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1.
To investigate the influence of mangrove reforestation on heavy metal accumulation and speciation in intertidal sediments, core sediments from a restored mangrove forest and adjacent mud flat in Yifeng Estuary (southeastern China) were analyzed. The chemical speciation of heavy metals (Pb, Zn, Cu, Cr and Ni) was determined according to a sequential extraction procedure. Special attention was paid to the upper 20 cm of sediment, in which metal accumulation was enhanced and speciation was obviously modified. Mangrove reforestation decreased the concentrations of all metals in the acid-soluble fraction and increased metal concentrations in the oxidizable fraction. Increased Pb, Zn and Cu concentrations and decreased Ni and Cr concentrations were observed in the reducible fraction. These results suggest that mangrove reforestation facilitated the accumulation of heavy metals in the upper sediment layers but decreased their bioavailability and mobility.  相似文献   

2.
Concentration of 7 heavy metals, Zn, Fe, Cu, Cr, Cd, Pb and Ni in mudflat sediments, mangrove root sediments and root tissues of Acanthus ilicifolius, Aegicerus corniculatum and Kandelia candel from the Mai Po Nature Reserve, Northwest Hong Kong, were measured. Metal concentrations in the upper 0–10 cm of the sediment cores from the mudflat were 4–25% higher than those found in the bottom 21–30 cm. Relative Topsoil Enrichment Index approximated 1.0 for all the metals. Mudflat sediment concentrations of Fe, Ni, Cr, Cd and Cu were greater than those found in the mangrove sediments. Except for Fe, concentrations of the other 6 heavy metals were more elevated in the mangrove root sediments than in the corresponding root samples. Higher concentration factors for Zn, Fe and Cu may indicate bioaccumulation. Mean metal concentrations in both mudflat and mangrove sediments decreased in the order Fe > Zn > Pb > Ni > Cu > Cr > Cd. Mangrove root tissues also showed the same pattern except that Pb > Cu > Ni  相似文献   

3.
Many urban rivers receive significant inputs of metal‐contaminated sediments from their catchments. Restoration of urban rivers often creates increased slack water areas and in‐channel vegetation growth where these metal‐contaminated sediments may accumulate. Quantifying the accumulation and retention of these sediments by in‐channel vegetation in urban rivers is of importance in terms of the planning and management of urban river restoration schemes and compliance with the Water Framework Directive. This paper investigates sediment properties at four sites across three rivers within Greater London to assess the degree to which contaminated sediments are being retained. Within paired restored and unrestored reaches at each site, four different bed sediment patch types (exposed unvegetated gravel, sand, and silt/clay (termed ‘fine’) sediments, and in‐channel vegetated sediments) were sampled and analysed for a range of metals and sediment characteristics. Many samples were found to exceed Environment Agency guidelines for copper (Cu), lead (Pb) and zinc (Zn) and Dutch Intervention Values for Cu and Zn. At all sites, sediments accumulating around in‐channel vegetation were similar in calibre and composition to exposed unvegetated fine sediments. Both bed sediment types contained high concentrations of pseudo‐total and acetic acid extractable metal concentrations, potentially due to elevated organic matter and silt/clay content, as these are important sorbtion phases for metals. This implies that the changed sediment supply and hydraulic conditions associated with river restoration may lead to enhanced retention of contaminated fine sediments, particularly around emergent plants, frequently leading to the development of submerged and emergent landforms and potential river channel adjustments. High pseudo‐total metal concentrations were also found in gravel bed sediments, probably associated with iron (Fe) and manganese (Mn) oxyhydroxides and discrete anthropogenic metal‐rich particles. These results highlight the importance of understanding the potential effects of urban river restoration upon sediment availability and channel hydraulics and consequent impacts upon sediment contaminant dynamics and storage. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

4.
Spatial and temporal variations of heavy metal contamination in sediments of a small mangrove stand in Hong Kong were examined by laying two transects perpendicular across the shore. Surface sediment samples were taken along the two transects running landward to seaward at intervals of 5 or 10 m during December 1989, and March, July and September 1990. Total concentrations of Cu, Zn, Mn and Pb did not show any specific trend along each transect, although the maximum concentration of heavy metals tended to occur at the landward edge. There was a high level of variability among locations within each transect; for instance, the Cu concentrations fluctuated from 1 to 42 μg g−1. Certain sites contained exceptionally high levels of total metals. Total concentrations of Cu, Zn, Mn and Pb as high as 42, 150, 640 and 650 μg g−1, respectively, were recorded, implying contaminated sediment. A comparison of the two transects indicated that the sediments of Transect B seemed to contain higher total Zn but lower Cu and Mn concentrations than those of Transect A. Most of the heavy metals accumulated in the sediments were not extractable with ammonium acetate and no Cu or Pb was detected in these extracts. The concentrations of extractable Zn and Mn were low, less than 10% of the total metal concentration in the sediment, and appeared to decrease from the landward to seaward samples. For both total and extractable metals, there were significant seasonal fluctuations for both transects, but no specific trends could be identified. These spatial and temporal variations suggest that the scale and representativeness of sampling require careful planning, and a single sample might not give a satisfactory evaluation of the levels of heavy metal contamination in mangrove ecosystems.  相似文献   

5.
Effects of suspended mussel and infaunal clam cultivation on sediment characteristics, and benthic organic and inorganic nitrogen and phosphorus fluxes were compared in a shallow coastal lagoon. The two species had different impacts on sediment features, but both created “hotspots” of nutrient fluxes with annual N and P regeneration rates being 4.9 and 13.5 (mussel) and 4.5 and 14.9 (clams) fold greater than those of unfarmed control sediments. Mussel farming also caused considerable nutrient regeneration within the water column with the mussel ropes contributing ∼25% of total inorganic N and P production and at times dominating the sediments (e.g. 95% of SRP production in summer and 45% of DIN production in winter). Such nutrient regeneration rates seriously question the proposal that suspension-feeding bivalves act as a eutrophication buffer, especially during summer when nutrient regeneration rates are maximal, but other nutrient sources (freshwater run-off and unfarmed sediments) are at their lowest.  相似文献   

6.
Trace metal retention in mangrove ecosystems in Guanabara Bay,SE Brazil   总被引：1，自引：0，他引：1  
Along contrasting environmental conditions (e.g., degree of trace metal contamination and mangrove forest structural development), sediments of Laguncularia racemosa-dominated mangrove stands in Guanabara Bay (SE Brazil) presented a trend of trace metal accumulation in forms with low potential of remobilization and biotic uptake. Concurrently, a relatively low transfer of sediment-bound metals to L. racemosa leaves was observed, which may moderate the metal export from the forests via leaf litter transport and the metal availability to enter in food chains based on leaf consumption.  相似文献   

7.
The distribution of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) were studied in sediments collected from mangrove forest, forest fringe and adjacent mudflat in the Zhangjiang Estuary, China. The aim was to examine the spatial distribution of AVS and SEM in sediments of the Estuary and determine the influence of mangrove trees on AVS and SEM concentrations in the sediments. The results indicated that AVS concentrations in forest sediments were significantly lower than those in mudflat sediments. There was a significant positive correlation between AVS values and moisture contents in forest sediments, while LOI played an important role in AVS concentrations of mudflat sediments. In the forest sediment core, the peak value of AVS appeared deeper in the sediment profile compared to it appeared in the mudflat core. The distribution of SEM showed different trends from that of AVS, and potential toxicity existed in the upriver forest sediments.  相似文献   

8.
To investigate the influence of mangrove reforestation on the accumulation of PCBs, the concentrations and homologue patterns of polychlorinated biphenyls in surface sediments from different mangrove forests and their adjacent mud flats in Guangdong Province were determined. The total PCB concentrations in the sediments ranged from 3.03 to 46.62 ng g?1 (dry weight). Differences in the accumulation and distribution of PCBs were found between the mangrove sites and the mud flats. Furthermore, the natural forests and restored mangrove forests of native species showed slight PCB contamination, whereas the exotic species Sonneratia apetala exacerbated the PCB pollution at certain sites. It was suggested that the native mangrove species Kandelia candel and Aegiceras corniculatum could represent good choices for the phytoremediation of PCB contamination.  相似文献   

9.
Methane concentrations and selected chemical parameters in interstitial water were examined along subsurface flowpath in two subsystems (hyporheic and parafluvial sediments) in the Sitka stream, Czech Republic. Interstitial methane concentrations exhibited a distinct spatial pattern. In the hyporheic downwelling zone where the sediments are relatively well oxygenated due to high hydrologic exchange with the surface water, low interstitial methane concentrations, averaging 9.3 μg CH4/l, were found. In contrast, upwelling sediments and parafluvial sediments (active channel sediments lateral to the wetted channel) had significantly higher methane concentrations (p < 0.05, and p < 0.01, respectively), averaging 43.2 μg CH4/l and 160.5 μg CH4/l, respectively. Dissolved oxygen was the highest where surface water entered hyporheic/parafluvial sediments and decreased with water residence time in the sediments (p < 0.01). Nitrate concentrations decreased along the flowpath and were significantly lower at downstream end of the riffle (p < 0.001). Sulfate concentrations also show a slight decline with the water residence time, but differences were not significant. Effect of both nitrate and sulfate on methanogenesis is also discussed. The interstitial methane concentration significantly increased with surface water temperature (p < 0.001) and was negatively correlated with redox potential (p < 0.01) and dissolved oxygen (p < 0.05).  相似文献   

10.
To complement physical and chemical data, information of biological communities is important to assess the qualities of mangrove sediments receiving wastewater. Ciliate communities have cosmopolitan distribution, short life cycle and high sensitivity to pollutants, which make them useful as biological indicators of the sediment environment. In most literature, ciliates are widely used as bioindicators for the state of water quality. In this study, the physico-chemical parameters and ciliate community structure of surface sediment collected at different sampling points from two constructed mangrove (Aegiceras and Sonneratia) belts for treatment of municipal sewage in southern China were investigated. Results showed that most (> 80%) of the 216 species ciliates identified at the two constructed mangrove belts were either omnivorous or bacterivorous. Sediment redox potential (Eh) was considered an important factor to govern the distribution of ciliate species within the mangrove sediment. The saprobic system originally derived from freshwater ecosystem was used to evaluate the saprobic degrees of these constructed mangrove belts. Saprobic index (SI) values declined from the sewage inlet to the outlet points of the constructed belts, suggesting better sediment quality at the outlet point caused by treatment processes within the mangrove belt system. Sediment quality of the sewage outlet area of the constructed Aegiceras belt was determined as class II-III (SI = 2.48), while that of the Sonneratia belt was as class III (SI = 2.71) according to the saprobic classification, indicating that a better sewage treatment efficiency was apparent in the Aegiceras than Sonneratia belt. The present data suggested that ciliates could serve as a good bioindicator in assessing organically polluted sediment qualities.  相似文献   

11.
《Marine pollution bulletin》2009,58(6-12):689-694
To complement physical and chemical data, information of biological communities is important to assess the qualities of mangrove sediments receiving wastewater. Ciliate communities have cosmopolitan distribution, short life cycle and high sensitivity to pollutants, which make them useful as biological indicators of the sediment environment. In most literature, ciliates are widely used as bioindicators for the state of water quality. In this study, the physico-chemical parameters and ciliate community structure of surface sediment collected at different sampling points from two constructed mangrove (Aegiceras and Sonneratia) belts for treatment of municipal sewage in southern China were investigated. Results showed that most (> 80%) of the 216 species ciliates identified at the two constructed mangrove belts were either omnivorous or bacterivorous. Sediment redox potential (Eh) was considered an important factor to govern the distribution of ciliate species within the mangrove sediment. The saprobic system originally derived from freshwater ecosystem was used to evaluate the saprobic degrees of these constructed mangrove belts. Saprobic index (SI) values declined from the sewage inlet to the outlet points of the constructed belts, suggesting better sediment quality at the outlet point caused by treatment processes within the mangrove belt system. Sediment quality of the sewage outlet area of the constructed Aegiceras belt was determined as class II-III (SI = 2.48), while that of the Sonneratia belt was as class III (SI = 2.71) according to the saprobic classification, indicating that a better sewage treatment efficiency was apparent in the Aegiceras than Sonneratia belt. The present data suggested that ciliates could serve as a good bioindicator in assessing organically polluted sediment qualities.  相似文献   

12.
Mangroves have been observed to possess a tolerance to high levels of heavy metals, yet accumulated metals may induce subcellular biochemical changes, which can impact on processes at the organism level. Six month-old seedlings of the grey mangrove, Avicennia marina (Forsk.) Vierh, were exposed to a range of Cu (0-800 micrograms/g), Pb (0-800 micrograms/g) and Zn (0-1000 micrograms/g) concentrations in sediments under laboratory conditions, to determine leaf tissue metal accumulation patterns, effects on photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids), and the activity of the antioxidant enzyme peroxidase. Limited Cu uptake to leaves was observed at low sediment Cu levels, with saturation and visible toxicity to Cu at sediment levels greater than 400 micrograms/g. Leaf Pb concentrations remained low over a range of Pb sediment concentrations, up to 400 micrograms/g Pb, above which it appeared that unrestricted transport of Pb occurred, although no visible signs of Pb toxicity were observed. Zn was accumulated linearly with sediment zinc concentration, and visible toxicity occurring at the highest concentration, 1000 micrograms/g Zn. Significant increases in peroxidase activity and decreases in photopigments were found with Cu and Zn at concentrations lower than those inducing visible toxicity. Significant increases in peroxidase activity only, were found when plants were exposed to Pb. Positive linear relationships between peroxidase activity and leaf tissue metal concentrations were found for all metals. Significant linear decreases in photosynthetic pigments with increasing leaf tissue metal concentrations were observed with Cu and Zn only. Photosynthetic pigments and peroxidase activity may be applicable as sensitive biological indicators of Cu and Zn stress, and peroxidase activity for Pb stress in A. marina.  相似文献   

13.
Inventory of nutrients in the Bohai   总被引：3，自引：0，他引：3  
Biogeochemical observations were carried out to address the influence of major sources on nutrient composition and the ecosystem of the Bohai. Relatively high concentrations of nutrients off the Huanghe mouth and the shallow water areas were observed in the Bohai suggesting the effects of tidal and residual currents and anthropogenic perturbation. Sediment in the Bohai represents a source for ammonium, phosphate and dissolved silicate, while it is a sink for nitrite and nitrate. Benthic nutrient fluxes were 2-3 times higher than the riverine input with the regeneration rate of phosphate being slower relative to DIN and dissolved silicate. The release of dissolved silicate and phosphate from sediments may mitigate the decrease of dissolved silicate and phosphate due to the reduction of freshwater discharge. Compared with submarine groundwater discharge, nutrient regeneration in sediment provides similar DIN flux, 2-5 times phosphate and dissolved silicate fluxes. DIN/P molar ratios in the three mentioned sources were 155-845, indicating that phosphorus limitation for phytoplankton growth could be intensified, which likely results in changes of ecosystems of the Bohai.  相似文献   

14.
The Mandovi and Chapora are two tropical estuaries lying in close geographic proximity on the west coast of India. Seasonal changes in down core variation of Fe, Mn and Total Organic Carbon (TOC) in the mangrove sediments adjoining these estuaries were studied to assess their influence on some of the representative benthic bacteria belonging to heterotrophic and autotrophic groups. Heterotrophic bacteria (HB) cultured on different nutrient concentrations (0.01%, 0.1% and 25%) together with nitrifiers (NtB; representating autotroph) were chosen to assess the influence of the above-mentioned abiotic parameters on the former. The experimental site located along the Mandovi is under the influence of extensive ferromanganese ore mining, while the control site at Chapora is relatively free from such influences. Geoaccumulation index computed for Mandovi showed that sediments (0-10cm) were 'uncontaminated to moderately contaminated' by Fe during the pre monsoon and monsoon seasons, while in the post monsoon season the 4-10cm fraction was almost completely restored from contamination. Similar computations for Mn showed that in pre monsoon, sediments fell in the 'moderately contaminated' and 'moderately to strongly contaminated' categories, while in the monsoon and post monsoon seasons all the sections were 'Uncontaminated'. The difference observed in correlation between Fe and Mn with the various fractions of heterotrophs and nitrifiers indicated that though these two elements shared a similar chemistry in the environment, microbes involved in biogeochemical processes might prefer them differentially. The relationship between TOC and HB enumerated on 0.01% dilute nutrient agar remained at r=0.50, p<0.05 throughout the year. Hence, it could be apparently linked to their preferred concentration of organic carbon requirement. A relationship of r=0.61, p<0.01 between manganese concentration and heterotrophs recovered on different strengths of nutrient agar is suggestive of their response to the metal enrichment. They could thus contribute towards maintaining the level of Mn at par with reference levels at Chapora. A positive correlation between Mn with NtB (n=10, p<0.05, r=0.58) at the experimental site during the non-monsoon months is suggestive of the latter's contribution to regulation of the metal concentration in the sediment probably through anaerobic nitrification at the expense of manganese. The study therefore supports our hypothesis that both autochthonous autotrophs and heterotrophs work in tandem to mitigate concentration of Mn and related metals in mangrove sediments.  相似文献   

15.
Elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) have been found in mangrove sediments due to anthropogenic pollution, and microbial degradation has been suggested as the best way to remove PAHs from contaminated sediments. The degradation of phenanthrene, a model PAH compound by bacteria, either the enriched mixed culture or individual isolate isolated from surface mangrove sediments was examined. The effects of salinity, initial phenanthrene concentrations and the addition of glucose on biodegradation potential were also investigated. Results show that surface sediments collected from four mangrove swamps in Hong Kong had different degree of PAH contamination and had different indigenous phenanthrene-degrading bacterial consortia. The enriched bacteria could use phenanthrene as the sole carbon source for growth and degrade this PAH compound accordingly. A significant positive relationship was found between bacterial growth and percentages of phenanthrene degradation. The phenanthrene biodegradation ability of the enriched mixed bacterial culture was not related to the degree of PAH contamination in surface sediments. The growth and biodegradation percentages of the enriched mixed culture were not higher than that of the individual isolate especially at low salinity (0 and 10 ppt). High salinity (35 ppt) inhibited growth and biodegradation of phenanthrene of a bacterial isolate but less inhibitory effect was found on the mixed culture. The inhibitory effects of salinity could be reduced with the addition of glucose.  相似文献   

16.
Due to the growing rate of urbanisation in many tropical coastal areas, there continues to be an increasing concern in relation to the impact of anthropogenic activities on mangrove forests. Punta Mala Bay is located on the Pacific coast of Panama and suffers from intense anthropogenic activities that are potentially harmful to the remaining mangrove forests. Field observations reveal that the mangrove stand within Punta Mala Bay receives high inputs of untreated domestic sewage, storm water run-off and a range of diffuse inputs from shipping activities. Results from analysis of eight metals (Mn, Cu, Zn, Ni, Pb, Fe, Cr, Cd) showed that Fe, Zn and Pb were in concentrations high enough to conclude moderate to serious contamination within the bay, and thus pose the most threat to the regeneration and growth of the mangrove. However, previous biological surveys indicate ongoing mangrove regeneration and domination of stand structure by Laguncularia racemosa, together with high numbers of seedlings and saplings.  相似文献   

17.
The purpose of this study was to establish the distribution, speciation and bioavailability of mercury in mangrove sediments. A systemic survey of surficial sediments from 13 mangrove wetlands of China was carried out. Hg concentrations ranged from 2.3–903.6 ng g−1, with an average value of 189.4 ng g−1. Of the 13 areas surveyed, the Hg content in sediments was similar to background levels in 6 areas but was much higher in the other seven areas. Hg levels were affected by natural and anthropogenic factors, including terrestrial pollutants, geomorphic properties, and indirectly by economic status. Hg levels were positively correlated with organic matter, pH, and silt and clay fractions, but Hg was negatively correlated with sand fraction. In most mangrove wetlands, Hg existed primarily in the form of volatile Hg. Hg is easily bioaccumulated in mangrove wetlands and may be the natural source of Hg emissions to the atmosphere.  相似文献   

18.
During the autumn of 2000, large areas of England and Wales were affected by severe flooding, which caused widespread disruption and significant damage to property. This study attempts to determine the impact of these flood events on contaminated sediment dispersal and deposition in the River Swale catchment, Yorkshire, UK, where lead and zinc were extracted and processed in large quantities during the nineteenth century. Seventy samples of overbank and channel‐edge sediments were collected at 35 sites along the River Swale. Inductively coupled plasma‐mass spectrometry was used to measure contaminant metal concentrations in the 2000–63 µm (sand) and <63 µm (silt and clay) size fractions. In both the channel‐edge and overbank sediments collected from the upper and middle reaches of the River Swale, concentrations of lead, zinc and cadmium were found to exceed MAFF guidelines. Highest concentrations correspond to the input of contaminated material from intensively mined tributaries, and elevated levels can be observed 5–10 km downstream of these inputs. This indicates that the remobilization of contaminated material during major flood events is potentially a serious problem for activities such as agriculture that utilize the Swale floodplain. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

19.
Wen‐Cheng Liu 《水文研究》2005,19(20):4039-4054
A vertical (laterally integrated) two‐dimensional numerical model was applied to study the hydrodynamic characteristics, salt‐water intrusion and residual circulation in the Danshuei River estuarine system. The cross‐sectional profiles measured in 2001 and 1990 respectively represent the conditions after and before channel regulation in the Keelung River. The model was re‐verified with the available hydrological data measured in 2001. Detailed model re‐verification has been conducted with water surface elevations, tidal current, and salinity distributions measured. The overall performance of the model is in qualitative agreement with the available field data. The model was then used to investigate the change in tidal ranges, salt‐water intrusion, and residual circulation as a result of channel regulation in the Keelung River. The model simulations indicate that more tidal energy propagates into the estuarine system before channel regulation because of the substantial increase in river cross‐sections. The residual circulations before channel regulation are greater than those after channel regulation and result in the limits of the salt intrusion before channel regulation being extended farther inland than those after channel regulation. This may show that channel regulation for flood control in the Keelung River did not contribute to the expansion of the mangrove areas and the disappearance of freshwater marshes at the Kuan‐Du wetlands. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

20.
Occurrence of selected estrogens in mangrove sediments   总被引：1，自引：0，他引：1  
This paper presents results related to the occurrence and distribution of estrogens along the Brazilian coast. Three mangrove areas were chosen to evaluate the presence of estrogens in surface sediments of mangrove forests. The presence of estrogens was observed in all studied sites. 17-α-Ethinylestradiol (EE2), a synthetic estrogen, was the most common and has been found in higher concentration (0.45-129.78 ng/g) compared to 17-β-estradiol (E1) and estrone (E2) (both being natural estrogens). The concentrations of E1 and E2 ranged from 0.02 to 49.27 ng/g and 0.03 to 39.77 ng/g, respectively. Theoretically, under anaerobic conditions EE2 can be reduced to E1 even in environments such as sediments of mangrove forests, which are essentially anaerobic. Even if the concentrations of estrogens seem to be insignificant in some samples, the effects remain uncertain.  相似文献   

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