Kimia Logam Berat

Logam berat

• Yang termasuk dalam logam

berat antara lain:

Hg, Pb, Cd, Cr, As, Cu, Cr, Ni,

Co, Mg

• Tersebar merata

• Toksisitas tinggi

• Nondegradable

Densitasnya lebih tinggi jika

dibandingkan dengan logam lain

Tabel: apakah semua logam berat bersifat

toksik?

http://php.med.unsw.edu.au/embryology/images/1/18/Heavy_metals_toxicity.gif

Apa itu Logam Berat?

Yang termasuk dalam Logam Berat.

• Heavy metals are chemical elements that have a specific

gravity (a measure of density) at least five times that of

water.

• generally interpreted to include those metals from periodic table groups IIA through VIA

• Heavy metals are natural constituents of the Earth's crust and are present in varying concentrations in all ecosystems

• Metals differ from other toxic substances in that they are neither created nor destroyed by humans. Therefore, they tend to accumulate in the soils, seawater, freshwater, and sediments.

Introduction

Although we commonly think of heavy metals as water

pollutants, they are for the most part transported from place

to place via the air, either as gases or as species absorbed

on, or absorbed in, suspended particulate matter. (Baird,

2011)

• Metals are probably the oldest toxins known to

humans. Lead usage may have begun prior to 2000

BC in the smelting of silver. Arsenic was obtained

during the melting of copper and tin, and an early

use was for decoration in Egyptian tombs/

Speciation and Toxicity

• Unsur bebas bersifat tidak toksis (kecuali uap Hg)

• Bersifat toksis sebagai kation

Putnam, 1972

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• Mercury is a contaminant of our water ways. Humans are exposed to mercury in the fish they eat as well as in the amalgam fillings in their teeth.

• Arsenic is found naturally in high concentration in drinking water in various parts of the world. Cadmium has been classified as a known human carcinogen.

CHEMICAL AND PHYSICAL

PROPERTIES

CHEMICAL AND PHYSICAL PROPERTIES

• 1. Physical states - solids, liquids, gases aerosols

• 2. Elements - indestructible

• 3. Electrophyllic cations - react with ligands reversible complexes molecular mimicry

• 4. Oxidation States affects toxicity

• 5. Organometallic compounds differ from inorganic

• 6. Essential versus non-essential

• Heavy metals (HM) exert their toxic effects by combining with one or more reactive groups (ligands) essential for normal physiological functions.

• Heavy metal antagonists (HMA) - chelating agents are designed specifically to compete with these groups for the metals, and thereby prevent or reverse toxic effects and enhance excretion of metals.

Sources of heavy metal pollution ATMOSPHERIC

Metals can be transferred by the atmosphere in gas or particle form (aerosol)

• Particles can fall from the atmosphere onto the land or sea = dry deposition

• Also precipitation can carry particles or dissolved gases = wet deposition

• Gaseous state elements (Boron, Mercury, Selenium) can also dissolve at the surface of water bodies (gaseous exchange)

• Bubbles breaking the surface of the sea can release salt particles containing metals

– can travels from sea to atmosphere as well as atmosphere to sea

Sources of heavy metal pollution RIVERS

• Erosion of rocks containing metals

• Surface runoff sweeps up naturally formed and anthropogenic metal particles

Metals often bind with sediments and are deposited on the seabed

– but these can enter the marine environment again is there is:

– Dredging

– Trawling

– Severe weather

Sources of heavy metal pollution

GROUNDWATER SEEPAGE

• Dissolved substances are carried via ground

water movement – contamination in soil may

be picked up by the moving waters

DELIBERATE DISCHARGE

• Contaminated waste dumping

• Industrial discharges

• Sewage