EES 333/413: Environmental Chemistry - Lecture Notes, Essays (university) of Geology

Download EES 333/413: Environmental Chemistry - Lecture Notes and more Essays (university) Geology in PDF only on Docsity!

EES 333/413: Environmental Chemistry

(Instructor: Ashis Biswas)

Grading Scheme

1. Calculation of final marks: o Quiz – 1 ( 10% ) o Quiz – 2 / Presentation ( 10% ) o Mid-semester exam ( 30% ) o End-semester exam ( 50% )
2. Grading: o Relative grading

Atmosphere

o Thin layer of gas above the earth surface o Source of major components of the life molecules (e.g. C, O, N, etc.) o Absorbs energy and coming from sun – moderates earth’s temperature – transports energy away from the equatorial regions o Absorbs harmful ultraviolet (UV) radiation coming from sun o Pathway of transporting water (as vapour) from sea to land – supports water transport in the hydrologic cycle

Geosphere

o Solid earth o Consists of different layers: I. Iron rich solid inner core II. Molten outer core III. Mantle IV. Crust o Lithosphere – consists of outer mantle and crust – most important part of the geosphere involves in the environmental processes – actively interacts with atmosphere, hydrosphere, and biosphere o Soil – outermost part of the lithosphere – important to support terrestrial life – formed by weathering of rock Source: https://en.wikipedia.org/wiki/Lithosphere

Biosphere

o All living entities on earth o Biotic – living organisms and the environment directly affecting them o Abiotic – rest of the environments

Anthrosphere

o Environment that is created or modified by human – technological intervention to the environment to ensure food, shelter, and goods that are required for their survival and well-being o Irreversible change in the environments o Sustainability?

Environmental Science & Environmental Chemistry

➢ Importance of the environment

o Environment in the earth supports life

➢ Environmental Science

o Science related to the complex interactions among different spheres of the environment

➢ Environmental Chemistry

o Sub-discipline of the ‘Environmental Science’ o Study of processes related to source, mobilization, reaction, transport, effect, and fate of chemical species in different spheres of the environment o Diverse topic – e.g. deals with Freon reaction in the stratosphere as well as PCB deposit in the ocean sediment o Deals with natural system; more complicated than traditional chemistry

➢ Learning goal

o To build-up fundamental chemical knowledge that you can use to solve (or make an educated guess) any environmental challenge

Calculation of Activity Co-efficient for Ionic Species

When I >1, Pitzer Model Source: Merkel and Planer-Friedrich, 2008

Aqueous Complexation

Literature: Langmuir 1997, Aqueous Environmental Geochemistry (chapter 3)

Hydration of Metal Ion in Water

Types of Ligand

Variation of Concentration of Different Complexes of Cd

with Cl

as a Function of Cl

Concentration

Electronegativity (EN) Difference and Complex Formation

o With increase of electronegativity difference between metal ion and ligand, formation of ion pair (outer-sphere complex) increases o With decrease of electronegativity difference formation of inner-sphere complexes increases o ∆EN <1.7 – covalency predominates; ∆EN >1.7 – ionicity predominates (Pauling 1966)

Stability of Inner-sphere Complex - I:

Concept of Hard and Soft Acid and Base

o Hard species : comparatively rigid; electron cloud is nondeformable, have low polarizability, hold their electrons firmly o Soft species : electron cloud is easily deformable or polarizable o Hard acid form strong ion pair with hard base o Soft acid form strong covalent complex with soft base o Hard-soft or soft-hard acid and base complexes are weak and rare o Class A metal ions: with noble gas electron configuration, hard acids o Class B metal ions: with electron configurations of Ni^0 , Pd^0 , or Pt^0 ; mono- and di-valent cations are soft acid, whereas higher valent cations are hard acids o Class C metal ions: have 0 to 10 d subshell electrons in the M shell (first series) or N shell (second series); divalent cations are border line acids and higher valent cations are hard acids