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Pesticide and nitrate contamination of soil and groundwater from agriculture is an environmental and public health concern worldwide. The herbicide terbuthylazine (CBET) has replaced atrazine in Italy and in many other countries because the use of the latter has been banned because of its adverse environmental impacts. Unlike atrazine, knowledge about the fate of CBET in soil is still not extensive, especially regarding its transformation products, but recent monitoring data show its occurrence and that of its main metabolite, desethyl-terbuthylazine (CBAT), in groundwater above the limit of 0.1 microg/L established by European Union Directive and Italian legislation. The objective of this work was to investigate if the presence of the fertilizer urea affects CBET degradation in the soil. Laboratory CBET degradation experiments in the presence/absence of urea were performed with microbiologically active soil and sterilized soil. Terbuthylazine degradation rates under the different experimental conditions were assessed, and the formation, degradation, and transformation of the metabolite CBAT were also studied. Terbuthylazine degradation was affected by the presence of urea, in terms both of a higher disappearance time of 50% of the initial concentration and of a lower amount of CBAT formed. These findings have practical implications for the real-life assessment of the environmental fate of triazine herbicides in agricultural areas since these herbicides are frequently applied to soils receiving ureic fertilizers.

Due to the great potential of atrazine in contaminating groundwater, its use has been banned in several countries and often replaced by terbuthylazine (CBET). Little is known on the fate of CBET in soil. The purpose of this work has been (1) to develop a general method for analysing CBET and its degradation products (DPs) in soil and (2) to use this method for elucidating the fate of CBET incubated in both surface and subsurface samples of an agricultural soil which had been receiving repeated CBET spills. This method involves analyte extraction from soil at 100 degrees C by phosphate-buffered water. Analytes coming out of the extraction cell were collected by a graphitized carbon black extraction cartridge. After analyte elution with a suitable solvent mixture, the final extract was analyzed by LC-MS. From an aged soil, our method extracted altogether quantities of CBET and its DPs respectively 2.1 and 1.4 times larger than those by two previously reported methods. For the analytes considered, limits of quantification (S/N 10) ranged between 0.22 and 5.5 ng per gram of soil. The laboratory CBET degradation experiment showed that (1) similarly to atrazine, remarkable amounts of hydroxylated metabolites were formed; (2) when the subsoil microflora was in the presence of rather large amounts of CBET, it degraded the herbicide with a rate similar to that of the topsoil microflora