Dissipation of Propanil and 3,4 Dichloroaniline in Three Different Rice Management Systems

Abstract

This study focused on the dissipation of propanil and 3,4 dichloroaniline (3,4 DCA) over time in the soil, field water, inlet water, and outlet water of paddy fields under three management systems: conventional water seeding (CON), conventional water seeding with supplied liquid manure (LMA), and dry seeding (DRY). Propanil dissipation in water was also investigated under laboratory conditions. The field study was conducted from 2004 to 2006 at Vercelli, northern Italy. Propanil and 3,4 DCA showed rapid dissipation in water and soil environments both in the field and in the laboratory. Under controlled conditions, chemical hydrolysis was not detected for either compounds for up to 100 d at pHs of 5, 7, and 9. In the laboratory, the half-life of propanil in irrigation water was 1.1 d; its half-life in soil was routinely measured at <1.0 d (between 0.17 and 1.77 d). 3,4 DCA was found to persist much longer. Measured in all three study years at 50 d after treatment, its concentration ranged between 44 μg kg (CON) and 140 μg kg (DRY). Propanil and 3,4 DCA concentrations in paddy water were particularly high in samples collected at 4 d (2004) and 2 d (2005) after treatment. Maximum concentrations were 54.4 μg L (CON) for propanil (2005) and 113.7 μg L (LMA) for 3,4 DCA (2004). The concentrations of propanil and 3,4 DCA in inlet water were never above 1.1 and 0.3 μg L, respectively, whereas the highest concentration of each compound in outlet water was in samples collected first after treatment in 2005 and 2006. Both chemicals dissipated rapidly in all the soil-water environments but displayed no important differences among the three management systems. In conclusion, propanil and 3,4 DCA did not persist longer in paddy fields. A risk of water network contamination by these compounds may occur only early after herbicide spraying. A water-holding period after herbicide spraying may reduce this risk.

Imazamox dissipation in two rice management systems

“…The presence of imazamox in the ditch water is probably related to treatments performed in paddies located upstream from the experimental fields, as herbicides applied to rice fields supplied by diffuse water networks can be lost via drifting and runoff during and after spraying, reaching the channels. A similar behaviour was observed in previous studies conducted on other pesticides (Milan et al 2012). Moreover, the current results indicated that outlet waters reaching the end of the main channels might transport sizeable amounts of imazamox.…”

Oxadiazon Dissipation in Water and Topsoil in Flooded and Dry-Seeded Rice Fields

“…These phenomena are likely more pronounced in case of pesticides applied in pre-emergence on bare soil and when flooding occurs early after the spraying. Previous studies carried out on rice pesticides confirmed the strict interaction between flooding water and the top soil layer [28,29], as they highlighted the formation of a gradient of concentration in paddy water from the upper part of the fields (close to inlet floodgate) to the bottom part of them (close to the outlet floodgate). The data of this study agree with the results of Das et al [30], which determined for oxadiazon an average soil half-life in the rice rhizosphere of 8.8 days.…”

“…Herbicides may reach water compartments through several phenomena of transport, as runoff, leaching, drift and soil erosion [13]. Risk of contamination of water bodies is particularly important in paddy fields, where the presence of flooding water over the season may facilitate the transfer of herbicides out of the fields by irrigation drainage and runoff [28,32]. Despite oxadiazon being an herbicide with a long history of application-it was introduced on the market in 1969 by Rhône-Poulenc-only a few studies have investigated the fate of this chemical in paddy fields.…”

Effects of environmental conditions on propanil degrading activity of <i> Acinetobacter baumannii</i> DT

“…The propanil degradation was also determined in soil without inoculation. Propanil in soil was extracted with acetone as described by Milan et al (2012). The extraction efficiencies of propanil from contaminated and uncontaminated soil were 92.0% and 94.6%, respectively.…”