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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...

Opuntia ficus-indica (prickly pear) and Grindelia squarrosa (gumweed) are two exceptionally drought tolerant plant species capable of growing in arid and semiarid environments. Additionally, they have unique cell wall structures. Prickly pear contains pectin and high levels of ash (16.1%) that is predominantly Ca and K. Gumweed has high levels of extractives that contain grindelic acid and monoterpenoids. The objective of this paper was to evaluate how these unique cell wall components alter the pyrolysis performance of prickly pear and gumweed. Using a tandem micropyrolyzer with GC-MS/FID/TCD, a detailed account of the product slate is given for products generated between 450 and 650 °C. Pyrolysis of prickly pear showed that the high levels of ash increase the amount of organics volatilized and shifted product pools, making it possible to generate up to 7.3% carbonyls vs 3.8% for Pinus taeda (loblolly pine) and 10.5% hydrocarbons vs 1.8% for pine depending on reaction conditions. Pyrolysis of gumweed sho...

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 ...

Soil surfaces receive large quantities of organic contaminants, including combustion products, pesticides, and naturally occurring substances. The heterogeneity of surfaces, however, has not allowed successful modeling of photolysis processes as compared to water or air, which offer greater homogeneity. Several factors must be examined and understood before an assessment of the importance of photochemical processes on soil surfaces can be made. The three primary factors which affect photolysis include the following: depth of photolysis, photochemical quenching-sensitization reactions, and transport processes. Photolysis depths are unlikely to be uniform. Because the depth of photolysis on soil surfaces is shallow, any process that moves compounds into or out of the sunlight-exposed zone will affect the rate of photolysis. For water-soluble, photolabile compounds, photolysis in soils is therefore likely to be a significant transformation pathway. Transport of soluble organic compounds to the soil surface in evaporating water or in soil films may provide a substantial increase in the rate of photolysis at soil surfaces.

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.

Originating at Lake Tahoe, the Truckee River provides 85% of drinking water for the Reno/Sparks metropolitan area. Major highways and a railroad run adjacent to the river, which increases risk of a contaminant spill into the river that could have detrimental effects on drinking water supplies. A one-dimensional solute transport model (OTIS) was applied to the Truckee River. Data from dye studies on the river were used to determine a relationship to estimate dispersion coefficients for the Truckee River and calibrate the model. Two sizes of hypothetical contaminant spills from 9 locations under 13 flow scenarios were simulated. Travel times to the first water intake for a train spill of 130,000 L ranged from 3 to 46 h and maximum simulated concentrations of a conservative water soluble contaminant at the intake ranged from 340 to 4,800 mg=L. Model output was influenced by uncertainties in the equation for longitudinal dispersion, so model runs were executed with estimated dispersion values that were a factor of 1.5 greater and less than the equation-estimated value of dispersion. DOI: 10.1061/(ASCE)WR.1943-5452.0000338. © 2014 American Society of Civil Engineers.

A laboratory scale sulfate-reducing bioreactor column study was used to investigate removal of arsenic, selenium, and sulfate in neutral to alkaline simulated mine water. Selenium was effectively removed as insoluble elemental selenium from 200 μg/L to below the maximum contaminant level (50 μg/L). With the addition of ferrous chloride in the influent, arsenic was also effectively removed to near the maximum contaminant level (10 μg/L). Sulfate removal was apparently limited by the presence of undissociated hydrogen sulfide, which was found to limit sulfate-reducing bacterial activity in the range of 20–40 mg/L and will need to be considered for sulfate-reducing bacteria treatment system designs.

This chapter addresses the development of social responsibility practices for Newmont Mining Corporation’s Emigrant Rain Project in the State of Nevada, USA. It results from Newmont’s concerns related to conflicts on permitting the Emigrant Mine over the past 12 years, which brought the University of Nevada, Reno, and the Newmont Mining Corporation together to investigate the concept of a Good Neighbor Agreement. A Good Neighbor Agreement can be used to understand the relationships between various stakeholders, to improve communication, and to help resolve disagreements. For this purpose, we identified groups of relevant stakeholders based on location, which include the Carlin group, the Twin Creeks Group, and the Long Canyon Group. For the first group, which is geographically close to the examined site, we established levels of influence and their interest in the Emigrant Rain Project, composed stakeholders’ matrixes and maps, and identified the stakeholders’ engagement risks and stakeholders’ engagement methods. For all groups together we conducted a survey to identify the opinions and concerns related to the mining industry in Nevada. The results of this research will be used to develop Good Neighbor Agreements as a general tool for conflict resolution.

Temperature is a major environmental factor influencing land surface volatilization at the time of agricultural field fumigation. Cooler fumigation soil temperatures relevant to Pacific Northwest (PNW) application practices with metam sodium/potassium should result in appreciably reduced methyl isothiocyanate (MITC) emission rates, thus minimizing off target movement and bystander inhalation exposure. Herein, a series of laboratory controlled flow-through soil column assessments were performed evaluating MITC emissions over the range of cooler temperatures (2–13°C). Assessments were also conducted at the maximum allowed label application temperature of 32°C. All assessments were conducted at registration label-specified field moisture capacity, and no more than 50% cumulative MITC loss was observed over the 2-day post-fumigation timeframe. Three-fold reductions in MITC peak fluxes at cooler PNW application temperatures were observed compared to the label maximum temperature. This study supports current EPA metam sodium/potassium label language that indicates surface fumigations during warmer soil conditions should be discouraged.

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.

Alcohol-fed, semi-passive bioreactors have been used to support the growth of sulfate-reducing bacteria (SRB) for treatment of acid drainage from mine sites. An alcohol source not previously examined for use in these reactors is the glycerol-methanol waste remaining after the production of biodiesel fuel. In the laboratory, rock-filled columns were used to investigate biodiesel waste (BDW) as a carbon source for SRB. Columns were provided with water containing 900 mg/L sulfate, and fed reagent-grade glycerol or BDW in sufficient quantity to reduce 50% of the sulfate. Addition of 246 mg/L of reagent-grade glycerol resulted in 50% sulfate reduction and production of up to 59 mg/L of soluble sulfide, while the equivalent of 246 mg/L of glycerol provided as BDW resulted in 55% sulfate reduction and the production of up to 92 mg/L of soluble sulfide. During the initial stages of acclimation, propionic, acetic, formic, and lactic acids were observed. Acid concentrations were reduced over time in the effluent, and organic carbon in the BDW was nearly completely converted to carbon dioxide.

Lepidium latifolium, perennial pepperweed, is an exotic crucifer that has spread explosively in recent years in wetlands and riparian areas of the western United States. Adaptive responses of L. latifolium to different durations of 0, 3, 7, 15, 30 and 50-day soil flooding treatment were investigated. Biomass allocation, adventitious rooting, aerenchyma development and ethylene production in plants were measured. Compared with controls maintained at −20 kPa soil matric water potential, flooding stress reduced total biomass of L. latifolium. After 7 days of flooding, the total biomass and root/shoot ratio of flooded plants were significantly less than those of unflooded controls. The number of adventitious roots on the stem base increased with the duration of flooding. Root porosity was much higher in the flooded plants than in the unflooded controls after 3 days of treatment and rose to 43% after 50 days. Ethylene production in roots was higher in flooded plants than in the control throughout the 50-day duration of flooding and peaked at 7 days. The reduction in the root/shoot ratio, adventitious rooting, and aerenchyma development in flooded L. latifolium are important contributions to flood tolerance. L. latifolium resembled species adapted to standing water conditions in terms of having an initially high porosity, but it resembled species adapted to either saturated or occasionally flooded habitats in terms of the degree of increase in root porosity under flooded conditions. However, in growth of biomass, L. latifolium was more like plants that do not grow in mostly saturated conditions. Thus, L. latifolium appears to be a plant that exhibits plasticity to tolerate or survive saturated conditions, but not to grow well under these conditions. This may be an adaptation to arid or semiarid riparian habitats where spring flooding and summer drought are characteristic.

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.

Sulfate reducing passive bioreactors are increasingly being used to remove metals and raise the pH of acidic waste streams from abandoned mines. These systems commonly use a variety of organic substrates (i.e. manure, wood chips) for sulfate reduction. The effectiveness of these systems decreases as easily accessible reducing equivalents are consumed in the substrate through microbial activity. Using column studies at room temperature (23–26°C), we investigated the addition of lactate and methanol to a depleted manure substrate as a method to reactivate a bioreactor that had lost >95% of sulfate reduction activity. A preliminary experiment compared sulfate removal in gravity fed, flow through bioreactors in which similar masses of each substrate were added to the influent solution. Addition of 148 mg/l lactate resulted in a 69% reduction in sulfate concentration from 300 to 92 mg/l, while addition of 144 mg/l methanol resulted in an 88% reduction in sulfate concentration from 300 to 36 mg/l. Because methanol was found to be an effective sulfate reducing substrate, it was chosen for further experiments due to its inherent physical properties (cost, low freezing point and low viscosity liquid) that make it a superior substrate for remote, high elevation sites where freezing temperatures would hamper the use of aqueous solutions. In these column studies, water containing sulfate and ferrous iron was gravity-fed through the bioreactor columns, along with predetermined methanol concentrations containing reducing equivalents to remove 54% of the sulfate. Following an acclimation period for the columns, sulfate concentrations were reduced from of 900 mg/l in the influent to 454 mg/l in the effluent, that reflects a 93% efficiency of electrons from the donor to the terminal electron acceptor. Iron concentrations were reduced from 100 to 2 mg/l and the pH increased nearly 2 units.

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.

The addition of group VI anions to sediment slurries resulted in the inhibition of the rate of mercury (Hg) methylation. The ranking of inhibition is as follows: tellurate (TeO) > selenate (TeO) > molybdate (MoO) > tungstate (WO). In sediment slurries treated with TeO and SeO, methylmercury (MeHg) formation was significantly inhibited (p 50 nM of TeO and >270 nM of SeO, while the significant inhibition (p < 0.05) of Hg-methylation by MoO and WO was observed in slurries spiked at final concentrations ≥100 μM and ≥700 μM, respectively. Increasing the sulfate (SO) concentration while using fixed concentrations of inhibitors led to the partial reestablishment of some MeHg production in WO-treated slurries, whereas, no such significant change was noticed in sediment slurries treated with MoO and TeO. These observations suggested that WO inhibits Hg methylation by a competitive mechanism, while MoO and TeO are noncompetitive inhibitors. Selenate and SO showed a qualitatively similar effect on Hg methylation at concentrations tested, in that each showed stimulation at low concentrations and inhibition at high concentrations. The depression of MeHg formation by group VI anions was not accompanied by an inhibition of general microbial activity, suggesting that only particular microorganisms, such as sulfate-reducing bacteria, are responsible for Hg methylation. Finally, in the concentration ranges encountered in most natural aquatic environments, the inhibition of MeHg production by group VI anions is unlikely, except in systems where those elements are found in anomalously high concentrations.

Pentachlorophenol (PCP) was applied to loamy sand and sandy clay loam soils to determine the effect of upward evaporative flux on the rates of photolytic loss. Subirrigated soil columns were irradiated by ultraviolet lamps or sunlight to measure relative rates of photolytic loss under differing soil moisture regimes. Photolysis was initially rapid in loamy sand soil under near-saturated flow conditions, with up to 55% more lost in light-exposed treatments in 14 d as compared to dark controls. Rates of transport were slower in sandy clay loam soil, reflecting a soil sorption distribution coefficient of 10 mL/g, as compared to 0.4 mL/g in the loamy sand. Despite slower upward movement, similar amounts of photodegradation of PCP had occurred in the sandy clay loam soil after 14 d. Dropping the water table to the 15 or 25 cm depth resulted in unsaturated flow and increased losses to volatilization, with a much lower relative contribution of photodegradation over the course of the experiments. Up to 77% was lost from the loamy sand soil dark treatments during the 14-day period, due to volatilization and irreversible sorption. Processes that translocate PCP into the sunlit surface zone under near-saturated soil moisture conditions can be expected to enhance rates of photolytic loss while minimizing volatilization.

Good Neighbor Agreements (GNAs) are a relatively new mechanism for improving communication and trust between a mining company and the community. The focus of a GNA will be to provide a written and enforceable agreement, negotiated between the concerned public and the respective mining company to respond to concerns from the public, and also provide a mechanism for conflict resolution, when there is mutual benefit to maintain a working relationship. GNA agreements resulting from current research coupled with international environmental standards will provide the basis for an accessible interactive model. This model will serve as a tool for independent technical scientific expertise and provide strategies for implementation of the GNA. Because of the higher quality environmental standards already in place, this new approach is most likely to be initially applicable in a developed country with mature state and federal regulatory programs, although utilization in other less-developed nations can be beneficial.

On July 14, 1991, 72,000 L of the pesticide Metam (active ingredient, methyl isothiocyanate) was accidentally released into the Upper Sacramento River. We hypothesized that the spill affected streamside microbial communities and that the effects were persistent. To address this hypothesis, we sampled river soils a year later from sites above and below the spill as well as from an agricultural area and determined soil carbon dioxide efflux (as a measure of soil respiration) in response to methyl isothiocyanate in controlled-environment microcosms, resulting in estimates of the EC50 and soil degradation rates of methyl isothiocyanate. The soil respiration EC50s for the river soils ranged from 13.2 to 51.4 μg/g methyl isothiocyanate, whereas that of the agricultural soil was 72.2 μg/g. Thus, the soils from the Upper Sacramento River were more sensitive to the toxicologic effects of methyl isothiocyanate than was the agricultural soil. Soils from below the spill site also showed higher (factor two or more) EC50s than soils from reference locations above the spill site. The half-life of methyl isothiocyanate in soils ranged from 2.7 to 6.9 days and was longer by a factor of two in the river soils. These degradation rates are controlled by both biotic (microbial) and abiotic processes. The presence of a microbial community accelerated the degradation rate by a factor of two. The pattern of EC50 data demonstrates that changes in the microbial community in the river soils were persistent a full year after the spill and that the stress elicited responses that were indicative of physiologic accommodation or selection for resistance at the population, species, and/or community level.

Concentrations of mercury (Hg) were determined in surface waters and associated river bank sediment samples in a river—reservoir system contaminated by mine wastes. The distribution of total and methyl Hg in surface waters along the Carson River was similar to that measured in river bank sediments and influenced by flow regimes. High levels of Hg (up to 7,585 and 7.2 ng Hg/L for total and methyl Hg, respectively) determined on surface water samples were in large part discharged from Hg-contaminated tailings, distributed in the river bank sediments. Once introduced into the river during the spring snowmelt runoff, Hg was transported downstream and accumulated in the lacustrine part of the system. Elemental Hg (Hg0) increased from 0.02 ng/L in the noncontaminated region to about 2 ng/L in the reservoir. The vertical distribution of total methylmercury (MeHgT) in water of the reservoir differs from that observed elsewhere, in both Hg-contaminated and noncontaminated lakes. The highest levels of MeHgT ( 10 m did not enhance MeHg production. In the anoxic hypolimnion of the reservoir, the recycling of MeHgT was more influenced by the redox cycling of Mn. The addition of group VI anions (SeO2−4, MoO2−4, and WO2−4) in the range of concentrations of oxyanion-forming elements found in the Carson River system to anoxic sediment slurry spiked with SO2−4 resulted in the reduction of rates of MeHg production. Their negative effect on MeHg production was enhanced by increasing pH. Group VI anions, analogous to SO2−4 are inhibitory to sulfate-reducing bacteria, which are known to play a key role in MeHg production in anoxic sediments. Accordingly, the particular water geochemistry of the Carson River system could partly explain the observed low levels of MeHg where one would expect higher concentrations.

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.

Selenium, a naturally occurring trace element, is a potential water quality problem in the western U.S.A. due to widespread areas of Se-rich source rock, arid climate, and consequent potential for evapoconcentration. Selenium concentrations in the Truckee, Walker, and Carson River systems which drain the eastern slope of the low Se content Sierra Nevada, California and Nevada, were low, ranging from less than 0.3 nmol/L (nM) to about 16 nM. Selenium was concentrated by evaporation in the flow systems but did not behave conservatively with respect to Cl−. Selenium concentrations were lower in the saline-alkaline terminal lakes of the Truckee and Walker Rivers than in the downstream reaches of the rivers. Potential Se “sinks” in the systems include bacterial reduction of Se in anoxic water and sediments and biomethylation of Se and subsequent degassing of the volatile Se species to the atmosphere.

A scanning UV-Vis detector, linked by fiber optics to a heated remote flow cell, was interfaced to a gas chromatograph and gas chromatograph-mass spectrometer equipped with conventional split/splitless injectors and a 30 m × 0.32 mm, 0.25 μm capillary column. Gas-phase UV spectra with a 3 nm effective bandpass are shown for benzene, biphenyl, anthracene, phenanthrene, benzo-α-pyrene, methyllanisoles and polychlorinated biphenyls. Chromatograms at a single wavelength are presented for Aroclors 1254 and 1221. A dual mass-UV chromatogram is shown for unleaded gasoline. Calibration curves generated for aromatic hydrocarbons suggest linearity of detector response over a range of about 104. A total absorbance chromatogram is shown for four components of a text mixture. Detection limits for a moderate UV absorber, biphenyl, were 1.0 ng in summed scanning mode and 750 pg in single-wavelength mode, using a criterion of three standard deviations of the baseline noise. The single-wavelength detection limit for naphthalene, a stronger UV absorber, was 90 pg.

The inactivation of coliform bacteria and poliovirus 1 was studied in secondary wastewater effluent containing suspensions of titanium dioxide (250 mg 1−1) irradiated with either F40BL fluorescent lights or sunlight. Approximately 150 min were required to achieve two-log inactivation of coliform bacteria under laboratory lights, while the two-log inactivation of poliovirus 1 occurred in approximately 30 min. No differences in photocatalytic disinfection rates were found when the assays were conducted in the pH range of 5–8. The results show that poliovirus 1 was effectively inactivated by titanium dioxide photocatalysis, and the rates were more rapid than for the inactivation of coliform bacteria. However, the photocatalytic disinfection of effluents using titanium dioxide under sunlight may be limited due to the relatively low inactivation rates and resulting long contact times compared to conventional disinfection methods.

The effects of pH, soluble chemical oxygen demand (COD), suspended solids, and ammonia ‐nitrogen on the titanium dioxide (TiO2)‐photocatalyzed treatment of l,2‐bis(2‐chloroethoxy)ethane (BCEE) were investigated in secondary wastewater effluent. The photochemical oxidation of BCEE was pH dependent and most rapid at pH 4. Sequential increases in soluble COD were provided by the addition of filtered wastewater influent, and suspended solids were varied by adding sonicated mixed liquor. Photocatalysis rates were inversely proportional to soluble COD concentrations, and the reaction was completely quenched at a soluble COD of 164 mg l‐1. Suspended solids in concentrations up to 90 mg l‐1 and ammonia ‐nitrogen (0.83–70 mg 1‐1) did not affect the photochemical oxidation of BCEE. The results show that, of the water quality characteristics investigated, only soluble COD affected TiO2‐mediated photocatalysis of the chloroether under the conditions of this study. Therefore, photocatalytic treatment of biore...

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.

Silica sand contaminated with perchloroethylene (PCE) was effectively treated by Fenton's reagent. Silica sand contaminated with PCE at 1000 mg/kg was totally mineralized in 3 h by Fenton's reagent with initial concentration of about 2.1 M of H 2 O 2 and 5 mM of FeSO 4 . Results from gas chromatography-mass spectroscopy (GC-MS) revealed that dichloroacetic acid was the sole significant intermediate species generated, and was believed to be limiting species leading to miniralization

The photolysis of a series of aryl ketones on air-dried soil surfaces was examined to establish whether vapor transport has an effect on the rate and extent of photolysis. If vapor transport were significant on light-exposed soils, then differences in the observed photolysis rate profiles would be expected, with the compounds having higher vapor pressures exhibiting the greatest photolysis. The aryl ketones, including hexanophenone, octanophenone, dodecanophenone, hexadecanophenone, and octadecanophenone, had nearly identical photolysis rates in solution exposed to sunlamps (Λmax 310 nm). The vapor pressures of these five compounds (25 °C) were estimated by a capillary gas chromatographic method and varied from 8.7 × 10−3 to 8.4 × 10−8 torr. The compounds were irradiated for 15 d on an air-dried sandy loam soil surface. The photolysis rate profiles of the four aryl ketones with vapor pressures from 1.3 × 10−3 torr to 8.4 × 10−8 torr were identical within experimental error, whereas the most volatile congener, hexanophenone, showed approximately 10% greater loss. Volatilization of hexanophenone appears to have caused the compound to move into the light-exposed soil surface to a greater extent than the other compounds. These results suggest that vaporization is not important for loss or transport of the compounds with vapor pressures less than 1.3 × 10−3 torr on air-dried soils within the 15-d irradiation.

The objective of this study were to determine the relative rates of loss of various gasoline hydrocarbons from soil in a field experiment, and to evaluate conditions which maximize volatilization, thus providing an inexpensive decontamination method

High performance liquid chromatography was used to determine interspecific differences in relative concentrations of individual coumarin and flavonoid compounds present in the persistent leaves of six Artemisia L. taxa from subgenus Tridentatae (McArthur), tribe Anthemideae, family Asteraceae. An internal standard technique provided an integrated area profile characteristic of each taxon and allowed relative quantification of up to 34 compounds present in the extracts. Sagebrush samples were collected during 1984 and 1986 from various locations and seasons throughout northern Nevada. Subsequent discriminant analysis performed on relative concentrations among 31 phenolic constituents in the extracts for these six taxa revealed 100% classification agreement to morphological identifications. Two-way (species-by-plants) ANOVA indicated that all significantly variable phenolic concentrations arose from interspecific differences. Interspecific variability in phenolic concentrations among these six taxa appears to be greater than interplant, geographic, or seasonal variation. Whether or not interspecific differences in phenolic concentrations among these six taxa represent genetic or environmental influences has not yet been determined.

Phenolic substances present in persisent leaves of 10 wyoming big sagebrush plants (Artemisia tridentata Nutall ssp. wyomingensis Beetle & Young; Asteracae), growing wild from an unknown seed source were monitored over a two-year period to determine intraplant, interplant and seasonal variations in concentration using high performance liquid chromatography (HPLC). Phenolics in extracts of whole flowers were also monitored from early development to senescence during year two. Up to 36 compounds were separated in the extracts and the identified constituents included a large array of coumarins and flavonoids. Statistical analyses of the data indicated that 53% of the individual phenolics present in persistent leaves varied significantly over two years at P ≥ 0.05. However, during the four-month period of flower development, concentrations of only 39% of the phenolics varied significantly in persistent leaves. A posteriori tests performed on the 11 most highly variable phenolics over the two years showed that the variation in concentration occurs between seasons and not within. The results also revealed that intraplant variability was lower than interplant variation, and interplant variability in concentrations was generally equal to seasonal variability over two years. Thus, the observed seasonable changes of phenolic concentrations in persistent leaves were found to be relatively consistent and predictable both from season to season and from year to year.

— Photosensitized inhibition of mitochondrial succinoxidase by hypericin was measured in vitro and found to be drug-dose, light-dose, and wavelength dependent. Singlet oxygen generation, monitored using the singlet oxygen trap tetramethylethylene, and oxygen consumption in isolated mitochondria sensitized by hypericin were also light-dose and wavelength dependent. Unequivocal evidence for the generation of singlet oxygen was obtained using kinetic isotope ratios of products from the reaction between singlet oxygen and geminally deuterated tetramethylethylene. An action spectrum for the inhibition of succinoxidase was measured at wavelengths between 400 and 700 nm and found to parallel the recorded visible absorption spectrum of hypericin in isolated mitochondria. The greatest singlet oxygen generation, oxygen consumption, and succinoxidase inhibition occurred with white light or 600 nm irradiation. These data are consistent with a type II singlet-oxygen-mediated mechanism for hypericin induced photosensitized inhibition of mitochondrial succinoxidase.

A remote flow cell has been interfaced to a scanning uv‐visible absorbance detector for the detection of gas chromatography (GC) analytes. The unique optical bench, detection scheme, and thermal control allow low‐noise operation at flow cell temperatures of 350 °C. Noise of 1×10−5 a.u. (peak to peak over a 1‐min period) and drift at the 1×10−4 a.u./h level facilitate detection of coumarin in the gas phase at 40 pg/s. Flow cell volume was optimized for use with capillary GC columns. An effective band pass of

The disappearance of carbaryl from the surface of the cuticle was correlated with the incorporation of [1- 14 C]acetate into hydrocarbon and its transport to the surface of the insect during development in the cabbage looper, Trichoplusia ni . The uptake of carbaryl, as measured by the disappearance of [1- 14 C]carbaryl from the surface of the insect, followed the same trends, in general, as did the rates of transport of hydrocarbon to the surface. The highest uptake occurred during the larval feeding stages and the lowest uptake occurred during the pupal stage. The similarity between the time of highest transport of labeled hydrocarbon to the surface of the insect and the time of highest uptake of labeled carbaryl during development suggest a common route for transport of hydrocarbon to the surface and the uptake of the insecticide.

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. (...)

The lifetime of traditional sulfate-reducing bacteria (SRB) bioreactors that utilize a source of reducing equivalents contained within the matrix (e.g. manure) is limited by the amount of readily available reducing equivalents within that matrix. In order to extend bioreactor lifetime indefinitely, the addition of known concentrations of alternative reducing equivalents (methanol and ethanol) to a depleted matrix was tested at low pH and low temperatures. Following acclimation, up to 100% efficiencies of reducing equivalents were directed toward sulfate reduction. Alcohol was added in stoichiometric concentrations to remove 50% of the added sulfate (900 mg/L), producing sufficient sulfide to precipitate all of the iron from solution. An average of 42% of the sulfate was removed following acclimation, reflecting 84% efficiency. An average of 93% of the iron was removed (93 mg/L). Bacteria acclimated to ethanol more rapidly than methanol, although both alcohols were effective as carbon sources. Efficient treatment was observed at the lowest temperatures (6 degrees C) and lowest pHs (pH=2.5) tested. The use of ethanol-fed, highly permeable bioreactor matrices of wood chip, pulverized plastic and rock was also examined to determine which of these porous matrices could be implemented in a field bioreactor. Results indicated that95% of the 100mg/L iron added was removed by all matrices. Sufficient reducing equivalents were added to remove 450 mg/L of sulfate, wood and rock matrices removed approximately 350 mg/L plastic removed approximately 225 mg/L. A study comparing rock size indicated that small rocks removed iron and sulfate more efficiently than medium- and large-size rocks. The results suggest that wood and rock in conjunction with ethanol are viable alternatives to traditional bioreactor matrices. These findings have direct application to semi-passive sustained operation of SRB bioreactors for treatment of acidic drainage at remote sites.