New Jersey Site Research Articles

Dynamic Behavior of Systemic Insecticide Residues in Snapdragons

Pesticide application is used in horticulture to reduce plant damage from organisms such as insects and mites. Systemic insecticides are highly efficacious and readily taken up by plant tissues. However, pesticide-treated plants may impose risks to nontarget insects or other organisms within ecosystems. In this study, insecticide residues in nectar, leaves, and flower petals of the horticulturally significant herbaceous annual snapdragon, Antirrhinum majus (Lamiales: Plantaginaceae), were assessed at two locations over several weeks following foliar and drench treatment with five systemic insecticides. Concentrations of the insecticides were determined by liquid chromatography–mass spectrometry. The independent effects Application Method, Application Rate, and Time were statistically significant among all active ingredients in the three matrices in both sites in California (CA) and New Jersey (NJ). The interaction effects were also generally statistically significant in the CA site but less consistently so in the NJ site, dependent on the active ingredient and matrix. Post hoc analyses found the highest residue concentrations in leaves and the lowest in nectar, a trend generally consistent over time regardless of active ingredient for both the CA and NJ sites. The results of this study are discussed in the context of conserving pollinators and other beneficial insects. It is recommended that similar studies should be implemented in different geographical regions and climates, along with multiyear studies for perennial ornamental plants.

Assessing the importance of ab- and adsorption to the gas-particle partitioning of PCDD/Fs

The gas-particle partitioning of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) was examined (i) by re-interpreting results from controlled field experiments and (ii) in diurnal samples taken in the New Jersey (NJ), New York (NY) City region. In the controlled field experiments, aerosol-laden filters were exposed to elevated concentrations of PCDD/Fs. Gas-particle partitioning coefficients, K p's, were significantly correlated with octanol–air partitioning coefficients, K oa's. The regression of all individual datapoints resulted in the following best fit ( r 2=0.74, n=87): log K p,meas=1.00(±0.13) log(10 −12 f om K oa/ ρ oct)−0.15(±0.48). We interpret this as showing that the ability of organic matter (OM) to absorb PCDD/Fs is generally well described by the octanol–air partitioning model ( f om K oa). At the NJ land-based sites, samples were taken and analyzed for organic carbon (OC) and elemental carbon (EC), gaseous and particulate PCDD/Fs. K p's were significantly correlated with the f om K oa approach. Adsorption to the filter and possibly to black carbon (BC), which was estimated based on EC measurements, could have contributed to the observed K p values. Gas-particle predictions based on BC adsorption and OM absorption, with K p= f om K oa/(10 12 ρ oct)+ f BC K BC–air/(10 12 ρ BC) resulted in K p predictions that were close to measured values. Adsorption to the filter might have been the major reason for elevated K p's: The one NJ site with highest K p's was most prone to the filter adsorption sampling artefact because of relatively low sampling volumes and concentrations of total suspended particulates. In addition, while adsorption to BC would result in better prediction of K p values, no influence of f BC or f BC/ f om ratios was seen, suggesting that it was of lesser importance in our sample set.