"The movement of DNT and THM in postapplication scenarios is not well understood, but reasonably expected to be a strong function of both the chemical properties of DNT and THM and physico-chemical soil properties. Persistence and transformation studies conducted by Karmarkar et al. (2006) over a 30-day time period demonstrated that sandy clay loam has the highest leaching potential (81.6%) for THM compared to loamy sand (55.7%), silty clay loam (78.8%), and sandy loam soils (69.5%). Leaching studies on THM demonstrated that 66–79% of THM could leach with the water equivalent of 65 cm rainfall, indicating THM has a potential to leach and affect groundwater under heavy rainfall conditions (Gupta et al., 2008). "
[Show abstract][Hide abstract] ABSTRACT: Dinotefuran (DNT), imidacloprid (IMD), and thiamethoxam (THM) are commonly used neonicotinoid insecticides in a variety of agriculture operations. Although these insecticides help growers control pest infestation, the residual environmental occurrence of insecticides may cause unintended adverse ecological consequences to non-target species. In this study, the leaching behavior of DNT, IMD, and THM was investigated in soils collected from an active AgriLife Research Extension Center (AREC) vineyard. A series of column experiments were conducted to evaluate the leaching potential of insecticides under two experimental scenarios: a) individual pulse mode, and b) mixed pulse mode. In both scenarios, the breakthrough pattern of the insecticides in the mostly acidic to neutral vineyard soil clearly demonstrates medium to high leachability. Of the three insecticides studied for leaching, DNT has exhibited high leaching potential and exited the column with fewer pore volumes, whereas IMD was retained for longer, indicating lower leachability. Relative differences in leaching behavior of neonicotinoids could be attributed to their solubility with the leaching pattern IMD < THM < DNT showing strong correlation with increasing aqueous solubility 610 mg/L < 4100 mg/L < 39,830 mg/L. Triplicate column study experiments were conducted to evaluate the consistency of the breakthrough pattern of these insecticides. The repeatability of the breakthrough curves shows that both DNT and IMD are reproducible between runs, whereas, THM shows some inconsistency. Leaching behavior of neonicotinoid insecticides based on the leachability indices such as groundwater ubiquity score, relative leaching potential, and partitioning between different environmental matrices through a fugacity-based equilibrium criterion model clearly indicates that DNT may pose a greater threat to aquatic resources compared to IMD and THM.
"Therefore, an evaluation of the safety and efficacy of its applications has become the biggest concern for human health and its maximum residue limits (MRLs) in many crops have been legislated in some countries. In recent years, analytical methods for the determination of thiamethoxam and its dissipation, residue levels at harvest, and other behaviors in soil, water and some crops have been reported (Campbell et al. 2005; Karmakar et al. 2006; Gupta et al. 2008). However, there are few reports on the fate of thiamethoxam residues and dissipation in tobacco and its environment. "
[Show abstract][Hide abstract] ABSTRACT: A two-year field experiment was conducted in two different locations to investigate the dissipation rate and residual fate of thiamethoxam in tobacco leaves and soil by high performance liquid chromatography with UV detection. The average recoveries for green, cured tobacco leaves and soil ranged from 89.7 %-94.8 %, 90.6 %-94.4 % and 89.0%-92.8 %, respectively, with relative standard deviations between 2.7 % and 9.2 %. The dissipation rates of thiamethoxam were described by first-order kinetics and its half-life values were in the range of 3.9-4.4 days in green tobacco leaves and 12.0-19.1 days in soil, respectively. The residue levels of thiamethoxam at harvest time ranged from 0.020-0.541 mg/kg in cured tobacco leaves, and 0.005-0.019 mg/kg in soil, respectively.
Bulletin of Environmental Contamination and Toxicology 06/2013; 91(2). DOI:10.1007/s00128-013-1043-2 · 1.26 Impact Factor
" Another study reported that persistence behavior of THM varies with soil types with half-life ranging from 11 to 26 days with dissipation of THM being slowest in loamy sand (55.7%) compared to sandy clay loam (81.6%), silty clay loam (78.8%), and sandy loam soils (69.5%).  From the literature review, it is clear that several researchers have extensively studied IMD, but DNT and THM have not been as thoroughly investigated owing to their more recent commercial introduction. There are no studies on the fate and transport of DNT in the subsurface environment. "
[Show abstract][Hide abstract] ABSTRACT: Dinetofuran (DNT), imidacloprid (IMD) and thiamethoxam (THM) are among the neonicotinoid insecticides widely used for managing insect pests of agricultural and veterinary importance. Environmental occurrence of neonicotinoid in post-application scenario poses unknown issues to human health and ecology. A sorption kinetic study provides much needed information on physico-chemical interaction of neonicotinoid with soil material. In this research study, time-dependent sorption behavior of DNT, IMD and THM in vineyard soil was studied. Sorption kinetics studies were conducted over a period of 96 hours with sampling duration varying from 0, 2, 4, 8, 12, 24, 60 and 96 hours. All three neonicotinoids exhibited very low sorption potential for the soil investigated. Overall percent sorption for all three neonicotinoids was below 20.04 ± 2.03% with highest percent sorption being observed for IMD followed by DNT and THM. All three neonicotinoids are highly soluble with solubility increasing with IMD < THM < DNT. Although, DNT has the highest solubility among all three neonicotinoids investigated, it exhibited higher percent sorption compared to THM, indicating factors other than solubility influenced the sorption kinetics. Low sorption potential of neonicotinoids indicates greater leaching potential with regard to groundwater and surface water contamination.
Journal of Environmental Science and Health Part B Pesticides Food Contaminants and Agricultural Wastes 03/2013; 48(4):237-42. DOI:10.1080/03601234.2013.742412 · 1.20 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.