Analyzing and understanding the effects of ambient pollution on plants is getting more and more attention as a topic of environmental biology.A method based on synchrotron radiation X-ray fluorescence and X-ray absorption near edge structure spectroscopy was established to analyze the sulfur concentration and speciation in mature camphor tree leaves （CTLs）,which were sampled from 5 local fields in Shanghai,China.Annual SO2 concentration,SO42-concentration in atmospheric particulate,SO42-and sulfur concentration in soil were also analyzed to explore the relationship between ambient sulfur sources and the sulfur nutrient cycling in CTLs.Total sulfur concentration in mature camphor tree leaves was 766-1704 mg/kg.The mainly detected sulfur states and their corresponding compounds were ＋6 （sulfate,include inorganic sulfate and organic sulfate）,＋5.2 （sulfonate）,＋2.2 （suloxides）,＋0.6 （thiols and thiothers）,＋0.2 （organic sulfides）.Total sulfur concentration was strongly correlated with sulfate proportion with a linear correlation coefficient up to 0.977,which suggested that sulfur accumulated in CTLs as sulfate form.Reduced sulfur compounds （organic sulfides,thiols,thioethers,sulfoxide and sulfonate） assimilation was sufficed to meet the nutrient requirement for growth at a balanced level around 526 mg/kg.The sulfate accumulation mainly caused by atmospheric sulfur pollution such as SO2 and airborne sulfate particulate instead of soil contamination.From urban to suburb place,sulfate in mature CTLs decreased as the atmospheric sulfur pollution reduced,but a dramatic increase presented near the seashore,where the marine sulfate emission and maritime activity pollution were significant.The sulfur concentration and speciation in mature CTLs effectively represented the long-term biological accumulation of atmospheric sulfur pollution in local environment.
Source characterization of heavy metals is prerequisite to assessing their potential contamination pathways and environmental risks,based on which pollution control and environmental remediation measures can be properly targeted.In the present study,recent progress in methodologies of source identification of heavy metals in solid waste are summarized.The key scientific concerns related to these methodologies based on the total contents,chemical speciation,isotopic composition,and single-particle signature are also discussed.Finally,prospective research with regard to source identification of heavy metals in solid waste is discussed according to current research conditions and progress.
Sulfate, nitrate and ammonium （SNA） are the dominant species in secondary inorganic aerosol, and are considered an important factor in regional haze formation. Size-fractionated aerosol particles for a whole year were collected to study the size distribution of SNA as well as their chemical species in Shanghai. SNA mainly accumulated in fine particles and the highest average ratio of SNA to particulate matter （PM） was observed to be 47% in the fine size fraction （0.49-0.95 ~tm）. Higher sulfur oxidation ratio and nitrogen oxidation ratio values were observed in PM of fine size less than 0.95 ~tm. Ion balance calculations indicated that more secondary sulfate and nitrate would be generated in PM of fine size （0.49-0.95 p.m）. Sulfur K-edge X-ray absorption near-edge structure （XANES） spectra of typical samples were analyzed. Results revealed that sulfur mainly existed as sulfate with a proportion （atomic basis） more than 73% in all size of PM and even higher at 90% in fine particles. Sulfate mainly existed as （NH4）2SO4 and gypsum in PM of Shanghai. Compared to non-haze days, a dramatic increase of （NH4）2SO4 content was found in fine particles on haze days only, which suggested the promoting impact of （NH4）2SO4 on haze formation. According to the result of air mass backward trajectory analysis, more （NH4）2SO4 would be generated during the periods of air mass stagnation. Based on XANES, analysis of sulfate species in size-fractionated aerosol particles can be an effective way to evaluate the impact of sulfate aerosols on regional haze formation.
