Quantification of Dissolved Natural Organic Matter (DOM) Mediated Phototransformation of Phenylurea Herbicides in Lakes

Abstract

For many important classes of pesticides including phenylurea herbicides (PUHs) and triazines, photosensitized transformation may be the only relevant elimination process in surface waters. In this study, the dissolved organic matter (DOM) mediated phototransformation of PUHs has been investigated in laboratory and field experiments. The results indicate that, in surface waters, the photosensitized transformation of PUHs may be significant and occurs primarily by an initial one-electron oxidation most likely involving excited triplet states of DOM (3DOM*) constituents. Using isoproturon and diuron as model compounds, it is shown that for a given DOM, quantum yield factors determined in the laboratory at a few selected wavelengths can be used to quantify the overall DOM- mediated phototransformation of a given PUH under sunlight irradiation. Furthermore, it is demonstrated that this process can be modeled for a given surface water, by applying the program GCSOLAR and a simple algorithm for cloud cover for quantification of average daily light intensities. Finally, the model has been successfully applied to predict vertical concentration profiles of isoproturon and diuron in a small lake in Switzerland. To our knowledge, this is the first study in which DOM-mediated phototransformation of organic pollutants has been quantitatively validated in the field.

Methylmercury Photodegradation in Surface Water of the Florida Everglades: Importance of Dissolved Organic Matter-Methylmercury Complexation

“…The results showed that MeHg compexed with DOM was dramatically decreased in the presence of NaN 3 . This finding suggested that 26,27 can also exist in the aquatic environments and be involved in the photodegradation of different pollutants in water.…”

Photochemical processes involving the UV absorber benzophenone-4 (2-hydroxy-4-methoxybenzophenone-5-sulphonic acid) in aqueous solution: Reaction pathways and implications for surface waters

“…However, concentrations involved are much higher than those found in environmental waters. Organic compounds that occur in aqueous environments can be transformed by a variety of abiotic and biological pathways, among which direct photochemistry and photogenerated reactive species such as hydroxyl radical ( • OH), carbonate radical (CO 3 •− ), singlet oxygen ( 1 O 2 ) and triplet states of Chromophoric Dissolved Organic Matter ( 3 CDOM*) (Mack and Bolton, 1999;Canonica et al, 1995 andCanonica and Freiburghaus, 2001;Gerecke et al, 2001;Boreen et al, 2003;Page et al, 2011). …”

Kinetics of phenylurea herbicides oxidation by Fenton and photo‐Fenton processes

“…10 They are used for a variety of purposes, 11 such as systemic herbicides (isoproturon and chlortoluron) to control broadleaf and grassy weeds in cereals and other crops, in cotton fields (linuron), as total herbicides in urban areas (diuron), and as algicides in paints and coatings (diuron). 12 They exhibit a high degree of biotoxicity, have a moderate to low solubility in water, and have received particular attention in recent years because of their toxicity and possible carcinogenic properties, requiring several weeks to months for their removal from the environment. 13 Moreover, diuron and isoproturon are considered The shortage of information in the literature about the chemical oxidation of this important group of pollutants promoted the design of a general research program for the study of the chemical degradation in aqueous solutions by several oxidation treatments of four selected herbicides of this group: linuron (L; 3-(3,4dichlorophenyl)-1-methoxy-1-methylurea), chlortoluron (C; 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea), diuron (D; 3-(3,4-dichlorophenyl)-1,1-dimethylurea), and isoproturon (I; 3-(4-isopropylphenyl)-1-1-dimethylurea).…”