An optimized procedure based on gas chromatography-mass spectrometry (GC-MS) combined with accelerated solvent extraction (ASE) is developed for the analysis of six phthalic acid esters (PAEs), which are priority soil pollutants nominated by United States Environmental Protection Agency (USEPA). Quantification of PAEs in soil employs ultrasonic extraction (UE) (USEPA 3550) and ASE (USEPA 3545), followed by clean up procedures involving three different chromatography columns and two combined elution methods. GC-MS conditions under selected ion monitoring (SIM) mode are described and quality assurance and quality control (QA/QC) criteria with high accuracy and sensitivity for target analytes were achieved. Method reliability is assured with the use of an isotopically labeled PAE, di-n-butyl phthalate-d4 (DnBP-D4), as a surrogate, and benzyl benzoate (BB) as an internal standard, and with the analysis of certified reference materials (CRM). QA/QC for the developed procedure was tested in four PAE-spiked soils and one PAE-contaminated soil. The four spiked soils were originated from typical Chinese agricultural fields and the contaminated soil was obtained from an electronic waste dismantling area. Instrument detection limits (IDLs) for the six PAEs ranged 0.10–0.31 μg·L-1 and method detection limits (MDLs) of the four spiked soils varied from a range of 20–70 μg·kg-1 to a range of 90– 290 μg·kg-1. Linearity of response between 20 μg·L-1 and 2 mg·L-1 was also established and the correlation coefficients (R) were all>0.998. Spiked soil matrix showed relative recovery rates between 75 and 120% for the six target compounds and about 93% for the surrogate substance. The developed procedure is anticipated to be highly applicable for field surveys of soil PAE pollution in China. 相似文献
Through high pressure oedometer-undrained triaxial tests and dynamic triaxial tests, researches were conducted on the static and dynamic strength characteristics of the tailings silty sand of No. 4 tailings reservoir in De-xing copper mine. The Mohr-stress circles of the tailings silty sand under all the testing confining pressure show that the single line failure envelope cannot represent the strength characteristics absolutely, the double line failure envelope can express the strength properties when confining pressures are less than 1400 kPa, and the parabolic failure envelope can reflect the strength characteristics well under all the testing confining pressures. The grading curve of the tailings silty sand indicates that the grain composition is relatively homogeneous. Thus, the tailings silty sand is susceptible to liquefy under the dynamic loading. Dynamic triaxial tests of the tailings silty sand show that the tailings silty sand in deep areas has more liquefaction resistance strengths than in shallow. The possible explanation is that the structure of the deep tailings silty sand is more stable than the shallow one. The tests also reveal that the liquefaction resistance increases with the dry density when it is in the range of 1.51-1.61. The results can be used to guide the construction and ensure the safety of No. 4 tailings dam or other high tailings dams. 相似文献
Combustion-generated hydrogen chloride （HCl） is considered to be a very hazardous acid gaseous pollutant. This paper presents a laboratory study on the dry adsorption of HCl. The experiments were conducted in a dual-layer granular bed filter, at gas temperatures of 500℃-700℃ and n（Ca）/n（Cl）molar ratios of 1.0-5.0 using the silver nitrate titration method by dry adsorbent powders Ca（OH）2. Mainly, the adsorption efficiency of HCI and utilization efficiency of Calcium were studied, by varying relevant factors including n（Ca）/n（Cl）, tempera- ture, feeding method, water vapor and CO2. With a relatively higher HCl concentration of 1000ppm, the experimental results revealed that 600℃ may be the optimum temperature for HCl adsorption when optimum n （Ca）/n（Cl） was 2.5 in our tests. The results also demonstrated that the feeding at a constant pressure was more effective, and the HCl adsorption efficiency could rapidly reach over 90% with n（Ca）/n（Cl） = 2.5 at 600℃. Furthermore, the HCl adsorption efficiency was found to be slightly promoted by water vapor, while could be impeded by CO2, and the utilization efficiency of calcium could be up to 74.4% without CO2, while was only 36.8% with CO2 when n（Ca）/n（Cl） was 2.5 at 600℃. 相似文献
The novel microwave catalyst MgFe2O4-SiC was synthesized via sol-gel method, to remove azo dye Direct Black BN (DB BN) through adsorption and microwave-induced catalytic reaction. Microwave-induced catalytic degradation of DB BN, including adsorption behavior and its influencing factors of DB BN on MgFe2O4-SiC were investigated. According to the obtained results, it indicated that the pseudo-second-order kinetics model was suitable for the adsorption of DB BN onto MgFe2O4-SiC. Besides, the consequence of adsorption isotherm depicted that the adsorption of DB BN was in accordance with the Langmuir isotherm, which verified that the singer layer adsorption of MgFe2O4-SiC was dominant than the multi-layer one. The excellent adsorption capacities of MgFe2O4-SiC were kept in the range of initial pH from 3 to 7. In addition, it could be concluded that the degradation rate of DB BN decreased over ten percent after the adsorption equilibrium had been attained, and the results from the result of comparative experiments manifested that the adsorption process was not conducive to the process of microwave-induced catalytic degradation. The degradation intermediates and products of DB BN were identified and determined by GC-MS and LC-MS. Furthermore, combined with the catalytic mechanism of MgFe2O4-SiC, the proposed degradation pathways of DB BN were the involution of microwave-induced $OH and holes in this catalytic system the breakage of azo bond, hydroxyl substitution, hydroxyl addition, nitration reaction, deamination reaction, desorbate reaction, dehydroxy group and ring-opening reaction.
