ABSTRACT
To investigate the pollution characteristics of carbonaceous components in PM10 and PM2.5 of road dust fall and soil dust in Xi'an and enrich their source profiles, samples from five sites of road dust fall and 16 sites of soil dust were collected in Xi'an from April to May 2015. The ZDA-CY01 particulate matter resuspension sampler was used to obtain PM10 and PM2.5 samples, and the Model5L-NDIR OC and EC analyzer were used to determine the concentrations of organic carbon (OC) and elemental carbon (EC) in PM10 and PM2.5. The pollution and sources of carbonaceous aerosol in PM10 and PM2.5 were investigated by analyzing OC and EC characteristics, ratio, and the principal component analysis statistical model. The results showed that the proportions of OC in PM10 and PM2.5 at the various dust fall sites differed, ranging from 6.0% to 19.4% and 7.6% to 29.8%, respectively. The ratios of EC in PM10 and PM2.5at the different dust fall sites were relatively small, accounting for 0.6%-2.2% and 0.2%-3.6% in urban sites, respectively; however, EC was almost undetectable in most peripheral soil dust. The proportions of carbonaceous components in PM10 and PM2.5 followed the order of urban road dust fall>external control dust>river beach soil dust>soil dust and urban road dust fall>soil dust>external control dust>river beach soil dust, respectively. OC dominated the carbonaceous aerosols at the different sites, which was relatively low in urban road dust fall. The OC to total carbon (TC) ratios in PM10 and PM2.5 at urban road dust fall were 85.2%-95.3% and 87.9%-98.9%, respectively. The OC to TC ratios in PM10 and PM2.5 of soil dust were relatively high, exceeding 99%. Carbonaceous components were primarily concentrated in fine particles. The pollution distribution of carbonaceous components in the urban road dust fall sites was consistent, whereas that in the different soil dust sites were quite different. The carbonaceous components in urban road dust fall and soil dust were primarily affected by pollutant source emissions such as biomass burning, coal burning, gasoline, and diesel vehicle exhaust. There were differences in the source contribution rates of carbonaceous aerosols in PM10 and PM2.5.
ABSTRACT
To study the emission characteristics of carbonaceous aerosol in particulate matter emitted from vehicle exhaust and main civil combustion fuels, organic carbon (OC) and elemental carbon (EC) in PM10 and PM2.5 samples from vehicle sources (gasoline vehicles, light duty diesel vehicles, and heavy duty diesel vehicles), civil coal (chunk coal and briquette coal), and biomass fuels (wheat straw, wood plank, and grape branches) were collected and analyzed by using a multifunctional portable dilution channel sampler and the Model 5L-NDIR OC/EC analyzer. The results showed that there were significant differences in the proportion of carbonaceous aerosols in PM10 and PM2.5from different emission sources. The proportions of total carbon (TC) in PM10 and PM2.5 of different emission sources were 40.8%-68.5% and 30.5%-70.9%, respectively, and the OC/EC were 1.49-31.56 and 1.90-87.57, respectively. The carbon components produced by different emission sources were dominated by OC, and the OC/TC values in PM10 and PM2.5 were 56.3%-97.0% and 65.0%-98.7%, respectively. The proportions of OC in carbonaceous aerosols in PM10and PM2.5 were in the descending order of:briquette coal>chunk coal>gasoline vehicle>wood plank>wheat straw>light duty diesel vehicle>heavy duty diesel vehicle and briquette coal>gasoline car>grape branches>chunk coal>light duty diesel vehicle>heavy duty diesel vehicle, respectively. The main components of carbonaceous aerosols in PM10 and PM2.5 emitted from the various emission sources were different, and source apportionment of carbonaceous aerosols could be accurately distinguished by their ingredient composition profiles.
ABSTRACT
Since the electrochemical oxidation peaks of both DNA and anti-tumor drug tamoxifen (TAM) overlapped with each other, the known electrochemical methods were limited in the study of the interactions between DNA and TAM. In this paper, zero current potentiometry, a new electrochemical method, was used to study the interaction of calf thymus dsDNA with TAM. The dsDNA was immobilized on the surface of carbon paste (dsDNA/CP). The dsDNA/CP connected in series between the clips of working and counter electrodes of a potentiostat and a reference electrode were immersed in aqueous solution containing TAM, the interaction of dsDNA with TAM produced a change in interfacial potential at the dsDNA/CP/solution interface. When linear sweep potential was applied to the dsDNA/CP and the corresponding I-E curve was recorded, interfacial potential offset applied potential partially, making the I-E curve displace along potential axis. Zero current potential where circuit current I was equal to zero in the I-E curve was measured to check the displacement of the I-E curve. Based on the displacement, the thermodynamic constants of the interaction between dsDNA and TAM were determined. The binding ratio of dsDNA with TAM was found to be 1:1 and the apparent binding constant was (6.85±0.20)×10(6) M(-1). As zero current potentiometry was independent of the changes in redox potential or current of both dsDNA and TAM themselves, the interaction was studied in their natural forms without damage. Moreover, TAM can be determined. The detection limit was 1.1×10(-7) M.
