Metal concentrations in the growth bands of Porites sp.: A baseline record on the history of marine pollution in the Gulf of Mannar, India

An appraisal of trace element concentration and environmental risk of sediments: a baseline study of sediments from Arasalar River Estuary, Tamil Nadu, India

A total of 21 surface sediment samples collected from Arasalar River are subjected to sediment texture (sand-silt-clay ratio), trace elements, organic matter, and CaCO3 studies to understand the accumulation dynamics of sediments. To assess the impact of metal pollution in estuarine sediments, the essential parameters should be done by checking the sediment characteristics, spatial distribution of heavy metal sources, sediment dynamics, and geochemical analysis. To evaluate the contamination level of metal pollution, a basic standard reference is required to decipher the values ranging from natural to anthropogenic contribution. From this research analysis, it is observed that the study area predominantly comprises silty sand and sand silty nature. The calcium carbonate content in the sediment is found to be proportional to the presence of shell fragments, whereas the organic matter (OM) is derived from riverine and coastal input which acts as a primary source. The obtained results confessed the average contents (mg/g) for the following selected eight elements in the order of Fe (35249-49068) > Mn (286-519) > Ni (107-279) > Cu (78.30-155.70) > Cr (50-99) > Zn (38.70-91.90) > Pb (39.90-62.40), and Co (12.6-29.1) by using an atomic absorption spectrophotometer (AAS) are utilized for this analysis. Multivariate analysis of heavy metals affirms geogenic sources (weathering of parent rocks) for Fe, Mn, Cr, Co, and Zn, whereas Cu, Ni, and Pb originated from anthropogenic activities (urban and industrial activities). The pollution load index, sediment pollution index, Igeo index, and PERI are categorized as under polluted, low to moderate polluted, and low potential environmental risk variety. Constant inspection and guidance are needed to prevent effluences from various agriculture and industrial activities in the nearby regions. The findings from this research may support and help the government to follow the suitable remediation on the better management of river and coastal areas.

Interannual variation and sources identification of heavy metals in seawater near shipping lanes: Evidence from a coral record from the northern South China Sea

Heavy metal pollution is a serious environmental problem in the marine ecosystem. Thereinto, marine transportation activities have gradually become an important source of heavy metals in seawater. However, the lack of studies on the temporal dynamics of seawater heavy metals in marine shipping areas has hindered our understanding of the sources and transport mechanisms of heavy metals in seawater of hectic shipping waters. Therefore, we investigated the interannual resolution variation of heavy metals in Porites lutea skeletons during the past 32 years under the rapid development of the shipping sector near Weizhou Island from the northern South China Sea. Results show that most heavy metal concentrations with higher coefficients of variation (≥100 %) in the Porites coral skeletons were higher than those in the uncontaminated or less anthropogenic waters. The results of principal component analysis and multiple linear regression showed that the interannual variations of Ni, V, Cr, Co, Zn, Cu, Mn, Fe and Mo were mainly impacted by marine oil extraction and oil spills generated by shipping activities, accounting for 51.58 %. The effect of sea surface temperature accounts for 13.44 %, and controls the interannual variations of Ba and Sr. The effect of industrial pollution accounts for 13.27 %, and explains the interannual variations of Cd and Y. The fuel consumption of marine shipping accounted for 8.76 %, explaining the interannual variations of Pb. The total contribution of anthropogenic activities reached 73.61 %. The interannual variation of heavy metals indicates that hectic marine shipping activities are the dominant cause of Ni, V, Pb, Cr, Co, Zn, Cu, Mn, Fe and Mo input to surface seawater around Weizhou Island. This provided valuable data for understanding the temporal dynamics and potential sources of heavy metals in the marine environment by using coral skeletons as a high-resolution recording vehicle.

Trace metal content in annually banded scleractinian coral 'Porites lobata' across the northern Persian Gulf

Concentrations of trace metals in skeleton growth bands of dominant scleractinian coral 'Porites lobata' in different years were investigated in Kharg and Hebourabi islands in the northern coast of the Persian Gulf. The highest average concentrations of metals respectively were Sr> Mg> Zn> Ba> Cu> U> Ni> Mn> Cr> Co> Pb> V> Cd in Kharg and Sr> Mg> Ba> Cu> U> Ni> Zn> Mn> Cr> Co> V> Pb> Cd in Hendourabi. The coefficient of variation percentages (CV%) of Cr, Mn, Zn, Ba, and Pb in Kharg and Cu and Ba in Hendourabi were more than 50%. Results of PCA analyses revealed that the levels of trace metals in Kharg were defined by three principle components: the first component (Mn, V, Pb, Zn, Ni and half of Mg, Cr and Co) corresponding to the past regional military conflicts and oil pollution, the second component (Sr, U, and Mg) corresponding to sea surface temperature (SST) changes, and the third component (Cr and Co) corresponding to other factors. The results of PCA analyses revealed that trace metals in Hendourabi were defined by two principle components including the first component (Co, Ni, Cr, Mn, and half of Ba) corresponding to annual precipitation changes and the second component (U, Zn, and Ba) corresponding to coastal constructions. The results showed that trace metal contamination in Kharg is higher than those of Hendourabi as a result of the oil exploration-related activities and war.

Baseline distributions and sources of polycyclic aromatic hydrocarbons (PAHs) in reef-associated sediments of Vembar group of Islands, Gulf of Mannar, India

The study aims to investigate the source and concentration of PAH fractions in the reef sediments of the Vembar group of Islands, Gulf of Mannar, India. The concentration of PAHs ranged from 0.36 to 15.98 ng/g. The reef environment was less contaminated with low-molecular-weight PAH fractions. The accumulation of the LMW-PAH fraction was very less, whereas the HMW fraction was derived from pyrolytic sources. The level of low and high molecular weight PAHs was lower than the level of Effective Range Median (ERM) and Effective Range Low (ERL).The calculated total TEQ value ranged from ND to 10.24 ng/g in the reef sediments.

Heavy metal concentration in reef-associated surface sediments, Hare Island, Gulf of Mannar Marine Biosphere Reserve (southeast coast of India): The first report on pollution load and biological hazard assessment using geochemical normalization factors and hazard indices

In this study, reef-associated surface sediment samples were collected from Hare Island in the Gulf of Mannar Marine Biosphere Reserve, Bay of Bengal and analyzed for heavy metal concentration. The sediment quality was evaluated based on the geochemical, biological, and ecological hazard indices. The mean concentration of heavy metals in the sediments ranged from 0.02 (Cd) to 26,262.87 mg/kg (Fe). Except for Cd and Hg, all other elements were found to be below the sediment quality guidelines and contamination level. The biological and ecological hazard (BEHI) revealed that most sediment samples (80%) fell under the low-risk category with 9% probability of toxicity to the marine flora and fauna. The overall contamination level of heavy metals in Hare Island suggested that the sediment could be grouped under low-risk category. Hence, this study recommends the need for a routine monitoring program in this region to maintain a clean and sustainable ecosystem in future.

Microplastic and heavy metal distributions in an Indian coral reef ecosystem

The current study focuses on the occurrence and characteristics of microplastics (MPs) and spatial distribution and pollution status of heavy metals in the water and sediments of the coral reef ecosystems associated with the Tuticorin and Vembar groups of islands in the Gulf of Mannar, southeast India. Mean abundance of MPs varies from 60 ± 54 to 126.6 ± 97 items/L in water and from 50 ± 29 to 103.8 ± 87 items/kg in sediment. Water and sediment samples from the Tuticorin islands contain higher MP concentrations than the Vembar islands. The highest MP were observed in the mainland samples, while MP distributions in the shoreward direction i.e. towards the islands closely reflect those of the mainland (p < 0.05). Polyethylene is the most common polymer, with fibers (1-3 mm) being the most abundant form in water and fragments (3-5 mm) being the most abundant in sediment. Pollution indices such as enrichment and contamination factors indicate moderate contamination of sediments by Zn, Hg, Cd, Pb and Ni. Heavy metal associated with MPs are greater than those in sediments, and this indicates that MP may be a source of metal pollution or that metals from the sediment preferentially partition to MPs. SEM analysis highlights the presence of cracks, protrusions and depositions on the surface of many MPs, indicating partial degradation. EDAX frequently showed the presence of Zn, Cd, Pb, Ni and Fe associated with MP surfaces. This study offers an insight into the level of MPs and associated elements that filter feeding corals in the region are exposed to current.

Speciation and risk assessment of selected trace metals in bottom sediment of coral reef ecosystems of the Persian Gulf

To evaluate the hazard assessment of anthropogenic activities on coastal ecosystems, fractionation and bioaccumulation of trace metals were carried out for sediment and coral samples of three distinct habitats including petroleum exploration area of Kharg, the rural harbor of Chirouyeh, and unpopulated area of Hendorabi. Fractionation results suggested that Ni (~ 51%), Pb (~ 49%), and V (~ 45%) in Kharg; Ni (~ 46%), Pb (~ 84%), and Zn (~ 47%) in Chirouyeh; and Cd (~ 51%) in Hendorabi were the predominant metals in the non-resistant fractions of the sediment samples. Risk Assessment Code (RAC), individual contamination factor (ICF), and global contamination factor (GCF) were derived. The highest relative risk for Cd, Cu, and Ti was observed in Kharg, whereas the highest relative risk for Ni, Pb, V, and Zn was recorded in Chirouyeh. The lowest risk for almost all of the trace metals was observed in Hendorabi. Biota-sediment accumulation factor (BSAF) values of coral samples revealed that species examined in the present study are reliable biomonitors for Cd, Ni, Pb, and Zn contamination. Principal component analysis (PCA) and Pearson's correlation coefficient (PCC) suggested that Pb, Ni, and Zn can be considered the main pollutants of the Persian Gulf which originated mainly from petroleum industries. Furthermore, the metal uptake rates of coral samples seemed to be dependent on bioabsorption pathways and coral species. Overall, the present work constitutes a good basis for further studies on trace metal fractionation, risk assessment, and source apportionment in the Persian Gulf, which could contribute to more effective decisions for reducing the anthropogenic trace metal pollution.

A baseline study on trace element based sediment pollution and potential ecological risk of reef sediments of Musal, Manoli and Manoli putti Islands, Gulf of Mannar, India

The aim of the present study is to assess the baseline level of the trace element, sediment pollution and potential ecological risk of reef associated sediments of Musal, Manoli and Manoli putti Islands, Gulf of Mannar, India. The grain size distribution of the sediments is chiefly controlled by corals and broken shell debris. The distribution of lithoclastic fractions and element concentration are most probably derived from longshore sediment transport and fluvial process from nearby mainland. The enrichment of organic matter is chiefly controlled by mangrove litters and sea grasses. The concentration of lead in the marine sediments is subjected to sediment matrix, vicinity of the local pollutant sources and distance from the mainland coast. The ecological risk assessment clearly reveals that the sediments belong to the low risk category.

A baseline study on the concentration of trace elements in the surface sediments off Southwest coast of Tamil Nadu, India

Forty two surface sediment samples were collected in order to document baseline elemental concentration along the Southwest coast of Tamil Nadu, India. The elements detected were Manganese (Mn), Zinc (Zn), Iron (Fe), Copper (Cu), Nickel (Ni) and Lead (Pb). The concentration of Fe and Mn was primarily controlled by the riverine input. The source of Pb and Zn is attributed to leaded petrol and anti-biofouling paints. The calculated index (EF, Igeo and CF) suggests that the sediments of the study area are significantly enriched with all elements except Pb. The contamination factor showed the order of Mn>Zn>Fe>Cu>Ni>Pb. The sediment pollution index (SPI) revealed that the sediments belonged to low polluted to dangerous category. The correlation matrix and dendrogram showed that the elemental distribution was chiefly controlled by riverine input as well as anthropogenic activity in the coast.

Geospatial risk assessment and trace element concentration in reef associated sediments, northern part of Gulf of Mannar biosphere reserve, Southeast Coast of India

Fifty two surface sediments were collected from the northern part of the Gulf of Mannar biosphere reserve to assess the geospatial risk of sediments. We found that distribution of organic matter and CaCO₃ distributions were locally controlled by the mangrove litters and fragmented coral debris. In addition, Fe and Mn concentrations in the marine sediments were probably supplied through the riverine input and natural processes. The Geo-accumulation of elements fall under the uncontaminated category except Pb. Lead show a wide range of contamination from uncontaminated-moderately contaminated to extremely contaminated category. The sediment toxicity level of the elements revealed that the majority of the sediments fall under moderately to highly polluted sediments (23.07-28.84%). The grades of potential ecological risk suggest that predominant sediments fall under low to moderate risk category (55.7-32.7%). The accumulation level of trace elements clearly suggests that the coral reef ecosystem is under low to moderate risk.

Trace element concentrations in reef associated sediments of Koswari Island, Gulf of Mannar biosphere reserve, southeast coast of India

Extensive field work was conducted in order to assess the sediment pollution level and potential ecological risk on coral reef ecosystem. Thirty three surface sample was collected using grid sampling technique. The calcium carbonate and organic matter were primarily controlled by the distribution of coral rubbles and seagrass meadows. The concentration of trace elements is higher than the crustal average in few locations and the same result was derived from index calculations. However, the significant concentration of lead was observed throughout the study area. The elevated level of lead is probably due to coal incinerating power plants, and confluence of urban runoff from the nearby coastal areas. Based on the sediment pollution index, the majority of the sediments belongs to highly polluted to dangerously polluted category. The ecological risk indicates that the sediments are under low risk to moderate risk category and this result was proved by correlation analysis.

Spatial risk assessment and trace element concentration in reef associated sediments of Van Island, southern part of the Gulf of Mannar, India

Forty eight surface sediment samples were collected from the vicinity of Van Island in order to assess the sediment pollution level and potential ecological risk on coral reef ecosystem. The analytical and correlation results indicate a distribution of elements is chiefly controlled by the CaCO₃ and OM. The enrichment factor and geoaccumulation index show the elevated level of Pb in the surface sediments is due to application of lead petrol and coal incinerating power plants. The sediment pollution index reveals that majority of the sediments falling under highly polluted sediment category (35.4%) followed by moderately polluted (25%) and dangerous sediment category (14.58%). The potential ecological risk suggests that nearly 66.6% of the samples falling under the low risk category, moderate risk category (20.8%) followed by considerable risk category (8.33%) and very high risk category (4.1%). The accumulation level of trace elements clearly suggests that the coral reef ecosystem is under low risk.

Assessment of trace element accumulation in surface sediments off Chennai coast after a major flood event

The present study was conducted to assess the trace element concentration in marine surface sediments after major flood event of Chennai metropolis, India. Thirty surface samples were collected from off Chennai coast. Trace elements, organic matter, CaCO₃, sand-silt-clay and C/N ratios were studied to understand the accumulation dynamics on sediments. The elemental concentration, calcium carbonate and OM distribution suggest that they are derived from urban runoff and transported through Adyar and Cooum Rivers. The enrichment factor reveals that the sediments are enriched by Pb, Cu, Zn, Cr, Co, Ni followed by Fe. The observed Igeo value shows that the samples are contaminated by Pb, Cu and Zn. The elemental concentration of the surface sediments is low when compared to other coastal region except Pb. The elevated level of Pb in the surface sediments is probably due to migration of contaminated urban soil from industrial and transportation sectors into marine environment.