Dietary intake of trace elements from commercially important fish and shellfish of Thoothukudi along the southeast coast of India and implications for human health risk assessment

Bioaccumulation of Arsenic, Cadmium, Chromium, Cobalt, Copper, and Zinc in Uroteuthis edulis from the East China Sea

In this study, the concentrations of trace elements (TEs) in Uroteuthis edulis caught from the East China Sea were determined. There were significant differences between TE concentrations in different body parts. Cu, Zn, and Cd were the most concentrated in the digestive glands and the concentrations of Cr and Co were highest in the gills. No significant differences in concentrations were shown between these tissues. In the four tissues analyzed, the mantle recorded the highest proportion of elemental load, while the digestive glands and gills had the lowest proportions. After maturity, TEs in the mantle showed no significant differences. In the digestive gland, the concentrations of all elements, except Zn, were significantly increased. The gonads illustrated apparent increases in the concentrations of Cr, Cu, and As. In the gills, the concentrations of Co and As were markedly increased.

Distribution and bioaccumulation of trace elements in two Cyprinidae fish species in the Indus river, Pakistan, including the impact of hydraulic structure on macroinvertebrates' biodiversity

The concentration of trace elements (chromium, lead, zinc, copper, manganese, and iron) was determined in water, sediment and tissues of two Cyprinidae fish species - Labeo rohita and Tor putitora - collected from the eight sampling stations of Indus River in 2022 for four successive seasons (autumn, winter, spring, summer), and also study the present condition of macroinvertebrates after the construction of hydraulic structure. The obtained results of trace element concentrations in the Indus River were higher than the acceptable drinking water standards by WHO. The nitrate concentration ranges from 5.2 to 59.6 mg l-1, turbidity ranges from 3.00 to 63.9 NTU, total suspended solids and ammonium ions are below the detection limit (<0.05). In the liver, highest dry wt trace elements (μg/g) such as Cr (4.32), Pb (7.07), Zn (58.26), Cu (8.38), Mn (50.27), and Fe (83.9) for the Labeo rohita; and Tor Putitora has significantly greater accumulated concentration (Cr, Pb, Zn, Cu, Mn, Fe) in muscle and liver than did Labeo rohita species. Additionally, lower number of macroinvertebrates were recorded during the monsoonal season than pre-monsoon and post-monsoon. Local communities surrounded by polluted environments are more probably to consume more fish and expose them to higher concentrations of toxic trace elements (lead and copper). The findings also provide a basis for broader ecological management of the Indus River, which significantly influenced human beings and socioeconomic disasters, particularly in the local community.

Bioaccumulation and health risk assessment of trace elements in Tilapia (Oreochromis mossambicus) from selected inland water bodies

The presence of toxic trace elements (TEs) has resulted in a worldwide deterioration in freshwater ecosystem quality. This study aimed to analyze the distribution of TEs, including chromium (Cr), nickel (Ni), arsenic (As), mercury (Hg), cadmium (Cd), and lead (Pb), in water, sediment, and organs of Tilapia (Oreochromis mossambicus) collected from selected inland water bodies in Tamil Nadu, India. The water samples exhibited a range of concentrations for TEs: Cr varied from 0.014 to 5.193 µg/L, Ni ranged from 0.283 to 11.133 µg/L, As ranged from 0.503 to 1.519 µg/L, Cd from 0.001 to 0.616 µg/L, and Pb ranged from non-detectable (ND) to 6.103 µg/L. The concentrations of TEs in sediment were found to vary within the following ranges: 5.259 to 32.621 mg/kg for Cr, 1.932 to 30.487 mg/kg for Ni, 0.129 to 0.563 mg/kg for As, 0.003 to 0.011 mg/kg for Cd, ND to 0.003 mg/kg for Hg, and 0.404 to 1.575 mg/kg for Pb. The study found that the accumulation pattern of TE in fishes across all selected areas was liver > bone > gill > muscle. The organs had TE concentrations of Cr (ND-0.769 mg/kg), Ni (ND-1.053 mg/kg), As (0.002-0.080 mg/kg), Pb (ND-0.411 mg/kg), and Hg (ND-0.067 mg/kg), which was below the maximum residual limit prescribed by EC and FSSAI. The bioconcentration factor (BCF) of TEs exhibited a greater magnitude in comparison with the biota-sediment accumulation factor due to the higher concentration of TEs in fish and lower level in water. The assessment of both carcinogenic and non-carcinogenic risks suggests that the consumption of Tilapia from the study region does not pose any significant risks.

Metals concentration and human health risk assessment in some fish species from the southern Caspian Sea

The main objectives of this study were to determine the mercury concentration in four species of valuable and widely consumed fish from the Caspian Sea, to assess the health risk due to their consumption. The average mercury concentrations for Chelon saliens, Chelon auratus, Acipenser persicus and Acipenser stellatus were 32.72, 39.51, 166.87 and 81.87 μg g-1 dw, respectively. There were correlations between the mercury concentrations in the muscle of Chelon saliens and morphological parameters, but these correlations were not observed in Chelon auratus. Our comparison of the mercury values obtained in all the samples with the recommended international standards, as well as the Hazard Quotients values, indicated that there is no potential risk for the health of consumers due to exposure to mercury from consuming these fish.

Bioaccessibility of toxic heavy metals/metalloids in edible seaweeds: Exposure and health risk assessment

This study assesses the health risk due to heavy metals/metalloids (HMs/Ms) in edible seaweeds (Caulerpa racemosa, Kappaphycus alvarezii, and Ulva lactuca) through an in vitro bioaccessibility study. The percentage of bioabsorbed HMs/Ms in unprocessed and processed C. racemosa, U. lactuca, and K. alvarezii ranged from 3 % to 46 %, 3 % to 42 %, and 3 % to 40 %, respectively. The levels of HMs/Ms in seawater, sediment, and seaweeds were below the levels recommended by the European Commission (EC) and World Health Organization/Food and Agriculture Organization (WHO/FAO). The maximum accumulation of HMs/Ms was found during monsoons and post-monsoon seasons, and Cd, Pb, Hg, Cr, As, and Pb were predominant in all the samples. Tukey's post hoc test and t-test confirmed that thermal processing significantly reduced HMs/Ms in seaweeds. On the basis of the bioabsorption of HMs/Ms, the TTHQ values were found to be < 1, and the LCR values were within the acceptable limit (10-06 to 10-04), indicating no carcinogenic risks through seaweeds.

Biomonitoring of mercury and selenium in commercially important shellfish: Distribution pattern, health benefit assessment and consumption advisories

This study aims to explore the concentrations of Se and Hg in shellfish along the Gulf of Mannar (GoM) coast (Southeast India) and to estimate related risks and risk-based consumption limits for children, pregnant women, and adults. Se concentrations in shrimp, crab, and cephalopods ranged from 0.256 to 0.275 mg kg-1, 0.182 to 0.553 mg kg-1, and 0.176 to 0.255 mg kg-1, respectively, whereas Hg concentrations differed from 0.009 to 0.014 mg kg-1, 0.022 to 0.042 mg kg-1 and 0.011 to 0.024 mg kg-1, respectively. Se and Hg content in bamboo shark (C. griseum) was 0.242 mg kg-1 and 0.082 mg kg-1, respectively. The lowest and highest Se concentrations were found in C. indicus (0.176 mg kg-1) and C. natator (0.553 mg kg-1), while Hg was found high in C. griseum (0.082 mg kg-1) and low in P. vannamei (0.009 mg kg-1). Se shellfishes were found in the following order: crabs > shrimp > shark > cephalopods, while that of Hg were shark > crabs > cephalopods > shrimp. Se in shellfish was negatively correlated with trophic level (TL) and size (length and weight), whereas Hg was positively correlated with TL and size. Hg concentrations in shellfish were below the maximum residual limits (MRL) of 0.5 mg kg-1 for crustaceans and cephalopods set by FSSAI, 0.5 mg kg-1 for crustaceans and 1.0 mg kg-1 for cephalopods and sharks prescribed by the European Commission (EC/1881/2006). Se risk-benefit analysis, the AI (actual intake):RDI (recommended daily intake) ratio was > 100%, and the AI:UL (upper limit) ratio was < 100%, indicating that all shellfish have sufficient level of Se to meet daily requirements without exceeding the upper limit (UL). The target hazard quotient (THQ < 1) and hazard index (HI < 1) imply that the consumption of shellfish has no non-carcinogenic health impacts for all age groups. However, despite variations among the examined shellfish, it was consistently observed that they all exhibited a Se:Hg molar ratio > 1. This finding implies that the consumption of shellfish is generally safe in terms of Hg content. The health benefit indexes, Se-HBV and HBVse, consistently showed high positive values across all shellfish, further supporting the protective influence of Se against Hg toxicity and reinforcing the overall safety of shellfish consumption. Enhancing comprehension of food safety analysis, it is crucial to recognize that the elevated Se:Hg ratio in shellfish may be attributed to regular selenoprotein synthesis and the mitigation of Hg toxicity by substituting Se bound to Hg.

Selenium and mercury concentration, Se/Hg molar ratio and risk-benefit assessment of marine fish consumption: Human health risks and protective role of Se against Hg toxicity

This study aimed to explore the concentrations of Se and Hg in marine fish along the Gulf of Mannar (southeast coast of India) and to assess related risks and risk-based consumption limits for children, pregnant women, and adults. Se concentrations in pelagic and benthic fish ranged from 0.278 to 0.470 mg/kg and 0.203 to 0.294 mg/kg, respectively, whereas Hg concentrations ranged from 0.028 to 0.106 mg/kg and 0.026 to 0.097 mg/kg, respectively. Se and Hg contents in demersal fish (Nemipterus japonicus) were 0.282 and 0.039 mg/kg, respectively. The lowest and highest Hg concentrations in pelagic fish were found in Scomberomorus commersoni and Euthynnus affinis whereas the lowest and highest Se concentrations in benthic fish were found in Scarus ghobban and Siganus javus. Se concentrations in marine fishes were found in the following order: pelagic > demersal > benthic whereas Hg concentrations were found in the following order: pelagic > benthic > demersal. The presence of Se in fish was positively correlated with trophic level (TL) and size whereas that of Hg was weakly correlated with TL and habitat and negatively correlated with size. Se risk-benefit analysis, the AI/RDI (actual intake/recommended daily intake) ratio was > 100 % and the AI/UL (upper limit) ratio was < 100 %, indicating that all fish have sufficient levels of Se to meet daily requirements without exceeding the UL. Hg level was below the maximum residual limit (MRL) of 0.5 mg/kg for most fish but it was 1 mg/kg in E. affinis and Lethrinus lentjan. The target hazard quotient (THQ < 1) and hazard index (HI < 1) imply that the consumption of fish poses no noncarcinogenic health risks. However, all examined fish had a mean Se/Hg molar ratio > 1, indicating that human intake of fishwas rather safe relative to Hg content. Health benefit indexes (Se-HBV and HBVse) with high positive values in all fish supported the protective effect of Se against Hg toxicity, suggesting the overall safety of fish consumption. The high Se/Hg ratio in fish could be attributed to the replacement of Se bound to Hg, thereby suppressing Hg toxicity and maintaining normal selenoprotein synthesis. This insight is useful for a better understanding of food safety analysis.

Assessment of heavy metals and environmental stress conditions on the production potential of polyunsaturated fatty acids (PUFAs) in indigenous microalgae isolated from the Gulf of Mannar coastal waters

The present study evaluated the effects of heavy metals, viz., lead, mercury, and cadmium, on growth, chlorophyll a, b, c, carotenoids, and PUFA content of marine microalgae Chlorella sp. and Cylindrotheca fusiformis. At 96-h exposure, the IC50 values for Hg2+, Pb2+, and Cd2+ were 0.85 mg/L, 2.4 mg/L, and 5.3 mg/L respectively, in Chlorella sp. In C. fusiformis, IC50 values for Hg2+, Pb2+, and Cd2+ were 0.5 mg/L, 1.2 mg/L, and 3 mg/L respectively. The pigment contents of both microalgae were significantly affected upon heavy metal exposure. In Chlorella sp. and C. fusiformis, the exposed concentrations of Hg2+ averagely decreased the PUFA content by 76.34% and 78.68%, respectively. Similarly, Pb2+-exposed concentrations resulted in 54.50% and 82.64% average reductions in PUFA content of Chlorella sp. and C. fusiformis, respectively. Cd2+-exposed concentrations showed 32.58% and 40.54% average reduction in PUFA content of Chlorella sp. and C. fusiformis, respectively. Among the environmental stress conditions, the dark treatment has increased total PUFA content by 6.63% in Chlorella sp. and 3.92% in C. fusiformis. It was observed that the 50% nitrogen starvation (two-stage) significantly improved the PUFA production from 26.47 ± 6.55% to 40.92 ± 10.74% in Chlorella sp. and from 11.23 ± 5.01 to 32.8 ± 14.17% in C. fusiformis. The toxicity for both microalgae was followed in the order Hg2+ > Pb2+ > Cd2+. Among the two species, Chlorella sp. has shown a high tolerance to heavy metals and can be effectively utilized in PUFA production.

De-novo exposure assessment of heavy metals in commercially important fresh and dried seafood: Safe for human consumption

The heavy metals (HMs) in seafood are alarming due to their biomagnification in the food chain. The concentrations of As, Cd, Hg, Pb, Cr, and Ni in both fresh and dried fish were quantified, and the potential exposure and safe intake levels for human consumption were assessed by the European Commission (EC) and the Food Safety Standard Authority of India (FSSAI). HMs concentrations ranged from 0.003 mg/kg (Cr) to 2.08 mg/kg for (As) and 0.007 mg/kg (Hg) to 2.76 mg/kg (As). Cd, Hg, and Pb levels in fresh and dried fish were below the maximum residue limits (MRLs) set by the EC and FSSAI, which were 0.1 mg/kg, 0.5 mg/kg, and 0.3 mg/kg, respectively. Cr and As concentrations were also below the MRLs of 12 mg/kg and 76 mg/kg for aquatic products specified by FSSAI. The concentration of HMs in fresh and dried fish was found in the order of As > Cr > Ni > Pb > Cd > Hg and As > Cd > Cr > Ni > Pb > Hg, while the fresh and dried fishes contained HMs in the following order: E. areolatus > S. longiceps > L.lentjen > S. barracuda > E. affinis > S. javus and DA > DS > DR > DB > DSF. The metal pollution index (MPI) validates seafood is HMs free, while the single (Pi) and Nemerow integrated pollution index (Pnw) indicate that concentrations of Cd and As in fresh and dried fish have exceeded the threshold value. The target hazard quotient (THQ<1), hazard index (HI < 1), and target cancer risk (TCR<10-4) indicate that there are no non-carcinogenic and carcinogenic risks through the consumption of seafood and seafood products collected from the Tuticorin coast and marketed at the domestic and international levels. The preliminary findings emphasize the importance of formulating domestic legislation/government initiatives to promote seafood and its consumption. The attainment of this objective shall be facilitated by examining the levels of persistent organic pollutants (POPs) in seafood and evaluating its potential risk to consumers.

Stable Isotopes (δ13C and δ15N) and Trace Elements of Invertebrates and Fish from the Coastal Waters of Ha Tinh Province, Central Vietnam

Stable isotope signatures (δ13C, δ15N) and trace elements (TEs) were analyzed from invertebrates and fish to assess food web structure and the biomagnification or biodilution of Cu, Pb, Cd, Zn, Mn, Cr, Hg and As in coastal waters of Ha Tinh Province, Central Vietnam. δ13C and δ15N values of purported food sources (sediments, phytoplankton, macroalgae, and zooplankton) ranged from -21.24 ± 0.39‰ to -16.72 ± 1.02‰ and from 3.02 ± 0.70‰ to 7.30 ± 0.42‰, respectively. The δ13C and δ15N values in invertebrates and fish ranged from -19.75 ± 0.10‰ to -18.68 ± 0.40‰, and from 7.02 ± 1.21‰ to 9.10 ± 0.29‰. The δ15N values showed that the food web structure could be divided into four trophic levels. The benthic invertebrates had significantly higher concentrations of Cu, Pb, Zn, Cd and As. Hg concentrations tended to accumulate higher in the crabs and fish. The biodilution of Pb, Cd, Zn, Cr was observed throughout the food web, whereas biomagnification was observed for Cr, Mn, and As in bivalves; Cd and Zn in gastropods; Pb, Cd, Zn, and As in crabs; Cd in prawns and Hg in fish.

Toxicological effect of endocrine disrupting heavy metal (Pb) on Mekong silurid Pangasius catfish, Pangasius hypophthalmus

The current study aimed to investigate the effects of lead nitrate exposure on the enzymatical, haematological, and histological changes in the gill, liver, and kidney of Pangasius hypophthalmus. The fish were divided into six groups and treated with different Pb concentrations. The LC₅₀ value of Pb was 55.57 mg/L at 96 h for P. hypophthalmus, and sublethal toxicity was assessed for 45 days at 1/5th (11.47 mg/L) and 1/10th (5.57 mg/L) of LC₅₀ concentration. Enzymes such as aspartate aminotransferase (AST), alanine aminotransferase (ALT) levels, alkaline phosphate (ALP), and lactate dehydrogenase (LDH) content increased significantly during sublethal toxicity of Pb. The reduction of HCT and PCV indicates an anemic condition due to the toxicity of Pb. Differential leucocytes, lymphocytes, and monocytes and their % values significantly decreased, indicating Pb exposure. The main histological changes observed in the gills were the destruction of secondary lamellae, the fusion of adjacent gill lamellae, primary lamellae hypertrophy, and severe hyperplasia, while in kidney exposed to Pb showed melanomacrophages, increased periglomerular, peritubular space, vacuolation, shrunken glomerulus, destruction of tubular epithelium, and hypertrophy of distal convoluted segment. The liver showed severe necrosis and rupture of hepatic cells, hyper trepheoid bile duct, shifting of nuclei, and vascular hemorrhage, while in the brain, binucleus, mesoglea cells, vacuole, and ruptured nucleus were observed. In conclusion, P. hypophthalmus, which has been exposed to Pb has developed a number of toxicity markers. Consequently, prolonged exposure to higher Pb concentrations may be harmful to fish health. The findings strongly suggest that the lead had a detrimental impact on the P. hypophthalmus population, as well as on the water quality and non-target aquatic organisms.

Heavy metals content in fresh tuna and swordfish caught from Hindian and Pacific Oceans: Health risk assessment of dietary exposure

Background and Aim

Yellowfin tuna and swordfish are seafood commodities commonly caught from deep oceans worldwide. Therefore, this study aimed to assess the levels of three heavy metals, namely, cadmium (Cd), lead (Pb), and mercury (Hg) in yellowfin tuna and swordfish. The results are expected to provide consumers with information on the safety of consuming or exporting these fishes caught in the Hindian and Pacific Oceans.

Materials and Methods

Fresh yellowfin and swordfish were obtained from fishermen's catches in FAO Fishing Zone 57 (Indian Ocean) and 71 (Pacific Ocean) and then collected at Benoa Harbor, Bali Province. The comparative method was to evaluate the levels of heavy metals in each fish. Furthermore, heavy metal concentrations, including Pb, Cd, and Hg, were determined using atomic absorption spectroscopy analysis. These results were then used to assess the safety of these fishes by calculating the estimated daily intake (EDI) and target hazard quotients-total target hazard quotients (THQs-TTHQs).

Results

The analysis showed that none of the samples exceeded the threshold levels for the three heavy metals, which was specified by the Indonesian National Standard (SNI) and European Commission Regulation (CR) No. 1881/2006. The EDI and provisional tolerable weekly index (PTWI) obtained in this study were still in the safe range. However, the PTWI values for Pb in yellowfin tuna product from the Indian Ocean were higher (0.0038 mg/kg) compared to the recommended standard for the adult population. The THQ-TTHQ values of fish caught from these oceans were also within the acceptable range specified by the two agencies, indicating that they are safe for consumption by people with various age groups and for export purposes.

Conclusion

The average levels of three heavy metals (Cd, Pb, and Hg) in muscle samples of yellowfin tuna and swordfish caught from the Pacific and Hindian Oceans were within the acceptable range as specified by the SNI and CR No. 1881/2006. Furthermore, the EDI and THQs values indicated that fishes caught from the Pacific and Hindian Oceans were safe for consumption. This research is still limited to assessing two capture fisheries commodities. Further research is needed on the assessment of heavy metal levels in other capture fisheries commodities in this capture zone.

Assessment of elemental composition in commercial fish of the Bay of Cádiz, Southern Iberian Peninsula

The assessment of trace metal content in our fish diet is important due to the adverse effect on human health. Despite the increasing interest about the fish quality, little information is available for Southern Spain, a region characterized by high seafood intake. Nine species from the Bay of Cádiz with high commercial value were selected. Similar values were measured in the nine studied species for most of the elements, except for the macroelements Ca and S, and the microelements Fe, Mn and As, which showed significant differences among species. Metal Pollution Index (MPI) did not differ among species, and it was similar to those obtained for other Atlantic and Mediterranean locations. The values measured for the nine species were below the health limits provided by World, European and Spanish legislations, indicating that, in general terms, consumption of these species is safe in the study area.

Mercury Contamination in Fish and Its Effects on the Health of Pregnant Women and Their Fetuses, and Guidance for Fish Consumption-A Narrative Review

As a principal source of long-chain omega-3 fatty acids (3FAs), which provide vital health benefits, fish consumption also comes with the additional benefit of being rich in diverse nutrients (e.g., vitamins and selenium, high in proteins and low in saturated fats, etc.). The consumption of fish and other seafood products has been significantly promoted universally, given that fish is an important part of a healthy diet. However, many documents indicate that fish may also be a potential source of exposure to chemical pollutants, especially mercury (Hg) (one of the top ten chemicals or groups of chemicals of concern worldwide), and this is a grave concern for many consumers, especially pregnant women, as this could affect their fetuses. In this review, the definition of Hg and its forms and mode of entrance into fish are introduced in detail and, moreover, the bio-accumulation of Hg in fish and its toxicity and action mechanisms on fish and humans, especially considering the health of pregnant women and their fetuses after the daily intake of fish, are also reviewed. Finally, some feasible and constructive suggestions and guidelines are recommended for the specific group of pregnant women for the consumption of balanced and appropriate fish diets in a rational manner.

Effect of household culinary processes on organochlorine pesticide residues (OCPs) in the seafood (Penaeus vannamei) and its associated human health risk assessment: Our vision and future scope

Food safety is crucial in today's competitive trading market, as it directly affects human health and promotes seafood exports. The effects of thermal processing (boiling, frying, grilling, and microwave cooking) on pesticide residues (PR) in P. vannamei were assessed. The PR in raw and processed shrimp ranged from 0.007 to 0.703 μg/kg for uncooked/raw, not detected (ND) to 0.917 μg/kg for boiled, ND to 0.506 μg/kg for fried, ND to 0.573 μg/kg for grilled and ND to 0.514 μg/kg for microwave cooked shrimps. The Endrin, endosulfan sulfate, and heptachlor were predominant PR found in the raw and processed shrimp. The PR content in raw and cooked shrimps were below the maximum residue limits (MRL) set by the Codex Alimentarius Commission (2021) and the European Commission (86/363/1986 and 57/2007). The estimated daily intake (EDI) of PR from raw and processed shrimps were below the ADI prescribed by CAC. The hazard quotient (HQ) and hazard ratio (HR) values were <1, indicating no non-carcinogenic or carcinogenic health implications through shrimp consumption. The estimated maximum allowable shrimp consumption rate (CRlim) suggests an adult can eat >100 shrimp meals/month, which is over the USEPA's (2000)recommendation of >16 meals/month without health issues. The Effect of thermal processing was detected in the following order: boiling < grilling < frying < microwave cooking. The processing factor (PF < 0.7), paired t-test (t < 0.05), Tukey post hoc (p < 0.05) test, Bray-Curtis similarity index, and matrix plot exhibited that all the four thermal processing methods have a considerable impact on pesticides in the processed shrimps. But frying (59.4%) and microwave cooking (60.3%) reduced PR far beyond boiling (48.8%) and grilling (51.3%). Hence, we recommend frying and microwave processing are better methods for minimizing PR in seafood than boiling or grilling.

Distribution and ecological risk assessment of heavy metals using geochemical normalization factors in the aquatic sediments

Thamirabharani river acquires a noticeable quantity of sewage and agriculture waste from local inhabitants. The distribution of heavy metals in the surface sediments of the Thamirabharani river was analyzed using Inductively Coupled Plasma- Mass Spectrometry (ICP-MS) to study the ecological risks. The heavy metal concentrations in the sediments ranged from 0.098 ± 0.03(Cd) to 159.181 ± 13.36 mg kg^-1 (Fe). The Cd, Zn, Ni, Fe, and Mn concentrations in the sediments were above the US Environmental Protection Agency-Sediment Quality Guidelines. The fact that Cd, Co, and Cu concentrations at sites 4 and 5 exceeded the background values (BGVs) of 0.2, 13, and 32 mg kg^-1 suggests anthropogenic activity, notably in the downstream of the river. The sediment contaminated with Cd is more evident, particularly in the estuarine region. The potential ecological risk index (150<PERI≤300) and ecological risk co-efficient (40 < Er < 80) revealed moderate ecological risk at the estuarine region (S5). There was a moderate level of pollution in the downstream region (S4 and S5) based on a geo-accumulation index (Igeo), contamination factor (CF), pollution load index (PLI), and the moderate degree of contamination (mCd) values. According to the geochemical normalization factors, the downstream region (sites 4 and 5) was moderately polluted than the upstream region (S1 and S2), which may affect the estuarine/marine ecosystem. This information may facilitate the relevant regulatory authorities to implement the requisite stringent monitoring program in the aquatic ecosystem.

Potentially toxic elements contamination and its removal by aquatic weeds in the riverine system: A comparative approach

Thamirabarani river acquires large untreated sewage effluents from the Tirunelveli and Thoothukudi districts of South Tamil Nadu. This study examined the concentration of trace elements in water, sediment, and phytoaccumulation potential of aquatic weeds viz., A. cristata, E. crassipes, S. natans, and P. stratiotes, growing along Srivaikundam dam of Thamirabarani river. The Pb, As, Hg, Cd, and Ni concentrations in water were slightly higher than the US Food and Drug Administration (USFDA) drinking water guidelines; however, their accumulation in sediment was below WHO's sediment quality guideline. This study concludes that the phytoaccumulation factor (PAF) and translocation factor (TF) was >1 in E. crassipes and A. cristata, representing them as hyperaccumulators, suitable for phytoremediation in polluted localities. E. crassipes, A. cristata, and S. natans accumulated (100-500 fold) higher trace elements concentrations than that present in the water. Also, the concentrations of trace elements found in the aquatic weeds were below the recommended levels for the critical plant range (CRP). These selected aquatic weeds are more suitable for plant hybridization to be modified as superbug plants.