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Wang W.,Fudan University | Wang S.,University of Shanghai for Science and Technology | Xu J.,Nanjing Environmental Monitoring Center | Zhou R.,Fudan University | And 3 more authors.
Environmental Science and Pollution Research | Year: 2015

The gas-phase ammonia (NH3) and fine particle PM2.5 ammonium (pNH4+) (collectively, NHx) were monitored between July 2013 and August 2014 in a busy traffic area of Nanjing, China. Results showed that PM2.5 concentration was 66.7 μg m−3, and NH3 concentration was 6.66 μg m−3. In the PM2.5, the concentration of pNH4+ was 3.04 μg m−3, SO42− (pSO42−) was 10.16 μg m−3, and NO3− (pNO3−) was 1.60 μg m−3. The significant correlation curves from the tests of PM2.5 revealed that molar ratio of pNH4+ and pSO42− was approximately 2, which could be (NH4)2SO4. Particulate NH4+ primarily associated with pSO42−, which accounted for 4.54 % of total PM2.5 mass. The PM2.5 observed acidic and the NH3 in the atmosphere neutralized acidic species, mainly in a sulfate form. The traffic intensity in the region was partially related to the formation of PM2.5 and NH3, suggesting that traffic pollution may be an important source of PM2.5. The reaction between NHx and acidic species was assumed to the secondary PM2.5. The neutralization and photochemical property of NHx were discussed. © 2015 Springer-Verlag Berlin Heidelberg Source

Zhang J.,Nanjing Southeast University | Zhang J.,Jiangnan University | Fu D.,Nanjing Southeast University | Yang L.,Nanjing Environmental Monitoring Center | And 2 more authors.
Journal of Southeast University (English Edition) | Year: 2011

In order to explore the reaction mechanism of Fe3+ and the mineralization effect of the micropollutant, Fe3+-assisted photocatalytic oxidation of sulfadiazine (SD) in the TiO2 suspended solution is investigated. The effect of Fe3+participation, the degradation kinetics of SD, the effect of SD mineralization and the possible mechanism of Fe3+ participation in TiO2 suspension are analyzed by adding FeCl3, taking samples at a given time and determining the SD concentration. Results indicate that the degradation of SD catalyzed by TiO2/Fe3+ is faster than that catalyzed by TiO2 or Fe3+separately. The photocatalytic degradation of SD follows the pseudo-first-order kinetics model in a range of 20 to 80 mg/L of initial concentration. The mineralization rate of SD can be enhanced by the addition of Fe3+ in the TiO2 suspended solution. The mechanism of the rapid degradation of SD is proposed, which indicates that Fe3+ adsorbed on the surface of TiO2 particles acts as an electron acceptor. The amount of recombining electron-hole pairs decreases, and the amount of hydroxyl radicals increases. The increased hydroxyl radical strengthens the degradation of SD in the TiO2/Fe3+ suspended solution. Copyright. Source

Dou Y.,Nanjing University | Dou Y.,Nanjing Environmental Monitoring Center | Wang B.,Nanjing University | Chen L.,Nanjing University | Yin D.,Tongji University
Environmental Science and Pollution Research | Year: 2013

Bicarbonate plays a crucial role in limiting the growth of submersed aquatic macrophytes in eutrophic lakes, and high ammonia is often toxic to macrophytes. In order to evaluate the combined effect of HCO3 - and total ammonia (i.e., the total of NH3 and NH4 +) on submersed macrophytes Vallisneria natans, the growth and physiological response of V. natans in the presence of HCO3 - and ammonia were studied. The results showed that with the increase of ammonia, morphological parameters of V. natans declined. In contrast, increased HCO3 - concentration stimulated the growth of V. natans, especially when the NH4 +-N/NO3 --N ratio was 1:7. High ammonia concentration induced excess free amino acids (FAA) accumulation and soluble carbohydrates (SC) depletion in plant tissues. However, the elevated HCO3 - promoted the synthesis of SC and rendered the decrease of FAA/SC ratio. The results also suggested that HCO3 - could partially alleviate the stress of ammonia, as evidenced by the decrease of FAA/SC ratio and the growth enhancement of V. natans when the ammonia concentration was 0.58 mg L-1. Given the fact that HCO3 - is probably the dominant available carbon source in most eutrophic lakes, the ability of V. natans to use HCO3 - for SC synthesis may explain the alleviating effect of HCO3 - on V. natans under ammonia stress. © 2013 Springer-Verlag Berlin Heidelberg. Source

Chen K.,Nanjing University of Information Science and Technology | Yin Y.,Nanjing University of Information Science and Technology | Wei Y.-X.,Nanjing Environmental Monitoring Center | Yang W.-F.,Nanjing University of Information Science and Technology
Zhongguo Huanjing Kexue/China Environmental Science | Year: 2010

Chemical characteristics and possible sources of fine particular matter (PM2.5) was investigated for 1 year in Nanjing. PM2.5 was collected from June 2007 to May 2008, which carbonaceous species, organic carbon (OC) and elemental carbon (EC), in the samples were analyzed. Seasonal variations of OC and EC concentrations were investigated; the pollution degree and characteristics of carbonaceous aerosols during haze and no haze period were analyzed and compared. Results showed that yearly PM2.5 and carbonaceous concentrations varied in wide ranges with 12.1~287.1 μg/m3 for PM2.5, 2.6~47.0 μg/m3 for OC and 1.0~33.6 μg/m3 for EC. On seasonal average, the highest PM2.5 (109.6 μg/m3) and OC (20.8 μg/m3) levels occurred during summer. The seasonal average concentrations of PM2.5 and organic carbon levels ranked by the order of summer > autumn > winter > spring, while the seasonal average concentrations of EC were in the order of autumn, spring, winter and summer. The OC/EC ratio and concentrations of carbonaceous species such as, OC, EC and total carbon (TC) in haze days were 1.7 2.0, 1.8, and 1.9 times higher than those in non-haze days. Backward air trajectories indicated that haze formation in Nanjing was attributable to air masses with abundant water vapors and pollutants. Source

Han S.-Y.,Nanjing University | Qiao J.-Q.,Nanjing University | Zhang Y.-Y.,Nanjing University | Yang L.-L.,Nanjing Environmental Monitoring Center | And 3 more authors.
Chemosphere | Year: 2011

n-Octanol/water partition coefficients (P) for DDTs and dicofol were determined by reversed-phase high performance liquid chromatography (RP-HPLC) on a C18 column using methanol-water mixture as mobile phase. A dual-point retention time correction (DP-RTC) was proposed to rectify chromatographic retention time (tR) shift resulted from stationary phase aging. Based on this correction, the relationship between logP and logkw, the logarithm of the retention factor extrapolated to pure water, was investigated for a set of 12 benzene homologues and DDT-related compounds with reliable experimental P as model compounds. A linear regression logP=(1.10±0.04) logkw - (0.60±0.17) was established with correlation coefficient R2 of 0.988, cross-validated correlation coefficient Rcv2 of 0.983 and standard deviation (SD) of 0.156. This model was further validated using four verification compounds, naphthalene, biphenyl, 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (p,p'-DDD) and 2,2-bis(4-chlorophenyl)-1,1-dichloroethene (p,p'-DDE) with similar structure to DDT. The RP-HPLC-determined P values showed good consistency with shake-flask (SFM) or slow-stirring (SSM) results, especially for highly hydrophobic compounds with logP in the range of 4-7. Then, the P values for five DDT-related compounds, 2-(2-chlorophenyl)-2-(4-chlorophenyl)-1,1,1-trichloroethane (o,p'-DDT), 2-(2-chlorophenyl)-2-(4-chlorophenyl)-1,1-dichloroethane (o,p'-DDD), 2-(2-chlorophenyl)-2-(4-chlorophenyl)-1,1-dichloroethene (o,p'-DDE), and 2,2,2-trichloro-1,1-bis(4-chlorophenyl)ethanol (dicofol) and its main degradation product 4,4'-dichlorobenzophenone (p,p'-DBP) were evaluated by the improved RP-HPLC method for the first time. The excellent precision with SD less than 0.03 proved that the novel DP-RTC protocol can significantly increases the determination accuracy and reliability of P by RP-HPLC. © 2011 Elsevier Ltd. Source

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