Environmental health risk assessment of Zn, Cd, Pb, Fe, and Co in coastal sediments of the southeastern Gulf of Aqaba

Abdelbaset El-Sorogy; Hamdy E. Nour; Khaled Al-Kahtany; Mohamed Youssef; Talal Alharbi; Salvatore Giacobbe

doi:10.1515/geo-2025-0807

Article Open Access

Environmental health risk assessment of Zn, Cd, Pb, Fe, and Co in coastal sediments of the southeastern Gulf of Aqaba

Abdelbaset El-Sorogy , Hamdy E. Nour , Khaled Al-Kahtany , Mohamed Youssef , Talal Alharbi and Salvatore Giacobbe

Published/Copyright: May 15, 2025

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From the journal Open Geosciences Volume 17 Issue 1

Abstract

This study provides a comprehensive assessment of environmental and human health risks associated with potentially toxic elements in the coastal sediments of the Gulf of Aqaba. A total of 33 sediment samples were analyzed using inductively coupled plasma mass spectrometry, revealing Fe (1,526–5,123 mg/kg), Zn (16.8–32.0 mg/kg), Pb (3.5–9.1 mg/kg), Co (2.2–6.4 mg/kg), and Cd (0.05–0.18 mg/kg). The concentrations detected were within acceptable limits and below the Interim Sediment Quality Guidelines, indicating minimal environmental risk. Environmental indices, including the pollution index, modified contamination degree, pollution load index, hazard index, and lifetime cancer risk indicate no contamination or health risks for adults or children through ingestion and dermal contact pathways. Principal component and correlation analysis suggest that Fe, Zn, and Co primarily originate from natural geological processes due to their strong association with elements typically derived from bedrock weathering, while minor anthropogenic contributions may arise from tourism and coastal activities. The findings confirm that the sediments pose no environmental or health risks, providing a baseline for future monitoring and pollution management in the Gulf of Aqaba.

Keywords: Gulf of Aqaba; Arabian Peninsula; heavy metal contamination

1 Introduction

The Gulf of Aqaba is located east of the Sinai Peninsula and west of the Arabian Peninsula, between latitudes 28–30°N and longitudes 34–36°E (Figure 1). It spans approximately 160 km in length and up to 24 km in width, resulting in the convergence of the Arabian and African tectonic plates. The Gulf is connected to the Red Sea via the Strait of Tiran, with its deepest point reaching 1,850 m below sea level [1,2]. The Gulf of Aqaba is a semi-enclosed water basin linked to the Red Sea through a relatively narrow and shallow strait. It plays a vital role in shaping its hydrodynamics through tidal and current activity. The Gulf is rich in marine biodiversity, hosting hundreds of coral species, over 100 types of coral reefs, more than 800 varieties of colorful fish, and numerous crustaceans and mollusks species, many of which are endemic to this region [2,3]. Industrial activities, such as oil transportation and desalination, and tourism-related construction projects may contribute to elevated levels of Zn and Pb in the coastal sediments through runoff and direct discharge [4,5]. In recent years, Saudi Arabia has undertaken extensive tourism development projects along its southern Gulf of Aqaba coastline. Simultaneously, the Kingdom is heavily investing in environmental monitoring initiatives to safeguard the ecological integrity of its coastal areas. The potential contamination of marine environments with potentially toxic elements (PTEs) remains a major challenge for environmental scientists, necessitating proactive strategies to mitigate both health and ecological consequences. Coastal sediments are derived from Precambrian basement rocks, including granites and metamorphic formations, contributing to the trace element composition. In addition, marine sediments contain silicate minerals, carbonates, and biogenic components from coral reefs and marine organisms. PTEs, such as Cu, Pb, Zn, and Cd, may originate from both the natural weathering of rocks and human activities, including maritime traffic and coastal development.

Figure 1

Location map and sampling sites modified after [4] (source: Esri, Maxar, Earthstar Geographics).

Excessive environmental PTEs act as persistent pollutants, accumulating in marine sediments or entering the water column, where marine organisms absorb them. This bioaccumulation facilitates the transfer of PTEs through the food chain, ultimately reaching humans via inhalation, ingesting contaminated silt or dust, and dermal contact, posing significant health risks [6,7,8]. Several studies have investigated PTE distribution in sediments and seawater along the Red Sea coast [9,10,11,12]. However, most of these studies have primarily focused on environmental risk assessments while neglecting health risk evaluations. Although sediment contamination assessments have been conducted in various regions worldwide, research specific to the study area remains limited. Health risk assessments of PTEs in coastal sediments are particularly scarce, highlighting the need for further investigation.

This study aims to:

Quantify the concentrations of Zn, Cd, Pb, Fe, and Co in the coastal sediments of the southeastern Gulf of Aqaba.
Compare these concentrations with international sediment quality guidelines.
Evaluate the potential environmental and human health risks of metal contamination. By addressing these objectives, this research is a foundational reference for future studies and contributes to a better understanding of PTE contamination and its implications in the Gulf of Aqaba.

2 Materials and methods

Thirty-three surface sediment samples were collected manually using a stainless-steel box from beaches along the Saudi coast of the southern Gulf of Aqaba at depths ranging from 1 to 15 cm and mapped in Figure 1. Sampling sites were selected to represent diverse locations across the southern Gulf, including areas influenced by tourism activities in the south (samples 15–27), as well as relatively naturally untapped regions in the north (samples 5–14). However, access to certain restricted areas was not permitted, preventing sample collection from those sites [4]. Samples were collected during a single season. The potential effects of seasonal and tidal variability on metal concentrations were not evaluated in this study. To minimize contamination, all samples were collected using acid-washed tools, stored in sealed polyethylene bags, and transported under controlled conditions.

To assess environmental contamination in the study area, the concentrations of Zn, Cd, Pb, Fe, and Co were measured using inductively coupled plasma mass spectrometry (ICP-MS, NexION 300D, PerkinElmer, USA) at the King Saud University laboratory [4]. ICP-MS calibration was performed using certified reference materials (NIST 1646a) to ensure analytical accuracy and precision. These metals were selected based on their environmental relevance, toxicity, and potential for accumulation. While Zn, Fe, and Co are essential trace elements for marine life, they can become toxic at elevated concentrations. In contrast, Cd and Pb are highly toxic even at low levels and pose significant risks to aquatic ecosystems and human health. These metals are commonly present in environmental samples due to their association with industrial activities, agricultural runoff, and natural geological sources.

Sample preparation and analysis followed internationally recognized standards to ensure data accuracy and reliability. Quality assurance and quality control (QA/QC) measures included the use of blanks, replicates, and determination of detection (LOD) and quantitation limits (LOQ). The LOD values ranged from 0.1 to 0.5 µg/L for Fe, 0.01 to 0.1 µg/L for Zn, 0.01 to 0.1 µg/L for Pb, 0.001 to 0.01 µg/L for Cd, and 0.01 to 0.1 µg/L for Co. The LOQ values were typically 0.5 to 1.0 µg/L for Fe, 0.1 to 0.5 µg/L for Zn and Pb, 0.01 to 0.05 µg/L for Cd, and 0.1 to 0.5 µg/L for Co. The resulting dataset, supported by rigorous statistical analysis of censored observations, provides a reliable foundation for evaluating PTE distribution in the Gulf of Aqaba. The analysis relied on analysis of variance and principal component analysis (PCA), data quality control, reproducibility and transparency, and robustness testing.

To evaluate contamination levels and the ecological risks associated with PTEs, several single and integrated contamination indices were employed. These included the single pollution index (PI), modified contamination degree (mC_deg), and pollution load index (PLI). The calculation procedures, classification of these indices, and the parameters used are detailed in equations (1)–(3) and Table S1, following the most up-to-date and consolidated literature [13,14,15,16,17,18].

(1) PI = C n / B n .

In sediment studies, PI is a key metric used to assess the degree of contamination by comparing the concentration of a specific PTE to its background or permissible limit. A PI value greater than 1 indicates contamination, while values below 1 suggest minimal or no pollution. This index helps evaluate soil quality and potential ecological risks.

(2) m C deg = ΣCF i .

It is an index used to evaluate the overall level of PTE contamination by summing the contamination factors of multiple elements. It provides a comprehensive assessment of soil pollution severity, with higher values indicating greater contamination. This index is useful for identifying areas at risk and guiding environmental management strategies. Where C _n is the PTE content in the soil, B _n is the concentration of elements in the Earth’s crust, and CF_i is the contamination factor for each element.

(3) PLI = ( CF 1 × CF 2 × CF 3 × CF 4 × … CF n ) 1 / n .

It is a comprehensive tool used to assess the overall level of PTE contamination by integrating multiple element concentrations. PLI value >1 indicates pollution, while PLI <1 suggests no significant contamination. This index helps evaluate soil quality, monitor pollution trends, and support environmental management decisions.

To assess health risks for both adults and children through ingestion and dermal contact, various indices were applied, including chronic daily intake (CDI), hazard quotients (HQ), hazard index (HI), cancer risk (CR), and total lifetime cancer risk (LCR). Given the area’s significance as a tourist destination, with activities such as swimming, diving, and beach recreation being common, attention was given to evaluating the health risks associated with dermal contact or ingestion. The calculation methods for these indices are detailed in formulas (4)–(9), while Table S2 outlines the exposure factors used to estimate CDI for non-carcinogenic risks (CRs) [19,20,21]. The reference dose is an estimate of the daily exposure level to PTEs that is unlikely to cause harmful effects on human health over a lifetime [22,23,24,25].

(4) CDI ing = ( Cs × R ing × EF × ED ) / ( BW × AT ) × CF,

(5) CDI derm = ( Cs × SA × AFs × ABS × EF × ED ) / ( BW × AT ) × CF,

(6) HQ = CDI / RfD,

(7) HI = ΣHQ = HQ ing + HQ derm ,

(8) CR = CDI × CSF,

(9) LCR = ΣCR = CR ing + CR derm .

3 Results and discussion

3.1 PTEs concentration and environmental assessment

The coastal sediments in the study area range from fine sand to gravels belonging to different fragments of marine shells. Rock and coral fragments, which result from weathering, are commonly found at the entrances of valleys. Figure 2 illustrates the distribution of PTE concentrations in coastal sediments. The PTE levels varied as follows: Fe ranged from 1,526 to 5,123 µg/g, with an average of 3,376.5 ± 831 µg/g; Zn ranged from 16.8 to 32 µg/g, averaging 24.31 ± 3.7 µg/g; Pb ranged from 3.5 to 9.1 µg/g, with an average of 6.66 ± 1.3 µg/g; Co ranged from 2.2 to 6.4 µg/g, averaging 4.55 ± 1.2 µg/g; and Cd ranged from 0.05 to 0.18 µg/g, with an average of 0.089 ± 0.02 µg/g. Spatial distribution patterns revealed that the highest concentrations were predominantly observed in the southern part of the study area: Fe in sample 14, Pb in sample 15, Zn in sample 29, and Cd in sample 32. Co was an exception, as its highest concentration was recorded in sample 1 in the northern part of the area. This increase may be due to the weathering of basement rocks near the northern coast, particularly granite and alkaline granite formations. In contrast, the lowest concentrations for all PTEs were detected in samples 13, 15, 16, 21, and 26 are mainly located in the southern region.

Figure 2

Spatial distribution of PTE concentration per sample location in the study area.

To determine whether the southern coast of the Gulf of Aqaba experiences pollution levels comparable to other regions worldwide, and with reference values for marine sediment quality, it is crucial to assess whether PTE concentrations exceed safe limits, identify pollution sources, and evaluate the effectiveness of local environmental management practices. This comparison is important for guiding environmental defense and conservation efforts. When comparing the present PTE concentrations with the reference values of the interim marine quality guidelines (ISQGs) and the probable effects level (PEL) [26], all study elements fall within safe ranges, as their concentrations are significantly lower than the reference values. This indicates no potential risk of biological effects associated with the metal levels in the sediments. Additionally, the average concentrations of Pb and Zn were lower than those reported for northern China [16], Bohai Bay, China [27], and Earth’s crustal background levels [28,29]. Similarly, the average Co concentration was below the levels documented for Gialova Lagoon, Greece [30], the Al-Khobar region of the Arabian Gulf [31], and Earth’s crustal background. The average Cd concentration was also below the values recorded along the Yemeni coast [32], northern China, Gialova Lagoon, Greece, and Bohai Bay, China. In conclusion, the average Fe concentration was lower than all comparison values listed in Table 1.

Table 1

Comparison between PTE concentration in the study area (µg/g) and other coastal sediments, background references, and sediment quality guidelines

Site	Fe	Cd	Zn	Pb	Co	Reference
Present study	3,377	0.09	24.31	6.66	4.55
Yemen coast, Red Sea	—	1.10	33.10	3.60	—	[33]
Al-Khobar area, Arabian Gulf	7,552	0.23	52.70	5.36	4.75	[32]
North Coast, China	—	0.77	60.92	21.45	—	[16]
Bohai Bay, China	46,000	0.19	112.3	32.00	—	[27]
Gialova Lagoon, Greece	32,000	0.13	—	35.46	14.81	[31]
Earth’s crust shall background	47,200	0.30	95.00	20.00	19.00	[28]
Continental crust background	56,300	0.20	70.00	12.50	25.00	[29]
ISQGs	—	0.70	124.0	30.20	—	[26]
PEL	—	4.21	271.0	112.0	—	[26]

The PI is calculated using the concentrations of individual metals in sediments and various reference values, such as preindustrial levels, average crustal levels, background values, baseline concentrations, national criteria, or threshold pollution values. PI is widely applied to classify sediments into three pollution categories (Table S1). In the studied sediments, PI values ranged as follows: Fe (0.032–0.109, average 0.071), Co (0.116–0.337, average 0.239), Zn (0.177–0.337, average 0.256), Cd (0.167–0.6, average 0.303), and Pb (0.175–0.455, average 0.332). These results indicate that the concentrations of the PTEs studied are below threshold pollution levels (Table 2). However, it is important to note that a PI value of below 1 does not necessarily confirm the absence of pollution, as anthropogenic influences or natural background enrichments may still be present [33,34,35].

Table 2

The distribution values of the PI, mC_deg, and PLI data in coastal sediments

SN	PI					mC_deg	PLI
SN	Fe	Zn	Pb	Co	Cd	mC_deg	PLI
1	0.060	0.259	0.195	0.337	0.267	0.624	0.291
2	0.087	0.237	0.235	0.274	0.333	0.737	0.322
3	0.078	0.197	0.290	0.289	0.400	0.854	0.334
4	0.077	0.274	0.300	0.242	0.300	0.690	0.323
5	0.046	0.196	0.390	0.126	0.200	0.494	0.239
6	0.084	0.261	0.330	0.258	0.433	0.913	0.347
7	0.086	0.259	0.400	0.232	0.267	0.640	0.320
8	0.075	0.283	0.360	0.200	0.300	0.691	0.318
9	0.078	0.265	0.385	0.232	0.333	0.754	0.335
10	0.087	0.289	0.340	0.274	0.267	0.645	0.331
11	0.086	0.295	0.400	0.321	0.300	0.713	0.346
12	0.052	0.228	0.280	0.211	0.200	0.749	0.366
13	0.049	0.246	0.290	0.221	0.167	0.683	0.358
14	0.109	0.240	0.320	0.205	0.267	0.869	0.444
15	0.048	0.177	0.455	0.147	0.233	0.564	0.258
16	0.032	0.215	0.310	0.226	0.167	0.684	0.332
17	0.099	0.295	0.380	0.332	0.300	0.724	0.371
18	0.077	0.284	0.410	0.279	0.300	0.712	0.344
19	0.064	0.282	0.340	0.326	0.267	0.644	0.316
20	0.099	0.294	0.395	0.221	0.400	0.872	0.363
21	0.087	0.196	0.400	0.116	0.233	0.557	0.270
22	0.063	0.261	0.360	0.200	0.267	0.621	0.287
23	0.074	0.265	0.385	0.258	0.300	0.696	0.323
24	0.043	0.196	0.410	0.121	0.233	0.556	0.247
25	0.073	0.257	0.210	0.200	0.300	0.658	0.281
26	0.046	0.184	0.175	0.132	0.233	0.515	0.215
27	0.070	0.259	0.340	0.200	0.300	0.682	0.306
28	0.073	0.274	0.375	0.274	0.300	0.703	0.333
29	0.081	0.337	0.235	0.326	0.333	0.779	0.369
30	0.063	0.282	0.345	0.326	0.267	0.655	0.331
31	0.079	0.320	0.275	0.289	0.367	0.828	0.368
32	0.068	0.261	0.315	0.274	0.600	1.187	0.351
33	0.068	0.277	0.360	0.237	0.400	0.855	0.326

The mC_deg, which assesses overall PTE contamination in sediments and is categorized into seven classes [36], ranged from 0.494 to 1.187, with an average of 0.721. This indicates that the coastal sediments exhibit very low contamination from the studied PTEs (Table 2). Similarly, the PLI, introduced by [37,38], evaluates the overall pollution level of each sample and the severity of contamination at each sampling site [19,39]. The PLI values ranged from 0.2148 to 0.4438 with an average of 0.3236. These results suggest that the coastal sediments studied are not contaminated by the PTEs investigated. These results are entirely consistent with field observations, as the study area remained untouched by human intervention for long periods. However, in the last few years, developmental efforts have been directed toward it, transforming it into a global tourist resort. Therefore, continuous monitoring of PTE levels and identifying their sources are extremely important.

The correlation matrix (Figure 3) revealed a strong positive correlation between Co and Zn (r = 0.719) and a moderate correlation between Fe and Zn (r = 0.517), suggesting that these metals may share common sources, such as industrial activities, natural mineral deposits, or similar geochemical processes [40,41]. In contrast, weak correlations were observed among metal pairs such as Fe–Cd, Zn–Cd, Co–Cd, and Fe–Co. Additionally, negative correlations were identified between Pb–Zn, Co–Pb, and Cd–Pb, indicating independent sources and distinct geochemical behaviors [42,43].

Figure 3

The correlation matrix of the analyzed PTEs.

PCA identified two significant components (PC1 and PC2), explaining a substantial portion of the data variance. PC1 (42.5% variance) represents geogenic contributions (Fe, Zn, Co) linked to bedrock weathering, while PC2 (21.6% variance) reflects minor anthropogenic inputs, likely from tourism and industrial activities (Table 3). PC1 showed high positive loadings for Fe (0.728), Zn (0.834), Co (0.766), and Cd (0.719), indicating a strong positive correlation among these metals, likely reflecting a shared origin such as mineral deposits [44,45,46]. The coastal sediments of northwest Saudi Arabia derive their metal content primarily from the weathering and erosion of Tertiary sedimentary rocks and older Precambrian basement rocks. Minerals like magnetite, hematite, sphalerite, and sulfides are significant sources of Fe, Zn, Co, and Cd. These metals were deposited in coastal sediments through fluvial transport and erosion processes during the Tertiary period. Additionally, hydrothermal activities related to Red Sea rift tectonics have further enriched localized zones with these metals [2,4,11]. Conversely, PC2 revealed inverse relationships between Fe, Pb, and Cd with Co and, to a lesser extent, Zn, suggesting differing environmental behaviors or anthropogenic sources [47]. The weaker positive loadings of Zn and Co on PC2 may indicate distinct geochemical processes or secondary sources contributing to their presence. This differentiation highlights the complex interplay of natural and anthropogenic factors shaping PTE distribution in the study area. Although the primary source of PTEs in the study area can be attributed to the natural weathering of rocks, consistent with the fact that the area remained untouched for many years, anthropogenic sources cannot be ignored, particularly due to urban expansion and coastal development projects in recent years.

Table 3

Principal components for the investigated PTEs

HMS	Component
HMS	1	2
Fe	0.728	−0.150
Zn	0.834	0.221
Pb	−0.014	−0.796
Co	0.766	0.430
Cd	0.719	−0.179
% of variance	42.51	21.64
Cumulative %	42.51	64.15

3.2 Health risk assessment

Zn, Cd, Pb, Fe, and Co accumulate in marine sediments, posing significant risks to both aquatic ecosystems and human health. Elevated concentrations of these metals can disrupt marine life through bioaccumulation and biomagnification within the food chain, ultimately affecting human health via seafood consumption. For instance, high levels of Zn and Cd can impair the growth and reproduction of marine organisms and inhibit phytoplankton development, a crucial component of the aquatic food web [48,49].

The average CDI values for non-CRs in adults ranged from 1.22 × 10⁻⁷ (Cd) to 0.00463 (Fe) through ingestion and from 4.89 × 10⁻¹⁰ (Cd) to 1.85 × 10⁻⁵ (Fe) via dermal exposure (Table 4). In children, the CDI values ranged from 1.14 × 10⁻⁶ (Cd) to 0.0431 (Fe) through ingestion and from 2.28 × 10⁻⁹ (Cd) to 8.61 × 10⁻⁵ (Fe) via dermal exposure. The average HI values for PTEs followed a descending order of Fe, Cd, Co, Zn, and Pb for adults and children. For adults, HI values ranged from 0.00068 to 0.0025 (Cd), 0.0029 to 0.099 (Fe), 0.0001 to 0.0004 (Co), 7.7 × 10⁻⁵ to 0.0001 (Zn), and 3.4 × 10⁻⁵ to 8.9 × 10⁻⁵ (Pb). For children, HI values varied from 0.0064 to 0.023 (Cd), 0.028 to 0.093 (Fe), 0.0014 to 0.0041 (Co), 0.0007 to 0.0013 (Zn), and 0.0003 to 0.0008 (Pb).

Table 4

The average CDI, HQ, HI, CR, and LCR values of health risk assessment in adults and children

PTEs	CDI_Ing	CDI_Derm	HQ_Ing	HQ_Derm	HI	CR_Ing	CR_Derm	LCR
Adults
Co	6.23 × 10⁻⁶	2.49 × 10⁻⁸	3.12 × 10⁻⁴	1.24 × 10⁻⁶	3.13 × 10⁻⁴
Cd	1.22 × 10⁻⁷	4.89 × 10⁻¹⁰	1.22 × 10⁻³	4.89 × 10⁻⁶	1.23 × 10⁻³	7.71 × 10⁻⁷	3.08 × 10⁻⁹	7.75 × 10⁻⁷
Zn	3.33 × 10⁻⁵	1.33 × 10⁻⁷	1.11 × 10⁻⁴	4.43 × 10⁻⁷	1.11 × 10⁻⁴
Pb	9.12 × 10⁻⁶	3.64 × 10⁻⁸	6.52 × 10⁻⁵	2.60 × 10⁻⁷	6.54 × 10⁻⁵	9.12 × 10⁻⁸	3.64 × 10⁻¹⁰	9.16 × 10⁻⁸
Fe	4.63 × 10⁻⁵	1.85 × 10⁻⁵	6.61 × 10⁻⁵	2.64 × 10⁻⁵	6.63 × 10⁻³
	Children
Co	5.82 × 10⁻⁵	1.16 × 10⁻⁷	2.91 × 10⁻³	5.80 × 10⁻⁶	2.92 × 10⁻³
Cd	1.14 × 10⁻⁶	2.28 × 10⁻⁹	1.14 × 10⁻²	2.28 × 10⁻⁵	1.15 × 10⁻²	7.20 × 10⁻⁶	1.44 × 10⁻⁸	7.21 × 10⁻⁶
Zn	3.11 × 10⁻⁴	6.20 × 10⁻⁷	1.04 × 10⁻³	2.07 × 10⁻⁶	1.04 × 10⁻³
Pb	8.52 × 10⁻⁵	1.70 × 10⁻⁷	6.08 × 10⁻⁴	1.21 × 10⁻⁶	6.09 × 10⁻⁴	8.52 × 10⁻⁷	1.70 × 10⁻⁹	8.53 × 10⁻⁷
Fe	4.32 × 10⁻⁵	8.61 × 10⁻⁵	6.17 × 10⁻⁵	1.23 × 10⁻⁴	6.18 × 10⁻²

The spatial distribution of HI values (Figure 4) revealed higher non-CRs for children compared to adults, with localized peaks for Zn (samples 29 and 31), Cd (sample 32), Fe (sample 14), and Pb (samples 15, 18, and 26) in the southern region. Co exhibited elevated HI values in samples 1, 17, 19, 29, and 30. Despite these variations, all HI values remained below 1.0, indicating no significant non-CR for residents along the studied coastline [19,50].

Figure 4

Spatial distribution of Hi for Co, Fe, Cd, Zn, and Pb per sample location in the study area.

CRs associated with Pb and Cd were assessed in the sampled sediments (Table 4). For adults, the average CR values through ingestion ranged from 9.12 × 10⁻⁸ (Pb) to 7.71 × 10⁻⁷ (Cd), while for children, CRs ranged from 8.52 × 10⁻⁷ (Pb) to 7.25 × 10⁻⁶ (Cd). The average LCR values for adults varied from 9.16 × 10⁻⁸ (Pb) to 7.84 × 10⁻⁷ (Cd), and for children, the range was from 8.53 × 10⁻⁷ (Pb) to 7.21 × 10⁻⁶ (Cd). The distribution of LCR values for Pb and Cd across the study area showed that the highest LCR values for Pb were observed in samples 15 and 18 for both adults and children, while the lowest values were recorded in samples 25 and 26 (Figure 5 and Table 4). For Cd, the highest LCR values were found in samples 6 and 32, with the lowest values in samples 13 and 16.

Figure 5

Spatial distribution of LCR for Cd and Pb per sample location in the study area.

When compared to the average LCR values reported for coastal sediments from various regions including both sides of the Red Sea coast, the Gulf of Aqaba, and the Arabian Gulf [19,21,23,25,41], our average values exhibited fluctuations, either exceeding or falling below these benchmarks. Nevertheless, all LCR values for Pb and Cd in both adults and children remained within acceptable or tolerable CR levels (ranging from 1 × 10⁻⁵ to less than 1 × 10⁻⁶), indicating no significant health risks [51,52,53,54]. Although HI and LCR levels are very low and do not pose any immediate health threat, continuous monitoring of PTE levels, identifying their sources, and reducing their input into the environment are essential to maintaining long-term environmental quality.

The current methods used in this study have certain limitations that should be acknowledged. These include the inability to estimate contamination from atmospheric deposition and the interactions between PTEs and soil organic matter. Additionally, spatial and temporal variations in metal concentrations may not be fully captured due to sampling constraints. Future research should focus on enhancing analytical techniques to improve the accuracy of contamination assessments. This includes incorporating advanced geochemical modeling, isotope analysis for more precise source tracing, and remote sensing techniques for large-scale monitoring. Further studies should also investigate the bioavailability and mobility of PTEs under different environmental conditions, as well as their long-term environmental and health impacts. Expanding the study to include water and plant samples would provide a more comprehensive understanding of metal transport within the ecosystem.

4 Conclusions

The present study examines the concentrations of Zn, Cd, Pb, Fe, and Co in 33 coastal sediment samples from the southern Gulf of Aqaba, Saudi Arabia, and assesses their potential ecological and health risks. The average concentrations of PTEs were found to follow this order: Fe (3376.5 µg/g) > Zn (24.31 µg/g) > Pb (6.66 µg/g) > Co (4.55 µg/g) > Cd (0.089 µg/g). All studied PTE concentrations are within safe limits according to the ISQGs and the PEL, indicating no biological risk associated with metal levels in the sediments. The results of the PI mC_deg, and PLI suggest that the sediments are generally unpolluted to lightly polluted. Multivariate analyses revealed that the primary sources of these metals are geogenic, with some influence from anthropogenic activities, especially for Zn and Co. The HI values for the investigated metals were all below 1.0, indicating no non-CRs along the studied coastline. Additionally, the LCR values for both adults and children ranged from 1 × 10⁻⁵ to less than 1 × 10⁻⁶, indicating no carcinogenic health risks.

Environmental monitoring in the Gulf of Aqaba is crucial for sustainable management, providing insights into pollution sources and ecosystem health. It supports conservation and industrial regulation. However, limitations include restricted sampling, temporal variations, and the need for stronger causal validation. Future research should expand monitoring, use advanced geochemical techniques, and incorporate biological indicators for a more comprehensive assessment.

Acknowledgments

The authors extend their appreciation to Researchers Supporting Project number (RSP 2025R139), King Saud University, Riyadh, Saudi Arabia.

Funding information: This study was supported by the Researchers Supporting Project (number RSP2025R139) at King Saud University Riyadh, Saudi Arabia.
Author contributions: Khaled Al-Kahtany, Talal Alharbi, Abdelbaset El-Sorogy, and Mohamed Youssef: conceptualization, project administration, methodology, software, validation, formal analysis, investigation, and data curation. Hamdy Nour, Abdelbaset El-Sorogy, and Salvatore Giacobbe: writing – original draft preparation, writing – review and editing. All authors read and approved of the final manuscript.
Conflict of interest: Authors state no conflict of interest.
Ethical approval: The conducted research is not related to either human or animal use.
Data availability statement: All data generated or analyzed during this study are included in this published article.

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Received: 2025-02-13

Revised: 2025-03-24

Accepted: 2025-04-14

Published Online: 2025-05-15

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

https://doi.org/10.1515/geo-2025-0807

Keywords for this article

Gulf of Aqaba; Arabian Peninsula; heavy metal contamination

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