Sediment Quality Indices Research Articles

Micro-spatial variation of elemental distribution in estuarine sediment and their accumulation in mangroves of Indian Sundarban.

This work describes the micro-spatial variation of elemental distribution in estuarine sediment and bioaccumulation of those elements in different mangrove species of the Indian Sundarbans. The potential ecological risk due to such elemental load on this mangrove-dominated habitat is also discussed. The concentrations of elements in mangrove leaves and sediments were determined using energy-dispersive X-ray fluorescence spectroscopy. Sediment quality and potential ecological risks were assessed from the calculated indices. Our data reflects higher concentration of elements, e.g., Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb, in the sediment, as compared to that reported by earlier workers. Biological concentration factors for K, Ca, Mn, Fe, Cu, and Zn in different mangroves indicated gradual elemental bioaccumulation in leaf tissues (0.002-1.442). Significant variation was observed for elements, e.g., Ni, Mn, and Ca, in the sediments of all the sites, whereas in the plants, significant variation was found for P, S, Cl, K, Ca, Mn, Fe, Cu, and Zn. This was mostly due to the differences in uptake and accumulation potential of the plants. Various sediment quality indices suggested the surface sediments to be moderately contaminated and suffering from progressive deterioration. Cu, Cr, Zn, Mn, and Ni showed higher enrichment factors (0.658-1.469), contamination factors (1.02-2.7), and geo-accumulation index (0.043-0.846) values. The potential ecological risk index values considering Cu, Cr, Pb, and Zn were found to be within "low ecological risk" category (20.04-24.01). However, Cr and Ni in the Sundarban mangroves exceeded the effect range low and probable effect level limits. Strong correlation of Zn with Fe and K was observed, reflecting their similar transportation and accumulation process in both sediment and plant systems. The plant-sediment elemental correlation was found to be highly non-linear, suggesting role of some physiological and edaphic factors in the accumulation process. Overall, the study of micro-spatial distribution of elements can act as a useful tool for determining health of estuarine ecosystem.

Recovery of saltmarsh meiofauna six years after the Deepwater Horizon oil spill

We examined the recovery of infauna from the 2010 Deepwater Horizon oil spill in reference, moderately and heavily oiled Louisiana, USA salt marshes. Although density and diversity were severely impacted by the spill initially, total meiofauna, nematodes, copepods, and annelids, excluding the polychaete Manayunkia aestuarina, recovered in about 3years in near synchrony with Spartina alterniflora stem density. However other common taxa either recovered more slowly (i.e., juvenile bivalves and amphipods) or remained significantly lower in density at oiled compared to reference sites 6years after the spill. Specifically, M. aestuarina, the tanaid Hargeria rapax, the kinorhynch Echinoderes coulli, ostracods, and juvenile gastropods did not recover at the heavily oiled sites, and M. aestuarina and E. coulli failed to recover at moderately oiled sites. Several factors possibly contributed to slow recovery even after the re-establishment of aboveground vegetation. The concentration of petroleum hydrocarbons (TPH) remained elevated at moderately and heavily oil sites, and the direct toxic effects of oil may have been long lasting for intolerant fauna; the densities of E. coulli and M. aestuarina across all samples were inversely correlated with TPH. In addition, several of the slowly recovering taxa also disperse slowly. Finally, live belowground biomass of roots and rhizomes (a key indicator of sediment quality) remained significantly reduced at heavily and moderately oiled sites, and belowground biomass and the densities of M. aestuarina and juvenile gastropods were positively correlated. We conclude that the factors controlling the rate and intensity of infaunal recovery from the DHOS differed among taxa and over time. The factors that were important later in the recovery process were not dissimilar to those affecting succession following marsh restoration by planting S. alterniflora, and the legacy of oiling from the spill did not greatly slow the recovery of infauna compared to that observed in restored wetlands. At current rates, full recovery of the infaunal community will require about a decade at moderately oiled and longer at heavily oiled sites.

A bacterial community-based index to assess the ecological status of estuarine and coastal environments

Biotic indices for monitoring marine ecosystems are mostly based on the analysis of benthic macroinvertebrate communities. Due to their high sensitivity to pollution and fast response to environmental changes, bacterial assemblages could complement the information provided by benthic metazoan communities as indicators of human-induced impacts, but so far, this biological component has not been well explored for this purpose. Here we performed 16S rRNA gene amplicon sequencing to analyze the bacterial assemblage composition of 51 estuarine and coastal stations characterized by different environmental conditions and human-derived pressures. Using the relative abundance of putative indicator bacterial taxa, we developed a biotic index that is significantly correlated with a sediment quality index calculated on the basis of organic and inorganic compound concentrations. This new index based on bacterial assemblage composition can be a sensitive tool for providing a fast environmental assessment and allow a more comprehensive integrative ecosystem approach for environmental management.

부산 연안해역의 잔류성 유기오염물질과 중금속 오염평가: 퇴적물 오염지수 적용

부산 연안해역의 잔류성 유기오염물질과 중금속 오염평가: 퇴적물 오염지수 적용

Comparison of pollution indices for the assessment of heavy metal in Brisbane River sediment

Estuarine environment is complex and receives different contaminants from numerous sources that are persistent, bioaccumulative and toxic. The distribution, source, contamination and ecological risk status of heavy metals in sediment of Brisbane River, Australia were investigated. Sediment samples were analysed for major and minor elements using LA-ICP-MS. Principal component analysis and cluster analysis identified three main sources of metals in the samples: marine sand intrusion, mixed lithogenic and sand intrusion as well as transport related. To overcome inherent deficiencies in using a single index, a range of sediment quality indices, including contamination factor, enrichment factor, index of geo-accumulation, modified degree of contamination, pollution index and modified pollution index were utilised to ascertain the sediment quality. Generally, the sediment is deemed to be “slightly” to “heavily” polluted. A further comparison with the Australian Sediment Quality Guidelines indicated that Ag, Cr, Cu, Ni, Pb and Zn had the potential to rarely cause biological effects while Hg could frequently cause biological effects. Application of potential ecological risk index (RI) revealed that the sediment poses moderate to considerable ecological risk. However, RI could not account for the complex sediment behaviour because it uses a simple contamination factor. Consequently, a modified ecological risk index (MRI) employing enrichment factor is proposed. This provides a more reliable understanding of whole sediment behaviour and classified the ecological risk of the sediment as moderate to very high. The results demonstrate the need for further investigation into heavy metal speciation and bioavailability in the sediment to ascertain the degree of toxicity.

Concentrations of persistent organic pollutants and organic matter characteristics as river sediment quality indices

ABSTRACTSelected persistent organic pollutants – polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine pesticides – were determined in sediments, soils, and crops from the Asopos River area, Greece. The river has been receiving industrial effluents for the last 40 years and has been recently found to be polluted with metals. Sediments were collected in the dry (May) and wet (February) season. Agricultural soils and cultivated crops were sampled from adjacent fields. Polychlorinated biphenyls were below the limit of detection in all samples. In one tomato and two soil samples, DDT and DDE were found. Polycyclic aromatic hydrocarbons were observed in 5% of the sediments and in concentrations ranging from 4 to 57 μg kg−1 dry weight, quite below sediment quality guidelines. Diagnostic ratios of polycyclic aromatic hydrocarbons indicated a strong influence of petrogenic point discharges. In the sediments, silicate minerals dominate over carbonates and the organic carbon content ranges from 0.4% to 3.5%, more than 70% being of natural origin. Compared to other rivers worldwide, the Asopos River was found to be not contaminated with persistent organic pollutants. Point loadings of organic pollutants were evident but continuous discharge is not occurring throughout the river basin.

Polycyclic Aromatic Hydrocarbons (PAHs) and Heavy Metal Occurrence in Bed Sediments of a Temporary River

The directive 2008/105/EC suggests the use of sediment or biota matrix for long-term monitoring of specific priority pollutants that tend to accumulate. But, the intermittent nature of flow in the majority of the Mediterranean rivers results in large variability of biological communities and especially fish, making advantageous the examination of pollution trend in sediment matrix and not in living organisms (biota). In this study, sediment environmental quality standards (EQSs) and sediment quality indicators (SQIs) were used to assess pollution by heavy metals (cadmium, nickel, lead, mercury, arsenic, chromium, copper, and zinc) and polycyclic aromatic hydrocarbons (PAHs) in Evrotas River, South Greece, monitored seasonally for 2 years (2009–2010) in five sampling sites. The results showed that, based on SQIs (geoaccumulation index (Igeo), enrichment factor (EF), and modified degree of contamination (mCd)), sediments of the Evrotas River can be classified as “low polluted,” with some exceptions of “extreme pollution.” EQS assessment revealed heavy metal pollution ranging from “low” to “medium high.” Furthermore, based on the Hakanson’s ecological risk index (RI) method, heavy metal potential risk was classified from “low” to “extreme.” Cadmium showed the highest RI values, while mercury reached “moderate” pollution level. The average ΣPAH concentration (24.4 ng g−1) was lower than both the reported EQSs and the values found in literature for unpolluted or moderately polluted river sediments. Increased heavy metal and PAH concentrations were found in sites where mixing of freshwater with reclaimed water occurred. EQSs are suggested to be supplemented with the RI or EF index that consider the natural background to assist a first ecorisk assessment and should be foreseen by 2008/105/EC directive. Sediments can be considered as a valuable matrix in assessing the spatial and temporal trends of several contaminants and should be included in the monitoring program of temporary river management plans. Special attention should be given when defining reference sites and the sampling period. Decreasing flow period at the beginning of the spring prevailed in order to diminish any disturbance by flash flood events.

Southern California Bight regional monitoring

The Southern California Bight (SCB) is a unique ecological and economic resource, home to some of the most productive coastal ecosystems, but also some of largest pollutant inputs in the United States. Historically, environmental monitoring of the coastal environment has been temporally intensive, but spatially focused on narrow areas closest to regulated discharges, providing a potentially biased perspective of overall coastal sediment quality. Beginning in 1994 and conducted approximately every five years thereafter, nearly 100 regulated, regulatory, non-governmental or academic organizations join forces to implement the SCB Regional Marine Monitoring Program (the Bight Program). The most recent Bight program sampled nearly 400 locations, from the head of tide in coastal estuaries to offshore basins 1000 m in depth, using a probabilistic survey design and measuring multiple indicators of sediment quality including chemistry, toxicity, and infauna. The three indicators were scored using regionally-developed assessment tools, and then combined for an integrated assessment of sediment quality. Results showed that the vast majority of SCB sediments do not have impacted sediment quality, but that not all habitats are in equally good condition. Most of the continental shelf is not impacted, despite the discharge of very large volumes (109 L/day) of treated wastewater discharges. In contrast, up to 50% of the area in estuaries and 45% of the area in marinas have impacted sediment quality. These generally quiescent waterbodies receive pollutant inputs from the region’s extensively urbanized watersheds and high density of boating activities. Despite the relatively large extent of impacted sediment quality in embayments, sediment quality has been steadily improving in this habitat over the last decade based on surveys dating back to the 1998. The Bight Program has affected management actions in the region by focusing current efforts in habitats most impacted by poor sediment quality, and highlighting the improvements from previous management actions.

Application of a Sediment Quality Index for the assessment and monitoring of metals and organochlorines in a premier conservation area.

The physical and chemical characteristics of surface sediments from a leading conservation area, namely the Kruger National Park, were determined in order to identify potential stressors in the systems that may contribute to overall deterioration in sediment quality within the reserve, leading to potential threats to the aquatic biota conserved within these stretches of river. Sediment samples were collected during four surveys (two low flow and two high flow) from 2009 to 2011. Samples were analysed for organic content, grain size determination, metals and various organochlorine pesticides. Results indicated that the Olifants River sediments did not show any great improvement over the years and point towards the continued input of pollutants into this system. Sediment quality in the Luvuvhu and Letaba Rivers is better than that of sediments from the Olifants River in terms of metals, but metal concentrations are still comparable and point towards anthropogenic inputs of metals into these rivers. Even though the data indicate that these systems are being contaminated with both metals and organochlorine pesticides (OCPs), levels were still below contaminated sediments from around the globe. Sediment Quality Index scores showed that the sediment quality of these rivers is in a relatively good state. High metal concentrations were the drivers behind lowered sediment quality, and in some cases certain OCPs played a role. Both metals and OCP concentrations were highly correlated with finer grain sizes. Sediment assessments are not routinely applied in South Africa resulting in very little reference or background data available for the area. The metal concentrations for the study area were generally lower than those for other studies in more polluted regions. The study also contributes to the available knowledge on surrounding metal pollution in riverine sediments in South Africa.

Trace Elements in the Marine Sediments of the La Paz Lagoon, Baja California Peninsula, Mexico: Pollution Status in 2013.

To determine the actual concentrations of trace elements in surface sediments from the La Paz Lagoon, as well as their associations and possible origins, 91 sediment samples were analyzed for more than 50 elements using a combination of ICP-MS and ICP-AES. The results of a principal component analysis are used to distinguish four associative groups within the elements. Natural enrichment of As, Cd and U occurs due to the supply of weathered phosphorites from the El Cien formation located to the north-west of the lagoon. Sediment quality indices for potentially toxic trace elements do not show any probable impact on the biota of the lagoon. Only the concentrations of As in 30 % of the stations and Cu in 20 % of them exceed related effect range low levels. The highest concentration of Pb (36.8 mg kg(-1)) was measured in the sediments near the City of La Paz.

Potentially problematic elements in sediment and fish from the Orange-Vaal River system

Potentially problematic elements in sediment and fish from the Orange-Vaal River system Levels of Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Pt, Au, Hg, Tl, Pb and U were investigated in sediment and fillet tissue (Clarias gariepinus), from sites along the Orange-Vaal River system, South Africa. Sediment sampling sites were chosen up- and downstream of major pollution sources such as mining, industrial and farming areas. The two fish collection sites in the Vaal River were Standerton and Parys and in the Orange River, Boegoeberg and Rooipoort. ICP-MS analysis was done to determine the concentrations the elements. Indices were calculated to describe the quality of the sediment regarding a number of factors: The enrichment factor (Ef) of individual elements evaluated elevation in levels above natural geology whereas the geo-accumulation index (Igeo) determined the degree of pollution by the enrichment levels of the individual elements at each site. The pollution effect of the total mixture of elements at each site was investigated by the elemental contamination index (ECI) and pollution load index (PLI). The ECI is the geometric mean concentrations of elements, while the PLI uses the contamination factor (Cf), that is, how many times the measured concentration is higher than a background value. Ecological risk was determined by calculating the sediment quality guideline index (SQG-I) at each site. The SQG-I is the arithmetic mean of how many times the measured concentration of individual elements at a specific site were higher than a guideline level. In this case, threshold sediment quality guideline values for Australia, the Netherlands, and Canada were used, since South Africa does not have them. In addition, a sediment quality index (SQI) was calculated to incorporate the percentage of elements that did not meet guidelines and the magnitude of exceedance. The bio-accumulation factor (BF) was also calculated between the sediment and the fish. The Igeo and Ef of Se, Ag and Au were the highest at all the sites. The Parys site had the most elements that were enriched to different degrees, but the Rooipoort site had the highest ECI and PLI. The SQG-I indicated that three of the four sites had a moderate chance of posing an ecological risk to its biota. However, the Rooipoort site had a high probability to be toxic to biota. The SQI classified Rooipoort as 'fair' in terms of sediment quality and the rest of the sites as 'good'. The elemental concentrations present within the fish were below the allowed standards for human consumption. Se, Ag, Pt, Au and Hg were the elements that bio-accumulated most in the fish.

Impact of trace metals from past mining on the aquatic ecosystem: A multi-proxy approach in the Morvan (France)

This study seeks to determine to what extent trace metals resulting from past mining activities are transferred to the aquatic ecosystem, and whether such trace metals still exert deleterious effects on biota. Concentrations of Cd, Cu, Pb and Zn were measured in streambed sediments, transplanted bryophytes and wild brown trout. This study was conducted at two scales: (i) the entire Morvan Regional Nature Park and (ii) three small watersheds selected for their degree of contamination, based on the presence or absence of past mining sites. The overall quality of streambed sediments was assessed using Sediment Quality Indices (SQIs). According to these standard guidelines, more than 96% of the sediments sampled should not represent a threat to biota. Nonetheless, in watersheds where past mining occurred, SQIs are significantly lower. Transplanted bryophytes at these sites consistently present higher trace metal concentrations. For wild brown trout, the scaled mass and liver indices appear to be negatively correlated with liver Pb concentrations, but there are no obvious relationships between past mining and liver metal concentrations or the developmental instability of specimens. Although the impact of past mining and metallurgical works is apparently not as strong as that usually observed in modern mining sites, it is still traceable. For this reason, past mining sites should be monitored, particularly in protected areas erroneously thought to be free of anthropogenic contamination.

Integrative assessment of sediment quality in terms of chemical contamination in Jinhae Bay, South Korea

The assessment of sediment quality by considering chemical contaminants is required for the effective management of coastal environments. In this study, complex data sets of heavy metals and organic pollutants were integrated to evaluate sediment quality. Thirty-two target pollutants were quantitatively determined in surface sediments from 80 stations in Jinhae Bay, South Korea. A sediment quality index (SQI) was derived by combining the functions of “scope” (the number of variables that do not meet guideline objectives) and “amplitude” (the magnitude by which these variables exceed the guideline objective). The SQI reflects the spatial gradient and differences in the contamination status with regard to heavy metals and organic pollutants in Jinhae Bay. Fifty-nine out of eighty stations surveyed (74%) were classified as being in “excellent” or “good” condition according to the SQI, and no stations were in a “poor” condition. The mean sediment quality guideline quotient (mSGQq) ranged from 0.06 to 0.31 (from nontoxic to marginally toxic). Acute sediment toxicity leading to amphipod mortality was recorded at 17 stations (21%) of the 80 surveyed, where the mortality rate was slightly over 20%. No significant relationship was observed between sediment toxicity and the concentration of each toxicant or mSQGq.

Integrated Assessment of Heavy Metal Pollution in the Surface Sediments of the Laizhou Bay and the Coastal Waters of the Zhangzi Island, China: Comparison among Typical Marine Sediment Quality Indices

The total concentrations and chemical forms of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in the surface sediments of the Laizhou Bay and the surrounding marine area of the Zhangzi Island (hereafter referred to as Zhangzi Island for short) were obtained and multiple indices and guidelines were applied to assess their contamination and ecological risks. The sedimentary conditions were fine in both of the two studied areas according to the marine sediment quality of China. Whereas the probable effects level guideline suggested that Ni might cause adverse biological effects to occur frequently in some sites. All indices used suggested that Cd posed the highest environmental risk in both the Laizhou Bay and the Zhangzi Island, though Cd may unlikely be harmful to human and ecological health due to the very low total concentrations. The enrichment factor (EF) showed that a substantial portion of Cr was delivered from anthropogenic sources, whereas the risk assessment code (RAC) indicated that most Cr was in an inactive state that it may not have any adverse effect either. Moreover, the results of EF and geoaccumulation index were consistent with the trend of the total metal concentrations except for Cd, while the results of RAC and potential ecological risk factor did not follow the same trend of their corresponding total metal concentrations. We also evaluated the effects of using different indices to assess the environmental impact of these heavy metals.

Environmental and ecological effects of Lake Shihwa reclamation project in South Korea: A review

The Shihwa Coastal Reservoir (SCR) was created to supply agricultural water during the construction of dikes for land reclamation, with this project representing a striking example of policy failure regarding tidal flat reclamation in Korea. After the completion of dike construction in 1994, the water quality inside the SCR drastically deteriorated. As a result, in 1996, the sluice gates were opened to dilute water pollution levels through the physical mixing of seawater from outside and freshwater from inside. Over the last 20 years, the Korean government has invested more than US $ 1.5 billion to recover SCR water quality by improving public sewage treatment systems, which is 2.7 times the cost of the original dike construction. Yet, within the reservoir, water quality has minimally improved, sediment pollution continues to be detected, and anoxic layers have been observed, due to stratification in summer. Severe sedimentary pollution caused by heavy metals and trace organic pollutants originating from the upstream regions of the watershed was evident during the SCR project; however, pollution levels appeared to decrease after seawater circulation. In parallel, the pelagic and benthic communities have also been affected by the deterioration of multiple water and sediment quality indices. While the recent construction of the tidal power plant has significantly increased the volume of seawater circulation, it has not been enough to improve the water quality of the upstream region of the SCR, where the water remains polluted. The SCR project presents a clear example that how incorrect policy leads to the mishandling of both coastal ecosystems and substantial governmental budgets.

AN EXPERIMENTAL EVALUATION OF SUSTAINABLE DRAINAGE SYSTEMS

This paper investigates the behaviour of certain water and sediment quality indicators of a vegetated detention pond system located at Waterlooville, Hampshire, UK. The period of study was 2 years (March 2011-March 2013) with sampling carried out once a month. Statistical analysis was performed using Minitab™. The aim of the study was to examine the changes in quality of various constituents with time and possible linear associations between them. Pond sediments and pond water quality were monitored for a range of variables at each monthly visit. Results indicate that the system demonstrates low levels of pollution while not having a direct impact on the oxygen balance of the receiving water-body. Oxygen demanding substances along with suspended matter and certain metals/elements were found to accumulate in the system with time. Significant linear associations were observed for road salts (containing Na, Cl, Mg) and certain pollutants, suggesting that road salts have a major impact on SuDS water/sediment quality. Sorption characteristics of specific metals were also evaluated by means of adsorption isotherm equations. Three widely used sorption isotherms were employed in this study. It was found that the sorption behaviour of metals is highly variable. This study highlights the dynamic nature of vegetated ponds and the importance of understanding the behaviour of different pollutants for SuDS design.

AN EXPERIMENTAL EVALUATION OF SUSTAINABLE DRAINAGE SYSTEMS

This paper investigates the behaviour of certain water and sediment quality indicators of a vegetated detention pond system located at Waterlooville, Hampshire, UK. The period of study was 2 years (March 2011-March 2013) with sampling carried out once a month. Statistical analysis was performed using Minitab™. The aim of the study was to examine the changes in quality of various constituents with time and possible linear associations between them. Pond sediments and pond water quality were monitored for a range of variables at each monthly visit. Results indicate that the system demonstrates low levels of pollution while not having a direct impact on the oxygen balance of the receiving water-body. Oxygen demanding substances along with suspended matter and certain metals/elements were found to accumulate in the system with time. Significant linear associations were observed for road salts (containing Na, Cl, Mg) and certain pollutants, suggesting that road salts have a major impact on SuDS water/sediment quality. Sorption characteristics of specific metals were also evaluated by means of adsorption isotherm equations. Three widely used sorption isotherms were employed in this study. It was found that the sorption behaviour of metals is highly variable. This study highlights the dynamic nature of vegetated ponds and the importance of understanding the behaviour of different pollutants for SuDS design.

Distribution and accumulation of heavy metals in surface sediments from a subtropical bay affected by the Special Economic Zone, China

The concentrations of nine metals (Cd, Cr, Cu, Ni, Mn, Pb, Zn, Fe, and Al) in surface sediments from 14 sampling sites in Shantou Bay were determined in order to understand current metal levels and spatial distribution due to the rapid development of the Shantou Special Economic Zone. Results showed that metal concentrations in surface sediments varied from 0.31 to 1.74 mg kg(-1) for Cd, 35.98 to 74.19 mg kg(-1) for Cr, 24.43 to 79.24 mg kg(-1) for Cu, 428.45 to 809.87 mg kg(-1) for Mn, 16.91 to 31.51 mg kg(-1) for Ni, 35.59 to 64.84 mg kg(-1) for Pb, 84.91 to 246.51 mg kg(-1) for Zn, 2.93 to 3.93% for Fe, and 5.25 to 9.28% for Al. Although all metal concentrations in sediments meet Chinese National Standard Criteria for Marine Sediment Quality, both enrichment factor (EF) and geo-accumulation index (Igeo) show Pb and Cd pollution existed in the upper and middle bay, and pollution of other metals is also recorded in some sites depending on the sources; river input, sewage discharge, and port activities are the main sources of pollutant to the bay.

Use of enzymatic tools for biomonitoring inorganic pollution in aquatic sediments: a case study (Bor, Serbia)

BackgroundSediment bacterial communities are key players in biogeochemical cycling of elements in the aquatic environment. Copper mining, smelting, and processing operations located in Bor area (Serbia) are major environmental hot spots in the lower Danube Basin and Western Balkans. In the present study, we evaluate the influence of trace element (TE) concentration in sediments and physico-chemical properties of water on sediment microbial communities in water streams adjacent to the Copper Smelter Complex Bor (RTB Bor, Serbia). The degree to which metabolic activities of bacterial biota inhabiting differently polluted sites is inhibited by inorganic pollution were compared using selected enzymatic bioindicators.ResultsCu, Zn, Pb, and As concentrations systematically exceeded the target values for metal loadings in aquatic sediments. Water electrical conductivity (WEC) followed the same pattern of spatial variation, irrespective of season. Interestingly, the most intense enzymatic activity occurred at the reference site although this site showed the greatest TE levels in aquatic sediments. Catalase activity (CA), potential dehydrogenase activity (PDA), actual dehydrogenase activity (ADA), urease activity (UA), and phosphatase activity (PA) in aquatic sediments displayed heterogeneous patterns of spatio-temporal variation. Inorganic pollution greatly affected CA, ADA, and PDA, but much less so UA and PA. Canonical correlation analysis showed that pH and WEC were the strongest determinants of enzymatic activity in bacterial biota, with the latter variable being reversely correlated with the enzymatic indicator of sediment quality (EISQ). The median values of EISQ increased with distance from the major sources of pollution. In addition, it was found that sites with different degrees of inorganic pollution can be appropriately classified by applying cluster analysis to EISQ, TE levels in sediments, and physico-chemical properties of water.ConclusionsBecause EISQ can precisely identify changes in overall enzymatic activity of sediment bacterial communities, this enzymatic bioindicator has a great potential for biomonitoring the current status of inorganic pollution in aquatic ecosystems.

Metal pollution assessment and multivariate analysis in sediment of Anzali international wetland

Anzali international wetland located in southwestern Caspian Sea coast is one of the most important wetlands of Iran from environmental and ecological points of view. Metal concentrations (Cu, Zn, Cr, Fe, Mn, Pb, Ni, Cd, and Li) in 41 surface sediment samples from Anzali wetland were determined. Assessment of ecological risk of sediment samples as well as their degree of contamination revealed considerable ecological risk and moderate degree of contamination in eastern part of the study area. Multivariate statistical analyses were used to identify metal content relationship and their origin. Higher enrichment factors of Cd, Pb, and Zn exhibited probable effects on human activities. Based on sediment quality guidelines (SQGs), moderate potential toxicity levels of sediment samples were identified. A new sediment quality index named sediment toxicity degree was developed based on the results of the multivariate statistical analysis to assess metal toxicity in surface sediments of aquatic systems. Results showed higher sensitivity of the new index (STd) to assess toxic effect of heavy metals on sediments and better capability to differentiate zones with different levels of risk within the study area than that of some other indices such as SQG-Q.