Isolation of Salmonella typhimurium Tn5 mutants defective for survival on egg shell surface using transposon footprinting

The objective of this study was to screen the genome of Salmonella typhimurium for genes potentially required for survival on egg shell surfaces using a novel transposon footprinting method based on a previously developed Tn5 mutagenesis technique. Since the amplified DNA fragment length should usually be unique for each mutant, the polymerase chain reaction products separated on an agarose gel generate a transposon footprint with each band in the footprint representing the corresponding Tn5 mutant. By comparing the footprints from the pools of S. typhimurium Tn5 mutants before and after inoculation on egg shell surfaces, Tn5 mutants not recovered after selection were rapidly identified for potential isolation and genetic analysis.     

Degradation of different pesticides in water by microplasma: the roles of individual radicals and degradation pathways

Environmental Science and Pollution Research - Pesticides are emergent toxins often identified in aquatic environments. In the present study, microplasma was employed to reduce the pesticide...     

Effects of ozonation and coagulation on effluent organic matter characteristics and ultrafiltration membrane fouling

Effluent organic matter （EfOM） is the major cause of fouling in the low pressure membranes process for wastewater reuse. Coagulation and oxidation of biological wastewater treatment effluent have been applied for the fouling control of microfiltration membranes. However, the change in EfOM structure by pre-treatments has not been clearly identified. The changes of EfOM characteristics induced by coagulation and ozonation were investigated through size exclusion chromatography, UV/Vis spectrophotometry, fluorescence spectrophotometry and titrimetric analysis to identify the mechanisms in the reduction of ultrafiltration （UF） membrane fouling. The results indicated that reduction of flux decline by coagulation was due to modified characteristics of dissolved organic carbon （DOC） content. Total concentration of DOC was not reduced by ozonation. However, the mass fraction of the molecules with molecular weight larger than 5 kDa, fluorescence intensity, aromaticity, highly condensed chromophores, average molecular weight and soluble microbial byproducts decreased greatly after ozonation. These results indicated that EfOM was partially oxidized by ozonation to low molecular weight, highly charged compounds with abundant electron- withdrawing functional groups, which are favourable for alleviating UF membrane flux decline.     

Service life of sewage culvert with bacteria coating from waste sludge and negative pressure method

Journal of Material Cycles and Waste Management - In this study, a bacteria coating resistant to sulfate attack using materials with bacteria immobilization has been developed. For core coating...     

Study on Size Distribution of Total Aerosol and Water-Soluble Ions During an Asian Dust Storm Event at Jeju Island, Korea

Soil dust particles transported from loess regions of the Asian continent, called Asian dust, highly influences the air quality of north-eastern Asia and the northern Pacific Ocean. In order to investigate the effects of these dust storms on the chemical composition of atmospheric aerosol particles with different size, measurements of size distributions of total aerosol and major ion species were carried out on Jeju Island, Korea during April 2001. Juju Island was chosen for the study because the levels of emissions of anthropogenic air pollutants are very low. A 5-stage cascade impactor was used to sample size-fractionated aerosol particles. Samples were analyzed for major water-soluble ions using Dionex DX-120 ion chromatograph. The average mass concentration of total aerosol was found to be 24.4 and 108.3 microg m(-3) for non-Asian dust and Asian dust periods, respectively. The total aerosol size distribution, measured during the non-Asian dust period, was bimodal, whereas the coarse particles dominated the size distribution of total aerosol during the Asian dust period. It was found that SO4(2-), NH4+ and K+ were mainly distributed in fine particles, while Cl-, NO3-, Na+, Mg2+ and Ca2+ were in coarse particles. Although SO4(2-) was mainly distributed in fine particles, during the Asian dust period, the concentrations in coarse particles were significantly increased. This indicates heterogeneous oxidation of SO2 on wet surfaces of basic soil dust particles. The NH4+ was found to exist as (NH4)2SO4 in fine particles, with a molar ratio of NH4+ to SO4(2-) of 2.37 and 1.52 for non-Asian dust and Asian dust periods, respectively. Taking into account the proximity of the sampling site to the sea, and the observed chloride depletion, coarse mode nitrate, during the non-Asian dust period, is assumed to originate from the reaction of nitric acid with sodium chloride on the surfaces of sea-salt particles although the chloride depletion was not shown to be large enough to prove this assumption. During the Asian dust period, however, chloride depletion was much smaller, indicating coarse nitrate particles were mainly produced by the reaction of nitric acid with surfaces of basic soil particles. Most chloride and sodium components were shown to originate from sea-salt particles. Asian dust aerosols, arriving at Jeju Island, contained considerable amounts of sea-salt particles as they passed over the Yellow Sea. Ca2+ was shown to be the most abundant species in Asian dust particles.     

Health risk assessment and source apportionment of PM2.5-bound toxic elements in the industrial city of Siheung,Korea

Environmental Science and Pollution Research - The emission sources and their health risks of fine particulate matter (PM2.5) in Siheung, Republic of Korea, were investigated as a middle-sized...     

Microfiber shedding from nonwoven materials including wipes and meltblown nonwovens in air and water environments

Environmental Science and Pollution Research - Nonwoven products are widely used in disposable products, such as wipes, diapers, and masks. Microfibers shed from these products in the aquatic and...