Near-source air quality impacts of large olefin flares

Large petrochemical flares, common in the Houston Ship Channel (the Ship Channel) and other industrialized areas in the Gulf of Mexico region, emit hundreds to thousands of pounds per hour of highly reactive volatile organic compounds (HRVOCs). We employed fine horizontal resolution (200 m?×?200 m) in a three-dimensional (3D) Eulerian chemical transport model to simulate two historical Ship Channel flares. The model reasonably reproduced the observed ozone rise at the nearest monitoring stations downwind of the flares. The larger of the two flares had an olefin emission rate exceeding 1400 lb/hr. In this case, the model simulated a rate of increase in peak ozone greater than 40 ppb/hr over a 12 km?×?12 km horizontal domain without any unusual meteorological conditions. In this larger flare, formaldehyde emissions typically neglected in official inventories enhanced peak ozone by as much as 16 ppb and contributed over 10 ppb to ambient formaldehyde up to ～8 km downwind of the flare. The intense horizontal gradients in large flare plumes cannot be simulated by coarse models typically used to demonstrate ozone attainment. Moreover, even the relatively dense monitoring network in the Ship Channel may not be able to detect many transient high ozone events (THOEs) caused by industrial flare emissions in the absence of stagnant air recirculation or stalled sea breeze fronts, even though such conditions are unnecessary for the occurrence of THOEs.

Implications: Flare minimization may be an important strategy to attain the U.S. federal ozone standard in industrialized areas, and to avoid inordinate exposure to formaldehyde in neighborhoods surrounding petrochemical facilities. Moreover, air quality monitoring networks, emission inventories, and chemical transport models with higher spatial and temporal resolution and more refined speciation of HRVOCs are needed to better account for the near-source air quality impacts of large olefin flares.     

Near-source air quality impacts of large olefin flares

Large petrochemicalflares, common in the Houston Ship Channel (the Ship Channel) and other industrialized areas in the Gulfof Mexico region, emit hundreds to thousands of pounds per hour of highly reactive volatile organic compounds (HRVOCs). We employedfine horizontal resolution (200 mx200 m) in a three-dimensional (3D) Eulerian chemical transport model to simulate two historical Ship Channel flares. The model reasonably reproduced the observed ozone rise at the nearest monitoring stations downwind of the flares. The larger of the two flares had an olefin emission rate exceeding 1400 lb/hr. In this case, the model simulated a rate of increase in peak ozone greater than 40 ppb/hr over a 12 kmx12 km horizontal domain without any unusual meteorological conditions. In this larger flare, formaldehyde emissions typically neglected in official inventories enhanced peak ozone by as much as 16 ppb and contributed over 10 ppb to ambient formaldehyde up to approximately 8 km downwind of the flare. The intense horizontal gradients in large flare plumes cannot be simulated by coarse models typically used to demonstrate ozone attainment. Moreover even the relatively dense monitoring network in the Ship Channel may not be able to detect many transient high ozone events (THOEs) caused by industrial flare emissions in the absence of stagnant air recirculation or stalled sea breeze fronts, even though such conditions are unnecessary for the occurrence of THOEs.     

Uncertainty requirements of the European Union’s Industrial Emissions Directive for monitoring sulfur dioxide emissions: Implications from a blind comparison of sulfate measurements by accredited laboratories

When annual average PM_2.5 (fine particulate matter sized 2.5 microns and less) data for 2005 became available in April 2006 and the 3-yr average PM_2.5 concentration in an area just north of the Houston Ship Channel reached 15.0 µg/m³, the Texas Commission on Environmental Quality (TCEQ) initiated daily collection of quartz fiber as well as Teflon PM_2.5 filter samples for chemical speciation analysis. The purpose of the chemical speciation analysis was to use the speciation data, together with meteorological data and hourly TEOM (tapered element oscillating microbalance) PM_2.5 mass data, to identify the causes of the high PM_2.5 concentrations affecting the monitoring site and the neighborhood. The ultimate purpose was to target emission reduction efforts to sources contributing to the high measured PM_2.5 concentrations. After a year of data collection, it was recognized that a specific source, unpaved driveways and loading areas along the Ship Channel and dirt tracked onto Clinton Drive, the main artery running east-west north of the Ship Channel, were the primary cause for the Clinton Drive site's measuring PM_2.5 concentrations significantly higher than other sites in Houston. The source characterization and remediation steps that have led to sustained reduced concentrations are described in this paper.

Implications: With PM_2.5 exceedances it can be essential to have or develop chemical speciation data as part of the process of identifying the source types causing exceedances of an annual standard. Positive matrix factorization (PMF) analysis proved to be a powerful tool that identified the two locally emitted species contributing to exceedances, which did not occur at other sites in the region. They were calcium sulfate (gypsum), an industrial by-product, and soil minerals. Other data analysis approaches were necessary to distinguish North African dust events, which PMF failed to identify.     

The use of conditional probability functions and potential source contribution functions to identify source regions and advection pathways of hydrocarbon emissions in Houston,Texas

In this study, we demonstrate the utility of conditional probability functions (CPFs), potential source contribution functions (PSCFs), and hierarchical clustering analysis (HAC) to identify the source region and transport pathways of hydrocarbons measured at five photochemical assessment monitoring stations (PAMS) near the Houston Ship Channel from June to October 2003. In contrast to scatter plots, which only show the pair-wise correlation of species, commonality in CPF figures shows both correlation and information on the source region of the species in question. In this study, we use over 50 hourly volatile organic compound (VOC) concentrations and surface wind observations to show that VOCs with similar CPF patterns likely have common transport pathways. This was established with the multivariate technique, which uses the hierarchical clustering analysis to define clusters of VOCs having similar CPF patterns. This method revealed that alkenes, and in particular those with geometric isomers such as cis-/trans-2-butene and cis-/trans-2-pentene, have similar CPF patterns and hence, a common area of origin. The alkane isomers often show CPF patterns among themselves, and similarly, aromatic compounds often show similar patterns. We also show how calculated trajectory information can be used in the PSCF analysis to produce a graphic picture that identifies specific geographic areas associated with a given VOC (or other pollutant). The use of these techniques in the chemically and meteorologically complex environment of Houston, Texas, suggests its further utility in other areas with relatively simpler conditions.     

Evaluation of air quality models for the simulation of a high ozone episode in the Houston metropolitan area

A high ozone event in the Houston–Galveston–Brazoria area was utilized to study the shortcomings of the current air quality models. To improve the baseline simulations with the Comprehensive Air quality Model with Extensions (CAMx) for developing the state implementation plan, the Texas Commission on Environmental Quality (TCEQ) imputed emissions of highly reactive volatile organic compounds (HRVOCs) by scaling the amount of fugitive emissions of olefins to co-emitted NO_x from selected point sources, effectively multiplying by 3–12 times over the regular inventory values. In this paper, CAMx and the Community Multiscale Air Quality (CMAQ) model were used to determine if the imputed HRVOC emissions were consistent with the observed atmospheric conditions. With the base emissions, CMAQ and CAMx both with the Carbon-Bond 4 (CB-4) mechanism simulated similar ozone concentrations. But with the imputed HRVOC emissions, CMAQ predicted lower ozone peaks than CAMx in the vicinity and downwind of the Ship Channel and other highly HRVOC-rich areas. Based on analyses of sensitivity simulations of CMAQ with different emission inputs and vertical diffusion algorithms in the model, we found that the modeled atmosphere lacked reactivity to produce the observed high ozone event. Although the imputed HRVOC emissions improved ozone prediction at the surface sites, but the ethylene concentrations were not consistent with the measurements at the super sites (La Porte and Clinton) and by NOAA aircraft. Several sensitivity tests designed to provide additional radicals into the system and other research results suggested that the lack of reactivity may need to be corrected by targeted, and probably of episodic, increase of HRVOC emissions, from the sources in the Houston Ship Channel. Additional investigation of the ozone production efficiency for different chemical mechanisms is necessary to pinpoint the emissions uncertainty issues.     

Molecular composition of organic fine particulate matter in Houston,TX

Organic fine particulate matter collected in Houston, TX between March 1997 and March 1998 was analyzed to determine the concentration of individual organic compounds. Samples from four sites were analyzed including two industrial locations (Houston Regional Monitoring Corporation (HRM-3) site in Channelview and Clinton Drive site near the Ship Channel Turning Basin), one suburban location (Bingle Drive site in Northwest Houston) and one background site (Galveston Island). At the three urban locations, samples were divided into three seasonal sample aggregates (spring, summer and winter), while at the background site a single annual average sample pool was used. Between 10 and 16 individual samples were pooled to get aggregate samples with enough organic carbon mass for analysis. Overall, 82 individual organic compounds were quantified. These include molecular markers which are compounds unique to specific fine particle sources and can be used to track the relative contribution of source emissions to ambient fine particle levels. The differences both spatially and temporally in these tracers can be used to evaluate the variability in emission source strengths.     

Extensive aerosol optical properties and aerosol mass related measurements during TRAMP/TexAQS 2006 – Implications for PM compliance and planning

Extensive aerosol optical properties, particle size distributions, and Aerodyne quadrupole aerosol mass spectrometer measurements collected during TRAMP/TexAQS 2006 were examined in light of collocated meteorological and chemical measurements. Much of the evident variability in the observed aerosol-related air quality is due to changing synoptic meteorological situations that direct emissions from various sources to the TRAMP site near the center of the Houston-Galveston-Brazoria (HGB) metropolitan area. In this study, five distinct long-term periods have been identified. During each of these periods, observed aerosol properties have implications that are of interest to environmental quality management agencies. During three of the periods, long range transport (LRT), both intra-continental and intercontinental, appears to have played an important role in producing the observed aerosol. During late August 2006, southerly winds brought super-micron Saharan dust and sea salt to the HGB area, adding mass to fine particulate matter (PM_2.5) measurements, but apparently not affecting secondary particle growth or gas-phase air pollution. A second type of LRT was associated with northerly winds in early September 2006 and with increased ozone and sub-micron particulate matter in the HGB area. Later in the study, LRT of emissions from wildfires appeared to increase the abundance of absorbing aerosols (and carbon monoxide and other chemical tracers) in the HGB area. However, the greatest impacts on Houston PM_2.5 air quality are caused by periods with low-wind-speed sea breeze circulation or winds that directly transport pollutants from major industrial areas, i.e., the Houston Ship Channel, into the city center.     

Concentrations of polychlorinated biphenyls (PCBs) in water, sediment, and aquatic biota in the Houston Ship Channel, Texas

Polychlorinated biphenyls (PCBs) were quantified in water, sediment, and catfish and crab tissue collected from the Houston Ship Channel (HSC) in Texas. The total concentrations of the 209 PCB congeners ranged from 0.49 to 12.49 ng l(-1), 4.18 to 4601 ng g(-1) dry wt, 4.13 to 1596 ng g(-1) wet wt, and 3.44 to 169 ng g(-1) wet wt, in water, sediment, catfish and crab tissue, respectively. All media showed maximum concentrations greater than studies in other regions with the highest concentrations occurring in the most industrialized segments of the channel. Inter-media correlations suggested that sediment is a source to water. Galveston Bay sediment concentrations compared to a previous study showed a declining trend though the rate of the decline may be slowing. Detailed homolog profiles revealed that the industrialized part of the channel may be receiving PCB-laden sediment from its tributaries. An unusually high fraction of the deca-chlorinated congener (PCB-209) was found in all media. Seen in only a few other studies and in previous air concentrations in the channel, this may point to unusual Aroclor mixtures used in the history of the HSC or to contemporary sources from local industry. A comparison of PCB concentrations obtained using Aroclor, representative congener, and all congener methods, indicated that Aroclors are not an appropriate surrogate for total PCBs and that the NOAA NST method is more representative than the NOAA EPA method.     

Degradation of bisphenol-A (BPA) in the presence of reactive oxygen species and its acceleration by lipids and sodium chloride

In this study, (1) change in bisphenol-A (BPA) leached from polycarbonate (PC) tube to water samples at 37 degrees C, (2) effect of reactive oxygen species (ROS) produced by Fenton reaction on BPA recovery and thiobarbituric acid (TBA) value with or without generally existing environmental substances such as alcohol, lipids and NaCl, were investigated. Amounts of BPA leached from PC tube to water samples containing lipids possessing unsaturated fatty acid with high TBA values were significantly lower than the amount of BPA to water only, and addition of NaCl to lipid containing water further decreased BPA concentration. The result indicates that BPA could be degraded by lipoperoxides formed by auto-oxidation of lipid, and NaCl plays an important role in BPA degradation. In the presence of ROS, BPA recovery was the lowest in water and addition of EtOH increased in both BPA recovery and TBA value, suggesting that EtOH could play a role as scavenger of ROS on the oxidative BPA degradation. Furthermore, the higher the concentration of lipid and/or NaCl, the lower the BPA recovery and TBA value. Physiologically and environmentally important concentrations of NaCl could enhance oxidative degradation of BPA in the presence of ROS.     

Spatiotemporal distribution of water environmental capacity—a case study on the western areas of Taihu Lake in Jiangsu Province,China

Currently, the poor water quality in Taihu Lake is a major problem in China, so pollution control in the upstream areas has become a government priority. In Jiangsu Province, pollution emissions around the western areas of Taihu Lake, including Changzhou Municipality and Yixing City, need to be highly restricted, and calculating the water environmental capacity is important if pollution is to be reduced. In this study, 19 control units in these areas were established, and a 0-D mathematical model was used to calculate the water environmental capacity. For three important control units with important cross sections, a 1-D model was established to redress the results. Finally, the total maximum monthly loads of each control unit were obtained using temporal allocation principles. The results suggested that (1) the total pollution control of chemical oxygen demand was 58,894.2 tonnes per annum (t a^?1), with ammonia nitrogen, total nitrogen, and total phosphorus amounting to 3,808, 6,054.6, and 386.6 t a^?1, respectively; (2) water environmental capacity per unit water area in the ambient control units was smaller than that in the middle control units; and (3) the largest water environmental capacity was in June, and the smallest capacity was in December. The study provides important information for local governments, which will enable them to implement pollution control strategies that will improve the water quality in Taihu Lake.     

Comparisons of polychromatic and monochromatic UV-based treatments of bisphenol-A in water via toxicity assessments

Polychromatic ultraviolet irradiation, such as from medium pressure (MP) Hg lamps may enhance the UV degradation of environmental pollutants as compared to low pressure (LP) Hg UV sources emitting monochromatic irradiation. Typically, studies involving destruction of environmental pollutants such as endocrine disrupting compounds (EDCs) are based on measurement of the parent compound decay using analytical chemistry, but such information is insufficient to determine an effective treatment endpoint because the identity and biological activity of many transformation products remain unknown. Bioanalytical methods to assess residual biological activity of a treated water offers one means to compare removal efficiency of EDC activity between MP- and LP-UV lamps under photolysis and UV/H2O2 oxidation. In this study, changes in estrogenic activity of bisphenol-A (BPA) as a function of UV treatment were evaluated using both an in vitro yeast estrogen screen and in vivo vitellogenin assay with Japanese medaka (Oryzias latipes) fish. Decay of BPA parent compound and formation of degradation products were followed using HPLC analysis. Results demonstrated that MP-UV direct photolysis more effectively removed BPA and associated estrogenic activity compared to LP-UV lamps. UV in combination with H2O2 significantly removed estrogenic activity in vitro and in vivo compared to direct photolysis; however, no significant difference in removal rates was found between the two lamps under UV/H2O2 oxidation. Furthermore, the UV/H2O2 process was effective for reducing embryo toxicity of BPA, but resulted in the production of acidic intermediates, causing acute toxicity and delayed hatching in some medaka embryos.     

Leaching of bisphenol A (BPA) to seawater from polycarbonate plastic and its degradation by reactive oxygen species

In this study, (1) change in the concentration of bisphenol A (BPA) leached from polycarbonate (PC) tube to control water (BPA free), seawater and river water at 20 and 37 degrees C as a function of time, (2) the fate of BPA caused by addition of H(2)O(2) and Fe(3+) to seawater containing BPA leached from PC tube were assessed. BPA leached from PC tube to all water samples increased with the ascendant of temperature and with the passage of time. The BPA leaching velocity in seawater was the fastest in three samples (11 ng/day for seawater, 4.8 ng/day for river water 0.8 ng/day for control water at 37 degrees C).BPA leaching velocity from PC tube was significantly high at pH 8 (50 mM Na(2)HPO(4)) and increased dose-dependently. There was no difference in the velocity of BPA among the 50 mM phosphate-buffers at pH 6.5, 7.0 and 7.5. BPA was leached three times higher by addition of Na(+) than K(+). However, the higher the K(+) concentration, the larger the BPA leached from PC tube. Na(+) mixed with PO(4)(-) was effective on BPA leaching from PC tube, but not with SO(4)(-) or Cl(-). The results suggested that BPA leaching from PC tube would be attributed to the concentration of bibasic phosphate such as Na(2)HPO(4) and K(2)HPO(4) in water samples. BPA was degraded in both control water and seawater in the presence of radical oxygen species, but the degradation rate was lower in seawater than in control water, suggesting that anti-oxidative system exists in seawater. Neo-synthesized substance in both control water and seawater in the presence of reactive oxygen species was identified as BPA-quinone by LC-MS.     

Sorption and degradation of pharmaceuticals and personal care products (PPCPs) in soils

Pharmaceuticals and personal care products (PPCPs) are one class of the most urgent emerging contaminants, which have drawn much public and scientific concern due to widespread contamination in aquatic environment. Most studies on the environmental fate and behavior of PPCPs have focused on nonsteroidal anti-inflammatory drugs. Some other compounds with high concentrations were less mentioned. In this study, sorption and degradation of five selected PPCPs, including bisphenol A (BPA), carbamazepine (CBZ), gemfibrozil (GFB), octylphenol (OP), and triclosan (TCS) have been investigated using three different soils. Sorption isotherms of all tested PPCPs in soils were well described by Freundlich equation. TCS and OP showed moderate to strong sorption, while the sorption of GFB and CBZ in soils was negligible. Degradation of PPCPs in three soils was generally fitted first-order exponential decay model, with half-lives (t _1/2) varying from 9.8 to 39.1 days. Sterilization could prolong the t _1/2 of PPCPs in soil, indicating that microbial activity played an important role in the degradation of these chemicals in soils. Degradation of PPCPs in soils was also influenced by the soil organic carbon (f _oc) contents. Results from our data show that sorption to the soils varied among the different PPCPs, and their sorption affinity on soil followed the order of TCS > OP > BPA > GFB > CBZ. The degradation of the selected PPCPs in soil was influenced by the microbial activity and soil type. The poor sorption and relative persistence of CBZ suggest that it may pose a high leaching risk for groundwater contamination when recycled for irrigation.     

Biological assessment of bisphenol A degradation in water following direct photolysis and UV advanced oxidation

Endocrine disrupting compounds (EDCs) are exogenous environmental chemicals that can interfere with normal hormone function and present a potential threat to both environmental and human health. The fate, distribution and degradation of EDCs is a subject of considerable investigation. To date, several studies have demonstrated that conventional water treatment processes are ineffective for removal of most EDCs and in some instances produce multiple unknown transformation products. In this study we have investigated the use of direct photolysis with low-pressure (LP) Hg UV lamps and UV+hydrogen peroxide (H(2)O(2)) advanced oxidation process (AOP) for the degradation of a prototypic endocrine disrupter, bisphenol A (BPA), in laboratory water. Removal rates of BPA and formation of degradation products were determined by high performance liquid chromatography (HPLC) analysis. Changes in estrogenic activity were evaluated using both in vitro yeast estrogen screen (YES) and in vivo vitellogenin (VTG) assays with Japanese medaka fish (Oryzias latipes). Our results demonstrate that UV alone did not effectively degrade BPA. However, UV in combination with H(2)O(2) significantly removed BPA parent compound and aqueous estrogenic activity in vitro and in vivo. Removal rates of in vivo estrogenic activity were significantly lower than those observed in vitro, demonstrating differential sensitivities of these bioassays and that certain UV/AOP metabolites may retain estrogenic activity. Furthermore, the UV/H(2)O(2) AOP was effective for reducing larval lethality in treated BPA solutions, suggesting BPA degradation occurred and that the degradation process did not result in the production of acutely toxic intermediates.     

Leaching of bisphenol A (BPA) from polycarbonate plastic to water containing amino acids and its degradation by radical oxygen species

In this study, (1) the change in the concentration of bisphenol A (BPA) leached from polycarbonate plastic (PCP) tube to water samples containing phosphate, sodium barbital, glycine, methionine or albumin at 37 degrees C as a function of time, and (2) the degradation rate of BPA leached from PCP tube to amino acid solutions in the presence of radical oxygen species (ROS) were investigated. The BPA leaching velocity (BPA-LV) from PCP tube to 50 mM glycine at pH 6 or 7 was twice that to control water, and the leaching was enhanced above pH 8. At pH 11, BPA-LV was significantly higher in 50 mM glycine and methionine solutions than in 50 mM NaOH. These results indicate that basic pH and amino acids contained in water could accelerate BPA leaching. The BPA-LV in phosphate buffer was different from the BPA-LVs in other buffers (barbital and glycine) at the same pH. BPA leached to the glycine or methionine solutions at pH 11 was degraded time dependently in a similar manner as the control water in the presence of ROS. The degradation of leached BPA was inhibited in the glycine solution, but was accelerated in the methionine solution. However, degradation of BPA added to freshly prepared methionine was inhibited in a similar manner to BPA in glycine. BPA degradation could be influenced by some kinds of amino acids, but glycine and methionine might be involved in BPA degradation in different ways.     

Duo-molecularly imprinted polymer-coated magnetic particles for class-selective removal of endocrine-disrupting compounds from aqueous environment

The removal of steroid and phenolic endocrine-disrupting compounds (EDCs) from an aqueous environment was investigated using magnetic particles encapsulated by a duo-molecularly imprinted polymer (duo-MIP). The effect of environmental variables on the binding efficiency was studied. Experimental results showed that the amount of EDCs adsorbed was neither affected by up to 10.0 mM NaCl nor significantly interfered by up to 10.0 mg/L humic acid. Negligible influence was observed from pH 3.3 to pH 6.8, but a decrease started at pH 9. Freundlich isotherm parameters indicated binding capacities in the order of DES?>?E2?～?E1?>?BPA. The applicability of class-selective removal was verified using river water samples spiked with these EDCs at 10 μg/L; the binding efficiencies were 90, 90, 88, and 98 % for estrone (E1), 17β-estradiol (E2), bisphenol A (BPA), and diethylstilbestrol (DES), respectively. A reuse investigation verified constant binding capacities exhibiting <2 % reduction after seven cycles of regeneration.     

Mercury species measured atop the Moody Tower TRAMP site,Houston, Texas

Atmospheric mercury speciation was monitored within Houston, Texas, USA, August 6–October 14, 2006 as part of the TexAQS Radical and Aerosol Measurement Program (TRAMP). On average, all mercury levels were significantly elevated compared to a rural Gulf of Mexico coastal site. Concentrations varied from very clean to very dirty. Multi-day periods of stagnant or low-wind conditions brought elevated concentrations of all mercury species, whereas multi-day periods of strong winds, particularly southerly winds off the Gulf of Mexico, brought very low values of mercury species. Over the entire mercury measurement period, the daily averages of mercury species showed distinct and consistent relationships with the average planetary boundary layer dynamics, with gaseous elemental and particulate-bound mercury near-surface concentrations enhanced by a shallow nocturnal boundary layer, and reactive gaseous mercury concentration enhanced by midday convective boundary layer air entrainment transporting air aloft to the surface. Mercury concentrations were not significantly correlated with known products of combustion, likely indicating non-combustion mercury sources from the Houston area petrochemical complexes. On the morning of August 31, 2006 an observed emission event at a refinery complex on the Houston Ship Channel resulted in extremely high concentrations of aerosol mass and particulate-bound mercury at the TRAMP measurement site 20 km downwind.     

Distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans in suspended sediments, dissolved phase and bottom sediment in the Houston Ship Channel

Spatial distributions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in the water column and bottom sediments of the Houston Ship Channel in Texas were measured three times over a 1-year period. Total TEQ concentrations in water ranged from 0.01 to 0.25 pg/l for the dissolved phase and from 0.09 to 2.91 pg/l for the suspended phase, while TEQ concentrations in bottom sediments varied from 0.9 to 139.8 ng/kg dry wt. The dissolved concentrations were lower than their respective suspended concentrations, with average dissolved/suspended ratios between 0.11 and 0.59 for individual congeners. More than 89% of the total concentration of 2378-substituted PCDD/PCDFs was attributable to OCDD but 2378-TCDD was the major contributor to total TEQ for the three sampled media. Average logs of organic carbon-normalized suspended sediment-dissolved partitioning coefficients (logK(oc)(obs)) varied between 4.92 and 8.59 l/kg-oc; while in the bottom sediment-dissolved interface, logK(oc)(obs) values ranged from 5.48 to 8.48 l/kg-oc. Observed logK(oc)values varied within a factor of 0.64-1.26 from equilibrium logK(oc) values, suggesting fluxes of PCDD/PCDFs across the interfaces. It was found that in the HSC, on average, the tendency of a compound to move from the particulate phase to the dissolved phase decreases with increasing K(ow).     

超声波／零价铁降解水中双酚A

研究了超声波／零价铁（US／Fe^0）工艺对水中双酚A（BPA）的降解效果及影响因素。结果表明,US／Fe^0工艺可以有效降解水中的BPA,具有协同作用,且降解过程符合一级动力学规律;Fe^0具有促进和抑制的双重作用;超声功率越大,越有利于BPA的降解;初始浓度较低时,BPA的降解效果较好;弱酸性条件有利于BPA的降解;加入一定量的自由基捕获剂（正丁醇）可以抑制BPA的降解;联合作用2h后,TOC的去除率较低,说明其矿化程度不完全。     

Effects of bacterial counts and temperature on the biodegradation of bisphenol A in river water

Total 15 surface river waters were collected from thirteen different rivers to investigate a relationship of bacterial counts and temperature to the degradation of bisphenol A (BPA). Autoclaved and non-autoclaved river water samples were spiked with 0.2 mg/l BPA. The spiked samples were placed at temperatures of 4, 20, and 30 degrees C and analyzed by high performance liquid chromatography. BPA was degraded at all temperatures in the non-autoclaved samples. However, BPA in the autoclaved samples was not changed at all temperatures for 20 d. These results show that the primary factor of BPA degradation in river water is bacteria. Moreover, three groups [group A (> 10000 CFU/ml), group B (2000-10000 CFU/ml), and group C (< 2000 CFU/ml)], were made on the basis of bacterial counts of the samples. Half-lives for BPA degradation in groups A, B, and C were 2, 3, and 6 d at 30 degrees C and were 4, 5, and 7 d at 20 degrees C, respectively. But at 4 degrees C, the loss of BPA was about 40%, 20%, and 10% in groups A, B, and C for 20 d, respectively. Bacterial counts exerted an influence on BPA degradation in river water with temperature. Our results also show that BPA-degrading bacteria are widely distributed in river waters.