Geochemistry of seawater the chemicals mixed in sea water.pptx

To known about the geochemistry of the sea water .what were the chemicals that were mixed with the sea water.

1. Geochemistry of sea water Submitted to: Dr.V.Perumal , Teaching Assistant, Alagppa University, Karaikudi Submitted by: J.Dhivagar Alagppa University, Karaikudi .

2. The geochemistry of seawater involves studying its chemical composition, the processes that control the distribution of dissolved elements and compounds, and the interactions between the ocean, atmosphere, and seafloor. Key components include the analysis of salts, gases, nutrients, trace elements, and biological influences. INTRODUCTION

3. Salinity and Major Ions Salinity measures the total amount of dissolved salts in seawater, typically about 35 parts per thousand (‰). The six major ions in seawater, contributing to its salinity, are:Sodium (Na⁺)Chloride (Cl⁻)Magnesium (Mg²⁺) Sulfate (SO₄²⁻)Calcium (Ca²⁺)Potassium (K⁺) These ions make up more than 99% of dissolved salts.

4. Trace ElementsTrace elements are present in small concentrations but are vital to biological and geochemical processes. Common trace elements include:Iron (Fe), essential for phytoplankton growth.Zinc (Zn), Copper (Cu), and Manganese (Mn), involved in enzymatic processes.Cobalt (Co) and Nickel (Ni), which also influence marine life. Dissolved GasesSeawater contains dissolved gases essential to life, such as:Oxygen (O₂), necessary for respiration.Carbon dioxide (CO₂), involved in the carbon cycle and ocean acidification.Nitrogen (N₂), which is less reactive but important for nitrogen fixation. The concentration of these gases varies with depth, temperature, and biological activity.

5. Nutrients and Biological ProcessesNutrients like nitrate (NO₃⁻), phosphate (PO₄³⁻), and silicate ( SiO ₄⁴⁻) are vital for the growth of marine organisms, especially phytoplankton. They are recycled through biological processes such as:Photosynthesis in surface waters.Decomposition and nutrient release in deeper waters.Biogeochemical cycles help regulate nutrient availability and ocean productivity. Carbonate System and Ocean AcidificationThe carbonate system (CO₂, HCO₃⁻, CO₃²⁻) is crucial for regulating seawater pH and buffering capacity.As CO₂ dissolves in seawater, it forms carbonic acid (H₂CO₃), which dissociates into bicarbonate and carbonate ions. This system helps maintain ocean alkalinity but also contributes to ocean acidification as atmospheric CO₂ levels rise, lowering the pH of seawater.

6. pH and AlkalinityThe average pH of seawater is around 8.1, making it slightly alkaline. It varies with depth, temperature, and local biological activity.Alkalinity refers to the ability of seawater to neutralize acids, largely controlled by the presence of bicarbonate and carbonate ions. Hydrothermal Vents and Geochemical CyclingHydrothermal vents at mid-ocean ridges release chemically altered seawater rich in metals like iron, manganese, and sulfur , contributing to the deep ocean's chemistry.Vents also introduce heat and affect the chemical gradients in deep waters.

7. Redox ReactionsRedox (reduction-oxidation) reactions control the cycling of many elements, especially in oxygen-deficient areas (anoxic zones). These processes affect elements like iron (Fe) and sulfur (S) in seawater. Residence TimeElements have varying residence times, the average time they remain in seawater before being removed (e.g., by biological uptake or precipitation). Sodium has a long residence time (millions of years), while nutrients like nitrate have shorter timescales due to rapid biological cycling.

8. Human ImpactsPollution , eutrophication (excess nutrient loading), and rising atmospheric CO₂ levels influence the geochemistry of seawater, affecting ecosystems and global climate processes. Seawater geochemistry plays a central role in understanding ocean circulation, marine life, and the global carbon cycle, making it vital for assessing climate change and ocean health.

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