Fate and Transport Analyses

 

The objective of fate and transport analyses is to identify how chemicals degrade and where chemicals travel in the environment when they are intentionally or unintentionally released (US Department of Energy). Fate and transport analyses describe how a chemical moves through the environment—air, water and soil—as well as how it changes in the presence of other chemicals and substances.

 

Technical fact sheets on the most commonly used chemicals to control dreissenids can be found in (Appendix B). Technical fact sheets provide information on the chemical class and type, uses, physical and chemical properties, mode of action, non-target organisms, acute toxicity, chronic toxicity, endocrine disruption, carcinogenicity, reproductive and developmental effects, fate in the body, medical tests and monitoring, environmental fate, ecotoxicity studies, and regulatory guidelines. While these studies base effects on populations, the Endangered Species Act is concerned with effects to individual organisms.

 

Copper-based products

Copper-based algaecides are lethal to all life stages of dreissenids, but are also lethal to many other aquatic species. Their efficacy increases with increasing ambient temperatures. Cooper sulfate is an algaecide, bactericide and fungicide, and is one of the most effective chemicals used to control dreissenids in a closed water body. Copper sulfate disrupts the surface epithelia function and enzymes in mussels in all life history stages of mussel, but has a proven efficiency of 50–99% for adult dreissenids (0. 5mg/l copper equivalent with 96 hours of exposure). Its toxicity to fish and other aquatic organisms depends on pH, dissolved organic carbon levels, and other water chemistry parameter, such as calcium. Copper sulfate, however, is highly toxic to salmonids (Griffin and Strauss 2000).

 

Extensive fate and transport analyses have been conducted on copper sulfate (Appendix B). Three processes control the fate of copper in the environment: transport to lower soil levels by groundwater percolation; binding to soil components; and breakdown into metabolites (Hartley and Kidd 1983). Copper is bound, or adbsorbed to organic materials, and to clay and mineral surfaces, depending on the level of acidity or alkalinity of the soil. The distance copper travels in soil is limited by its strong adsorption to many types of surfaces. Copper sulfate is highly water soluble, but the copper ions are strongly adsorbed or precipitated to soil particles (Extoxnet 1996).

 

The following summarizes fate and transport analyses on copper sulfate (Siemering and Hayworth 2005):

  • Mechanism of Toxicity—Photosynthesis and cell growth inhibitor.
  • Solubility—230,550ppm at 25 degrees Celcius (anhydrous)
  • Fate—Highly water soluble with no degradation. Strong particle and dissolved oxygen concentration affinity causes rapid sediment deposition. Transport occurs between water and sediment (advection/flux).
  • Confounding Factors—Toxicity is temperature, pH, and hardness dependent, with greater toxicity in softer water. Bioavailability is influenced by sorption to dissolved oxygen concentration and particles.
  • Data Gaps—Toxic effects on embryos and larvae, and chronic effects to benthic invertebrates.

Environmental Fate (National Pesticide Information Center):

 

Soil

Copper sulfate can dissociate or dissolve in the environment releasing copper ions. This process is affected by its solubility, which in turn is affected by pH, redox potential, dissolved organic carbon, and ligands present in the soil. Copper in soil may originate from natural sources, pesticides, and other anthropogenic sources such as mining, industry, architectural material, and motor vehicles. Copper accumulates mainly at the surface of soils and it can persist because it has a tendency to bind to organic matter, minerals, and some metal oxides. It may leach from acidic or sandy soil. The more acidic the soil, less binding occurs. Irrigation water treated with copper sulfate as an algaecide could lead to soil levels that could damage crops. The presence of calcium ions decreases leaching of copper, increasing its binding capacity. The presence of sodium ions has the opposite effect and causes more copper to leach.

 

Water

Copper sulfate is an inorganic salt that is highly soluble in water. The disassociated copper ions mainly bind to organic matter or remain dissolved in water. When applied to channel catfish ponds over 16 weeks, 90% of the copper in copper sulfate pentahydrate was bound to the sediments within minutes of application and 99% of it was bound after 2 days. Nearly all of the copper remained in the top 16 cm of sediment. After applying 2,250 kg copper sulfate to a lake in California, researchers noted that 20% of the applied copper left the reservoir by day 70 and most of the remaining copper became bound in the upper layer of the sediment.

 

Air

No data were found regarding the fate of copper sulfate in the atmosphere.

 

Plants

Copper is an essential mineral for plant growth and its concentration is regulated by homeostatic mechanisms. However, copper can be toxic to plants by affecting electron transport in photosynthesis. Bioavailability depends on the amount of copper, soil pH, organic carbon, precipitation, and temperature. Readily soluble copper is the most phytotoxic form, and can inhibit growth of plants, such as onion (Allium cepa) bulbs and garden cress (Lepidium sativum) seeds by as much as 50% within 48 hours of exposure.

 

Ecotoxicity Studies

 

Birds

The U.S. EPA classified copper as moderately toxic to birds based on the acute oral LD50 for bobwhite quail (Colinus virginianus) of 384 mg/kg copper sulfate pentahydrate and 98 mg/kg metallic copper. Bobwhite quail feed copper sulfate for 21 days fed less and gained less weight. Then birds in a flock of captive 3-week-old Canada geese (Branta canadensis) that used a pond treated with copper sulfate died nine hours after ingestion of about 600 mg/kg copper sulfate. Limited data are available regarding copper sulfate toxicity to wild birds.

 

Fish and Aquatic Life

The toxicity of copper to fish and other aquatic life depends on its bioavailability, which is strongly dependent on pH, the presence of dissolved organic carbon (DOC), and water chemistry such as the presence of calcium ions. Fish kills have been reported after copper sulfate applications for algae control in ponds and lakes. However, oxygen depletion and dead organisms clogging the gills have been cited as the cause of fish deaths, resulting from massive and sudden plant death and decomposition in the water body.

  • Researchers exposed juvenile rainbow trout (Oncorhynchus mykiss) to either hard water or soft water spiked with copper for 30 days. Fish in the hard-water, high dose (60 µg/L) treatment groups showed an increased sensitivity to copper.
  • The mean 96-hour LC50 (with 95% confidence limits) for copper exposure in alevin, swim-up, parr and smolt steelhead (Salmo gairdneri) are 28 (27-30), 17 (15-19), 18 (15-22), and 29 (>20) µg/L of copper respectively. The mean 96-hour LC50 for copper exposure in alevin, swim-up, parr and smolt Chinook salmon (Oncorhynchus tshawytscha) are 26 (24-33), 19 (18-21), 38 (35-44), and 26 (23-35) µg/L of copper respectively. The experiments were done by adding copper as CuCl2.
  • Copper sulfate is toxic to shrimp due to damage of the gill epithelium and respiration disruption. Copper also disrupts olfaction in fish, possibly interfering with their ability to locate food, predators, and spawning streams
  • The toxicity of copper sulfate to blue tilapia (Oreochromis aureus) fingerlings was found to increase with the decrease in total alkalinity.
  • Researchers studied the effect of sediment on copper toxicity in three Daphnia species, similis, D. magna, and D. laevis. They reported that the toxicity is reduced in the presence of sediments because bioavailability of copper is decreased.
  • Researchers exposed 1-day-old freshwater snail eggs (Lymnaea luteda) to copper at concentrations from 1 to 320 µg/L of copper for 14 days at 21 °C in a semi-static embryo toxicity test. Embryos exposed to copper at 100 to 320 µg/L died within 168 hours. At lower doses from 3.2-10 µg/L, significant delays in hatching and increased mortality were noted.
  • Researchers reported no observed effects concentrations (NOEC) of 8.2-103 mg/L copper in the freshwater rotifer (Brachionus calyciflorus). Toxicity increased with decreasing levels of DOC and decreasing pH.
Terrestrial Invertebrates

The U.S. EPA considers copper to be practically nontoxic to bees.