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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.

A high yield of levulinic acid was produced by directly converting cellulose over a ZrO2 catalyst by a one-pot catalytic aqueous phase partial oxidation (APPO) process. Compared to conventional acid hydrolysis, APPO is a highly selective and environmentally benign process with merits of easy recovery and re-use of heterogeneous catalysts.

A headspace air-sampling experiment was performed in the laboratory to determine the identity and concentrations of monoterpene hydrocarbons that could be attained in the vapor phase surrounding single-leaf pinyon pine (Pinus monophylla Torr. & Frem.) understory litter using controlled air collection conditions at a simulated field temperature of 37.8°C. The total monoterpene hydrocarbon content in 21 sequential samples of air collected from a sealed glass carboy packed with 1.44 kg of single-leaf pinyon litter equivalent to a bulk density of 0.15 g/cm3 averaged 3.56 ± 1.04 mg/liter. The monoterpenesα-pinene and camphene were present in the vapor phase at the highest concentrations, averaging 2.40±0.64 and 0.68±0.22 mg/ liter, respectively. Myrcene,β-pinene, 3-carene,β-phellandrene, andγ-terpinene were all present at average concentrations below 0.30 mg/liter. The first two traps of the sequential air samples yielded the highest concentrations for the monoterpene hydrocarbons; however, the average total levels were relatively stable throughout the remaining 19 traps. Therefore, the data indicate that these hydrocarbons volatilize from the source pinyon litter and maintain an equilibrium in the vapor phase. Although this analysis was conducted using an artificial system, combined with results from our previous studies, mounting evidence indicates that monoterpene hydrocarbons present in the vapor phase of the single-leaf pinyon understory may be toxic to a variety of native plant species and thus further implicates allelopathy as a significant contributor to the observed patterning of associated vegetation in these forests.

Senescent foliage from pines is potentially a large contributor to the total monoterpene content of the litter layer, and the availability of these compounds as phytotoxins may result from release of these compounds into the vapor phase. In order to determine the fate of several monoterpene hydrocarbons in the natural environment, we examined their concentrations in fresh, senescent, and decaying needles from 32 single-leaf pinyon pine (Pinus monophylla Torr. & Frem.: Pinaceae) trees growing at two different locations. Total monoterpene content was highest in the fresh needles (mean=5.6 ± 2.2 mg/g extracted air dry weight), but also remained relatively high in senescent needles (mean=3.6 ±1.8 mg/g extracted air dry weight), either still attached to the tree or forming the freshest layer of understory litter. Decaying needles within a dark decomposing layer of litter material 5–20 cm from the surface were found to contain much lower amounts of total monoterpenes (average: =0.12 ±0.06 mg/g extracted air dry weight). Further investigation of the fate of these compounds in the pinyon understory is required to determine if these hydrocarbons are indeed exerting phytotoxic characteristics.

Stands of quaking aspen (Populus tremuloides) previously cut by beavers (Castor canadensis) consist mainly of root sprouts exhibiting juvenile morphological characteristics. Feeding experiments showed that beavers avoided these sprouts when normal sprouts and branches were present, and an unidentified compound which has not previously been reported in the Salicaceae appears to be responsible for the deterrence of beaver feeding. High performance liquid chromatography (HPLC) showed that several compounds in aspen bark which act as feeding deterrents to other herbivores were not responsible for beaver deterrence. These compounds were found in higher concentrations in normal aspen sprouts and branches than in juvenile-form sprouts. Since juvenile-form sprouts are clones of mature aspen and arise after beaver cutting occurs, we suggest that quaking aspen is plastic in its defensive chemistry, allocating its resources among various secondary metabolites in response to beaver cutting.

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.

1. 1. Injection of [U-14C]aspartic acid into juvenile Macrobrachium rosenbergii resulted in no label being incorporated into asparagine. 2. 2. Labelled taurine was observed 24 hr post injection of [U-14C]serine. Radioactivity was also detected in glycine. 3. 3. The turnover rate of injected [U-14C]taurine suggests a half-life of greater than 28 days in the prawn. 4. 4. Results suggest that a dietary requirement for asparagine may exist in the prawn. In addition, the prawn's nutritional requirement of taurine may be fulfilled by its biosynthesis.

Irradiation of 3,4-dichloroaniline in water (λ > 290nm) gave 2-chloro-5-aminophenol with a conversion of 78±5%. The photolysis quantum yield at 313 nm of 0.052±0.003 was unaffected by cyanide (0.35 M) or pH changes between 4 and 12. A MO calculation indicated a large excited singlet state shift in electron density to the carbon undergoing substitution. The reaction is suggested to proceed through an aryl cation intermediate produced by heterolytic cleavage of the meta carbon-chlorine bond. Reaction from the triplet state is not considered likely since neither oxygen nor sorbic alcohol affected the quantum yield.

Light-induced transformations of organic chemicals have been studied to provide kinetic results concerning the influence of sunlight on pollutant behavior in lakes and rivers. A review of these studies shows that the humus component of the dissolved organic matter in natural water affects aquatic photoreactions in two important ways: by attenuating sunlight and by sensitizing photoreactions. Studies of humus-sensitized photoreactions of furans, sulfides, dienes, nitroaromatic compounds, and other chemicals are discussed. Research concerning effects of aquatic particulates on pollutant photoreaction rates are reviewed. Suspended sediments mainly affect photolysis rates through light attenuation and scattering. Algae, diatoms, and bacteria accelerate light-induced transformations of anilines and phosphorothioate insecticides, suggesting that photobiological processes may play a significant role in the breakdown of certain pollutants in aquatic environments. Evidence is presented that nitrate, iron species, and peroxides may be responsible for sunlight-initiated free radical oxidations of pollutants in some natural waters.

As with the parent pesticide, the significance of a pesticide photoproduct depends on its concentration in a given environmental compartment, its toxicity, and exposure of the organism or ecosystem of interest. This requires an understanding of the production and environmental chemistry of each photoproduct as well as its toxicity. While these data are generally available for the parent pesticide, they are rarely determined in detail for the photoproducts. Although the environmental photochemistry of each pesticide is different, some generalizations can be made. Photochemical oxidations, reductions, hydrolytic reactions, and isomerizations often generate products identical to those of metabolic and nonbiological transformations. The chemistry and environmental stability of each individual photoproduct can be substantially different from those of the original pesticide and other products. With several notable exceptions, however, photoproducts are generally less stable to environmental forces and less toxic than the parent pesticide, at least to the target organism. A most significant exception is the P = S to P = O conversion in the organophosphorus insecticides. This sunlight promoted reaction is important in treated fields and has been implicated as a cause of injury to farmworkers.

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.

Strychnine (C21H22N2O2) sorption on soils and uptake in alfalfa (Medicago sativa L.) were investigated. Using application rates of 52-1040 mg/L strychnine, sorption isotherms were developed on three Nevada soils. Strychnine was found to sorb strongly to the three soils studied; however, isotherms were all nonlinear and the extent of sorption varied with each soil. Desorption characteristics paralleled sorption isotherms, indicating reversibility. Strychnine extraction with ammonium chloride (NH4Cl) solutions was greater than that obtained with water extraction on all soils. An apparent relationship between specific surface area, cation exchange capacity (CEC), and total strychnine sorption was noted. Strychnine movement through soil columns under saturated flow was also investigated for the three soils. These results were similar to the sorption studies in that the soil with the lowest sorptive capacity also required the fewest pore volumes for the eluting strychnine concentration to equal that of the starting concentration. The binding mechanism of strychnine to soil is suggested to be a combination of cation exchange and surface absorption to the organic and inorganic fractions of soil. Potential uptake of strychnine in alfalfa was investigated by applying treated milo (Sorghum vulgare var. subglabrescens) bait to the base of alfalfa plants at rates that exceeded normal rodent treatments. Strychnine was not detected (detection limit 0.03 mg/kg) in whole alfalfa samples taken 4 and 11 d following treatment. The data indicate that strychnine is relatively immobile in soil systems, particularly those of moderate-to-high CEC, and is not expected to leach rapidly nor be significantly taken up by plants

Data are presented concerning the effects of suspended sediments upon photolysis rates of dissolved ultraviolet (u.v.) absorbing pollutants. The malachite green leucocyanide actinometer was found to be a convenient and sensitive device for measurement of solar u.v. radiation (∼ 330 nm) in sediment suspensions. Irradiance measurements by the actinometer were employed to compute diffuse attenuation coefficients for sediment suspensions from six natural water bodies in Georgia, Mississippi, and Montana. Specific attenuation coefficients were remarkably similar for all the sediments examined. Evidence is presented that large underestimates of photolysis rates result when beam attenuation coefficients of turbid water bodies are employed to compute the effects of light attenuation. Finally, it is demonstrated that photolysis rates within the photic zone are generally more rapid in turbid than in clear water. Enhanced photolysis rates in turbid waters are attributed to the increased diffuseness of light caused by scattering.

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.

1. 1. Taurine concentrations were determined in various organs dissected from juvenile Macrobrachium rosenbergii . 2. 2. Heart and nervous tissue had the highest taurine concentrations; this suggests that taurine may function in cardiac and neural processes in the prawn. 3. 3. Relative free amino acid concentrations were determined to investigate changes in concentration following acclimation to various salinities. 4. 4. No significant change in taurine concentration in the prawns was demonstrated at any salinity tested. However, the concentration of alanine increased significantly between 15–20%. The elevated alanine concentration suggests it may function in osmoregulation.

Assessing the sunlight photoreactivity of new pesticides has become common- place in the last decade in recognition of the effects the sun has on the dissipation rate of organic chemicals and their transformation products in various environmental compartments. Several reviewers have summarized research dealing with both the kinetic aspects (Zepp and Cline 1977, Smith et al. 1977, Zepp 1979 and 1980, Zepp and Baughman 1978) and the photoproduct distributions (Sundstrom and Ruzo 1978, Crosby 1979. Moilanen et al. 1975).

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.