dissolved metal species and metal release that was strongly dependent on the changes in the overlying water characteristics. Total Cd release was substantially higher during exposure to salt water, although, as a result of complexation, predicted dissolved Cd(2+) concentration in the overlying water was higher during exposure to freshwater. Total Zn release was little changed during exposure to salt water and freshwater, although the predicted dissolved Zn(2+) concentration was much higher during freshwater exposures. No significant iron was released because of the rapid oxidation of ferrous iron (Fe(2+)) in aerobic surficial sediments and overlying water. The present study suggests that cyclic changes in pH and salinity in the overlying water can dramatically influence metal release from estuarine sediments.

Simulating the dynamics of sulfur species and zinc in wetland sediments

In situ measurements comparing vertical SO 4 2− profiles in vegetated and non-vegetated sediments showed that SO 4 2− concentrations in vegetated sediments increased significantly at the beginning of the growing season and then gradually decreased during the rest of the growing season. Throughout the growing season, SO 4 2− concentrations remained higher in the vegetated sediments than in the sediments without plants. The higher SO 4 2− concentrations in the vegetated sediments indicate that oxygen release from roots and evapotranspiration-induced advection by plants play an important role in the dynamics of sulfur species in sediments. Since the total pool of solid-phase sulfide is relatively large compared to the mass of SO 4 2− in the sediments, the gradual decrease of SO 4 2− concentrations may result from limitation of the solid-phase sulfide that is in direct contact with or very close to the roots and rhizomes. This would mean that the main pool of solid-phase sulfide and associated trace metals are not affected by the oxygen release from roots, and the associated trace metals will not become bioavailable during the growing season. A mathematical model was developed to gain a better understanding of how oxygen release from roots is linked to the dynamics of solid-phase sulfide, associated trace metals and dissolved SO 4 2− concentrations in sediments throughout the growing season. The model consists of one-dimensional mass balance equations formulated for the reactive transport of organic carbon, terminal electron acceptors and their corresponding reduced species in the sediments. It accounts for the combined effects of oxygen release by roots and evapotranspiration as well as physical and biological reactions, and includes formulations for the oxidative dissolution of solid species, such as FeS(s) and ZnS(s), as well as the formation of these species. Model simulations indicate that only 0.1% of the total solid-phase sulfide in the sediment is available to be oxidized by the oxygen released from roots. The oxidation of solid-phase sulfide associated with oxygen release from roots not only produces oxidized sulfur species (i.e. SO 4 2−, S 0), it also releases the associated metals to the sediment pore-water and perhaps the water column. Simulation results indicate that this oxidation of AVS (acid-volatile sulfide) does not result in the flux of trace metals into the water column.

Elemental sulfur in drain sediments associated with acid sulfate soils

This paper reports the abundance of elemental S in drain sediments associated with acid sulfate soils. The sediments exhibited near-neutral pH (5.97–7.27), high concentrations of pore-water Fe 2+ (1.37–15.9 mM) and abundant oxalate-extractable Fe (up to 4300 μmol g −1). Maximum acid-volatile sulfide (AVS) concentrations in each sediment profile were high (118–1019 μmol g −1), with AVS often exceeding pyrite-S. Elemental S occurred at concentrations of 13–396 μmol g −1, with the higher concentrations exceeding previous concentrations reported for other sedimentary systems. Up to 62% of reduced inorganic S near the sediment/water interface was present as elemental S, due to reaction between AVS and oxidants such as O 2 and Fe(III). Significant correlation ( r = 0.74; P < 0.05) between elemental S and oxalate-extractable Fe(III) is indicative of elemental S formation by in situ oxidation of AVS. The results indicate that AVS oxidation in near-surface sediments is dynamic in acidified coastal floodplain drains, causing elemental S to be a quantitatively important intermediate S fraction. Transformations of elemental S may therefore strongly influence water quality in ASS landscapes.

On the Vertical Distribution and Influencing Factors of Acid-Volatile Sulfide in the Sediments of Donghu Lake (Wuhan)

Lake Donghu(Wuhan), a subtropical shallow lake near the Yangze River, is polluted heavily by some sewage inputs. Based on total phosphorus (TP) and chlorophyll-a, Station I is defined as a hypertrophic lake, and Station II is defined as a eutrophic lake, and Station III is defined as mesotrophic lake. The main purposes of this paper are to describe the vertical distribution of acid volatile sulfide (AVS) in the sediments of three stations with different trophic levels in Lake Donghu, and to discuss the possible mechanisms underlining these patterns with emphasis on the possible effects of organic matter. The results indicate that AVS peak appeared in anoxic sediments in all three stations. Two patterns of AVS distribution were found. The AVS profiles in cores of Station I and II showed a maximum concentration at about 5-cm depth, and then a drop down at a lower level. On the contrary, the AVS profile in the cores of Station III showed AVS peak between 10 cm to 20 cm depths. There was closer relationship between OM and AVS in the sediment with high concentration of OM than with low concentration of OM, and AVS/OM ratio was in the order of Station I II III. This indicates that organic matter exerted great effects on the distribution of AVS in the sediment. The content of AVS in sediments is mainly affected by decompose of organic matter, deposition, dissolution and oxidation of AVS. High organic matter flux shifted AVS peak into the surface sediment, and narrowed the depth interval over which the accumulation of AVS became maximized at the more eutrophic Stations I and II. The convection-diffusion model of AVS reported by Fang et al was tested. The vertical distribution of AVS accorded with the model better in eutrophic lake with high concentration of OM than with low concentration of OM.

Effect of bioturbation on metal‐sulfide oxidation in surficial freshwater sediments

AbstractRecent studies have demonstrated the role of acid‐volatile sulfide (AVS) in controlling the bioavailability of several cationic metals in anoxic sediments. However, metal‐sulfide complexes can be relatively labile with respect to oxidation associated with factors such as seasonal changes in rates of oxidation/production of AVS. Another potentially important mechanism of AVS oxidation in surficial sediments is bioturbation. We used different densities of the burrowing oligochaete Lumbriculus variegatus in a series of laboratory experiments to evaluate the effect of bioturbation on oxidation of AVS and subsequent bioavailability of cadmium and zinc spiked into freshwater sediments. Metal bioavailability was determined directly by bioaccumulation in the test organisms and indirectly through analysis of interstitial (pore) water metal concentrations. In our studies, horizon‐specific sediment analyses were conducted to assess spatial differences in AVS and pore‐water metal concentrations specifically related to organism activity. Burrowing activity of the oligochaete significantly reduced AVS concentrations in surficial sediments in a density‐dependent manner and resulted in elevated interstitial water concentrations of cadmium but not zinc. Concentrations of cadmium in pore water from deeper horizons (below the zone of active burrowing) were consistently lower than those in the surficial sediments. The bioaccumulation of cadmium and zinc by L. variegatus was reflective of pore‐water concentrations of the two metals, i.e., there was significant accumulation of cadmium, but not zinc, by the oligochaetes. Overall, our results indicate that bioturbation can enhance the bioavailability of some cationic metals in surficial sediments, via oxidation of AVS, and demonstrate the importance of analyzing surficial sediments when assessing bioavailability of metals in sediments.

Chronic effect of cadmium in sediments on colonization by benthic marine organisms: An evaluation of the role of interstitial cadmium and acid‐volatile sulfide in biological availability

AbstractThe role of interstitial cadmium and acid‐volatile sulfide (AVS) in controlling the bioavailability of sediment‐associated metal was examined using the chronic saltwater benthic colonization test. Sediments were spiked to achieve nominal cadmium/ AVS molar ratios of 0.0 (control), 0.1, 0.8, and 3.0 in this 118‐d test. Oxidation of AVS in the surficial 2.4 cm within 2 to 4 weeks resulted in sulfide profiles similar to those occurring naturally in local sediments. In the nominal 0.1 cadmium/AVS treatment, measured simultaneously extracted metal (SEMcd) was always less than AVS. Interstitial cadmium concentrations (&lt;3‐10 μg/L) were less than those likely to cause biological effects. No significant biological effects were detected. In the nominal 0.8 cadmium/ AVS treatment, measured SEMcd commonly exceeded AVS in the surficial 2.4 cm of sediment. Interstitial cadmium concentrations (24‐157 μg/L) were of likely toxicological significance to highly sensitive species. Shifts in the presence or absence over all taxa, and fewer macrobenthic polychaetes (Mediomastus ambiseta, Streblospio benedicti, and Podarke obscurd) and unidentified meio‐faunal nematodes, were observed. In the nominal 3.0 cadmium/AVS treatment, concentrations of SEMcd were always greater than AVS throughout the sediment column. Interstitial cadmium ranged from 28,000 to 174,000 μg/L. In addition to the effects above, these sediments were colonized by fewer macrobenthic species, polychaete species, and harpacticoids; had lower densities of diatoms; lacked bivalve molluscs; and exhibited other impacts. Over all treatments, the observed biological responses were consistent with SEMcd/AVS ratios in surficial sediments and interstitial water cadmium concentrations.

Horizon-specific oxidation of acid volatile sulfide in relation to the toxicity of cadmium spiked into a freshwater sediment

The effects of oxidative processes on acid volatile sulfide (AVS) concentrations in various horizons of whole sediment cores were evaluated in relation to the toxicity of a metal (cadmium). An artificial system was used to “age” cadmium-spiked sediment samples under a constant flow of fresh Lake Superior water. Sediments from Pequaywan Lake, Minnesota (12 μmol AVS/g) were spiked to achieve (nominal) cadmium: AVS molar ratios of 0.02 (control), 0.2, 0.8, 1.2, and 3.0. At 0, 24, and 48 days post-spiking, sediment cores were removed from the aging system and tested for toxicity to the amphipod Hyalella azteca. At the same time, horizons from replicate sediment cores were prepared for analysis by freezing, and then cutting them into 10–20 mm increments. The sediment horizons were analyzed for AVS and simultaneously extracted cadmium concentrations, and pore water concentrations of cadmium. Relatively little oxidation of surficial AVS concentrations was observed, even at aging times up to 48 d. By 48 d, pore water concentrations of cadmium were slightly elevated at all spiking concentrations, but were increased greatly at cadmium:AVS ratios greater than one. Hyalella azteca mortality was generally predictable based on surficial cadmium:AVS ratios or pore water cadmium concentrations.

Distribution and isotopic composition of sulfur in lake sediments of northern Ontario

Sediments from unpolluted and highly polluted lakes in northern Ontario have been fractionated into acid volatile sulfide, HCl-soluble sulfur, elemental sulfur, pyrite sulfur, ester sulfate and carbon-bonded sulfur and the isotopic composition of each fraction determined. In general, reduced inorganic S constitutes 25–50% of the total S in the polluted surficial sediments, but is <20% in the unpolluted samples, with pyrite formation being a minor process of S diagenesis in lake sediment ecosystems. Organic S in the form of ester sulfate and carbon-bonded S predominates and both the C/S ratios and the isotopic data suggest that, in unpolluted lakes, plant detritus can be a major contributor of organic-S to the sediments. The depth profiles observed suggest that the more labile ester sulfate is diagenetically converted to the carbon-bonded form. For the polluted sediments from the Sudbury basin, the isotopic data suggest that (a) the elemental S is derived from the oxidation of acid volatile sulfide in the aerobic surficial sediments, and (b) the isotopically light reduced S species are incorporated into the organic material. S diagenesis in lake sediments generally results in the release of 34S to the overlying water. The suggestion is made that sulfate concentrations over 5 mg/1 accompanied by an enrichment of surficial sediments with isotopically different S may signal significant inputs of pollutant S into the lake and its basin.