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)