Dr. Gehan El Zokm is a professor at the Marine Chemistry Department and leader of the halogen, sulfide modeling, and surfactant groups at the National Institute of Oceanography and Fisheries, Mediterranean Sea Branch in Egypt. She earned her B.Sc., M.Sc., and Ph.D. in the Chemistry Department at the Faculty of Science of Alexandria University in Alexandria, both of which concerned heavy metal chemistry (focusing on preconcentration and fractionation tools). She is a specialist in environmental chemistry in the Marine Environment Division. Her research interests are in analytical and instrumental analytical chemistry with an emphasis on fractionation techniques (metals, sulfur, phosphorus, and nitrogen) regarding their bioavailability. Sulfide-metal dynamic models’ topic has been a great concern in her publications. Statistical analyses were the most prominent features of her research, which was conducted using the most recent software packages. Her papers discussthe topics of eutrophication and pollution as well as the responses of marine biota to these two phenomena. Her study focuses on the mobility and fluxes of various parameters within marine environmental compartments. Her recent projects include natural product extraction for a variety of applications as well as method characterization (FTIR, XRD, SEM, TEM, EDEX, GC, HPLC, UV-Vis, and BET). Nutritional and functional food studies are highlighted in her research. Her research is also focused on water treatment and the mobility as well as fluxes of pollutants (heavy metals, phenol, hydrocarbons, and pesticides). She has 50 research papers and two books with an H-index of 17. A factorial design is applied for water treatment experiments. She reviews a lot of papers for many important publishers (Elsevier, Springer, and Taylor & Francis). She supervised and headed several projects and postgraduate students, participated in many conferences and workshops, and has several activities.

• Chapter I; Introduction to the Significant Impact of AVS on Controlling the Metal Toxicity Regarding Sulfur Cycle.- Chapter II; Chemistry of Sulfur Components and Factors Controlling AVS Concentrations in Marine Environment.- Chapter III; Experimental Approach to Sampling, Storage, Extraction, Determination of AVS-SEM.- Chapter IV; AVS-SEM MODELS.- Chapter V; A Review and an Outlook "AVS- SEM"   Studies in Egypt Compared to Aquatic Environment around the World.- Chapter VI; Update, Conclusions, Recommendations, Future Perspective and Challenges.

Dr. Gehan El Zokm is a professor at the Marine Chemistry Department and leader of the halogen, sulfide modeling, and surfactant groups at the National Institute of Oceanography and Fisheries, Mediterranean Sea Branch in Egypt. She earned her B.Sc., M.Sc., and Ph.D. in the Chemistry Department at the Faculty of Science of Alexandria University in Alexandria, both of which concerned heavy metal chemistry (focusing on preconcentration and fractionation tools). She is a specialist in environmental chemistry in the Marine Environment Division. Her research interests are in analytical and instrumental analytical chemistry with an emphasis on fractionation techniques (metals, sulfur, phosphorus, and nitrogen) regarding their bioavailability. Sulfide-metal dynamic models’ topic has been a great concern in her publications. Statistical analyses were the most prominent features of her research, which was conducted using the most recent software packages. Her papers discussthe topics of eutrophication and pollution as well as the responses of marine biota to these two phenomena. Her study focuses on the mobility and fluxes of various parameters within marine environmental compartments. Her recent projects include natural product extraction for a variety of applications as well as method characterization (FTIR, XRD, SEM, TEM, EDEX, GC, HPLC, UV-Vis, and BET). Nutritional and functional food studies are highlighted in her research. Her research is also focused on water treatment and the mobility as well as fluxes of pollutants (heavy metals, phenol, hydrocarbons, and pesticides). She has 50 research papers and two books with an H-index of 17. A factorial design is applied for water treatment experiments. She reviews a lot of papers for many important publishers (Elsevier, Springer, and Taylor & Francis). She supervised and headed several projects and postgraduate students, participated in many conferences and workshops, and has several activities.

• Chapter I; Introduction to the Significant Impact of AVS on Controlling the Metal Toxicity Regarding Sulfur Cycle.- Chapter II; Chemistry of Sulfur Components and Factors Controlling AVS Concentrations in Marine Environment.- Chapter III; Experimental Approach to Sampling, Storage, Extraction, Determination of AVS-SEM.- Chapter IV; AVS-SEM MODELS.- Chapter V; A Review and an Outlook "AVS- SEM"   Studies in Egypt Compared to Aquatic Environment around the World.- Chapter VI; Update, Conclusions, Recommendations, Future Perspective and Challenges.

Dr. Gehan El Zokm is a professor at the Marine Chemistry Department and leader of the halogen, sulfide modeling, and surfactant groups at the National Institute of Oceanography and Fisheries, Mediterranean Sea Branch in Egypt. She earned her B.Sc., M.Sc., and Ph.D. in the Chemistry Department at the Faculty of Science of Alexandria University in Alexandria, both of which concerned heavy metal chemistry (focusing on preconcentration and fractionation tools). She is a specialist in environmental chemistry in the Marine Environment Division. Her research interests are in analytical and instrumental analytical chemistry with an emphasis on fractionation techniques (metals, sulfur, phosphorus, and nitrogen) regarding their bioavailability. Sulfide-metal dynamic models’ topic has been a great concern in her publications. Statistical analyses were the most prominent features of her research, which was conducted using the most recent software packages. Her papers discussthe topics of eutrophication and pollution as well as the responses of marine biota to these two phenomena. Her study focuses on the mobility and fluxes of various parameters within marine environmental compartments. Her recent projects include natural product extraction for a variety of applications as well as method characterization (FTIR, XRD, SEM, TEM, EDEX, GC, HPLC, UV-Vis, and BET). Nutritional and functional food studies are highlighted in her research. Her research is also focused on water treatment and the mobility as well as fluxes of pollutants (heavy metals, phenol, hydrocarbons, and pesticides). She has 50 research papers and two books with an H-index of 17. A factorial design is applied for water treatment experiments. She reviews a lot of papers for many important publishers (Elsevier, Springer, and Taylor & Francis). She supervised and headed several projects and postgraduate students, participated in many conferences and workshops, and has several activities.

• Chapter I; Introduction to the Significant Impact of AVS on Controlling the Metal Toxicity Regarding Sulfur Cycle.- Chapter II; Chemistry of Sulfur Components and Factors Controlling AVS Concentrations in Marine Environment.- Chapter III; Experimental Approach to Sampling, Storage, Extraction, Determination of AVS-SEM.- Chapter IV; AVS-SEM MODELS.- Chapter V; A Review and an Outlook "AVS- SEM"   Studies in Egypt Compared to Aquatic Environment around the World.- Chapter VI; Update, Conclusions, Recommendations, Future Perspective and Challenges.