The formation potential of four trihalomethanes （THMFP） and seven haloacetic acids （HAA7FP） in 13 source waters taken from four major water basin areas in China was evaluated using the simulated distribution syst...The formation potential of four trihalomethanes （THMFP） and seven haloacetic acids （HAA7FP） in 13 source waters taken from four major water basin areas in China was evaluated using the simulated distribution system （SDS） chlorination method. The specific ultraviolet absorbance （SUVA254： the ratio of UV254 to dissolved organic carbon （DOC））, which ranged between 0.9 and 5.0 L/（mg.m）, showed that the organic compounds in different source waters exhibited different reactivities with chlorine. The HAA7FP of source waters ranged from 20 to 448 μg/L and the THMFP ranged from 29 to 259 μg/L. The HAA7FP concentrations were higher than the THMFP concentrations in all but one of the samples. Therefore, the risks of haloacetic acids （HAAs） should be of concern in some source waters. TCM （chloroform） and BDCM （bromodichloromethane） were the major THM constituents, while TCAA （trichloroacetic acid） and DCAA （dichloroacetic acid） were the major HAA species. Br-THM （brominated THM species） were much higher than Br- HAA （brominated HAA species）, and the formation of Br-DBP （Br-THM and Br-HAA） should be of concern when the bromide concentration is over 100 μg/L.展开更多
Permeability is a major indicator of concrete durability,and depends primarily on the microstructure characteristics of concrete,including its porosity and pore size distribution.In this study,a variety of concrete sa...Permeability is a major indicator of concrete durability,and depends primarily on the microstructure characteristics of concrete,including its porosity and pore size distribution.In this study,a variety of concrete samples were prepared to investigate their microstructure characteristics via nuclear magnetic resonance(NMR),mercury intrusion porosimetry(MIP),and X-ray computed tomography(X-CT).Furthermore,the chloride diffusion coefficient of concrete was measured to explore its correlation with the microstructure of the concrete samples.Results show that the proportion of pores with diameters<1000 nm obtained by NMR exceeds that obtained by MIP,although the difference in the total porosity determined by both methods is minimal.X-CT measurements obtained a relatively small porosity;however,this likely reflcts the distribution of large pores more accurately.A strong correlation is observed between the chloride diffusion coefficient and the porosity or contributive porosity of pores with sizes<1000 nm.Moreover,microstructure parameters measured via NMR reveal a lower correlation coefficient R2 versus the chloride diffusion coefficient relative to the parameters determined via MIP,as NMR can measure non-connected as well as connected pores.In addition,when analyzing pores with sizes>50 um,X-CT obtains the maximal contributive porosity,followed by MIP and NMR.展开更多
基金supported by the High-Tech Research and Development Program (863) of China(No.2007AA06A414)the National Basic Research Development Program (973) of China(No. 2006CB403306)the Chinese Academy of Sciences Major Projects of Knowledge Innovation Program(No. KZCX1-YW-06)
文摘The formation potential of four trihalomethanes （THMFP） and seven haloacetic acids （HAA7FP） in 13 source waters taken from four major water basin areas in China was evaluated using the simulated distribution system （SDS） chlorination method. The specific ultraviolet absorbance （SUVA254： the ratio of UV254 to dissolved organic carbon （DOC））, which ranged between 0.9 and 5.0 L/（mg.m）, showed that the organic compounds in different source waters exhibited different reactivities with chlorine. The HAA7FP of source waters ranged from 20 to 448 μg/L and the THMFP ranged from 29 to 259 μg/L. The HAA7FP concentrations were higher than the THMFP concentrations in all but one of the samples. Therefore, the risks of haloacetic acids （HAAs） should be of concern in some source waters. TCM （chloroform） and BDCM （bromodichloromethane） were the major THM constituents, while TCAA （trichloroacetic acid） and DCAA （dichloroacetic acid） were the major HAA species. Br-THM （brominated THM species） were much higher than Br- HAA （brominated HAA species）, and the formation of Br-DBP （Br-THM and Br-HAA） should be of concern when the bromide concentration is over 100 μg/L.
基金Thanks to the financial supports provided by the Natural Science Foundation of Zhejiang Province(LY17E090007,LQ18G010007,and LY19E90006)the National Natural Science Foundation of China(Grant No.51279181).
文摘Permeability is a major indicator of concrete durability,and depends primarily on the microstructure characteristics of concrete,including its porosity and pore size distribution.In this study,a variety of concrete samples were prepared to investigate their microstructure characteristics via nuclear magnetic resonance(NMR),mercury intrusion porosimetry(MIP),and X-ray computed tomography(X-CT).Furthermore,the chloride diffusion coefficient of concrete was measured to explore its correlation with the microstructure of the concrete samples.Results show that the proportion of pores with diameters<1000 nm obtained by NMR exceeds that obtained by MIP,although the difference in the total porosity determined by both methods is minimal.X-CT measurements obtained a relatively small porosity;however,this likely reflcts the distribution of large pores more accurately.A strong correlation is observed between the chloride diffusion coefficient and the porosity or contributive porosity of pores with sizes<1000 nm.Moreover,microstructure parameters measured via NMR reveal a lower correlation coefficient R2 versus the chloride diffusion coefficient relative to the parameters determined via MIP,as NMR can measure non-connected as well as connected pores.In addition,when analyzing pores with sizes>50 um,X-CT obtains the maximal contributive porosity,followed by MIP and NMR.
