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  • Geochemistry of Coastal Marine Sediments Geochemistry of Coastal Marine Sediments and their Contaminant Metals, Red Sea, Egypt: and their Contaminant Metals, Red Sea, Egypt:

    A Legacy for the Future and a Tracer to A Legacy for the Future and a Tracer to Modern Sediment DynamicsModern Sediment Dynamics

    bybyABBAS M. MANSOUR, AHMED H. NAWAR1, AND AHMED W. MOHAMED1ABBAS M. MANSOUR, AHMED H. NAWAR1, AND AHMED W. MOHAMED1

    Geology Dept. Geology Dept. FacFac. Science, South Valley Univ., 83511 . Science, South Valley Univ., 83511 QenaQena, Egypt, Egypt11National Inst. Oceanography and Fisheries, Red Sea Branch, National Inst. Oceanography and Fisheries, Red Sea Branch, HurghadaHurghada, Egypt, Egypt

  • Are the Are the nearshorenearshore marine ecosystem marine ecosystem and and geosystemgeosystem impacted?impacted?

    Along the Red Sea coast of Egypt, the nearshoremarine ecosystem and geosystem are dynamic having variable bottom sediment types, diverse biologic habitats, and localized depositional and transportation processes. They are impacted by many activities, as phosphate mining, oil industry, fishing, recreation, housing, sewage and waste disposal, and shipping. In some cases, especially adjacent to large cities and harbors, the sediments are polluted and the ecosystem suffers detrimental effects.

  • Are the pollutants reach levels cause Are the pollutants reach levels cause toxic effects to marine organisms ?toxic effects to marine organisms ?

    Through discharge of pollutants from coastal communities and other sources, metals and organic pollutants may reach levels that cause toxic effects to marineorganisms like fish and shrimp. The sediments can also release toxic constituents to the water column.

  • Where is the study area?

    The study area extends from Gemsha at the entrance of the Gulf of Suez southward to Ras Banas (Fig. 1). Water depths range from 0m to ab. 60m and to a distance of more than 4000m in the sea (Fig. 2). The land is a relatively high, steep metamorphic and igneous terrain in the west and a lower sedimentary sequence close to the sea.

  • What are the sources of the coastal Red Sea Sediments?

    The coastal Red Sea sediments are the result of interplay of aeolian, fluvial and marine influx of sedimentary material. The influence of these sources is more or less localized resulting in a particular textural and compositional distribution, especially in the nearshore area.

  • Sedimentary Parameters

    Grain Size Distribution

  • What are the reasons for the high mud content in some areas?

    The reason for this high mud content is due to the landfill in transects 10 and 3, and terrigenous flux of wadis in transects 2 and 5. Moreover, phosphate deposits in the nearby harbors also contribute in the high mud content of transects 2 and 3.

  • How the sediment are distributed along the coast

    From the beach to ab. 200m seaward fine sands and mud dominant most transects, whereas medium to coarse sands occur in the beach and close to topographic highareas. In some transects seaward fine sands and mud dominant the low areas. This distribution of coarser sediment may reflect the abundance of terrigenous sediments in the beach and biogenic fragments in reefareas.

  • How to prove this distribution of sediment types along the coast?

    The distribution of carbonates supports this result where carbonate content is low in nearly the first 200m from the beach and gradually or abruptly increases seaward (Fig. 2). The areas of finer size in nearly the first 200m from the beach may represent the winnowed material transported in the nearshore zone away from the beach coarser material.

  • How to prove this distribution of sediment types along the coast?

    . In front of marine station at Hurghada(transect 9) fine and medium sands dominate, especially in the 800m landward where non-carbonates are common. Concentrations of some metals such as Fe, Mn, Ni, Zn, Pb, V, Cu are relatively high indicating the terrigenous contamination.

  • What are the most prominent pollution features in Hurghada?

    Landfilling is one of the most prominent pollution features in Hurghada. Bottom sediments act as a reservoir for different nutrient salts, trace metals and even rare earth elements. Sediments are resuspendedand carried by currents southward to these areas, where they are deposited and protected by the islands from storm waves causing subsequent resuspension.

  • Geochemical Parameters

    Organic Carbon (OC) and Total Organic Matter (TOM)

  • What are the areas rich in organic matter and why?

    The abundance of OC and TOM in Quseir is partially from the terrigenous flux of W. Ambaji and probably due to sewage of Quseir City and the harbor. Sewage of Safaga City and harbors are the reason for the high content of OC and TOM in transect 3. Terrestrial materials rich in organic matter and the high organic productivity are the two main reasons for their high content in Sharm Abu Makhadeg. The deeper parts of transects 10, 11, 12 are rich in fine carbonate sediments (Fig. 2) and therefore most organic matter are associated to carbonates.

  • Geochemical Parameters

    Distribution of Major Elements

  • Where do distribute the major elements and why?

    Ca, except for transects 3 and 12, and Mg and Sr contents generally increase seaward. Biogenic constituents are the reason for increasing these elements seaward whereas terrigenous materials disturb this trend in transects 3 and 12. These elements Ca, Mg and Sr show +ve correlation to carbonates. However, this correlation is low due to their difference from one area to another indicating that part of these elements is detritus.

  • Where do distribute the major elements and why?

    Na, Fe and K reveal -ve correlation to carbonates. Their conc. generally decreases seaward reflecting their detrital origin. Their low conc. is observed in carbonate-dominated areas. The highest -ve correlation (r=-0.62) is recorded between Fe and carbonates. In some transects low -ve (transects 2 and 3) and low +ve (transect 10) correlation is observed between Fe and carbonates.

  • Is the elements distribution reflecting the source sediments only and why?

    The -ve correlations between the biogenic and terrigenous elements reflect the presence of 2 different sediments sources namely marine and terrestrial. Low correlation is mostly observed between elements and carbonates and mean size showing the presence of appreciable amount of carbonates in fine fraction as well as in coarse fractions. The presence of relatively high Sr concentrations is indicative of important proportions of aragonite. This is in good agreement with the biogenic origin of most carbonate deposits, especially in the seaward side.

  • Geochemical Parameters

    Distribution of Trace Metals

  • Are metals reflecting the anthropogenic influence? How and where?

    Most of the lowest conc. are from transects 6, 11 and 13, whereas transects 2, 3, and 7 reveal most of the highest concentrations. This may be related to the terrigenous input and anthropogenic influence where transects 2,3 and 7 lie at or near the harbors. In transect 2 (Quseir), P content is very high compared with other areas. P is positively correlated to carbonates (r= 0.53) and mud (r= 0.42) indicating that part of P is related to dust of P from the nearby harbor.

  • Are metals reflect the anthropogenic influence? How and where?

    Contaminants (Cd, Co, Ni, Zn, Pb, Cu) show very low correlation either +ve or -ve to carbonates related to source rocks and/or sewage of QuseirCity. The +ve correlation of Pb to mud (r= 0.54) indicates their transportation to sediments from the nearby harbor. Some transects show the highest conc. of one element such as Co of transect 1, Mnin transect 5 and Cu in transect 13. This may be due to the terrigenous source rocks, especially where the highest concentrations are in the beach samples and less seaward.

  • Table 2. Chemical and physical properties of sediment samples from different areas (transects T1-T13).T13 T12 T11 T10 T9 T8 T7 T6 T5 T4 T3 T2 T1 BGL Max Min

    Ca % 16.02 30.31 40.57 31.60 34.02 29.90 35.23 23.54 49.01 17.21 22.06 12.96 18.87 27.57 49.01 12.96Na % 1.13 1.48 0.86 0.62 0.47 0.59 0.58 0.53 1.62 1.63 1.62 1.37 1.08 0.57 1.63 0.47Mg % 1.86 5.31 3.11 1.87 1.77 1.77 1.73 1.67 4.88 5.35 5.53 3.77 4.31 1.77 5.53 1.67K % 0.16 0.22 0.14 0.37 0.21 0.12 0.11 0.41 0.37 0.40 0.20 0.19 0.65 0.39 0.65 0.11Sr % 0.89 0.23 0.22 0.18 0.21 0.18 0.26 0.19 0.24 0.29 0.26 0.24 1.03 0.18 1.03 0.18Fe % 1.00 1.32 0.94 1.07 0.81 0.89 0.60 0.27 1.45 0.67 1.21 1.04 1.02 0.67 1.45 0.27Mn ppm 404.91 413.38 301.86 283.07 292.00 308.17 428.57 127.13 609.54 293.25 576.00 483.27 469.44 205.10 609.54 127.13P ppm 128.64 144.38 80.43 129.60 121.92 92.83 109.20 103.75 142.46 112.38 129.00 287.45 136.38 116.68 287.45 80.43Cd ppm 0.10 1.21 1.46 1.05 1.39 1.27 1.71 0.86 0.93 0.94 1.55 1.13 0.36 0.96 1.71 0.10Co ppm 4.71 4.94 13.27 10.78 11.32 11.22 17.66 8.51 6.78 8.54 10.33 17.23 18.88 9.64 18.88 4.71Ni ppm 4.56 30.27 42.00 27.91 17.15 15.92 57.84 19.04 34.13 22.93 32.90 36.96 5.84 23.48 57.84 4.56Zn ppm 27.22 31.61 23.86 21.60 25.14 25.05 31.86 13.58 63.48 31.65 73.52 73.03 23.03 17.59 73.52 13.58Pb ppm 32.88 52.46 30.14 25.20 29.61 28.73 35.63 14.42 39.62 50.00 71.00 32.60 34.23 19.81 71.00 14.42V ppm 21.00 67.44 45.57 35.93 44.72 39.27 54.96 7.65 42.00 45.50 38.70 93.70 42.15 21.79 93.70 7.65Cu ppm 57.79 24.46 11.71 13.53 28.08 15.92 15.14 14.50 40.13 37.40 31.30 27.81 14.40 14.02 57.79 11.71Carbonates % 59.06 62.29 70.29 70.73 71.68 62.90 77.96 84.40 49.96 74.65 78.02 39.98 76.52 77.56 84.40 39.98TOM % 2.06 3.65 4.80 4.25 2.91 2.73 2.63 3.53 4.30 2.56 4.89 3.99 2.12 3.89 4.89 2.06OC % 1.14 2.02 2.65 2.37 1.59 1.52 1.46 1.99 2.36 1.46 2.71 2.22 1.18 2.18 2.71 1.14Mz (phi) 1.86 2.02 2.11 2.87 2.09 1.78 1.16 1.12 3.05 1.63 2.65 3.59 2.15 2.00 3.59 1.12Gravel % 3.69 3.11 2.75 3.04 4.85 5.13 7.42 10.79 1.62 3.36 6.16 0.07 2.00 6.91 10.79 0.07Sand % 85.85 88.25 85.81 67.85 83.53 88.35 91.31 84.58 74.49 90.12 68.27 70.30 84.21 76.22 91.31 67.85Mud % 10.46 8.64 11.48 28.85 11.62 6.51 1.27 4.61 23.73 6.50 25.58 29.63 13.82 16.73 29.63 1.27BGL = average of T6 & T11 (two transects include lowest concentrations of metals), Mz = mean sizeMax = maximum (marked cells), Min = minimum, TOM = total organic matter, OC = organic carbon

  • What are the reasons for the apparent enrichments of Pb & Cd?

    The high Cd conc. near harbors in transects 3 and 7 is probably due to industrial waste waters. Amounts of Cd accumulate in the deposits through contaminated materials such as use of coal, oil and cement. The apparent enrichments of Pb, Cd in carbonate sediments of most transects are due to: 1) The preferential uptake in the carbonatesediments. The affinity of Cd for organic matter is well documented, as is the organic matter association of recent carbonate sediments.

  • What are the reasons for the apparent enrichments of Pb & Cd?

    The uptake of Pb and Cd from surface seawater by marine organisms has been suggested, although Pb is generally thought to be associated with inorganic particulates. 2) Proximity to localized anthropogenic sources as in transects 2, 3, and 7. These observations readily explain the large Pb anomalies in the carbonate sediments and may also explain the elevated Cd level.

  • Statistical Analysis

    Cluster analysis

  • What are the cluster types of metals and why?

    The lowest contaminant cluster (75 samples),

    Cu cluster (2 samples), Cd, Co, Zn, V cluster (4 samples), Ni cluster (29 samples) and Pb cluster (32 samples)(Fig. 3B).

  • What do characterize the 1st cluster & why?

    The first cluster includes most samples in transects 1, 6, 9, 10, 11, and 13 (Fig. 5). It shows the lowest conc. of metals (Cd, Ni, Zn, Pb, V, and Cu) and can be used as background level of metals.

  • What do characterize the 2nd cluster & why?

    The Cu cluster (av. 235ppm) includes the first 2 samples of transect 13 indicating that most of Cu is transported to sediments from the nearby Basement Rocks. Decreasing conc. of Cu from beach seaward support this result.

  • What do characterize the 3rd cluster & why?

    Cluster 3 includes the beach sample of transect 1, and 3 samples in transect 2. The highest conc. of Cd, Co, Zn, and V characterizes this cluster. Concentration of these metals exceeds 6 times the background level of V, 5 times that of Zn, 3 times that of Cd and 2 times that of Co and Ni (Fig. 3B). This high conc. is related to the nearby source rocks of transect 1, whereas in transect 2 the phosphate harbor is probably the reason of this conc.. The occurrences of samples on the continental slope away from the beach in transect 2 support this result.

  • Rock phosphates and environmental assessments

    Rock phosphates contain large amounts of Cd, Zn, Co, Ni, Pb and Cu and should be considered in metal transport assessments, ecosystem studies and environmental assessments (Kpomblekou and Tabatabai, 1994).

  • Explain the highest conc. of Ni in some transects

    Cluster 4 is characterized by its highest conc. of Ni (43.6ppm). Cd and Co conc. are also high. The highest conc. of Ni in transects 11, 12 is probably related to source rocks from the opposite wadis. In transects 2, 7 the high Ni conc. is probably related to the nearby harbor. Contamination from the sea can cause this high content of Ni in the seaward side of transect 10. NE-SW oriented wave motion and southward currents transport contaminants from the Gulf of Suez to the exposed area of transect 10.

  • Which areas include the highest conc. of Pb and why?

    Pb cluster includes all samples of transect 3, most samples of transect 4, 5 and 12. Transects 3, 4, and 5 occur in semi-enclosed areas probably sensitive to the anthropogenic activities. The shore of the area at transect 3 is occupied by Safaga city, port and harbors for aluminum, phosphate and others with many hotels and tourist villages widely distributed around transects 4 and 5. In transect 12, Pb conc. in the seaward side is probably related to the contamination from sea.

  • What are the reasons for the increasing rate of Pb?

    Oil from production and heavy oil tankers in the Gulf of Suez and the NE-SW wave motion and southward currents are probably the reason for the increasing rate of Pb. Motor boats are the largest source of Pb enrichments in sediments. It originates from the combustion and aeoliandistribution of the tetraethyl lead added to automobile gasoline since 1945 (Chow a.o., 1973). Concentration of Pb in the deeper parts of transect 12 is associated with fine sediments indicating its aeolian distribution, although the concentrations of transects 3 and 4 indicate point sources probably related to the harbor in transect 3 and the motor boats of tourists in transect 4.

  • Conclusions and Recommendations

    Both mineral and chemical analyses reveal the presence of an inverse relationship between carbonate and terrigenous mineral associations. This illustrates the two environments affecting the dominant sediment types. Terrestrial environment acts for the dominance of terrigenous material mostly in the beach and nearshore sediments. Marine environment is responsible for the predominance of carbonates in the other bottom sediments.

  • Conclusions and Recommendations

    Concentrations of metals (ex. Pb, P, Cd, Ni, Cu and Zn) and physical properties (grain size, OC, and TOM) measured in surface samples taken in 1996 are a legacy for the future and will help managers identify anthropogenic impacts and better assess the needs for remediation by detecting any changes, from the existing level expected with operation of future activity.

  • Conclusions and Recommendations

    The quality of coastal sediments in some areas is impacted by proximity to harbors, urban areas and industrial activities, especially Quseir, Safaga and Hurghada. Semi-enclosed marine areas, such as northern and southern Safaga Bay, are particularly sensitive to anthropogenic inputs because their sediments and water may be less efficiently removed, dispersed, and diluted. In Hurghadaalthough sediment fill is widely distributed, sediment contamination is low due to the dispersion of sediments by water waves and currents.

  • Conclusions and Recommendations

    Contaminants are localized in coastal sediments and therefore, remediation is an easy work by covering the contaminated areas with a thin layer of cleaner sediment. Unfortunately, the accumulations of industrial and urban waste still continue to be reworked by biologic and geologic processes and thus remain accessible to biota well into the future.

  • Conclusions and Recommendations

    The highest concentrations in sediments are close to the harbors and near urban areas, with decreasing values seaward. The concentrations of P, Cd, Ni and Pb (the more characteristic contaminants) measured at some areas are above the background values and can cause adverse effects to marine organisms. Therefore, chemical and biologic measurements should be made to determine whether metal concentrations sufficiently high to cause toxic effects in test organisms. Toxicity criteria are determined by exposing biota to varying levels of contaminants in sediments and comparing responses.

  • Conclusions and Recommendations

    Sediments are generally muddy in the deeper areas between the beach on the western side and the islands in the eastern side, with a transition to coarser textures in the beach and toward the islands; elevated contaminant concentrations follow the pattern of being present in muddier sediments. Many contaminants are associated with fine-grained material and/or are characteristic of specific sources. Changes in contaminant patterns can consequently trace transport and cycling processes and help measure rates of modern geologic and geochemical processes in the marine environment.

  • Conclusions and Recommendations

    Pollution from port facilities in Hurghada, Safaga and Quseir threatens the nearby coral reefs. Sedimentation from coastal development off Hurghada and Safaga has seriously damaged reefs. Eutrophicationproblems related to nutrient rich sewage water from hotel gardens, as well as desalinization effluents pumped onto reefs from hotels in Quseir threaten reef health.

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