Effect of ambient-level gas-phase peroxides on foliar injury, growth, and net photosynthesis in Japanese radish (Raphanus sativus)

To investigate the effects of ambient-level gas-phase peroxides concurrent with O₃ on foliar injury, photosynthesis, and biomass in herbaceous plants, we exposed Japanese radish (Raphanus sativus) to clean air, 50 ppb O₃, 100 ppb O₃, and 2-3 ppb peroxides + 50 ppb O₃ in outdoor chambers. Compared with exposure to 100 ppb O₃, exposure to 2-3 ppb peroxides + 50 ppb O₃ induced greater damage in foliar injury, net photosynthetic rates and biomass; the pattern of foliar injury and the cause of net photosynthetic rate reduction also differed from those occurring with O₃ exposure alone. These results indicate for the first time that sub-ppb peroxides + 50 ppb O₃ can cause more severe damage to plants than 100 ppb O₃, and that not only O₃, but also peroxides, could be contributing to the herbaceous plant damage and forest decline observed in Japan's air-polluted urban and remote mountains areas.     

Determination of antibiotics in sewage from hospitals, nursery and slaughter house, wastewater treatment plant and source water in Chongqing region of Three Gorge Reservoir in China

Sewage samples from 4 hospitals, 1 nursery, 1 slaughter house, 1 wastewater treatment plant and 5 source water samples of Chongqing region of Three Gorge Reservoir were analyzed for macrolide, lincosamide, trimethoprim, fluorouinolone, sulfonamide and tetracycline antibiotics by online solid-phase extraction and liquid chromatography-tandem mass spectrometry. Results showed that the concentration of ofloxacin (OFX) in hospital was the highest among all water environments ranged from 1.660 μg/L to 4.240 μg/L and norfloxacin (NOR, 0.136-1.620 μg/L), ciproflaxacin (CIP, ranged from 0.011 μg/L to 0.136 μg/L), trimethoprim (TMP, 0.061-0.174 μg/L) were commonly detected. Removal range of antibiotics in the wastewater treatment plant was 18-100% and the removal ratio of tylosin, oxytetracycline and tetracycline were 100%. Relatively higher removal efficiencies were observed for tylosin (TYL), oxytetracycline (OXY) and tetracycline (TET)(100%), while lower removal efficiencies were observed for Trimethoprim (TMP, 1%), Epi-iso-chlorotetracycline (EICIC, 18%) and Erythromycin-H₂O (ERY-H₂O, 24%). Antibiotics were removed more efficiently in primary treatment compared with those in secondary treatment.     

Tracking nitrogen losses in a greenhouse crop rotation experiment in North China using the EU-Rotate_N simulation model

Vegetable production in China is associated with high inputs of nitrogen, posing a risk of losses to the environment. Organic matter mineralisation is a considerable source of nitrogen (N) which is hard to quantify. In a two-year greenhouse cucumber experiment with different N treatments in North China, non-observed pathways of the N cycle were estimated using the EU-Rotate_N simulation model. EU-Rotate_N was calibrated against crop dry matter and soil moisture data to predict crop N uptake, soil mineral N contents, N mineralisation and N loss. Crop N uptake (Modelling Efficiencies (ME) between 0.80 and 0.92) and soil mineral N contents in different soil layers (ME between 0.24 and 0.74) were satisfactorily simulated by the model for all N treatments except for the traditional N management. The model predicted high N mineralisation rates and N leaching losses, suggesting that previously published estimates of N leaching for these production systems strongly underestimated the mineralisation of N from organic matter.     

Simple model for estimating dry deposition velocity of ozone and its destruction in a polluted nocturnal boundary layer

Determining the destructions of both ozone and odd oxygen, O_x, in the nocturnal boundary layer (NBL) is important to evaluate the regional ozone budget and overnight ozone accumulation. This work develops a simple method to determine the dry deposition velocity of ozone and its destruction at a polluted nocturnal boundary layer. The destruction of O_x can also be determined simultaneously. The method is based on O₃ and NO₂ profiles and their surface measurements. Linkages between the dry deposition velocities of O₃ and NO₂ and between the dry deposition loss of O_x and its chemical loss are constructed and used. Field measurements are made at an agricultural site to demonstrate the application of the model. The model estimated nocturnal O₃ dry deposition velocities from 0.13 to 0.19 cm s^?1, very close to those previously obtained for similar land types. Additionally, dry deposition and chemical reactions account for 60 and 40% of the overall nocturnal ozone loss, respectively; ozone dry deposition accounts for 50% of the overall nocturnal loss of O_x, dry deposition of NO₂ accounts for another 20%, and chemical reactions account for the remaining 30%. The proposed method enables the use of measurements made in typical ozone field studies to evaluate various nocturnal destructions of O₃ and O_x in a polluted environment.     

Chemical mass balance source apportionment for combined PM2.5 measurements from U.S. non-urban and urban long-term networks

The Minnesota Particulate Matter 2.5 (PM_2.5) Source Apportionment Study was undertaken to explore the utility of PM_2.5 mass, element, ion, and carbon measurements from long-term speciation networks for pollution source attribution. Ambient monitoring data at eight sites across the state were retrieved from the archives of the Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Speciation Trends Network (STN; part of the Chemical Speciation Network [CSN]) and analyzed by an Effective Variance – Chemical Mass Balance (EV-CMB) receptor model with region-specific geological source profiles developed in this study. PM_2.5 was apportioned into contributions of fugitive soil dust, calcium-rich dust, taconite (low grade iron ore) dust, road salt, motor vehicle exhaust, biomass burning, coal-fired utility, and secondary aerosol. Secondary sulfate and nitrate contributed strongly (49–71% of PM_2.5) across all sites and was dominant (≥60%) at IMPROVE sites. Vehicle exhausts accounted for 20–70% of the primary PM_2.5 contribution, largely exceeding the proportion in the primary PM_2.5 emission inventory. The diesel exhaust contribution was separable from the gasoline engine exhaust contribution at the STN sites. Higher detection limits for several marker elements in the STN resulted in non-detectable coal-fired boiler contributions which were detected in the IMPROVE data. Despite the different measured variables, analytical methods, and detection limits, EV-CMB results from a nearby IMPROVE-STN non-urban/urban sites showed similar contributions from regional sources – including fugitive dust and secondary aerosol. Seasonal variations of source contributions were examined and extreme PM_2.5 episodes were explained by both local and regional pollution events.     

Emission factors and particulate matter size distribution of polycyclic aromatic hydrocarbons from residential coal combustions in rural Northern China

Coal consumption is one important contributor to energy production, and is regarded as one of the most important sources of air pollutants that have considerable impacts on human health and climate change. Emissions of polycyclic aromatic hydrocarbons (PAHs) from coal combustion were studied in a typical stove. Emission factors (EFs) of 16 EPA priority PAHs from tested coals ranged from 6.25 ± 1.16 mg kg^?1 (anthracite) to 253 ± 170 mg kg^?1 (bituminous), with NAP and PHE dominated in gaseous and particulate phases, respectively. Size distributions of particulate phase PAHs from tested coals showed that they were mostly associated with particulate matter (PM) with size either between 0.7 and 2.1 μm or less than 0.4 μm (PM_0.4). In the latter category, not only were more PAHs present in PM_0.4, but also contained higher fractions of high molecular weight PAHs. Generally, there were more than 89% of total particulate phase PAHs associated with PM_2.5. Gas-particle partitioning of freshly emitted PAHs from residential coal combustions were thought to be mainly controlled by absorption rather than adsorption, which is similar to those from other sources. Besides, the influence of fuel properties and combustion conditions was further investigated by using stepwise regression analysis, which indicated that almost 57 ± 10% of total variations in PAH EFs can be accounted for by moisture and volatile matter content of coal in residential combustion.     

超声吹脱去除氨氮的机理和动力学研究

采用超声吹脱技术对某印染厂印染废水中的氨氮进行了处理实验,探索了其反应机理并进行了动力学研究。研究表明,叔丁醇的存在没有降低废水中氨氮的去除率,证明.OH不是超声吹脱去除氨氮反应中的主导氧化物种。通过对反应产物的分析发现,超声吹脱去除氨氮的机理主要是氨氮以游离态的方式在空化效应下高温高压热解成氮气和氢气排出,同时氨气在空化效应产生的超临界状态下传质速度加快,在吹脱条件下更易于从废水中散失。动力学分析表明,印染废水中氨氮的超声去除反应属于一级反应,符合一级反应动力学。     

Theoretical versus observed gas-particle partitioning of carbonyl emissions from motor vehicles

A state-of-the-science thermodynamic model describing gas-particle absorption processes was used to predict the gas-particle partitioning of mixtures of approximately 60 carbonyl compounds emitted from low-emission gasoline-powered vehicles, three-way catalyst gasoline-powered vehicles, heavy-duty diesel vehicles under the idle-creep condition (HDDV idle), and heavy-duty diesel vehicles under the five-mode test (HDDV 5-mode). Exhaust was diluted by a factor of 120-580 with a residence time of approximately 43 sec. The predicted equilibrium absorption partitioning coefficients differed from the measured partitioning coefficients by several orders of magnitude. Time scales to reach equilibrium in the dilution sampling system were close to the actual residence time during the HDDV 5-mode test and much longer than the actual residence time during the other vehicle tests. It appears that insufficient residence time in the sampling system cannot uniformly explain the failure of the absorption mechanism to explain the measured partitioning. Other gas-particle partitioning mechanisms (e.g., heterogeneous reactions, capillary adsorption) beyond the simple absorption theory are needed to explain the discrepancy between calculated carbonyl partitioning coefficients and observed partitioning. Both of these alternative partitioning mechanisms imply great challenges for the measurement and modeling of semi-volatile primary organic aerosol (POA) species from motor vehicles. Furthermore, as emitted particle concentrations from newer vehicles approach atmospheric background levels, dilution sampling systems must fundamentally change their approach so that they use realistic particle concentrations in the dilution air to approximately represent real-world conditions. Samples collected with particle-free dilution air yielding total particulate matter concentrations below typical ambient concentrations will not provide a realistic picture of partitioning for semi-volatile compounds.     

Source apportionment of wintertime secondary organic aerosol during the California regional PM10/PM2.5 air quality study

The UCD/CIT air quality model with the Caltech Atmospheric Chemistry Mechanism (CACM) was used to predict source contributions to secondary organic aerosol (SOA) formation in the San Joaquin Valley (SJV) from December 15, 2000 to January 7, 2001. The predicted 24-day average SOA concentration had a maximum value of 4.26 μg m^?3 50 km southwest of Fresno. Predicted SOA concentrations at Fresno, Angiola, and Bakersfield were 2.46 μg m^?3, 1.68 μg m^?3, and 2.28 μg m^?3, respectively, accounting for 6%, 37%, and 4% of the total predicted organic aerosol. The average SOA concentration across the entire SJV was 1.35 μg m^?3, which accounts for approximately 20% of the total predicted organic aerosol. Averaged over the entire SJV, the major SOA sources were solvent use (28% of SOA), catalyst gasoline engines (25% of SOA), wood smoke (16% of SOA), non-catalyst gasoline engines (13% of SOA), and other anthropogenic sources (11% of SOA). Diesel engines were predicted to only account for approximately 2% of the total SOA formation in the SJV because they emit a small amount of volatile organic compounds relative to other sources. In terms of SOA precursors within the SJV, long-chain alkanes were predicted to be the largest SOA contributor, followed by aromatic compounds. The current study identifies the major known contributors to the SOA burden during a winter pollution episode in the SJV, with further enhancements possible as additional formation pathways are discovered.     

South Pole Antarctica observations and modeling results: New insights on HOx radical and sulfur chemistry

Measurements of OH, H₂SO₄, and MSA at South Pole (SP) Antarctica were recorded as a part of the 2003 Antarctic Chemistry Investigation (ANTCI 2003). The time period 22 November, 2003–2 January, 2004 provided a unique opportunity to observe atmospheric chemistry at SP under both natural conditions as well as those uniquely defined by a solar eclipse event. Results under natural solar conditions generally confirmed those reported previously in the year 2000. In both years the major chemical driver leading to large scale fluctuations in OH was shifts in the concentration levels of NO. Like in 2000, however, the 2003 observational data were systematically lower than model predictions. This can be interpreted as indicating that the model mechanism is still missing a significant HO_x sink reaction(s); or, alternatively, that the OH calibration source may have problems. Still a final possibility could involve the integrity of the OH sampling scheme which involved a fixed building site. As expected, during the peak in the solar eclipse both NO and OH showed large decreases in their respective concentrations. Interestingly, the observational OH profile could only be approximated by the model mechanism upon adding an additional HO_x radical source in the form of snow emissions of CH₂O and/or H₂O₂. This would lead one to think that either CH₂O and/or H₂O₂ snow emissions represent a significant HO_x radical source under summertime conditions at SP. Observations of H₂SO₄ and MSA revealed both species to be present at very low concentrations (e.g., 5 × 10⁵ and 1 × 10⁵ molec cm^?3, respectively), but similar to those reported in 2000. The first measurements of SO₂ at SP demonstrated a close coupling with the oxidation product H₂SO₄. The observed low concentrations of MSA appear to be counter to the most recent thinking by glacio-chemists who have suggested that the plateau's lower atmosphere should have elevated levels of MSA. We speculate here that the absence of MSA may reflect efficient atmospheric removal mechanisms for this species involving either dynamical and/or chemical processes.