The adsorption of contaminants onto soil particles typically is nonlinear if the contaminant concentration is sufficiently high. A simplified piecewise linear adsorption isotherm consistent with experimental results is proposed as an approximation for nonlinear adsorption behavior. This approximation allows for the use of analytical solution to model solute diffusion of contaminants that exhibit nonlinear adsorption. A moving boundary is introduced to represent significant changes in the retardation factor of clay with an increase in solute concentration. The proposed analytical solutions were validated using experimental data presented in the literature. There is negligible difference between the results obtained by the proposed analytical solution and those obtained by the linear model when Cm/C0 reached 0.5. The results also show that the model based on linear adsorption using the initial secant of the Freundlich isotherm leads to significantly lower estimated breakthrough time for the contaminant of interest than that obtained using the proposed model. The earlier breakthrough is due to an under-estimation of the amount of adsorption. The proposed method is relatively simple to apply and can be used for evaluating experimental results and verifying more complex numerical models. 相似文献
The concentration levels of 36 airborne heavy metals and atmospheric radioactivity in total suspended particulate (TSP) samples were measured to investigate the chemical characteristics, potential sources of aerosols, and health risk in Beijing, China, from September 2016 to September 2017. The TSP concentrations varied from 6.93 to 469.18 μg/m3, with a median of 133.97 μg/m3. The order for the mean concentrations of heavy metals, known as hazardous air pollutants (HAPs), was as follows: Mn > Pb > As > Cr > Ni > Se > Cd > Co > Sb > Hg > Be; Non-Designated HAPs Metals: Ca > Fe > Mg > Al > K > Na > Zn > P > Ba > Ti > Cu > Sr > B > Sn > I > V > Rb > Ce > Mo > Cs > Th > Ag > U > Pt. The median concentration of As was higher than China air quality standard (6 ng/m3). The gross α and β concentration levels in aerosols were (1.84?±?1.59) mBg/m3 and (1.15?±?0.85) mBg/m3, respectively. The enrichment factor values of Cu, Ba, B, Ce, Tl, Cs, Pb, As, Cd, Sb, Hg, Fe, Zn, Sn, I, Mo, and Ag were higher than 10, which indicated enriched results from anthropogenic sources. Pb, As, and Cd are considered to originate from multiple sources; fireworks released Ba during China spring festival; Fe, Ce, and Cs may come from stable emissions such as industrial gases. The health risks from anthropogenic metals via inhalation, ingestion, and dermal pathway were estimated on the basis of health quotient as well as the results indicated that children faced the higher risk than adults during the research period. For adults, the health risk posed by heavy metals in atmospheric particles was below the acceptable level.
In a previous study, we found that rice-straw biochar degraded and removed hydrophobic organic contaminants (HOCs) through coupled adsorption-biodegradation. However, few studies have determined whether biochar affects HOC isomer degradation and isomer-selective biodegradation or whether biochar can alter HOC isomer features, resulting in changes to HOC isomer residues in water environments. In this study, the effects of biochar at two dosages (0.001 and 0.01 g) on the biodegradation of ten isomers of a typical xenoestrogen of nonylphenol (NP) were evaluated. The results revealed that there were no effects of biochar on the adsorption of NP isomers. However, biochar addition affected the biodegradation of a specific isomer without altering the features of the NP isomers. The treatment of NP isomers with Pseudoxanthomonas sp. yielded degradation ratios ranging from 60.7 to 100%. At 0.001 g biochar treatment, the degradation of eight NP isomers was enhanced (except for NP194 and NP193a+b) due to their bulky structures. The degradation of the ten NP isomers was inhibited when 0.01 g biochar was added. These findings characterized the effects of biochar on NP isomer contaminants and provided basic information for the application of biochar for the remediation of NP isomer contaminants.
To investigate the feasibility of using black carbon (BC) in the control of hydrophobic organic contaminants (HOCs) in sediment, we added BCs from various sources (rice straw charcoal (RC), fly ash (FC) and soot (SC)) to sediment to create different BC-inclusive sediments and studied the release of pentachlorophenol (PCP) in the sediments under different condition. Different pH values had no obvious effect on the release of PCP in BC-inclusive sediment, but solid/liquid ratio, temperature, salinity and dissolved organic matter (DOM) content had significant influences on the release of PCP in all sediments except the RC-inclusive sediment. Adding 2% RC to sediment resulted in a 90% decrease in PCP release, which was a greater decrease than observed with FC- and SC-inclusive sediments. Therefore, from the standpoint of HOC release, the application of RC is feasible for organic pollution control in the water environment. 相似文献