An integrated theoretical and experimental investigation of insensitive munition compounds adsorption on cellulose,cellulose triacetate, chitin and chitosan surfaces

This manuscript reports results of combined computational chemistry and batch adsorption investigation of insensitive munition compounds, 2,4-dinitroanisole（DNAN）, triaminotrinitrobenzene（TATB）, 1,1-diamino-2,2-dinitroethene（FOX-7） and nitroguanidine（NQ）, and traditional munition compound 2,4,6-trinitrotoluene（TNT） on the surfaces of cellulose, cellulose triacetate, chitin and chitosan biopolymers. Cellulose,cellulose triacetate, chitin and chitosan were modeled as trimeric form of the linear chain of4 C1 chair conformation of β-D-glucopyranos, its triacetate form, β-N-acetylglucosamine and D-glucosamine, respectively, in the 1 ？ 4 linkage. Geometries were optimized at the M062 X functional level of the density functional theory（DFT） using the 6-31 G（d,p） basis set in the gas phase and in the bulk water solution using the conductor-like polarizable continuum model（CPCM） approach. The nature of potential energy surfaces of the optimized geometries were ascertained through the harmonic vibrational frequency analysis. The basis set superposition error（BSSE） corrected interaction energies were obtained using the 6-311 G（d,p）basis set at the same theoretical level. The computed BSSE in the gas phase was used to correct interaction energy in the bulk water solution. Computed and experimental results regarding the ability of considered surfaces in adsorbing the insensitive munitions compounds are discussed.

Effect of indaziflam on microbial activity and nitrogen cycling processes in an orchard soil

Indaziflam is a preemergent herbicide widely used for the control of weeds in pecan(Carya illinoinensis)orchards in the southwestern region of the United States.Given the paucity of data regarding the effect of indaziflam on the biochemical properties of soils supporting pecan production,this study was conducted to evaluate the effects of different application rates of indaziflam on soil microbial activity,diversity,and biochemical processes related to nitrogen(N)cycling.During two consecutive growing seasons(2015 and 2016),soil samples were obtained from experimental mesocosms consisting of soil-filled pots where pecan saplings were grown and treated with indaziflam applied at two different rates(25 and 50 g active ingredient(ai)ha^(-1),with the higher rate being slightly lower than the recommended field application rate of 73.1 g ai ha^(-1)).Soil samples were collected approximately one week before and one week after herbicide application for determination of soil microbial biomass and diversity,N mineralization,andβ-glucosaminidase activity.Soil samples collected from the control mesocosms without herbicide application were treated in the laboratory with two rates of indaziflam(75 and 150 g ai ha^(-1))to determine the immediate effect on microbial activity.No significant effect of herbicide treatment on soil respiration and microbial biomass was detected.The results showed a slight to moderate decrease in microbial diversity(7%in 2015 and 44%in 2016).However,decreasedβ-glucosaminidase activity with herbicide treatment was observed in soils from the mesocosms(33%)and soils treated with indaziflam in the laboratory(45%).The mineral N pool was generally dominated by ammonium after indaziflam application,which was consistent with the drastic decrease(75%)in nitrification activity measured in the laboratory experiment.The results of this study indicate that indaziflam,even when applied at higher than recommended rates,has limited effects on soil microbial activity,but may affect N cycling processes.

Microbial and size characterization of airborne particulate matter collected on sticky tapes along US–Mexico border

Particulate matter （PM） emissions from various sources can affect significantly human health and environmental quality especially in the Chihuahuan Desert region along US- Mexico border. The objective of this study was to use the low-cost sticky tape method to collect airborne PM for size characterization and identification of fungal spores. Sticky tape samplers were placed at 1.0 and 2.0 m above the ground surface at experimental sites in Ciudad Ju＆ez, Mexico and at 0.6, 1.2 and 1.8 m at New Mexico sites, USA. Soil samples were collected in both countries to determine fungal diversity, texture and moisture content. Dust particles collected from all of the experimental sites had a dominant texture of clay （〈0.002 mm）. The dominant textures identified from soil samples collected from the US and Mexican sites were loam and sandy clay loam, respectively. Alternaria, Penicillium and Fusarium were frequently found funguses in the US sites while Alternaria and Aspergillus were commonly observed in the Mexican sites. The sticky tapes also showed a similar diversity of fungal microorganisms present in the airborne PM at both Mexico and US sites. Alternaria, Penicillium and Aspergillus were the three groups of airborne fungal microorgan- isms consistently present in the US and Mexican sites. The low-cost sticky tape method has the potential to be used for characterizing different airbome microorganisms and dust particles.

Effect of application rate and irrigation on the movement and dissipation of indaziflam

Indaziflam is a new preemergence herbicide for the control of annual grass and broadleaf weeds in various cropping systems including pecan orchards.The objectives of this study were to（1） determine the mobility and dissipation of indaziflam and（2） evaluate herbicide efficacy in a flood-irrigated pecan orchard in southern New Mexico,USA.Indaziflam was applied at 0,35.5,and 73.1 g/ha in areas with（impacted） and without（unimpacted） tree injury symptoms.Soil samples were collected at 0-15,15-30,and 30-46 cm depths 25,63,90,and 125 days after the first herbicide application.Additional soil samples were collected 4,30,and 55 days after the second application.Indaziflam was detected in soil samples collected at each depth,suggesting movement with irrigation water.Indaziflam concentrations decreased with increasing soil depth and time.Indaziflam mass recoveries were greater in the unimpacted area than in the impacted area after the first and second applications.Dissipation half-lives of indaziflam in the soil ranged from 30 to 85 days for total indaziflam recovered from the entire soil profile after the first and second applications in both areas.The percent weed control was similar in the impacted and unimpacted areas for both rates of indaziflam on 25 and 53 days after application;however,on 90 days after the application,percent weed control was lower in the impacted than unimpacted area.