Spatial and temporal water quality characteristics of Poyang Lake Migratory Bird Sanctuary in China

Poyang Lake Migratory Bird Sanctuary includes Bang Lake, Sha Lake, Dahu Lake, and estuaries of the Xiu and Gan Rivers in the Migratory Bird Natural Reserve. Water samples were collected and analyzed to study spatial and temporal water quality variation. Strong seasonal variation of water quality was found. The water quality of Bang Lake was relatively poor compared to Sha and Dahu Lakes in the wet season, but better in the normal season. During the dry season, the water quality of Bang Lake is negatively affected by the activity of migratory birds. According to the correlation analysis of monthly concentrations of each parameter, the concentrations of COD, NH?-4–N, and NO3–N were highly correlated. The correlation index was 0.829 and significance index was0.042 \ 0.05. From north to south within Bang Lake, the concentration of TN decreased; however, the concentration of Chl-a increased. From east to west within Bang Lake,concentrations of COD, NH?4–N, NO-3–N, and Chl-a increased. The Xiu and Gan Rivers influence the water quality of Bang Lake, especially in the northeast area of the lake. The water quality of Bang Lake only reached Chinese water quality standard level IV or V according to a fuzzy comprehensive evaluation. The evaluation factors impacting Bang Lake are TN[TP[NH?4–N[COD, in order of decreasing importance. The waters of Poyang Lake Migratory Bird Sanctuary have been polluted; one of the important contributing factors was migratory birds' disturbance and feces.

Rapid and sensitive method for determining free amino acids in plant tissue by high-performance liquid chromatography with fluorescence detection

This paper describes a reliable and rapid method for the complete separation and quantitation of twenty-five amino acids typically found in plants, based on reversed phase high-performance liquid chromatography–linked fluorescence detector using a 150×4.6 mm Zorbax Eclipse AAA column. Plant tissue free amino acids(FAA)were extracted by ultrasonication with 5%(v/v) aqueous trifluoroacetic acid followed by ultrafiltration of extracts.The following analysis of amino acids was performed through programmed precolumn derivatization with orthophthalaldehyde and 9-fluorenylmethyl chloroformate reagents and efficient elution of derivatives within 26 min using binary gradient scheme. The method was validated over a concentration range of 4.5–450 μmol L^(-1)(μM).Separation analysis showed good selectivity(resolution>1.5) for most amino acids. The average repeatability(RSD%, relative standard deviation) of the analysis at seven calibration concentrations was below 4% and ranged from 1.13% to 12.04%. The intra-day mean coefficient of variation at two concentrations(22.5 and 90 μM) was within 2%, and the intermediate precision was less than 4%. The limits of detection were between 0.012 and 6.68 μM. The coefficients of determination(R2) of the linear calibration curves were from 0.9989 to 0.9999.When the method was applied to plant samples, the FAA recoveries at two spiked levels(25 and 100 μM) ranged from 67.0% to 108.9% with an average of 94.4%, and the precision was 0.26%–12.31% RSD. A specific application combining this method with optimized extraction and interference removal procedures was successfully used to determine the FAA pools in different plant tissues. Finally,a PLS-DA multivariate statistics model was validated for the classification of three plant species according to their FAA profiles.

Do lamprophyric magma carry gold?——Evidence from high temperature and ultrahigh pressure experiments

By taking lamprophyres in the Laowangzhai gold orefield, Yunnan Province, as starting materials, the melting experiments of lamprophyre + gold have been conducted under 1.5 and 3.0 GPa in a DS-29A cubic-type 3 600 t ultrahigh-pressure apparatus. The experimental results showed that gold powder (less than 0.045 mm) which even contributed in the samples be-

Adsorption of fluoride on clay minerals and their mechanisms using X-ray photoelectron spectroscopy

This research investigates the adsorptionmechanisms of fluoride(F)on four clay minerals(kaolinite,montmorillonite,chlorite,and illite)underdifferent F^(-)concentrations and reaction times by probingtheir fluoride superficial layer binding energies and elementcompositions using X-ray photoelectron spectroscopy(XPS).At high F^(-)concentrations(C_(0)=5-1000 mg·L^(-1)),the amount of F^(-)adsorbed(Q_(F)),amount of hydroxidereleased by clay minerals,solution F^(-)concentration,andthe pH increase with increasing C_(0).The increases areremarkable at C_(0)>50 mg·L^(-1).The QF increases significantlyby continuously modifying the pH level.At C_(0)<5-100 mg·L^(-1),clay minerals adsorb H+to protonatealuminum-bound surface-active hydroxyl sites in thesuperficial layers and induce F^(-)binding.As the C_(0)increases,F^(-),along with other cations,is adsorbed toform a quasi-cryolite structure.At C_(0)>100 mg·L^(-1),newminerals precipitate and the product depends on the criticalAl^(3+)concentration.At[Al^(3+)]>10^(-11.94)mol·L^(-1),cryoliteforms,while at[Al^(3+)]<10^(-11.94)mol·L^(-1),AlF_(3) is formed.At low C_(0)(0.3-1.5 mg·L^(-1)),proton transfer occurs,andthe F^(-)adsorption capabilities of the clay minerals increasewith time.