Effect of dissolved organic matter on the stability of magnetite nanoparticles under different pH and ionic strength conditions.

Upon release of engineered nanoparticles (NPs) into the subsurface environment, their fate and transport and hence their potential environmental and public health impacts will largely depend on how stable these NPs are as suspended particles in the natural environment. In this study, we systematically examine the effect of humic acid (HA) on surface charge status and aggregation potential of magnetite (Fe(3)O(4)) NPs, selected as a model for metal oxide NPs, over a wide range of solution pH and ionic strength. Through zeta potential (ZP) measurements, we found that HA can adsorb to magnetite particles hence modifying their surface charge status.

[PAH sources in road runoff system in Beijing].

In this study, road runoff, rainwater, ground sediment and roadside tree water samples were collected from three types of roads in Beijing in 2006. The samples were analyzed for polycyclic aromatic hydrocarbons (PAHs). The average PAH concentrations in each media in May-June were generally higher than those in July-August.

Numerical simulation of PAHs sorption/desorption on soil with the influence of Tween80.

In this paper, the influences of inionic surfactant Tween80 on polycyclic aromatic hydrocarbons (PAHs) sorption/desorption on artificially contaminated soil were studied, and gamma model was applied to simulate the influences. Results showed that, with the use of Tween 80, the sorption behaviors of PAHs on soil altered significantly. Adsorbed Tween 80 increased the sorption amount of PAHs while the dissolved Tween80 increased the apparent solubility of PAHs.

[Desorption of polycyclic aromatic hydrocarbons from soil in presence of surfactants].

Four types of surfactant were used to study their effects on polycyclic aromatic hydrocarbons (PAHs) desorption from artificially contaminated and oil-contaminated soil. The results show that the desoption of PAHs from soil is affected by the type and concentration of surfactant and also by the character and state of PAHs. Surfactants don't improve PAHs desorption from soil when their concentrations are below or near their critical micelle concentration (CMC) values.

[Effect of surfactants on biodegradation of PAHs by white-rot fungi].

The impacts of surfactants (Tween80, Trition X-100, LAS and SDS) on PAHs degradation by white-rot fungi in aqueous system and soil-water system were studied. Results show that the type and concentration of surfactants, PAHs statues, pH value of the systems and temperature have impacts on the degradation of PAHs. In aqueous system, all the four surfactants restrained the degradation of PAHs.

[Influences of surfactant on the transport of PAHs in artificially contaminated soil columns].

The effect of anionic surfactant LAS on leaching of PAHs from artificially contaminated soil was studied. The interaction of these processes were studied in a two-layer column experiment with a base layer of uncontaminated soil(9cm) and a top layer of artificially contaminated soil(1cm). Results show that 5 critical micelle concentration (CMC) LAS enhanced the transport of PAHs.