Dasar-dasar Reaksi dan Sifat

Kimia Alam

AF Assomadi

Kuliah Kimia Lingkungan I

Hubungan

antar

sistem

lingkungan

dengan

manusia

dan

kehidupan

Environmental

Chemistry

Is the study of the sources, reactions, transport, effects, and fates of chemical species in water, soil, air, and living environments, and the effects of technology thereon

Pertukaran Zat/Materi antar sphere

Siklus Karbon (C-Cycle)

Siklus Nitrogen (N-cycle)

Siklus

Sulfur

(S-cycle)

Siklus Fosfat (P-cycle)

Beberapa impact teknologi pada

lingkungan Agricultural perubahan lahan, drainase,

irigasi, pestisida Manufacturing polusi udara, polusi air, by-

produk limbah hazard dsb Extraksi and produksi mineral kerusakan

lingkungan dan polusi Produksi Energi dan penggunaannya

kerusakan lahan/tanah, polusi air (garam), emisi polutan udara (hujan asam) dsb

Transportasi Modern automobile, perubahan struktur tanah (jalan), emisi polusi udara, peningkatan penambangan minyak dsb

technology can be applied to minimize

environmental impact

maximum energy efficiency, maximum utilization of raw materials, and minimum production of pollutant by-products

minimize pollution problems

maximum materials recycling and minimum waste product production

advanced biotechnologies

catalysts for efficient synthesis

minimize waste production

Steady State Addition and Removal

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Kimia Air

Siklus Air

(hydrolo

gic

cycle)

dalam triliun

liter/hari

Sifat

Air

Air Struktur terdiri atas 2 atom H

dan 1 atom O dalam setiap molekulnya

Struktur bersudut 105 o moment dipol tidak nol (polar)

Kemampuan sangat besar membentuk ikatan hidrogen (kelarutan molekul, logam, suspensi)

Pelarut yang universal Kapasitas panas tinggi Densitas terbesar pada 4 oC

(jaminan kelangsungan hidup)

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Ikatan Hidrogen

19

Water Chemistry

The polarity of water causes it to be cohesive and adhesive.

Polarity unequal charge distribution in a molecule resulting in a region and a + region

cohesion: water molecules stick to other water molecules by hydrogen bonding

adhesion: water molecules stick to other polar molecules by hydrogen bonding

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Water Chemistry

cohesion

21

Water Chemistry

adhesion

Stratifikasi Air danau

Major Aquatic Chemical Process

Kesetimbangan CO2-CaCO3 di air

Oksidasi-Reduksi di Air

Oksigen di Air

O2 dibutuhkan terlarut di air untuk menjaga reaksi oksidasi-reduksi, respirasi, degradasi dst

Kelarutan O2 di air tergantung temperatur, pd 25 oC sekitar 8,5 mg/L; pada 0oC 14,74 mg/L

Dihasilkan dari proses fotosintesis alga/tumbuhan hijau di air dan proses aerasi

CO2 di Air

Kesetimbangan CO2 di Air

29

Acids and Bases

Hydrogen ion (H+1) is the basis of the pH scale.

Greater H+1 concentration --- lower pH (acidic)

Lower H+1 concentration --- higher pH (basic)

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Acids and Bases

Acid: a chemical that releases H+1 ions.

pH below 7

Base: a chemical that accepts H+1 ions.

pH above 7

Buffer: a chemical that accepts/releases H+1 as necessary to keep pH constant

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Acids and Bases

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Acids and Bases

Most biological buffers consist of a pair of molecules, one an acid and one a base.

BUFFER SYSTEM IN HUMAN BLOOD

BASE ACID

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Acids and Bases

34

Properties of Water

1. Water has a high specific heat.

- A large amount of energy is required to change the temperature of water.

2. Water has a high heat of vaporization.

- The evaporation of water from a surface causes cooling of that surface.

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Properties of Water 3. Solid water is less dense than liquid water.

- Bodies of water freeze from the top down.

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37

Properties of Water

4. Water is a good solvent.

- Water dissolves

polar molecules and

ions.

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Properties of Water

5. Water organizes nonpolar molecules. - hydrophilic: water-loving -hydrophobic: water-fearing - Water causes hydrophobic molecules to

aggregate or assume specific shapes.

6. Water can form ions. H2O OH

-1 + H+1

hydroxide ion hydrogen ion

Ionization; happens spontaneously

Concentrations of main ions (Ca2+, Mg2+, K+, Na+, HCO3-, SO4

2-, Cl-, NO3-

)

Monitoring surface waters chemistry

1954-1955, 1990-1991, 2000-

2001 Tebo fishpond basin

1964 - 2007 Stropnice river

Water Quality Parameters

Temperature - Dissolved Oxygen (DO) - pH

Alkalinity - Hardness

Nitrates and Phosphates - Turbidity

Conductivity

-

Temperature

Affects:

Water density

Gas solubility

Chemical reaction rates

Organism growth rates

Conductivity

pH

Dissolved Oxygen

Q10 rule cold-blooded aquatic organisms

Predicts that growth rate will double

if temperature increases by 10C (18F) within their "preferred" range.

Gases Dissolve in Water

Dissolved Oxygen (DO)

DO is the measurement of oxygen

dissolved in water and available for

fish and other aquatic life.

Indicates health of an aquatic system.

Can range from 0-18 ppm.

Most natural water systems require 5-

6 ppm to support a diverse population.

Varies with time of day, weather, temperature.

Dissolved Oxygen (DO)

Increase in organic waste

Increase in algae/plant vegetation

Decrease in DO available to organisms

Leads to changes in ecosystem as

organisms needing lots of DO are

replaced by organisms needing little.

pH - p(otential of) H(ydrogen)

Determines the solubility of nutrients (PO4-3, NO3

-, C)

and heavy metals (Fe, Cu, etc)

Determines availability of these chemicals for use by aquatic life.

In natural water systems, determined largely by geology and soils.

pH of natural waters

due to humic acid

Limestone, marble, CO3 rich

Pure rain, snow

Sea water

Factors that affect pH

Algal blooms Bacterial activity Water turbulence Chemicals flowing into the water body Sewage overflows Pollution

How pH affects aquatic life

Decreasing pH (e.g.: via acid rain)

Liberation of Al, metals

Toxic conditions

Chronic stress

Smaller, weaker fish

Alkalinity

Alkalinity refers to the capability of water to neutralize acid.

Buffering capacity resistance to pH changes.

Common natural buffer: CO3

(carbonates like limestone).

Protects aquatic life.

Commonly linked to water

hardness.

In natural systems:

50 150 mg/L as CaCO3.

Limestone outcrop

Hardness

Reflects dissolved

carbonate minerals.

Mostly of concern for

drinking water

standards.

Metals precipitate out

of solution.

Create scale/hard

water deposits

High alkalinity Hard water

and Nitrate (NO3

-)

naturally-occurring

form of nitrogen

found in soil.

Forms by microbial

decomposition of

fertilizers, plants,

manures or other

organic residues

Plants uptake

nitrates (Spinach a

good source).

Phosphate (PO4-3)

naturally occurs in

rocks and minerals.

Plants uptake

weathered-out

elements and

compounds.

Animals ingest plants.

Water soluble.

Redfield Ratio: 106:16:1

Nitrates

The U.S. EPA has set a maximum

contaminant level for NO3- in drinking

water of 10 parts per million (ppm)

Artificial sources: Livestock manure/urine

Failing septic systems

Synthetic fertilizers

Can lead to: eutrophication of natural

water systems

(overproduction of

vegetation)

Blue baby syndromne

Artificial sources:

Sewage Laundry, cleaning fluids

Synthetic fertilizers

Can also lead to

eutrophication of

natural water

systems

(overproduction of

vegetation)

Phosphates

Blue green algae

1990 and 1999 comparison

of Nitrates in Great Lakes

From US EPA

http://www.epa.gov/glnpo/monitoring/limnology/SprNOx.html

Solutions??

Wetland restoration Reduce fertilizers

Reduce emissions WWTP/industry Reduce soil erosion

Turbidity

Measures how

murky the water is

Estimates:

Mineral fraction

Organics

Inorganics

Soluble organic compounds

Plankton

Microscopic organisms

MODIS Image from NASA

http://rapidfire.sci.gsfc.nasa.gov/

Causes of highly waters

In open waters, phytoplankton Closer to shore, particulates Resuspended bottom sediments

(wind)

Organic from stream and/or wastewater discharges.

Channelization Increased flow rates Too many bottom-feeding fish (such as carp)

Effects of highly waters

Modify light penetration Increase sedimentation rate Smother benthic habitats Settling clay particles Fine particulate material also can damage sensitive structures

Decrease organism resistance to disease Prevent proper egg and larval development Macrophyte growth may be decreased Reduced photosynthesis can lead to lower daytime release of oxygen

Conductivity Ability of a substance to conduct an electrical current.

In water, conductivity determined by types and quantities of dissolved

solids. (Commonly called Total Dissolved Solids = TDS)

Current carried by ions (negatively or

positively charged particles).

Eg: NaCl(aq) = Na + + Cl

Cl- Na+ Na+

Na+

Na+

Na+ Cl-

Cl-

Cl-

Cl-

Na+ Cl- Cl- Cl- Cl-

Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+

Cl- Cl- Cl- Cl-

Na+ Na+ Na+ Na+

Cl- Cl- Cl- Cl-

Na+ Na+ Na+ Na+

Cl- Cl- Cl- Cl-

Na+ Na+ Na+ Na+ Na+

Na+ Na+

Na+ Na+

Na+ Na+

Conductivity

Conductivity of natural waters depends upon:

Ion characteristics (mobility, valence, concentration)

Water temperature

Geology

Size of watershed

Evaporation

Some artificial factors that can affect conductivity:

Wastewater

Urban runoff (especially road salt)

Agricultural runoff

The most abundant components of a

kilogram of seawater.

The Components of Salinity