1.2 Laboratory analyses

1.2.1 Granulometric analysis

The collected samples were packed in labeled polyethylene bags and immediately transported in ice-cooled box to the laboratory. At the laboratory, these samples were air-dried, disaggregated, and about 100 g of the pre-dried samples were sieved each one phi (Ø) interval to obtain textural properties according to Folk (1974). Seven fractions were obtained: gravel (Ø−1 > 2.00 mm), very coarse sand (Ø0 = 2.00 to 1.00 mm), coarse sand (Ø1 = 1.00 to 0.50 mm), medium sand (Ø2 = 0.50 to 0.25 mm), fine sand (Ø3 = 0.250 to 0.125 mm), very fine sand (Ø4 = 0.125 to 0.063 mm) and mud “silt & clay” (Ø5 < 0.063 mm).

1.2.2 Geochemical analysis

For analysis of carbonate content and total organic matter, about 10 g of pre-dried bulk sediments were completely grinded using agate mortar. The carbonate contents were determined by the method described by Gross (1971) depending on acid-treatment weight-loss. One gram of each powdered sample was treated with 1N HCl acid then the remaining insoluble residue was washed, dried at 60°C in oven, reweighted and the weight loss was converted into carbonate percentage. The total organic matter (TOM) was determined by the ignition loss of one gram from powdered samples at 550°C (Dean, 1974). The difference in weight was calculated as organic matter percentage.

The leachable forms of heavy metals were determined in the finest fractions of the collected samples (Ø3, Ø4 and Ø5). From each fraction, 0.5 g was digested with a mixture of concentrated HNO3 and HClO3 (3:1) then evaporated to near dryness. The digested samples were filtered and diluted with de-ionized water (Chester et al., 1994). This method is adopted to determine the leachable heavy metals (oxides, hydroxides, carbonates and sulphides). The concentrations of: Co, Cu, Zn, Ni, Cd, Mn, Fe and Pb were determined using flame Atomic Absorption Spectrophotometer (AAS, GBC-932) at the National Institute of Oceanography and Fisheries (NIOF), Hurghada, Egypt. To insure maximum accuracy, precision of the methods was confirmed by analysis of replicate measurements for each metal in the sediments sample. The obtained results showed a satisfied precision of 3.9 –16.1. In addition, the AAS was adjusted to provide mean value of triplicate measurements of each metal and the results were expressed in µg/g. the zero level of the AAS were adjusted by blanks and the quality control tools were adopted to avoid possible contamination, meanwhile, the chemical reagents are of high analytical grade and all of glassware were washed with diluted acid and later rinsed with double-distilled water before use.

1.3 Sediment quality guidelines and Ecological Risk indices

Biological adverse effects were evaluated by comparing levels of the measured heavy metals with the numerical sediment quality guidelines (SQG’s) proposed by Persuad et al. (1992). Two levels of risk were estimated; the lowest effect level (LEL) and the sever effect level (SEL). The contamination status was assessed by comparing the results of present study with available data given in previous literatures for leachable heavy metals in sediments from various ports worldwide.

Several indices have been applied to assess the ecological risk of heavy metals in various aquatic environments (Fujita et al., 2014) including; metal pollution load index (MPI) (Tomlinson et al. 1980), enrichment factor (EF) (Salomons and Förstner, 1984), and the geo-chemical index (Igeo) (Müller, 1979). The interpretation of these indices is depending on the comparison with a background levels. Rubio et al. (2000) have concluded that the use of regional background values gives more appropriate results than the global background values, consequently the mean results of Hanna (1992) for the sediments collected from the Red Sea during 1943 were used to calculate the background values.

1.4 Statistical analysis

All statistics were performed using Statistica 10 and Wingraph Prism 7. One-way analysis of variance (ANOVA) was applied to test significant variation in metal distribution between sites, and comparing levels of metals between different fractions. To explore potential association between heavy metals and relationship among variables, Pearson's correlation matrix and principal component analysis (PCA) were used.

2 Results and Discussions

2.1 Sediments characteristics

It has been reported that many characteristics of the marine sediments such as texture, organic matter and carbonate content may influence the distribution of metals in sediments (Chen et al., 2007). The granulometry of marine sediments at the different ports is illustrated in Figure 2. It can be noticed that the texture of all studied stations was sandy. At Hurghada, the total of the finest fractions (Ø3, Ø4 and Ø5) was varied between 36.26% in fishing port and 83.47% in front of passenger port; at Safaga, the fine fractions percentage was fluctuated between 46.32% in passenger wharf and 73.17% in the marine area off bauxite wharf with significant for Ø4; meanwhile at the old port of Qusier, these percentage was varied from 59.83% to 64.69% with nearly equal occurrences for Ø3 and Ø4. The recorded high percentages of the fine fractions Ø3, Ø4 and Ø5 at the different ports indicating to different sources of depositions mostly from the maritime activities, terrestrial runoff, phosphate shipments and the nearby land based activities. Dar et al. (2016b) found the average percentages of finest sediments (Ø3, Ø4 and Ø5) between 24.21% and 88.88 % with strong occurrence for Ø4 at Hurghada, and from 37.47% to 48.14% at Safaga with strong occurrence for Ø3. They indicated that the high occurrence of fine sediments at Hurghada and Safaga to the deposition under calm conditions due to the natural protections by the shallow coral terraces and the frontal islands. Madkour and Dar (2007) reported that Ø4 has significant occurrence at the tidal flat area off Hurghada Harbour. Mansour et al. (2013) attributed the high fine sediment contents in front of Hurghada to the terrigenous inputs, landfilling and dredging operations.

Figure 2 Distribution patterns of the different size fractions and the percentages of the finest fractions Ø3, Ø4 and Ø5 at the studied ports

2.2 Geochemical characteristics

2.2.1 Carbonates and total organic matter (TOM)

Table 1 shows the measured carbonate and total organic matter (TOM) percentages at the different stations. The studied stations at Hurghada ports recorded the highest percentages of carbonates which was varied between 51.62 and 76.65% indicating that the biogenic source materials constituted significant portion of the sea sediments; Safaga wharfs recorded significant variations in the carbonate percentages between less than 10% at grains and passenger wharfs and 59.52% at quartz and orthoclase wharf; while the carbonate percentage was less than 50% at the old port of Qusier. These data illustrated that the biological productions in the marine area off Hurghada and Qusier have strong contribution in the high carbonate percentage; while the effects of maritime activities and terrestrial runoff of terrigenous materials were the main reasons in carbonate percentage declining at Safaga ports. Significant variations were observed in TOM contents at Hurghada and safaga ports due to the local effects of the anthropogenic effluents. At Hurghada it was varied between 2.48% in marina and 8.78% in the fishing port, while at Safaga varied between 1.91% in grains wharf and 10.09% at coal wharf. On the other hand, the old port of Qusier recorded insignificant variation in TOM percentages which ranged from 2.79 to 3.73%. The recorded variation in the total organic matter (TOM) in bottom sediments of the studied ports at Hurghada and Safaga is usually related to the local hydrodynamics, algal and seagrass flourishing, the terrigenous and domestic wastewater. Mansour et al. (2013) attributed the recorded TOM at Hurghada to the seagrass patches and the algal bottom faces.

2.2.2 Distribution of leachable heavy metals and evaluation the biological risk

At Hurghada, the finest fraction Ø5 was the essential heavy metal carrier followed by Ø4 at the different ports except passenger port, which was followed by Ø3. The marine area off Hurghada shipyard recorded significantly high Fe, Mn, Zn, Cu, Ni and Pb in the finest fraction Ø5 (6556, 108.17, 330.38, 298.4, 91.40 and 101.02 µg/g, respectively), meanwhile tourist marina recorded the lowest values. Fishing berth was followed the shipyard in the heavy metal contents in the different fractions (Table 1). The metal accumulation at Hurghada ports was follow the sequence Ø5> Ø4> Ø3. Dar et al. (2016b) and Madkour and Dar (2007) attributed the high accumulation of heavy metals in the marine sediments off the shipyards to the repairing, maintaining, antifouling paint remains and ship constructing. At Safaga, Fe showed relatively high values at the different wharfs relative to Hurghada and Qusier due to the high amount of terrestrial runoff. The highest Fe and Cu were recorded in Ø5 (7483 and 62.58 µg/g, respectively) followed by Ø4 (6813 µg/g) for Fe at the grain wharf and Ø5 (54.70 µg/g) for Cu at passenger terminal; the highest Mn was observed at passenger warf in Ø5 (306.3µg/g) followed by bauxite wharf in Ø3 (291.82 µg/g). The highest Zn in Ø3 (126.6 µg/g) followed by Ø5 (109.17 µg/g) was showed in front of bauxite wharf. The highest Ni was in Ø3 (36.13 µg/g) in front of coal wharf, Pb was in Ø5 (22.52 µg/g) at orthoclase and quartz wharf, meanwhile Co was observed in Ø5 (5.5 µg/g) at the navigation basin of bauxite wharf. The recorded Cd at all wharfs was less than 2 µg/g. Dar et al. (2016b) concluded that the high Zn and Mn at Safaga marine area attributed to the high quantities of pollutants rich in Zn from antifouling paint remains and Mn from the terrestrial runoff from the phosphate shipments. At Qusier, the highest Fe and Zn was showed at the fishing basin in Ø5 (6207 and 80.53 µg/g, respectively) followed by Ø3 (5601 and 72.78 µg/g, respectively), the highest Mn and Cu was showed in Ø5 (233.7 and 34.45 µg/g, respectively) in front of the old port. The highest Ni was recorded in Ø3 (73.30 µg/g) and Co was in Ø4 (5.85 µg/g) at the fishing basin, meanwhile Cd recorded the highest content in Ø5 (4.19 µg/g) at the old port. The marine area off the old port and fishing basin were highly affected by the terrestrial runoff from the subsurface wastewater and coastal activities. The accumulation sequences of metals at Safaga and Qusier were; Ø5> Ø3> Ø4.

It was interesting to observe that the distribution of Fe and Mn were generally lower in Hurghada area (significant in most cases at p≤0.05) comparing to Safaga and Qusier stations (Figure 3). In consistence with our results, previous work showed general elevated levels of Fe and Mn in sites which were used for shipping of ores, especially phosphate and bauxite as reported in Safaga, Hamrawin and Qusier (Mansour et al., 2011; Madkour et al., 2012; El-Metwally, 2015; Dar et al., 2016a; 2016b). Mn and Fe are essential elements and have relatively low toxicology to aquatic organisms. The concentrations of Fe and Mn in all ports were very low compared with the values of LEL (20,000 and 460 µg/g, respectively) and SEL (40,000 and 1100 µg/g, respectively). The values of Fe in the present study were significantly lower than Port Kemblaharbour, Australia (He and Morrison, 2001), while the recorded Mn values were comparable with those reported in Sydney Harbour (Irvine and Birch, 1998) and Victoria Harbour (Wong et al., 1995; Tang et al., 2008) but were much lower than Hamilton Harbour (Poulton et al., 1996). The Fe availability in this study was below that recorded in other harbours around the world (Table 2).

Figure 3 Leachable heavy metals concentrations in fine sediments (Ø3, Ø4 and Ø5) with references to the lowest effect level (LEL) and the sever effect level (SEL) at different stations of the Red Sea ports

Table 2 Comparison between the recorded heavy metals levels (mg/g) in the studied ports with other previous studies worldwide

The significantly high concentrations of Zn, Cu and Pb at Hurghada shipyard were not surprised, since this area serves the activities of ships maintenance and repairing in Hurghada. High amounts of Zn and Cu are continuously dumped to surface sediments from scraped antifouling paints. It is also believed that, considerable amounts of Pb released from accidental oil spill and seeping of fuel during ships maintenance and from mooring boats (Madkour and Dar, 2007). Cu showed significantly (p<0.05) higher levels in the mud sediments (Ø5 fraction). Similar result was observed by El-Said and Youssef (2013) in mangrove sediments of the Red Sea. Among 6 studied metals, they found that Cu showed distinctive high levels in Ø5 relative to the other fractions. Regarding the SQGs, Figure 3 shows the leachable metals rates between LEL and SEL at the different stations. Cu concentrations in all stations exceeded the values of LEL (16 µg/g) and only at the shipyard was exceeded the value of SEL (110 µg/g), meanwhile the recorded concentrations of Zn and Pb in all ports were below LEL (120 and 31 µg/g, respectively) except the shipyard, which were exceeded the guidelines (76.2±5.7 to 330.4±11.5 µg/g for Zn and 50.6±5.8 to 101±4.9 µg/g for Pb). On the other hand, the contamination status of Cu, Zn and Pb was much higher than the Trade Harbours of South Korea (Choi et al., 2012) and lower than those recorded in Port Kemblaharbour, Australia (He and Morrison, 2001), Sydney Harbour (Irvine and Birch, 1998), Kaohsiung Harbour (Chen et al., 2007) and Hamilton Harbour (Poulton et al., 1996) (Table 2).

The spatial distribution of Ni was more homogenous between ports with significant high levels in fishing berth of Hurghada (28.96±3.0 to 61.96±28.0 µg/g) and Qusier old port and fishing basin (38.1±5.0 to 73.3±12.0 µg/g). Salem et al. (2014) stated that the locations recorded high levels of Ni and partially Co related to anthropogenic discharges. The levels of Ni in most studied ports were higher than the LEL (16 µg/g) but lower than SEL (75 µg/g) except Ø5 (91.40 µg/g) fraction that exceeding SEL limit at Hurghada shipyard. The overall concentrations of Ni much higher than the Trade Harbours of South Korea (Choi et al., 2012), within the range recorded in the Sydney Harbour (Irvine and Birch, 1998) and Hamilton Harbour (Poulton et al., 1996) and were lower than Victoria Harbour (Wong et al., 1995; Tang et al., 2008) and Ceuta Harbour (Guerra-Garcia and Garcia-Gomez, 2005) (Table 2).

The concentration of Co recorded significantly very low concentrations (p≤0.01) at Hurghada passenger port and Hurghada shipyard, meanwhile the highest availability were observed in Qusier old port and fishing basin (Figure 3). There were no standard guidelines for Co in the marine sediments, but the overall Co levels in current study were below the standard background of average shale (Förstner et al., 1982) and below the recorded values in other contaminated sites such as in Sydney Harbour (Irvine and Birch, 1998) and Darwin Harbour (Padovan et al., 2012).

Cadmium showed significantly low concentrations (p≤0.05) at Hurghada ports and was below the lowest effect levels (LEL), meanwhile Safaga and Qusier ports recorded Cd concentrations higher than LEL (0.6 µg/g) but still below SEL value (10 µg/g) (Figure 3). Comparing to the levels of Cd with worldwide Harbours (Table 2), Qusier old port and fishing basin recorded levels similar to Hamilton Harbour (Poulton et al., 1996) and Victoria Harbour (Wong et al., 1995; Tang et al., 2008) but it is lower than the levels in Sydney Harbour (Irvine and Birch, 1998).

2.3 Associations and sources of the leachable heavy metals

Correlation matrix and Principal Component Analysis (PCA) estimated the statistical relationship among heavy metals as well as between sediment characteristics and the heavy metals. Additionally, PCA was used to infer the hypothetical sources of heavy metals contamination (Dou et al., 2013; Qiao et al., 2013; Fujita et al., 2014; Yang et al., 2015).

The correlation matrix for the different heavy metals in sediment fractions showed strong association between heavy metals in the mud fraction Ø5, followed by Ø3, and the least association was in Ø4. Two significant associations were observed; the first association was strong positive correlation between metal pairs of; Cu, Zn, Pb and Ni in Ø5 to lesser extents of; Cu, Zn, Pb in Ø3. The second association was common in all fractions, competed Mn with Fe and Cd in strong correlations coincided with a negative correlations of carbonate and with Fe and Mn (Table 3).

As shown in Figure 4, components in Ø3, Ø4 and Ø5 between metals, the obtained results of the PCA showed wide accordance with the correlation matrix. In Ø3 (Figure 4A), two main components with accumulative account for 55.44% of the total variance were found. In the first component (31.98% of the total variance), Fe, Mn and Ni were grouped with positive loading and carbonate content with negative loading. The second component (23.46% of the total variance) grouped positive loading of Cu, Pb and Zn. In Ø4 (Figure 4B), two main components were identified, accounted for 45.32% of the total variance. The first PCA (27.5% of the total variance) was associated with positive loading of Mn, Fe, Cd and Co accompanied with negative loading of carbonate. The second PCA (17.83% of the total variance) showed positive loading between Cu and TOM as well as negative loading of Cu with Cd. In Ø5 (Figure 4C), three components (with total account of 72.49%) were recognized. The first component (32.73% of total variance) included strong positive loadings of Cu, Zn, Pb and Ni. The second component (24.35% of total variance) showed positive loading between Mn and Fe associated with negative loadings toward carbonates. The third PCA component (15.42% of total variance) showed positive loading of Cd with Co and negative loading of Cd and Co toward TOM.

Figure 4 Heavy metals associations in the fine fractions Ø3 (A), Ø4 (B) and Ø5 (C) according the PCA between metals

The overall multivariate analyses showed two major patterns. The first pattern suggested that the metals Fe, Mn and partially Cd were originated from the trrigenous sources and were negatively correlated with carbonate, this mainly due to phosphate ores sedimentation and coastal activities. Previous work in many locations of Red Sea area showed high levels of these metals (Fe, Mn and Cd) associated with terrestrial inputs (e.g., Mansour et al., 2011; Madkour et al., 2012; El-Metwally, 2015; Dar et al., 2016a; 2016b; El-Metwally et al., 2017). The second pattern showed that high portion of Cu, Zn and Pb that mostly have anthropogenic sources since the highest impacts were observed at Hurghada shipyard.

2.4 Assessment the ecological risk

Metal pollution load index (MPI) is a simple method to describe the integrated effect of metal contamination. The values (>1) indicate to the progressive deterioration in sediments quality (El-Said and Youssef, 2013). MPI was obtained from the following formula:

Where, the contamination factor (CF) is the concentration of metal in obtained sample (Cmetal) divided by the background concentration (Cbackground) of the same metal and (n) is the number of measured metals. The calculated values of MPI were ranged between 1.08 and 1.50 (Table 4). The highest MPI values were found in Hurghada stations (1.11 to 1.50) followed by Qusier (Table 4) and the lowest MPI values (1.08 to 1.22) were at Safaga stations. Similar pattern for MPI was recorded by Salem et al. (2014) at Qusier and Safaga.

The enrichment factor (EF) represents the actual contamination level in sediments since it is probably differentiates between natural and anthropogenic sources of metals (Chen et al., 2007; Amin et al., 2009). EF was calculated from the equation:

The calculated averages of EF showed that the heavy metals were followed the enrichment order; Pb>>Cu≥Zn>Cd>Mn=Ni>Co. Zhang and Liu (2002) reported that the lowest values (EF<1.5) indicating to natural sources of heavy metals (crustal materials) and the highest values (EF>1.5) indicating to the significant anthropogenic sources. In general, the calculated EF values illustrated moderate enrichment for Cu (2.45), Zn (2.37), Ni (2.03), Cd (2.23) and Mn (2.04), meanwhile Pb was highly enriched (6.89). With respect to the studied stations, Hurghada shipyard and tourist marina showed high EF enrichment by Cu (6.43 to 8.76), Zn (3.99 to 8.22), and Pb (10.03 to 25.15) attributed to anthropogenic sources from ships repairing, antifouling paints and fuels leakage as well as boats mooring. The studied stations at Safaga and Qusier were enriched by Mn (1.99 to 4.06) and partially Cd (1.55 to 5.2) due to the different shipment operations (Table 5).

Geo-accumulation index (Igeo) has been proposed by Müller (1969) to evaluate the contamination level in sediments by comparing current status with the pre-industrial levels according to the formula:

Where Cn is the current concentration of metal, Bn is the geochemical background value of the same metal, and the factor 1.5 is the matrix correction factor of the background. According to Müller (1981), Igeo is estimated over seven categories; uncontaminated sediments (Igeo≤0), uncontaminated to moderately contaminated (0< Igeo≤1), moderately contaminated (1< Igeo≤2), moderately to strongly contaminated (2< Igeo≤3), strongly contaminated (3< Igeo≤4), strongly to extremely contaminated (4< Igeo≤5) and extremely contaminated (Igeo≥5).

As calculated in Table 4, the Igeo values of the studied heavy metals at the different stations were classified the marine sediments as unpolluted to moderate polluted; except at Hurghada shipyard, the marine sediments were classified as moderately to highly polluted by Cu (2.56), Zn (2.47) and Pb (4.08).

3 Conclusions

Distribution and ecological risk of heavy metals were investigated in finest fractions of the surface sediments of Red Sea ports at Hurghada, Safaga and Qusier Cities. The total of the finest fractions (Ø3, Ø4 and Ø5) was varied between 36.26% and 83.47% with considerable high percentages of the different stations indicating to different sources of depositions mostly from the maritime activities, terrestrial runoff, phosphate shipments and the nearby coastal based activities. Carbonate percentage showed significant decline with increasing the terrigenous inputs at Safaga followed by Qusier, however, Hurghada stations showed high carbonate percentages due to the high marine productivity. TOM recorded variable percentages at the different stations may attribute to the local effects of the anthropogenic effluents. At Hurghada, the finest fraction Ø5 was the essential heavy metal carrier followed by Ø4 with reference to Hurghada shipyard that recorded significantly high Fe, Mn, Zn, Cu, Ni and Pb in the finest fraction Ø5. At Safaga, Fe showed relatively high values at the different wharfs relative to Hurghada and Qusier due to the high amount of terrestrial runoff. At Qusier, the highest Fe and Zn was showed at the fishing basin in Ø5 followed by Ø3. The distribution of Fe and Mn were generally lower in Hurghada stations (p≤0.05) comparing to Safaga and Qusier stations with distinctive high levels of Cu (p<0.05) in Ø5. A strong correlation observed between Fe, Mn and partially Cd, it was associated with the process of shipping of raw materials from Safaga and Qusier ports. The organic matter content showed no significant correlation with heavy metals in the surface sediments, and carbonate was negatively correlated with Cu, Zn and Pb. The levels of heavy metals in present study were similar/or below the levels recorded in other ports worldwide. According to sediments quality guidelines (SQGs), the concentrations of heavy metals in sediments of the studied ports were not expected to have biological adverse effects, except the metals Cu, Zn, Pb and Ni may pose some ecological risks to marine organisms near the shipyard of Hurghada.

Authors’ contributions

Mohamed E.A. El-Metwally contributed to the paper by collecting samples, analyses, processing the data and writing the manuscript. Amany G. Madkour and Rasha R. Fouad contributed to the paper by collecting samples, laboratory treatment and data analysis. Lamiaa I. Mohamedein contributed to the paper by collecting samples, analysis and coordination. Hamada A. Nour Eldine contributed by collecting samples. Mahmoud A. Dar and Khalid M. El-Moselhy contributed by editing and revising the manuscript.

Acknowledgments

The authors are thankful for the authorities of Egyptian Red Sea ports for supporting through the samples collection. This work was funded by the projects system of National Institute of Oceanography and Fisheries, Egypt.

References

Abu-Hilal A.H., and Badran M.I., 1990, Effect of pollution sources on metal concentration in sediment cores from the Gulf of Aqaba (Red Sea). Mar. Pollut. Bull., 21: 190-197

https://doi.org/10.1016/0025-326X(90)90501-X

Amin B., Ismail A., Arshad A., Yap C.K., and Kamarudin M.S., 2009, Anthropogenic impacts on heavy metal concentrations in the coastal sediments of Dumai, Indonesia. Environ. Monit. Assess., 148: 291-305

https://doi.org/10.1007/s10661-008-0159-z

PMid:18274874

Chen C.W., Kao C., Chen C., and Dong C., 2007, Distribution and accumulation of heavy metals in the sediments of Kaohsiung Harbour, Taiwan. Chemosphere, 66: 1431-1440

https://doi.org/10.1016/j.chemosphere.2006.09.030

PMid:17113128

Chester R.; Lin F. G., and Basaham A., 1994, Heavy metals solid state speciation changes associated with the down-column fluxes of oceanic particulates. J. Geol. Soc. London, 151: 351–360

https://doi.org/10.1144/gsjgs.151.2.0351

Choi K.Y., Kim S.H., Hong G.H., and Chon H.T., 2012, Distributions of heavy metals in the sediments of South Korean harbors. Environ. Geochem. Health, 34: 71-82

https://doi.org/10.1007/s10653-011-9413-3

PMid:21826508

Dar M.A., 2014, Distribution patterns of some heavy metals in the surface sediment fractions at northern Safaga Bay, Red Sea, Egypt. Arab. J. Geosci., 7(1): 55–67

https://doi.org/10.1007/s12517-012-0754-8

Dar M.A., El-Metwally M.E.A., and El-Moselhy Kh.M., 2016a, Distribution patterns of mobil heavy metals in the inshore sediments of the Red Sea. Arab. J. Geosci., 9: 221

https://doi.org/10.1007/s12517-015-2205-9

Dar M.A., Fouda F.A., El-Nagar A.M., and Nasr H.M., 2016b, The effect of land-based activities on the near-shore environment of the Red Sea, Egypt. Environ. Earth. Sci., 75: 188

https://doi.org/10.1007/s12665-015-4961-y

Dean Jr.W.E., 1974, Determination of carbonate and organic matter in calcareous sediments and sedimentary rocks by loss in ignition: comparison with other methods. J. Sediment. Petrol., 44: 242–248

Dickinson W.W., Dunbar G.B., and McLeod H., 1996, Heavy metal history from cores in Wellington Harbour, New Zealand. Environ. Geol., 27: 59–69

https://doi.org/10.1007/BF00770603

Dou Y., Li J., Zhao J., Hu B., and Yang S., 2013, Distribution, Enrichment and Source of Heavy Metals in Surface Sediments of the Eastern Beibu Bay, South China Sea. Mar. Poll. Bull., 67: 137-145

https://doi.org/10.1016/j.marpolbul.2012.11.022

PMid:23245460

El-Metwally M.E.A., 2015, Monitoring of heavy metals pollution in the Egyptian Red Sea coast and response of marine organisms. Ph.D. Thesis, Mansoura University, 275

El-Metwally M.E.A., Abouhend A.S., Dar M.A., and El-Moselhy Kh.M., 2017, Effects of urbanization on the heavy metal concentrations in the Red Sea coastal sediments, Egypt. Internat. J. Mar. Sci., 7(13): 114-124

https://doi.org/10.5376/ijms.2017.07.0013

El-Said G.F., and Youssef D.H., 2013, Ecotoxicological impact of some heavy metals and their distribution in some fractions of mangrove sediments from Red Sea, Egypt. Environ. Monit. Assess., 185: 393-404

https://doi.org/10.1007/s10661-012-2561-9

PMid:22371036

El Zrelli R., Courjault-Radé P., Rabaoui L., Castet S., Michel S., and Bejaoui N., 2015, Heavy metal contamination and ecological risk assessment in the surface sediments of the coastal area surrounding the industrial complex of Gabes city Gulf of Gabes, SE Tunisia. Mar. Poll. Bull., 101: 922–929

https://doi.org/10.1016/j.marpolbul.2015.10.047

PMid:26526855

Folk R.L., 1974, Petrology of sedimentary rocks. University of Texas, Hemphill Pub., Co., 182

Förstner U., and Salomons W., 1980, Trace metal analysis on polluted sediments. Part 1. Assessment of sources and intensities. Environ. Tech. Lett., 1: 494-505

https://doi.org/10.1080/09593338009384006

Förstner U., and Wittmann G.T.W., 1983, Metal pollution in the aquatic environment. Second Revised Edition. Springer-Verlag, Berlin

PMCid:PMC1154062

Förstner U., Calmano W., and Schoer J., 1982, Metals in sediments from the Elbe, Weser and Ems estuaries and from the German Bight: grain size effects and chemical forms. Thalassia Jugoslavia, 12: 30-36

Fujita M., Ide Y., Sato D., Kench P.S., Kuwahara Y., Yokoki H., and Kayanne H., 2014, Heavy metal contamination of coastal lagoon sediments: Fongafale Islet, Funafuti Atoll, Tuvalu. Chemosphere, 95: 628–634

https://doi.org/10.1016/j.chemosphere.2013.10.023

PMid:24200049

Galkus A., Joksas K., Stakeniene R., and Lagunaviciene L., 2012, Heavy metal contamination of harbour bottom sediments. Pol. J. Environ. Stud., 21(6): 1583-1594

Gargouri D., Azri C., Serbaji M.M., Jedoui Y., and Montacer M., 2011, Heavy metal concentrations in the surface marine sediments of Sfax coast, Tunisia. Environ. Monit. Assess., 75: 519–530

https://doi.org/10.1007/s10661-010-1548-7

PMid:20533086

Gross M.G., 1971, Carbon determination. In: Carver, R.E. (Ed.), Procedures in Sedimentary Petrology. John Wiley and Sons, New York, pp. 573–596

Guerra-Garcia J.M., and Garcia-Gomez J.C., 2005, Assessing pollution levels in sediments of a harbour with two opposing entrances: environmental implications. J. Environ. Manage., 77: 1-11

https://doi.org/10.1016/j.jenvman.2005.01.023

PMid:15946788

Hanna R.G.M., 1992, The levels of heavy metals in the Red Sea after 50 years, Sci. Total Environ., 125: 417-488

https://doi.org/10.1016/0048-9697(92)90405-H

Hanna R.G., and Muir G.L., 1990, Red Sea corals as biomonitors of trace metal pollution. Environ. Monit. Assess., 14: 211-222

https://doi.org/10.1007/BF00677917

PMid:24243324

He Z., and Morrison R.J., 2001, Changes in the marine environment of Port Kembla harbour, NSW, Australia, 1975–1995: a review. Mar. Poll. Bull., 42: 193–201

https://doi.org/10.1016/S0025-326X(00)00142-9

Idris A.M., Eltayeb M.A.H., Potgieter-Vermaak S.S., Van Grieken R., and Potgieter J.H., 2007, Assessment of heavy metals pollution in Sudanese harbours along the Red Sea coast. Microchem. J., 87: 104–112

https://doi.org/10.1016/j.microc.2007.06.004

Irvine I., and Birch G.F., 1998, Distribution of heavy metals in surficial sediments of Port Jackson, Sydney, New South Wales. Australian J. Earth Sci., 45: 297-304

https://doi.org/10.1080/08120099808728388

Madkour H.A., 2004, Geochemical and environmental studies of recent marine sediments and some invertebrates of the Red Sea, Egypt. Ph. D. thesis, South Valley University, Qena, p. 317

Madkour H.A., 2005, Geochemical and environmental studies of recent marine sediments and some hard corals of Wadi El-Gemal area of the Red Sea, Egypt. Egypt. J. Aqua. Res., 31 (1): 69–91

Madkour H.A., and Dar M.A., 2007, The anthropogenic effluents of the human activities on the Red Sea coast at Hurghada harbour (case study). Egypt. J. Aqua. Res., 33 (1): 43–58

Madkour H.A., El-Taher A., Ahmed N.A., Mohamed A.W., and El-Erin T.M., 2012, Contamination of coastal sediments in El-Hamrawein Harbour, Red Sea, Egypt. J. Environ. Sci. Technol., 5(4): 210–221

https://doi.org/10.3923/jest.2012.210.221

Mansour A. M., Nawar A.H., and Madkour H.A., 2011, Metal pollution in marine sediments of selected harbours and industrial areas along the Red Sea coast of Egypt. Ann. Naturhist. Mus. Wien. Ser., 113(A): 225–244

Mansour A.M., Askalany M.S., Madkour H.A., and Assran B.B., 2013, Assessment and comparison of heavy-metal concentrations in marine sediments in view of tourism activities in Hurghada area, northern Red Sea, Egypt. Egypt. J. Aqua. Res., 39: 91–103

https://doi.org/10.1016/j.ejar.2013.07.004

Maata M., and Singh S., 2008, Heavy metal pollution in Suva Harbour sediments, Fiji. Environ. Chem. Let., 6(2): 113–118

https://doi.org/10.1007/s10311-007-0122-1

McClanhan T.R., Sheppard C.R.C., and Obura D.O., 2000, Coral reefs of the Indian Ocean, Their Ecology and Conservation, p. 247. Oxford University Press, New York

Müller G., 1969, Index of geoaccumulation in the sediments of the Rhine River. Geol. J., 2: 108–118

Müller G., 1979, Heavy metals in the sediment of the Rhine–Changes seitt. 1971. Umschan 79: 778–783

Müller G., 1981, The heavy metal pollution of the sediments of Neckars and its tributary: a stocktaking. Chem. Zeitung., 105: 157–164

Paetzel M., Nes G., Leifsen L.O., and Schrader H., 2003, Sediment pollution in the Vagen, Bergen harbour, Norway. Environ. Geol., 43: 476–483

Persuad D., Jaagumagi R., and Hayton A., 1992, Guidelines for the protection and management of aquatic sediment quality in Ontario, Queen's Printer for Ontario, pp.23

Padovan A., Munksgaard N., Alvarez A., McGuinness C., Parry D., and Gibb K., 2012, Trace metal concentrations in the tropical sponge Spheciospongia vagabunda at a sewage outfall: synchrotron X-ray imaging reveals the micron-scale distribution of accumulated metals. Hydrobiol., 687: 275–288

https://doi.org/10.1007/s10750-011-0916-9

Poulton D.J., Morris W.A., and Coakley J.P., 1996, Zonation of contaminated bottom sediments in Hamilton Harbour as defined by statistical classification techniques. Wat. Qual. Res. J. Canada, 31: 505–528

Qiao Y., Yang Y., Gu J., and Zhao, J., 2013, Distribution and Geochemical Speciation of Heavy Metals in Sediments from Coastal Area Suffered Rapid Urbanization, a Case Study of Shantou Bay, China. Mar. Poll. Bull., 68: 140-146

https://doi.org/10.1016/j.marpolbul.2012.12.003

PMid:23290610

Rubio B., Nombela M.A., and Vilas F., 2000, Geochemistry of major trace elements in sediments of the Ria de vigo (NW Spain) an assessment of metal pollution. Mar. Poll. Bull., 40: 968–980

https://doi.org/10.1016/S0025-326X(00)00039-4

Salem D.M.S., Khalid A., El-Nemr A., and El-Sikaily A., 2014, Comperhensive risk assessment of heavy metals in the surface sediments along the Egyptian Red Sea coast. Egypt. J. Aquat. Res., 40 (4): 349-362

https://doi.org/10.1016/j.ejar.2014.11.004

Salomons W., and Förstner U., 1984, Metals in the hydrocycle. Springer-Verlag, Berlin.349P.

https://doi.org/10.1007/978-3-642-69325-0

Tang C.W.Y., Ip C.C.M., Zhang G., Shin P.K.S., Qian P.Y., and Li X.D., 2008, The spatial and temporal distribution of heavy metals in sediments of Victoria Harbour, Hong Kong. Mar. Poll. Bull., 57(6–12): 816–825

Tomlinson D.C., Wilson J.G., Harris C.R. and Jeffrey D.W., 1980, Problems in the assessment of heavy metals in estuaries and the formation pollution index. Helgoland Mar. Res., 33: 566-575

https://doi.org/10.1007/bf02414780

Wong Y.S., Tam N.F.Y., Lau P.S., and Xue, X.Z., 1995, The toxicity of marine sediments in Victoria Harbour, Hong Kong. Mar. Poll. Bull., 31: 464–470

https://doi.org/10.1016/0025-326X(96)81927-8

Yang L., Wang L., Wang Y., and Zhang W., 2015, Geochemical speciation and pollution assessment of heavy metals in surface sediments from Nansi Lake, China. Environ. Monit. Assess., 187: 1–9

https://doi.org/10.1007/s10661-015-4480-z

PMid:25893757

Yu T., Zhang Y., and Zhang Y., 2012, Distribution and bioavailability of heavy metals in different particle-size fractions of sediments in Taihu Lake, China. Chem. Speciat. Bioavail., 24(4): 205-215

https://doi.org/10.3184/095422912X13488240379124

Zhang J., and Liu C.L., 2002, Riverine composition and estuarine geochemistry of particulate metals in China-weathering feature, anthropogenic impact and chemical fluxes. Estuar. Coast. Shelf Sci., 45: 1051-1070

https://doi.org/10.1006/ecss.2001.0879

Zhu H., Yuan X., Zeng G., Jiang M., Liang J., Zhang C., Yin J., Huang H., Liu Z., and Jiang H., 2012, Ecological risk assessment of heavy metals in sediments of Xiawan Port based on modified potential ecological risk index. Trans. Nonferrous Metals Soc. China, 22: 1470–1477

https://doi.org/10.1016/S1003-6326(11)61343-5