The majority of data were collected in the central Pacific ocean between 30 degree N and 30 degree S and 130 degree W and 155 degree W. During the KOROLEV cruise, a general symmetry in several aerosol optical and phys...
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(纸本)0444009477
The majority of data were collected in the central Pacific ocean between 30 degree N and 30 degree S and 130 degree W and 155 degree W. During the KOROLEV cruise, a general symmetry in several aerosol optical and physical parameters was observed for both Northern and Southern hemispheres centered on the Intertropical Convergence Zone, while a minima in aerosol mass concentration was observed for this region. An exception was observed for the fine particle size distribution as measured by an active scattering aerosol spectrometer probe.
In a search for the chemical and meteorological factors controlling rainwater composition the authors have demonstrated the performance of these techniques in the analysis of data consisting of rainwater samples colle...
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In a search for the chemical and meteorological factors controlling rainwater composition the authors have demonstrated the performance of these techniques in the analysis of data consisting of rainwater samples collected weekly at four sites in Western Washington State in 1982-83. The approach we have undertaken involves the identification of the underlying factors governing precipitation composition at individual sites supplemented by identification of the factors which link the local composition at different sites within a region. Major steps in this type of analysis include initial data scaling and transformation, outlier detection, determination of the underlying factors, and evaluation of the effect that experimental procedures may have on the variance of the results. Most of the calculations were performed with the ARTHUR software package.
Short-term (16 h) laboratory studies of 32P uptake by E. densa rooted in sediment demonstrated both foliar and root uptake, and that translocation occurred acropetally and basipetally. Root absorption is projected to ...
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Short-term (16 h) laboratory studies of 32P uptake by E. densa rooted in sediment demonstrated both foliar and root uptake, and that translocation occurred acropetally and basipetally. Root absorption is projected to provide 83-85% of total P uptake during 12-16 h photoperiod days. Measured foliar uptake and excretion rates suggest that there would be no net leakage of P into the water by undamaged actively-growing E. densa. Foliar uptake decreased and root uptake increased in the dark relative to rates under light.
Phenol and seven alkylphenols ( o -, m - and p -cresol, 2.5-, 2.6-, 3.4- and 3,5-dimethylphenol) were added at various concentrations to aliquots of domestic anaerobic sludge in Hungate serum bottles and these were in...
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Phenol and seven alkylphenols ( o -, m - and p -cresol, 2.5-, 2.6-, 3.4- and 3,5-dimethylphenol) were added at various concentrations to aliquots of domestic anaerobic sludge in Hungate serum bottles and these were incubated at 37°C. The concentration of methane in the headspace gas was monitored to determine if the phenolics were fermented to methane or if they inhibited the anaerobic process. Only phenol and p -cresol were fermented to methane. At 500 mg l −1 (but not at 300 mg l −1 ) 2,5-, 3,4- and 3,5-dimethylphenol reduced the rate and the amount of methane produced. The cresols were inhibitory at 1000 mg l −1 but not at 400 mg l −1 . In cultures supplemented with acetate and propionate (VOA), and in unsupplemented cultures, phenol at concentrations up to 500 mg l −1 was fermented to methane. Between 800 and 1200 mg l −1 phenol, methane production was neither enhanced nor inhibited relative to control cultures containing no phenol. Inhibition of methane production was evident when phenol was present at ⩾ 2000 mg l −1 . Thus the methanogens are less susceptible to phenol inhibition than are the phenol-degrading acid formers. In similar experiments with p -cresol: enhanced methane production was observed at concentrations of ⩽ 400 mg l −1 ; no enhancement or inhibition was observed at 600 mg l −1 ; and inhibition was noted when p -cresol was present at ⩾ 1000 mg l −1 .
A physicochemical model of the fate of toxic substances in the Great Lakes was constructed from mass balance principles, incorporating principal mechanisms of particulate sorption-desorption, sediment-water and atmosp...
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A physicochemical model of the fate of toxic substances in the Great Lakes was constructed from mass balance principles, incorporating principal mechanisms of particulate sorption-desorption, sediment-water and atmosphere-water interactions, and chemical and biochemical decay. The steady state mass balance model of the suspended solids in the open lake water yielded net solids loss rates from 0.02 m/day for Saginaw Bay to 1.22 m/day or Lake Ontario. Calibration of the toxic model was through comparison to 239Pu data collected in the 1970s using a 23 yr time variable calculation. In general, the sediments were interactive with the water column in the Great Lakes through resuspension and horizontal transport. Response times (50%) of 239Pu following a cessation of load extend beyond 10 yr with sediment resuspension. The calibrated model was also applied to polychlorinated biphenyl (PCB) using a high and low estimate of contemporary external load and with and without volatilization. The lower load level (lake range 640-1390 kg/yr) with volatilization (at an exchange rate of 0.1 m/day) was more representative of observed surface sediment data for the open lake waters. Calculated water column concentrations for the lower load level with and without volatilization ranged from 0.25-0.90 ng/l for open lake waters. Response times (50%) for PCB following cessation of load varied from < 5 yr when volatilization was included to 10-20 yr without volatilization. Comparison of these response times to decline of concentrations of PCB in Lake Michigan bloaters indicated that, at least for that lake, volatilization occurred at an exchange rate of .apprx. 0.1 m/day.
The extent of reversibility of PCB [polychlorinated biphenyl] bonding to sediments was characterized in studies on the partitioning behavior of hexachlorobiphenyl isomer. Linear nonsingular isotherms were observed for...
The extent of reversibility of PCB [polychlorinated biphenyl] bonding to sediments was characterized in studies on the partitioning behavior of hexachlorobiphenyl isomer. Linear nonsingular isotherms were observed for the adsorption and desorption of 2,4,5,2'',4,'',5''-hexachlorobiphenyl (HCBP) to 1100 ppm sediment suspensions. Partition coefficients, (.pi.l/kg), for desorption from lake sediments (Saginaw Bay, Lake Huron, Michigan) [USA] were substantially greater (.pi.d .apprx. 20,000-35,000) than those obtained for adsorption (.pi.a .apprx. 9000-14,000). HCBP was more weakly adsorbed to montmorillonite (.pi.a .apprx. 3000, .pi.d .apprx. 9000) and kaolinite (.pi.a .apprx. 1000, .pi.d .apprx. 3000) clay samples than to the natural sediment samples. Desorption results (.pi.d) for Saginaw Bay sediments were similar to .pi. values (15,000-35,000) calculated from field measurements of aqueous and particulate PCB concentrations. For Saginaw Bay sediments and clay minerals partitioning was correlated to sediment surface area and sediment organic content. A regression analysis using both variables explained .apprx. 90% of the observed variations. HCBP adsorption at ***. C (.pi.a .apprx. 14,000) was significantly greater than at ***. C (.pi.a .apprx. 6500) resulting in a calculated enthalpy of adsorption of +3.3 kcal/mol. Nonsingular isotherm behavior was not readily attributable to microbiological, kinetic or experimental effects. Evidence from consecutive desorption studies suggested that while HCBP adsorption may have been ultimately reversible, release from sediments probably involved desorption along 2 distinct isotherms. These results were interpreted in terms of possible similarities between the sorption properties observed in distilled water systems and PCB bonding processes in natural water systems.
Gaseous NH 3 and HNO 3 were continuously and rapidly removed from an aerosol containing small, aqueous solution droplets of NH 4 NO 3 (MMD = 0.4 μm), resulting in evaporation of the NH 4 NO 3 from the droplets. The r...
Gaseous NH 3 and HNO 3 were continuously and rapidly removed from an aerosol containing small, aqueous solution droplets of NH 4 NO 3 (MMD = 0.4 μm), resulting in evaporation of the NH 4 NO 3 from the droplets. The rate of evaporation was measured by following changes in the size distribution of the aerosol with time. The measured rates agree well with those predicted from existing theories of gaseous diffusion and concentrated solution chemistry. The resulting ‘evaporation’ coefficient for both NH 3 and HNO 3 was unity, implying that resistance to transport of molecules across the vapor-liquid interface is small. The observed rates imply negligible sampling errors from evaporation of NH 4 NO 3 in gas denuder tubes used in atmospheric measurements of HNO 3 and particulate nitrate compounds.
We report measurements taken in Houston, Texas of the chemical composition and degree of hydration of haze particles and compare these results with previously reported measurements taken in rural Virginia. Our in-situ...
We report measurements taken in Houston, Texas of the chemical composition and degree of hydration of haze particles and compare these results with previously reported measurements taken in rural Virginia. Our in-situ, real time measurements are based on detecting changes in particle light scattering extinction with changes in relative humidity and air temperature. With these methods we can determine fine particle mass and sulfate mass concentrations, and sulfate to ammonium ion molar ratio. In Houston, fine particle sulfate averaged 42 % of fine particle mass and the composition in terms of ammonium to sulfate molar ratio ranged from 0.5 to 2 with strong diurnal variation. The particles were most acid during the period 1500 to 2000 and neutral during 0200 to 0900. About 1 3 of the time the particles were droplets supersaturated in terms of salt content. In Virginia, the particles were on average more acidic and contained more water than those in Houston, but the particles were never observed to be supersaturated solution droplets. The difference in the hygroscopic behavior of the particles at the two sites is consistent with differences in both particle chemistry and ambient relative humidity.
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