A study of bactericidal effect and optimization of pathogenic bacteria using TiO2 photocatalyst.

The photocatalytic degradation of Salmonella choleraesuis subsp. and Vibrio parahaemolyticus in water by TiO2 catalysts was investigated in a batch reactor. After 30 min of irradiation with UV light in the presence of 1 mg/ml of TiO2, death ratio of S. choleraesuis subsp. and V. parahaemolyticus was 60% and 83%, respectively. And complete killing of the cells was achieved after 3 h of illumination in the presence of TiO2. We established the response surface methodology to investigate the effect of principal parameters on the pathogenic bacteria sterilization such as TiO2 concentration, pH and temperature. By applying response surface analysis to the bactericidal effect of S. almonella choleraesuis subsp. and V. parahaemolyticus, we found that the cell death ratio was influenced significantly by the first order term of TiO2 concentration.

Photocatalytic degradation of 2,4-dinitrophenol using TiO2 in aqueous solution.

A new method was developed to synthesize uniform anatase TiO2 nanocrystals by the hydrolysis of titanium tetraisopropoxide in nitric acid-isopropyl alcohol aqueous solutions at 353 K. The samples were characterized by XRD, TEM, FE-SEM, and specific surface area determination. In this work, the photocatalytic degradation of 2,4-dinitrophenol in the presence of TiO2 using ultraviolet (UV) light source was investigated in a batch reactor. The effects of various factors, namely TiO2, pH, temperature and concentration, on the degradation performance of 2,4-DNP were studied. The photocatalytic degradation of 2,4-DNP follows the pseudo-first-order kinetics. In acidic or alkaline conditions, the photocatalytic degradation efficiency of 2,4-DNP was greater than that in neutral conditions. Thermodynamic studies have also been carried out and values of standard free energy (deltaG degrees), enthalpy (deltaH degrees) and entropy (deltaS degrees) were calculated.

Bactericidal effect of TiO2 on the selected Vibrio parahaemolyticus and optimization using response surface methodology.

In this work, the bactericidal effect of TiO2 on selected typical food pathogenic bacteria, Vibrio parahaemolyticus was studied. V parahaemolyticus is an important pathogen of humans and aqua-cultured animals. We established the response surface methodology (Box-Behnken Design) to investigate the effect of principal parameters on the cell sterilization such as TiO2 concentration, UV illumination time, temperature, and pH. The sterilization rate reached maximum value at the TiO2 concentration of 1.0 mg/ml. During irradiation under the time of 30 min with UV light with the 1g-TiO2/l, the sterilization rate was greater than 85%, and 99% or more cell lost their viability with 3 hours of irradiation. Sterilization rate of the cell increased with decrease in the pH and temperature.

Design of stormwater monitoring programs.

Stormwater runoff is now the leading source of water pollution in the United States, and stormwater monitoring programs have only recently been developed. This paper evaluates several stormwater monitoring programs to identify ways of increasing the likelihood of identification of high-risk dischargers and increasing data reliability for assisting in the development of total maximum daily loads. No relationship was found between various types of industrial activity or landuse and water quality data. Stormwater data collected with grab samples has much greater pollutant concentration variability than in potable water or wastewater monitoring programs. Industrial land use is an important source of metals. For grab samples, sampling time during the storm event will affect results. Data from California, which has distinct dry periods, showed a seasonal first flush, whereas data from areas with more uniform rainfall throughout the year did not show a seasonal first flush. Selecting a subset of sites from each monitored category using a flow-weighted composite sampler is an alternative strategy, and may result in lower overall cost with improved accuracy and variability in mass emissions, but may not be less successful in identifying high-risk dischargers.

Characterization of PM2.5 aerosols dominated by local pollution and Asian dust observed at an urban site in Korea during aerosol characterization experiments (ACE)--Asia Project.

Daily fine particulate matter (PM2.5) samples were collected at Gwangju, Korea, during the Aerosol Characterization Experiments (ACE)-Asia Project to determine the chemical properties of PM2.5 originating from local pollution and Asian dust (AD) storms. During the study period, two significant events occurred on April 10-13 and 24-25, 2001, and a minor event occurred on April 19, 2001. Based on air mass transport pathways identified by back-trajectory calculation, the PM2.5 dataset was classified into three types of aerosol populations: local pollution and two AD aerosol types. The two AD types were transported along different pathways. One originated from Gobi desert area in Mongolia, passing through Hunshandake desert in Northern Inner Mongolia, urban and polluted regions of China (AD1), and the other originated in sandy deserts located in the Northeast Inner Mongolia Plateau and then flowed southward through the Korean peninsula (AD2). During the AD2 event, a smoke plume that originated in North Korea was transported to our study site. Mass balance closures show that crustal materials were the most significant species during both AD events, contributing -48% to the PM2.5 mass; sulfate aerosols (19.1%) and organic matter (OM; 24.6%) were the second greatest contributors during the AD1 and AD2 periods, respectively, indicating that aerosol properties were dependent on the transport pathway. The sulfate concentration constituted only 6.4% (4.5 microg/m3) of the AD2 PM2.5 mass. OM was the major chemical species in the local pollution-dominated PM2.5 aerosols, accounting for 28.7% of the measured PM2.5 mass, followed by sulfate (21.4%), nitrate (15%), ammonium (12.8%), elemental carbon (8.9%), and crustal material (6.5%). Together with substantial enhancement of the crustal elements (Mg, Al, K, Ca, Sc, Ti, Mn, Fe, Sr, Zr, Ba, and Ce), higher concentrations of pollution elements (S, V, Ni, Zn, As, Cd, and Pb) were observed during AD1 and AD2 than during the local pollution period, indicating that, in addition to crustal material, the AD dust storms also had a significant influence on anthropogenic elements.