Dissipation of S-metolachlor in plant and soil and effect on enzymatic activities

Environmental Monitoring and Assessment, Jun 2017

The present study aimed at evaluating the dissipation of S-metolachlor (S-MET) at three doses in maize growing on diverse physico-chemical properties of soil. The effect of herbicide on dehydrogenase (DHA) and acid phosphatase (ACP) activity was estimated. A modified QuEChERS method using LC-MS/MS has been developed. The limit of quantification (0.001 mg kg−1) and detection (0.0005 mg kg−1) were very low for soil and maize samples. The mean recoveries and RSDs for the six spiked levels (0.001–0.5 mg kg−1) were 91.3 and 5.8%. The biggest differences in concentration of S-MET in maize were observed between the 28th and 63rd days. The dissipation of S-MET in the alkaline soil was the slowest between the 2nd and 7th days, and in the acidic soil between the 5th and 11th days. DT50 of S-MET calculated according to the first-order kinetics model was 11.1–14.7 days (soil) and 9.6–13.9 days (maize). The enzymatic activity of soil was higher in the acidic environment. One observed the significant positive correlation of ACP with pH of soil and contents of potassium and magnesium and negative with contents of phosphorus and organic carbon. The results indicated that at harvest time, the residues of S-MET in maize were well below the safety limit for maize. The findings of this study will foster the research on main parameters influencing the dissipation in maize ecosystems.

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Dissipation of S-metolachlor in plant and soil and effect on enzymatic activities

Environ Monit Assess Dissipation of S-metolachlor in plant and soil and effect on enzymatic activities Elżbieta Wołejko 0 1 2 Piotr Kaczyński 0 1 2 Bożena Łozowicka 0 1 2 Urszula Wydro 0 1 2 Andrzej Borusiewicz 0 1 2 Izabela Hrynko 0 1 2 Rafał Konecki 0 1 2 Krystyna Snarska 0 1 2 Dorota Dec 0 1 2 Paweł Malinowski 0 1 2 0 P. Malinowski Division of Statistics and Medical Informatics, Medical University of Bialystok , Szpitalna 37, Białystok , Poland 1 D. Dec Division of Agrifood and Forestry Engineering, Białystok University of Technology , Wiejska 45 E, 15-351 Białystok , Poland 2 E. Wołejko ( The present study aimed at evaluating the dissipation of S-metolachlor (S-MET) at three doses in maize growing on diverse physico-chemical properties of soil. The effect of herbicide on dehydrogenase (DHA) and acid phosphatase (ACP) activity was estimated. A modified QuEChERS method using LC-MS/MS has b e e n d e v e l o p e d . T h e l i m i t o f q u a n t i f i c a t i o n (0.001 mg kg−1) and detection (0.0005 mg kg−1) were very low for soil and maize samples. The mean recoveries and RSDs for the six spiked levels (0.0010.5 mg kg−1) were 91.3 and 5.8%. The biggest differences in concentration of S-MET in maize were observed between the 28th and 63rd days. The dissipation of S-MET in the alkaline soil was the slowest between the 2nd and 7th days, and in the acidic soil between the 5th and 11th days. DT50 of S-MET calculated according to the first-order kinetics model was 11.1-14.7 days (soil) and 9.6-13.9 days (maize). The enzymatic activity of soil was higher in the acidic environment. One observed the significant positive correlation of ACP with pH of soil and contents of potassium and magnesium and negative with contents of phosphorus and organic carbon. The results indicated that at harvest time, the residues of S-MET in maize were well below the safety limit for maize. The findings of this study will foster the research on main parameters influencing the dissipation in maize ecosystems. S-Metolachlor; Dissipation; Soil; Maize; Acid phosphatase; Alkaline phosphatase; Dehydrogenase Introduction Maize (Zea mays L.) has high adaptive abilities and produces high fresh weight yields. Due to its cultivation in monoculture, more and more frequently, it decreases its yields owing to weed infestation, which at the early stages of growth competes with maize for nutrients and water (Sun et al. 2013; Cao et al. 2008) . To prevent it, one uses herbicides, which play a key role in the maize conservation programmes. Furthermore, residues in the soil may pose a risk to consumers, which is why their constant monitoring is recommended. The behaviour of herbicides in soil is complex and depends on many factors, such as the type of crop, soil pH, organic matter content, temperature, irrigation and light (Kah and Brown 2006) as well as microbial activity of the soil. Moreover, the properties of the herbicide molecule, such as water solubility, the octanol-water partition coefficient and the dissociation constant, are some of the most important factors influencing the bioavailability of these molecules (Chirukuri and Atmakuru 2015) . The information about these processes is important for the evaluation of the dissipation rate of herbicides which allows for selecting the substances which may pose a potential threat to the natural environment as well as human and animal health. Among herbicides, a very important one is Smetolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)N-[(1S)-2-methoxy-1-methylethyl]aceta-mide) used for selective weed, with wider use in sorghum, maize, cotton, potato, soybean, peanut or sunflower (Tomlin 2003 ). It is a chloroacetanilide herbicide classified as an inhibitor of very-long-chain fatty acid (VLCFA) formation (Tanetani et al. 2011) . In its commercial formulation, S-metolachlor contains 88% S-enantiomer and 12% R-enantiomer, but the only biological active ingredient is S-enantiomer (Dale et al. 2006) . Different behaviours in the soil sorption and dissipation processes are observed for this herbicide, which is related to its different chemical properties. S-metolachlor has a relatively high solubility in water (480 mg L−1), and it is highly soluble in acetone, ethyl acetate, toluene and xylene (PPDB 2014) . Furthermore, its toxicological and environmental profile is favourable for mammals, birds and insects (honeybees included), except that it can be extremely toxic to fish and aquatic species ( YawJian et al. 1999 ). Following their release into the environment, pesticides may have many different fates and understanding their behaviour becomes of major scientific interest. Moreover, the pesticide evolution is conditioned by the microbiological composition of soil, in particular by the activities of soil enzymes (Gevao et al. 2000) . According to Hussain et al. (2009) , first, pesticides may disturb metabolism or soil enzymatic activities, and second, important information on pesti (...truncated)


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Elżbieta Wołejko, Piotr Kaczyński, Bożena Łozowicka, Urszula Wydro, Andrzej Borusiewicz, Izabela Hrynko, Rafał Konecki, Krystyna Snarska, Dorota Dec, Paweł Malinowski. Dissipation of S-metolachlor in plant and soil and effect on enzymatic activities, Environmental Monitoring and Assessment, 2017, pp. 355, Volume 189, Issue 7, DOI: 10.1007/s10661-017-6071-7