[1] To evaluate the wintertime regional brown haze in northern China, trace gases and aerosols were measured at an urban site between 9 and 20 November 2009. Ion chromatography and transmission electron microscopy (TEM) were used to investigate soluble ions in PM 2.5 and the mixing state of individual particles. The contrasts between clear and hazy days were examined in detail. Concentrations of the primary gases including NO (55.62 ppbv), NO 2 (54.86 ppbv), SO 2 (83.03 ppbv), and CO (2.07 ppmv) on hazy days were 2 to 6 times higher than those on clear days. In contrast, concentrations of O 3 remained low (5.71 ppbv) on hazy days. Mass concentrations of PM 2.5 (135.90 mg m −3 ) and BC (7.85 mg m −3 ) were 3 times higher on hazy days than on clear days. Based on the estimations from TEM analysis, fractions of both ammoniated sulfate (AS)-soot (20%) and AS-soot/organic matter/fly ash (20%) were larger on hazy days than on clear days (13% and 12%), implying that coagulation is an important mixing process in the polluted air. The SO 2 emissions from coal combustion for power plants, industrial activities, and household heating led to high concentrations. Also, high concentrations of secondary sulfates significantly formed in the haze. Therefore, high concentrations of acidic gases contributed to the increased mass and number of secondary aerosols. Our study indicates that metal-catalyzed oxidation in the aqueous phase is a major pathway of sulfate formation. The mixtures of aerosol particles, together with MODIS images, suggest that the hazes covered not only the industrial cities, but extended into the neighboring rural regions.

Soybean seeds provide an excellent source of protein for human and livestock nutrition. However, their nutritional quality is hampered by a low concentration of the essential sulfur amino acid, methionine (Met). In order to study factors that regulate Met synthesis in soybean seeds, this study used the Met-insensitive form of Arabidopsis cystathionine γ-synthase (AtD-CGS), which is the first committed enzyme of Met biosynthesis. This gene was expressed under the control of a seed-specific promoter, legumin B4, and used to transform the soybean cultivar Zigongdongdou (ZD). In three transgenic lines that exhibited the highest expression level of AtD-CGS, the level of soluble Met increased significantly in developing green seeds (3.8-7-fold). These seeds also showed high levels of other amino acids. This phenomenon was more prominent in two transgenic lines, ZD24 and ZD91. The total Met content, which including Met incorporated into proteins, significantly increased in the mature dry seeds of these two transgenic lines by 1.8- and 2.3-fold, respectively. This elevation was accompanied by a higher content of other protein-incorporated amino acids, which led to significantly higher total protein content in the seeds of these two lines. However, in a third transgenic line, ZD01, the level of total Met and the level of other amino acids did not increase significantly in the mature dry seeds. This line also showed no significant change in protein levels. This suggests a positive connection between high Met content and the synthesis of other amino acids that enable the synthesis of more seed proteins.

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Abstract. The evolution of physical, chemical and optical properties of urban aerosol particles was characterized during an extreme haze episode in Beijing, PRC, from 24 through 31 January 2013 based on in situ measurements. The average mass concentrations of PM1, PM2.5 and PM10 were 99 ± 67 μg m−3 (average ± SD), 188 ± 128 μg m−3 and 265 ± 157 μg m−3, respectively. A significant increase in PM1-2.5 fraction was observed during the most heavily polluted period. The average scattering coefficient at 550 nm was 877 ± 624 Mm−1. An increasing relative amount of coarse particles can be deduced from the variations of backscattering ratios, asymmetry parameter and scattering Ångström exponent. Particle number-size distributions between 14 and 2500 nm diameter showed high number concentrations, particularly in the nucleation mode and accumulation mode. Size-resolved chemical composition of submicron aerosol from a high-resolution time-of-flight aerosol mass spectrometer showed that the mass concentrations of organic, sulfate, nitrate, ammonium and chlorine mainly resided on particles between 500 and 800 nm (vacuum diameter), and nitrate and ammonium contributed greatly to particle growth during the heavily polluted day (28 January). Increasing relative humidity and stable synoptic conditions on 28 January combined with heavy pollution on 28 January, leading to enhanced water uptake by the hygroscopic submicron particles and formation of secondary aerosol, which might be the main reasons for the severity of the haze episode. Light-scattering apportionment showed that organic, sulfate, ammonium nitrate and ammonium chloride compounds contributed to light-scattering fractions of 54, 24, 12 and 10%, respectively. This study indicated that the organic component in submicron aerosol played an important role in visibility degradation during the haze episode in Beijing.