A baseline study on elemental concentration and potential ecological risk status of the surface sediments of Ashtamudi Lake, south west coast of India

Microplastic contamination in Ashtamudi Lake, India: Insights from a Ramsar wetland

Estuaries function as temporary storage sites for plastic debris, influencing the distribution of microplastics (MPs) across ecosystems. This research delves into the presence of MPs in the water, sediment, fish, and shellfish of Ashtamudi Lake, a Ramsar wetland with brackish water located on the southwest coast of India. Given the lake's significance in supporting the livelihoods of numerous fishers and acting as a vital source of fishery resources for both local consumption and export, examining the contamination of the system by MPs becomes particularly pertinent. The highest percentage composition of MPs was found in macrofauna at 60.6% (with fish at 19.6% and shellfish at 40.9%), followed by sediment (22.8%) and water (16.7%). The primary types of MPs identified in all samples were fibers (35.6%), fragments (33.3%), and films (28%), with beads being the least represented at 3.03%. ATR-FTIR and Raman spectra analysis identified five polymers from shellfish (polypropylene, polyethylene, polystyrene, nylon, and polyvinyl chloride), five from fish guts (nylon, polypropylene, polyethylene, polyurethane, and polysiloxane), four in sediment (polypropylene, polyethylene, nylon, rayon), and four in water samples (polypropylene, polyethylene, nylon, and polystyrene). SEM-EDAX analysis of MPs obtained from the samples revealed degradation and the presence of inorganic elements such as Na, Mg, Al, Si, S, K, Cl, P, and Ca, as well as heavy metals like Pb, Mo, Rh, Pd, Ti, and Fe. The existence of these plastic polymers and heavy metals in microplastic samples poses a threat to vulnerable biota; people consume contaminated fish and shellfish, underscoring the importance of monitoring MPs in lake water. This investigation of MPs in Ashtamudi Lake highlights the system's susceptibility to plastic pollution and the bioavailability of smaller MPs to aquatic organisms. Identified sources of MPs in the lake include fishing and aquaculture activities, sewage pollution, improper solid waste management in lake watersheds, and unsustainable tourism. Upstream and downstream management interventions are recommended to address MP pollution in Ashtamudi Lake.

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.

Occurrence, distribution and sources of phthalates and petroleum hydrocarbons in tropical estuarine sediments (Mandovi and Ashtamudi) of western Peninsular India

The present study provides baseline information on the concentration levels, distribution characteristics and pollution sources of environmental contaminants, such as phthalic acid esters (PAEs or phthalates) and petroleum hydrocarbons in surface sediments of the tropical estuaries (Mandovi and Ashtamudi) from western Peninsular India. Total PAEs (∑₅PAEs), hopanes, steranes and diasteranes concentrations from Ashtamudi estuary ranged from 7.77 to 1478.2 ng/g, n.d.-363.2 ng/g, n.d.-121.5 ng/g and n.d.-116.6 ng/g, respectively. Likewise, PAEs (∑₆PAEs), steranes and diasteranes concentrations from Mandovi estuary ranged from 60.1 to 271.9 ng/g, 2.33-40.1 ng/g and 2.28-23.0 ng/g, respectively. The PAEs comprising di-isobutyl phthalate (DIBP), dibutyl phthalate (DBP), an isomer peak for DBP, di(2-ethylhexyl) phthalate (DEHP), di-isononyl phthalate were dominant in Ashtamudi estuary sediments, while PAEs including diethyl phthalate, DIBP, DBP and its isomer, DEHP, di(2-ethylhexyl) terephthalate were detected in the Mandovi sediment samples. The results of this study show an insignificant correlation of TOC with PAEs, and indicates that the varying spatial distributions of the PAEs in both the estuaries can be the result of discharge sources. The higher concentration of PAE congeners was noticed in Ashtamudi, a Ramsar wetland site, that can be attributed to land-based plastic waste. The petroleum biomarkers were abundantly present in Mandovi estuary due to anthropogenic activities such as boating and spillage from oil tankers. The findings of the present study will serve as a reference point for future investigation of organic contaminants in Indian estuaries, and calls for attention towards implementing effective measures in controlling the pervasion of the PAEs and petroleum biomarkers.

Accumulation potential of heavy metals at different growth stages of Pacific white leg shrimp, Penaeus vannamei farmed along the Southeast coast of Peninsular India: A report on ecotoxicology and human health risk assessment

This study compared the heavy metal concentration in water, sediment, and shrimp at different growth stages of culture and subsequently evaluated the ecotoxicological and human health risk status. Total trace element concentration in the water, sediment and shrimp ranged from not detected (ND) (Hg) to 91.05 (Fe) μg/L, 0.01 (Hg) to 19, 246.33 (Fe) mg/kg, and ND (Hg) to 13.98 (Fe) mg/kg, respectively. Toxic metals such as, Cd, Hg, and Pb in shrimps ranged from ND to 2.11 mg/kg, ND to 0.158 mg/kg, ND to 0.088 mg/kg, and ND to 0.469 mg/kg, respectively. Toxic heavy metals at all the growth stages of shrimps (days of culture (DOC)-01 to DOC-90) were found below the maximum residual limit (MRL) of 0.5 mg/kg set by the European Commission (EC). Similarly, Cu, Zn, and As concentrations in shrimp were also far below the MRLs of 30 mg/kg, 100 mg/kg, and 76 mg/kg set by the World Health Organization and Food Safety and Standard Authority of India, respectively. The concentration of heavy metals increased from DOC-01 to DOC-90 and was positively correlated with the length and weight of the shrimps (p < 0.05). The risk assessment was estimated for both Indians and Americans and found no carcinogenic (lifetime cancer risk (LCR) < 10^-4) and non-carcinogenic (THQ and TTHQ<1) health risks through consumption of shrimp cultured in this region. The hazard quotient (HQ_dermal < 1), hazard index (HI < 1), and LCR (<10^-4) values of the heavy metals indicated that the dermal absorption might not be a concern for the local fishermen and marine fish/shrimp farmworkers. Water and sediment quality indices were applied to assess the surface water and sediment quality, and their results were found nil to low levels of heavy metal contamination at all the sampling sites. All heavy metals studied in sediments were < effect range low (ERL) and < threshold effect level (TEL), indicating no adverse biological effects on aquatic organisms. Therefore, regular monitoring of the shrimp aquaculture system throughout the crop will provide evidence of heavy metals bioaccumulation in shrimps. This research will provide baseline data to help farmers establish the optimal aquaculture practices and regulatory authorities to formulate legislation and strategies to reduce heavy metal biomagnification in shrimps from farm to fork.

Assessment of water quality in a tropical ramsar wetland of southern India in the wake of COVID-19

The novel SARS-CoV-2 virus influenced the world severely in the first half of 2020 caused shut down of all kind of human activities. It is reported that a word-wide ecological improvement in terms of air quality and water quality during this lock down period. In the present study, an attempt has been made to study the progression in water quality through examining suspended particulate matter using remote sensing data in a tropical Ramsar site viz, Asthamudi Lake in Southern India. The change in spectral reflectance of water along the study area were analyzed and suspended particulate matter (SPM) is estimated from Landsat 8 OLI images. A comparison analysis of pre and co lockdown periods reveal that the concentration of SPM values during lockdown (mean SPM 8.01 mg/l) is lower than that of pre-lockdown (10.03 mg/l). The time series analysis of last five-year data from 2015 to 2020 also shows an average decrease of 43% in SPM concentration during lockdown period compared to the last five-year average value of 9.1 mg/l. The reasons for improvement of SPM in water quality during the lockdown period in April-May 2020 was discussed, in terms of the role of anthropogenic activities and strategies for the sustainable management of coastal ecosystems and water resources in the Asthamudi Lake were also presented.

Distribution, sources, and ecological risks of potentially toxic elements in the Laizhou Bay, Bohai Sea: Under the long-term impact of the Yellow River input

Potentially toxic element (PTE) contamination is a common environmental issue in offshore regions worldwide. Water and sediment samples were collected from the Yellow River downstream and adjacent Laizhou Bay to investigate the residues, sources, and ecological risks of 11 typical PTEs (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sc, V, and Zn). The results indicated that the concentrations of PTEs in the sediments decreased from the Yellow River Estuary to the inner Laizhou Bay under the long-term effect of the Yellow River input. Principal component analysis (PCA) identified three potential sources: natural origins, coastal anthropogenic activities (e.g., oil exploration and steel refining), and marine production (e.g., marine aquaculture and transportation). Among the PTEs, Cd was the most significant contaminant, with a contamination factor (CF) of 2.06 ± 0.78. Furthermore, Cd was the most sensitive factor used in evaluating the overall ecological risk using Monte Carlo analysis, with a contribution of up to 96%. Although the overall contamination and risk levels were low in the bay, a higher pollution load index (PLI) and risk index (RI) adjacent to the Yellow River Estuary indicated that the Yellow River remained the primary contributor to the PTEs contamination in the bay.

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.