Pesticide removal in constructed wetlands is controlled by a variety of factors:
- the physico-chemical characteristics of the compound itself – basically predictors of how the chemical will move in the environment. Will it stay in water? Will it bind with sediments?
- processes within constructed wetlands themselves that remove pesticides – sedimentation, microbial degradation, other chemical-reaction based degradation processes (e.g. breakdown by light), and plant uptake
- site specific factors – organic matter, pH, clay content, hydraulic retention time, plant presence (yes/no), flow conditions (intermittent vs. permanently flooded)
Some trends exist with regard to removal efficacy in constructed wetlands:
- High removal (84-97% removal efficacy): Organochlorines (e.g. endosulfan and pentachlorophenol), strobilurin/strobin (e.g. azoxystrobin, trifloxystrobin), organophosphates (e.g. chlorpyrifos, dimethoate, glufosinate, and parathion), and pyrethroids (e.g. bifenthrin, cyhalothrin, cypermethrin, esfenvalerate, and permethrin). These groups have low water solubility.
- Low removal (24 – 50% removal efficacy): triazinone (e.g. metribuzin), aryloxyalkanoic acid groups (e.g. dichlorprop, MCPA, mecoprop), and urea-based pesticides (e.g. diuron, linuron). Water solubility is variable and does not help to predict remediation efficacy.
Predicting whether constructed wetlands will effectively remediate the pesticides of concern to you is a challenging process – and highly technical. Please consult with Dr. Sarah White (firstname.lastname@example.org) if you want additional information about this topic.