Fate and Transport of Naproxen in a Sandy Aquifer Material: Saturated Column Studies and Model Evaluation

Naproxen-C₁₄H₁₄O₃ is a nonsteroidal anti-inflammatory drug which has been found at detectable concentrations in wastewater, surface water, and groundwater. Naproxen is relatively hydrophilic and is in anionic form at pH between 6 and 8. In this study, column experiments were performed using an unconsolidated aquifer material from an area near Barcelona (Spain) to assess transport and reaction mechanisms of Naproxen in the aquifer matrix under different pore water fluxes. Results were evaluated using HYDRUS-1D, which was used to estimate transport parameters. Batch sorption isotherms for Naproxen conformed with the linear model with a sorption coefficient of 0.42 (cm³ g^?1), suggesting a low sorption affinity. Naproxen breakthrough curves (BTCs) measured in soil columns under steady-state, saturated water flow conditions displayed similar behavior, with no apparent hysteresis in sorption or dependence of retardation (R, 3.85-4.24) on pore water velocities. Soil sorption did not show any significant decrease for increasing flow rates, as observed from Naproxen recovery in the effluent. Sorption parameters estimated by the model suggest that Naproxen has a low sorption affinity to aquifer matrix. Most sorption of Naproxen occurred on the instantaneous sorption sites, with the kinetic sorption sites representing only about 10 to 40% of total sorption.     

Modeling the Effect of Glucose Syrup on the Moisture Sorption Isotherm of Figs

Moisture sorption isotherms of figs with and without glucose syrup (at 20% and 40%, w/w) were determined at 5 °C, 25 °C, and 40 °C. A static gravimetric method was used under 0.11–0.84 water activity ranges for the determination of sorption isotherms that were found to be typical type ΙΙΙ for control sample. The inclusion of glucose syrup had significant effects on the sorption isotherms, and the moisture content of samples at each a _w decreased with increasing temperature. The experimental data were fitted well with two-parameter Brunauer–Emmet–Teller, three-parameter Guggenheim–Anderson–de Boer, and four-parameter Peleg models that all had R ² of greater than 0.99. The net isosteric heats of sorption were estimated using the Clausius–Clapeyron equation from the equilibrium data at different temperatures. It was found that the addition of glucose syrup significantly increased the amount of monolayer water and the isosteric heat of sorption. Both water activity and isosteric heat of sorption increased with glucose syrup level and the shape and status of sorption isotherms tend to change toward the typical sigmoid shape of most food systems.     

Biodegradation of atrazine in surface soils and subsurface sediments collected from an agricultural research farm

The purpose of the present study was to assess atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) mineralization by indigenous microbial communities and to investigate constraints associated with atrazine biodegradation in environmental samples collected from surface soil and subsurface zones at an agricultural site in Ohio. Atrazine mineralization in soil and sediment samples was monitored as ¹⁴CO₂ evolution in biometers which were amended with ¹⁴C-labeled atrazine. Variables of interest were the position of the label ([U-¹⁴C-ring]-atrazine and [2-¹⁴C-ethyl]-atrazine), incubation temperature (25°C and 10°C), inoculation with a previously characterized atrazine-mineralizing bacterial isolate (M91-3), and the effect of sterilization prior to inoculation. In uninoculated biometers, mineralization rate constants declined with increasing sample depth. First-order mineralization rate constants were somewhat lower for [2-¹⁴C-ethyl]-atrazine when compared to those of [U-¹⁴C-ring]-atrazine. Moreover, the total amount of ¹⁴CO₂ released was less with [2-¹⁴C-ethyl]-atrazine. Mineralization at 10°C was slow and linear. In inoculated biometers, less ¹⁴CO₂ was released in [2-¹⁴C-ethyl]-atrazine experiments as compared with [U-¹⁴C-ring]-atrazine probably as a result of assimilatory incorporation of ¹⁴C into biomass. The mineralization rate constants (k) and overall extents of mineralization (P _max ) were higher in biometers that were not sterilized prior to inoculation, suggesting that the native microbial populations in the sediments were contributing to the overall release of ¹⁴CO₂ from [U-¹⁴C-ring]-atrazine and [2-¹⁴C-ethyl]-atrazine. A positive correlation between k and aqueous phase atrazine concentrations (C _eq ) in the biometers was observed at 25°C, suggesting that sorption of atrazine influenced mineralization rates. The sorption effect on atrazine mineralization was greatly diminished at 10°C. It was concluded that sorption can limit biodegradation rates of weakly-sorbing solutes at high solid-to-solution ratios and at ambient surface temperatures if an active degrading population is present. Under vadose zone and subsurface aquifer conditions, however, low temperatures and the lack of degrading organisms are likely to be primary factors limiting the biodegradation of atrazine.     

Effect of temperature on ion content, ion fluxes and energy metabolism in Chara corallina

Abstract Effects of temperature on the ionic relations and energy metabolism of Chara corallina were investigated. Measurements were made of the ionic content, tracer ion fluxes, and photosynthetic and dark CO₂ fixation in isolated cells, and of O₂ exchange in photosynthesis and respiration in isolated shoot apices. The total intracellular concentration of K⁺, Na⁺ and Cl^? was the same in cells held for 5 days in non-growing medium at 15°C (the growth temperature) as in those held at 25°C or 5°C. The tracer influx in the light of all ions tested (Rb⁺, Na⁺, CH₃NH₃⁺, Cl^? and H₂PO₄^?) was lower at 5°C than at 15°C in experiments in which cells were subjected to 5°C for less than 24 h in toto. The influx at 25°C was greater than that at 15°C for H₂PO^?₄, there was no difference between the two temperatures for Na⁺, while the influx at 25°C was less than that at 15°C for Cl^?, Rb⁺ and CH₃NH₃⁺ For Cl^? and H₂PO^?₄ similar results were found in later experiments with cells grown at 20—23°C. Photosynthetic CO₂ fixation and O₂ evolution, and respiratory O₂ uptake, are greater at 25°C, and lower at 5°C, than they are at the growth temperature of 15°C. In longer-term pretreatments at the different temperatures, tracer Cl^? influx at 15°C and particularly at 25°C were lower than in short-term experiments, while the influx at 5°C was higher. It was concluded from these experiments, and from previous data on H⁺ free energy differences across the plasmalemma, that (1) the maintenance of internal ion concentrations involves a close balancing of influx and efflux of K⁺, Na⁺ and Cl^? at all experimental temperatures; (2) the regulation of the tracer fluxes of the ions is kinetic rather than thermodynamic and (3) that the tracer fluxes at low temperatures are not restricted by the rate at which respiration or photosynthesis can supply energy to them.     

Dilatometric Measurement of the Partial Molar Volume of Water Sorbed to Durum Wheat Flour

Moisture sorption isotherms were measured at 25 °C for untreated, dry-heated and pre-gelatinized durum wheat flour samples. The isotherms could be expressed by the Guggenheim-Anderson-de Boer equation. The amount of water sorbed to the untreated flour was highest for low water activity, with water sorbed to the pre-gelatinized and dry-heated flour samples following. The dry-heated and pregelatinized flour samples exhibited the same dependence of the moisture content on the partial molar volume of water at 25 °C as the untreated flour. The partial molar volume of water was ca. 9 cm³/mol at a moisture content of 0.03 kg-H₂O/kg-d.m. The volume increased with increasing moisture content, and reached a constant value of ca. 17.5 cm³/mol at a moisture content of 0.2 kg-H₂O/kg-d.m. or higher.     

The Influence of n-Propanol on the Growth and Conidiation of Pestalotia rhododendri

Pestalotia rhododendri was exposed to vapours from 1 ml propanol solution in water and linear growth, formation of aerial hyphae and production of conidia were determined. A special Petri dish technique was used and maximum stimulation of conidial formation was induced by the vapours from a propanol concentration of 3–4 % (v/v) at 25°C. When propanol was added directly to the medium, a concentration of 1.2 × 10^?2M was optimal for growth and sporulation at 30°C. Sporulation stimulated by propanol was observed at temperatures from 20–32°C, with an optimum at 30°C. Certain observations indicated that an exposure to propanol for 24 hours was enough to induce a stimulated spore production. The stimulation was noticed on different media at 25°C, and was more pronounced at 30°C. One exception was observed. Propanol did not promote sporulation when the fungus was grown on maltagar at 30°C. Propanol 3 ° (v/v) in combination with the standard medium containing (NH₄)₂-tartrate as sole nitrogen source, inhibited the linear growth at 15–20°C, was inactive at 22.5° and 25°C, and stimulated growth at 27.5–31°C. The stimulatory effect was maximal at 30°C. Other media were tested at 25° and 30°C. At both temperatures stimulations of linear growth caused by propanol were observed with a medium containing KNO₃ as sole nitrogen source, and inhibitions with maltagar and another medium containing l -asparaginc as sole nitrogen source. The linear growth could be either inhibited or stimulated while the sporulation was stimulated.     

Specific Surface Area Effect on Adsorption of Chlorpyrifos and TCP by Soils and Modelling

The adsorption of chlorpyrifos and TCP (3,5,6, trichloro-2-pyridinol) was determined in four soils (Mollisol, Inceptisol, Entisol, Alfisol) having different specific surface areas (19–84 m² g^?1) but rather similar organic matter content (2.4–3.5%). Adsorption isotherms were derived from batch equilibration experiments at 25°C. After liquid-liquid extraction, the chlorpyrifos and TCP concentrations in the solution phase were determined by gas chromatography with an electron capture detector. Adsorption coefficients were calculated using the Freundlich adsorption equation. High K_F coefficients for chlorpyrifos (15.78) and TCP (6.54) were determined for the Entisol soil, while low K_F coefficients for chlorpyrifos (5.32) and TCP (3.93) were observed in the Alfisol soil. In all four soils, adsorption of chlorpyrifos was higher than that of TCP. A surface complexation model, the constant capacitance model, was well able to fit the adsorption isotherms of both chlorpyrifos and TCP on all four soils. The results showed that specific surface area affected adsorption of both chlorpyrifos and TCP. Among the soil properties, specific surface area could be a better indicator than organic matter content alone for adsorption of chlorpyrifos and TCP by soils that contained low organic matter.     

Effects of acute temperature change on the metabolism and swimming ability of juvenile sterlet sturgeon (Acipenser ruthenus,Linnaeus 1758)

The objective of this study was to provide information on changes in the metabolism and swimming ability of juvenile sterlet sturgeon, Acipenser ruthenus, caused by acutely low or high temperatures. Changes in critical swimming speed (U_crit), oxygen consumption rate (MO₂), tail beat frequency (TBF) and tail beat amplitude (TBA) were observed with a Steffensen‐type swimming respirometer, an oxygen electrode and a camera at different swimming speeds at three temperatures: 5°C, 15°C, and 25°C. Fish tested at 5°C and 25°C were maintained at 15°C (near optimal) for one week to simulate conditions below a dam. The U_crit value decreased significantly during acute temperature changes at 5°C and 25°C; U_crit was highest near the optimal temperature. Oxygen consumption rate (MO₂) increased with the swimming speed at 15°C; however, at 25°C and 5°C, the MO₂ decreased with the swimming speed. Both TBA and TBF decreased at 5°C and 25°C compared to values at 15°C. The slopes of the regression lines (TBF/U) at 5°C and 25°C seemed lower compared to 15°C.     

Thermal effects on the biological parameters of the predatory mirid Pilophorus gallicus (Hemiptera: Miridae)

Pilophorus gallicus Remane (Hemiptera: Miridae) is a predatory mirid reported in deciduous trees in the western Mediterranean area. This work aimed to determine the biological and demographic parameters for this species at different temperatures (15, 20, 25 and 30°C). Egg hatching times shortened from 57.8 days at 15°C to 9.2 days at 30°C, and nymphal development times declined from 62.8 days at 15°C to 11.1 days at 30°C. The hatching and nymphal survival rates were low at 15 and 30°C. The lower thermal thresholds for the egg and nymphal development were 12.4 and 12.0°C, respectively. These high thermal thresholds could be a safety mechanism to avoid the emergence of nymphs in the unfavorable winter period. Female weight increased between 15 and 25°C and decreased at 30°C. The fecundity increased from 70.2 eggs per female at 15°C to 212.4 eggs per female at 25°C, and decreased to 88.5 eggs per female at 30°C. Fertility ranged from 9.4% at 15°C to 40.9% at 25°C, being 24.9% at 30°C. The intrinsic rate of natural increase (r_m) rose from 0.001 to 0.081 between 15 and 25°C and decreased to 0.05 at 30°C. In summary, this species performs poorly at low temperatures and has a relative tolerance of high temperatures (30°C); its performance was best at 25°C. Knowledge of the variation in the biological parameters with temperature may be very useful for the understanding of its ecology and population dynamics.     

Temperature effects on carbon and nitrogen metabolism in some Maritime Antarctic freshwater phototrophic communities

Biofilms growing on ice and benthic mats are among the most conspicuous biological communities in Antarctic landscapes and harbour a high diversity of organisms. These communities are consortia that make important contributions to carbon and nitrogen input in non-marine Antarctic ecosystems. Here, we study the effect of increasing temperatures on the carbon and nitrogen metabolism of two benthic communities on Byers Peninsula (Livingston Island, Maritime Antarctica): a biofilm dominated by green algae growing on seasonal ice, and a land-based microbial mat composed mainly of cyanobacteria. Inorganic carbon photoassimilation, urea and nitrate uptake and N₂-fixation (acetylene reduction activity) rates were determined in situ in parallel at five different temperatures (0, 5, 10, 15, 25°C) using thermostatic baths. The results for the cyanobacterial mat showed that photosynthesis and N₂-fixation responded positively to increased temperatures, but urea and NO₃⁻ uptake rates did not show a significant variation related to temperature. This microbial mat exhibits relatively low activity at 0°C whereas at higher temperatures (up to 15°C), N₂-fixation rate increased significantly. Similarly, the maximum photosynthetic activity increased in parallel with temperature and showed no saturation up to 25°C. In contrast, the ice biofilm displayed higher photosynthetic activity at 0°C than at the other temperatures assayed, and it showed elevated photoinhibition at warmer temperatures.     

The effects of temperature on swimming performance of juvenile shortnose sturgeon (Acipenser brevirostrum)

The swimming performance of juvenile shortnose sturgeon (～16 cm TL, ～20 g), Acipenser brevirostrum, was quantified with regards to temperature (5 to 25°C) using both increased (U_crit) and fixed velocity (endurance) tests in a laboratory setting. Sturgeons were found to show reduced U_crit values at 5 and 10°C (25.99 and 28.86 cm s^?1 respectively), with performance beginning to plateau at 15°C through 25°C (33.99 cm s^?1). For the endurance protocol, fish were tested at speeds of 35, 40 and 45 cm s^?1 at 5, 15 and 25°C. Performance within a single speed was similar at all temperatures, indicating the usage of anaerobic metabolism to fuel locomotion at these higher velocities. Overall, shortnose sturgeon demonstrated high tolerance towards a wide range of temperatures but showed few differences between performance levels at colder or warmer water conditions.     

Photosynthetic and respiratory responses of Gracilaria parvispora from the southeastern Gulf of California

Photosynthetic and respiratory responses (P–E curves) of Gracilaria parvispora from the southeast Gulf of California were studied at four temperatures (20, 25, 30, 35 °C) and salinity (25, 30, 35, 40 psu) combinations. The alga showed acclimation in its photosynthetic and respiratory responses to tropical temperature as well as to oceanic salinity. A positive effect of temperature on photosynthetic rate (P _max) was observed for all salinities. Photosynthetic rates for treatments at 20 and 25 °C were lower (<9.2 mg O₂?g dry weight (dw)^?1?h^?1) than for treatments at 30 and 35 °C (>12 mg O₂ g dw^?1?h^?1). G. parvispora showed limited tolerance to low salinities (25 psu) and low temperatures (20 °C) and the interaction between temperature and salinity was significant (analysis of variance, P?<?0.05). Responses to salinity indicated adaptation to oceanic salinity. Photosynthetic responses were lower at 25 psu than at higher salinities. The lowest P _max values (6.2–8.2 mg O₂?g dw^?1?h^?1) were observed at the lowest salinity (25 psu) regardless of temperature. Compensation and saturation irradiances (26–170 and 57–149 μmol photons m^?2?s^?1, respectively) indicate adaptation to lower irradiances in shallow (1–2 m depth) habitats, where turbidity can be high, and the capacity of shade adaptation has been developed. Results suggest distribution of this species is mainly related to salinity or temperature. The potential mariculture efforts of G. parvispora would be limited by low temperatures in winter, and indicate that this species will probably not be able to spread further due to low temperatures (<15 °C) in the upper part of the Gulf of California.     

Norfloxacin Sorption to Different Fractions in Sediments from Typical Water Systems in China

Sorption isotherms of Norfloxacin (NOF) to different fractions from six typical sediments in China were determined to compare the NOF sorption behavior and contribution of different fractions to total sorption. All sorption isotherms were nonlinear and fitted well with the Freundlich model. Sorption coefficients (K _f) by original sediments changed in larger magnitude, from 114 (mg/g)/(mg/L)ⁿ to 5271 (mg/g)/(mg/L)ⁿ, and black carbon with more aromatic carbon has more sorption capacity and nonlinearity. The sorption capacity K _f values were found to significantly correlate with SSA (specific surface area), OC (organic carbon), BC (black carbon), and TON (total organic nitrogen) (p < 0.05), but had no obvious relation with pH, CEC (cation exchange capacity), TOC/TON, and BC/TOC. The DOC removed, NaOH extracted, and 375°C heated fractions showed more nonlinear sorption than the original sediments, suggesting more heterogeneous sorption sites in these fractions. Among different sediment fractions, the 375°C heating fractions were responsible for >50% of the total NOF sorption over the whole concentration range. The contribution of DOC removed fractions to the total sorption was the highest at higher NOF concentration.     

Transgenic tobacco plants overexpressing a cold-adaptive nitroreductase gene exhibited enhanced 2,4-dinitrotoluene detoxification rate at low temperature

Abstract

Plants encounter many environmental factors such as low and high temperatures during phytoremediation processes. In this study, our aim was to produce the transgenic tobacco plants by using a newly characterized bacterial nitroreductase, Ntr, which was active at a broad range temperature in order to detoxify 2,4-dinitrotoluene (2,4-DNT) at lower temperature. The presence of Ntr and its heterologous expression was verified in T1 transgenic plants and their growing ability were determined under toxic amount of 2,4-DNT (35?µM). Fresh weight and dry weight of transgenic plants were significantly higher than wild type (WT) under toxic 2,4-DNT at 22?°C, indicating higher growth capacity of the transgenics. Transgenic plants also showed a higher tolerance than WT when exposed to 2,4-DNT at 15?°C. Moreover, transformation rate of 2,4-DNT was gradually decreased through decreasing temperatures in WT media, however, it was increased through decreasing temperatures in transgenic plant TR3-25 media and it had the highest transformation rate (54%) of 2,4-DNT at 4?°C. Correlatively, 2,4-DNT treatment at 4?°C led to a significant decrease in H₂O₂ level in transgenic plants. Thus, transgenic plants overexpressing nitroreductase might have an important advantage for phytoremediation of toxic nitroaromatic compounds in field applications at low temperatures.     

Photosynthetic performance and resistance to photoinhibition of Zea mays L. leaves grown at sub-optimal temperature

The performance of the photosynthetic apparatus was examined in the third leaves of Zea mays L. seedlings grown at near-optimal (25 °C) or at suboptimal (15 °C) temperature by measuring chlorophyll (ChI) a fluorescence parameters and oxygen evolution in different temperature and light conditions. In leaf tissue grown at 25 and 15 °C, the quantum yield of PSII electron transport (ψ_PSII) and the rate of O₂ evolution decreased with decreasing temperature (from 25 to 4 °C) at a photon flux density of 125 μmol m^?2 s^?1. In leaves grown at 25 °C, the decrease of ψ_PSII correlated with a decrease of photochemical ChI fluorescence quenching (q_p), whereas in leaves crown at 15 °C q_p was largely insensitive to the temperature decrease. Compared with leaves grown at 25 °C, leaves grown at 15 °C were also able to maintain a higher fraction of oxidized to reduced Q_A (greater q_p) at high photon flux densities (up to 2000 μmol m^?2 s^?1), particularly when the measurements were performed at high temperature (25 °C). With decreasing temperature and/or increasing light intensity, leaves grown at 15 °C exhibited a substantial quenching of the dark level of fluorescence F₀ (q₀) whereas this type of quenching was virtually absent in leaves grown at 25 °C. Furthermore, leaves grown at 15 °C were able to recover faster from photo inhibition of photosynthesis after a photoinhibitory treatment (1200 μmol m^?2 s^?1 at 25, 15 or 6 °C for 8 h) than leaves grown at 25 °C. The results suggest that, in spite of having a low photosynthetic capacity, Z. mays leaves grown at sub optimal temperature possess efficient mechanisms of energy dissipation which enable them to cope better with photoinhibition than leaves grown at near-optimal temperature. It is suggested that the resistance of Z. mays leaves grown at 15 °C to photoinhibition is related to the higher content of carotenoids of the xanthophyll cycle (violaxanthin + antheraxanthin + zeaxanthin) measured in these leaves than in leaves grown at 25 °C.     

The influence of temperature and nitrogen source on growth and nitrogen uptake of two polar-desert species,Saxifraga caespitosa and Cerastium alpinum

Polar-desert plants experience low average air temperatures during their short growing season (4–8 °C mean July temperature). In addition, low availability of inorganic nitrogen in the soil may also limit plant growth. Our goals were to elucidate which N sources can be acquired by polar-desert plants, and how growth and N-uptake are affected by low growth temperatures. We compared rates of N-uptake and increases in mass and leaf area of two polar-desert species (Cerastium alpinum L. and Saxifraga caespitosa L.) over a period of 3 weeks when grown at two temperatures (6 °C vs. 15 °C) and supplied with either glycine, NH₄ ⁺ or NO₃ ⁻. At 15 °C, plants at least doubled their leaf area, whereas there was no change in leaf area at 6 °C. Measured mean N-uptake rates varied between 0.5 nmol g⁻¹ root DM s⁻¹ on glycine at 15 °C and 7.5 nmol g⁻¹ root DM s⁻¹ on NH₄ ⁺ at 15 °C. Uptake rates based upon increases in mass and tissue N concentrations showed that plants had a lower N-uptake rate at 6 °C, regardless of N source or species. We conclude that these polar-desert plants can use all three N sources to increase their leaf area and support flowering when grown at 15 °C. Based upon short-term (8 h) uptake experiments, we also conclude that the short-term capacity to take up inorganic or organic N is not reduced by low temperature (6 °C). However, net N-uptake integrated over a three-week period is severely reduced at 6 °C. This revised version was published online in June 2006 with corrections to the Cover Date.     

Physiological responses of Opuntia ficus-indica to growth temperature

The influences of various day/night air temperatures on net CO₂ uptake and nocturnal acid accumulation were determined for Opuntia ficus-indica, complementing previous studies on the water relations and responses to photosynthetically active radiation (PAR) for this widely cultivated cactus. As for other Crassulacean acid metabolism (CAM) plants, net nocturnal CO₂ uptake had a relatively low optimal temperature, ranging from 11°C for plants grown at day/night air temperatures of 10°C/0°C to 23°C at 45°C/35°C. Stomatal opening, which occurred essentially only at night and was measured by changes in water vapor conductance, progressively decreased as the measurement temperature was raised. The CO₂ residual conductance, which describes chlorenchyma properties, had a temperature optimum a few degrees higher than the optimum for net CO₂ uptake at all growth temperatures. Nocturnal CO₂ uptake and acid accumulation summed over the whole night were maximal for growth temperatures near 25°C/15°C, CO₂ uptake decreasing more rapidly than acid accumulation as the growth temperature was raised. At day/night air temperatures that led to substantial nocturnal acid accumulation (25°C/15°C.). 90% saturation of acid accumulation required a higher total daily PAR than at non-optimal growth temperatures (10°C/0°C and 35°C/25°C). Also, the optimal temperature of net CO₂ uptake shifted downward when the plants were under drought conditions at all three growth temperatures tested, possibly reflecting an increased fractional importance of respiration at the higher temperatures during drought. Thus, water status, ambient PAR, and growth temperatures must all be considered when predicting the temperature response of gas exchange for O. ficus-indica and presumably for other CAM plants.     

Importance of Environmental Black Carbon to Dissolved Petroleum Hydrocarbons Sorption on Soil

Importance of environmental black carbon (BC) to sorption of dissolved petroleum hydrocarbons (DPH) on two soils with high BC:TOC ratios (33% and 11%, respectively) was evaluated at a relatively high concentrations (mg/L ～ μ g/L range). Sorption isotherms of DPH were determined for the two original soils and soils combusted at 375°C (only BC). The sorption isotherms of the original soils were linear, whereas the isotherms of the combusted soils were highly nonlinear (n _F = 0.45, 0.60). It is indicated that intrinsic BC-water sorption coefficient is not possible to be used to estimate total sorption to the original soil, even in our relatively high concentrations. From the sorption isotherms, Freundlich coefficient of environmental BC sorption, K _F,BC ^env of 10 ^{2.55 ± 0.21} was calculated and could be used as a generic starting point for environmental modeling purposes. From the data, it could be deduced that BC was responsible for 50% of the total sorption at concentrations of 45 and 4 μ g/L (μ g/L range), which were significantly higher than literature concentrations (ng/L range). These results demonstrate that in soil with high BC:TOC ratio BC is the most important geosorbent constituent with respect to sorption of DPH at relatively high concentrations ranged in μ g/L.     

Effect of temperature on germination,growth, and infectivity of the mosquito pathogen Tolypocladium cylindrosporum (deuteromycotina; hyphomycetes)

The mosquito pathogen Tolypocladium cylindrosporum was examined with regard to its response to temperature. Similar temperature ranges were found for growth, germination, and infectivity of blastospores and conidia. Germination occurred at 8° and 33°C but not at 6° and 35°C. Optimal germination and growth was noted between 24° and 27°C for both spore types. Infectivity of blastospores and conidia at different temperatures was examined by exposing L₂Aedes sierrensis larvae to concentrations of 5 × 10⁵ blastospores/ml or 5 × 10⁶ conidia/ml. Larvae were incubated at 12°, 15°, 25°, and 30°C. Infection occurred at all temperatures tested with LT₅₀ values ranging from 22.7 days (12°C) to 5.6 (25°C) days for conidia and 4.7 days (12°C) to 0.6 day (25°C) for blastospores. These results confirmed earlier findings that blastospores infected and killed host larvae more rapidly than conidia and suggested that this difference is largely due to the more rapid germination rate of blastospores. These experiments demonstrated that T. cylindrosporum can be active against mosquito larvae over a broad range of temperatures encompassing both the cold-water habitat of certain temperate mosquito species as well as the habitat of tropical vector species.     

The effects of development at sub-optimal growth temperatures on photosynthetic capacity and susceptibility to chilling-dependent photoinhibition in Zea mays

When plants of Zea mays L. cv. LG11 that have been grown at optimal temperatures are transferred to chilling temperatures (0–12°C) photoinhibition of photosynthetic CO₂ assimilation can occur. This study examines how growth at sub-optimal temperatures alters both photosynthetic capacity and resistance to chilling-dependent photoinhibition. Plants of Z. mays cv. LG11 were grown in controlled environments at 14, 17, 20 and 25°C. As a measure of the capacity for photosynthesis under light limiting conditions, the maximum quantum yields of CO₂ assimilation (φ^a.c) and O₂ evolution (φ^a.o) were determined for the laminae of the second leaves at photon fluxes of 50–150 μmol m^-2s^-1. To determine photosynthetic capacity at photon fluxes approaching light saturation, rates of CO₂ uptake (A₁₅₀₀) and O₂ evolution (A₁₅₀₀) were determined in a photon flux of 1500 μmol m^-2s^-1. In leaves developed at 14°C, φ and φ were 26 and 43%, respectively, of the values for leaves grown at 25°C. Leaves grown at 17°C showed intermediate reductions in φ and φ, whilst leaves developed at 20°C showed no significant differences from those grown at 25°C. Similar patterns of decrease were observed for A₁₅₀₀ and A_1500.0 with decreasing growth temperature. Leaves developed at 25°C showed higher rates of CO₂ assimilation at all light levels and measurement temperatures in comparison to leaves developed at 17 and 14°C. A greater reduction in A₁₅₀₀ relative to A_1500.0 with decreasing growth temperature was attributed to increased stomatal limitation. Exposure of leaves to 800–1000 μmol m^-2 s^-1 when plant temperature was depressed to ca 6.5°C produced a photoinhibition of photosynthetic CO₂ assimilation in all leaves. However, in leaves developed at 17°C the decrease in A₁₅₀₀ following this chilling treatment was only 25% compared to 90% in leaves developed at 25°C. Recovery following chilling was completed earlier in leaves developed at 17°C. The results suggest that growth at sub-optimal temperatures induces increased tolerance to exposure to high light at chilling temperatures. This is offset by the large loss in photosynthetic capacity imposed by leaf development at sub-optimal temperatures.