Contamination Profile

a potential contamination that prompts subsurface assessments is either ____ or to a lesser degree ______

chemical

lesser degree - microbial

5 general categories of constituents (components) of interest

1. inorganics (non heavy metals)

2. inorganics (heavy metals)

3. gases

4. organics

5. microbiological/pathogens (biohazards)

examples of inorganics (non heavy metals) contaminants

calcium, sulphate, iron

examples of inorganics (heavy metals) contaminants

arsenic, mercury, lead, cadmium

examples of gaseous contaminants

methane, hydrogen sulfide

examples of organics contaminants

Volatile Organic compounds (VGO)

Semi Volatile organic compounds (SVOC)

non volatile organic compounds

examples of microbiological contaminants

bacterial, viral, human cadavers

five physical phases contaminants can be found in the subsurface

1. solid grains, rocks or waste solids

2. ions or molecules of solids weakly bound to soils

3. gas or vapor in pore spaces in unsaturated soils

4. liquids dissolved in water

5. non-aqueous phase liquids

NAPL

non-aqueous phase liquids

what is true of contaminants in mobile phases (water, vapours, NAPL)

can migrate

contaminants from immobile phases can ________ slowly overtime

contaminant subsurface water

adsorption vs absorption

Adsorption - molecules stick to the surface of a material, like dust on a table

absorption - molecules are taken into the volume of another substance (sponge)

typical sources of groundwater contamination

• vapours that can dissolve in groundwater

• solids that produce undersirable dissolved compounds

• chemicals adsorbed onto solid surfaces

• pools of NAPLs

LNAPL vs DNAPL vs NAPL residuals

LNAPL

• lighter than water

• specific gravity less than 1.00

• hydrocarbons and aromatic solvents

DNAPL

• heavier than water

• specific gravity more than 1.00

• penetrates deep below water table

NAPL residuals

• immobile

• form solids

non aqueous

not readily miscible with water

where do LNAPL and DNAPL tend to collect

LNAPL - small pools suspended on top of ground water aquifer

DNAPL - small pools suspended at the bottom of ground water aquifer

best known pesticide

DDT

pesticide characteristics

• cyclic

• chirality centers

• lots of substituents

what are NAPLs always associated with

human activities

what does NAPLs cause

severe environmental and health hazards

is it possible to remove all the NAPLs once released

NO

BTEX plume

highly mobile volatile organic compounds (VOCs) that contaminate groundwater, typically from gasoline spills

what does BTEX stand for

Benzene, Toluene, Ethylbenzene, and Xylenes