5g

pollution

• soil is considered polluted when the contaminant limits the soil’s natural function

types of pollution

• chemicals - pesticides, fertilizers

• inorganic toxins: mercury, cadmium, lead

• organic wastes, ag, indusry

• salts - nontoxic materials

• radioactive materials

evaluating the pollution potential

• is it an immediate danger to people and the environment

• what kind of material

  • organic or inorganic

  • biodegrade

  • dangerous?

• how much added to soil

• -

• -

• what kind of soil is it?

• what are the growing conditions

• how long has the material been on site

organic contaminants

• organic compounds, including industrial compounds and pesticides

• the longer a contaminant persists, the greater risk for groundwater contamination.

remediation - organic contaminants

natural attenuation

• many ecosystems eventaually recover, takes the longest

microbial bioremediation

• uses soil microbes to break down and remove contaminants

• happens in-situ

• most bioremediation happens with microbes already in the soil

• bioaugmentation - inoculating the soil with microbes known for contaminant removal

• biostimulation

  • conditions are optimized for maximum microbial activity

phytoremediation

• utilizes plants in the removal or breakdown of inorganic and organic toxins

• hyperaccumulators - plants that have a special ability to remove large amounts of contaminants

removal and containment

• soil is excavated, moved off site, and stored in a sealed landfill

• pro: fast

• con: expensive

soil washing or incineration

• organic pollutants are “burned off” and material is put back to where it was

• pro: fast

• con: expensive, soil is dead (sterile)

remediation - inorganic contaminants

inorganic contaminants

• mostly metals

  • Hg, Cd, Pb, As, Ni, Cu, Zn, Cr, Mo, Mn, Se F, B

• sources

  • fossil fuels

  • paint

  • smelting

  • pesticides

  • land application of sewage sludge

remediating inorganic contaminants

• three options

  • eliminate or drastically reduce application of the toxin

  • immobilize the toxin by means of soil management

immobilization

• acidity

  • most metals are most soluble at low pH

  • raising pH increases whats absorbed

  • when in doubt, add lime

• oxidation

phytoremediation

• removing metals by harvesting aboveground biomass

brownfields

• areas of land in which further development is limited due to existing contamination

• land needs remediation, but who is going to pay?

soil pollution topics - LUSTs

• leaking underground storage tanks

• metal tanks stored below ground

• can rust and leak

• out of sight out of mind