Sudarshan Kurwadkar

Time dependent sorption behavior of dinotefuran, imidacloprid and thiamethoxam

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.

Evaluation of leaching potential of three systemic neonicotinoid insecticides in vineyard soil.

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 610mg/L<4100mg/L<39,830mg/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.

Comparative mobility of sulfonamides and bromide tracer in three soils

In animal agriculture, sulfonamides are one of the routinely used groups of antimicrobials for therapeutic and sub-therapeutic purposes. It is observed that, the animals when administered the antimicrobials, often do not completely metabolize them; and excrete the partially metabolized forms into the environment. Due to the continued use of antimicrobials and disposal of untreated waste, widespread occurrence of partially metabolized antimicrobials in aquatic and terrestrial environments has been reported in various scientific journals. In this research, the mobility of two sulfonamides - sulfamethazine (SMN), sulfathiazole (STZ) and a conservative bromide tracer was investigated in three soils collected from regions in the United States with large number of concentrated animal-feed operations. Results of a series of column studies indicate that the mobility of these two sulfonamides was dependent on pH, soil charge density, and contact time. At low pH and high charge density, substantial retention of sulfonamides was observed in all three soils investigated, due to the increased fraction of cationic and neutral forms of the sulfonamides. Conversely, enhanced mobility was observed at high pH, where the sulfonamides are predominantly in the anionic form. The results indicate that when both SMN and STZ are predominantly in anionic forms, their mobility approximates the mobility of a conservative bromide tracer. This observation is consistent for the mobility of both SMN and STZ individually, and also in the presence of several other antimicrobials in all three soils investigated. Higher contact time indicates lower mobility due to increased interaction with soil material.

Modeling photodegradation kinetics of three systemic neonicotinoids – dinotefuran, imidacloprid and thiamethoxam in aqueous and soil environment

Environmental presence and retention of commonly used neonicotinoid insecticides such as dinotefuran (DNT), imidacloprid (IMD), and thiamethoxam (THM) are a cause for concern and prevention because of their potential toxicity to nontarget species. In the present study the kinetics of the photodegradation of these insecticides were investigated in water and soil compartments under natural light conditions. The results suggest that these insecticides are fairly unstable in both aqueous and soil environments when exposed to natural sunlight. All 3 insecticides exhibit strong first-order degradation rate kinetics in the aqueous phase, with rate constants kDNT , kIMD , and kTHM of 0.20 h(-1) , 0.30 h(-1) , and 0.18 h(-1) , respectively. However, in the soil phase, the modeled photodegradation kinetics appear to be biphasic, with optimal rate constants k1DNT and k2DNT of 0.0198 h(-1) and 0.0022 h(-1) and k1THM and k2THM of 0.0053 h(-1) and 0.0014 h(-1) , respectively. Differentially, in the soil phase, imidacloprid appears to follow the first-order rate kinetics with a kIMD of 0.0013 h(-1) . These results indicate that all 3 neonicotinoids are photodegradable, with higher degradation rates in aqueous environments relative to soil environments. In addition, soil-encapsulated imidacloprid appears to degrade slowly compared with dinotefuran and thiamethoxam and does not emulate the faster degradation rates observed in the aqueous phase. Environ Toxicol Chem 2016;35:1718-1726.

Preliminary studies on occurrence of monensin antibiotic in Bosque River Watershed

Water quality impact due to excessive nutrients has been extensively studied. In recent years, however, micro-pollutants such as pharmaceuticals and hormonal products used in animal agriculture have added an additional impact to overall water quality. Pharmaceuticals used in the poultry, swine, beef, and dairy industries have been detected in various environmental matrices such as, soil, groundwater and surface water. In this study, 26 surface water samples were collected throughout the Bosque River Watershed (BRW) with samples representing a range of land use conditions and locations of major dairy operations. Samples were analyzed using commercially available Enzyme-Linked Immunosorbent Assay test. Of the 26 samples, three samples consistently tested positive for monensin antibiotic with concentration ranging from 0.30 to 3.41 microg/L. These three samples were collected from sites that received varying amount of agriculture wastes (11.7% to 31.3%) and located downstream from sites associated with moderate levels of animal agriculture. The preliminary results suggest that there is a potential for monensin occurrence in the BRW, although initial findings indicate only very low levels.

Uptake and translocation of sulfamethazine by alfalfa grown under hydroponic conditions

Antibiotics are routinely used in intensive animal agriculture operations collectively known as Concentrated Animal Feed Operations (CAFO) which include dairy, poultry and swine farms. Wastewater generated by CAFOs often contains low levels of antibiotics and is typically managed in an anaerobic lagoon. The objective of this research is to investigate the uptake and fate of aqueous sulfamethazine (SMN) antibiotic by alfalfa (Medicago sativa) grass grown under hydroponic conditions. Uptake studies were conducted using hydroponically grown alfalfa in a commercially available nutrient solution supplemented with 10mg/L of SMN antibiotic. Analysis of alfalfa sap, root zone, middle one-third, and top portion of the foliage showed varying uptake rate and translocation of SMN. The highest average amount of SMN (8.58μg/kg) was detected in the root zone, followed by the top portion (1.89μg/kg), middle one-third (1.30μg/kg), and sap (0.38μg/kg) samples, indicating a clear distribution of SMN within the sampled regions. The ultraviolet (UV) spectra of parent SMN and translocated SMN identified in different parts of the plant present the possibility of metabolization during the uptake process. Uptake of SMN using alfalfa grown under hydroponic conditions has potential as a promising remediation technology for removal of similar antibiotics from wastewater lagoons.

Nanoparticles in the Environment: Occurrence, Distribution, and Risks

AbstractRapid advances in nanotechnology in recent years have raised concern about the occurrence, distribution, fate, and transport of nanoparticles in the environment. Sources of nanoparticles in the environment include their widespread use in a variety of engineering operations, biomedical applications, consumer goods, food and drug delivery system, and so forth. Because they can be released into the environment either as a waste product or as a byproduct of some engineered processes or applications, nanoparticles or nanoscale materials are increasingly detected in various environmental matrices. By their very nature, nanoparticles are active at molecular levels, and there is a concern that their occurrence in the environment and unintended exposure may pose an adverse risk to human health and ecology. Because of the nature of recent nanotechnology-based applications, our understanding of nanoparticle behavior in the environment is limited. The objective of this literature review is to provide a measur...

Neonicotinoids: Systemic Insecticides and Systematic Failure

the use of neonicotinoid applications and consequences in agriculture. For example, of the 131 reported instances of neonicotinoid pollution in surface water, nearly 50% of these studies were published in BECT (Stehle and Schulz 2016). It should be noted that imidacloprid was the first generation neonicotinoid to receive widespread attention for its environmental consequences. The third generation of neonicotinoids, dinotefuran, is several orders of magnitude more soluble in water than the first generation (imidacloprid 610 mg/L; thiamethoxam 4100 mg/L; dinotefuran 39,830 mg/L), in addition to being more potent and persistent (PPDB 2012). While these powerful neonicotinoid properties have definitely helped control pest infestations in agricultural and domestic contexts, our knowledge regarding the environmental consequences and risks to non-target species following their widespread use has sorely lagged behind (Fig. 1). More than two decades have passed since the introduction of the first generation of neonicotinoid agents. During this time period an improved understanding of the risks that can result from exposure to residual neonicotinoids in non-target species has been established through various studies. In 2008, the Environmental Fate and Effects Division (Environmental Risk Branch V) of the USEPA, acknowledged via a memorandum the potential risks that neonicotinoids present for non-target species such as upland game birds, endangered aquatic invertebrates in both freshwater and marine environments and secondary toxicity to fish due to alteration of food chains (USEPA 2008). It is interesting that, in the same memorandum the USEPA cited disorientation and death of honeybees in France in 1999. These honeybee deaths were attributed to exposure to imidacloprid through foraging on sunflowers grown from imidacloprid coated seeds (USEPA 2008). Since then the pace of scientific understanding regarding As we celebrate 50 years of publication of the Bulletin of Environmental Contamination and Toxicology (BECT), we are simultaneously discovering that the widespread adoption and use of neonicotinoid compounds originally considered to be environmentally benign can now potentially be considered to be an environmental catastrophe. Imidacloprid, the first generation neonicotinoid, was made commercially available by Bayer AG in 1994. This neurotoxin rapidly became extremely popular due to its high insecticidal activity at low application rate (0.3 mg/L). In 2004 alone, 131,394 pounds of imidacloprid-based formulations were applied for insecticidal purposes in the State of California (Fossen 2006). In 2016, imidacloprid was the most widely used neonicotinoid in the world (Mathiesen and Goldenberg 2016). The second generation of neonicotinoids (thiamethoxam) was introduced by Syngenta in 2000, and was quickly followed by a third generation of neonicotinoids (dinotefuran), made commercially available by Bayer AG in 2005. While the generational development and production of neonicotinoids has focused on making these insecticides more potent to their target organisms at very small dosages, their adverse environmental consequences have largely remained overlooked. BECT published its first article on neonicotinoids in 1994, reporting on the persistence of imidacloprid (Rouchaud et al. 1994). Indeed, BECT pioneered reporting on the environmental concerns about