Comprehensive risk assessment and interactions of fluoride and boron ions in the water-sediments interface: The Red Sea, Egypt.

This study presents a baseline evaluation of the distribution, human and ecotoxicological risk, and the potential interactions of fluoride and boron in the water-sediment interface in 25 locations from incredible Red Sea tourist destinations. Results showed comparable levels of B and F in the water and sediments with previous literature. Significant positive correlation was found between B and F (r = 0.57; P<0.01). Based on the sediment/liquid partition coefficient (Kd), F is more likely to be released from the sediment into seawater (logKd< 3) than B (3< logKd< 4). pH and alkalinity may affect water-sediment interactions of B and F, respectively, while SO42- and Cl- ions had no significant effect on adsorption ability of F and B. The majority of minerals had average saturation Index (SI) > 1 referring to the over saturation of seawater with these minerals and their inability to dissolve. The formation of CF, FAP, and CFAP may be related to the high correlation between Fw (r = 0.928, P< 0.01; r = 0.527, P< 0.01; r = 0.608, P< 0.01) and Bw (r = 0.38, P< 0.05; r = 0.38, P< 0.05; r = 0.397, P< 0.05). Total hazard quotient (THQ) for children and adults were <1, revealing no health risks from exposure to B and F through ingestion and skin contact while swimming. The risk characterization ratio; RCRmix(MEC/PNEC) showed high short-term risks to aquatic organisms. Further investigations might emphasis on emerging mitigation strategies to address these concerns.

A comparative study of surfactant distribution and fate (western and eastern) Egyptian Mediterranean coasts focusing on its environmental toxicity.

One of the most difficult-to-manage new contaminants constantly released into the environment is linear alkylbenzene sulphonate (LAS), an anionic surfactant. Significant volumes of LAS are received by the Mediterranean coast of Egypt. The current study is a comprehensive assessment of the environmental fate of the LAS 1505 km off the Mediterranean coast of Egypt in the fall of 2023 in order to track its geographic spread and eventual demise in the water column. Critical analysis of LAS revealed that it is vertically distributed in various ways according to sources, uses, production amounts, and salinity levels. The vertical variation of LAS can be explained by its amphiphilic structure. A significant increase in surfactant concentration (>300 µg/L) was recorded in 66% and 43% of the total samples, ranging from 301.128 to 455.36 and from 304.556 to 486.135 for the western and eastern sides along the Egyptian Mediterranean coast, respectively. Evaluation of the average acute and chronic risk quotient (RQ) along the investigated locations revealed that fish were the most susceptible to LAS in both long and short exposure periods. The presented results also indicated significant LAS toxicity to three trophic levels (RQ values > 1). LAS toxicity to marine organisms was greater in the western than in eastern coastal regions according to acute and chronic mixture risk characterization ratios (RCRmix). The three trophic levels in the study area had the following order of acute relative contribution (RC) to LAS toxicity: fish > invertebrates > algae. The ANOVA test results showed that in both the western and eastern regions, LAS varied significantly (p < 0.05) with salinity (1.04E-60 and 5.44E-42) and depth (6.02E-65 and 1.59E-47), respectively. In addition, a significant difference was observed using the ANOVA test between the eastern and western regions of the Egyptian Mediterranean coast.

Impact of land development along the western Mediterranean coast of Egypt regarding surfactant sources, interfering elements and ecotoxicity.

The effect of recent land development of the western side of the Egyptian Mediterranean coast on the fates, behaviors, interactions, and ecotoxicology of surfactant (LAS), F, Br, B, Ca, Mg, and P was studied. Samples of seawater and sediments were collected from 15 stations at different depths representing, 5 perpendicular sectors. Elevated levels of LAS were identified in seawater columns in the El-Hamam (467.3 ± 220.8 µg/L) and El-Dabaa (480.0 ± 314.1 µg/L) stations. LAS homologue in sediment was in the range of 0.013-0.024, 0.042-0.184, 0.086-0.402, and 0.025-0.058 µg/g for C10, C11, C12, and C13, respectively. Studied parameters showed mixture risk characterization ratios RCRmix > 1 for algae, invertebrates, and fish in seawater and sediments, except for P, which showed low risk (RCRmix ≤ 1) in sediment. Acute relative contribution (RC) of LAS reflected that fish were the most sensitive species (RCFish = 48.5), followed by algae (RCAlgae = 44.4) and invertebrates (RCInvert = 7.1).

Abnormal fluoride distribution, human health risk assessment, predicted no-effect concentration (PNEC) and environmental hazards in an Egyptian lake connected to the Mediterranean Sea.

Fluoride can affect the metabolism and physiological functioning of humans and aquatic organisms like any hazardous substance when it exceeds its permissible limits and PNEC values. The fluoride content of the lake water and sediment samples collected from different locations was determined to assess its risks to humans and its ecological toxicity in Lake Burullus. Statistical analyses show that the proximity of the supplying drains had an impact on the fluoride content. Fluoride ingestion and skin contact in lake water and sediment during swimming for child, female and male were evaluated at 95, 90, and 50%. The values of hazard quotient (HQ) and total hazard quotient (THQ) for children, females and males were less than one, reflecting that exposure to fluoride through ingestion and skin-to-skin contact while swimming poses no risks to human health. PNEC values for fluoride in lake water and sediment were estimated using the equilibrium partitioning method (EPM). The ecological risk assessment of fluoride for acute and chronic toxicity was performed for the three trophic levels based on the PNEC, the half-maximal effective concentration (EC50), the median lethal dose (LC50), the no-observed effect concentration (NOEC), and the 5% lethal concentration (EC05). The risk quotient (RQ), mixture risk characterization ratios (RCRmix), relative contribution (RC), toxic unit (TU), and sum of toxic units (STU) were estimated. The acute and chronic RCRmix(STU) and RCRmix(MEC/PNEC) produced similar values for the three trophic levels in lake water and sediment, indicating that invertebrates are the most sensitive species to fluoride. These results of evaluating the environmental risks of fluoride in lake water and sediments reflected its significant impact on aquatic organisms living in the lake area in the long term.

A comparative study, distribution, predicted no-effect concentration (PNEC) and contamination assessment of phenol with heavy metal contents in two coastal areas on the Egyptian Mediterranean Sea coast.

This study comparing the expected pollution status of phenol along with heavy metals in sediments of two economic regions on the Mediterranean Sea coast using equilibrium partitioning method (EPM) as well as exposure of fishermen and populations to these sediments through ingestion and skin contact while swimming. El-Dekhila (ED) and Abu Talat (AT) regions were different in sediment texture and pollution sources. The expected ecological hazards of phenol in the studied areas were carried out using the equilibrium partitioning method (EPM) by which the partition coefficient of organic carbon-water, KOC (logKOC> 0.95-3.49), octanol-water coefficient, KOW (logKOW> 1.46-1.48) and sediment/liquid partition coefficient, Kd (log Kd < 3) detected high availability amounts of phenol in seawater. Risk quotient (RQ) for phenol in ED region ranged from high to moderate risk, while for AT region was low risk (<0.1); whereas, RQ values of heavy metals in sediments of two studied areas reflected the overall low risk without human hazards (HQ & HI < 1). RQAcute and RQChronic values were above 1 for phenol and heavy metals (Cu and Zn) reflecting that fish were the most sensitive to them in the two regions. Interestingly, this current investigation predicts future contamination of the studied areas especially phenol contamination and its relationship to heavy metals using some reasonable information and allowing the managers to manage how they decide on and protect these two areas. Thus, there is a constant need to use relatively simple tools capable of ensuring protection objectives with a quantity of information with realistic feasibility.

Spatiotemporal distribution of some dissolved salts and minerals in Lake Edku connected to Mediterranean Sea: in relation to different pollutant inputs.

Regarding the generally accepted view of the minerals formed in solving the problem of ecosystem pollution, this research aims to track the role of seasonal minerals in overcoming widespread pollution problems in Lake Edku. At eleven locations inside Lake Edku and three locations in the outside the water inlets, some physical and chemical parameters that affect the formation of minerals and salts were detected seasonally. As a result of human activities from 1972 to 2020, the applied remote sensing technology showed a decrease in the area of Edku Lake by 13.3%. The saturation index (SI) of twelve minerals formed in fifty-six seasonal water samples collected from fourteen locations inside and outside the lake was estimated. The saturation index (SI) of anhydrite (ANH), gypsum (GYP), calcium phosphate (CP), magnesium phosphate (MP), calcite (CAL), aragonite (ARG), dolomite (DOL), magnesite (MGS), fluorapatite (FAP), hydroxyapatite (HAP), octacalcium phosphate (OCP), and carbonate-fluorapatite (CFAP) was calculated. The presented SI values of apatite and phosphate minerals including FAP (SI 30.63-65.65), CFAP (SI 28.14-40.02), HAP (SI 24.83-31.81), Ca3(PO4)2 (SI 23.99-25.95), OCP (SI 19.96-25.47), and Mg3(PO4)2 (SI 15.80-17.46) were high. Palmer-Roger's diagram and piper ternary diagram models reflected the abundance of NaCl in lake water with 30, 40, 46, and 75% in winter, spring, summer, and autumn, respectively. Using correlation matrix, multiple stepwise regression and cluster analysis for statistical analysis, the relationship between sedimentary minerals and outflow and drainage, as well as the role of sedimentary minerals in reducing pollution in the lake area, was outlined.

Human Health Implication of Major and Trace Elements Present in Commercial Crustaceans of a Traditional Seafood Marketing Region, Egypt.

The present study focused on the distribution of some major and trace elements (S (as SO42-), Na, K, B, Ca, Mg, F, Li, Al, Fe, Zn, Cu, Mn, Ni, Co, Cd, and Pb) in both flesh (Fl) and total cephalon/exoskeleton (C/E) tissues of selected crustacean species obtained from an Egyptian traditional seafood marketing region. The sequence of studied elements in (Fl) and (C/E) tissues in descending orders was S (as SO42-) > Na > K > B > Mg > Ca > Li > F > Al > Zn > Fe > Cu > Pb > Ni > Mn > Co > Cd, and S (as SO42-) > Na > B > K > Mg > Ca > F > Li > Al > Fe > Cu > Zn > Mn > Pb > Ni > Co > Cd, respectively. Both length-weight relationship and Fulton's condition factor showed the physical and biological statuses of the crustaceans. Ion quotient calculations of the studied tissues pointed to their importance in decreasing hypertension, preeclampsia, and heart disease. Human health risk due to the consumption of the crustacean species was determined using some guideline limits, metal pollution index (MPI), estimated daily intake (EDI), health comparison values (CVs), dietary intake (DRI-ULs), target hazard quotient (THQ), total target hazard quotient (TTHQ), and provisional tolerable weekly intake (%PTWI). MPI values of cephalon/exoskeleton tissues were greater than those of the flesh with ranges between 11.4-24.0 and 4.6-14.3, respectively. Interestingly, the calculations of TTHQ of toddler and adult were lesser than one and not expected to pose any risk concern to human from crustaceans' consumption.

Halogen content relative to the chemical and biochemical composition of fifteen marine macro and micro algae: nutritional value, energy supply, antioxidant potency, and health risk assessment.

Marine algae have made a strong contribution to global food security in the future. This study is the first report describing the concentration, pathways, and interactions of halogens in 15 species of marine algae collected from the Eastern Harbor in Alexandria, Egypt, relative to 22 key variables. The relationship between halogen content and chemical and biochemical parameters was studied through multivariate analysis. Among all the tested algae, the iodine content was the lowest (2.53-3.00 µg/g). The range of fluoride and chloride in macroalgae (1.12-1.70 and 0.10-0.46 mg/g) was smaller than that of microalgae (0.10-0.46 and 1.48-3.17 mg/g). The bromide content in macroalgae (0.36-5.45 mg/g) was higher than that in microalgae (0.40-0.76 mg/g). The halogen content in macroalgae was arranged in the order of Br > F > Cl > I. In addition, the biochemical parameters such as carbohydrates, proteins, lipids, and certain heavy metals (Fe, Zn, Cu, Mn, Pb, Ni, Co, Cd, and Cr) were determined. Calories, energy, total antioxidant activity (TAC), K/Na, and ion quotient amounts were estimated. The results showed that the green seaweed species had the highest TAC content. In most of the studied algal species, the calculated ion quotient referred to their likelihood of overcoming high blood pressure. The estimated daily intake (EDI) of algae showed no adverse effects on human health. Most of the research variables are below the acceptable WHO/FAO level. Generally, the calorie content of the selected algae is less than 2 kcal, which makes the algae considered an alternative source of healthy food to reduce obesity.Graphical abstract.

Modeling adsorption kinetic of crystal violet removal by electrocoagulation technique using bipolar iron electrodes.

This paper studies the removal of crystal violet (CV) dye by electrocoagulation (EC) process using bipolar iron electrodes. Numerous operating parameters such as initial CV solution concentration, speed of agitation, number of electrodes, type and quantity of supporting electrolyte, temperature- and initial pH were investigated. A complete removal of 10 mg/L CV was achieved within 10 min at pH 7, 0.5 g NaCl, 1 LCV, 750 rpm, 9 sheets, 17.36 mAcm2, and 25 °C. The performed energy-dispersive X-ray spectroscopy (EDAX), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses confirmed the adsorption of CV onto the insoluble iron hydroxide flocs. Amongst the studied adsorption isotherms models, Langmuir and Dubinin-Radushkevich were the most applicable. The kinetic of adsorption of CV onto flocs during the EC operation was studied using the pseudo-first-order, pseudo-second-order, and intraparticulate diffusion models, with results affirming that the adsorption process proceeded according to the pseudo-second-order model. The study of thermodynamic parameters (ΔG0, ΔH0, and ΔS0,) of the CV removal at different temperatures reflected the feasibility of the spontaneous randomness of endothermic adsorption, especially at lower temperatures. The multiple regression equation of the removal of CV by EC technique under the different studied conditions was predicted.

Adsorption isotherms and kinetic studies for the defluoridation from aqueous solution using eco-friendly raw marine green algae, Ulva lactuca.

The defluoridation from aquatic medium by raw marine algae, Ulva lactuca, was investigated. The element components and adsorbent's properties were determined. The influence of pH, contact period, and Ulva sp. weight on the deflouridation was achieved. The complete defluoridation of 10 mg F-/l solution was obtained within 10 min at definite pHs. Fourteen adsorption isotherms and four kinetic models (pseudo-first order and pseudo-second order, Elovich, and intraparticle diffusivity) were studied. The most adequate model was performed by using five error functions. The application of chi-squared test indicated that the nonlinear isotherm models (two and three parameters) were more applicable than the linear ones. The adsorption kinetic proceeded by pseudo-first-order model. The adsorption mechanism was very complex; thus, the solute distribution step was not the only dominant one during the process. The adsorption seemed to be a physical negative binding cooperative type with activation energy and free energy of 3.16 and - 1.672 kJ/mol, respectively. Thus, raw marine algae, Ulva lactuca, can be used as an adsorbent in solving the fluoridation problem in aquatic mediums throughout the world due to their fast procedure, high efficiency, low effort, and high economic value.

Assessment and Ecological Risk of Heavy Metals in Sediment and Molluscs from the Mediterranean Coast.

Heavy metal contamination in both sediments and molluscs from the Egyptian Mediterranean coast was investigated. Seawater, sediments, and mollusc samples were collected from representative locations along the coastal area. Different representations of the data set, including, statistical methods (correlation matrix and cluster analyses), various sediment quality assessment methods, and bioaccumulation factor calculation, were combined to investigate the trends of heavy metals, identify pollution sources, and assess sediment quality from a toxicological point of view. The measurements of dissolved oxygen (DO) revealed to relatively well oxygenate surface water in all locations. There is a distinct change in the contents of heavy metals (Fe, Al, Zn, Cu, Ni, Cr, Pb, Cd, and Hg) among the sampling sediments. The statistical interpretations showed that the bio-availability of the studied heavy metals is controlled by different factors, including the geochemistry of sediments, the hydrology of the system, the uptake of metals from sediments, as well as human anthropogenic activities. Although, there are still certain points of the Egyptian Mediterranean coast with a relatively high concentration of toxic metals, the toxicological approach suggests that the risk for living organisms is not high, but, in the long run, toxicological implications can appear. These results can provide useful information for the local managers and decision makers.

The distribution, contamination and risk assessment of heavy metals in sediment and shellfish from the Red Sea coast, Egypt.

Zn, Cu, Ni, V, Al, Pb, Cd, Hg, lipid and water contents were determined in the soft tissues of different shellfish species collected along the Red Sea shoreline. Metal contents showed a descending order of Zn > Cu > Ni > Al > V > Pb > Cd > Hg. The leachable concentrations found in the sediments gathered from the studied locations gave another descending order: Al > Zn > Ni > Pb > V > Cu > Cd. The determined leachable heavy metal contents in the sediment did not exceed the NOAA and CCME (Anonymous 1999) sediment quality guidelines. Accordingly, the sediments along the Egyptian Red Sea area did not pose any adverse impacts on the biological life. According to the hazard quotient (HQ) calculations for heavy metal contents in the soft tissue of shellfish, mercury did not pose any risk on human health; whereas, the other determined heavy metals gave HQ values of 1 < HQ < 10 and showed a possibility of risk on the long term. Cu is above the desirable levels in mussels. The RQ calculations of toddlers and adults reflected that Cu was the only heavy metal that had an adverse effect on toddlers' health. Based on the human organizations (EPA, BOE, MAFF, and NHMRC) that proposed safety concentrations of heavy metals, the studied shellfish were somewhat safe for human consumption.

Risk Assessment of Organochlorines in Mollusk from the Mediterranean and Red Sea Coasts of Egypt.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) residues were studied in different mollusk species from the Egyptian Mediterranean and Red Sea coasts. The average levels of OCPs in mollusks comprised chlordanes, dieldrins, total endrin, endosulfan compounds, and methoxychlor (DECEM), dichlorodiphenyltrichloroethanes (DDTs), and, hexachlorocyclohexanes (HCHs). The averages of HCHs, DDTs, and polychlorinated biphenyls (PCBs) in mollusks from the Mediterranean Sea were 1.13±1.21, 1.30±1.27, and 1.40±0.93 ng/g, respectively; from the Red Sea, they were 0.62±0.90, 1.77±1.82, and 6.44±5.05 ng/g, respectively. The analysis of HCHs, DDTs, and PCBs in mollusks indicates a new usage of lindane, PCB congeners, and the input of technical HCH and aged DDT. The data showed that the Red Sea Coast was more affected by PCBs congeners than the Mediterranean Sea Coast, which may be attributed to the different activities along the two coastal areas. Mollusks in the Mediterranean Sea had higher dieldrins, total endrin, endosulfan compounds, and methoxychlor contents than those in the Red Sea. Interestingly, HCHs, DDTs, and PCBs levels were lower than those recommended for Swedish Food Regulation and U.S. Food and Drug Administration, which means that mollusks from these two coastal areas are safe as food.

Anomalous distribution of fluoride and phosphorus forms in surface sediments along eastern Egyptian Mediterranean Sea coast.

The study focused on the distribution of fluoride, total phosphorus, and four phosphorus fractions in some sites along the Egyptian Mediterranean Sea coast. The geochemical parameters and textures of 30 surficial sediment samples from six sectors were determined. The sediment's geochemical parameters (total carbonates (TCO3) and total organic carbon (TOC), exchangeable and carbonate-associated phosphorus (Pex), iron- and aluminum-associated phosphorus (POH), calcium-associated phosphate/apatite (PHCl), residual phosphorus (PR), total phosphorus (TP), calcium (Cas), magnesium (Mgs), and fluoride (Fs)) showed variable values. The rank of phosphorus fractions in the sediments PHCl > PR > POH > Pex reflected that the eastern Egyptian coast was still uncontaminated. Generally, Pex levels gave a gradual increase in the offshore direction, while POH values varied along the stations of each sector. Also, the presented data indicated that the apatite-P fraction was the main storage of the phosphate in the sediments with a contribution to TP ranging from 58 to 87 %. The highest and lowest average fluoride contents (0.49 ± 0.10 and 0.25 ± 0.31 mg/g) were determined in the Port Said and Damietta sectors, respectively. Interestingly, the variability of both phosphorus and fluoride levels in the investigated area seemed to be accompanied with the sediment's character beside the proximity to potential effluent sources.

Sedimentology, geochemistry, pollution status and ecological risk assessment of some heavy metals in surficial sediments of an Egyptian lagoon connecting to the Mediterranean Sea.

Spatial distribution of heavy metals (Co, Cu, Ni, Cr, Mn, Zn and Fe) was studied on Lake Edku's surface sediments in relation to sedimentology and geochemistry characteristics and their contamination status on the ecological system. Lake Edku's sediments were dominated by sandy silt and silty sand textures and were enriched with carbonate content (9.83-58.46%). Iron and manganese were the most abundant heavy metals with ranges of 1.69 to 8.06 mg g(-1) and 0.88 to 3.27 mg g(-1), respectively. Cobalt and nickel showed a harmonic distribution along the studied sediments. The results were interpreted by the statistical means. The heavy metal pollution status and their ecological risk in Lake Edku was evaluated using the sediment quality guidelines and the contamination assessment methods (geoaccumulation, pollution load and potential ecological risk indices, enrichment factor, contamination degree as well as effect range median (ERM) and probable effect level (PEL) quotients). Amongst the determined heavy metals, zinc had the most ecological risk. Overall, the heavy metals in surface sediments showed ecological effect range from moderate to considerable risk, specially, in the stations in front of the seawater and in drain sources that had the highest toxic priority.

Bioavailability of heavy metals in fresh water Tilapia nilotica (Oreachromis niloticus Linnaeus, 1758): potential risk to fishermen and consumers.

The study was undertaken to assess the accumulation of some heavy metals (Cr, Co, Cu, Ni, Zn, Pb and Cd) in different tissues (muscle, gills, heart, liver, brain, bone and skin) of Tilapia nilotica. It is one of the most edible fish species in Egypt and was collected from a commercial fish farm in order to evaluate their potential risk to fishermen and consumers. This fish farm is fed with discharged water containing agricultural, industrial, sewage and domestic wastes. The length-weight relation and condition factor calculation of Tilapia nilotica samples showed a significant linear regression (r(2) = 0.920) and an average condition factor of 4.1 g/cm(3). This indicated that the health status for the studied fish samples was good. Metal pollution index (MPI) values for the determined heavy metals in the different tissues reflected that the muscle was the only tissue that had the lowest content. Provisional Tolerable Weekly Intake (PTWI) values for the investigated heavy metals were lower than those reported for the permissible limits. The data were evaluated by using ANOVA statistical analysis. For appraising the human health risk effects of heavy metals in fish muscle, estimated dietary intake (EDI) and hazard quotient (HQ) were determined. HQ levels indicated that Cr and Co were the only heavy metals among the determined ones that had values more than unity. Also, their relative contributions in fish consumptions were Cr> Co> Pb> Ni> Cu> Cd> Zn. The highest average HQ value of chromium determined in this study referred to the possible adverse effects of Cr on human health. Accordingly, the potential public health risks from dietary exposure to hazardous contaminants in fish species from fish farms must be continually subjected to research, regulation and debate.

Ecotoxicological impact assessment of some heavy metals and their distribution in some fractions of mangrove sediments from Red Sea, Egypt.

The total and fraction concentrations of heavy metals (Mn, Cu, Ni, Pb, Co, and Cd) were analyzed in some sediment fractions (Φ2, Φ3, Φ4, Φ5) of selected mangrove ecosystems collected from the Egyptian Red Sea shoreline. The results revealed that manganese had the highest mean value (133 ± 97 mg/kg) followed by copper (49.9 ± 46.0 mg/kg), nickel (28.1 ± 11.8 mg/kg), lead (19 ± 13 mg/kg), cobalt (6.7 ± 4.0 mg/kg), and cadmium (3.327 ± 1.280 mg/kg). The concentrations of heavy metals in the different sediment fractions showed that there was a preferential accumulation of Cu, Co, Mn, and to a lesser degree Cd in the silt and clay fractions rather than in the sand-sized. The sediment quality was performed by using some sediment quality guidelines. Additionally, the contamination and the risk assessment of these heavy metals were achieved by different methods including, potential ecological risk index, contamination factor, pollution load index, and geoaccumulation index. According to the Sediment Quality Guidelines comparisons, the concentrations of Mn and Pb were low and showed no possibility of detrimental effects on the local environment. The levels of Cu and Ni were high, however, could not be considered to present serious threat to the mangrove ecosystem. The data showed that the mangrove ecosystems were affected by the Cd risk.

Chemical composition of some seaweed from Mediterranean Sea coast, Egypt.

This study pointed to the assessment of the chemical composition (F, Ca, Mg, Na, K, Fe, Mn, Zn, Cu, Ni, Co, Cr, Cd, and carbohydrate) of different marine seaweeds (red, green, and brown) from the Egyptian Mediterranean Sea coast. The results showed that green seaweeds supplied better calcium sources than the red and brown ones. Also, red and brown seaweeds showed higher averages of Na and K than that in green species and these seaweeds could play an important role in the electrolyte balance in humans. On the other hand, green seaweeds gave the highest average carbohydrate concentration; thus, these green species could be used as a source of polysaccharides. Ion quotient values for almost seaweed species were between 1.4 and 4.0, so they can reduce hypertension, preeclampsia, and heart disease in human beings. Interestingly, the calculated hazard quotient of elements was below 1. Accordingly, these seaweed species were of high quality and safety and might be used in the field of nutrition.

Assessment of some heavy metals in surface sediments of the Aqaba Gulf, Egypt.

Aqaba Gulf is an economically important marine environment in Egypt. Its coastal area was subjected to anthropogenic impact of urbanization and economic development during the last decades. The study was oriented to investigate the distribution as well as assess the heavy metal pollution status (Fe, Mn, Zn, Ni, Co, Cr, Cu, and Cd) in its surface sediment. Large heavy metals fluctuations were detected along the studied area. The results pointed out to the highly significant correlations among Fe, Cu, Ni, and Co heavy metals and their similar lithogenic origin beside their input sources. The sediment quality was performed by using the geo-accumulation index (I (geo)) and different sediment criteria guidelines; China State Bureau of Quality and Technical Supervision (CSBTS), and Canadian guidelines. Among the studied heavy metals, Cd was the only metal that showed moderate pollution for I (geo) as well as it exceeded the primary and the secondary criteria of CSBTS and the threshold effect level of the Canadian guidelines (TEL). On the other hand, the other heavy metals were within the natural background levels.

Physicochemical and geochemical characteristics of raw marine sediment used in fluoride removal.

The study was directed to use raw marine sediment in the removal of fluoride. The sediment was mainly composed of calcite, magnesium-calcite and aragonite. The effect of the initial fluoride concentration, pH and the contact time was studied at room temperature to determine the adsorption capacity of the sediment. The optimum adsorption capacity was observed at pH values of 5 and 6.2. The adsorption process was fast and the equilibrium was reached within 60 min. For fluoride solutions of 10 and 15 mg/L, 100% removal was obtained onto 0.1 g of raw marine sediment. Pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion equations were used to deduce the kinetic data. The adsorption mechanism was rather complex process, and the intra-particle diffusion was not the only rate-controlling step. The equilibrium data were tested using thirteen isotherm models (Langmuir, Freundlich, Tempkin, Dubinin-Radushkevich, Erunauer-Emmett-Teller, Flory-Huggins, Non-ideal competitive adsorption, Generalized, Redlich Peterson, Khan, Sips, Koble Corrigan and Toth isotherm equations). Five different error functions were applied. For the sorption of fluoride process, the calculated activation energy and the free energy were of 0.707 and -14.491 kJ /mol, respectively.