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

Trace element concentration and Al/Fe ratio in sediments of the South East Mediterranean Sea

The heavy metals (HMs) concentration range, the metal/Al and metal/Fe value were determined in the sediment in order to evaluate the correlation coefficient of HMs at the regions of South East Mediterranean Sea, Cyprus. The results showed that the mean concentrations of the HMs in the sediment samples followed the order Al > Fe > Mn > Cr > Ni > Zn > Cu > Pb > As>Hg, respectively. The pollution indices of contamination factor (CF), geoaccumulation index (Igeo), enrichment factor (EF), and soil pollution index (SPI) were calculated. The Igeo, CF and EF values for Cu were obtained moderately to strongly polluted, moderate contamination and moderately severe enrichment, respectively. The remaining elements indicated unpolluted or low contamination results. Also, SPI indicated a low level of contamination for the all of the metals. The cluster analysis of data set indicates that the HMs are separated with 50% similarity in two categories of Al category (As, Pb, Cr, Ni) and Fe category (Mn, Zn, Cu, Hg).

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.

Seasonal variations of trace metals from water and sediment samples in the northern Bay of Bengal

We aimed to determine the temporal variation of trace metals concentrations in surface water and surface sediment samples at Kutubdia Channel, Bangladesh. Trace metals of samples were detected using energy dispersive X-ray fluorescence (Energy-dispersive X-ray spectroscopy) method. The lowest concentration of metals was found in water samples during post-monsoon season and the highest during pre-monsoon season (Cu: 0.030 ± 0.001 μg/L in pre-monsoon and 0.026 ± 0.002 μg/L in post-monsoon, Zn: 0.087 ± 0.003 μg/L in pre-monsoon and 0.073 ± 0.002 μg/L in post-monsoon, Fe: 0.080 ± 0.001 μg/L in pre-monsoon and 0.055 ± 0.001 μg/L in post-monsoon). In contrast, metal concentration in surface sediment samples were higher in post-monsoon than in pre-monsoon season i.e. Cr 11 mg/kg in pre-monsoon and 12 mg/kg in post-monsoon, Mn 571 mg/kg in pre-monsoon and 606 mg/kg in post-monsoon, As (8 mg/kg in pre-monsoon and 10 mg/kg in post-monsoon, Pb (22 mg/kg in pre-monsoon and 24 mg/kg in post-monsoon, and Fe 2317 mg/kg in pre-monsoon and 2435 mg/kg in post-monsoon. We found a spatial gradient of high to medium to low in trace metal concentration from river to river mouth to offshore area. Considering the sources of metals, land erosion by waves and tidal action, an influx of water and sediment from the surrounding rivers, agricultural waste, industrial effluent and sewage are the most likely sources of metal pollution in the study area. We conclude that proper management strategies should be adopted to control the pollution and conserve the ecosystem health.

Microplastic presence in commercial marine sea salts: A baseline study along Tuticorin Coastal salt pan stations, Gulf of Mannar, South India

The present baseline research infers that the salts present in the sea may contain microplastics (MPs), as the seawater is contaminated due to a number of anthropogenic activities. Herein, 25 types of sea salt samples were collected from salt pans located in the Tuticorin coastal region. The MPs present in the samples were separated and identified by various methods such as handpicking, visual classification, and micro-Fourier transform infrared spectroscopy (μ-FT-IR) and atomic force microscopy (AFM). The MPs that measured less than 100 μm formed the major part of the salts, accounting to 60% of the MPs among the total pollutants. The MPs that were found in abundance in the sea salts were polypropylene, followed by polyethylene, nylon, and cellulose. This study was conducted in salt pan areas and demarcated the percentage of MPs present in sea salts. Table salt, which is a prime edible commodity, was found to be contaminated with MPs through polluted seawater, which poses a threat to public health.

Novel hybrid methods applied for spatial prediction of mercury and variable selection of trace elements in coastal areas of USA

This study was concerned with spatial analysis of mercury (Hg) in sediment samples of the USA coastal areas using more accurate and stable hybrid approaches compared to the conventional methods. An ensemble of simulated annealing along with least angle regression (SA-LAR) was applied for selection of predictors in spatial analysis. The latest algorithm was efficient with resultant RMSE and R² of 0.066 and 0.705 compared to 0.099 and 0.571 for the traditional method of recursive feature elimination (RFE) approach. Using Cu, Pb and As as selected variables, it was tried to improve the spatial forecasting of Hg with either a hybrid of generalized boosted regression and ordinary kriging (GBROK) or inverse distance weighting (GBRIDW). According to the results, the variance explained by cross validation (VECV) was improved from 7.52% and 9.76% for IDW and OK to 40.41% and 41.94% for the GBRIDW and GBROK methods, respectively.

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 preliminary study on coastal debris in Nallathanni Island, Gulf of Mannar Biosphere Reserve, Southeast coast of India

Nine sampling stations were fixed to carry out the preliminary investigation on coastal debris from Nallathanni island, Gulf of Mannar Biosphere Reserve, Southeast coast of India. The coastal debris were separated and identified using hand picking, visual identification and microscopic studies. The coastal areas of the study region were less dominated by micro plastic contamination. The coastal debris was dominated by polyethylene bottles and fibrous fishnet materials. The distribution of the coastal debris along the coastal region is chiefly controlled by winnowing action of sea waves and Aeolian action along the berm region.

Sediment textural characteristics and elemental distribution in the core sediments, Pullivasal and Kurusadai Island, Gulf of Mannar, Southeast coast of India

Two core samples were collected in order to assess the textual characteristics and elemental distribution of the sediments, from the lagoonal environment of Pullivasal and Kurusadai island, Gulf of Mannar, Southeast coast of India. The distribution of the organic matter and calcium carbonate is chiefly controlled by the coral debris, shell fragments and mangrove litters. The elemental distribution is controlled by natural process and other trace elements are controlled by anthropogenic land based activities.