Contamination and ecological risk of heavy metals in Al-Uqair coastal sediments, Saudi Arabia

Investigating the bacterial community of gray mangroves (Avicennia marina) in coastal areas of Tabuk region

Mangrove vegetation, a threatened and unique inter-tidal ecosystem, harbours a complex and largely unexplored bacterial community crucial for nutrient cycling and the degradation of toxic pollutants in coastal areas. Despite its importance, the bacterial community composition of the gray mangrove (Avicennia marina) in the Red Sea coastal regions remains under-studied. This study aims to elucidate the structural and functional diversity of the microbiome in the bulk and rhizospheric soils associated with A. marina in the coastal areas of Ras Alshabaan-Umluj (Umluj) and Almunibrah-Al-Wajh (Al-Wajh) within the Tabuk region of Saudi Arabia. Amplicon sequencing targeting the 16S rRNA was performed using the metagenomic DNAs from the bulk and rhizospheric soil samples from Umluj and Al-Wajh. A total of 6,876 OTUs were recovered from all samples, of which 1,857 OTUs were common to all locations while the total number of OTUs unique to Al-wajh was higher (3,011 OTUs) than the total number of OTUs observed (1,324 OTUs) at Umluj site. Based on diversity indices, overall bacterial diversity was comparatively higher in rhizospheric soil samples of both sites. Comparing the diversity indices for the rhizosphere samples from the two sites revealed that the diversity was much higher in the rhizosphere samples from Al-Wajh as compared to those from Umluj. The most dominant genera in rhizosphere sample of Al-Wajh were Geminicoccus and Thermodesulfovibrio while the same habitat of the Umluj site was dominated by Propionibacterium, Corynebacterium and Staphylococcus. Bacterial functional potential prediction analyses showed that bacteria from two locations have almost similar patterns of functional genes including amino acids and carbohydrates metabolisms, sulfate reduction and C-1 compound metabolism and xenobiotics biodegradation. However, the rhizosphere samples of both sites harbour more genes involved in the utilization and assimilation of C-1 compounds. Our results reveal that bacterial communities inhabiting the rhizosphere of A. marina differed significantly from those in the bulk soil, suggesting a possible role of A. marina roots in shaping these bacterial communities. Additionally, not only vegetation but also geographical location appears to influence the overall bacterial composition at the two sites.

Health risk assessment and contamination of lead and cadmium levels in sediments of the northwestern Arabian Gulf coast

This environmental assessment focuses on the coastal sediments of the Al-Khafji area in the Saudi Arabian Gulf, with an analysis of the human health risks posed by lead (Pb) and cadmium (Cd) contamination. Single and integrated indices were used to detect contamination and evaluate these metals' non-carcinogenic and carcinogenic impacts on adults and children through ingestion, dermal contact, and inhalation pathways. Sediment quality guidelines and contamination indices indicated the absence of significant contamination levels. The moderate contamination observed in scattered samples did not imply adverse biological effects due to the presence of these two metals in Al-Khafji sediments. The average values of the chronic daily intake (CDI) for both Pb and Cd were higher in children than adults across all three pathways, with ratios of 9.4, 4.7, and 4.7 folds, respectively. The hazard index (HI) values for Pb and Cd were below 1, confirming that the sediments of Al-Khafji are considered acceptable and safe in terms of these potentially toxic elements (PTEs). The average lifetime cancer risk (LCR) values for Pb and Cd were higher in children compared to adults, with ratios of 9.3 and 9.4 folds, respectively. However, all detected LCR levels do not represent a potential carcinogenic health hazard. Nevertheless, a regular monitoring program aimed at detecting early signals of environmental health depletion is recommended.

Distribution, Source, and Contamination of Heavy Metals in Coastal Sediments of Jeddah, Red Sea, Saudi Arabia

The study investigates heavy metal (HM) contamination in coastal sediments of Jeddah along Red Sea coast, analyzing spatial distribution and sources. 24 samples underwent (ICP-AES) for Fe, Al, Mn, Ni, Pb, Zn, Cu, Cr, Co, Sr, V, and As. HM averages followed Fe ˃ Al ˃ Sr ˃ Mn ˃ Zn ˃ V ˃ Cu ˃ Ni ˃ Cr ˃ As ˃ Co ˃ Pb. Contamination indices revealed severe Sr enrichment, minor As and Co enrichment, and no enrichment for other HMs. Sediment quality guidelines suggest Ni, Cu, Zn, and As risks to benthic communities at some sites, while Cr and Pb pose minimal risk. Multivariate analysis indicates natural sources for Fe, Al, Mn, Ni, Zn, Cu, Cr, Co, and V, and anthropogenic sources for Sr, As, and Pb, linked to agriculture, industry, and urbanization. Increased Sr values may stem from seawater acidification impacting calcitic corals and molluscs.

Evaluation of sediment quality for heavy metal(loid)s contamination and health risk assessment in the Gulf of Suez, Egypt

The Gulf of Suez faces challenges related to contamination, primarily due to industrial, tourism, and shipping activities along its shores. This study aims to record the distribution, concentration, and potential environmental and health risk impacts of heavy metal(loid)s (HMs) in 30 surface sediment samples collected from Ras Sidr coastline, Gulf of Suez. Various contamination and health indices were employed for this study. The average concentrations of HMs (μg/g) were ranked as follows: Fe (3472), Mn (103.3), V (10.41), As (7.94), Cr (6.00), Zn (5.31), Ni (2.94). The spatial distribution of HMs indicated an increase in Mn, Zn, As, and V levels toward the southern part of the study area, potentially linked to the proximity of manganese quarries and their metal association at Abu Zenima. Contamination indices revealed moderately severe enrichment with As, minor enrichment with Mn, and no enrichment for the remaining HMs. Multivariate analysis suggested a natural origin for Cr, Fe, Mn, Ni, Zn, and V, while As were likely anthropogenic. Values of hazard index (HI) for HMs in both adults and children followed the descending order of As > Fe > Cr > V > Mn > Ni > Zn. However, all HI values were below 1.0, indicating no significant non-carcinogenic risk for individuals along the Ras Sidr coastline. 19 samples exhibited lifetime cancer risk (LCR) values exceeding 1 × 10-4 for As in children, suggesting potential carcinogenic risks. LCR values for As in adults and Cr in adults and children ranged from 1 × 10-5 to less than 1 × 10-6, indicating acceptable or tolerable levels of carcinogenic risk and no significant threats to health.

Potential contamination and health risk assessment of heavy metals in Hurghada coastal sediments, Northwestern Red Sea

Throughout the year, people flock to the Red Sea's shoreline for tourism and fishing. The current study aims to document heavy metal contamination and human health assessment in 30 surface sediment samples collected along the Hurghada shoreline in Egypt. To estimate sediment contamination, the pollution index (PI), pollution load index (PLI), degree of contamination (Cdeg), and Nemerow integrated pollution index (NIPI) were calculated, while the chronic daily intake (CDI), hazard index (HI), cancer risk (CR), and total lifetime cancer risk (LCR) were determined on both adults and children via ingestion, dermal, and inhalation pathways. The HM averages (μg/g dry weight) were in the following order: Fe (345.70) > Mn (49.36) > Pb (41.98) > Zn (7.47) > Ni (1.73) > Cu (1.23) > Co (1.09) > Cd (0.14). Pollution indices found that Hurghada coastal sediments were moderately polluted with Pb but not with the other HMs. The average CDI values were in the descending order of ingestion > dermal > inhalation pathways, and the average CDI values on children were higher than those on adults. The hazard index (HI) for adults and children was Pb > Ni > Cd > Fe > Mn > Co > Cu > Zn, and all values were <1.0, showing that these HMs had no substantial non-carcinogenic impacts on the human body. LCR results show that children have greater values than adults. LCR values in adults were lower than 1 × 10-6, indicating no substantial health concerns, while in children they ranged from 1 × 10-6 to 1 × 10-4, indicating no significant risk to human health.

Assessment of human health risks of toxic elements in coastal area between Al-Khafji and Al-Jubail, Saudi Arabia

The present work aims to document the distribution of toxic elements (TEs) and assess the human health risk posed by the TEs in the marine sediment of the Arabian Gulf, Saudi Arabia. The descending order of TE averages (μg/g) was as follows: Ni > Cr > V > Zn > Pb > Cu > As > Co. Based on the enrichment factor values, only minor enrichment for Pb, As, Cr, and Ni was noted. The hazard index (HI) values for the non-carcinogenic risk of the TEs were less than 1.0, and the lifetime cancer risk values for carcinogenic Pb, Cr, and As ranged between 2.96 × 10-8 and 5.44 × 10-5, indicating no significant health hazards for the inhabitants of the study area.

Spatial distribution and risk assessment of heavy metals in the coastal waters of the Gulf of Suez, Red Sea, Egypt

To assess ecological and health risks connected with heavy metal contamination in the Gulf of Suez, Red Sea seawater during winter 2021. The selected heavy metals were detected using the "AAS" Technique. The results presented that; the average metal concentrations ranged between (0.57, 1.47, 0.76, 5.44, 0.95, 18.79, and 1.90 μg/l) for Cd, Pb, Zn, Mn, Fe, Cu, and Ni along the investigated area. Pollution Index for overall Gulf sectors <1, indicating a slightly and moderately affected region. Metal Index for the Gulf is >1, representing the existence of heavy metal pollution, which is alarming in this area. (HPI) Heavy metal pollution index <100 indicates low contamination of heavy metal "and is apposite for consumption. The Gulf's ecological risk index (Eri) mostly fell under the low-ecological risk. The risk health estimation revealed that CDI values for carcinogenic were (10-5 to10-7), (10-6 to10-8), and (10-9 to10-11) for ingestion, dermal, and inhalation, respectively. Ingestion for children is twice as high as the proportions documented for adults. At the same time, THQ values for non-carcinogenic ingestion, dermal, and inhalation were (10-5 to 10-8), (10-4 to 10-5), and (10-10 to 10-12), respectively. Also, the total hazard quotient (THQ ing. + THQ inh.) values were <1 acceptable limit, indicating no non-carcinogenic risk to the residents through dermal adsorption and oral water intake. The ingestion pathway was the main pathway for total risk. In conclusion, the overall hazard risks are lower than the permissible limit of <1 regarding heavy metals.

Spatial geochemical structure of soft sediment on shallow littoral of the Gulf of Antalya, the eastern Mediterranean Sea

The concentrations of heavy metals in soft sediments of the Manavgat and Lara regions in Antalya, Türkiye were investigated to assess contamination levels and their potential sources, followed by multivariate statistical analysis and generation of spatial distribution maps. Results showed low contamination levels for As, Zn, and Cu, moderate contamination for Pb, Ni, and Mn, and very high accumulation for Co and Cr. Geoaccumulation index (Igeo) and contamination factor (CF) analyses revealed moderate enrichment for Mn and low enrichment for As, indicating no human-induced contamination in Cu, Pb, Zn, Mn, and As, while Ni, Co, and Cr originated mainly from agriculture. The maximum modified degree of contamination (mCd) value was at an extreme high level, with an average mCd of 4.12 indicating high contamination. Maximum pollution load index (PLI) value was 3.13, indicating high-grade pollution and an average value of 1.7 indicating moderate pollution.

Ecological and health risk assessment of heavy metals contamination in mangrove sediments, Red Sea coast

Due to the significance of mangroves for the diversity of marine and terrestrial life along the Red Sea coast, the present work aimed to evaluate the environmental and health risk of heavy metals in Wadi el-Gemal sediments. The findings of single and integrated indices demonstrated no significant pollution with Fe, Cu, Zn, Ni, Co, and Cd, while the sediments showed severe and minor enrichment with Mn and Cd, respectively, which might be attributed to the presence of some mining activities in the mountains near the study area. The possible carcinogenic and non-carcinogenic risks due to their dermal absorption from the sediments were analyzed and the findings demonstrated that the non-carcinogenic health hazards were within tolerable and safe limits. Moreover, the evaluation of chronic daily intake and the overall cancer risk (LCR) for adults and children for Pb and Cd both ruled out any current potential carcinogenic health risks.

Assessment of metal contaminants along the Bay of Bengal - Multivariate pollution indices

The spatial concentration of heavy metals (Mn, Ni, Cu, Co, Zn, Cd, and Pb) was studied in coastal areas (n = 9) including water (n = 27) and sediment (n = 27) in the Palk Bay, India to understand the metal pollution due to prevailing natural and anthropogenic activities. Pollution indices like metal index (MI), geoaccumulation index (Igeo), contamination factor (CF), pollution load index (PLI) and potential ecological risk (PER) were calculated based on the background/reference value. The values of MI index indicated that water was free of metals, whereas Igeo, CF, PLI and PER indicated moderate contamination of sediment in monsoon. Cadmium concentrations were the highest irrespective of the indices (Igeo: 0.04-1.42, Cf: 0.36-0.74, PLI: 0.36-0.74, and PER: 76.89-143.36) indicating moderate pollution. The Principal Component Analysis (PCA) affirmed that Cd was positively correlated with stations indicating anthropogenic sources of Cd contamination.

Chemical speciation and bioavailability of potentially toxic elements in surface sediment from the Huaihe River, Anhui Province, China

In order to understand the characteristics of speciation and ecological risk of potentially toxic element (PTE) pollution in the surface sediment of huaihe river (Anhui province), 23 surface sediment samples were collected. The occurrence characteristics of PTEs (As, Cr, Zn, Cu, Cd, Pb, Mn) were analyzed by modified continuous extraction method (BCR), and the pollution status and potential ecological risk of PTEs were comprehensively evaluated by Pollution Load Index (PLI), Geoaccumulation Index (Igeo), Enrichment Factor (EF) and the risk assessment code (RAC). Results showed that the total concentrations of As, Mn, Cd, Cr, Cu, Pb, and Zn in sediment were 14.98 ± 2.32, 936.02 ± 144.48, 0.32 ± 0.08, 161.73 ± 124.83, 40.44 ± 9.67, 15.46 ± 6.67, and 74.85 ± 26.43 mg/kg, respectively. The mean concentrations of PTEs with the increasing order of Zn < Mn < Cr < Pb < Cu < As < Cd. Most PTEs appeared to mainly associate with a dominant proportion of residual fraction suggesting lower mobility whereas Cd and Mn presented a relative higher exchangeable fraction indicating a great degree of bioavailability and easily ingested by aquatic organism. Results of pollution degree showed that 3 sampling sites belong to the pollution degree of strong pollution, and the other sampling sites belonged to the medium pollution level. The indexes EF revealed moderately enrichment of Cr, minor enrichment of Cd, Mn and As, no enrichment of Cu, Zn and Pb. The values of the Igeo and RAC demonstrated that Cd and Mn pose a high ecological risk, which deserves further attention.

Heavy metal pollution in surface sediments and human health assessment in southern Al-Khobar coast, Saudi Arabia

Surface sediment samples from twenty-nine stations in south Al-Khobar coastline, Arabian Gulf, have been examined to assess the heavy metal contamination and impact on human health through dermal contact. The content in Cu, Zn, Cd, Pb, Fe, Mn, Co, Hg and Ni, was evaluated. Pollution index, modified degree of contamination, and pollution load index agreed to exclude heavy metal pollution. Differently, soil pollution index and Nemerow integrated pollution index pointed out moderate and heavy pollution grade for Hg and Cu, respectively. The human health assessment, according to the low values of the hazard index ˂ 1.0 for both adults and children, excluded any significant impact on the human body. The chronic daily intake and the total lifetime cancer risk also were consistent in excluding any risk to human health. Similarly, the carcinogenic risks for Pb and Cd, and the total cancer risk ˂1 × 10^-6, did not imply significant health hazards.

Distribution and ecological risk assessment of heavy metals in sediments of Dajiuhu Lake Wetland in Shennongjia, China

The rapid development of modern society has resulted in discharge of large, heavy metal quantities into wetlands that have been continuously accumulating, causing severe pollution. Dajiuhu, located in the Shennongjia Forest District of Hubei Province in China, is a wetland of significant value internationally, serving as a model wetland ecosystem with heightened scientific research value. In this study, 27 surface sediment samples from nine sub-lakes in Dajiuhu were collected in August 2020. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the sediments were determined. The heavy metal occurrence and speciation characteristics were analyzed by an improved BCR (European Community Bureau of Reference) extraction method. Four methods were used to evaluate heavy metals' pollution degree and ecological risk. The possible source of heavy metals was inferred using correlation analysis and principal component analysis. The heavy metal content in the lake sediments of Dajiuhu wetland was from the highest to the lowest concentration as follows: Zn [Formula: see text] Cr [Formula: see text] Ni [Formula: see text] Pb [Formula: see text] Cu [Formula: see text] Cd. The average Cd content exceeded the national nature reserve threshold values, while the other heavy metals measured were below their respective threshold values. However, due to the occurrence of Pb and Cd in different forms, they still pose certain pollution and ecological risk to the lake wetlands. On the other hand, Zn, Cr, Ni, and Cu do not pose an ecological risk in the lakes of the Dajiuhu wetland. The spatial distribution of heavy metal content in the nine sub-lakes did vary significantly. Regarding the heavy metal sources in the lake sediments, Ni, Cr, and Cu originate from natural factors, and Cd and Pb have mainly anthropogenic origins. In contrast, Zn has both natural and anthropogenic origins. This study provides further insights into the study of heavy metal pollution in lake wetlands. It provides a framework and a direction for managing heavy metal pollution in the Dajiuhu wetland.

Source-specific ecological risk assessment and quantitative source apportionment of heavy metals in surface sediments of Pearl River Estuary, China

In this study, surface sediments of the Pearl River Estuary were collected from 29 stations and investigated the spatial distribution, pollution level, quantitative source apportionment, and source-specific ecological risk of 10 heavy metals. The mean concentrations followed the order of Mn > Zn > Cr > Cu > Ni > Pb > As > Co > Cd > Hg. In terms of spatial distribution, it showed that the heavy metals were enriched in the inner Pearl River Estuary with 'extremely high' level of Hg, whereas, Cd and Zn posed 'moderate to high' contamination potential. We apportioned four main sources using positive matrix factorization model, in which natural geogenic and industrial manufacturing sources accounted for 36.84% and 27.11% of the total, respectively. However, the source-specific risk assessment suggested that mixed anthropogenic sources were the main contributors, and ecological risks were strongly affected by anthropogenic imports from the surrounding cities.