Kinetic field dissipation and fate of endosulfan after application on Theobroma cacao farm in tropical Southwestern Nigeria

Abstract

benzodioxathiepin-3-oxide is still a pesticide of choice for most cocoa farmers in Southwestern Nigeria, in spite of its persistence, bio-accumulative, toxicological properties and restriction. A single-treatment of 1.4 kg ai/ha (0.5% ai) of technical grade endosulfan (Thiodan, 35EC) was applied to 0.0227 hectare of cultivated Theobroma cacao L. (Cocoa) farm at the Cocoa Research Institute of Nigeria (CRIN). Levels of parent endosulfan (α-, β-endosulfan) and major metabolite (endosulfan sulfate) were determined in vegetation and surrounding matrices at days 0, 7, 14, 21, 28, 42 and 60 using GC-MS. Their kinetic variables were determined. Order of ∑endosulfan distribution at day 0 was: dry foliage>fresh foliage>bark>pods>soil (0-15cm). No residual endosulfan was found in cocoa seeds and sub-surface soil (15-30 cm). Low residual levels in pods on day 0 may be due to endogenous enzymatic breakdown, with αisomer more susceptible and α/β-endosulfan ratio being 0.90. Fell dry foliage as mulch was predominantly the receiving matrix for non-target endosulfan sprayed. Volatilization was key in endosulfan dissipation between days 0 and 7 from foliage surfaces (> 60% loss), while dissipation trend were bi-phasic and tri-phasic for vegetation and soil respectively. ∑endosulfan loss at terminal day ranged between 40.60% (topsoil) and 99.47% (fresh foliage). Iteratively computed half-lives (DT ' 50) ranged from 6.48-30.13d for ∑endosulfan in vegetation. Endosulfan was moderately persistent in pods-a potential source for cross contamination of seeds during harvest. Iteratively determined DT ' 50 and initial-final day DT50 are highly correlated (R=0.9525; n= 28) and no significant difference (P=0.05) for both methods.

Introducing ground cover management in pesticide emission modeling

“…The modeling of GCM fills a gap in the consideration of common farming practices, and demonstrated the potential of GCM to reduce emissions to field soil and related freshwater ecotoxicity impacts. Following our proposed approach to considering GCM processes, our emission results reproduce well the effect of GC on pesticide distribution as observed in cocoa farm systems by Vaikosen et al ( 2019 ), where the reduction in bare soil surface with a GC of fallen leaves of the main crop decreased emission to the top soil. The higher the fraction of effective area of cover (composed of living or dead cover), the lower the fraction distributed to field soil.…”

Assessment of systemic and carcinogenic health risks of persistent organochlorine pesticide residues in four fruit vegetables in south-western Nigeria

“…These findings further confirmed that the pesticides were still available in Nigeria either singly or as a mixture with other active ingredients despite their ban. A long-time accumulation of the endosulfan sulphate in soil and on plant surfaces have been reported to be due to its persistent as a major metabolite of the less persistent α - and β -endosulfan (Jack and Phil, 2004; Rosendahl et al , 2009) with a half-life 1.5 times longer than other isomers (Vaikosen et al , 2019) and this could have been one of the reasons for its high concentration in the fruit vegetables. The technical or commercial endosulfan pesticide (90–95% of the pure endosulfan mixture) is a mixture of α -endosulfan (70%) and β -endosulfan (30%) (Yu et al , 2014; Baqar et al , 2018).…”

“…The technical or commercial endosulfan pesticide (90–95% of the pure endosulfan mixture) is a mixture of α -endosulfan (70%) and β -endosulfan (30%) (Yu et al , 2014; Baqar et al , 2018). The lower concentrations of α-endosulfan in comparison to other isomers showed that the applied pesticides had degraded to more persistent isomers as the α-isomers are more susceptible to enzymatic breakdown or easily degraded (Yu et al , 2014; Vaikosen et al , 2019).…”

Dietary risk assessment of organochlorine pesticide residues in maize-based complementary breakfast food products in Nigeria

“…The levels of endosulfan sulfate detected in this study were higher than the concentrations earlier reported by Sosan et al (2018) and Anzene et al (2014) on maize from Nasarawa State, Nigeria. The higher concentrations of endosulfan sulfate could be due to volatilization and degradation of endosulfan (αand β-isomers) present on the maize grains to a more persistence endosulfan sulfate leading to its increase in concentration, as the endosulfan (α-and β-isomers) are easily degraded with shorter half-life on plant and soils (Vaikosen et al, 2019).…”