Groundwater Pollution Week 04 – Types of Pollution 2

Contaminants are separated into four main categories: Physical Biological Inorganic chemicals Organic chemicals

These categories may overlap sometimes. eg a biological organism might make organic chemicals and the organisms have a physical effect on the water.

Contaminants can have effects at very small concentrations. Measure amounts of contaminants in terms of concentration. ppm and ppb and ppt, which are parts per million and parts per billion and parts per trillion. PPM is the amount of contaminant units in 1,000,000 (1 million) units of groundwater. PPB is lthe amount of contaminant units in 1,000,000,000 (1 billion) units of groundwater. PPT is the amount of contaminant units in 1,000,000,000,000 (1 trillion) units of groundwater.

ContaminationBasics1.htm

Very small concentrations of some groundwater contaminants could have serious health effects. Different kinds of contaminants have different concentration limits. It is necessary to find out both the specific type of contaminant and the concentration of the contaminant.

ContaminationBasics3.htm

Contamination Movement As contamination moves it disperses. The concentration decreases as it moves farther away from the source of the pollution. So there are different concentrations of contaminants at different points in the aquifer.

The representation of these different concentrations is called a contamination plume. ntaminationMovement.htm

Area of Contamination A contaminant may be released into the groundwater for only a short time and in a very small area, but as it disperses the contaminant can affect a very large area and number of people. aofContamination.htm

Plumes can be very irregular

ule04/PlumeExample.htm Watch and say: Where is the source of the contamination? Is the source continuous or a one-time event? Based on the direction of the plume, which way is the groundwater moving? How far does the contamination travel in 16 years? What important areas of the city are affected by the contamination?

Finding Contaminants Look at the history of the site. See if a nearby river is contaminated or what possible above-surface sources exists. To find the contaminant plume drill test wells or use other technology to find concentrations at different points underground. meSourceGame.htm

Some specific contaminants.

Sites to search for contaminants in.org/contaminantfocus/default.focus/sec/ General_Contaminant_Information/cat/Ov erview/ has a large list of sites, including ic/entry.cfm

Suspended Solids Organic and inorganic particles in water are termed suspended solids May be distinguished from colloids, particles that do not settle readily Measured by filtering a water sample, drying and weighing the filter

Suspended Solids Problems –sedimentation –may exert oxygen demand –primary transport mechanism for many metals, organics and pathogens –aesthetic –complicates drinking water treatment Sources –storm water –wastes –erosion

Pathogenic Organisms Many organims that cause human or animal diseases colonize the instinal tract but can live for a period of time outside the body Carriers (who may or may not exhibit disease symptoms) excrete these intestinal tract organims in very large numbers When water is contaminated by excretia, the organisms can be transmitted to those who contact the water

Pathogenic Organisms

Toxic and Hazardous Substances Volatile organic compounds Hydrophobic organic compounds Endocrine disruptors Surfactants Petroleum Additives Pesticides Heavy metals Other inorganic elements Acids/bases Oxidants/reductants Chlorination by- products Combustion by- products

Volatile Organic Compounds Petroleum constituents: –benzene and substituted benzenes –prevalent in gasoline, diesel fuel, heating oil –most easily transported, slow degradation, toxic

Volatile Organic Compounds Oxygentated gasoline additives –added to gasoline to improve air quality –very soluble, resistant to degradation, toxic –attempt to solve one problem caused another (spills) Methyl tertiary butyl ether (MTBE)

Volatile Organic Compounds Chlorinated solvents –C1 and C2 aliphatics –widely used in degreasing, dry cleaning, extraction –somewhat soluble, volatile, difficult to degrade

Hydrophobic Organic Compounds Polycyclic aromatic hydrocarbons (PAHs) –potent carcinogens, tend to associate with particles –also combustion by-products

Hydrophobic Organics/ Chlorinated Aromatics Chlorinated Pesticides Polychlorinated dibenzodioxins (PCDDs) Polychlorinated biphenyls (PCBs)

Some Other Categories Trihalomethanes Explosives and Propellants Phenolics Aldehydes Organometallics Asbestos

Arsenic Occurs naturally in rock and soil Released to groundwater under some conditions Health effects include cardiovascular diseases, skin cancer, nervous system effects, and kidney disease Major problem in Bangladesh Drinking water standard being lowered in U.S.