Effect of copper(II) on biodegradation of benzo[a]pyrene by Stenotrophomonas maltophilia

Benzo[a]pyrene (BaP) biodegradation by Stenotrophomonas maltophilia was studied under the influence of co-existed Cu(II) ions. About 45% degradation was achieved within 3 d when dealing with 1 mg L^?1 BaP under initial natural pH at 30 °C; degradation reached 48% in 2 d at 35 °C. Efficacy of BaP biodegradation reached the highest point at pH 4. In the presence of 10 mg L^?1 Cu(II) ions, the BaP removal ratio was 45% on 7th day, and maintained stable from 7 to 14 d at 30 °C under natural pH. The favorable temperature and pH for BaP removal was 25 °C and 6.0 respectively, when Cu(II) ions coexisted in the solutions. Experiments on cometabolism indicated that S. maltophilia performed best when sucrose was used as an additional carbon source. GC–MS analysis revealed that the five rings of BaP opened, producing compounds with one or two rings which were more bioavailable.     

Effect of natural compounds on reducing formaldehyde emission from plywood

The effects of natural compounds on reducing formaldehyde emission from plywood were investigated. Urea, catechin and vanillin were examined as the natural formaldehyde reducers. The microemission cell, with an internal volume of 35 ml, the maximum exposed test surface area of 177 cm² and an air purge flow rate of 50 ml min⁻¹, was used to measure specific emission rate (SER). In the case of no reducer treatment, formaldehyde emission from plywood was fast and SERs were 4.4 mg m⁻² h⁻¹ at 30 °C and 15 mg m⁻² h⁻¹ at 60 °C. When this plywood was treated with the natural compounds, the SERs of formaldehyde were decreased at all temperatures. In the case of urea treatment, the SERs of formaldehyde decreased to 0.30 mg m⁻² h⁻¹ at 30 °C and 0.65 mg m⁻² h⁻¹ at 60 °C. When the urea treatment was applied to the inside of kitchen cabinet (made from plywood; 270 cm wide, 60 cm deep, 250 cm high), the concentration of formaldehyde was reduced substantially from 1600 to 130 μg m⁻³. The reducing effect of formaldehyde continued during the observation period (6 months), with a mean concentration of 100 μg m⁻³. Reducers in the plywood would react with released formaldehyde. Application of natural compounds such as urea, catechin and vanillin could provide a simple and effective approach for suppressing formaldehyde emission from plywood.     

Organic matter in the bulk precipitations in Zagreb and Šibenik,Croatia

Dissolved organic carbon (DOC), surface active substances (SAS) and copper complexing capacity (CuCC) were studied in bulk precipitations collected periodically from 2003 to 2007 in the continental city of Croatia (Zagreb: n = 27) and in the city at the Adriatic coast (?ibenik: n = 38). DOC concentrations (Zagreb: 0.67–4.03 mgC/L with average concentration of 1.93 ± 0.76 mgC/L; ?ibenik: 0.44–4.13 mgC/L with average concentration of 1.83 ± 0.83 mgC/L) are similar to those measured in other samples of continental rainwater in the northern hemisphere. The concentrations of SAS in samples from Zagreb ranged from 0.055 to 0.45 eq. Triton-X-100 mg/L with average concentration of (0.14 ± 0.06) eq. Triton-X-100 mg/L. SAS fractions were of a similar range in ?ibenik (0.02–0.60 eq. Triton-X-100 mg/L) with an average concentration of 0.11 ± 0.06 eq. Triton-X-100 mg/L. However, the lowest values of SAS (between 0.02 and 0.04 eq. Triton-X-100 mg/L) were observed only in ?ibenik (27%). We have estimated that the higher pH values were responsible for lower surface activity of organic matter in bulk samples from ?ibenik. DOC may form complexes that control the transport and solubility of heavy metals in natural water. CuCC measured in ?ibenik in the range 0.066–1.4 μM Cu²⁺ was in general higher, compared to the one in Zagreb (0.010–0.586 μM Cu²⁺) which is the result of biogenically driven organic contribution to the precipitation, especially in the warmer period of the year.     

Henry's Law coefficients of chloropicrin and methyl isothiocyanate

Henry's Law coefficients were measured for the first time for chloropicrin and methyl isothiocyanate (MITC) at 25 °C in deionized water, in 0.10 M NaCl, in 0.20 M NaCl, and in pH 4.0 and 8.0 buffered solutions. For chloropicrin, the Henry's Law coefficient was 2.1±0.3 atm M⁻¹, and did not show significant pH dependence or dependence on ionic strength. For MITC, the coefficient was much smaller, 0.06±0.05 atm M⁻¹. The Henry's Law coefficient for MITC did show dependence on ionic strength, increasing to 0.14±0.05 atm M⁻¹ at 0.20 M, but did not appear to depend on pH. MITC has a much stronger tendency to remain in solution than chloropicrin. The transport of chloropicrin from solution to the atmosphere is likely to be significant environmentally, while MITC shows a much lower rate of volatilization. When transferred to the atmosphere, oxidation and photochemical reactions are likely to dominate the transformation of both chloropicrin and MITC, rather than heterogenous reactions.     

Size distribution of metals in urban aerosols in Seville (Spain)

The size distribution of metals in aerosols has been studied in 12 areas of the city of Seville. Urban particles were collected with a high-volume sampling system equipped with a cascade impactor, which effectively separates the particulate matter into six-size ranges. Forty-one samples were collected in spring 1996. Each filter was extracted with a mixture of nitric and percloric acids. The acid solutions of the samples were analysed in six-particle fractions by inductively coupled plasma atomic emission spectrometry (ICP-AES). The impactor stage fractionation of particles shows a typical bimodal distributions, one corresponding to the fine mode below 1 μm (55%), and the other to the coarse mode around 10 μm (32%). With regard to the size distribution of metals, we concluded that potentially toxic metals, such as nickel, lead and cadmium are mainly accumulated in the smaller particles, with percentages of 72.6, 69.4 and 63.8%, respectively. Lead have a concentration of 63.7 ng m⁻³, more than copper and manganese (26.7 and 16.5 ng m⁻³) and above all more than nickel, cobalt and cadmium (1.97, 0.54 and 0.32 ng m⁻³).     

Mobile sources of atmospheric polycyclic aromatic hydrocarbons in a roadway tunnel

Amounts of polycyclic aromatic hydrocarbons (PAHs) and oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) in samples collected from the air, from the dust on a guardrail, and from the soils on a tunnel roadway at five sampling sites in a regular roadway tunnel were chemically analyzed in order to determine their sources. Among the 23 PAHs found in the air samples, pyrene was found in the highest concentration (43±7.2 ng/m³), followed by fluoranthene (26±4.3 ng/m³). Among 20 oxy-PAHs found in the air samples, anthraquinone was found in the greatest amount (56±3.9 ng/m³). The average concentration of the major PAHs found in the guardrail dust samples were 6.9±0.77 μg/g for pyrene, 5.5±0.76 μg/g for fluoranthene, and 2.6±0.30 μg/g for phenanthrene. The average concentration of the major oxy-PAHs found in the guardrail dust samples were 9.2±3.5 μg/g for anthraquinone and 1.4±0.50 μg/g for 2-methylanthraquinone. The average concentration of the major PAHs found in the soil samples were 1.1±0.31 μg/g for fluoranthene, 0.92±0.21 μg/g for pyrene, and 0.72±0.16 μg/g for phenanthrene. The average concentration of the major oxy-PAHs found in the soil samples were 1.2±0.88 μg/g for anthraquinone, 0.18±0.04 μg/g for 4-biphenylcarboxaldehyde, and 0.13±0.08 μg/g for 2-methylanthraquinone. The BeP ratios calculated from the results suggest that most PAHs found in the samples collected from the roadway tunnel were from automobile exhaust gases.     

Transformation of diesel engine exhaust in an environmental chamber

Overnight aging experiments with diesel engine exhaust from a diesel power aggregate, with no or 9 kW load, and from a diesel-fueled vehicle were conducted in an environmental chamber. During a 24 h aging period the volatilities of monodisperse particles at 140, 250 and 360 °C heater temperatures were analyzed with volatility tandem differential mobility analysis (VTDMA). The particulate organic to total carbon ratio and organic carbon subfractions at 120, 250, 450 and 550 °C were analyzed with thermal-optical carbon analysis for samples from fresh, 8 or 18 h aged and 24 h aged aerosol. During the experiment also the particle size distribution, ozone and nitrogen oxide concentration, and temperature, relative humidity and total solar and total ultraviolet radiation in the chamber were monitored.After injection, the geometric mean diameter and number concentration of the particles in the chamber were 66–85 nm and 0.9–4.6×10⁵ cm⁻³, respectively. The particles were seen to grow fast, at a growth rate of 18–47 nm h⁻¹ during the first hour. The fresh particles from the diesel power aggregate contained 37–45% of apparent volume semi-volatile compounds with no load and 10–24% with 9 kW load. The semi-volatile apparent volume fraction at 360 °C for 50 nm particles produced by the diesel power aggregate was 57%. After 24 h of aging, the semi-volatile apparent volume fraction at 360 °C for 100 nm particles was 99%. This suggests that the particles in the 24 h aged aerosol at this size class are no more primary particles but particles that are formed in the chamber through nucleation and subsequent growth.     

Measurements of atmospheric nitrous acid and nitric acid

A highly sensitive technique for the measurement of atmospheric HONO and HNO₃ is reported. The technique is based on aqueous scrubbing using two coil samplers, followed by conversion of HNO₃ to nitrite, derivatization of nitrite to a highly light-absorbing azo dye with sulfanilamide (SA) and N-(1-naphthyl) ethylenediamine (NED), and high performance liquid chromatography (HPLC) analysis. HNO₃ concentration was obtained by the difference of the two channels. Two scrubbing solutions were used for sampling the two species: a 1-mM phosphate buffer solution (pH 7) for the measurement of HONO and a 180 mM NH₄Cl/NH₃ buffer solution (pH 8.5) for the measurement of HONO+HNO₃. The scrubbing solution flow rate was 0.24 ml min⁻¹ and the gas sampling flow rate was 2 l min⁻¹. HNO₃ in the NH₄Cl/NH₃ buffer solution was quantitatively reduced to nitrite along an on-line 0.8-cm Cd reductor column. Nitrite in both channels was derivatized with 2 mM SA and 0.2 mM NED in 25 mM HCl. Quantitative derivatization was achieved within 5 min at 55°C. The azo dye derivative was then separated from the SA/NED reagent by reversed-phase HPLC and detected with a UV-vis detector at 540 nm. With an on-line SEP-PAK C-18 cartridge for the reagent purification, the method detection limit is estimated to be better than 1 pptv for HONO and about 20 pptv for HNO₃. The sample integration time was about 2 min and the sampling frequency is every 10 min. Data collected in downtown Albany and Whiteface Mountain, NY, are shown as examples of applications of this technique in both urban and remote clean environments.     

Chemical composition of fresh snowfalls at Palmer Station,Antarctica

A first time investigation was performed to establish a chemical baseline for snowfall at Palmer Station Antarctica (64°46′S, 64°05′W) since there was no such record. A chemical baseline for snow could be use to validate climate change studies based on ice core analyses. The snow samples contained (from high to low mass concentration) total organic carbon, chloride, inorganic carbon, sodium, sulfate, magnesium, calcium, potassium, fluoride, ammonium, and nitrate, excluding hydrogen and hydroxide. The pH of these samples ranged between 4.0–6.2. The relatively low nitrate and relatively high sulfate concentrations found in our samples are consistent with the results of other studies for this region of Antarctica. The ions and pH do not appear to favor a particular wind direction during this period. The total deposition of sulfate and flouride via snowfall between 10 January and 10 February is conservatively estimated to be 4.78 and 1.3 kg km^-2, respectively.     

Analysis of particulate polycyclic aromatic hydrocarbons by on-line coupled supercritical fluid extraction–liquid chromatography–gas chromatography–mass spectrometry

An on-line supercritical fluid extraction–liquid chromatography–gas chromatography–mass spectrometry (SFE–LC–GC–MS) method was developed for the analysis of the particulate polycyclic aromatic hydrocarbons (PAHs). The limits of detection of the system for the quantification standards were in the range of 0.25–0.57 ng, while the limits of determinations for filter samples varied from 0.02 to 0.04 ng m⁻³ (24 h sampling). The linearity was excellent from 5 to 300 ng (R²>0.967). The analysis could be carried out in a closed system without tedious manual sample pretreatment and with no risk of errors by contamination or loss of the analytes. The results of the SFE–LC–GC–MS method were comparable with those for Soxhlet and shake-flask extractions with GC–MS. The new method was applied to the analysis of PAHs collected by high-volume filter in the Helsinki area to study the seasonal trend of the concentrations. The individual PAH concentrations varied from 0.015 to more than 1 ng m⁻³, while total PAH concentrations varied from 0.81 to 5.68 ng m⁻³. The concentrations were generally higher in winter than in summer. The mass percentage of the total PAHs in total suspended particulates ranged from 2.85×10⁻³% in July to 15.0×10⁻³% in December. Increased emissions in winter, meteorological conditions, and more serious artefacts during the sampling in summer season may explain the concentration profiles.     

Waste recombinant DNA: Effectiveness of thermo-treatment to manage potential gene pollution

Heating at 100 °C for 5–10 min is a common method for treating wastewater containing recombinant DNA in many bio-laboratories in China. In this experiment, plasmid pET-28b was used to investigate decay efficiency of waste recombinant DNA during thermo-treatment. The results showed that the decay half-life of the plasmid was 2.7–4.0 min during the thermo-treatment, and even heating for 30 min the plasmids still retained some transforming activity. Low pH promoted the decay of recombinant DNA, but NaCl, bovine serum albumin and EDTA, which existed in the most wastewater from bio-laboratories, protected DNA from degradation. Thus, the decay half-life of plasmid DNA may be longer than 2.7–4.0 min practically. These results suggest that the effectiveness of heating at 100 °C for treating waste recombinant DNA is low and a gene pollution risk remains when those thermo-treated recombinant DNAs are discharged into the environment. Therefore other simple and effective methods should be developed.     

Influence of a large steel complex on the spatial distribution of volatile polycyclic aromatic hydrocarbons (PAHs) determined by passive air sampling using membrane-enclosed copolymer (MECOP)

Membrane-enclosed copolymer (MECOPs) samplers containing crystalline copolymers of ethylvinylbenzene-divinylbenzene in polyethylene membranes were used to assess the influence of a steel complex on the level and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in ambient air. MECOPs were deployed at six sites in Pohang, Korea for 37 days (August 9, 2005–September 14, 2005). Fluorene, phenanthrene, anthracene, and fluoranthene were dominant PAHs with the highest contribution of phenanthrene (59%) to the total amount of vapor-phase PAHs. The spatial distribution of total PAHs in the vapor phase ranging from 76 to 1077 ng MECOP⁻¹ and air dispersion modeling suggested that the steel complex was the major PAH source in Pohang. It was revealed that the major wind directions rather than the distance from the steel complex were a significant factor affecting the levels of PAHs at the sampling sites. Finally, we tried to convert MECOP concentrations (ng MECOP⁻¹) to air concentrations (ng m⁻³) with the modified sampling rates (m³ day⁻¹). This study demonstrates again that passive air samplers are useful tools for spatially resolved and time-integrated monitoring of semivolatile organic compounds (SOCs) in ambient air.     

Photooxidation of methylhydroperoxide and ethylhydroperoxide in the aqueous phase under simulated cloud droplet conditions

The photooxidation of methylhydroperoxide (MHP) and ethylhydroperoxide (EHP) was studied in the aqueous phase under simulated cloud droplet conditions. The kinetics and the reaction products of direct photolysis and OH-oxidation were studied for both compounds. The photolysis frequencies obtained were J_MHP=4.5 (±1.0)×10⁻⁵ s⁻¹ and J_EHP=3.8 (±1.0)×10⁻⁵ s⁻¹ for MHP and EHP respectively at 6 °C. The rate constants of OH-oxidation of MHP at 6 °C were 6.3 (±2.6)×10⁸ M⁻¹ s⁻¹ and 5.8 (±1.9)×10⁸ M⁻¹ s⁻¹ relative to ethanol and 2-propanol respectively, and the rate constant of OH-oxidation of EHP was 2.1 (±0.6)×10⁹ M⁻¹ s⁻¹ relative to 2-propanol at 6 °C. The reaction products obtained were not only the corresponding aldehydes, but also the corresponding acids, and hydroxyhydroperoxides as primary reaction products. The yields for these products were sensitive to the pH value. The carbon balance was higher than 85% for all experiments, showing that most reaction products were detected. A chemical mechanism was proposed for each reaction, and the atmospheric implications were discussed.     

Monitoring personal,indoor, and outdoor exposures to metals in airborne particulate matter: Risk of contamination during sampling,handling and analysis

Rigorous sampling and quality assurance protocols are required for the reliable measurement of personal, indoor and outdoor exposures to metals in fine particulate matter (PM_2.5). Testing of five co-located replicate air samplers assisted in identifying and quantifying sources of contamination of filters in the laboratory and in the field. A field pilot study was conducted in Windsor, Ont., Canada to ascertain the actual range of metal content that may be obtained on filter samples using low-flow (4 L min⁻¹) 24-h monitoring of personal, indoor and outdoor air. Laboratory filter blanks and NIST certified reference materials were used to assess contamination, instrument performance, accuracy and precision of the metals determination. The results show that there is a high risk of introducing metal contamination during all stages of sampling, handling and analysis, and that sources and magnitude of contamination vary widely from element to element. Due to the very small particle masses collected on low-flow 24-h filter samples (median 0.107 mg for a sample volume of approximately 6 m³) the contribution of metals from contamination commonly exceeds the content of the airborne particles being sampled. Thus, the use of field blanks to ascertain the magnitude and variability of contamination is critical to determine whether or not a given element should be reported. The results of this study were incorporated into standard operating procedures for a large multiyear personal, indoor and outdoor air monitoring campaign in Windsor.     

Organic trace gas composition of the marine boundary layer over the northwest Indian Ocean in April 2000

In April 2000 atmospheric trace gas measurements were performed on the western Indian Ocean on a cruise of the Dutch research vessel Pelagia from the Seychelles (5°S, 55°E) to Djibouti (12°N, 43°E). The measurements included analysis of dimethyl sulfide (DMS), acetone and acetonitrile every 40 s using PTR-MS (proton-transfer-reaction mass spectrometry) and gas chromatographic analyses of C₂–C₇ hydrocarbons in air samples taken during the cruise. The measurements took place at the end of the winter monsoon season and the sampled air masses came predominantly from the Southern Hemisphere, resulting in low concentrations of some long-lived hydrocarbons, halocarbons, acetone (350 pptv) and acetonitrile (120 pptv). On three consecutive days a diurnal cycle in DMS concentration was observed, which was used to estimate the emission of DMS (1.5±0.7×10¹³ molecules m⁻² s⁻¹) and the 24 h averaged concentration of hydroxyl (OH) radicals (1.4±0.7×10⁶ molecules cm⁻³). A strongly increased DMS concentration was found at a location where upwelling of deeper ocean waters took place, coinciding with a marked decrease in acetone and acetonitrile. In the northwestern Indian Ocean a slight increase of some trace gases was noticed showing a small influence of pollution from Asia and from northeast Africa as indicated with back trajectory calculations. The air masses from Asia had elevated acetonitrile concentrations showing some influence of biomass burning as was also found during the 1999 Indian Ocean Experiment, whereas the air masses from northeast Africa seemed to have other sources of pollution.     

Inventory of aerosol and sulphur dioxide emissions from India: I—Fossil fuel combustion

A comprehensive, spatially resolved (0.25°×0.25°) fossil fuel consumption database and emissions inventory was constructed, for India, for the first time. Emissions of sulphur dioxide and aerosol chemical constituents were estimated for 1996–1997 and extrapolated to the Indian Ocean Experiment (INDOEX) study period (1998–1999). District level consumption of coal/lignite, petroleum and natural gas in power plants, industrial, transportation and domestic sectors was 9411 PJ, with major contributions from coal (54%) followed by diesel (18%). Emission factors for various pollutants were derived using India specific fuel characteristics and information on combustion/air pollution control technologies for the power and industrial sectors. Domestic and transportation emission factors, appropriate for Indian source characteristics, were compiled from literature. SO₂ emissions from fossil fuel combustion for 1996–1997 were 4.0 Tg SO₂ yr⁻¹, with 756 large point sources (e.g. utilities, iron and steel, fertilisers, cement, refineries and petrochemicals and non-ferrous metals), accounting for 62%. PM_2.5 emitted was 0.5 and 2.0 Tg yr⁻¹ for the 100% and the 50% control scenario, respectively, applied to coal burning in the power and industrial sectors. Coal combustion was the major source of PM_2.5 (92%) primarily consisting of fly ash, accounting for 98% of the “inorganic fraction” emissions (difference between PM_2.5 and black carbon+organic matter) of 1.6 Tg yr⁻¹. Black carbon emissions were estimated at 0.1 Tg yr⁻¹, with 58% from diesel transport, and organic matter emissions at 0.3 Tg yr⁻¹, with 48% from brick-kilns. Fossil fuel consumption and emissions peaked at the large point industrial sources and 22 cities, with elevated area fluxes in northern and western India. The spatial resolution of this inventory makes it suitable for regional-scale aerosol-climate studies. These results are compared to previous studies and differences discussed. Measurements of emission factors for Indian sources are needed to further refine these estimates.     

Seasonal patterns of heavy metal deposition to the snow on Lambert Glacier basin,East Antarctica

Al, V, Mn, Fe, Cu, As, Cd, Ba, Pb, Bi and U were determined in a continuous series of 46 snow samples from a 2.3-m snow pit, covering the time period from austral spring 1998 to summer 2002, at a site on the east side of the Lambert Glacier basin in East Antarctica. Concentrations are very low for all metals and differ by orders of magnitude from one metal to another, with the mean concentrations ranging from 0.028 pg g⁻¹ for Bi to 165 pg g⁻¹ for Al. It is estimated that anthropogenic contributions are dominant for Cu, Pb and probably As, in the snow in our study area while the natural contributions from rock and soil dust, sea-salt spray and volcanic emissions account for most of the measured concentrations of the other metals. Our snow profiles show pronounced seasonal variations for Mn, As, Ba, Pb and Bi throughout the year, but a very different situation is observed between different metals. These observations suggest that heavy metals determined in our samples are controlled by different transport and deposition mechanisms related to physical and chemical alterations in the properties and sources of aerosol.     

Heavy metal distribution in dust from elementary schools in Hermosillo,Sonora, México

The city of Hermosillo, Sonora in northern Mexico was investigated for its heavy metals content. Samples of sedimented dust in roofs from 25 elementary schools were analyzed for their contents of Ni, Cr, Zn, Cd, Co, Ba, V, Pb, Fe and Cu after digestion with nitric acid. The results of the analysis were used to determine spatial distribution and magnitude of heavy metals pollution. The results of this study reveal that heavy metals distribution is different in two areas of the city. The southern area contains higher concentrations of heavy metals than the northcentral area. The mean level of Cd in exterior dust is 5.65 mg kg⁻¹ in the southern area whereas the mean level of Cd is 2.83 mg kg⁻¹ in the northcentral area. Elevated concentrations of Zn (2012 mg kg⁻¹), Pb (101.88 mg kg⁻¹), Cr (38.13 mg kg⁻¹) and Cd (28.38 mg kg⁻¹) in roof dust were found in samples located near industrial areas. Principal component analysis (PCA) was applied to the data matrix to evaluate the analytical results and to identify the possible pollution sources of metals. PCA shows two main sources: (1) Pb, Cd, Cr and Zn are mainly derived from industrial sources, combined with traffic sources; (2) Fe, Co and Ba are mainly derived from natural sources. V and Ni are highly correlated and possibly related to fuel combustion processes. Enrichment factors were calculated, which in turn further confirms the source identification. Ba and Co are dominantly crustal. Anthropogenically added Cd, Pb, Zn and Cr show maximum enrichment relative to the upper continental crustal component. The distribution of the heavy metals in dust does not seem to be controlled only by the topography of the city, but also by the location of the emission sources.     

Optical and microphysical properties of severe haze and smoke aerosol measured by integrated remote sensing techniques in Gwangju,Korea

Aerosol optical and microphysical parameters from severe haze events observed in October 2005 at Gwangju, Korea (35.10°N, 126.53°E) were determined from the ground using a multi-wavelength Raman lidar, a sunphotometer, and a real-time carbon particle analyzer and from space using satellite retrievals. Two different aerosol types were identified based on the variability of optical characteristics for different air mass conditions. Retrievals of microphysical properties of the haze from the Raman lidar indicated distinct light-absorbing characteristics for different haze aerosols originating from eastern and northern China (haze) and eastern Siberia (forest-fire smoke). The haze transported from the west showed moderately higher absorbing characteristics (SSA = 0.90 ± 0.03, 532 nm) than from the northern direction (SSA = 0.96 ± 0.02). The organic/elemental carbon (OC/EC) ratio varied between 2.5 ± 0.4 and 4.1 ± 0.7.     

Dechlorination of hexachlorobenzene using lead–iron bimetallic particles

Synthesized lead–iron (Pb/Fe) bimetallic particles were applied to dechlorinate hexachlorobenzene (HCB) under various conditions (e.g. bimetal amount, initial pH value, reaction temperature, and reaction duration). The results showed that adding Pb onto Fe benefited the dechlorination of HCB and the bimetal with 1.4% Pb content performed best. The degradation rate decreased regularly as the initial pH value of the aqueous increased from 1.9 to 11.1 except for pH 7.0 where the fastest dechlorination rate emerged. The dechlorination could be enhanced by increasing the amount of Pb/Fe or the reaction temperature. The dechlorination ratio of HCB within 15 min increased from 24.3% to 81.3% when Pb/Fe amount increased from 0.1 g to 0.8 g. The dechlorination followed pseudo-first-order kinetics, and the dechlorination rate constants were 0.0027, 0.0064, 0.0157, and 0.0321 min^?1 at 25, 50, 70, and 85 °C, respectively, and the activation energy (E_a) of the dechlorination by Pb/Fe was 37.86 kJ mol^?1.