Predicting Disaster:

Model Ecosystems and the Prevention of Water Pollution

Partial List of Ecologically Harmful Chemicals

• Persistent and bioaccumulative:– DDT and its congeners– Cycodienes

• Aldrin & Dieldrin• Endrin• Heptachlor & Chlordane• Mirex & Chlordecone (Kepone)

– PCBs – PBBs– PFOS & PFOA– Cadmium– Selenium– Organic mercury compounds– Organic tin compounds– Hexachlorobenzene

• Persistent but not bioaccumulative:– Aldicarb– Lead– DES

• Unduly Toxic– Fenthion– Parathion– Compound 1040

• Endocrine disruptors– Vinclozolin– Phthalates– Atrazine?– ….. etc

Preventing Ecological Disasters

• Statement of the problem:– Complex ecosystems– Many chemicals – Ecological consequences take time to show up– Chemicals cannot be retrieved from environment

• Metcalf Microcosm:– Predicts environmental behavior– Validated

• 150 chemicals• Many with field experience

Metcalf Microcosm

• Environment– 10 gallon aquarium– Sterile sand, 15 kg– Standard reference water, 8L– 10 ml aquarium water

• Organisms– Sorghum vulgare– Daphnia magnum– Snails (Physa spp)– Algae (Oedegonium

cardiacum)– Mosquito larvae (Culex

pipiens) – Mosquito fish (Gambusia

affinis)

• Preparation: – Water, sand– Plant sorghum– 8 snails– 100 Daphnia– Algae

• Day 0 – Sorghum is 3-5 cm tall– Treat plants (or sand)– Wait 1/2 hour

• Day 5– Add caterpillars

• Day 26– Add 300 mosquito larvae

• Day 29– Add 3 mosquitofish

• Day 32– Terminate system

• Analysis– Measure 14C in all organisms,

water, sand

Tradeoffs in Designing Model Ecosystems• Microcosm

– Advantages• Cheap• Fast• Repeatable

– Disadvantages• Unrealistic?• Tests 1 or 2 parameters

– Which?

• Mesocosms– Vary tremendously– With increasing size

• Complexity increases– More variables included– More parameters tested

• Costs increase• Time to completion increases• Reproducibility decreases

Mesocosms

Water, Soil and Air Interconnect

Fields, parking lots,Roofs, roads

bubbles

Wells - private & public

Municipal water sources

Adsorption on solids; Absorption of gases

Water, Air and Soil as Media for Pollutants