Pei Hua

The qualitative and quantitative source apportionments of polycyclic aromatic hydrocarbons in size dependent road deposited sediment.

This study showcases the qualitative and quantitative source apportionments of size-dependent polycyclic aromatic hydrocarbons (PAHs) in road deposited sediment by means of molecular diagnostic ratio (MDR) and positive matrix factorisation (PMF) approaches. The MDR was initially used to narrow the PAH source candidates. PMF modelling was subsequently used to provide more precise source apportionment with the assistance of a multiple linear regression analysis. Through a combined qualitative and quantitative source apportionment, different potential source contributors were identified at different size fractions. Explicitly, three major contributors to sorption at the size fraction of 1000-400 μm were tentatively identified as incineration (26%), coal combustion (53%) and gasoline-powered vehicle (20%). Four major contributors to the size fraction of 400-100 μm were identified as gasoline-powered vehicle (25%), surface pavement (15%), diesel-powered vehicle (37%) and industrial boiler (24%). Four major contributors to the size fraction of 100-63 μm were identified as cogeneration emission (13%), diesel-powered vehicle (28%), tire debris (45%) and wood combustion (14%). The potential contributors in the size fraction 63-0.45 μm were identified as diesel-powered vehicle (21%), heterogeneous sources (41%) and biomass burning (38%). In addition, the highest ∑16PAH concentration was found in the smallest size fraction of 63-0.45 μm, which is also where the highest BaPE and TEF values for potential risk assessment occurred.

The build-up dynamic and chemical fractionation of Cu, Zn and Cd in road-deposited sediment

This study investigates the build-up dynamics of heavy metals on impervious urban surfaces with different antecedent dry-weather periods (ADPs) and land-use types. Solid-phase concentration (mg/kg), surface load (mg/m(2)), and chemical fractionation of Zn, Cu and Cd in bulk- and size-fractionated road-deposited sediment were determined. The inherent correlations among particle size distribution, ADP, land use, and chemical fractionation were analysed by hierarchical cluster analysis. Results show a clear build-up phenomenon of Cu and Zn at a city commercial centre and a highway area. Cd had complex build-up patterns. With regard to chemical fractionation, Zn and Cd could pose higher risks than Cu to aquatic biota after a longer ADP. Special attention should be paid to the significant risk in a rural area because of the high proportion of exchangeable chemical fractionation in terms of the unstable Cd component. Hierarchical cluster analysis indicates that ADP had a strong influence on build-up processes of sediments and associated metals. The metal contents were very dependent on the particle size distribution. However, the chemical fractionation of metals was dependent to a lesser extent on the land-use type.

The influences of dissolved organic matter and surfactant on the desorption of Cu and Zn from road-deposited sediment.

This study showcases the desorption behaviours of copper (Cu) and zinc (Zn) in road-deposited sediment (RDS). Batch tests were conducted to investigate the influences of rainwater, major wastewater constituents of dissolved organic matter (DOM) and surfactant on the metals leaching from RDS. Results show that the rainwater solutions considerably enhanced the total amounts of Cu (319 ± 46% of the total leaching amount by blank solutions) and Zn (617 ± 130%) released from RDS compared with blank solutions. DOM enhanced the leaching of Cu from RDS at a neutral pH. By contrast, DOM had an adverse effect on the mobilization of Zn. In the absence of DOM, a higher concentration of sodium dodecyl sulfonate (SDS) slightly increased the release of Cu from RDS than a lower concentration of SDS. However, the existence of SDS suppressed the release of Zn from RDS.

The influence of land use on source apportionment and risk assessment of polycyclic aromatic hydrocarbons in road-deposited sediment

The pollution load of urban runoff is boosted due to the washing away of road-deposited sediment (RDS). Therefore, a source-oriented mitigation strategy is essential to integrated stormwater management. This study showcases the influence of land use dependent source apportionment and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in RDS. Samples were collected from areas of different land uses, including commercial city centre, highway, residential rural and campus areas. According to the positive matrix factorisation (PMF) receptor model, different primary sources were identified at different land use areas. Generally, potential sources of gasoline- and diesel-powered engine emissions and other pyrogenic sources of biomass, coal, and wood combustions were identified as main sources of PAH content in RDS. The source specific risks posed by PAHs at different land uses were further estimated by the incremental lifetime cancer risk (ILCR). This shows that the mean ILCRs of the total cancer risk for children and adults at the given land uses were lower than the baseline value of an acceptable risk. However, the potential exposure risk to RDS adsorbed PAHs for children was considerably higher than that for adults. Vehicular emissions and wood combustion were the major contributors to the cancer risk with average contributions of 57 and 29%, respectively.

The chemical fractionation and potential source identification of Cu, Zn and Cd on urban watershed

This study showcases the chemical fractionation and primary source identification of Cu, Zn and Cd in road-deposited sediment. Results show that Zn and Cd were identified as easily mobilised and biologically available metals that pose high risks to the receiving aquatic environments. However, Cu was released in substantial amounts only under relatively extreme conditions. With the assistance of principal component analysis and chemical fractionation, two primary contributors to heavy metals in road-deposited sediment were tentatively identified as vehicle-related sources (especially, auto brake pad erosion for Cu and tyre debris for Zn) and atmospheric deposition (especially for Cd).

Vehicular contribution of PAHs in size dependent road dust: A source apportionment by PCA-MLR, PMF, and Unmix receptor models

This study focuses on the source apportionments of polycyclic aromatic hydrocarbons (PAHs) in road dust (RD) with four size fractions through three receptor models of principal component analysis with multiple linear regression (PCA-MLR), positive matrix factorization (PMF) and Unmix. The concentrations of total PAHs range from 0.45 to 2.03μgg-1. Results show that the concentrations of PAHs increased with a decreasing size fraction. Similar potential sources to PAHs in RD were extracted by three models with a little difference in numbers and percent load contributions of each identified sources. The overall proportion of the identified sources were ranked as vehicular emission>coke oven>surface pavement>others in each size fractions. In terms of risk assessment, the mean values of incremental lifetime cancer risk (ILCR) of the total cancer risk of PAHs in RD were lower than the baseline value of an acceptable risk. However, PAHs in smaller size fraction prone to have a higher adverse effect on children via ingestion. Furthermore, the ecological risk assessment of hazard quotients and mean hazard quotients indicated that PAHs in RD had a 9% probability of being toxic to the benthic organisms and aquatic environment.