Acid Volatile Sulfide Research Articles

Organic matter quantity and quality, metals availability and foraminiferal assemblages as environmental proxy applied to the Bizerte Lagoon (Tunisia)

This study analyzes the benthic trophic state of Bizerte Lagoon (Tunisia) based on the total organic matter and the bioavailability of biopolymeric carbon including proteins (PTN), carbohydrates (CHO), lipids (LIP), chlorophyll a, as well as bacteria counts. The overall simultaneously extracted metals (SEM), and acid volatile sulfides (AVS) as well as the SEM/AVS ratio indicative of the toxicity of the sediments also were analyzed aiming to study their impact in the dimension, composition and structure of both dead and living benthic foraminiferal assemblages.In the studied sites TOC content is relatively high and the PTN/CHO values indicate that they can be considered as meso-eutrophic environments. The CHO/TOC and C/N values suggest that the OM which accumulated on the sediments surface has mainly natural origin despite the introduction of municipal and industrial effluents in the lagoon and the large bacterial pool.The living assemblages of benthic foraminifera of Bizerte Lagoon are quite different to other Mediterranean transitional systems studied until now. They are composed of typical lagoonal species but also include several marine and opportunistic species including significant numbers of bolivinids, buliminids, Nonionella/Nonionoides spp. and Cassidulina/Globocassidulina spp. These assemblages seem to benefitfrom the physicochemical parameters and the sediment stability. They may however face environmental stress in the lagoon related to the AVS production as a result of the organic matter degradation and toxicity in some areas due to the available concentrations of metals. Nonetheless statistical results evidence that the structure and dimension of assemblages are being controlled mostly by OM quantity and quality related mainly to the availability of PTN, CHO and chlorophyll a. Results of this work support the importance of considering OM quantity and quality in studies of environmental impact in coastal systems.

Geochemical control processes and potential sediment toxicity in a mine-impacted lake.

Geochemical parameters and major ion concentrations from sediments of a freshwater lake in the town of Åtvidaberg, southeastern, Sweden, were used to identify the geochemical processes that control the water chemistry. The lake sediments are anoxic, characterized by reduced sulfur and sulfidic minerals. The hypothesis tested is that in sulfidic-anaerobic contaminated sediments, the presence of redox potential changes creates a favorable condition for sulfide oxidation, resulting in the release of potentially toxic metals. The acid volatile sulfide (AVS) contents ranged from 5.5 μmol/g to 16 μmol/g of dry sediment. Comparison of total mine tailing metals (∑mine tailing metals) with simultaneously extracted metals (SEM) in sediments indicates that up to 20% of the ∑mine tailing metals are bound to the solid phase as AVS. Consequently, the AVS and SEM analysis classified all sediment samples as potentially toxic in terms of heavy metal concentrations (i.e., SEM to AVS ratio distribution > 1). Evaluation of hydrogeochemical data suggests that calcite dissolution, iron (III) oxyhydroxysulfate mineral jarosite (H-jarosite) precipitation, hematite precipitation, and siderite precipitation are the most prevailing geochemical processes that control the geochemical interactions between the water column and sediment in a mine-impacted lake. The geochemical processes were verified and quantified using a chemical equilibrium modeling program, Visual MINTEQ, Ver 3.1, beta. The identified geochemical processes create an environment in which the characteristics of sulfate-rich waters and acidic-iron produce the geochemical conditions for acid mine drainage and mobilization of toxic metals.

Legacy impacts of acid sulfate soil runoff on mangrove sediments: Reactive iron accumulation, altered sulfur cycling and trace metal enrichment

The off-site impacts of iron-rich, acidic runoff from drained acid sulfate soils (ASS) on the geochemistry of estuarine sediments are relatively poorly constrained. In this study, we examine the geochemistry of intertidal zone mangrove sediments and porewaters from an estuarine tributary that received ~15–20years of acute ASS drainage, compared to adjacent control sites. Mixing of acidic, iron-rich ASS drainage waters with circumneutral pH estuarine waters drove precipitation of Fe(III) floc and has led to significant, localized accumulation of reactive-Fe species (FeR; Σ1M HCl and citrate-buffered dithionite extracts; up to 4200μmolg−1) as well as significantly elevated porewater Fe2+ (>1000μM) in ASS impacted sediments. X-ray diffraction indicates that goethite, lepidocrocite and ferrihydrite are important Fe(III) minerals in surficial sediments at ASS impacted sites. The abundant FeR is shifting the equilibrium of reduced inorganic sulfur (RIS) mineral-formation pathways towards accumulation of S(0) and acid volatile sulfide (AVS) species and is buffering porewater S(-II) to low concentrations. In contrast, RIS speciation at the control sites is dominated by pyrite (SCR) and porewater S(-II) is present. Some porewater metals (i.e. Al, Mn, Cu, Cr) are significantly elevated at sites proximal to the source of ASS drainage compared to control sites. Abundant FeR also provides a substrate for sorption and accumulation of metals and correspondingly there is significant relative enrichment of reactive metal fractions (1M HCl extractable) in sediments at the ASS impacted sites, with Al≈Mn≈U>Cu>Cr>Ni. This study demonstrates that ASS drainage, which causes accumulation of reactive Fe in mangrove environments, can substantially influence sediment biogeochemistry by altering reduced inorganic sulfur cycling and enhancing the availability of some trace metals.

Assessment of sediment quality based on acid-volatile sulfide and simultaneously extracted metals in heavily industrialized area of Asaluyeh, Persian Gulf: concentrations, spatial distributions, and sediment bioavailability/toxicity.

Sediment samples from the coastal area of Asaluyeh harbor were collected during autumn and spring 2015. The acid-volatile sulfide (AVS) and simultaneously extracted metals (SEMs) were measured to assess the sediment quality and potential ecological risks. The average concentrations (and relative standard deviation (RSD)) of AVS in the industrial sediments were 12.32μmol/g (36.91) and 6.34μmol/g (80.05) in autumn and spring, respectively, while in the urban area, these values were 0.44μmol/g (123.50) and 0.31μmol/g (160.0) in autumn and spring, respectively. The average concentrations of SEM (and RSD) in the industrial sediments were 15.02μmol/g (14.38) and 12.34μmol/g (20.65) in autumn and spring, respectively, while in the urban area, these values were 1.10μmol/g (43.03) and 1.06μmol/g (55.59) in autumn and spring, respectively. Zn was the predominant component (34.25-86.24%) of SEM, while the corresponding value for Cd, much more toxic ingredient, was less than 1%. Some of the coastal sediments in the harbor of Asaluyeh (20 and 47% in autumn and spring, respectively) had expected adverse biological effects based on the suggested criterion by United States Environmental Protection Agency (USEPA), while most stations (80 and 53% in autumn and spring, respectively) had uncertain adverse effects.

Development of a bioavailability-based risk assessment approach for nickel in freshwater sediments.

To assess nickel (Ni) toxicity and behavior in freshwater sediments, a large-scale laboratory and field sediment testing program was conducted. The program used an integrative testing strategy to generate scientifically based threshold values for Ni in sediments and to develop integrated equilibrium partitioning-based bioavailability models for assessing risks of Ni to benthic ecosystems. The sediment testing program was a multi-institutional collaboration that involved extensive laboratory testing, field validation of laboratory findings, characterization of Ni behavior in natural and laboratory conditions, and examination of solid phase Ni speciation in sediments. The laboratory testing initiative was conducted in 3 phases to satisfy the following objectives: 1) evaluate various methods for spiking sediments with Ni to optimize the relevance of sediment Ni exposures; 2) generate reliable ecotoxicity data by conducting standardized chronic ecotoxicity tests using 9 benthic species in sediments with low and high Ni binding capacity; and, 3) examine sediment bioavailability relationships by conducting chronic ecotoxicity testing in sediments that showed broad ranges of acid volatile sulfides, organic C, and Fe. A subset of 6 Ni-spiked sediments was deployed in the field to examine benthic colonization and community effects. The sediment testing program yielded a broad, high quality data set that was used to develop a Species Sensitivity Distribution for benthic organisms in various sediment types, a reasonable worst case predicted no-effect concentration for Ni in sediment (PNECsediment ), and predictive models for bioavailability and toxicity of Ni in freshwater sediments. A bioavailability-based approach was developed using the ecotoxicity data and bioavailability models generated through the research program. The tiered approach can be used to fulfill the outstanding obligations under the European Union (EU) Existing Substances Risk Assessment, EU Registration, Evaluation, Authorisation, and Regulation of Chemicals (REACH), and other global regulatory initiatives. Integr Environ Assess Manag 2016;12:735-746. © 2015 SETAC.

Changes in soil organic carbon fractions after remediation of a coastal floodplain soil

Coastal floodplain soils and wetland sediments can store large amounts of soil organic carbon (SOC). These environments are also commonly underlain by sulfidic sediments which can oxidise to form coastal acid sulfate soils (CASS) and contain high concentrations of acidity and trace metals. CASS are found on every continent globally except Antarctica. When sulfidic sediments are oxidised, scalds can form, which are large bare patches without vegetation. However, SOC stocks and fractions have not been quantified in these coastal floodplain environments. We studied the changes in soil geochemistry and SOC stocks and fractions three years after remediation of a CASS scald. Remediation treatments included raising water levels, and addition of either lime (LO) or lime and mulch (LM) relative to a control (C) site. We found SOC concentrations in the remediated sites (LO and LM) were more than double than that found at site C, reflected in the higher SOC stocks to a depth of 1.6 m (426 Mg C/ha, 478 Mg C/ha and 473 Mg C/ha at sites C, LO and LM, respectively). The particulate organic C (POC) fraction was higher at sites LO and LM due to increased vegetation and biomass inputs, compared to site C. Reformation of acid volatile sulfide (AVS) occurred throughout the profile at site LM, whereas only limited AVS reformation occurred at sites LO and C. Higher AVS at site LM may be linked to the additional source of organic matter provided by the mulch. POC can also potentially contribute to decreasing acidity as a labile SOC source for Fe3+ and SO42− reduction. Therefore, coastal floodplains and wetlands are a large store of SOC and can potentially increase SOC following remediation due to i) reduced decomposition rates with higher water levels and waterlogging, and ii) high C inputs due to rapid revegetation of scalded areas and high rates of biomass production. These results highlight the importance of maintaining vegetation cover in coastal floodplains and wetlands for sequestering SOC.

Chemical speciation of sulfur and metals in biogas reactors – Implications for cobalt and nickel bio-uptake processes

This article deals with the interrelationship between overall chemical speciation of S, Fe, Co, and Ni in relation to metals bio-uptake processes in continuous stirred tank biogas reactors (CSTBR). To address this topic, laboratory CSTBRs digesting sulfur(S)-rich stillage, as well as full-scale CSTBRs treating sewage sludge and various combinations of organic wastes, termed co-digestion, were targeted. Sulfur speciation was evaluated using acid volatile sulfide extraction and X-ray absorption spectroscopy. Metal speciation was evaluated by chemical fractionation, kinetic and thermodynamic analyses. Relative Fe to S content is identified as a critical factor for chemical speciation and bio-uptake of metals. In reactors treating sewage sludge, quantity of Fe exceeds that of S, inducing Fe-dominated conditions, while sulfide dominates in laboratory and co-digestion reactors due to an excess of S over Fe. Under sulfide-dominated conditions, metals availability for microorganisms is restricted due to formation of metal-sulfide precipitates. However, aqueous concentrations of different Co and Ni species were shown to be sufficient to support metal acquisition by microorganisms under sulfidic conditions. Concentrations of free metal ions and labile metal complexes in aqueous phase, which directly participate in bio-uptake processes, are higher under Fe-dominated conditions. This in turn enhances metal adsorption on cell surfaces and bio-uptake rates.

Macroinvertebrate responses to nickel in multisystem exposures.

Metals introduced to sediments undergo a variety of complexation and partitioning changes that affect metal bioavailability. Using simultaneously extracted metal (SEM)/acid volatile sulfide (AVS) and organic carbon (f(OC)) models, the authors examined nickel (Ni) toxicity and bioavailability in 2 field studies (using streamside mesocosm and in situ colonization) and 1 laboratory study. The streamside mesocosm experiments indicated that benthic communities (Ephemeroptera, abundance, and taxa richness) responded negatively to increasing SEM(Ni) /AVS and (SEM(Ni) -AVS)/f(OC) models. In the in situ colonization study, taxa richness, abundance, and Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa decreased with increasing SEM(Ni) and SEM(Ni)/AVS values. Nickel-spiked sediments were tested in the laboratory with indigenous field-collected mayflies (Anthopotamus verticis, Isonychia spp., and Stenonema spp) and a beetle (Psephenus herricki), and with laboratory-cultured Hyalella azteca and Chironomus dilutus. The amphipod H. azteca was the most sensitive organism tested, and the mayflies Anthopotamus verticis and Stenonema spp. were the most sensitive indigenous organisms to Ni-spiked sediments. These studies help discern which factors are important in determining Ni toxicity and bioavailability at the individual, population, and community levels.

Potential risk assessment of heavy metals in sediments during the denitrification process enhanced by calcium nitrate addition: Effect of AVS residual

Calcium nitrate addition has been proved to be a effective technology for sediment odor control, however, when sulfide was oxidized, metals those combined to sulfide might potentially threatened the aquatic ecosystem. In this work, for the purpose of assessing the effect of acid volatile sulfide (AVS) residual on ecological risk of heavy metals (Cu, Cd, Pb and Zn) in anoxic sediments during the denitrification, limited calcium nitrate (20g/kgdw) was added into sediments in microcosm systems, and then was exhausted within two weeks, along with 95.0% AVS removed. During the treatment, simultaneously extracted metal (SEM) to AVS ratio increased with sulfide removal, but remained lower than 1 because of the residual of AVS. Furthermore, geoaccumulation index (Igeo), sediment quality guidelines (SQGs) and risk assessment code (RAC) all indicated that the risk level of all metals in treated sediments showed no significant change compared to that in initial sediments. It suggested that certain content of AVS residual could keep ecological risk of heavy metals at a low level during the treatment with calcium nitrate addition. However, limitations of each assessment index were observed as well. Igeo and SQGs were found to be unsuitable for temporal dynamic evaluation, but useful for identifying which metal got higher pollution level and risk level, and thus deserved more concerns. In addition, RAC was appropriate for Cu assessment rather than Zn, Cd and Pb evaluation, while AVS–SEM method was suitable for Zn, Cd and Pb evaluation instead of Cu assessment. Thus, all these indexes should be taken into account as a whole when used.

Induced metal redistribution and bioavailability enhancement in contaminated river sediment during in situ biogeochemical remediation.

In situ sediment remediation using Ca(NO3)2 or CaO2 for odor mitigation and acid volatile sulfide (AVS) and organic pollutant (such as TPH and PAHs) removal was reported in many studies and fieldwork. Yet, the associated effects on metal mobilization and potential distortion in bioavailability were not well documented. In this study, contaminated river sediment was treated by Ca(NO3)2 and CaO2 in bench studies. Through the investigation of AVS removal, organic matter removal, the changes in sediment oxidation-reduction potential (ORP), microbial activity, and other indigenous parameters, the effects on metal bioavailability, bioaccessibility, and fraction redistribution in sediment were evaluated. The major mechanisms for sediment treated by Ca(NO3)2 and CaO2 are biostimulation with indigenous denitrifying bacteria and chemical oxidation, respectively. After applying Ca(NO3)2 and CaO2, the decreases of metal concentrations in the treated sediment were insignificant within a 35-day incubation period. However, the [SEMtot-AVS]/f OC increased near to the effective boundary of toxicity (100 μmol g(-1) organic carbon (OC)), indicating that both bioavailability and bioaccessibility of metals (Cu, Zn, and Ni) to benthic organisms are enhanced after remediation. Metals were found redistributed from relatively stable fractions (oxidizable and residual fractions) to weakly bound fractions (exchangeable and reducible fractions), and the results are in line with the enhanced metal bioavailability. Compared with Ca(NO3)2, CaO2 led to higher enhancement in metal bioavailability and bioaccessibility, and more significant metal redistribution, probably due to its stronger chemical reactive capacity to AVS and sediment organic matter. The reactions in CaO2-treated sediment would probably shift from physicochemical to biochemical heterotrophic oxidation for sediment organic matter degradation. Therefore, further investigation on the long-term metal redistribution and associated mobility as well as bioavailability is recommended.

The relationship of benthic community metrics to pyrethroids, metals, and sediment characteristics in Cache Slough, California

ABSTRACTA bioassessment multiple stressor study was conducted at 12 sites in Cache Slough, California during the Spring and Fall of 2012, 2013 and 2014. Specific study goals were to: (1) collect and identify benthic macroinvertebrates and develop a suite of benthic metrics; (2) measure total organic carbon (TOC), grain size, bulk metals, simultaneously extracted metals (SEM) and acid volatile sulfides (AVS), and 8 pyrethroids in sediment; (3) measure basic water quality parameters; and, (4) use univariate and stepwise multiple regressions and canonical correlation analysis to determine the relationship between various benthic metrics (i.e., taxa richness, abundance) and TOC, grain size, metals (bulk metals and SEM/AVS) and pyrethroids using the 3-year database. Five benthic metrics showed statistically significant relationships with environmental variables. Taxonomic Richness, a metric that decreases with stress, tended to be greater in less organic-rich, coarser sediments and the apparent relationships with toxicants such as pyrethroids or metals were diminished when these conditions are taken into account. The % Amphipod metric, which has a variable response to environmental stressors, showed a direct relationship with arsenic, an inverse relationship with chromium and an inverse relationship with % silt. The % Corbicula metric, which has a variable response to environmental stressors, was directly correlated with cypermethrin and nickel. Therefore, it appears that Corbicula tends to be associated with more contaminated sediments in Cache Slough. The metric % Collectors/Filterers & Collectors/Gatherers, a metric that increases in stressed environments, was reported to increase in sediments with higher arsenic concentrations. This relationship makes ecological sense because this metric should increase with an increase in arsenic concentrations. The benthic metric Abundance, a metric that decreases with stress, was reported to be inversely correlated with % TOC and % silt. The abundance of benthic communities increases in coarser, less organic rich sediments. In general, relatively few statistically significant relationships were observed between the various combinations of benthic metrics and environmental variables. Benthic communities in Cache Slough appear to be more closely associated with sediment characteristics and with metals concentrations than with the pyrethroid concentrations.

Influence of the phenols on the biogeochemical behavior of cadmium in the mangrove sediment.

Phenols exert a great influence on the dynamic process of Cd in the soil-plant interface. We investigated the influence of phenols on the biogeochemical behavior of cadmium in the rhizosphere of Avicennia marina (Forsk) Vierh. All combinations of four levels of cadmium (0, 1, 2 and 4 mg/kg DW) and two levels of phenol (0 and 15 mg/kg DW) were included in the experimental design. We found that phenols facilitated increasing concentrations of exchangeable cadmium (Ex-Cd), acid volatile sulfide (AVS) and reactive solid-phase Fe (II) in sediments, and iron in plants, but inhibited Cd accumulation in iron plaque and roots. The concentrations of AVS and reactive solid-phase Fe (II) were significantly positively correlated with Cd treatment. As for the biogeochemical behavior of Cd in mangrove sediments, this research revealed that phenols facilitated activation and mobility of Cd. They disturbed the "source-sink" balance of Cd and turned it into a "source", whilst decreasing Cd absorption in A. marina. Additionally, phenols facilitated iron absorption in the plant and alleviated the Fe limit for mangrove plant growth.

Trace metals partitioning among different sedimentary mineral phases and the deposit-feeding polychaete Armandia brevis

Trace metals (Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn) were determined in two operationally defined fractions (HCl and pyrite) in sediments from Ensenada and El Sauzal harbors (Mexico). The HCl fraction had significantly higher metal concentrations relative to the pyrite fraction in both harbors, underlining the weak tendency of most trace metals to associate with pyrite. Exceptionally, Cu was highly pyritized, with degrees of trace metal pyritization (DTMP) >80% in both harbors. Dissolved Fe flux measurements combined with solid phase Fe sulfide data indicated that 98mt of Fe are precipitated as iron sulfides every year in Ensenada Harbor. These Fe sulfides (and associated trace metals) will remain preserved in the sediments, unless they are perturbed by dredging or sediment resuspension. Calculations indicate that dredging activities could export to the open ocean 0.20±0.13 to (0.30±0.56)×103mt of Cd and Cu, respectively, creating a potential threat to marine benthic organisms. Degrees of pyritization (DOP) values in Ensenada and El Sauzal harbors were relatively low (<25%) while degrees of sulfidization (DOS) were high (~50%) because of the contribution of acid volatile sulfide. DOP values correlated with DTMP values (p≤0.001), indicating that metals are gradually incorporated into pyrite as this mineral is formed. Significant correlations were also found between DTMP values and −log(Ksp(MeS)/Ksp(pyr)) for both harbors, indicating that incorporation of trace metals into the pyrite phase is a function of the solubility product of the corresponding metal sulfide. The order in which elements were pyritized in both harbors was Zn≈Mn<Fe<Cd≈Pb<Ni≈Co<<Cu. Lastly, a strong correlation (r2=0.87, p<0.01) was found between average reactive trace metal concentrations and metal concentrations measured in Armandia brevis (a deposit-feeding Opheliid polychaete), suggesting that these labile sedimentary metals are preferentially accumulated by the polychaete, making it a useful biomonitor of sedimentary metal exposure.

Accumulation of sulfidic sediments in a channelised inland river system, southern Australia

Accumulation of sulfidic sediments in freshwater environments is a relatively recent phenomenon and an emerging environmental issue. In the present study, benthic sediments along short (~250m) reaches of an inland freshwater river in south-eastern Australia were examined to determine the abundance and vertical distribution of fine-grained organic sulfidic sediments, identified by acid volatile sulfide (AVS) and chromium-reducible sulfur (SCR) contents. Sulfidic sediments (up to 404mmolkg–1 SCR) preferentially accumulated in zones immediately overlying coarse sandy bed material. Conversely, where bed material was clay or silt dominated, comparatively limited sulfidic sediment had accumulated (where AVS and SCR were not detected). This suggests that the hydraulic conductivity of the underlying bed material could play a role in the formation of sulfidic sediments and that the overlying water column is not the sole source of SO42–. Evidence suggests that accumulation of sulfidic materials occurred preferentially downstream of channel obstructions, such as submerged logs or in scour pools. However, sediment accumulation was not limited to lower-energy parts of the channel, as would be expected for fine-grained organic sediments. Evidence of reworking, burial or sulfide formation at depth highlights the dynamism of the system and its differences to many coastal systems where these sediments are commonly found.

Accumulation of trace metals in sediments in a Mediterranean Lagoon: Usefulness of metal sediment fractionation and elutriate toxicity assessment

The authors investigated sediment quality in Bizerte Lagoon (Tunisia) focusing on geochemical characteristics, metal sediment fractionation and elutriate toxicity assessment. Nickel, Cu, Zn, Pb, Cr and Cd partitioning in sediments was studied; accumulation and bioavailability were elucidated using enrichment factors, sequential extractions, redox potential, acid volatile sulfide and biotest procedures in toxicity evaluation. Results revealed an accumulation for Pb and Zn, reaching 99 and 460 mg kg−1 respectively. In addition, the acid volatile sulfide values were high in both eastern and western lagoon areas, thus affecting metal availability. Mean enrichment factor values for Pb and Zn were 4.8 and 4.9, respectively, with these elements as the main contributors to the lagoon's moderate enrichment level. Toxicity levels were influenced by accumulation of Zn in different surface sediment areas. Core sediments were investigated in areas with the highest metal concentrations; metal fractionation and biotest confirmed that Zn contributes to sediment toxicity.

Environmental Quality Assessment of Bizerte Lagoon (Tunisia) Using Living Foraminifera Assemblages and a Multiproxy Approach.

This study investigated the environmental quality of the Bizerte Lagoon (Tunisia) through an integrated approach that combined environmental, biogeochemical, and living benthic foraminiferal analyses. Specifically, we analyzed the physicochemical parameters of the water and sediment. The textural, mineralogical, and geochemical characteristics of the sediment, including total organic carbon, total nitrogen, simultaneously extracted metals (SEM), acid volatile sulfides (AVS), chlorophyll a, CaCO3, and changes in bacterial populations and carbon isotopes were measured. The SEM/AVS values indicated the presence of relatively high concentrations of toxic metals in only some areas. Foraminiferal assemblages were dominated by species such as A. parkinsoniana (20–91%), Bolivina striatula (<40%), Hopkinsina atlantica (<17%), and Bolivina ordinaria (<15%) that cannot be considered typical of impacted coastal lagoons both in Mediterranean and northeast Atlantic regions. The results of this work suggest that Bizerte Lagoon is a unique setting. This lagoon is populated by typical marine species that invaded this ecosystem, attracted not only by the prevailing favorable environmental conditions but also by the abundance and quality of food. The results indicate that the metal pollution found in some areas have a negative impact on the assemblages of foraminifera. At present, however, this negative impact is not highly alarming.

Survival, Reproduction and Growth of the Marine Amphipod, Leptocheirus plumulosus, Following Laboratory Exposure to Copper-Spiked Sediment.

Leptocheirus plumulosus was exposed for 28days to Cu-spiked sediment at mean concentrations ranging from 44.4 to 605mg Cu/kg dry sediment in a sediment/water test system designed to simulate natural conditions. The NOEC (no observed effect concentration)-LOEC (lowest observed effect concentration) range for the most sensitive endpoint of growth was 199-414mg Cu/kg sediment. An IC50 for reproduction was estimated at 187mg Cu/kg sediment. Mean Cu concentrations in pore water (PW) where significant effects were observed were 25.8 and 59.0µg/L, while their respective concentrations in overlying water (OW) were 22.1 and 28.0µg Cu/L. Copper concentrations were ≤19.1 and <16.6µg/L in PW and OW, respectively, at lower exposures where effects were not evident. Concentrations of Cu in marine sediment lower than sediment quality guidelines based on geochemical factors of acid volatile sulfide, organic carbon content (f OC), and sediment grain size (i.e., silt+clay) would appear not to result in adverse effects toward L. plumulosus.

울산 태화강 하구역 퇴적물의 유기물 및 미량금속 오염도 평가

Grain size, the content of ignition loss (IL), and the concentrations of chemical oxygen demand (COD), acid volatile sulfide (AVS), and trace metals (Fe, Mn, Cu, Pb, Zn, Cd, Cr, As, and Hg) in surface sediments from the Taehwa River estuary, Ulsan, were measured to evaluate pollution levels and potential ecological risks of organic matter and trace metals in estuarine sediment. The mean grain size (Mz) of sediments in the study region ranged from <TEX>$-0.8-7.7{\varphi}$</TEX> (mean <TEX>$2.8{\pm}2.4{\varphi}$</TEX>). Surface sediments in the upstream region of the Taehwa River were mainly composed of coarse sediments compared to the downstream region. The concentrations of IL, COD, AVS and trace metals in the sediment were much higher at downstream sites of Myeongchon Bridge in the vicinity of industrial complexes than at upstream sites of those in the vicinity of the residential areas due to the anthropogenic input of organic matter and trace metals by industrial activities. On the basis of several geochemical assessment techniques [sediment quality guidelines (SQGs), enrichment factor (EF), geoaccumulation index (<TEX>$I_{geo}$</TEX>), pollution load index (PLI) and ecological risk index (ERI)], the surfaces sediments in the study region are not highly polluted for trace metals, except for As. However, the higher concentrations in downstream study regions of the Taehwa River could impact benthic organisms including shellfish (i.e. Manila clam) in sediments.

곰소만 바지락(Ruditapes phillippinarum) 양식장 주변 퇴적물 내 유기물과 미량금속 분포특성

【Organic matter and trace metals were investigated in surface sediments of Gomso Bay, where there is dense Manila clam Ruditapes philippinarum farming activity, to evaluate contamination of sediments in intertidal shellfish farming area. We measured mean grain size (Mz), chemical oxygen demand (COD), ignition loss (IL), acid volatile sulfide (AVS), total organic carbon (TOC), and total nitrogen (TN), and trace metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb and Zn) in intertidal and sublittoral sediments. The intertidal sediments were mainly composed of coarser sediments (sand, silty sand, and sandy silt), with Mz values ranging from 2.61 to 4.79 O. Mz and the content of organic matter in sediments were lower in the intertidal zone than in the sublittoral zone. The mean metal concentrations in surface sediments decreased in the order Fe > Mn > Zn > Cr > Pb > Cu > As > Cd > Hg. The metal concentrations in surface sediments showed a significant positive correlation with Mz and organic matter content, indicating that metal concentrations in the surface sediments of Gomso Bay are controlled by Mz and organic matter. The concentrations of organic matter and trace metals in the study region were lower than or similar to those in other intertidal zones in western coast and much lower than those reported in other shellfish farming areas in Korea. Our results suggest that intertidal Manila clam farming sediments from Gomso Bay are not contaminated by organic matter and trace metals.】

Characterization of H2S removal and microbial community in landfill cover soils.

H2S is a source of odors at landfills and poses a threat to the surrounding environment and public health. In this work, compared with a usual landfill cover soil (LCS), H2S removal and biotransformation were characterized in waste biocover soil (WBS), an alternative landfill cover material. With the input of landfill gas (LFG), the gas concentrations of CH4, CO2, O2, and H2S, microbial community and activity in landfill covers changed with time. Compared with LCS, lower CH4 and H2S concentrations were detected in the WBS. The potential sulfur-oxidizing rate and sulfate-reducing rate as well as the contents of acid-volatile sulfide, SO4(2-), and total sulfur in the WBS and LCS were all increased with the input of LFG. After exposure to LFG for 35 days, the sulfur-oxidizing rate of the bottom layer of the WBS reached 82.5 μmol g dry weight (d.w.)(-1) day(-1), which was 4.3-5.4 times of that of LCS. H2S-S was mainly deposited in the soil covers, while it escaped from landfills to the atmosphere. The adsorption, absorption, and biotransformation of H2S could lead to the decrease in the pH values of landfill covers; especially, in the LCS with low pH buffer capacity, the pH value of the bottom layer dropped to below 4. Pyrosequencing of 16S ribosomal RNA (rRNA) gene showed that the known sulfur-metabolizing bacteria Ochrobactrum, Paracoccus, Comamonas, Pseudomonas, and Acinetobacter dominated in the WBS and LCS. Among them, Comamonas and Acinetobacter might play an important role in the metabolism of H2S in the WBS. These findings are helpful to understand sulfur bioconversion process in landfill covers and to develop techniques for controlling odor pollution at landfills.