Distinguishing the sources of Asian dust based on electron spin resonance signal intensity and crystallinity of quartz

IEECAS SKLLQG

Characteristics and sources of formic；acetic and oxalic acids in PM2.5 and PM10 aerosols in Beijing；China

IEECAS SKLLQG

Characterization and sources of regional-scale transported carbonaceous and dust aerosols from different pathways in coastal and sandy land areas of China

IEECAS SKLLQG

Sorption of metals on humic acid

The sorption on humic acid (HA) of metals from an aqueous solution containing Hg(II). Fe(III), Pb, Cu, Al, Ni, Cr(III), Cd, Zn, Co and Mn, was investigated with special emphasis on effects of pH, metal concentration and HA concentration. The sorption efficiency tended to increase with rise in pH, decrease in metal concentration and increase in HA concentration of the equilibrating solution. At pH 2.4. the order of sorption was: Hg Fe Pb Cu=Al Ni Cr=Zn=Cd=Co=Mn. At pH 3.7. the order was: Hg and Fe were always most readily removed, while Co and Mn were sorbed least readily. There were indications of competition for active sites (CO2H and phenolic OH groups) on the HA between the different metals. We were unable to find correlations between the affinities of the eleven metals to sorb on HA and their atomic weights, atomic numbers, valencies, and crystal and hydrated ionic radii. The sorption of the eleven metals on the HA could be described by the equation Full-size image (1K), where Y = % metal removed by HA; X = mgHA; and A and B are empirical constants

FACTOR-ANALYSIS SPECTROPHOTOMETRY FOR THE SIMULTANEOUS DETERMINATION OF VALENCE STATES OF METALS

Two M(n+)-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol systems for the simultaneous determination of the valence states of Cr and Fe using factor analysis were studied. (1) At pH 4.0, Cr(III) and Cr(VI) react with the reagent to form stable complexes and a slight difference in the wavelengths of maximum absorption (lambda(max.)) between the two complexes is observed when the sodium lauryl sulfate, which also acts as a solubilizing and sensitizing agent, is added, viz., 590 nm for Cr(III) and 593 nm for Cr(VI) complexes. (2) In the presence of ethanol, both Fe(II) and Fe(III) form 1:2 complexes with the reagent at pH 2.5-3.5 and the lambda(max.) of the Fe(II) and Fe(III) complexes is at 557 and 592 nm, respectively. In the target transformation factor analysis, the K coefficients calculated from the standard mixtures by classical least-squares analysis and a non-zero intercept added to each wavelength are used as the target vector instead of the pure component standards; this can decrease the analysis errors introduced by the interaction between the two species and by deviations from Beer's law.

Distribution and mobility of metals in agricultural soils near a copper smelter in South China

The distribution and mobility of heavy metals in the paddy soils surrounding a copper smelting plant in south China was investigated. We assessed the degree of metal contamination using an index of geoaccumulation. The metals were divided into two groups: (1) Cu, Zn, Pb and Cd, whose concentrations were heavily affected by anthropogenic inputs, and (2) Ni, Co and Cr, which were mainly of geochemical origin. Concentrations of Cu, Cd, Zn, and Pb in the polluted soils were higher than the Chinese soil quality criteria. The chemical partitioning patterns of Pb, Zn and Cu indicated that Pb was largely associated with the residual and NH2OH HCl extractable fractions. In contrast, Cd was predominantly associated with the MgCl2 extractable fraction. A large proportion of Cu was bound to the acidic H2O2 extractable fractions, while Zn was predominantly found in the residual phase. The fraction of mobile species, which potentially is the most harmful to the environment, was found to be elevated compared to unpolluted soils in which heavy metals are more strongly bound to the matrix. The mobility of the metals was studied by water extraction using a modification of Tessier's procedure, and the order of mobility was Zn > Cd > Cu > Ce > Pb.

Food sources of three bivalves living in two habitats of Jiaozhou Bay (Qingdao, China): Indicated by lipid biomarkers and stable isotope analysis

Food Sources of three filter-feeding bivalves from two habitats (intertidal oyster Crassostrea gigas, mussel Mytilus galloprovincialis. and subtidal cultured scallop Chlamys farreri) of Jiaozhou Bay (Qingdao,China) were determined by fatty acid and stable isotope in analysis. Cultured scallop was characterized by significant diatom markets such as 16:1/16:0 close to 1 and high ratio of 20:5(n - 3)/22:6(n - 3), hence we assume that the scallop mainly feeds on diatoms. Fatty acid biomarkers specific to bacteria and terrestrial materials were also found in considerable amounts in scallop tissue, which suggested that there were Substantial bacterial and terrestrial input into the food of the species. Intertidal oyster and mussel, however, exhibited significant flagellate marker. 22:6(n - 3). and lower level of diatom markers. which indicated that flagellates are also part of intertidal bivalves' Planktonic food Sources: meanwhile, high level of Chlorophyta fatty acid marker, Sigma 18:2(n - 6) + 18:3(n - 3), suggested that Ulva pertusa (Chlorophyta) seaweed bed supplied important food sources to intertidal bivalves. Additionally, result of stable isotope analysis showed that phytoplankton contributed 86.2 to 89.0% to intertidal bivalves' carbon budget; macroalga U. pertusa origin source had a contribution of MIX, to 11.0%, which indicated its role Lis in important supplemental food source to intertidal bivalves. From this study. it is concluded that the dietary difference of three bivalves probably relates to the different potential food sources in the scallop farm and intertidal zone in Jiaozhou Bay.

Influence of biofilms growth on corrosion potential of metals immersed in seawater

The changes of corrosion potential (E-corr) of metals immersed in seawater were investigated with electrochemical technology and epifluoresence microscopy. In natural seawater, changes of E-corr were determined by the surface corrosion state of the metal. E-corr of passive metals exposed to natural seawater shifted to noble direction for about 150 mV in one day and it didn't change in sterile seawater. The in-situ observation showed that biofilms settled on the surfaces of passive metals when E-corr moved in noble direction. The bacteria number increased on the metal surface according to exponential law and it was in the same way with the ennoblement of E-corr. The attachment of bacteria during the initial period played an important role in the ennoblement of E-corr and it is believed that the carbohydrate and protein in the biofilm are reasons for this phenomenon. The double layer capacitance (C-dl) of passive metals decreased with time when immersed in natural seawater, while remained almost unchanged in sterile seawater. The increased thickness and reduced dielectric constant of C-dl may be reasons.