An experimentally practical and precise flocculation-based method was developed, tested, and applied to determine phenanthrene and 1,2,4-trichlorobenzene sorption with NIST SRM 2975 diesel ...particulate matter. Following an initial equilibration period, polyaluminum chloride (PACl) solution was added to the sorption tubes in order to facilitate the formation of flocculated aggregates of soot particles. After separation of the solids through centrifugation, supernatant concentrations were determined as with conventional batch methods. The flocculation-based method was tested on three kinds of soot and then used to evaluate sorption kinetics and equilibrium with SRM 2975. Kinetic results showed that wetting of the soot required more than 20 days, but that 60 days was sufficient to achieve equilibration with both water and phenanthrene. Sixty-day isotherms for both phenanthrene and 1,2,4-trichlorobenzene were strongly nonlinear. At approximate 10-3 of solubility, carbon-normalized distribution coefficients (Koc ) were 10−20 times higher than those for absorption to sediment organic matter. Measurements at closer to solubility indicated much lower Koc , suggesting a total sorption capacity at aqueous solubility that is of similar magnitude to that in sediment organic matter. Independent analysis of extractable hydrocarbons suggests that absorption into a native hydrocarbon phase was not a major component of sorption.
ABSTRACT We analyze the galactic cosmic ray (GCR) density and its spatial gradient in Forbush Decreases (FDs) observed with the Global Muon Detector Network (GMDN) and neutron monitors (NMs). By ...superposing the GCR density and density gradient observed in FDs following 45 interplanetary shocks (IP-shocks), each associated with an identified eruption on the Sun, we infer the average spatial distribution of GCRs behind IP-shocks. We find two distinct modulations of GCR density in FDs, one in the magnetic sheath and the other in the coronal mass ejection (CME) behind the sheath. The density modulation in the sheath is dominant in the western flank of the shock, while the modulation in the CME ejecta stands out in the eastern flank. This east-west asymmetry is more prominent in GMDN data responding to ∼60 GV GCRs than in NM data responding to ∼10 GV GCRs, because of the softer rigidity spectrum of the modulation in the CME ejecta than in the sheath. The geocentric solar ecliptic-y component of the density gradient, Gy, shows a negative (positive) enhancement in FDs caused by the eastern (western) eruptions, while Gz shows a negative (positive) enhancement in FDs caused by the northern (southern) eruptions. This implies that the GCR density minimum is located behind the central flank of IP-shocks and propagating radially outward from the location of the solar eruption. We also confirmed that the average Gz changes its sign above and below the heliospheric current sheet, in accord with the prediction of the drift model for the large-scale GCR transport in the heliosphere.
Protection of some poly(methyl methacrylate) samples against gamma rays has been investigated in the absence and presence of
N,N-dioxalyl
p-aminobenzene sulphonic acid and its iron (II)-complex. The ...pure PMMA (without additives), PMMA-ligand and PMMA-iron complex composite samples were irradiated with gamma rays for different exposure doses (5, 15, 25, 35, 50, 75 and 100 KGy). Viscosity average molecular weights (
M
v
-values) and thin layer Chromatographic measurements were carried out after each irradiation dose.
The maximum protection against gamma ray is found when 7% of the organic ligand or its iron complex is used in the polymer matrix. The radiation chemical yield for main chain scission (
Gs) is calculated and has its lower values in the case of the organic ligand which means that the protection is stronger in the case of the organic ligand than its iron complex. From TLC studies, it is noticed that both the
R
f
-values and polydispersity of the PMMA samples increase with increasing exposure dose.
The transport of polycyclic aromatic hydrocarbons (PAH) in porous media in the presence of dissolved organic matter (DOM) was predicted with a transport bicontinuum model using independently obtained ...relationships to derive transport parameters for describing the effect of PAH binding to the DOM.
The sorption constants of PAHs to soil and their binding constants to DOM were derived from basic correlations with
K
ow (indicator of hydrophobicity). The kinetic (rate) constants were derived from previously published correlations with
K
p (sorption constant). The independently obtained sorption and rate constants were corrected for binding to DOM and were used to predict the breakthrough curves (BTC) of contaminants in the presence and the absence of DOM.
Column results confirmed the independently predicted BTC of PAHs in the presence of DOM that did not sorb to the solid phase, as well as the effect of DOM on the rate of the sorption and desorption processes. These findings confirm the ability to quantitatively describe how DOM facilitates transport of contaminants in the subsurface using independently derived parameters.
New modified alkyd varnishes were prepared by partial replacement of phthalic anhydride with methylene disalicylic acid. Incorporation of this phenolic derivative led to significant improvement in ...hardness, gloss, and alkali resistance performance.
We examine the deviation of the solar diurnal anisotropy vector from the 18 LT direction during the positive state of the solar cycle by assuming two anisotropies in free space. We use two detectors ...characterized by two linearly independent coupling functions. The median primary rigidity of response of these detectors covers the range 16 GV ≤ R^sub m^ ≤ 331 GV. Amplitude, direction, spectrum exponent, and the upper cut-off rigidity of each anisotropy have been calculated using the least-squares method over the time interval 1968-1988. This period covers a complete solar magnetic cycle. Only one anisotropy is dominant during each magnetic state of the solar cycle. The upper cut-off rigidity at which the dominant anisotropy vanishes varies between 50-250 GV. The direction of the dominant anisotropy vector points toward the 18 LT direction during the negative state of the solar cycle and toward earlier hours than 18 LT during the positive state. The non-dominant anisotropy is characterized by very high upper cut-off rigidity and sharper energy spectral.PUBLICATION ABSTRACT
Aerosol optical measurements acquired with satellite–borne TERRA/Moderate Resolution Imaging Spectro–radiometer (MODIS) sensor were analyzed over Kuwait. The study focuses on the seasonal variation ...of aerosol optical thickness (AOT) and their relationship with meteorological parameters during the 7–year period from 2000 through 2007. The mean values of AOT, wind speed (V), air temperatures (T), diurnal temperature range (AT) and water vapor content (WVC) in the near-infrared (NIR) region were high during spring (April–May), while those of the Angstrom wavelength exponent α were low. These low values of α indicate the presence of large aerosol particles (dust). Spectral analysis shows a significant annual variation in the AOT and meteorological parameters. The second (semi–annual), third (4–month) and fourth (3–month) harmonics of the annual variation are also evident. The fourth harmonic is well defined in WVC (NIR) spectra. The power spectral densities of the exponent α, ΔT and RH have a similar spectral power ~1.9. The cross–correlation functions between the time series of the wavelength exponent and each of the meteorological parameters exhibit annual and biennial cycles. The atmosphere over Kuwait is relatively dust free 3 months after WVC (NIR) peaks.
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