Imidacloprid transport and sorption nonequilibrium in single and multilayered columns of Immokalee fine sand

Abstract

Imidacloprid (IMD) is a neonicotinoid pesticide soil-drenched to many crops to control piercing-sucking insects such as the Asian citrus psyllid (ACP). Neonicotinoids are persistent in the environment and transport analyses are helpful estimate leaching potential from soils that could result in groundwater pollution. The objective of this study was to analyze IMD breakthrough under saturated water flow in soil columns packed with three horizons (A, E, Bh) of Immokalee Fine Sand (IFS). Also, we used the dimensionless form of the convective-dispersive model (CD-Model) to compare the optimized transport parameters from each column experiment (retardation factor, R; fraction of instantaneous-to-total retardation, β; and mass transfer coefficient, ω) with the parameters obtained from sorption batch equilibria and sorption kinetics. The tracer (Cl-) breakthrough curves (BTCs) were symmetrical and properly described by the CD-Model. IMD BTCs from A, Bh, and multilayered [A+E+Bh] soil columns showed steep fronts and tailing that were well described by the one-site nonequilibrium (OSNE) model, which was an evidence of non-ideal transport due to IMD mass transfer into the soil organic matter. In general, IMD was weakly-sorbed in the A and Bh horizons (R values of 3.72 ± 0.04 and 3.08 ± 0.07, respectively), and almost no retardation was observed in the E horizon (R = 1.20 ± 0.02) due to its low organic matter content (0.3%). Using the HYDRUS-1D package, optimized parameters (R, β, ω) from the individual columns successfully simulated IMD transport in a multilayered column mimicking an IFS soil profile. These column studies and corresponding simulations agreed with previous findings from batch sorption equilibria and kinetics experiments, where IMD showed one-site kinetic mass transfer between soil surfaces and soil solution. Ideally, sandy soils should be maintained unsaturated by crop irrigation systems and rainfall monitoring during and after soil-drench application. The unsaturated soil will increase IMD retardation factors and residence time for plant uptake, lowering leaching potential from soil layers with low sorption capacity, such as the E horizon.

Emerging Contaminant Imidacloprid in Mediterranean Soils: The Risk of Accumulation Is Greater than the Risk of Leaching

“…The results also showed that the retardation factor increase was more pronounced for IMI, which can be attributed to a stronger preference of IMI towards OM. Retardation factors for IMI obtained here are larger compared to rare other studies [85,86], which can be attributed primarily to higher OM content. On the other hand, the coefficient f showed a decreasing trend with OM content, with protruding values in soils S2 and S4 for DIM (Figure 4b).…”

Imidacloprid soil movement under micro-sprinkler irrigation and soil-drench applications to control Asian citrus psyllid (ACP) and citrus leafminer (CLM)

“…On the contrary, imidacloprid was still present in the soil profile even four to six weeks after application (Tables 2 and 3 ). In this regard, the best available models for Imidacloprid transport in IFS - the convective-dispersive model (CD-model) and the one-site nonequilibrium model (OSNE) - were studied in detailed by Leiva et al [ 40 ]. Shortly, both models describe the solute transport process, and the models’ dimensionless form have a variable called the Retardation Factor ( R ), which is a function of Imidacloprid soil sorption coefficient ( K D , mL g -1 ) and the volumetric soil moisture ( θv , in cm 3 cm -3 ).…”

Photo-degradation dynamics of five neonicotinoids: Bamboo vinegar as a synergistic agent for improved functional duration

“…Neonicotinoids are a relevant class of insecticides, following pyrethroids, organophosphorus, and carbamates, successfully developed based on nicotine modifications [1,2]. Since entering the market at the end of the 1980s, neonicotinoids have been extensively employed in the control of piercing-sucking mouth insects including aphids, aleyrodidae and delphacidae, due to their good root uptake, broad spectrum, high efficiency and low toxicity to mammals [3,4]. Neonicotinoids function by selectively acting as effective agonists of the nicotine acetylcholine receptors (nAChRs) which play a key role in the nervous system of insects.…”