Measurement and Modeling the Phase Partitioning of Organophosphate Esters Using Their Temperature-Dependent Octanol-Air Partition Coefficients and Vapor Pressures

Atmospheric concentrations of 11 organophosphate esters (OPEs) were measured in an urban area in Izmir, Turkey to explore their phase partitioning. Octanol-air partition coefficients (K-OA) and vapor pressures (P-L) of the OPEs were also measured as a function of temperature. Average Sigma 11OPE gas-phase concentrations were 1.77 +/- 0.84 and 4.00 +/- 1.77 ng/m(3), while particle-phase concentrations were 1.95 +/- 0.77 and 1.15 +/- 0.36 ng/m(3) during winter and summer, respectively. TCiPP1 dominated Sigma 11OPEs, followed by TnBP and TEP. OPE concentrations generally increased and shifted to gas-phase in the summer probably due to higher temperatures that favor partitioning to the gas-phase. Distribution between two phases covered a wide range from being primarily in gas-phase (TEP, TnBP) or particle-phase (EHDPP, TEHP, T2iPPP). Phase partitioning was also examined via four widely used models (K-OA, Soot, Steady-State, and pp-LFER). All models underestimated the majority of particle-gas partition coefficients (K-P) especially for the compounds having higher volatilities. Estimations based on the recently reported molecular weight of organic matter in urban aerosols (MWOM) and activity coefficients of OPEs in octanol (xi(OCT)) determined in the present study suggested that the basic assumptions of K-OA-based models (i.e., xi(OCT)/xi(OM) and MWOCT/MWOM = 1) are not valid

Confinement Effectiveness of CFRP in Axial Members under Various Loading Conditions

In this study, parameters affecting the mechanical properties of FRP-confined cylindrical and prismatic concrete columns were studied via experimental data, which were collected after an extensive literature review. The parameters were summarized as unconfined concrete strength, FRP thickness, cylinder diameter, overlap length of FRP, sustained stress level, heating-cooling effect and corner radius in prismatic specimens. Considering these parameters the confinement effectiveness is established analytically in the light of ultimate strength values obtained from the test results available in the literature. No steel reinforcement is taken into account because the main aim is to capture the behavior of FRP-confinement only. The analytical results revealed that unconfined concrete strength, FRP thickness, cross-sectional dimension of the specimen are the main parameters controlling the confinement effectiveness in cylindrical specimens. In addition to these parameters corner radius and sustained stress level are found to be significant in prismatic specimens

Spatial variations of linear and cyclic volatile methyl siloxanes in a river basin and their air-water exchange

Linear and cyclic volatile methylsiloxanes (VMS) are Si and O containing organic compounds that are increasingly subject to scientific studies in recent years. They are used as solvents and coating materials in personal care products, cleaning materials and industrial applications. In this study, it was aimed to investigate the spatial variations of VMS levels in river water and ambient air in Kucuk Menderes Basin and their air-water exchange patterns. Grab river water samples and passive ambient air samples collected from 10 sites throughout Kucuk Menderes Basin located in Izmir region in Turkey, and they were analyzed for VMS. The concentrations of Sigma VMS in river water and ambient air ranged from 48.4 to 148 ng L-1 and from 41.7 to 433 ng m(-3), respectively. Among the VMS compounds, the predominant compounds were found to be D5 and D3 in ambient air and river water, respectively. In general, concentrations of all VMS congeners increased towards downstream of the river for both water and ambient air samples and there were substantial fluctuations between the sampling points. These fluctuations may be due to wastewater discharges at some sites (increase), followed by loss by volatilization along the river (decrease). VMS concentrations measured in air and river water samples were used to estimate the net air-water exchange fluxes. In all cases, fluxes were negative, ranging between -159 (L4) and -11100 (D3) ng m(-2) day, indicating volatilization from water is a source for atmospheric VMS