Heavy Metal Pollution in Abu Dhabi Marine Sediments: A Comparative Study across Different Environmental Areas Using Various Pollution Assessment Indices

Coastal pollution in the Arabian Gulf is an emerging issue, driven by both natural processes and human activities such as atmospheric deposition, industrial effluents, discharges from desalination and sewage treatment plants, reclamation and dredging operations, island developments, and oil and gas exploration. To investigate the bottom sediments pollution characteristics and assessments, twenty-two sites were sampled monthly and quarterly in Abu Dhabi’s territorial waters across various ecological categories which includes natural habitats, confined area, nearby public beaches. The samples were analysed for dissolved trace metals, including, Cadmium, Chromium, Copper, Cobalt, Manganese, Nickel, Lead, Zinc, Mercury, and Iron. The concentrations of these metals in the sediment ranged as follows: Cd (0 mg/kg–4.68 mg/kg), Cr (0.19 mg/kg–47.05 mg/kg), Cu (0 mg/kg–71.31 mg/kg), Co (0 mg/kg–6.57 mg/kg), Fe (82.8 mg/kg–18040 mg/kg), Mn (3.06 mg/kg–282.90 mg/kg), Ni (0 mg/kg–34.63 mg/kg), Pb (0 mg/kg–24.37 mg/kg), and Zn (1.58 mg/kg–198.5 mg/kg). Further levels of heavy metal enrichment in the bottom sediments were assessed using the Contamination Factor (CF), Enrichment Factor (EF), Geo-accumulation Index (Igeo), and Pollution Load Index (PLI). The results show that confined area has severe enrichment in Cd, moderate enrichment in Zn and Cu. PLI also confirms Cd in confined areas is >1 which indicates pollution. These accumulation in confined areas, particularly those with heavy anthropogenic activity, highlights a potential environmental risk to marine biota and eventually human health.

Introduction

Heavy metals are essential for life at low concentrations [1], they are metallic elements that may be harmful to the ecosystem’s flora and fauna if present at higher concentrations [2]. Oil spills, sewage effluents, industrial discharges, auto emissions, coastline development including dredging activities and land filling are some of the major sources of metal pollution of marine ecosystem [3].

Metals, after entering the water, may precipitate or adsorb on solid surfaces, remain soluble or suspended in water or may be taken up by fauna and flora [4], [5]. These metals may accumulate in marine organisms which are consumed by other marine organisms and subsequently by humans [4], [5]. With a combined action of adsorption, hydrolysis, and co-precipitation, only a small part of free metal ions stays dissolved in water, and a large quantity of them get deposited in the sediments [6], [7]. Therefore, the contents of heavy metals in sediments are often monitored to provide basic information for environmental risk assessment.

Coastal zones, particularly those with large population densities received large inputs of pollutants from anthropogenic origin (domestic and industrial sewages), despite airborne particulates from distant industrial sources, for example, trace metals were likely transported from the industrial sites to the area of their deposition as sulphur-bearing coatings on small anthropogenic particles. After deposition, these sulphur-bearing compounds reacted with organic matter within the sediment [8]. Presence of these kinds of pollutants in the sediments pose a serious threat to the essential microorganisms that play an important role in balancing of carbon and nitrogen cycling and biotransformation of several organic pollutants [9].

Abu Dhabi seabed features a sedimentary basin with a dominant benthic substratum in the coastal regions, constituting carbonate sediment formed from fragmented skeletons of benthic organisms [10]. Abu Dhabi’s shallow subtidal environments resume to be an era of active carbonate sedimentation. The massive ongoing dredging activities has expanded the tidal flows to shallow marine surroundings: thus, enlarging its linkage to open sea environments [11]. Aeolian terrigenous sediments carried by the Shamal wind are the reason for fine sand silt and clay with high carbonate (calcite and dolomite) content [12], [10].

The spatial variability of the heavy metal concentrations in soils is basic information for identifying the possible sources of contamination and to delineate the strategies of site remediation [13]. Abu Dhabi waters have been the subject of many environmental investigations, including heavy metal distribution. However, information on heavy metal distribution in Abu Dhabi waters, particularly offshore spatial distribution, is very limited [10].

This study aims to evaluate the distribution of heavy metal pollution in the sediments of Abu Dhabi waters across various environmental zones. The gathered data on heavy metals will help inform management with pollution status as well as raise awareness among policymakers about the level of contamination in the region. In addition, the study assesses heavy metal pollution in Abu Dhabi’s marine sediments using four widely recognised pollution assessment indices after international benchmarking: the Geo accumulation Index (Igeo), Pollution Load Index (PLI), Enrichment Factor (EF) and Contamination Factor (CF), providing a comprehensive evaluation of the extent and severity of metal contamination.

Method

Study Area

The Emirate of Abu Dhabi is in the far west and southwest part of the United Arab Emirates, along the southern cost of the Arabian Gulf, between latitudes 22°40′ and around 25° N and longitudes 51° and around 56° E. The territorial waters of the Emirate embrace about 200 islands along its 700 km coastline. The region experiences very hot summer with an average annual rainfall of <82 mm [42]. In this study, 22 sites (Fig. 1) were sampled for sediment and grouped into eight categories: confined areas, natural habitats, public beaches, ports and marinas, areas near desalination plants, newly developed, areas near the nuclear power plant, and a reference area.

Fig. 1. Sampling site map.

Sample Collection

From January to December 2022, monthly sediment sampling was collected at 16 sites (Fig. 1) around Abu Dhabi, with additional quarterly sampling at 6 sites (Fig. 1) in the Al Dhafra region. These twenty two sites are classified under different categories such as confined areas (site—1, 2, 3, and 201), public beaches (site—7, 9, 107), desalination plants (site—13, 14 and 15), natural habitats (site—4, 20, 21, 22 and 123), newly developed area (site—117, 119 and 202), near nuclear power plant (site—125), ports and marinas (site—11 and 12) and reference area (site—126). Surface sediments were collected at each location using a Peterson Grab sediment sampler, and sub-samples were taken from the uppermost sediment layer to minimize contamination according to Andy Wheeler [14]—Seabed Sediment Sampling Techniques. After collection, all samples were stored in ice-packed coolers and transported to Abu Dhabi Quality and Conformity Council (AD QCC)—approved external laboratory, Arab Center for Engineering Studies (ACES). The samples were analysed for heavy metals, including Cu, Zn, Mn, Fe, Ni, Cd, Cr, Co, and Pb. The testing was conducted according to the American Public Health Association (APHA) Standard Method 3120B (23rd edition).

Data Analysis

To determine the magnitude of heavy metal contamination in the sediment, the Enrichment Factor (EF), Contamination Factor (CF) Pollution Load Index (PLI) and Geo-accumulation Index (Igeo) were employed.

Enrichment Factor (EF)

The Enrichment Factor (EF) in marine sediments is a tool used to evaluate the degree of contamination or pollution [15], [16]. by comparing the concentration of a specific element in the sediment to its natural background levels. Iron (Fe) was selected as the normalizing element for EF calculations, as it is primarily derived from sediments and is commonly used as a reference element [17]–[19], [10]:

Enrichment factor=(CnFe)Sample(CnFe)Background

where C_n is the concentration of the element “n.” The background value is that of average shale [10], [20]–[22]. The EF classification constitutes six categories (Table I), from background concentration to extremely high enrichment [10], [23].

Table I. Enrichment Classification

EF Value	EF classification
<1	No enrichment
1–3	Minor enrichment
3–5	Moderate enrichment
5–10	Moderately severe enrichment
10–25	Severe enrichment
25–50	Very severe enrichment
>50	Extremely severe enrichment

Contamination Factor (CF)

The contamination factor was proposed by [24] and determined experimentally, as the ratio between the elemental concentration of the sample and its background:

CF=M/MB

where M sample is the total metal concentration and MB background value represents the average background value shale [20]. The CF values were further classified [10], as follows (Table II).

Table II. Contamination Factor Classification

CF value	CF classification
CF <1	Low contamination
1 ≤ Cf < 3	1 ≤ Cf < 3 Moderate contamination
3 ≤ Cf < 6	Considerable contamination
Cf > 6	Very high contamination

Geo-Accumulation Index

The Geo-accumulation Index (Igeo), introduced by Muller [20], was used to evaluate the degree of metal pollution by comparing current concentrations to pre-industrial levels. It was calculated using the following equation as outlined by Rajan et al. [10] and Muller [20]:

Igeo=log2(Cn/1.5×Bn)

where C_n is the measured concentration of the heavy metals in the sediments, B_n is the geochemical background value in average shale of element n and 1.5 is the background matrix correction due to terrigenous effects. The Igeo classification comprises seven classes (0–6), ranging from unpolluted to extremely polluted (Table III).

Table III. Geo Accumulation Classification

Igeo value	Igeo classification
≤0	Uncontaminated
0–1	Uncontaminated to moderately contaminated
1–2	Moderately contaminated
2–3	Moderately to heavily contaminated
3–4	Heavily contaminated
4–5	Heavily to extremely contaminated
5–6	Extremely contaminated

Pollution Load Index (PLI)

The Pollution Load Index (PLI) was employed to assess the extent of heavy metal pollution in the environment. The PLI for each site was calculated using the method proposed by Tomlinson et al. [25]. The PLI for each sample was determined as follows:

PLI=(Cf1xCf2x,…,xCfn)1/n

where n represents the number of metals and C_f is the contamination factor, the PLI serves as a powerful tool for evaluating heavy metal pollution. According to [10], [17], [18] a PLI value greater than 1 indicates pollution, whereas a PLI value less than 1 signifies no pollution.

Results and Discussion

Chemical Analysis of Heavy Metals

Confined Areas

Confined areas are designated spaces where environmental conditions, such as water flow and exchange, are restricted, often including lagoons, bays, narrow channels. These areas are frequently impacted by nearby industries and wastewater outfalls, leading to limited dispersion of pollutants and potential accumulation of contaminants. Confined areas showed high and very high susceptibility due to their low flushing capacity [26].

The selected confined areas include four sites (Fig. 1). Al Salmiyah Channel (Site 1), Mussafah South Channel (Site 2), Mussafah Industrial Area (Site 3), and Al Muzoon Channel (Site 201). The heavy metals in sediment were analysed for Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn, and Hg, measured in mg/kg (Table IV). Site 1 (Al Salmiyah Channel) exhibited lower maximum and minimum concentrations, such as Cu (1.55 mg/kg–17.14 mg/kg) and Zn (7.69 mg/kg–33.66 mg/kg), reflecting limited human impact and relatively low contamination. Only Ni has exceeded the AD QCC 2017/18 [27] standards level. Site 2 (Mussafah South Channel) recorded the highest maximum concentrations of several metals, including Cr (40.49 mg/kg), Cu (44.92 mg/kg), and Zn (164.5 mg/kg), indicating significant contamination likely due to industrial influences and discharge runoff in this area. This confined area is of eutrophic nature, under pressure due to receiving approximately 400,000 m³ of treated sewage day [28]. The Cd, Cu, Pb, and Zn exceeded the AD QCC 2017/18 [27] Standard levels. Cd, Cu and Ni exceeded the AD QCC 2017/18 [27] standards in Site 3 (Mussafah Industrial Area) and also showed metal levels, with Cr concentrations ranging from 14.97 mg/kg to 36.11 mg/kg and Cu from 2.59 to 29.24 mg/kg, indicating industrial influence, though not as severe as in Site 2. The concentration of metals Site 201 (Al Muzoon Channel) such as Cr ranged from 20.52 mg/kg to 35.79 mg/kg, while Cu levels varied between 3.16 mg/kg and 19.59 mg/kg. Zn concentrations ranged from 14.61 mg/kg to 58.86 mg/kg, with a mean of 36.03 mg/kg, indicating moderate pollution compared to the very high levels observed in Site 2. The maximum Ni concentration was 30.2 mg/kg, which exceeded the AD QCC 2017/18 [27] standards. The Hg concentrations consistently below the detection limit in all the sampling sites in confined areas.

Table IV. Heavy Metals Minimum, Maximum and Mean -Site Wise

Categories	Site		Cd	Co	Cr	Cu	Fe	Mn	Ni	Pb	Zn	Hg
Confined areas	Site 1	Min	0.08	0.52	7.21	1.55	1122	28.11	0	0.07	7.69	ND
		Max	0.65	2.74	26.39	17.14	5883	152.7	17.26	3.07	33.66	ND
		Mean	0.42	1.91	18.49	7.43	3964.21	99.46	6.57	1.34	24.19	ND
	Site 2	Min	0.4	2.8	24.16	6.27	4995	73.49	0	0.08	21.8	ND
		Max	4.68	6.57	40.49	44.92	11460	282.9	32.54	24.37	164.5	ND
		Mean	1.33	3.75	32.24	23.03	7567.93	160.85	16.04	6.94	82.23	ND
	Site 3	Min	0.23	1.24	14.97	2.59	2721	65.4	0	0.77	11.75	ND
		Max	0.98	4.02	36.11	29.24	9470	200	22.26	5.63	87.67	ND
		Mean	0.54	2.35	25.25	12.38	5372.29	129.81	8.35	2.76	41.25	ND
	Site 201	Min	0.37	2.25	20.52	3.16	3711	43.87	3.8	0.66	14.61	ND
		Max	0.77	3.51	35.79	19.59	7535	198.3	30.2	7.31	58.86	ND
		Mean	0.53	2.84	28.29	9.74	5424.93	123.94	14.82	2.89	36.03	ND
Public beaches	Site 7	Min	0.28	2.02	15.11	1.24	3492	114.2	0	0.94	14.46	ND
		Max	0.73	2.83	34.46	7.47	6486	177.9	17.16	4.68	91.99	ND
		Mean	0.47	2.33	24.02	5.02	4815.86	144.95	8.11	2.09	31.47	ND
	Site 9	Min	0.07	0.33	5.09	2.16	951.9	18.84	0	0	4.94	ND
		Max	0.96	2.1	18.66	16.44	8652	80.1	15.35	3.15	54.06	ND
		Mean	0.30	1.01	12.49	8.22	3443.49	41.01	6.96	1.54	19.26	ND
	Site 107	Min	0.37	2.31	18.64	1.45	3568	72.1	2.95	0.41	17.06	ND
		Max	0.78	3.49	34.92	11.09	7969	199.9	23.78	1.99	31.47	ND
		Mean	0.52	2.68	26.45	6.61	5353.64	140.23	11.06	1.38	23.48	ND
Port & marinas	Site 11	Min	0.06	0.22	2.53	5.36	2338	23.05	0	0.37	4.36	ND
		Max	0.97	1.86	13.71	23.69	7752	62.95	7.85	2.87	63.1	ND
		Mean	0.37	0.98	10.43	15.93	3353.07	44.31	2.37	1.56	22.90	ND
	Site 12	Min	0	0.13	2.6	0.69	236.1	14.92	0	0	3	ND
		Max	0.28	1.43	12.25	4	3676	61.58	21.32	11.35	11.98	ND
		Mean	0.13	0.63	7.04	2.06	1672.03	35.60	7.11	4.46	6.88	ND
Near desalination plants	Site 13	Min	0.2	0.57	11.48	2.57	3423	65.29	0	0.22	8.15	ND
		Max	2.3	3.95	27.13	11.69	7710	167.1	19.37	3.99	49.35	ND
		Mean	0.62	1.96	19.40	7.40	4468.29	115.99	6.82	1.32	21.53	ND
	Site 14	Min	0	0.16	3.56	0	557.5	11.92	0	0	1.7	ND
		Max	0.22	1.14	15.02	3.66	6396	109.6	0.6	0.95	14.62	ND
		Mean	0.08	0.56	7.93	1.43	1763.93	46.22	0.09	0.37	5.47	ND
	Site 15	Min	0.02	0.13	3.22	0.7	499.6	14.62	0	0	2.23	ND
		Max	0.23	1.25	13.77	3.51	3087	55.6	31.09	5.76	8.5	ND
		Mean	0.10	0.64	8.20	2.14	1516.33	34.85	10.49	2.65	5.33	ND
Newly developed & developing area	Site 117	Min	0.11	0.63	8.5	1.05	2010	22.29	0	0.09	5.91	ND
		Max	1.09	2.13	31.58	9.9	8226	78.35	9.38	1.61	39.32	ND
		Mean	0.30	1.07	14.82	5.11	3163.43	47.28	3.24	0.87	17.22	ND
	Site 119	Min	0.02	0.48	0.19	0.8	1323	34.35	0	0.16	4.62	ND
		Max	0.51	2.96	29.52	8.38	5801	160	10.49	6.09	20.29	ND
		Mean	0.28	1.42	14.87	3.95	3312.11	90.37	2.68	1.69	12.79	ND
	Site 202	Min	0.25	1.91	20.25	1.78	3511	77.6	0	0.14	13.32	ND
		Max	2.56	4.6	47.05	13.84	18040	202.6	33.56	2.33	72.14	ND
		Mean	0.74	2.98	28.42	7.45	6834.07	145.45	16.28	1.25	33.42	ND
Natural habitats	Site 4	Min	0.13	0.78	7.99	2.12	1788	39.19	0	0.07	7.43	ND
		Max	1.24	2.5	23.04	17.31	3782	86.74	8.61	3.99	23.75	ND
		Mean	0.35	1.18	13.12	7.53	2457.57	59.66	2.76	1.19	14.28	ND
	Site 20	Min	0	0.43	4.27	1.78	515.9	27.05	0	0	4.37	ND
		Max	0.18	0.8	9.16	2.93	2097	36.62	7.52	4.74	6.78	ND
		Mean	0.11	0.60	7.14	2.37	1358.47	31.83	3.02	2.28	5.66	ND
	Site 21	Min	0	0	1.38	0.6	88.2	7.36	0	0	2.72	ND
		Max	0.04	0.19	4.94	1.24	712.9	15.15	0	3.74	3.77	ND
		Mean	0.03	0.09	3.45	0.91	403.45	10.77	0.00	1.81	3.11	ND
	Site 22	Min	0	0	1.56	0.49	172.7	10.64	0	0.4	2.06	ND
		Max	0.04	0.14	3.15	0.95	524.7	18.1	0	10.74	5.42	ND
		Mean	0.02	0.08	2.43	0.73	334.33	13.73	0.00	4.37	3.73	ND
	Site 123	Min	0	0.07	2.52	0	116.9	5.22	0	0	1.58	ND
		Max	0.13	1.03	11.88	2.43	1705	23.78	14.23	0.99	36.42	ND
		Mean	0.04	0.35	5.84	1.07	716.09	15.21	2.03	0.37	8.47	ND
Near	Site	Min	0	0.12	2.8	0.49	299.4	15.64	0	0	2.58	ND
nuclear	125	Max	0.3	0.96	14.96	3.41	2074	50.9	0	3.89	9.69	ND
power station		Mean	0.12	0.48	7.46	1.70	1077.70	30.19	0.00	1.81	5.48	ND
Reference	Site	Min	0	0	2.59	0.11	291.2	3.06	0	0.11	2.14	ND
area	126	Max	0.17	0.6	7.59	3.14	5846	24.39	11.36	2.25	12.35	ND
		Mean	0.08	0.30	5.02	1.30	1628.96	14.18	1.62	0.94	5.24	ND

The mean concentrations of heavy metals (Table V) in confined areas are generally below AD QCC 2017/18 [27] standards, indicating minimal environmental risk. Cd (0.60 mg/kg), Cr (21.89 mg/kg), Cu (10.83 mg/kg), Pb (3.04 mg/kg), Ni (9.34 mg/kg), and Zn (38.66 mg/kg) all fall well below their respective AD QCC 2017/18 [27] limits. Additionally, Hg is not detected, remaining far below the 0.2 mg/kg threshold. These results suggest that heavy metal contamination in confined areas is within safe levels according to AD QCC 2017/18 [27] guidelines.

Table V. Heavy Metals Mean Value Categories Wise

Categories	Cadmium (mg/kg)	Cobalt (mg/kg)	Chromium (mg/kg)	Copper (mg/kg)	Iron (mg/kg)	Manganese (mg/kg)	Nickel (mg/kg)	Lead (mg/kg)	Zinc (mg/kg)
Confined area	0.60	2.23	21.89	10.83	4744.09	106.60	9.34	3.04	38.66
Public beaches	0.42	1.97	20.91	6.73	4449.13	108.49	8.69	1.68	24.26
Port and marinas	0.31	0.88	9.64	12.56	2831.18	41.62	3.77	2.52	19.20
Near desalination plants	0.32	1.20	12.93	4.20	2762.85	74.49	4.65	1.15	12.55
Newly developing & development area	0.44	1.82	19.05	5.53	4389.12	95.08	7.66	1.29	21.29
Natural habitat	0.15	0.60	7.85	3.47	1299.36	31.80	1.82	1.55	8.87
Near nuclear power plant	0.12	0.48	7.46	1.70	1077.70	30.19	0.00	1.81	5.48
Reference	0.08	0.30	5.02	1.30	1628.96	14.18	1.62	0.94	5.24

These variations in metal concentrations across the four sites highlight the influence of localised industrial activities, with Site 2 experiencing the highest levels of pollution. Overall, metal concentrations across the confined area remain below the AD QCC 2017/18 [27] standards. However, Site 2 exceeded the standards for Cd, Cu, Pb, and Zn pointing to significant localized pollution from industrial sources. The increase in Cu, Ni, Zn, and Pb contents in sediments was related to the rapid urbanization and industrialization [29].

Public Beaches

Public beaches in coastal areas are recreational spaces accessible to the public, often featuring amenities for swimming, sunbathing, and various water sports. Beaches are important areas for recreation and tourism, and beachgoers generally select beaches on the basis of their perceived cleanliness [30]. A polluted beach is a public health risk and can inhibit economic growth of the community US EPA [31]. Under the Public Beach Categories (Fig. 1), sediment analysis from Sites 7 (Al Bateen Beach), Site 9 (Corniche Beach), and Site 107 (Fairmount Beach) shows different heavy metal contamination (Table IV), with some exceeding the AD QCC 2017/18 [27] standards for certain metals. Site 7 recorded the highest levels of concentrations among the public beach sites. Cr ranged from 15.11 mg/kg to 34.46 mg/kg, Cu from 1.24 to 7.47 mg/kg, and Zn from 14.46 mg/kg to 91.99 mg/kg. Notably, Cd and Ni exceeded the AD QCC 2017/18 [27] standard. Mn (max: 177.9 mg/kg) and Fe (max: 6 486 mg/kg) also exhibited considerable concentrations, Site 9 a popular recreational beach, exhibited lower contamination levels overall. Cr ranged from 5.09 mg/kg to 18.66 mg/kg, Cu from 2.16 mg/kg to 16.44 mg/kg, and Zn from 4.94 mg/kg to 54.06 mg/kg. While only Cd exceeded AD QCC 2017/18 [27] standards at this site, the levels of Fe (max: 8652 mg/kg) and Mn (max: 80.1 mg/kg) were also recorded. Site 107 has the levels, with Cr ranging from 18.64 mg/kg to 34.92 mg/kg, Cu from 1.45 mg/kg to 11.09 mg/kg, and ZN from 17.06 mg/kg to 31.47 mg/kg. These concentrations were well within AD QCC 2017/18 [27] standards except Cd and Ni. However, the maximum concentration of Mn (199.9 mg/kg) and Fe (7 969 mg/kg) were recorded.

The levels of heavy metals in all three sites from public beaches show variation across different elements. Notably, the mean concentrations (Table V) for Cd (0.42 mg/kg), Cr (20.91 mg/kg), Cu (6.73 mg/kg), Pb (1.68 mg/kg), Ni (8.69 mg/kg), and Zn (24.26 mg/kg) remain below AD QCC 2017/18 [27] standards, which are 0.7 mg/kg for Cd, 52 mg/kg for Cr, 20 mg/kg for Cu, 30 mg/kg for Pb, 16 mg/kg for Ni, and 125 mg/kg for Zn. However, Hg is not detected in the sampled sediments, while the AD QCC 2017/18 [27] standard is 0.2 mg/kg. Overall, the heavy metal concentrations in public beach sediments generally comply with the established guidelines.

Sediment analysis from Sites 7 (Al Bateen Beach), 9 (Corniche Beach), and 107 (Fairmount Beach) revealed varying heavy metal levels, with Site 7 showing the highest concentrations. While Cr, Cu, and Zn mostly remained within AD QCC 2017/18 [27] standards, Cd and Ni exceeded limits at certain sites, likely due to outfall runoff (approximately 500 m), nearby coastal development, and the extension of channel from confined areas. Due to discharge and landfill activities the heavy metals are two to four times higher in one kilometre from the landfill’s leachate discharge [32]. Hg was not detected. Despite some exceedances, the overall heavy metal concentrations in the beach sediments remained within AD QCC 2017/18 [27] guidelines, with localised sources contributing to higher levels at specific sites.

Port and Marinas

Ports play a central role in countries’ economic growth [33]. In general, ports generate environmental impacts through their various functions linked to cargo handling, connectivity to maritime and land transport networks, industrial and semi-industrial activities, logistics and distribution activities, and energy production and distribution [34]. Marinas, on the other hand, cater to recreational boats and yachts, providing docking, mooring, and servicing [35].

Two sites Site 11 (Port Mina Zayed) and Site 12 (Ruwais) were monitored under port and marinas categories (Fig. 1). At Site 11 the concentrations of heavy metals (Table IV) were as follows: Cd ranged from 0.06 to 0.97 mg/kg, Cr (2.53 mg/kg to 13.71 mg/kg), Cu (5.36 mg/kg to 23.69 mg/kg), Pb (0.37 mg/kg to 2.87 mg/kg), Ni (0 mg/kg to 7.85 mg/kg), and Zn (4.36 mg/kg to 63.1 mg/kg). Hg was not detected. At Site 12 (Ruwais), Cd ranged from 0 to 0.28 mg/kg, Cr (2.6 mg/kg to 12.25 mg/kg), Cu (0.69 mg/kg to 4 mg/kg), Pb (0 mg/kg to 11.35 mg/kg), Ni (0 mg/kg to 21.32 mg/kg) and Zn (3 mg/kg to 11.98 mg/kg). Hg was not detected. Compared to the AD QCC 2017/18 [27] standards, Site 11 exceeded the standards for Cd and Cu, while Site 12 exceeded the Ni standard.

The mean concentrations of heavy metals in the Port and Marinas category (Table V) were below compared to the AD QCC 2017/18 [27] standards. The mean concentrations of Cd (0.31 mg/kg), Cr (9.64 mg/kg), Cu (12.56 mg/kg), Pb (2.52 mg/kg), Ni (3.77 mg/kg), and Zn (19.20 mg/kg) However, the mean concentration of Hg (0 mg/kg) was below the detection limit, which is lower than the AD QCC 2017/18 [27] standard of 0.2 mg/kg.

The results revealed in Site 11, Cd and Cu levels exceeded the AD QCC 2017/18 [27] standards. Cd’s exceedance may be attributed to industrial activities and ship traffic in the port, which often involve the use of cadmium-containing materials. Similarly higher concentrations of Cd were recorded in the sediments of intertidal zone around the ship breaking area of Chittagong (Bangladesh) due to discharge of untreated effluents from ship breaking yards [36], [37]. Elevated Cu levels could be linked to marine antifouling paints, which are commonly used in ports to prevent biofouling on ships. Higher metal concentrations in the harbours compared to the reference sites, the leisure boat harbours accumulate metal contaminants as AF paints are one of the main sources of Cu leaching from boat coating [38].

At Site 12, nickel concentrations exceeded the standard. This could be due to industrial emissions, particularly from the nearby petrochemical and refining industries in Ruwais, where nickel is often used in catalytic processes and suggesting increasing industrial and maritime activity as potential contributing factors. Nickel play a positive role in refining, assisting in oil exploration, catalysing upgrading and producing petrochemicals with increasing environmental concerns [39]. Nickel is commonly used in welding operations and exist in antifouling paint residues and contents in the sediments near the port area are primarily sourced from ship repainting and repairs [40]. These exceedances raise environmental concerns, particularly for water and sediment quality in these areas. Hg was not detected at either site, or most other heavy metals remained within acceptable limits according to the AD QCC 2017/18 [27] standards.

Near Desalination Plants

Desalination is a multi-stage process that splits saltwater into two products: the product stream (freshwater) and the by-product stream highly concentrated brine [41]. The process typically involves intake of seawater, followed by filtration and reverse osmosis, this technology is essential for providing potable water in arid regions or areas with limited freshwater resources. Brine is an unavoidable product of seawater desalination and is commonly disposed of in oceans and seas, where it has negative effects on the surrounding marine environment and its biodiversity due to the resultant increased salinity and temperature, as well as the presence of chemicals [42]. Seawater desalination accounts for 61% of all freshwaters produced globally [42], [43].

Three sites (Site 13—Umm Al Nar, Site 14—Taweela, and Site 15—Mirfah) were monitored under the desalination plant category (Fig. 1). Site 13 showed significant heavy metal contamination, with Cd levels ranging from (0.2 to 2.3 mg/kg) and nickel from 0 mg/kg to 19.37 mg/kg, both exceeding AD QCC 2017/18 [27] standards. while Cr, Cu, zinc Mn was within acceptable limits (Table IV). Site 14 demonstrated significantly lower concentrations across all metals and within the AD QCC 2017/18 [27] standards, with Cd ranging from 0 mg/kg to 0.22 mg/kg, Co (0.16 to 1.14 mg/kg), Cr (3.56 mg/kg to 15.02 mg/kg), Cu (0 mg/kg to 3.66 mg/kg), nickel (0 to 0.6 mg/kg) and Pb (0 to 0.95 mg/kg) which indicating good sediment quality. Site 15 showed elevated nickel levels ranging from 0 mg/kg to 31.09 mg/kg, however, all other parameters (Table IV) were within AD QCC 2017/18 [27] standard limit.

The mean heavy metal concentrations (Table V) were as follows: Cd (0.32 mg/kg), Co (1.20 mg/kg), Cr (12.93 mg/kg), Cu (4.20 mg/kg) Iron (2 762.85 mg/kg), Mn (74.49 mg/kg), nickel (4.65 mg/kg), Pb (1.15 mg/kg), and zinc (12.55 mg/kg). Hg was not detected. Overall, the heavy metals mean concentration of sites in desalination plant categories were within the AD QCC 2017/18 [27] standards (Cd 0.7 mg/kg, Cr 52 mg/kg, Cu 20 mg/kg, Pb 30 mg/kg, nickel 16 mg/kg, zinc 125 mg/kg and Hg 0.2 mg/kg).

This category revealed that Site 13 had significant heavy metal contamination, with Cd and nickel exceeding AD QCC 2017/18 [27] standards. Major source of input of nickel into the marine environment is the corrosion of Cu, nickel pipes and fittings used extensively in this area whereas desalination/power plants and cooling system utilizing water [44]. In contrast, Site 14 showed all metal concentrations within acceptable limits, indicating good sediment quality. Site 15 had elevated nickel levels but met standards for other parameters. Overall, the mean concentrations of heavy metals across the sites fell within AD QCC 2017/18 [27] standards, suggesting that while some sites face contamination risks, this variation results from differences in local activities, runoff, and sedimentation processes affecting the sites. [45], confirmed an accumulation of high levels of Cd, and other metals in sediments at the proximity of a seawater desalination plant in Saudi Arabia. This fact is well supported by [46], who documented localized pollution of Cu, Cr, Fe and Ni in coastal sediments of Oman due to effluent discharges from power/desalination plants.

Newly Developed Areas

Refers to the development that humans create along a coastline for the purpose of increasing tourism, include building hotels, removing forests or seagrass to create larger beach spaces, and building marinas for storage and access of boats. Also, development along the coast impacts the natural landscape and the coastal ecosystem [47]. These developments can increase environmental pressures through land-use changes, pollution, and habitat disruption.

Sediment samples (Fig. 1) were collected from three sites (Site 117—Reem Island, Site 119—Hudariyat Island and Site—202 Al Muneera). In site 117, the concentrations of heavy metals in sediment were as follows (Table IV): Cd ranged from 0.11 mg/kg to 1.09 mg/kg, Co (0.63 mg/kg to 2.13 mg/kg), Cr ranged (8.5 mg/kg to 31.58 mg/kg), Cu (1.05 mg/kg to 9.9 mg/kg), iron (2010 mg/kg to 8226 mg/kg), Mn (22.29 mg/kg to 78.35 mg/kg), Ni (0 mg/kg to 9.38 mg/kg), Pb (0.09 mg/kg to 1.61 mg/kg), and zinc (5.91 mg/kg to 39.32 mg/kg), Hg was not detected. At Site 119 (Hudariyat), Cd ranged from 0.02 mg/kg to 0.51 mg/kg, Co ranged from 0.48 mg/kg to 2.96 mg/kg, Cr ranged from 0.19 to 29.52 mg/kg, Cu ranged from 0.8 mg/kg to 8.38 mg/kg, iron ranged from 1.323 mg/kg to 5.801 mg/kg, Mn ranged from 34.35 mg/kg to 160 mg/kg, Ni ranged from 0 mg/kg to 10.49 mg/kg, Pb ranged from 0.16 mg/kg to 6.09 mg/kg and Zn ranged from 4.62 mg/kg to 20.29 mg/kg. Hg was also not detected. At site 202 Cd ranged from 0.25 mg/kg to 2.56 mg/kg, Co (1.91 mg/kg to 4.6 mg/kg), Cr (20.25 to 47.05 mg/kg), Cu (1.78 mg/kg to 13.84 mg/kg), iron (3 511 to 18 040 mg/kg), Mn (77.6 mg/kg to 202.6 mg/kg), Ni (0 to 33.56 mg/kg), Pb (0.14 mg/kg to 2.33 mg/kg), and Zn (13.32 to 72.14 mg/kg), Hg was not detected. Compared to AD QCC 2017/18 [27] standards, all heavy metals were within the acceptable limits except Cd in sites 117 and 202 in addition Ni in site 202.

In the “Newly Developed” area, the mean concentrations of heavy metals (Table V) generally fall below the AD QCC 2017/18 [27] standards for sediment quality. Cd levels average 0.44 mg/kg, well within the limit of 0.7 mg/kg, while Cr and Cu show mean values of 19.05 mg/kg and 5.53 mg/kg, both significantly below their respective limits of 52 mg/kg and 20 mg/kg. Pb and Ni also remain far below the regulatory thresholds, with mean concentrations of 1.29 mg/kg and 7.66 mg/kg, compared to their limits of 30 mg/kg and 16 mg/kg, respectively. Notably, Hg was not detected in the samples, maintaining a concentration of 0 mg/kg against the 0.2 mg/kg standard.

The sediment samples from newly developed coastal areas show that most heavy metals, such as Cr, Cu, Pb, and zinc, are well within AD QCC 2017/18 [27] standards. However, elevated levels of Cd at Sites 117 and 202, and Ni at Site 202, exceed the recommended limits, indicating potential environmental concerns. Hg was not detected across all sites. The elevated Cd and Ni levels are likely due to industrial runoff, construction activities, and marine traffic near the coastal areas may also contribute to the contamination. Cd is highly toxic and originates from anthropogenic activities. It was found that more than 90% of Cd in marine environments is of anthropogenic origin [48], similarly highest content of Ni was recorded at Al Khowkhah and Al-Mokha regions, the high Ni concentrations are certainly anthropogenic from the direct human impact from the boats [48].

Natural Habitats

Natural habitats are land and water areas where the ecosystems’ biological communities are formed largely by native plant and animal species, and human activity has not essentially modified the area’s primary ecological functions. All natural habitats have important biological, social, economic, and existence value. Important natural habitats may occur in natural arid and semi-arid lands; mangrove swamps, coastal marshes, and other wetlands; estuaries; seagrass beds; coral reefs; freshwater lakes and rivers [49].

Sediment samples were collected from 4 sites under natural habitat categories (Fig. 1). At Site 4 (Eastern Corniche), Site 20 (Marawah), Site 21 (Butinah), Site 22 (Al Yasat), and Site 123 (Ras Al Gananda) reveal generally low heavy metal concentrations, with most values below AD QCC 2017/18 [27] standards. These areas represent important natural habitats, including marine reserves and protected zones. At Site 4 (Eastern Corniche), Cd ranged from 0.13 mg/kg to 1.24 mg/kg, slightly exceeding the AD QCC 2017/18 [27] limit of 0.7 mg/kg in some samples, while other metals like Cr (7.99 mg/kg to 23.04 mg/kg), Cu (2.12 mg/kg to 17.31 mg/kg), and zinc (7.43 mg/kg to 23.75 mg/kg) remained well within acceptable ranges. At Site 20 (Marawah), a marine protected area, heavy metals like Cd (0 to 0.18 mg/kg) and Ni (0 mg/kg to 7.52 mg/kg) were minimal, and all other metals, including Cu and zinc, were well below the thresholds. Site 21 (Butinah), a UNESCO biosphere reserve, had very low heavy metal concentrations, with Cd at 0 mg/kg to 0.04 mg/kg and no detectable Ni. Similarly, Site 22 (Al Yasat) and Site 123 (Ras Al Gananda), both critical marine habitat areas, showed minimal contamination, with Cr, Cu, and zinc remaining far below the standard limits. No Hg was detected at any of these sites (Table IV), indicating the natural habitats are relatively unimpacted by industrial pollution, except for a slight Cd elevation at Site 4.

Overall, the mean concentrations of heavy metals (Table V) in natural habitats reveal that Cd has a low mean value of 0.15 mg/kg, while Co and Ni show mean values of 0.60 and 1.82 mg/kg, respectively. Cr (7.85 mg/kg), Cu (3.47 mg/kg), and iron (1 299.36 mg/kg) are moderately present. Mn follows with a mean of 31.80 mg/kg, while zinc averages 8.87 mg/kg. Pb remains relatively low at 1.55 mg/kg, and no detectable Hg levels were found. These mean values suggest that the sediment quality in the natural habitat sites generally were within the AD QCC 2017/18 [27] standards.

The sediment samples from Sites 4, 20, 21, 22, and 123 showed generally low heavy metal concentrations, with most values below AD QCC 2017/18 [27] standards. Cd slightly exceeded the limit at Site 4, this might be due to the outfalls influence and anthropogenic activities nearby the sites. More than 90 % of Cd in marine environments is of anthropogenic origin [48], but other metals like Cr, Cu, and zinc remained within safe ranges. No Hg was detected at any site, indicating minimal industrial pollution. Overall, sediment quality across the natural habitats was within standard limits, indicating a relatively unimpacted environment.

Near Nuclear Power Plant

It is a facility like any other power plant in that steam is produced to run a turbine generator to make electricity. However, its major difference is that the heat used to make the steam is produced from uranium [50]. The cooling process involves drawing large amounts of seawater, circulating it to absorb heat generated by the nuclear reactor, and then discharging the warmed water back into the ocean.

Only one site (Site 125) was monitored, and sediment samples were collected near the nuclear power plant (Fig. 1). The analysed heavy metals (Table IV) were compared against AD QCC 2017/18 [27] standards for sediment quality. The concentrations of heavy metals were as follows: Cd (0 mg/kg to 0.3 mg/kg), Co (0.12 to 0.96 mg/kg), Cr (2.8 mg/kg to 14.96 mg/kg), Cu (0.49 to 3.41 mg/kg), Pb (0 to 3.89 mg/kg), and Zinc (2.58 mg/kg to 9.69 mg/kg). Ni and Hg were not detected. Overall, the heavy metal concentrations analysed at Site 125 remained within the standard limits.

The mean heavy metal concentrations (Table V) at Site 125, near the nuclear power plant, were within the AD QCC 2017/18 [27] sediment quality standards, with no detection of Ni or Hg, indicating good and unpolluted sediment quality.

Reference Area

Reference site as a site whose condition is a suitable baseline or benchmark for assessment and management of sites in similar water bodies. Reference sites, in contrast, are those that are considered to represent pristine environments [51]. This area typically presents minimal anthropogenic influence, allowing to understand the natural variability of water quality parameters such as nutrient levels, pollutant concentrations, and biodiversity.

Site 126 was a reference site for evaluating heavy metal concentrations (Table IV) in sediment. The measured levels of heavy metals at this site were compared against the AD QCC 2017/18 [27] standards for sediment quality. Cd concentrations ranged from 0 mg/kg to 0.17 mg/kg, were well below the standard of 0.7 mg/kg. Cr levels varied from 2.59 mg/kg to 7.59 mg/kg, significantly lower than the 52 mg/kg threshold. Cu concentrations were found between 0.11 mg/kg and 3.14 mg/kg, well within the 20 mg/kg limit. Pb levels ranged from 0.11 mg/kg to 2.25 mg/kg, also under the 30 mg/kg standard. Ni was detected at a maximum of 11.36 mg/kg, remaining below the 16 mg/kg guideline, while zinc levels ranged from 2.14 mg/kg to 12.35 mg/kg, were within the 125 mg/kg standard limits. Hg was not detected and below the 0.2 mg/kg standard limit. Overall, the heavy metal concentrations at Site 126 with in the standards. Site 126 provided effective information as a reference site, with heavy metal concentrations in sediment consistently falling within AD QCC 2017/18 [27] standards. All measured metals, including Cd, Cr, Cu, Pb, Ni, Zn, and Hg, were below the established limits, indicating a good sediment quality in the marine environment.

Assessment of Sediment Pollution Levels

The level of heavy metal contamination from both natural and anthropogenic sources in the Abu Dhabi coast, was determined based on the complete assessment of sediment samples in the study area. four assessments, namely EF, CF, Igeo, and PLI, were used to obtain the pollution level of the sampling sites.

Enrichment Factor (EF)

The enrichment factor (EF) is commonly used to distinguish the natural and anthropogenic sources of elements deposited in certain regions and to evaluate the degree of pollution caused by anthropogenic emissions [52]. EF data shows significant variation in metal contamination and pollution levels across different sites (Fig. 2). Sites like Al Muneera (Site 202) and Mussafah South Channel (Site 2) stand out with notably high EF values for Cd, indicating “very severe enrichment” (EF values of 25.97 and 24.13, respectively). This suggests considerable anthropogenic contamination, likely from industrial or urban runoff. Al Bateen Beach (Site 7) also shows “severe enrichment” for Cd (EF of 21.86) and “moderate to moderately severe enrichment” for Cr, Co, Cu, manganese, Ni, and zinc. The data for Al Salmiyah Channel (Site 1) and Port Mina Zayed (Site 11) also show “severe enrichment” for Cd (16.36 at both sites), while metals like Pb and zinc present “moderate to moderately severe enrichment” across several locations, indicating more widespread, though varying, contamination patterns. These results highlight the need for focused pollution control measures in highly enriched areas. On the other hand, sites like Butinah (Site 21), Al Yasat (Site 22), and Ras Ghanadah (Site 123) exhibit very low EF values for most metals, often falling below 1, indicating “no enrichment” or “minor enrichment”. These sites appear relatively minimal anthropogenic impact.

Fig. 2. Enrichment Factor in different sites.

The mean EF values (Fig. 3) from different categories reveals the levels of heavy metal contamination. Confined Areas exhibit “severe enrichment” for Cd (EF = 18.01), “moderate enrichment” for zinc (EF = 3.94) and minor enrichment for other metals. Desalination Plants show “moderate enrichment” for Cd (EF = 9.80) and “minor enrichment” for most other metals. Cd displayed the highest EF value among the eight metals investigated [53]. Development areas show “moderate enrichment” for Cd (EF = 12.18) and zinc (EF = 2.34). Natural Habitats display the lowest contamination, with most metals showing “no enrichment” (e.g., Cd EF = 4.75, zinc EF = 1.03). Nuclear Power Plant sites have “minor enrichment” for Cd (EF = 3.88) and little for other metals. Ports and Marinas exhibit “moderate enrichment” for Cu (EF = 3.76). Public Beaches demonstrate “moderate to severe enrichment” for Cd (EF = 10.69). The Reference Site shows no enrichment across all metals, with most EF values below 1.

Fig. 3. Enrichment Factor in different categories.

Based on the EF values, Confined areas rank highest in metal enrichment, particularly for Cd and zinc, followed by Desalination Plants and Ports and Marinas rank next, showing moderate enrichment for Cd and Cu. The EF results revealed that the higher values for Cd are primarily attributable to contamination from metal-based industries such as electroplating and metallurgy, as well as automobile exhaust [54]. In contrast, near nuclear power plant, Natural Habitats and Reference site rank lowest, reflecting minimal enrichment across all measured metals.

Contamination Factor (CF)

The Contamination Factor (CF) data (Fig. 4) provides a detailed levels of metal contamination across various sites. Al Salmiyah Channel (Site 1) shows moderate contamination for Cd (CF = 1.42) and low contamination for all other metals, Mussafah Industrial Area (Site 3) reflects moderate contamination for Cd (CF = 1.77) but low contamination for the other metals, including Cu and Ni.

Fig. 4. Contamination Factor -Site wise.

Mussafah South Channel (Site 2) stands out with “considerable contamination” for Cd (CF = 3.78), showing significantly higher contamination than many other sites. It also exhibits moderate contamination for Cu (CF = 0.50) and zinc (CF = 0.85). Meanwhile, Al Muzoon Channel (Site 201) follows a similar trend with moderate Cd contamination (CF = 1.76) and low contamination for other metals like Pb and zinc. Al Muneera (Site 202) presents moderate Cd contamination (CF = 2.10) but low levels of other metals like Pb (CF = 0.06) and zinc (CF = 0.34).

Eastern Corniche (Site 4) is one of the most contaminated sites, with “very high contamination” for Cd (CF = 11.70) and “considerable contamination” for other metals, such as Cr (CF = 1.70) and zinc (CF = 1.78). This suggests significant anthropogenic activity impacting the area. Port Mina Zayed (Site 11) also shows moderate contamination for Cd (CF = 1.15) and Cu (CF = 0.36), but low contamination for the remaining metals.

Public beaches like Al Bateen Beach (Site 7) exhibit moderate Cd contamination (CF = 1.54) and low contamination for other metals. Corniche Beach (Site 9), Reference (Site 126), Butinah (Site 21), Al Yasat (Site 22), Marawah (Site 20), Ruwias (Site 12), Ras Ghanadha (Site 123) and Barakah (Site 125) have the lowest contamination overall, with CF values mostly below 0.2, showing minimal human impact.

The mean contamination factors (CF) for different categories (Fig. 5) indicate different levels of metal pollution. The highest mean values are observed in Confined Areas, particularly for Cd (2.18), followed by Public Beaches (1.37) and Development Areas (1.30), which fall into the moderate contamination category (1 ≤ Cf < 3). But the other categories Port and Marinas, Desalination Plants, Natural Habitats, Nuclear Power Plants and Reference exhibit low contamination levels in all parameters like Cd, Co, Cr, Cu, Iron, Manganese, Ni, Pb, and Zinc.

Fig. 5. Contamination Factor in different categories.

The analysis of the contamination factors (CF) reveals varying levels of metal pollution across different sites, with significant concerns regarding Cd contamination in several areas. Notably, Eastern Corniche exhibits very high Cd contamination and Mussafah south channel shows considerable contamination indicating severe anthropogenic impacts. In contrast, locations from Natural habitat, near nuclear power plant and Reference show low contamination, reflecting lower human influence. Overall, while confined areas display moderate mean contamination levels, most other categories maintain low contamination, highlighting the need for targeted monitoring and remediation efforts in the more affected sites.

Geo Accumulation Index (Igeo)

The geo-accumulation indices of all metals (Fig. 6) indicate that, only 5 out of 22 site is uncontaminated to moderately contaminated level comparing to [20], [10]. However, the geo-accumulation index for Cd reached 1 in the Mussafah South Channel (Site 2), followed by Al Muzoon Channel (Site 201) at 0.20, Al Muneera (Site 202) at 0.18, Mussafah Industrial Area (Site 3) at 0.17, and Fairmount Beach (Site 107) at 0.14. These values suggest Cd levels reached the “uncontaminated to moderately contaminated” category. The heavy metals Cd pollution tends to be higher possibly due to anthropogenic inputs such as untreated sewage discharge, fertilisers, pharmaceuticals, paints [55]. All other sites geo accumulation index were at uncontaminated levels.

Fig. 6. Geo Accumulation Index in different sites.

Overall, based on the geo-accumulation index across categories (Fig. 7), only Cd in confined areas reached the “uncontaminated to moderately contaminated” level. This finding is like the study in the South-western Bay of Bengal [55]. All other categories such as Desalination Plants, Development Areas, Ports and Marinas, Public Beaches, Nuclear Power Plants, Natural Habitats, and Reference areas, remained below the “uncontaminated” classification for all metals. This suggests that, apart from confined areas, the overall metal pollution across most categories is minimal.

Fig. 7. Geo Accumulation Index in different categories.

Pollution Load Index (PLI)

The Pollution Load Index (PLI) was calculated (Fig. 8), and eight sites were identified as polluted based on the criteria of [25], [10]. The highest pollution levels were observed in Mussafah South Channel (Site 2), followed by Al Muzoon Channel (Site 201), Al Muneera (Site 202), Mussafah Industrial Area (Site 3), Fairmount Beach (Site 107), Al Bateen Beach (Site 7), Umm Al Nar (Site 13), and Al Salamiyah Channel (Site 1). All other sites calculated, indicated no pollution.

Fig. 8. Pollution Load Index in different sites.

The mean value of the PLI of the different categories showed (Fig. 9), Confined area and public beaches indicates pollution. The other categories such as Desalination Plants, Development Areas, Ports and Marinas, Nuclear Power Plants, Natural Habitats, and Reference areas remained no pollution.

Fig. 9. Pollution Load Index in different categories.

The Pollution Load Index (PLI) analysis indicates that pollution is present in confined areas and public beaches, with Mussafah South Channel (Site 2) having the highest pollution levels. Other categories, such as Desalination Plants, Development Areas, Ports and Marinas, Nuclear Power Plants, Natural Habitats, and Reference areas, showed no pollution. Overall, the pollution is localized, mainly affecting confined areas and public beaches, while most other categories remain unaffected.

Conclusion

The comprehensive analysis of sediment quality from 22 sites in the Abu Dhabi coastal areas reveals a distinct variation in heavy metal contamination across different site categories. Confined areas, including Mussafah South Channel (Site 2), Al Muzoon Channel (Site 201), and Mussafah Industrial Area (Site 3), exhibited the highest pollution levels, particularly for Cd, Cu, Pb, and zinc. These findings supported with the Pollution Load Index (PLI) and Enrichment Factor (EF) results, illustrates that confined areas are significantly affected by industrial activities, runoff, and maritime traffic. Site 2 showed the most considerable contamination, indicating the urgent need for targeted pollution control and remediation strategies in these localized hotspots. Public beaches, such as Al Bateen Beach (Site 7) and Fairmount Beach (Site 107), also revealed moderate levels of contamination, especially for Cd and Ni. The proximity of these areas to confined channels and coastal developments likely contributes to the accumulation of metals observed in the sediments. However, despite some exceedances, overall heavy metal concentrations in public beaches remained largely within acceptable limits.

In addition, areas near desalination plants, development areas, ports and marinas exhibited generally lower contamination levels. While some sites, like Port Mina Zayed (Site 11) and Ruwais (Site 12), showed moderate exceedances in metals like Cd and Ni, the overall impact was less severe compared to confined areas. Natural habitats, reference areas, and the site near the nuclear power plant showed minimal to no contamination, with most metals falling well within the (AD QCC 2017/18) standards. The Geo-Accumulation Index (Igeo) further supports the conclusion that Cd is the primary metal of concern, particularly in confined areas, where it reached the “uncontaminated to moderately contaminated” category. Cd is a common by-product of various industrial processes, including metal plating, and pigments, which are known to contribute to its accumulation in sediments. Other metals, as well as most other sites across all categories, were found to be uncontaminated. Overall, the study highlights the importance of localized monitoring and mitigation strategies, particularly in confined industrial areas and public beaches where the risk of contamination is at its highest. Meanwhile, areas such as desalination plants, ports, marinas, and natural habitats remain relatively unimpacted by heavy metal pollution, maintaining good sediment quality.