Dafang Fu

Speciation distribution and mass balance of copper and zinc in urban rain, sediments, and road runoff

Heavy metal pollution in road runoff had caused widespread concern since the last century. However, there are little references on metal speciation in multiple environmental media (e.g., rain, road sediments, and road runoff). Our research targeted the investigation of metal speciation in rain, road sediments, and runoff; the analysis of speciation variation and mass balance of metals among rain, road sediments, and runoff; the selection of main factors by principal component analysis (PCA); and the establishment of equation to evaluate the impact of rain and road sediments to metals in road runoff. Sequential extraction procedure contains five steps for the chemical fractionation of metals. Flame atomic absorption spectrometry (Shimadzu, AA-6800) was used to determine metal speciation concentration, as well as the total and dissolved fractions. The dissolved fractions for both Cu and Zn were dominant in rain. The speciation distribution of Zn was different from that of Cu in road sediments, while speciation distribution of Zn is similar to that of Cu in runoff. The bound to carbonates for both Cu and Zn in road sediments were prone to be dissolved by rain. The levels of Cu and Zn in runoff were not obviously influenced by rain, but significantly influenced by road sediments. The masses for both Cu and Zn among rain, road sediments, and road runoff approximately meet the mass balance equation for all rainfall patterns. Five principal factors were selected for metal regression equation based on PCA, including rainfall, average rainfall intensity, antecedent dry periods, total suspended particles, and temperature. The established regression equations could be used to predict the effect of road runoff on receiving environments.

Novel molecularly imprinted polymer prepared by palygorskite as support for selective adsorption of bisphenol A in aqueous solution

AbstractNovel strategy to synthesize palygorskite-supported surface molecularly imprinted polymer (SMIP) for bisphenol A (BPA) template was presented. Fourier transform infrared, scanning electron microscopy, and elemental analysis were employed for the characterization of the resulting composites. When compared with the molecularly imprinted polymer, the SMIP exhibited more excellent affinity and selectivity towards BPA in aqueous solution, with the affinity constant (b) of 1.929, the Freundlich constants (KF) of 25.758, and the distribution coefficient (Kd) of 128.390. The adsorption behaviors of the SMIP were well described by Freundlich isotherm model and the pseudo-second-order model. Moreover, the sustainable reusability of the SMIP without significant loss in rebinding capacity was affirmed in four repeated cycles. These results demonstrated the potential of the prepared SMIP as an advanced separation materials for the elimination of specific endocrine disruptor in aquatic environment.

A novel method for measuring polymer–water partition coefficients

Low density polyethylene (LDPE) often is used as the sorbent material in passive sampling devices to estimate the average temporal chemical concentration in water bodies or sediment pore water. To calculate water phase chemical concentrations from LDPE concentrations accurately, it is necessary to know the LDPE-water partition coefficients (KPE-w) of the chemicals of interest. However, even moderately hydrophobic chemicals have large KPE-w values, making direct measurement experimentally difficult. In this study we evaluated a simple three phase system from which KPE-w can be determined easily and accurately. In the method, chemical equilibrium distribution between LDPE and a surfactant micelle pseudo-phase is measured, with the ratio of these concentrations equal to the LDPE-micelle partition coefficient (KPE-mic). By employing sufficient mass of polymer and surfactant (Brij 30), the mass of chemical in the water phase remains negligible, albeit in equilibrium. In parallel, the micelle-water partition coefficient (Kmic-w) is determined experimentally. KPE-w is the product of KPE-mic and Kmic-w. The method was applied to measure values of KPE-w for 17 polycyclic aromatic hydrocarbons, 37 polychlorinated biphenyls, and 9 polybrominated diphenylethers. These values were compared to literature values. Mass fraction-based chemical activity coefficients (γ) were determined in each phase and showed that for each chemical, the micelles and LDPE had nearly identical affinity.

Enhanced Nitrogen Removal by Rice Husk Amended Dynamic Membrane Bioreactors

AbstractEffective and low-cost dynamic membrane bioreactors (DMBR) can be a strong option for wastewater treatment in developing countries. The goal of this study was to investigate the effect of rice husk addition on the DMBR’s nitrogen removal performance. Tests were performed at both lab-scale and pilot-scale facilities. Results showed that rice husk served as a suitable biofilm carrier as well as an effective denitrification carbon source. In lab-scale experiments, the removal efficiency of rice husk amended DMBR for chemical oxygen demand (COD), NH3-N, and total nitrogen (TN) was 96.7, 96.3, and 80.4%, respectively. Results from the pilot-scale DMBR system showed that removal efficiency for COD and NH3-N was 90.3 and 95.2%, respectively, whereas TN removal was comparatively lower (50.5%). Fluorescence in situ hybridization (FISH) analysis showed that the bacterial population was higher in the rice husk added DMBR than the controlled DMBR, and ammonia-oxidizing bacteria were the main components of tot...

Modeling of gas generation from the river adjacent to the manufactured gas plant

Ebullition of gas bubbles through sediment can enhance the migration of gases through the subsurface and potentially affect the emission of important greenhouse gases to the atmosphere. To better understand the parameters controlling ebullition, investigations of gas ebullition in the Grand Calumet river (Indiana, USA) were conducted. We found that gas ebullition might shift and change with different vertical hydraulic gradients and temperatures. CO2 and CH4 flux for each site increased with an increase in temperature. A comparatively simple linear relationship existed between the gas flux and the measured parameters (GF = 0.316T + 300.66i, R2 = 0.82). The gas flux in the sand cap was more variable than that in sediment. Moreover, the total field gas fluxes varied from 10 to 180 mmol m−2 d−1 for sediment and from 5 to 35 mmol m−2 d−1 for the sand cap, which proved an in situ sand cap could provide effective remediation. The analysis presented here has shown that gas fluxes and reactive transport modeling can provide effective means of investigating ebullition and quantifying gas transport.

Pollutant removal efficiency of mesocosm HSSF-constructed wetlands treating highway runoff with different filter materials and HRT

AbstractIn this study, cobble-stone (CS) and broke-stone materials were used as filter media in horizontal sub-surface flow constructed wetlands (HSSF-CWs) for highway runoff treatment. These wetlands were planted with Phragmites spp. plants. The Lukou viaduct section of the Nanjing airport expressway was selected for collection of highway runoff. The HSSF-CWs were subjected to two hydraulic retention times (HRT) of 12 and 24 h with different hydraulic loads and influent flow rate. Based on the results, the CW with broken-stone (BS) substrate achieved significantly higher removal efficiency for SS (75 and 55%), chemical oxygen demand (45 and 50%), NH3-N (78 and 88%), and total phosphorus (77 and 34%) in 12 and 24 h HRT compared with CS substrate wetlands. The CW with CS substrate showed lower removal efficiencies than the BS substrate wetland. The removal efficiencies for Cu, Zn, and Pb for the 12 h HRT were 62, 80, and 9%, respectively, and the concentrations of Cu, Zn, Pb, and Cr were generally under th...

Investigation on the carbon sequestration capacity of vegetation along a heavy traffic load expressway

Carbon sequestration by vegetation plays an important role in the global carbon cycle. More emphasis on the carbon sequestration of roadside vegetation will help to reduce the total carbon emissions from the transportation sector. In the current study, the Shanghai-Nanjing G42 expressway in east China was selected to investigate and calculate the carbon sequestration of roadside vegetation including trees, shrubs and herbs. Findings of the current study revealed that the total carbon sequestration of all the vegetation was about 97,000 tons per year. Results also indicated that trees have a higher carbon sequestration capacity (γ) in unit land area compared to shrubs and herbs. The γ value of most of the shrubs was lower than that of tree; however, species such as Nerium indicum, Jasminum mesnyi and Forsythia suspense have better carbon sequestration capacity than some other tree species. The γ value of herbs was too low, compared with trees and shrubs. The findings of the current study will be of great benefit to make the vegetation planting strategy for express highways in the areas with similar geographic characteristics and climate.

Sediment in-situ bioremediation by immobilized microbial activated beads: Pilot-scale study

A field study was carried out to investigate the sediment in-situ bioremediation by adding microbial activated beads. In this work, Calcium carbonate, silicon dioxide, activated carbon powder, attapulgite powder, sodium alginate, microbial liquid and polyvinyl alcohol were utilized to make the immobilized microbial activated beads. Field experiment results showed that the removal rate of NH4+-N, TN and COD in overlying water reached about 61.8%, 87.5% and 87.1%, respectively. The initial concentration of NH4+-N, TN and COD was 159 mg/L, 6.24 mg/L and 7.28 mg/L, whereas and the final concentration was 58 mg/L, 0.78 mg/L and 0.94 mg/L when water temperature, DO, pH and C/N ratio were 25-30 °C, 2-3 mg/L, 7.0-8.0 and 10-15, respectively. Moreover, under optimal temperature condition (25-30 °C), the removal rate of TOC, TN, heterotrophic bacteria and sulfur bacteria in the river sediment reached to 46.5%, 50.7%, 39.2% and 73.2%, respectively.

The research on the deactivation mechanism of TiO2 nanotube

AbstractTo explore the deactivation mechanism of TiO2 nanotube, freshly prepared and deactivated TiO2 nanotubes were characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The morphologies, the element speciation, and content of the two TiO2 nanotubes were comparatively studied. The results indicated that the two TiO2 nanotubes were different in morphologies. For the deactivated TiO2, the upper end of the nanotubes turned thinner and porous. There was also great difference in element speciation, content and some functional groups on the surface of the two types of TiO2 nanotubes. In the deactivated TiO2 nanotubes, the lattice oxygen (Ti–O) was consumed heavily, which could provide oxygen and let down hole-electron recombination during the catalysis reaction, and the titanium was lost partially, whereas the contents of some carbon/nitrogen functional groups (C–O, C=O, COOR, O–Ti–N) and oxygen species (O–, ) increased. It showed that the effective constituent of TiO2...

Column studies to determine mercury settling in road runoff

A study was performed using a settling column to remove mercury (Hg) from road runoff. The emphasis was placed on the relationship between Hg removal and critical settling velocities, as well as the distribution of total suspended solids (TSS). The impact of rainfall characteristics and temperature on Hg removal was also discussed. Results indicated that Hg removal was significant within the initial 30 min of the settling process. The Hg removal rate increased with the decrease of critical settling velocity, and this trend became gradually significant, which could be used as an important reference for the optimization of sedimentation basin design. Hg removal at different settling times was significantly related to initial distribution of TSS. The impact of rainfall intensity on Hg removal was greater than other parameters of precipitation features, followed by rainfall. In addition, Hg removal was moderately related to temperature. The effect of antecedent dry periods on Hg removal was restricted by rainfall and rainfall intensity.