In order to study deposited sediment settlement and consolidation mechanisms, sediment settlement experiments were conducted using a settlement column. Based on the experimental results, sediment settlement stage defi...In order to study deposited sediment settlement and consolidation mechanisms, sediment settlement experiments were conducted using a settlement column. Based on the experimental results, sediment settlement stage definition, excessive pore pressure （EPP） dissipation, and consolidation constitutive equations are discussed. Three stages, including the free settlement, hindered settlement, and self-weight consolidation settlement stages, are defined. The results of this study show that sediment settlement is mainly affected by the initial sediment concentration and initial settlement height, and the interface settlement rate is linearly attenuated with time on bilogarithmic scales during the hindered settlement and self-weight consolidation settlement stages. Moreover, the deposited sediment layer in the self-weight consolidation settlement stage experiences large strains, and the settlement amount in this stage is about 32% to 59% of the initial height of deposited sediment. EPP is nonlinearly distributed in the settlement direction, and consolidation settlement is faster than EPP dissipation in the self-weight consolidation settlement stage. Consolidation constitutive equations for the hydraulic conductivity and effective stress, applicable to large-strain consolidation calculation, were also determined and fitted in the power function form.展开更多
Stormwater runoff derived from the wash-off of road-deposited sediments (RDS), contains elevated heavy metal (HM) concentrations and, thus, imposes an increasing threat to urban aquatic ecosystems. In-depth understand...Stormwater runoff derived from the wash-off of road-deposited sediments (RDS), contains elevated heavy metal (HM) concentrations and, thus, imposes an increasing threat to urban aquatic ecosystems. In-depth understanding of the variations of HMs pollution from RDS to stormwater during transport processes facilitates the development of effective RDS and stormwater control strategies. Toward this end, the distribution of HMs (Cu, Pb, Zn, Cr, and Ni) in RDS and stormwater were investigated simultaneously. The results show a preferential accumulation of Pb and Zn in the finer (< 38.5μm) RDS, and Cu, Cr and Ni in the coarser (38.5-150μm) RDS. For stormwater, n.d.~48.6% of HMs fractionated into the dissolved phase, and stormwater particles constitute the primary carriers of HMs. Furthennore, the accumulation of HMs in stormwater particles increased linearly with finer particle size distributions (PSD). Geoaccumulation index (Igeo) highlighted the predominant pollution of both RDS and stormwater particles by Cu, Pb and Zn. Nonetheless, Cu, Pb, and Ni mostly contributed the potential ecological risk of RDS, whereas Cu, Pb, and Zn mainly contributed that of stormwater particles. Moreover, contamination by Cu, Pb and Zn was significantly higher in stormwater particles than that in RDS. These differences are attributable to the solubility and size-dependent accumulation of HMs in RDS, as well as the PSD variations during transport processes. The study outcomes highlight the importance of very fine (nano- and submicron- scale) RDS in stormwater pollution and the necessity of control.展开更多
Road-deposited sediments(RDS)accumulated on road surfaces are an important environmental medium that often provides transport for heavy metals.In order to understand the characteristics of heavy metals in RDS,we inves...Road-deposited sediments(RDS)accumulated on road surfaces are an important environmental medium that often provides transport for heavy metals.In order to understand the characteristics of heavy metals in RDS,we investigated the size distribution and heavy metal(i.e.Cd,Cr,Cu,Ni,Pb and Zn)concentrations in RDS and road runoff in typical expressways of suburban and rural area in China.The results demonstrated that RDS particles from all impervious expressway surfaces were predominantly coarse particles(>250μm,58.4%±3.8%)and the RDS on all expressways contained more heavy metals than background soils.Furthermore,the concentrations of Cd,Cr,Cu,Ni,Pb and Zn increased with traffic volume,suggesting that these heavy metals are mainly derived from traffic activities.Moreover,it is found that although heavy metals were concentrated in fine grain fractions,the total loading is highest for the coarsest particles due to their large mass percentage.Additionally,it reveals that the heavy metal concentrations in road runoff of suburban expressway are higher than that in urban expressway.Our findings enhance the understanding of expressway pollution,and imply that for controlling runoff pollution from RDS,transportation agencies should be concerned with both fine and coarse particles and take cleaning methods into account.展开更多
The 25 road-deposited sediments were collected from five different land-use zones （industrial, residential, commercial, park, and countryside） in Hangzhou, China. The concentrations of metals （Cd, Co, Cr, Cu, Fe, M...The 25 road-deposited sediments were collected from five different land-use zones （industrial, residential, commercial, park, and countryside） in Hangzhou, China. The concentrations of metals （Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn） in these samples were determined using ICP-AES after digestion with the mixture of HNO3-HF-HC1 （aqua regia）, and chemically fractionated according to the modified BCR （the European Community Bureau of Reference） sequential extraction procedure. The high metal concentration levels were detected in the sample from industrial zone and commercial zone having heavy traffic. While the low metal levels were noted in the street dust sample from residential zone, park, and countryside zone. The mobility sequence based on the sum of the BCR sequential extraction stages was： Zn （80.28%）, Pb （78.68%）, Cd （77.66%） 〉 Cu （73.34%） 〉 Mn （67.92%） 〉 Co （41.66%） 〉 Ni （30.36%） 〉 Cr （21.56%）, Fe （20.86%）. Correlation analysis and principal component analysis were applied to the data matrix to evaluate the analytical results and to identify the possible pollution sources of metals. Factor analysis showed that these areas were mainly contaminated by three sources, namely lithology, traffic, and industry.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.2009B13514)the Doctoral Fund of the Ministry of Education of China(Grant No.20100094110002)
文摘In order to study deposited sediment settlement and consolidation mechanisms, sediment settlement experiments were conducted using a settlement column. Based on the experimental results, sediment settlement stage definition, excessive pore pressure （EPP） dissipation, and consolidation constitutive equations are discussed. Three stages, including the free settlement, hindered settlement, and self-weight consolidation settlement stages, are defined. The results of this study show that sediment settlement is mainly affected by the initial sediment concentration and initial settlement height, and the interface settlement rate is linearly attenuated with time on bilogarithmic scales during the hindered settlement and self-weight consolidation settlement stages. Moreover, the deposited sediment layer in the self-weight consolidation settlement stage experiences large strains, and the settlement amount in this stage is about 32% to 59% of the initial height of deposited sediment. EPP is nonlinearly distributed in the settlement direction, and consolidation settlement is faster than EPP dissipation in the self-weight consolidation settlement stage. Consolidation constitutive equations for the hydraulic conductivity and effective stress, applicable to large-strain consolidation calculation, were also determined and fitted in the power function form.
基金the National Natural Science Foundation of China (Grant No. 51508447)the National Program of Water Pollution Control in China (Grant No. 2014ZX07305-002)+1 种基金the National Key Technology Support Program (Grant No. 2014BAC13B06)Program for Innovative Research Team in Shaanxi (PIRT)(Grant No. 2013KCT-13).
文摘Stormwater runoff derived from the wash-off of road-deposited sediments (RDS), contains elevated heavy metal (HM) concentrations and, thus, imposes an increasing threat to urban aquatic ecosystems. In-depth understanding of the variations of HMs pollution from RDS to stormwater during transport processes facilitates the development of effective RDS and stormwater control strategies. Toward this end, the distribution of HMs (Cu, Pb, Zn, Cr, and Ni) in RDS and stormwater were investigated simultaneously. The results show a preferential accumulation of Pb and Zn in the finer (< 38.5μm) RDS, and Cu, Cr and Ni in the coarser (38.5-150μm) RDS. For stormwater, n.d.~48.6% of HMs fractionated into the dissolved phase, and stormwater particles constitute the primary carriers of HMs. Furthennore, the accumulation of HMs in stormwater particles increased linearly with finer particle size distributions (PSD). Geoaccumulation index (Igeo) highlighted the predominant pollution of both RDS and stormwater particles by Cu, Pb and Zn. Nonetheless, Cu, Pb, and Ni mostly contributed the potential ecological risk of RDS, whereas Cu, Pb, and Zn mainly contributed that of stormwater particles. Moreover, contamination by Cu, Pb and Zn was significantly higher in stormwater particles than that in RDS. These differences are attributable to the solubility and size-dependent accumulation of HMs in RDS, as well as the PSD variations during transport processes. The study outcomes highlight the importance of very fine (nano- and submicron- scale) RDS in stormwater pollution and the necessity of control.
基金supported by Central Public-interest Scientific Institution Basal Research Fund (No.20160604)Con-struction&Technology Projects in Ministry of Transportation (No.2014316670070,No.20113186701290)Construction&Technology Projects in Department of Transportation of Jilin Province (No.2014-4-1-7).
文摘Road-deposited sediments(RDS)accumulated on road surfaces are an important environmental medium that often provides transport for heavy metals.In order to understand the characteristics of heavy metals in RDS,we investigated the size distribution and heavy metal(i.e.Cd,Cr,Cu,Ni,Pb and Zn)concentrations in RDS and road runoff in typical expressways of suburban and rural area in China.The results demonstrated that RDS particles from all impervious expressway surfaces were predominantly coarse particles(>250μm,58.4%±3.8%)and the RDS on all expressways contained more heavy metals than background soils.Furthermore,the concentrations of Cd,Cr,Cu,Ni,Pb and Zn increased with traffic volume,suggesting that these heavy metals are mainly derived from traffic activities.Moreover,it is found that although heavy metals were concentrated in fine grain fractions,the total loading is highest for the coarsest particles due to their large mass percentage.Additionally,it reveals that the heavy metal concentrations in road runoff of suburban expressway are higher than that in urban expressway.Our findings enhance the understanding of expressway pollution,and imply that for controlling runoff pollution from RDS,transportation agencies should be concerned with both fine and coarse particles and take cleaning methods into account.
基金supported by the Natural Science Foun-dation of Zhejiang Province, China (No. R306011)the National Basic Research Program (973) of China (No.2005CB121104)the National Natural Science Foundation of China (No. 40771090).
文摘The 25 road-deposited sediments were collected from five different land-use zones （industrial, residential, commercial, park, and countryside） in Hangzhou, China. The concentrations of metals （Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn） in these samples were determined using ICP-AES after digestion with the mixture of HNO3-HF-HC1 （aqua regia）, and chemically fractionated according to the modified BCR （the European Community Bureau of Reference） sequential extraction procedure. The high metal concentration levels were detected in the sample from industrial zone and commercial zone having heavy traffic. While the low metal levels were noted in the street dust sample from residential zone, park, and countryside zone. The mobility sequence based on the sum of the BCR sequential extraction stages was： Zn （80.28%）, Pb （78.68%）, Cd （77.66%） 〉 Cu （73.34%） 〉 Mn （67.92%） 〉 Co （41.66%） 〉 Ni （30.36%） 〉 Cr （21.56%）, Fe （20.86%）. Correlation analysis and principal component analysis were applied to the data matrix to evaluate the analytical results and to identify the possible pollution sources of metals. Factor analysis showed that these areas were mainly contaminated by three sources, namely lithology, traffic, and industry.
