Role of Vegetation in a Constructed Wetland on Nutrient–Pesticide Mixture Toxicity to Hyalella azteca
- 132 Downloads
The toxicity of a nutrient–pesticide mixture in nonvegetated and vegetated sections of a constructed wetland (882 m2 each) was assessed using Hyalella azteca 48-h aqueous whole-effluent toxicity bioassays. Both sections were amended with a mixture of sodium nitrate, triple superphosphate, diazinon, and permethrin simulating storm-event agricultural runoff. Aqueous samples were collected at inflow, middle, and outflow points within each section 5 h, 24 h, 72 h, 7 days, 14 days, and 21 days postamendment. Nutrients and pesticides were detected throughout both wetland sections with concentrations longitudinally decreasing more in vegetated than nonvegetated section within 24 h. Survival effluent dilution point estimates—NOECs, LOECs, and LC50s—indicated greatest differences in toxicity between nonvegetated and vegetated sections at 5 h. Associations of nutrient and pesticide concentrations with NOECs indicated that earlier toxicity (5–72 h) was from permethrin and diazinon, whereas later toxicity (7–21 days) was primarily from diazinon. Nutrient–pesticide mixture concentration–response assessment using toxic unit models indicated that H. azteca toxicity was due primarily to the pesticides diazinon and permethrin. Results show that the effects of vegetation versus no vegetation on nutrient–pesticide mixture toxicity are not evident after 5 h and a 21-day retention time is necessary to improve H. azteca survival to ≥90% in constructed wetlands of this size.
The authors wish to thank Lisa Brooks, James Hill, and Renee Russell for analytical assistance. Mention of equipment, computer programs, or a pesticide neither constitutes an endorsement for use by the US Department of Agriculture nor does it imply pesticide registration under FIFRA as amended. All programs and services of the USDA are offered on a nondiscriminatory basis without regard to race, color, national origin, sex, marital status, or handicap.
- APHA (American Public Health Association) (2005) Standard methods for the examination of water and wastewater, 21st edn. APHA, Washington, DCGoogle Scholar
- US Census Bureau (2009) US & world population clocks. US Census Bureau, Population Division. http://www.census.gov/main/www/popclock.html
- FAO (Food and Agriculture Organization of the United Nations) (2009) FAO Statistical database, FAOSTAT. http://faostat.fao.org/site/575/default.aspx#ancor
- Scheffer M (2004) Ecology of shallow lakes. Kluwer Academic, DordrechtGoogle Scholar
- Schulz R, Moore MT, Bennett ER, Milam CD, Bouldin JL, Farris JL, Smith S Jr, Cooper CM (2003) Acute toxicity of methyl-parathion in wetland mesocosms: assessing the influence of aquatic plants using laboratory testing with Hyalella azteca. Arch Environ Contam Toxicol 45:331–336. doi: 10.1007/s00244-003-2170-2 CrossRefGoogle Scholar
- Smith S Jr, Cooper CM (2004) Pesticides in shallow groundwater and lake water in the Mississippi Delta MSEA. In: Nett M, Locke M, Pennington D (eds) Water quality assessments in the Mississippi Delta: regional solutions, national scope. ACS Symposium Series, vol 877. American Chemical Society, Oxford University Press, Chicago, p 91Google Scholar
- USEPA (US Environmental Protection Agency) (2000) Methods for measuring the toxicity and bioaccumulation of sediment-associated contaminants with freshwater invertebrates. EPA 600/R-99/064. EPA, Washington, DCGoogle Scholar
- Yu SJ (2008) The toxicology and biochemistry of insecticides. CRC Press, Boca RatonGoogle Scholar