Search

To investigate the seasonal and spatial variations of carbon fractions in PM2.5 in Ningbo, PM2.5 samples were collected at 5 sites in typical periods of 4 seasons from December 2012 to October 2013. The concentrations of organic carbon (OC) and elemental carbon (EC) were determined and the contribution of secondary organic carbon (SOC) was estimated. The result shows that: (1)the annual average of PM2.5 in Ningbo is 51. 6 µm.m-3. OC and EC account for 17% and 6% respectively. According to the result of the backward trajectory model, the concentrations of PM2.5 in winter and spring are higher mainly because of regional transport from inland China. (2) the OC/EC ratio and the correlation between OC and EC indicate that in summer a large sum of SOC is generated while in winter the influence of coal burning emission for heating in North China may be the main reason for high OC/EC ratio. (3) the contribution of SOC was estimated using an EC tracer method. The result shows that this method is not suitable for both winter and spring because of significant regional transport. The average concentrations of SOC in summer and autumn are 2. 5 µg.m-3 and 2. 3 µg.m-3, accounting for 42% and 28% of total OC respectively.

To investigate the effect of meteorological characteristics on PM2.5 chemical composition and the spatial distribution of different PM2.5 species in Shenzhen, 24-h PM2.5 samples were collected every six days from December 2008 to December 2009. The sampling network included an industrial site at Baoan, an urban site at Luohu and a seaside site at Yantian. Water-soluble inorganic ions and carbonaceous material (organic carbon and elemental carbon) were analyzed. The industrial site showed a much higher concentration than that of other two sites of organic matter, elemental carbon and nitrate, which presented the obvious difference of local emissions. But for the concentration of sulfate and ammonium of three different sites nearly stayed at the same level and indicated that they were mainly influenced by regional transport. OC/EC had the characteristics of the industrial sitethe urban sitethe seaside site, which implied that the industrial site had less secondary organic matter and more primary pollution sources. As the subtropical maritime monsoon climate is the dominant meteorological feature of the Pearl River Delta with a southwesterly transport and abundant rain in spring and summer, in contrast to a northwesterly transport and little rain in fall and winter, the PM2.5 pollution was much more serious in winter than in summer. Compared with the results of the similar experiment in 2004, the concentration of sulfate in PM2.5 has significantly declined because of the measures of reducing the emission of sulfer dioxide. But the pollution of vehicle emissions has become significant.

In order to obtain ammonia volatilization flux and volatilization loss rate in the vegetable field and investigate their relationship with environmental factors, an on-line monitoring system was used to measure the ammonia volatilization in the vegetable (Brassica rapa L. and lettuce) field after urea application during January to September, 2009. The system included a wind tunnel system, a gas collector and an online analyzer system with ion chromatography. The time resolution of measurement was 15 min. The recovery of the system was (92.6 +/- 3.4)%; the accumulated ammonia volatilization within 15 d continuous sampling after fertilization was regarded as the total loss. The accumulated ammonia volatilization of 12 d continuous sampling after fertilization accounted for (85.4 +/- 5.2)% of the total volatilization. The ammonia volatilization loss of broadcasting basal dressing and top dressing for Brassica rapa L. were 23.6% and 21.3%, respectively. The ammonia volatilization loss of holing basal dressing and top dressing for lettuce were 17.6% and 24.0%, respectively. The ammonia volatilization in the vegetable field mostly occurred in the first 2-3 weeks after fertilization. The ammonia volatilization flux had significant positive correlation with the nitrogen application rate, while the ammonia volatilization loss rate had negative correlation with the nitrogen application rate. The ammonia volatilization flux was positively correlated with the soil temperature (r = 0.041, p0.05) and the air temperature (r = 0.049, p0.01), while not significantly associated with the air humidity and the soil moisture. Temperature was found to be a main factor influencing the ammonia volatilization in the vegetable field.

The precipitation chemical components are good indicators of the air pollution. With rapid economic developing, air quality has greatly changed in Shenzhen. To investigate Chemical feature of precipitation and atmospheric pollution characteristics in Shenzhen, two-year precipitation samples in Shenzhen were collected and analyzed. Based on the dataset, chemical characteristics of rainwater in Shenzhen were discussed. Results show that the concentration of the sum of anions and rations in Shenzhen rainwater was lower compared to northern cities like Beijing, whereas the acidification of rainwater was very serious in Shenzhen. Volume-weighted mean pH values of rainwater were 4.48 and 4.68 respectively, and 88% and 91% of rain events were acidic in 2004 and 2005, respectively. The contribution of SO4(2-) to Shenzhen rainwater acidity was smaller than that in northern cities and NO3- and Cl- played an important part to acidification of Shenzhen precipitation. The contribution of Cl- and Na+ to rainwater chemical components was higher, indicating the significant marine influence on Shenzhen precipitation. The secondary components like SO4(2-), NO3- and NH4+ contributed significantly to total ions of rainwater and they accounted for more than 40% of total ions in 2004 and 2005, which indicated the severe secondary pollution in Shenzhen. There was the obvious difference in origins for different rainwater components. Cl-, K+ and Na+ were mainly from marine contribution while SO4(2-), NO3-, Ca2+ and Mg2+ were mainly from non-sea salt fraction. Formic acid, acetic acid and oxalic acid were most abundant low-molecular weight organic acids and the sum of their concentrations accounted for 94% and 99% of total organic acids determined in 2004 and 2005, respectively.

To understand one of the important characteristics of Beijing particulate matter pollution, the mass size distribution of particulate matters and its water-soluble ions, the particle samples were collected by a MOUDI cascade impactor in Beijing during July 2001, March 2002, July 2002 and January 2003 and every sampling period lasted a week. By analysis, the results indicate that there is "two modes" in the diameter range of the fine particle, one called "condensation mode" and another called "droplet mode", and the reasons of the peak of the accumulation mode appearing in the diameter range of 1 - 1. 8 microm was discussed in this paper. And there was a relatively strong correlation between PM1.8 and PM10 (R280%), the same to PM(1.8-10) (PM10 minus PM1.8); the ratio of PM1.8s/PM10 varietied between 40% and 60% during the sampling periods; as a result, the mass concentration of PM10 can be decreased by decreasing the concentration of coarse particles; sulfate, nitrate and ammonium are the main component of the inorganic water-soluble ions and the percentage of these three ions in PM1.8 was above 70% when the concentration of fine particle was more than 70 microg x m(-3) and they are the main reason increasing particle concentration.

Ten water soluble organic acids in PM2.5 of atmosphere in Beijing were determined by capillary electrophoresis, including low molecular weight dicarboxylic acids, aldehyde acids, ketoacids and methanesulfonic acid. The quantified detection limits ranged from 110 to 280 microg/L (extract). The precise of peak area was between 1.7% and 6.0%, and the correlation coefficients of standard curve were 0.995-0.999. The average total concentrations of the ten organic acids in summer, fall and winter were 721 ng/m3, 362 ng/m3 and 325 ng/m3, respectively, which were comparable with some foreign big cities. Oxalic acid was the most abundant species. By exploring seasonal variations of the acids, their source characteristics were simply discussed.

A determination method was developed for the quantification of polar organic compounds in atmospheric fine particles in Beijing City by GC-MS. The optimally reactive conditions of two derivative methods were set up. The related coefficients (R2) of standard curves were 0.995-1.000. The precise of the GC-MS was 1%-10%, and the quantified detection limits ranged from 0.1 to 4.0 ng x microL(-1) depending on the various standard compounds. The percent relative standard deviation of standards and atmospheric samples were 3%-20% and 3%-17%, respectively. The methods were applied for Beijing fine particle samples in summer, fall, and winter in 2002. Total 42 polar organic compounds were identified and quantified, including 30 n-aliphatic and n-alkenoic acid species, 5 aliphatic dicarboxylic acid species, 3 monosaccharide anhydrides, 3 steroids, and benzoic acid. The sources of these compounds were discussed.