The role of organic colloids in herbicide transfer to rivers: a quantitative study of triazine and phenylurea interactions with colloids

Abstract

For moderately hydrophobic compounds such as most pesticides adsorption on colloids (<0.2 microm) may play a key role in pesticide mobility as well as in their degradation by chemical and microbiological processes. However, until now, pesticide-organic colloid interactions are poorly understood. Quantitative data for sorption equilibria on colloids of two series of herbicides including triazines (atrazine, simazine, terbutylazine, prometryne, desethylatrazine, and desisopropylatrazine) and phenylureas (isoproturon, linuron, neburon, and diuron) sampled in the Seine river (urban zone) and the Marne river (agricultural zone) are presented. Partition coefficient of herbicides on colloids (K(com)), were evaluated by solid-phase extraction coupled with high-performance liquid chromatography-UV diode-array detection (SPE-HPLC-UV/DAD). In the case of triazines a satisfactory log-log correlation was found between K(com) and octanol-water coefficient (K(ow)) values. Phenylureas did not obey this correlation, with K(com) values being about two times higher than those of triazines. The existence of two distinct types of adsorption behaviour on colloids partly explains the different occurrence of triazines and phenylureas in surface waters.

What happens when pharmaceuticals meet colloids

“…2) (Flury and Qiu 2008). Besides, colloid-facilitated transport has been widely studied for many pollutants, such as heavy metals (Mills et al 1991;Grolimund and Borkovec 2005) and pesticides (Sojitra et al 1995;Sprague et al 2000;Irace-Guigand and Aaron 2003).…”

Aerobic microbial transformation of pesticides in surface water

“…12,13) The dilution factor is also estimated by hydrodynamic models 14) or monitoring the concentration of a tracer (Cl − ) in a water system. 15,16) Depending on its physicochemical properties, pesticide is partly adsorbed or associated with suspended particles, colloids, and dissolved organic matters (DOM), 4,17,18) reaches bottom sediment via sedimentation or diffusion, 17,19) and escapes from the water body via volatilization. 4,14) The sorption of pesticides is evaluated by an adsorption coefficient determined in a batch study, generally assuming a linear or Freundlich isotherm.…”

“…23) Algae and protozoa can absorb and metabolize pesticides, 24) but bacteria and fungi contribute more to pesticide dissipation through their ubiquity. 3,8,18) Bacteria are more diversely populated, with their activity depending on the habitat, 25) while fungi tend to grow on a substratum, such as detritus, rather than in water. 26,27) Bacteria metabolize pesticides via various enzymatic reactions, 28) and extra-cellular enzymes such as laccases, 29) may participate in their fungal degradation.…”

“…4) In contrast, either lack of microbes having relevant enzymes or steric hindrance posed by a bulky cyclohexyl moiety resulted in insignificant degradation of fenhexamid (18). 98) The different amide reactivity by conjugation with the bulky alkenyl moiety might cause insignificant biodegradation of flumorph (19).…”

On-line coupling of microporous membrane liquid?liquid extraction and gas chromatography in the analysis of organic pollutants in water

“…Automation of LLE is possible but it requires robots and the procedures are typically off-line leading to possible analyte loss and contamination. Because of these drawbacks more environmentally friendly methods are continuously being searched for and LLE has been increasingly replaced by solid-phase extraction (SPE) [4,5].…”