Characteristics of particle size distribution and related contaminants of highway-deposited sediment, Maanshan City, China

Road-deposited sediment (RDS) has been identified as both the source and sink of various pollutants. In this study, the highway-deposited sediment (HDS) in Spring, Summer, Autumn and Winter was characterized. On average, the mass proportions of particles with the size of 830-4750 μm, 500-830 μm, 250-500 μm, 150-250 μm, 63-150 μm and < 63 μm were 23.6 ± 8.6%, 16.9 ± 3.4%, 28.4 ± 3.5%, 10.0 ± 4.3%, 15.7 ± 5.8% and 5.3 ± 2.0%, respectively, wherein the HDS of 63-830 μm accounted for 71% of the total mass load. It was observed that the particle size distribution of HDS could be described using the gamma distribution function based on gravimetric and cumulative basis (R² (determination coefficient) = 0.9960-0.9995). The bulk pollutant contents of HDS showed seasonal variation with the mean of COD (chemical oxygen demand), nitrogen, phosphorus, Zn (zinc), Pb (lead) and Cd (cadmium) as 57 g/kg, 839 mg/kg, 97 mg/kg, 627 mg/kg, 110 mg/kg and 1.00 mg/kg and the highest COD of 83 g/kg in Autumn, nitrogen 1164 mg/kg Autumn, phosphorus 133 mg/kg Winter, Zn 801 mg/kg Summer, Pb 133 mg/kg Spring and the highest Cd of 1.36 mg/kg in Summer, respectively. The contents of Zn, Pb and Cd in HDS were significantly above their local soil background values. Moreover, the size fractional pollutant contents overall increased as particles' size increased. Averagely, 40-52% pollutant loads were associated with the particles < 250 μm, which can be moved easily by runoff. This study suggests that the behaviors of HDS different from city RDS should be considered as nonpoint source pollution control is performed.

Microzonation, ecological risk and attributes of metals in highway road dust traversing through the Kaziranga National Park, Northeast India: implication for confining metal pollution in the national forest

Despite the abundant literature on metal contamination through road dust (RD) in urban/suburban and residential/highway regions, the RD of highways traversing through the Kaziranga National Park, NE India, has not been studied and lacks baseline data. The objective of the present study was to ascertain the possibility of highway microzonation based on temporal and spatial variability of metal pollution level and ecological risk. It was found that the RD contains an average content of (1.7-33.5 mg/kg) for Cd, Co, Cu and Pb and (121-574 mg/kg) for Ni, Zn, Cr and Mn across the highway passing through the national forest attributed by various sources. The study revealed three possible microzones present in the studied highway NH-37 based on spatial trend of metal as well as human interference. An attempt was made to understand the possible source of metals by principal component analysis, and four sources were identified: Three were of vehicular origin, and another was related to road surface and subsurface condition. The use of noise barrier walls as an effective measure to control the translocation of RD from one place to other was recommended to reduce the hostile effects of metal accumulation in the sensitive ecosystem. Thus, the study suggested and necessitated micronizing the system based on human interference level, ecological risk factors, spatial variability of pollutants and traffic pattern for their efficient management and conservation.

Flow injection online spectrophotometric determination of uranium after preconcentration on XAD-4 resin impregnated with nalidixic acid

In this work, spectrophotometer was used as a detector for the determination of uranium from water, biological, and ore samples with a flow injection system coupled with solid phase extraction. In order to promote the online preconcentration of uranium, a minicolumn packed with XAD-4 resin impregnated with nalidixic acid was utilized. The system operation was based on U(VI) ion retention at pH 6 in the minicolumn at flow rate of 15.2 mL min(-1). The uranium complex was removed from the resin by 0.1 mol dm(-3) HCl at flow rate of 3.2 mL min(-1) and was mixed with arsenazo III solution (0.05 % solution in 0.1 mol dm(-3) HCl, 3.2 mL min(-1)) and driven to flow through cell of spectrophotometer where its absorbance was measured at 651 nm. The influence of chemical (pH and HCl (as eluent and reagent medium) concentration) and flow (sample and eluent flow rate and preconcentration time) parameters that could affect the performance of the system as well as the possible interferents was investigated. At the optimum conditions for 60 s preconcentration time (15.2 mL of sample volume), the method presented a detection limit of 1.1 μg L(-1), a relative standard deviation (RSD) of 0.8 % at 100 μg L(-1), enrichment factor of 30, and a sample throughput of 42 h(-1), whereas for 300 s of the preconcentration time (76 mL of sample volume), a detection limit of 0.22 μg L(-1), a RSD of 1.32 % at 10 μg L(-1), enrichment factor of 150, and a sampling frequency of 11 h(-1) were reported.

On-line separation and preconcentration of lead(II) by solid-phase extraction using activated carbon loaded with xylenol orange and its determination by flame atomic absorption spectrometry

Activated carbon loaded with xylenol orange in a mini-column was used for the highly selective separation and preconcentration of Pb(II) ions. An on-line system for enrichment and the determination of Pb(II) was carried out on flame atomic absorption spectrometry. The conditions of preconcentration and quantitative recovery of Pb(II) from diluted solution, such as pH of aqueous phase, amount of the sorbent, volume of the solutions and flow variables were studied as well as effect of potential interfering ions. Under the optimum conditions, Pb(II) in an aqueous sample was concentrated about 200-fold and the detection limit was 0.4 ng mL(-1) Pb(II). The adsorption capacity of the solid phase was 0.20mg of lead per one gram of the modified activated carbon. The modified activated carbon is stable for several treatments of sample solutions without the need for using any chemical reagent. The recovery of lead(II) from river water, waste water, tap water, and in the following reference materials: SRM 2711 Montana soil and GBW-07605 tea were obtained in the range of 97-104% by the proposed method.