Sedimentation and sulfate reduction under a mussel culture

The sedimentation and dissimilatory sulfate reduction under a blue-mussel culture were quantified in order to gain information on the environmental impact of intense mussel farming. The sedimentation rate (3 g C·m^-2·d^-1) under a culture is nearly three times higher than at a nearby reference station. A build-up of sediment rich in organic material and sulfide takes place under the mussels. At 15°C the sulfate reduction rate was 30.5 mmol SO ₌ ⁴ ·m^-2·^-1 in the upper 10 cm of the mussel sediment. The increase in sedimentation under a mussel culture and the consequent effects should be considered when establishing mussel farms.     

Partitioning of Cs-137 Between Sediment and Water From the Black Sea

Abstract

As part of a joint USA/USSR Environmental Agreement to determine the distribution and concentration of Chernobyl radioactivity in the northwest Black Sea area, the sediment from eight stations was collected and analyzed to assess the ability of this material to adsorb radiocaesium. Batch tests were conducted in which Cs-137 tracer was added to mixtures of sediment and bottom water, with contact solutions ranging from 85 Bq ml^?1 to 1,760 Bq ml^?1. This work was done in an argon atmosphere at 9.5°C, which is the average temperature of the sediment. Isotherms were linear for all cores and distribution ratios (R_D) calculated from the slopes of the isotherms ranged from 660 to 1,660 ml g^?1. These isotherms fit a simplified Freundlich isotherm. Correlations of R_D to a number of sediment parameters describing texture and mineralogy were determined. A close relationship was observed between R_D for caesium and the percentage of illite contained in the samples.     

武汉严东湖近代沉积物中总氮、总磷与生物硅沉积及营养演化的动态过程

选择武汉近郊一中型浅水湖泊——严东湖为研究对象,对其进行了2个柱状沉积物的总氮、总磷、生物硅含量测试。结果表明：严东湖表层沉积物中总氮、生物硅含量总体均有所上升,而总磷近代含量有所下降。近代以来,硅藻的生长消耗了水体大量的硅与磷,表现为生物硅含量的显著上升,严东湖的营养程度有所上升。硅藻的生长与沉积影响到湖泊的沉积系统与过程,使营养盐比例与结构发生了变化,导致严东湖水体出现硅限制。     

Assessment of total and organic vanadium levels and their bioaccumulation in edible sea cucumbers: tissues distribution,inter-species-specific,locational differences and seasonal variations

The objective of this study is to investigate the levels, inter-species-specific, locational differences and seasonal variations of vanadium in sea cucumbers and to validate further several potential factors controlling the distribution of metals in sea cucumbers. Vanadium levels were evaluated in samples of edible sea cucumbers and were demonstrated exhibit differences in different seasons, species and sampling sites. High vanadium concentrations were measured in the sea cucumbers, and all of the vanadium detected was in an organic form. Mean vanadium concentrations were considerably higher in the blood (sea cucumber) than in the other studied tissues. The highest concentration of vanadium (2.56 μg g⁻¹), as well as a higher degree of organic vanadium (85.5 %), was observed in the Holothuria scabra samples compared with all other samples. Vanadium levels in Apostichopus japonicus from Bohai Bay and Yellow Sea have marked seasonal variations. Average values of 1.09 μg g⁻¹ of total vanadium and 0.79 μg g⁻¹ of organic vanadium were obtained in various species of sea cucumbers. Significant positive correlations between vanadium in the seawater and V _org in the sea cucumber (r = 81.67 %, p = 0.00), as well as between vanadium in the sediment and V _org in the sea cucumber (r = 77.98 %, p = 0.00), were observed. Vanadium concentrations depend on the seasons (salinity, temperature), species, sampling sites and seawater environment (seawater, sediment). Given the adverse toxicological effects of inorganic vanadium and positive roles in controlling the development of diabetes in humans, a regular monitoring programme of vanadium content in edible sea cucumbers can be recommended.

     

Denitrification in bottom sediment near oil production facilities off the Louisiana Gulf Coast

There is little information on denitrification in Gulf of Mexico bottom sediment. Potential denitrification rates in surface sediment were measured along transects legs extending 0–800 m from two offshore oil production platforms. The average potential denitrification ranged from approximately 50 mg N m^?2 d^?1 in surface sediment near the platforms to 15 mg N m^?2 d^?1 in sediment 800 m from the platforms. Measured denitrification rates were correlated to a higher organic matter content in sediment nearer the platforms. This research examined only a small component of nitrogen processing in Gulf of Mexico sediment. Additional research should examine the effect of nitrogen loading and temporal and spatial variability on denitrification rate.     

Distribution and mortality of diapause eggs from calanoid copepods in relation to sedimentation regimes

Distribution, abundance and age of diapause eggs from three species of calanoid copepods (in particular from Acartia spp. most likely Acartia tonsa, and Centropages hamatus and less numerous from Temora longicornis) were recorded in sediment profiles by enumerating hatched nauplii from incubated sediment samples. Phytoplankton pigments and ²¹⁰Pb and ¹³⁷Cs analyses indicated that the sedimentation regimes were different between two southern and two northern stations of the island Funen, Denmark. Significant variations in vertical distribution, abundance and mortality of diapause eggs were found between the stations. Dating of the sediment cores suggested a ~70-year maximum age of viable eggs on the northernmost stations, and ~28 year at the southernmost stations. The eggs exhibited a significantly higher mortality rate at the southernmost stations compared with the northernmost, 0.35–0.53 year⁻¹ vs. 0.07–0.08 year⁻¹ with no systematic pattern among species. The differences in abundance, mortality and age of the diapause eggs are suggested to be due to the sediment characteristics in which they are buried.     

Rates of nitrification,distribution of nitrifying bacteria,and nitrate fluxes in different types of sediment from Danish waters

Nitrification rates, measured in different sediment types from Danish waters, are in the range of 0.3 to 1.4 mmol NO ₃ ^- m^-2 d^-1. There is no signification between sandy and muddy sediments, nor between shallow and deeper stations. The extent of nitrification is probably limited to the zone of oxygen penetration, 1.5 to 5.5 mm. There are, however, nitrifying bacteria located in the anoxic sediment layers. There relative numbers were found by measuring the nitrification potential of the sediment. These potential rates (22°C) can also be used to calculate actual rates of nitrification, by adjusting to in situ temperature and oxygen penetration. These calculated rates agree with the actual measured rates of nitrification for a wide range of sediment types and may be used for the estimation of actual nitrification rates. Nitrate flux out from the sediment/water interface is in the range of 0 to 0.7 mmol NO ₃ ^- m^-2 d^-1. There is no correlation between concentration gradients of nitrate across the sediment/water interface and the measured flux of nitrate. Approximately 50% of nitrate production is released to the water column. The remainder (0 to 0.35 mmol N m^-2 d^-1) may have been denitrified.     

Experimental study on the control of black smoke pollution from the ceramic kilns based on the mechanism of the surfactant and coagulant

Aiming at the characteristics of carbon black, a new method of controlling the black smoke from the industrial coal-burning ceramic kilns by wetting was brought forward. The carbon black in the flue of coal-burning ceramic kiln was collected for the experiments, and its physical and chemical properties were studied in detail. In order to change the sedimentation and wettability state of the carbon black, the complex solution of the coagulant and surfactant was applied. After a series of orthogonal experiments, the complex solutions with better effects were chosen. Then, the sedimentation percentage of carbon black treated by the selected complex solutions was measured. The optimized complex solutions included Na₂SO₄ (100 mmol/L), sodium dodecyl benzenesulfonate (SDBS) (1.2 mmol/L) and polyacrylamide (PAM) (40 mg/L). After carbon black was absorbed, the complex solutions were clear and colorless. The complex solutions can be recycled, and the sedimentation percentage of carbon black is 94%.     

Interrelationships between sulfate reducing and methane producing bacteria in coastal sediments with intense sulfide production

Coastal sediments receiving different amounts of organic carbon through sedimentation were investigated with respect to sulfate reduction and methanogenic activity. Sampling was carried out at sediment temperatures of 7° and 15°C. Sulfate-reducing and methanogenic bacteria were found at all depths. Sulfate reduction decreased with depth and the highest sulfide concentrations were found a few centimeters below the sediment surface, up to 15 mM at 15°C and pH 7.1. In the same segments a maximum in the methane concentration was also found, 0.91 mM. The high sulfide concentration inhibited the methane formation from acetate but not from carbon dioxide. In the organic rich sediment sulfate reduction was limited by the diffusion of SO ₄ ⁺ into the sediment and methane production from acetate by sulfide diffusion out of the sediment. When electron acceptor concentration limits sulfate reduction, thermodynamic calculations show that the utilization of electron donors more reduced than acetate is favored. In the sediment with the high carbon-input, acetate predominated at 15°C whereas in the low carbon-input sediment hardly any short chain organic acids were detected. The possibility of a shift in sulfate reduction from acetate oxidation to acetate production is discussed.     

Effect of algal bloom deposition on sediment respiration and fluxes

Using sediment cores collected in November 1989 from Aarhus Bight, Denmark, the fluxes of O₂, CO₂ (total CO₂), NH ₄ ⁺ , NO ₃ ^– +NO ₂ ^– and DON (dissolved organic nitrogen) across the sediment-water interface were followed for 20 d in an experimental continous flow system. On day 7, phytoplankton was added to the sediment surface, to see the result of simulated algal bloom sedimentation. Benthic O₂ consumption and CO₂ efflux, 38 to 41 mmol O₂ m^-2 d^-1 and 25 to 30 mmol CO₂ m^-2 d^-1, respectively, immediately increased by 39% and 100% after the algal addition, but gradually declined to the orginal level. Fluxes of NH ₄ ⁺ (1.0 to 1.2 mmol m^-2 d^-1) and DON (0.3 to 0.9 mmol m^-2 d^-1) increased due to the organic substrate addition. NH ₄ ⁺ and NO ₃ ^– flux changed direction, becoming an efflux and influx, respectively, for a few days and a large amount of DON (max. rate 4.0 mmol m^-2 d^-1) was immediately produced either by bacterial hydrolytic activity or from autolysis of the algae. DON was the most significant nitrogen component in pore water and in terms of N-flux from sediment. A temporary stimulation of anaerobic respiration processes (sulfate reduction and denitrification) and a decrease in nitrification were indicated. After the effect of the organic addition had declined, the fluxes gradually reverted to the original rates. The halflife of the added algal material, of which 20 to 30% was very labile, was estimated to be 2 to 3 wk.     

N:P stoichiometry and transparent exopolymeric particles buffer ecological impacts of nutrients in the Ganga River: a mesocosm study

We investigated the possible drivers of the N:P stoichiometric shift and its relationship with micro-algal production of transparent exopolymeric particles (TEP) along a 35?km gradient of the Ganga River. The objective was to evaluate if the trade-off between N:P stoichiometry and production of TEP helps in maintaining water quality of the river. Mesocosm experiments were conducted to examine N:P-TEP linkages and its role in turbidity removal. In situ measurements did not show Si to be a limiting nutrient (N:Si?Aulacosira granulata and Fragilaria intermedia. Settling efficiency, turbidity removal and sedimentation of TEP, biogenic silica (BSi) and biomass all increased with decreasing N:P ratio proportionately to the amount of TEP produced in the mesocosm. The study demonstrates that trade-off between N:P stoichiometry and the production of TEP generates feedback to buffer the ecological impacts of nutrient pollution.     

Effect of selenium on mercury methylation in facultative lake sediments

The effect of selenium (Na₂SeO₃) on the methylation of mercury (HgCl₂) in facultative sediment was studied. The results showed that small amount of selenium (0.25 μg/g) added to the sediment could significantly reduce the net methylation rate of mercury. The more the selenium was added, the higher the inhibition effect was. These results made the addition of selenium to the aquatic systems more practical and safe as a way to alleviate mercury accumulation in fish. Additionally, higher temperature was favorable to the net methylation of mercury, and high concentration of methylmercury emerged earlier.     

Carbon isotopic and biochemical fingerprints of sedimentary organic matter in lower Narmada and Tapi rivers,north-west coast of India

Sources of organic matter (OM) in lower Narmada and Tapi river-estuaries were examined using organic carbon to nitrogen ratio (C_org/N), stable carbon isotope ratio (δ¹³C_org) and lignin phenol biomarkers. The signature of lower C_org (av. 0.50%) and higher δ¹³C_org (av. –20.3‰) in Narmada and, higher C_org (av. 0.85%) and lower δ¹³C_org (av. –22.8‰) in Tapi highlight the difference in OM characteristics of both systems, nevertheless they flow adjacent to each other. The OM in Tapi was predominated by fresh plant tissues, as indicated by higher Λ8?=?1.2–3.2?mg/100?mg C_org, lower Ad/Al_v?=?0.22–0.46 and lower LPVI?=?17–23. The plant OM present in the sediments of Narmada was previously degraded and mixed with soil. The OM contribution from algae was restricted to estuarine stations in both the rivers, which was ～50% in Narmada and ～35% in Tapi. The contribution of OM from fresh vascular plant was higher (20% to 63%) in Tapi than Narmada (2% to 35%). This study illustrated the benefits of using lignin phenols along with C_org/N and δ¹³C_org to identify the potential OM sources in two large river–estuary systems of India, which highlighted the complex interaction of natural and anthropogenic processes acted on the terrestrial OM compositions.     

Sediment load and timing of sedimentation affect spore establishment in Macrocystis pyrifera and Undaria pinnatifida

Although the frequency and magnitude of sedimentation often varies across coastal landscapes creating patches with different mean sediment loads, duration of sedimentation and rates of sediment resuspension, few studies have documented the emergent effects of spatio-temporal variability in sedimentation. Here, we conducted two laboratory experiments to evaluate such effects on the establishment of Macrocystis pyrifera and Undaria pinnatifida spores. In the first experiment, spore establishment was significantly affected by sediment load (the effective dose required for a 40 % reduction in establishment ranged between 16 and 60 mg sediment l^?1) and sediment regime (relative sedimentation occurring before spore settlement, ~3 times more sediment was required for 20 % reduction in spore establishment when sedimentation occurred after spore settlement). The second experiment demonstrated that the effects of sediment depended on sediment load (spore establishment was 2–4 times greater when sediment load was 200 mg l^?1 relative to 400 mg l^?1), variability in sedimentation (spore establishment was 1.36 times greater with variable than fixed sediment loads), repeated pulses of sedimentation (pulsed sedimentation decreased spore establishment by 59–91 % relative to a single sedimentation event) and timing of sedimentation relative to spore settlement (sedimentation before spore settlement decreased establishment by 51–95 % relative to sedimentation after spore settlement). These results have important implications for ecologists and resource managers attempting to predict the consequences of sedimentation, suggesting that it is not only important to consider sediment load, but also fine-scale temporal variability in sedimentation relative to key life-history events of the impacted organisms.     

Impact of the polychaete Capitella sp. I on microbial activity in an organic-rich marine sediment contaminated with the polycyclic aromatic hydrocarbon fluoranthene

Polychaetes belonging to the genus Capitella are often present in high numbers in organic-rich sediments polluted with, e.g., oil components, and Capitella spp. may have a great impact on the biogeochemistry of these sediments. We examined the influence of Capitella sp. I on microbial activity in an organic-rich marine sediment contaminated with the polycyclic aromatic hydrocarbon, fluoranthene. Capitella sp. I were added to microcosms (10 000 ind m⁻²) and the impact of a pulse-sedimentation of fluoranthene-contaminated sediment (3 mm layer) was studied for a period of 12 d after sedimentation. The sediment oxygen uptake and total sediment metabolism (TCO₂ production) increased in cores with worms (71 to 131%), whereas the anaerobic activity, measured as sulfate reduction rate 12 d after sedimentation, was lower compared to cores without worms. The effect of fluoranthene on sulfate reduction was most pronounced in the presence of worms, with a 34% reduction versus 16% in cores without worms. The reduced sulfur pools in cores with worms were smaller than in cores without worms, suggesting that the reduced anaerobic activity was caused by increased oxidation of the sediment, which may favor O₂ and other electron-acceptors (e.g. NO₃ ⁻, Fe³⁺, Mn⁴⁺) in organic matter decomposition. The sediment oxygen uptake and TCO₂ production did not show significant changes due to fluoranthene treatment, indicating that these parameters were either less sensitive to fluoranthene stress or recovered more rapidly (i.e. within 48 h) than sulfate reduction rates. Bioturbation by Capitella sp. I altered the depth profile of fluoranthene such that fluoranthene was found in deeper sediment layers (down to 2 cm) where diffusional loss and microbial breakdown probably are reduced relative to surface layers. In cores without worms, fluoranthene was found down to 1 cm, with 75% remaining in the upper 5 mm. Received: 5 December 1996 / Accepted: 11 February 1997     

武汉东湖近代沉积物中总氮、总磷与生物硅沉积与营养演化的动态过程

选择富营养化程度较高的武汉东湖作为研究对象,于2011年对其中4个子湖湖心的沉积物进行了采集,并分析了沉积物中总氮、总磷与生物硅含量。结果表明：对照东湖沉积速率（约0.33 cm·a-1）,在底层41～50 cm（1860—1890年）与31～40 cm（1890—1920年）,东湖4处子湖氮、磷、硅基本为湖泊自然沉积;在中层21～30 cm（1920—1950年）,人类活动有所增强,沉积有所变化;表层沉积物0～10 cm（1980—2010年）、11～20 cm（1950—1980年）中氮、磷、硅沉积普遍上升,这一时期对应着东湖人类干扰活动的普遍增加。对东湖4个子湖的沉积物氮、磷与硅的对比研究表明：人类活动增加了对东湖氮、磷的排放,促进了东湖硅藻的生长及硅的消耗,东湖不同子湖之间氮、磷、硅的沉积存在着明显差异,这可能与人类活动的影响差异有关。     

Ionic liquids for the inhibition of gas hydrates. A review

The formation of gas hydrates is a major issue during the operation of oil and gas pipelines, because gas hydrates cause plugging, thereby disrupting the normal oil and gas flows. A solution is to inject gas hydrate inhibitors such as ionic liquids. Contrary to classical inhibitors, ionic liquids act both as thermodynamic inhibitors and hydrate inhibitors, and as anti-agglomerates. Imidazolium-based ionic liquids have been found efficient for the inhibition of CO₂ and CH₄ hydrates. For CO₂ gas hydrates, N-ethyl-N-methylmorpholinium bromide showed an average depression temperature of 1.72 K at 10 wt% concentration. The induction time of 1-ethyl-3-methyl imidazolium bromide is 36.3 h for CO₂ hydrates at 1 wt% concentration. For CH₄ hydrates, 1-ethyl-3-methyl-imidazolium chloride showed average depression temperature of 4.80 K at 40 wt%. For mixed gas hydrates of CO₂ and CH₄, only quaternary ammonium salts have been studied. Tetramethyl ammonium hydroxide shifted the hydrate liquid vapour equilibrium to 1.56 K at 10 wt%, while tetrabutylammonium hydroxide showed an induction time of 0.74 h at 1 wt% concentration.

     

Different niches of the Halophila stipulacea seagrass bed harbor distinct populations of nitrogen fixing bacteria

Halophila stipulacea beds in the northern Gulf of Elat (Red Sea) may be subdivided into three different sub-habitats, each harboring a distinct population of diazotrophs. Nitrogen (N₂) fixation in the phyllosphere and in the rhizomes/upper-sediment niche was light dependent, suggesting its dependence on photosynthesis. N₂ fixation in the phyllosphere was not affected by the addition of either glucose or 3-3,4-dichloro-phenyl-1,1-dimethyl-urea (DCMU), indicating that the diazotrophs involved carried out non-oxygenic photosynthesis. They may, thus, have been photosynthetic bacteria. N₂ fixation in the rhizomes/upper-sediment niche, however, was greatly enhanced by the addition of glucose, but was suppressed in the presence of DCMU. This indicates that the diazotrophs involved here probably possess two photosystems (I and II) and may be Cyanobacteria. The anaerobic rhizosphere, in which fixation rates in light were very slow but were greatly enhanced by the addition of glucose, is probably populated by heterotrophic diazotrophs. Plant and sediment samples used in the present study were collected from the Gulf of Elat between 1990 and 1992.     

杭州西湖湖湾生物硅沉积测定与营养演化的过程

选择杭州西湖3处湖湾——茅家埠、乌龟潭、浴鹄湾作为研究对象,通过3处湖湾多点浅钻的表层沉积物生物硅质量分数测试,通过底泥分析西湖疏浚与水环境治理措施的效果。研究发现：对照西湖沉积速率（4mm／a）,3处湖湾表层沉积物中生物硅质量分数高低依次为茅家埠、乌龟潭与浴鹄湾。近10年来不同湖湾沉积物中生物硅沉积含量相差较大,这一时期正对应着西湖综合环境整治工程。对西湖3个湖湾表层沉积物中生物硅质量分数研究表明：西湖水体中的氮、磷、硅促进了硅藻的生长与硅的消耗,不同湖湾之间生物硅沉积存在着明显差异,这可能与人类活动的影响差异有关。     

Bioavailability of copper and cadmium in sediment of nanjing section of Changjiang river to aquatic organisms

Bioavailabilities of metals in sediment to aquatic organisms depend on the strength of metal bonding to particulates. The accumulation tests of Cu and Cd in carp and in snails have been studied in vitro with the solution containing semisynthetic sediment samples in which the contents of various speciation of metal in sediment have been extended. For carp, the accumulation of Cu and Cd is related to the concentration of dissolved metal which in turn is affected by the distributions of speciations in sediment under given environmental conditions. It is another pattern for snails, various speciations of metal in sediment can contribute indirectly to metal accumulation. The contribution ratio, or relative importance of various speciations of metal in sediment can be expressed by multiple linear regression formulas. The contribution of ion‐exchangable speciation and coprecipition with carbonate speciation is 10⁵ times larger than that of residue speciation in sediment.