Glenn C. Miller

Photocatalytic inactivation of coliform bacteria and viruses in secondary wastewater effluent

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.

PHOTOACTIVATION OF HYPERICIN GENERATES SINGLET OXYGEN IN MITOCHONDRIA AND INHIBITS SUCCINOXIDASE

Abstract— 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.

Adaptive responses of Lepidium latifolium to soil flooding: biomass allocation, adventitious rooting, aerenchyma formation and ethylene production

Abstract 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.

Peer reviewed: understanding the water quality of pit lakes.

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

Extrapolating photolysis rates from the laboratory to the environment

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).

High yield production of levulinic acid by catalytic partial oxidation of cellulose in aqueous media

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.

Photolysis of octachlorodibenzo-p-dioxin on soils: Production of 2,3,7,8-tcdd

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.

Monoterpene concentrations in fresh, senescent, and decaying foliage of singleleaf pinyon (Pinus monophylla Torr. & Frem.: Pinaceae) from the western Great Basin

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.

Levels of methylmercury and controlling factors in surface sediments of the Carson River system, Nevada.

Spatial and temporal distribution of methylmercury (MeHg) was determined in surficial sediments collected from a river-reservoir system impacted by Hg-contaminated mine wastes. Despite the fact that total mercury concentrations (HgT) in surface sediments of the Carson River system were in the microg.g(-1) range, levels of MeHg varied from about 2 to 28 ngHg.g(-1) dry weight, representing less than 3% of Hg(T). Concentrations of MeHg were well correlated with both the biotic (r=0.95) and abiotic activity (r=0.85) of the sediment, determined as the ability of each compartment to specifically reduce an alternative electron acceptor. However, the positive relationship between the two measured activities suggests that the abiotic activity may be due to reductant substances produced by micro-organisms. When sediments collected from the Carson River were used in laboratory assays for the determination of potential rates of MeHg production, the addition of inorganic Hg (added as HgCl2) resulted in increased rates of methylation when the spike concentration was lower or equal to 15.3 microg.g(-1) dry weight. This trend was reversed for spike concentration of inorganic Hg above 15.3 microg.g(-1). The reduction of methylation rate was associated with an inhibition of microbial activity. These observations suggest that seasonal inputs into the river of significant amounts of inorganic Hg eroded from mill tailings during winter and spring flooding events could have an inhibiting effect on Hg-methylating micro-organisms. This observation could explain the low [MeHg]/[HgT] ratios previously documented in waters of the Carson River system.

Catalyzed hydrogen peroxide treatment of octachlorodibenzo-p-oxin (OCCD) in surface soils

Abstract 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.