Comprehensive analysis of degradation and accumulation of ametryn in soils and in wheat, maize, ryegrass and alfalfa plants.

Ametryn is a selective herbicide belonging to the triazine family and widely used for killing annual grasses or weeds in China and other parts of the world. However, reports on its environmental risk assessment with regard to soil and crop contamination are limited. In this study, accumulation of ametryn in wheat, maize, ryegrass and alfalfa crops along with ametryn residues in the soil planted with the plants were comparatively investigated. Soil enzyme activities and low molecular weight organic acids (LMWOAs), as well as antioxidant and degradation enzyme activities in plant tissues were measured. The maximum accumulation of ametryn was found in shoots and roots of wheat and alfalfa. Ryegrass had the maximum ametryn translocation factor (TF) from roots to shoots, with more than three times over the other crops. The ametryn residue in ryegrass-planted soil was much lower than that in soil planted with others. The residual content of ametryn in crop-planted soils was ordered as rhizosphere soil<bulk soil<non-rhizosphere soil<control (without plants). Activities of catalase (CAT), glutathione S-transferase (GST) and laccase (LAC) in ametryn-exposed ryegrass were significant higher than those in non-ametryn exposed ryegrass. The maximum activities of CAT in ryegrass shoot and root were increased by 6.16- and 28.84-fold over the control, respectively. Exudation of organic acids in the crop was induced by ametryn and contributed a lot to the degradation of the herbicide. Thus, ryegrass was shown to have a relatively strong ability to remove ametryn from ametryn-contaminated soil and its plant tissues as well.