Metal pollution of estuarine sediments caused by leaching of acid sulphate soils

This study tracks changes in metal distribution in estuarine sediments as a result of leakage from acid sulphate (AS) soil landscapes in the Boreal Zone (Finland). The main objective was to identify the impact of these nasty soils on sediment geochemistry in a biologically sensitive and shallow brackish-water estuary. In order to do this four sediment cores were sampled in a profile extending seawards from the mouth of the Vörå River, which is one of the most heavily AS soil-impacted rivers in Finland and Europe. Two of the cores were rather deep (2.5 m and 4.0 m) and the others were shallow (0.4 m and 0.8 m). The results showed that an appreciable amount of aluminium (Al), cobalt (Co), cadmium (Cd), copper (Cu), manganese (Mn), nickel (Ni) and zinc (Zn) were elevated in the surface and sub-surface of the sampled bottom sediments compared to the deeper sediment background levels. These metals are all known to be abundantly leached from the AS soils. At the site approximately 4 km away from the river mouth, the concentrations of Cd, Co, Mn, Ni and Zn were elevated 5–100 times as compared to the background levels and showed an intriguing cyclic pattern, most likely reflecting seasonal leaching dynamics in the AS soil landscapes. In contrast, metals that are not abundantly leached from AS soils, i.e. chromium (Cr), iron (Fe) and vanadium (V) had consistently low concentrations throughout all sediment cores. The elevated metal concentrations in the top layers of the sediments in the estuary are alarming. The continuous land uplift of the region combined with the episodic rapid declines in pH may result in short and long term extensive release of metals. This, in turn, may have significant effects on the trace-metal contents in the Gulf of Bothnia and the entire Baltic Sea.     

Linking pollution induced community tolerance (PICT) and microbial community structure in chronically metal polluted estuarine sediments

We tested the ability of pollution induced community tolerance (PICT) to detect the effects of chronic metal pollution on estuarine sediment microbial communities, along a gradient spanning two orders of magnitude in metal concentrations. In tandem, we investigated the associated microbial community structure using terminal restriction fragment length polymorphism (T-RFLP). Tolerance of microbes to Cu, measured as IC50 (inhibitory concentration 50%), was strongly correlated with pore water Cu concentration (r(2)=0.842). No strong correlation existed for other metals tested, highlighting the ability of PICT to identify the pollutant causing a toxic effect. There was no correlation between microbial community structure and community tolerance to metals tested, but analysis of community structure did provide some information on reasons for observed PICT response. PICT methodology used here provided a greater strength and consistency of association with pollutant concentration compared to microbial community structure and can be recommended as a sensitive indicator of metal pollution on estuarine sediment microbial communities.     

Geochemical and ecotoxicological assessment for estuarine surface sediments from Southern Brazil

Sediments from Guaratuba Bay (PR, Brazil), a marine protected area, were collected and evaluated for geochemistry and toxicity. High levels of P and acute toxicity were observed in some samples. Concentrations of Cu, Cd, Pb and Zn were relatively low; however, Cd levels eventually exceeded Threshold Effect Level. Toxicities were associated to nutrients and metals enrichment. Results suggest that impacts are incipient and occur only at specific sites, associated to multiple contamination sources. Despite sediments quality seems to range between good and fair, attention is required to land-use planning around Guaratuba Bay and controlling local pollution sources.     

Microbial activity in sandy and muddy estuarine sediments

Striking differences were observed in the use of the electron acceptors involved in the degradation of organic matter by heterotrophic bacterial activity between a muddy and a sandy sediment on the same tidal flat of the Scheldt estuary. These bio-reduction reactions could have a quite different effect on the cycling of trace metals in the sediment as suggested by the results of the mobilization experiments. Trace metal speciation can be described as a function of the redox potential, in view of the fact that the latter is related to the heterotrophic bacterial activity.     

河口污染沉积物中重金属释放与迁移的围隔生态系研究

利用围隔式生态实验装置研究了加拿大False河口污染沉积物中重金属Pb、Zn、Cd、Cu在海水环境中的行为。实验模拟了 4种环境条件 :( 1)高生产力 ;( 2 )低生产力 ;( 3 )高悬浮物含量 ;( 4 )还原环境。结果表明 ,污染沉积物中重金属在海水环境中的行为既取决于元素自身性质 ,亦受外界环境条件制约。还原环境能抑制重金属的释放 ,有助于体系中原有的重金属清除出水柱。低生产力条件下 ,Pb、Zn表现出释放行为 ,而高生产力和高悬浮物含量条件下 ,Pb、Zn表现出先释放后迁移 ,而Cd、Cu则呈现出相反的图象。研究了实验期间 4种重金属释放与迁移的净通量 ,表明氧化条件下Cu、Zn净释放通量比Cd、Pb高 1～ 2个量级。研究表明 ,添加粘土及向还原环境倾倒均有助于减轻污染沉积物倾倒后重金属的二次污染     

秦皇岛河口沉积物砷形态分布特征

河口沉积物在陆源砷向海洋输送过程中具有源和汇的双重作用,分析砷在河口沉积物中的存在形态和分布特征对于掌握砷的毒理效应和污染评价具有重要意义.通过野外调查和样品采集,对秦皇岛典型河流河口沉积物中砷的质量比进行了测定,并采用Tessier五步连续提取法对砷在沉积物中的存在形态进行了提取分析.结果表明,汤河河口表层沉积物中砷的质量比为35.73~46.63 mg/kg,戴河河口表层沉积物中砷的质量比为13.60~16.00 mg/kg,汤河河口沉积物砷含量明显高于戴河河口.总砷含量随沉积深度的增加而有降低的趋势.各形态砷在沉积物中的分布特征基本一致,即以残渣态为主,占其总量的87%以上,其他各形态相对含量较小,其中可利用性最强的可交换态含量最小,平均为1.04%.各形态砷分布与沉积物的pH和有机质含量有一定的相关关系, pH和有机质含量的改变将会影响砷的形态分布特征.     

Diatom size distributions and community stratification in estuarine intertidal sediments

The organization of an intertidal epipelic diatom community was quantified in terms of vertical cell-size distributions within soft sediments. Microgradients of grain and organic particle sizes, percentage of organics, porosity, light attenuation and oxygen distributions were measured over the top 5 mm of surface sediments. Epifluorescence microscopy and computerized planimetry showed that diatom cell size was bimodally distributed between very small and very large cells. The community was vertically stratified within the sediments with large numbers of small cells massed at the interface. Large cells were concentrated deeper in the microhabitat, far below light and oxygen penetration. Community organization was related to r-K selection theory, invertebrate herbivory and size-related adaptations of the diatoms.     

The behaviour of iodine and bromine in estuarine surface sediments

The distribution of iodine and bromine was examined in sediments which receive inputs of marine and terrigenous organic matter. The I and Br concentrations are directly related to the content of ‘marine’ organic matter defined using carbon/nitrogen ratios. In the Etive sediments both Br and I may be used as an indicator of ‘marine’ organic matter; Br is of general application as the $\text{Br}\text{C}{}_{\mathrm{mar}}$ ratio (180 × 10^?4) is similar to ratios in other sedimentary environments but the use of I is restricted as the $\text{I}\text{C}{}_{\mathrm{mar}}$ ratio is unlike those in other sediments. Experimental study of iodine sorption clearly shows the importance of decaying marine organic matter and oxygenated conditions in the incorporation of iodine by sediments. This suggests that the mechanism of incorporation of iodine by seston previously proposed is probably an important pathway to sediments. The similarity of Br association with marine organic matter suggests that Br sorption as opposed to residual enrichment may be important for sediment Br accumulation.     

Oxygenation of intertidal estuarine sediments by benthic microalgal photosynthesis

A mathematical model was used to define the relative importance of microalgal photosynthesis and physical processes in the formation and maintenance of the oxygenated zone on the surface of intertidal estuarine sediments. Manometric measurements of sediment uptake and release showed that gross oxygen production usually exceeded aerobic community respiration. Polarometric microprobes measured vertical oxygen distributions in the sediment. Surface levels of oxygen ranged from 200% saturation in summer to 70% in winter. Profiles and flux measurements allowed calculation of sediment diffusion coefficients. Empirical evaluation of the terms of the model showed that epipelic diatom photosynthesis as a source of oxygen at low tide may exceed atmospheric diffusion by an order of magnitude. On a diurnal and seasonal basis, however, the diatoms may be less important to the oxygenation process than the physical forces of the tide.     

Evaluation of extraction schemes for organic matter in anoxic estuarine sediments

A persistent criticism of studies of organic matter in sediments and soils has been that the extracted products used in these investigations may not resemble the original material, particularly if harsh extractants such as NaOH, Na₄P₂O₇ or HCl are employed. To minimize chemical changes, a mild separation procedure has been developed for obtaining soluble organic matter from anoxic estuarine sediments. The resulting complex mixture of organic compounds can be analyzed by reversed-phase liquid and size-exclusion chromatographic methods, which monitor the relative molecular polarity and size, respectively. The effects of the strong reagents NaOH, Na₄P₂O₇ and HCl, as well as exposure to the atmosphere and bacterial activity on this anoxic sedimentary extract has been investigated. In each instance, significant degradation of anoxic organic matter occurs, producing molecules of increased polarity and reduced molecular weight. These data indicate that extreme care is necessary to avoid artifacts in preparation and handling of samples.     

Sulfide control of cadmium and copper concentrations in anaerobic estuarine sediments

Equilibrium concentrations of the toxic trace metals copper and cadmium were calculated for the physico-chemical conditions characterizing pore waters of anaerobic estuarine sediments using available thermodynamic data and assuming simple sulfide minerals control solubilities. Polysulfide complexes are responsible for the solubility of copper in the cuprous (Cu(I)) oxidation state. Predicated copper concentrations, assuming covellite (CuS) is the controlling solid phase, are in reasonable agreement with copper analyses in a wide range of sulfidic waters and sediment pore waters. In the absence of thermodynamic data, no account could be taken of possible polysulfide complexes of cadmium. However, bisulfide complexes appear to account satisfactorily for observed solubilities assuming the existence of greenockite (CdS) as the controlling solid phase. Anaerobic estuarine sediments may act as a sink for copper and cadmium in the common situation in which free sulfide concentrations are controlled by the coexistence of iron sulfide and iron oxide minerals. However, where free sulfides reach high concentrations of 10^?3 M or more, the concomitant increase in concentration of bisulfide and polysulfide complexes may result in the sediments acting as a source of copper and cadmium.     

大连湾石油污染沉积物中细菌群落结构分析

大连新港"7.16"输油管道爆炸溢油事故发生后,为探究石油污染与细菌群落结构变化之间的关系及在石油生物降解过程中起重要作用的细菌菌群,本研究对大连湾表层沉积物中石油烃含量和细菌宏基因组16SrDNA V3区进行分析。结果表明:溢油初期2010年8月DLW01站位表层沉积物石油烃含量高达1 492mg/kg,符合第三类沉积物质量标准,随着时间推移,2011年4月、2011年7月、2011年12月航次各站位沉积物中石油烃含量基本呈下降趋势,且均符合第一类沉积物质量标准;16S rDNA PCR-DGGE方法分析表明,石油烃含量高的区域优势细菌种类少,反之则较丰富;海洋环境中同一地点的细菌群落能保持一定稳定性;大连湾石油污染沉积物中变形菌门γ-变形菌纲和拟杆菌门一直保持较高的优势度,是在石油生物降解过程中起重要作用的细菌菌群,而厚壁菌门只在石油烃含量低的区域出现;此外,出现的对污染物敏感的嗜冷杆菌可作为石油污染指示生物进行深入研究。     

深圳近海海域沉积物重金属污染状况评价

根据2000—2007年深圳近海海域表层沉积物的基础监测资料, 采用地累积指数和潜在生态危害指数两种评价方法, 对该区域沉积物中重金属的污染状况进行了分析和研究。结果表明, 深圳近海海域沉积环境在一定程度上已受到了重金属的污染, 除固戍近海外, 大部分海域基本上为II类沉积物, 其污染程度大小顺序为: 固戍近海＞深圳湾中＞深圳湾口＞沙头角湾口。其中沉积物中Cu和Zn超标严重, 固戍近海沉积物中Cu和Zn平均含量分别为128.96mg.kg-1和199.40mg.kg-1, 为III类沉积物。研究还表明, 深圳近海海域基本上不存在重金属潜在的生态危害, 7种重金属潜在的生态危害大小顺序为: Hg＞Cd＞Cu＞As＞Pb＞Cr＞Zn。     

Hydrocarbon pollution of the Mediterranean coastline of Morocco

Organic geochemical study of hydrocarbon pollution of the Mediterranean coastline of Morocco (Tangier-Nador) was performed during March–April 2002. It corresponds to a preliminary work representing an initial assessment of oil contamination of Moroccan coast.Three coastal sites corresponding to Tangier, Tetouan and Nador, representing the main built-up area of this marine region, were selected for superficial sediments, water and organism sampling. Results showed high contamination levels in these three selected sites, known as the most exposed areas to urban and industrial discharges. The maximal contamination corresponding to the sum of non-aromatic (NAH) and polycyclic aromatic hydrocarbons (PAH) encountered in sediment samples was about 553 μg/g (dw). Nevertheless, even a small city agglomeration without any industrial activity showed high values reaching 370 μg/g (dw), which confirm the important hydrocarbons input coming from discharges of fishing ships and oil transporting tankers.The obtained results from this survey reflecting in part the important amounts drained via effluents toward the Moroccan Mediterranean coasts, presented to the concerned authorities drove to the realization of the project of treatment of the wastewater.They later expect to lower rates by 50%, which is still insufficient for a fragile ecosystem such as the Mediterranean and sensitive to anthropogenic effects.     

Plutonium in intertidal coastal and estuarine sediments in the Northern Irish Sea

Surface intertidal sediments from 35 sites in the Irish Sea have been analysed for their ²³⁸Pu and ^239,240Pu activities, together with an intensive study of plutonium in sediments of the Esk Estuary (NW England). The range of plutonium activities for the whole survey were 0·14–4118 and 1·3–16 026 Bq kg⁻¹ for ²³⁸Pu and ^239,240Pu, respectively. The levels of Pu activity, derived from the Sellafield nuclear fuel reprocessing effluents, in sediments are controlled by lithological factors and the influence of transport and post-depositional processes. Grain size distribution is particularly important, the major part of plutonium activity being in the mud fraction of all sediments.The data suggest that over the Irish Sea coastline, dynamic mixing of sediment grains by reworking and resuspension and/or by dispersion in tidal currents are important in determining plutonium distributions. The exponential decrease in sediment plutonium activities away from the Sellafield source is attributed to the progressive mixing with older contaminated and uncontaminated sediments.     

Geochemical tracers of northern Portuguese estuarine sediments on the shelf

The northern Portuguese coastal zone is drained by large Iberian rivers, along which there is intensive industrial, agricultural and urban activity. Offshore of the two main river basins of the Douro and Minho, two fine-grained sedimentary formations can be characterised. A geochemical study of this sediment cover has been performed focussing in particular on the fine deposits and the adjacent estuaries. The chemical composition of superficial sediments collected from the northern Portuguese shelf and from the river basins of the Minho and Douro rivers was determined for major, minor and trace elements; the rare earth elements (REE) composition was also determined in selected samples. Statistical analyses of these data for the shelf sediments allow us to identify elements with similar behaviours and the different sediment types along the shelf, and to evaluate of their origins. Downcore profiles of the chemical composition of the fine sediments reveal no evidence for changes induced by recent human activities. To assess the influence of the rivers on the fine sedimentary formations, the elemental distribution patterns of selected sediments have been compared with the estuarine sediments. Lithogenic elements composition normalised to Al and the shale normalised REE distributions showed there are similarities between the Douro River sediments and the sediment composition of the Douro and Galicia mud patches. However, the Galicia mud field showed no relationship in its chemical composition to sediments derived from the Minho River. Nor was any evidence for heavy metal contamination originating from the Douro estuary detected in anthropogenic element/Al ratios in the shelf sediments. This may be because of processes associated with resuspension, complexation and bioturbation that occur during sediment transport and deposition. Nevertheless, the Douro River seems to be the main continental source of fine sediments being deposited on the northern Portuguese shelf.     

Experiments on the resuspension of estuarine sediments containing benthic diatoms

A laboratory system was used to test the effect of water flow on the resuspension of mud and sand sediments and, specifically, benthic diatoms from the Ems estuary, The Netherlands. Current velocities generated by two rotating cylinders in a cylindrical tank were determined by a small float and a laser Doppler velocimeter. At low angular velocities, the amount of suspended matter increased linearly with angular velocity and the float current velocity. However, at higher angular velocities, the increase in current velocity was less because of the strong turbulence: concomitantly, the current velocity boundary layer (δ) became thinner and the suspended matter concentration increased rapidly. The dominant diatom species from the sandy sediment were suspended in two distinct groups, one of which consisted of the species Navicula aequorea, Navicula salinicola, Ophephora martyi and Opephora pacifica, and was more exclusively bound to sand grains than the other. The benthic diatom species inhabiting the silty sediment did not show this difference. The most important shortcoming in the experiments was the inability to determine the radial and vertical velocity components. This precluded reliable calculations of the shear stress. The data presented emphasize the importance of finding a method to determine the shear stress under experiments and field conditions so that direct comparisons can be made. Despite this it is assumed that, just as under the experimental conditions discussed, under natural conditions in shallow waters resuspension starts at current velocities as low as ca. 10 cm s⁻¹.