Characterization of the Atrazine's Bound (Nonextractable) Residues Using Fractionation Techniques for Soil Organic Matter

Abstract

Atrazine's bound residues (BR), in the range of 10-40% of the applied atrazine,were obtained by laboratory incubation (56 d) of four soils having different capacities to degrade atrazine in relation to the presence or absence of a microflora able to mineralize the triazinic ring. Soil size fractionation followed by alkaline extraction, before and after HF treatment, and then acid hydrolysis with 2 M HCl in reflux conditions was applied to the soils containing BR. Most of the BR were in the finest fraction (<20 microm) that contained the humified organic matter (from 61 to 77% of the total BR), and between 78 and 89% was made soluble during the different steps of the chemical fractionation procedure. From 20 to 50% of the BR of the fraction <20 microm was identified as the intact atrazine and its main derivatives, indicating that this proportion of the BR was probably formed by entrapment in voids of the soil organic matter. Between 13 and 30% of the BR was associated to humic acids (HA); they were not dialyzable and were released by acid hydrolysis with HCl, indicating that these BR were chemically bound to HA by an heteroatomic bond after the substitution of the chlorine atom of atrazine. Comparison of the results obtained for the four soils indicated that (i) an important activity of microorganisms able to mineralize the triazinic ring favors the formation of highly degraded products that can form BR; (ii) a soil pH <6 favors the formation and stabilization of hydroxylated derivatives of atrazine, and (iii) a high content of humic acids favors the formation of chemically bound residues.

Bioaccessibility of Environmentally Aged 14C-Atrazine Residues in an Agriculturally Used Soil and Its Particle-Size Aggregates

“…The reason for atrazine in ground water is due to direct leaching, surface run-off or intrusion via particle binding. A continuous desorption and resulting mobility of atrazine in soils is also under discussion, with focus on the formation of "bound residues" (9 ). Degradation and metabolism of atrazine in soil occurs through microbial activity and non-biotic processes, such as hydrolysis, photo-degradation and oxidation, leading simultaneously to the formation of bound residues (10 ).…”

“…Numerous investigations have stated that the distribution of atrazine residues in soil is mainly dependent on the soil organic carbon (e.g. humin, humic and fulvic acids) (15 ) and the clay content (16 ), with the majority of the atrazine residues are located in soil particle fractions <20µm (9 ).…”

Sorption of atrazine, propazine, deethylatrazine, deisopropylatrazine and hydroxyatrazine onto organovermiculite

“…Because of the large use of atrazine (AT) to control annual grasses and broad-leaved weeds in several crops, in roadside verges and golf courses, intense research has been performed to investigate its environmental impacts. [2][3][4][5][6] Several authors have reported the presence of AT and its metabolites in surface and ground waters, as well as other s-triazines such as simazine, ametryne and propazine. 7 Although the presence of AT metabolites is indicative of herbicide degradation, some of them, especially deethylatrazine (DEA) and deisopropylatrazine (DIA), have similar toxicity, greater water solubility and weaker interaction with soil components than the parent herbicide.…”

Incorporation of pesticides by soil micro-organisms as a way of bound residues formation

“…For instance, using degradative techniques such as pyrolysis and chemical hydrolysis, and pesticides labelled with 13 C or 15 N, Guthrie et al (1999), Loiseau et al (2000), Loiseau and Barriuso (2002), and Dignac et al (2003) showed a partial release of bound residues. Their results showed that a major part of bound residues were compounds of chemical structure similar to that of the parent compound.…”