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Grindelia squarrosa biocrude is a promising feedstock for producing high-density cycloalkane fuels for high-performance aircraft due to the branched tricyclic nature of its primary diterpenoid component, grindelic acid. Herein we designed a novel biphasic tandem catalytic process (biTCP) for the conversion of Grindelia squarrosa biocrude into high-density aviation fuels with a superior carbon atom efficiency. The systematic experimental studies provided valuable insights into the effects of process conditions. The detailed speciation was carried out with the complementary chemical analysis techniques. Under the optimum conditions, a ∼90% carbon yield of aviation fuel components was produced from the Grindelia squarrosa biocrude. Multistep tandem reactions, including cyclic ether ring opening, dehydration, hydrogenation, and decarboxylation were carried out in the “one-pot” biTCP. The detailed catalytic reaction mechanism is discussed. A continuous process was designed integrating the extraction of biocrud...

Gumweed (Grindelia squarrosa) has potential as a biofuel/biomaterial crop in arid lands. Two years of biomass production data at University of Nevada, Reno (UNR) field plots varied from 6700 kg/ha up to 14 900 kg/ha with an average of 9950 kg/ha. Gumweed was planted in 4 m × 4 m plots at spacings of 15, 20, 25, 30, and 37 cm with three replications each. Acetone extraction of the ground, dried biomass yielded about 12.5% extractable hydrocarbons, called biocrude or crude resin. Approximately 52% of the biocrude extract consists of the C20 diterpene acid grindelic acid, which is also approximately 6.5% of the dried plant biomass. Additional carboxylic acids bring the total carboxylic acid fraction to approximately 68% of the biocrude. Also found in the biocrude is approximately 4.7% monoterpenes, including pinene, limonene, germacrene, elemene, and camphene. Acid-catalyzed methylation of the biocrude followed by hexane extraction and removal of the hexane and remaining methanol produced an approximately 72...

In this study, bagasse from two arid land plants, grindelia and rabbitbrush, were hydrothermally carbonized (HTC) along with their raw biomass at 200–260 °C for 5 min. Prior to HTC, biocrude was extracted from grindelia (Grindelia squarrosa), whereas rubber was extracted from rabbitbrush (Ericameria nauseosa). Solid hydrochars and HTC process liquids of extracted feedstocks were characterized by ultimate, proximate, fiber, FTIR, higher heating value (HHV), and GC–MS analyses and the results were compared with their corresponding unextracted conditions. Hydrochars were pelletized in a single-press pelletizer and mass and energy densities of the pellets were measured. From the proximate, ultimate, FTIR, and fiber analyses, the bagasse show similar properties of the raw biomass, although the HHV was slightly increased with crude extraction from grindelia and decreased with rubber extraction from rabbitbrush. With the increase of HTC temperature, solid mass yield was decreased up to 44% for grindelia bagasse ...

The soil fumigant metam-sodium (CH3NHCS2Na) produces the bioactive respiratory irritant methyl isothiocyanate (MITC). Recent laboratory gas-phase oxidative studies indicate that MITC rapidly transforms to the more toxic methyl isocyanate (MIC) in the lower atmosphere. Inhalation exposure risks from MITC plus MIC may therefore be an occupational worker and/or bystander health concern. To address this concern, MIC was monitored, along with MITC, in outdoor residential air in Washington state during the peak fall metam fumigation season. XAD-7 cartridges, coated with 1-(2-pyridyl)piperazine, were developed to retain MIC as its stable substituted urea derivative. Of the 68 residential air measurements of MIC, 15 (22%) were observed to be above the California Environmental Protection Agency's chronic inhalation reference level of 1 μg/m(3), with an observed maximum MIC air concentration of 4.4 μg/m(3). This study indicates MIC air concentrations can be anticipated along with MITC in residential air where seasonal metam soil fumigant applications occur.

Growing demands for potable water have strained water resources and increased interest in wastewater reclamation for potable reuse. This interest has brought increased attention to endocrine-disrupting chemicals (EDCs) as emerging water contaminants. The effect of EDCs, and in particular natural steroid hormones, on humans is of heightened interest in the study of wastewater reuse in advanced life support systems (e.g., space missions) because they are excreted in urine and have high endocrine-disrupting potencies. Direct contact membrane distillation (DCMD) and forward osmosis (FO) are being investigated for wastewater treatment in space. Retention of two natural steroid hormones, estrone and 17beta-estradiol, by these two processes was evaluated in the current investigation. DCMD provided greater than 99.5% hormone rejection; DCMD also provided constant flux, greater than 99.9% urea and ammonia rejection, and high water recovery. FO provided from 77 to 99% hormone rejection depending on experiment duration and feed solution chemistry.

Gaseous methyl isothiocyanate (MITC), the principal breakdown product of the soil fumigant metam sodium (sodium N-methyldithiocarbamate), is an inhalation exposure concern to persons living near treated areas. Inhalation exposure also involves gaseous methyl isocyanate (MIC), a highly reactive and toxic transformation product of MITC. In this work, gas-phase hydroxyl (OH) radical reaction rate constants of MITC and MIC have been determined using a static relative rate technique under controlled laboratory conditions. The rate constants obtained are 15.36 × 10(-12) cm(3) molecule(-1) s(-1) for MITC and 3.62 × 10(-12) cm(3) molecule(-1) s(-1) for MIC. The average half-lives of MITC and MIC in the atmosphere are estimated to be 15.7 and 66.5 h, respectively. The molar conversion of MITC to MIC for OH radical reactions is 67% ± 8%, which indicates that MIC is the primary product of the MITC-OH reaction in the gas phase.

Novel methods are described for determining atmospheric photolysis rates for the moderately volatile pesticide, phorate. The gas-phase sunlight photolysis of this substance was determined in three test systems which include: (1) 3-L borosilicate flasks exposed to sunlight and laboratory solar simulation, (2) 100-L Tedlar sunlight exposed air sample bags, and (3) 12,800-L Tedlar sunlight exposed chamber studies using a photochemically stable tracer compound. The kinetic results from all systems indicate rapid gas-phase photolysis under midsummer sunlight conditions with observed half-lives being less than 30 minutes. A pronounced increase in transformation rates with increasing volume to surface area suggests photoreactions occur at more rapid rates in the gas-phase. 14C Radiolabeled phorate irradiations resulted in one conversion product, phorate sulfoxide, and this photoproduct accounted for essentially all of the phorate lost.

Photolysis in soils is effectively limited to the top 0.5 mm of the soil surface. Consequently, processes that move contaminants to this sunlight-irradiated zone may have a significant impact on the degree of photolysis in soils. The effect of upward transport in translocating napropamide [2-(a-naphthoxy)-N,N-diethylpropionamide] into the photic zone was examined using an experimental system in which soils were supplied with water at their base. Sunlight photolysis rates were much greater than predicted if photolysis had been limited to the soil surface, with up to 70% lost in a 3 cm deep loamy sand soil after 14 days of irradiation as compared to dark controls. Rates of loss were slower in a sandy clay loam, with 29% loss over 14 days. Rates of transport were affected by sorption, with measured values of the distribution coefficient K d of 0.4-0.72 and 6.6-7.2 mL/g in loamy sand and sandy clay loam soils, respectively.

Methyl isothiocyanate (MITC) is the major volatile transformation product of the fumigant metam sodium. The objectives of these studies were to determine both the products and the kinetics of photolysis of MITC in the gas phase in order to better understand its transformation in the atmosphere. The gas phase photolysis of MITC was examined using Tedlar, borosilicate, and quartz chambers. Since sorption of MITC on the walls of the reactors is potentially important, these studies used a ratioing technique that relates sorption of MITC to two other photostable compounds of similar vapor pressure. These experiments showed that MITC undergoes photolysis in the gas phase with a half-life of 10 ± 3 h under xenon arc irradiation and slightly greaterthan 1 day of late summer sunlight. Photolysis products were determined using GC-NPD/FPD and GC/MS. Products observed include methyl isocyanate, methyl isocyanide, sulfur dioxide, hydrogen sulfide, carbonyl sulfide, N-methylformamide, and methylamine. These data have implications on the risk assessment of metam sodium on human health and environmental receptors.

The increase in deep pit mining in western North America raises concerns about the environmental impact of mine closure.

The emission rates [ER (μg m -2 s 1 )] for subsurface injections and surface chemigations for 15 fumigant applications were combined with the physicochemical properties of the fumigants [vapor pressure, VP (Pa); water solubility, S w (mg L 1 ); soil adsorption coefficient, K oc (mL g 1 )] and with application conditions [application rate, AR (kg ha -1 ); depth of application, d (cm)]. This resulted in the regression Ln ER = 3.598 - 0.9400 Ln R [R = VP × AR)/(S w × K oc × d)], which can be used to estimate emissions for new applications. Emission rates derived from the linear correlation were used as input to an atmospheric dispersion model to estimate concentrations of fumigants in air at various downwind distances, and the results were compared with concentration values measured in the field near sources. The fumigant correlation along with an atmospheric dispersion model can be used as a rapid screening method by regulatory and enforcement agencies for exposure and risk assessment.

The treatment of soils contaminated with octachlorodibenzo-p-dioxin (OCDD) using a Fenton-like reaction was investigated using four soils, two hydrogen peroxide concentrations, and four temperatures. Loss of OCDD was inversely related to the soil organic carbon content, with 96% OCDD removed in a soil with 2% organic carbon. Use of 3.5% H2O2 and 35% H2O2 was equally effective in a natural soil, but 35% H2O2 was more effective in silica sand. In addition, increased loss of OCDD occurred at elevated temperatures. Analysis of extracts by gas chromatography/mass spectrometry (GC/MS) showed no peaks other than the parent compound, including other dioxin congeners.

Linear anionic polyacrylamide (PAM) has been used in irrigation practices as a flocculating agent to minimize water losses through seepage in earthen canals. The stability of PAM is of concern because of the possibility of acrylamide (AMD) monomer release during environmental weathering. Aqueous solutions of commercial PAM mixed with ferric sulfate, subjected to simulated and natural sunlight irradiation, showed polymer chain scission and release of the AMD monomer. At acid/neutral pH, the amount of AMD released was directly related to the concentration of ferric ion and the irradiation time. At alkaline pH (approximately 8), PAM/Fe(3+) mixtures were stable under irradiation. PAM chain scission involved the hydroxyl radical, but specific AMD release appeared to require PAM-bound iron. Low iron concentrations and alkaline pH of irrigation water would limit AMD release. Residual monomer in PAM can contribute AMD to irrigation water, but concentrations would remain below the U.S. EPA drinking water standard of 0.5 ppb.

Photoreduction of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to 2,3,7-trichlorodibenzo-p-dioxin (TrCDD) in isooctane was found to account for approximately 10% of the loss of TCDD and is thus a minor photolysis pathway. The remainder undergoes conversion by other pathways, which may involve carbon-oxygen cleavage. One new photoproduct of TCDD, formed by a reductive rearrangement, is 4,4{prime},5,5{prime}-tetrachloro-2,2{prime}-dihydroxybiphenyl, as demonstrated by mass spectrometry. Photolysis of TCDD on soils is slow relative to solution photolysis. TCDD on soils is slow relative to solution photolysis. Organic solvent added to the soil enhances the extent of photolysis. Evidence is presented that transport of TCDD to the surface in the organic solvent film is primarily responsible for the increased photolysis, rather than an effect from addition of a reducing hydrogen source. In the unamended soils, photochemical loss of TCDD was observed only for the first 5 days of a 15-day irradiation. In soils containing hexadecane, more than twice the amount of TCDD was lost, and photochemical loss continued at both 10 and 15 days of irradiation. This observation suggests that transport of the light-exposed soil/air interface is occurring. Octachlorodibenzo-p-dioxin (OCDD) undergoes photoreduction on soil surfaces to the lower chlorinated congeners.

The recovery of gasoline constituents from soil by using a sonication/extraction method was evaluated. Ten characteristic compounds were studied: benzene, toluene, n-heptane, m-xylene, nonane, n-propylbenzene, 1,2,4-trimethylbenzene, n-butylbenzene, 1,2,4,5-tetramethylbenzene, and dodecane. Modifications of extraction method EPA 3550 were tested using flame ionization gas chromatography with a 15 m X 0.53 mm id fused-silica capillary column. For dry soils, reducing total solvent extraction volume from 400 to 250 mL resulted in equivalent recoveries and shorter analysis times. Recovery of the gasoline constituents from wet soils was significantly lower than from dry soils for all methods studied. Recoveries were also dependent on the relative constituent volatility. Higher molecular weight compounds were recovered at greater than 80% of the initial amount applied from dry soils; while recoveries of benzene and heptane were generally less than 5%. Using the most efficient extraction procedure, recovery of unleaded gasoline from a dry, spiked soil was 43.2% when expressed on a total petroleum hydrocarbon basis, and recovery from a wet, spiked soil was 21.8%.

The photolysis depth of direct and indirect photolysis in soils was determined with use of two agrochemicals. The dinitroaniline herbicide flumetralin and a dialkyl thioether organophosphorus insecticide disulfoton were homogeneously applied to four soils and irradiated. Flumetralin undergoes direct photolysis while disulfoton undergoes indirect photolysis by reaction with singlet oxygen. Various depths of treated soils (0.4-4.0 mm) were exposed to natural sunlight and laboratory lighting until no further degradation of chemical was detected. (...)

Methods were developed to determine OH reaction rates for medium-weight organophosphorus pesticides in the gas phase. A 57-L chamber was constructed that utilized xenon arc irradiation (290 nm) to photolyze the OH precursor, methyl nitrite. Experiments were performed at elevated temperatures ranging from 60 to 80 degrees C to minimize wall sorption. Solid-phase microextraction (SPME) sampling of the gas phase was employed to assess the simultaneous rate of loss of the pesticides in relation to the rate of loss of two reference substances with known OH rate constants. An internal gas-phase standard (hexachlorobenzene), relatively stable to hydroxyl radicals, was used to assess other processes, which included dilution and wall sorption. The relative reaction rates of the organophosphorus insecticides, diazinon and chlorpyrifos, when compared to reference compounds, were unaffected by various air temperatures between 60 and 80 degrees C. Although both insecticides were expected to react at similar rates on the basis of structural activity model predictions, diazinon reacted 3 times more rapidly than chlorpyrifos and gave estimated environmental OH half-lives of 0.5 and 1.4 h, respectively. The degree of sorption onto the chamber walls was minimal and similar for each of the compounds examined. Experimental gas-phase determinations at elevated temperatures may provide important information that can be used when in the assessment of the potential of airborne pesticide risks to nontarget and ecologically sensitive areas.

New methods were developed to determine photolysis rates of medium-weight pesticides in the gas phase using elevated air temperatures and solid-phase microextraction (SPME). A 57-L glass chamber was constructed that utilized collimated xenon arc irradiation that could heat chamber air to increase the amount of pesticide in the gas phase. Gas-phase photolysis rates were determined at various air temperatures by comparing the rate of loss of each of the tested pesticides to a photochemically stable tracer, hexachlorobenzene. Interval sampling of gas-phase constituents was performed using SPME immediately followed by GC-ECD or GC-MSD analysis. The two pesticides under examination were the dinitroaniline herbicide trifluralin and the organophosphorus insecticide chlorpyrifos. The gas-phase photolysis for trifluralin was found to be rapid with half-lives of 22-24 min corrected for sunlight. These results were comparable to photochemical lifetime estimates from other investigators under sunlight conditions. Elevating temperatures from 60 to 80 degrees C did not affect photolysis rates, and these rates could be extrapolated to environmental temperatures. From 60 to 80 degrees C, gas-phase chlorpyrifos photolysis lifetimes were observed to range from 1.4 to 2.2 h corrected for sunlight and will thus be important together with hydroxyl radical reactions for removing this substance from the atmosphere. At these elevated temperatures, pesticides and tracer compounds were found to be substantially in the gas phase, and possible effects on reaction rates from wall interactions were minimized.

Hydrophobic organic xenobiotics such as polychlorinated dibenzodioxins and polycyclic aromatic hydrocarbons have strong tendencies to sorb on environmental surfaces. This paper summarizes a workshop in which scientists and modelers assembled to discuss nonbiological processes that affect sorption to soil or sediment surfaces and on atmospheric particles. The 20 scientists discussed a variety of topics with a major emphasis on the fate of chlorinated dioxins. The topics include transformation processes, mobility of organic pollutants, fate of organics, and evaluative fate models.

The photochemical generation of singlet oxygen on a variety of soils was confirmed by using two specific singlet oxygen traps. Geminally deuterated 2,3-dimethyl-2-butene and 1,2-dimethylcyclohexene react with singlet oxygen to produce characteristic ratios of deuterated alcohols and endocyclic and exocyclic alcohols, respectively. The ability of irradiated soils to photosensitize the formation of singlet oxygen was independent of the amount of organic matter present, and both the organic and inorganic components of the soils appeared to contribute to the sensitizing activity of the soils. Two soils from rice growing areas of California uniquely photosensitized the conversion of the olefins to saturated alcohols. Other reactions observed for the olefins included epoxidation and ketone formation. Free radical oxidations were not observed to significantly contribute to the loss of either of the olefins. Singlet oxygen reactions on soil surfaces may contribute to transformation of several classes of susceptible xenobiotics.

Irradiation of 10−4M aqueous 4-chloroaniline or N-(4-chlorophenyl)-benzenesulfonamide at >290 nm in air-saturated solutions produced both 4-chloronitrosobenzene and 4-chloronitrobenzene, with a maximum conversion of 23%. 4-Chloronitrobenzene was stable to photolysis and was not formed primarily from 4-chloronitrosobenzene. Formation of both products is proposed to proceed through an N-peroxide to a nitro radical anion which is either reduced to 4-chloronitrosobenzene or oxidized to 4-chloronitrobenzene.

A technique for measuring vapor phase photolysis rates of pesticides was developed and applied to the dinitroaniline herbicide trifluralin. The method consists of sunlight irradiation of trifluralin in a 17 m3 polyethylene chamber. Rates of photolysis are determined by comparing the vapor phase concentration of trifluralin to that of a stable tracer. Both chemicals are volatilized from a black surface inside the chamber. The observed half-lives for trifluralin photolysis ranged from 25–60 min for July, midday sunlight and are consistent with those previously reported and are similar to results obtained in solution.

Photolysis of octachlorodibenzo-p-dioxin (OCDD) on soils results in production of the lower chlorinated dibenzo-p-dioxins, notably 2,3,7,7-tetrachloro-dibenzo-p-dioxin (2,3,7,8-TCDD), 1,2,3,7,8-pentachlorodibenzo-p-dioxin (1,2,3,7,8-PCDD) and three hexachlorodibenzo-p-dioxin isomers substituted at the 2,3,7,8-positions. Photodechlorination is favored at the lateral positions for the H6CDD and P5CDD congeners, based on the relative yields of the various isomers produced. The mean depth of photolysis of OCDD in the two soils examined varied between 0.06 and 0.13 mm.

A gas-liquid chromatographic procedure is described for determining strychnine in alfalfa with a nitrogen- phosphorus detector. Alfalfa samples containing strychnine residues are chopped and extracted in a blender using ethyl acetate, sodium carbonate, and sodium sulfate, and the organic extract is extracted with 0.1N H2SO4 solution, made basic, and subsequently extracted with methylene chloride. Following concentration, the strychnine residues are quantitated by peak height, using an external standard. Recoveries for 0.05 ppm spikes were 88 ± 11%.

Irradiation of the non-transition-metal oxide powders silica gel, aluminium oxide and magnesium oxide in the presence of oxygen results in the formation of singlet oxygen (1O2). Two specific chemical traps were used to detect 1O2: 1,2-dimethylcyclohexene and geminally deuterated [2H6]-2,3-dimethylbut-2-ene. Both compounds gave product distributions characteristic of singlet-oxygen reactions when irradiated on the metal oxide surfaces. These results support previous suggestions that singlet oxygen is formed through an energy-transfer process involving oxygen and excitons on the metal oxide surface. Under the same reaction conditions TiO2 showed no production of 1O2.