This study examines the adsorption isotherms, kinetics and mechanisms of Pb2+ sorption onto waste cow bone powder (WCBP) surfaces. The concentrations of Pb2+ in the study range from 10 to 90 mg/L. Although the sorption data follow the Langmuir and Freundlich isotherm, a detailed examination reveals that surface sorption or complexation and co-precipitation are the most important mechanisms, along with possibly ion exchange and solid diffusion also contributing to the overall sorption process. The co-precipitation of Pb2+ with the calcium hydroxyapatite (Ca-HAP) is implied by significant changes in Ca2+ and PO43? concentrations during the metal sorption processes. The Pb2+ sorption onto the WCBP surface by metal complexation with surface functional groups such as ≡ POH. The major metal surface species are likely to be ≡ POPb+. The sorption isotherm results indicated that Pb2+ sorption onto the Langmuir and Freundlich constant qmax and KF is 9.52 and 8.18 mg g?1, respectively. Sorption kinetics results indicated that Pb2+ sorption onto WCBP was pseudo-second-order rate constants K2 was 1.12 g mg?1 h?1. The main mechanism is adsorption or surface complexation (≡POPb+: 61.6%), co-precipitation or ion exchange [Ca3.93 Pb1.07 (PO4)3 (OH): 21.4%] and other precipitation [Pb 50 mg L?1 and natural pH: 17%). Sorption isotherms showed that WCBP has a much higher Pb2+ removal rate in an aqueous solution; the greater capability of WCBP to remove aqueous Pb2+ indicates its potential as another promising way to remediate Pb2+-contaminated media. 相似文献
This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure (XANES) and atomic absorption spectrometry.Total arsenic (As) concentrations in the soil were more than 200 mg/kg.Over four months of laboratory experiments,less than 0.8% As was released into solution after reduction experiments.The 71% to 83% As was chemically reduced into arsenite (As(III)) and partially weathering into the soluble phase.The kinetic dissolution and re-precipitation of As,Fe,Pb and sulfate in this area of paddy soils merits further study. 相似文献
Guangzhou is the capital and largest city(land area:7287 km2)of Guangdong province in South China.The air quality in Guangzhou typically worsens in November due to unfavorable meteorological conditions for pollutant dispersion.During the Guangzhou Asian Games in November 2010,the Guangzhou government carried out a number of emission control measures that significantly improved the air quality.In this paper,we estimated the acute health outcome changes related to the air quality improvement during the 2010 Guangzhou Asian Games using a next-generation,fully-integrated assessment system for air quality and health benefits.This advanced system generates air quality data by fusing model and monitoring data instead of using monitoring data alone,which provides more reliable results.The air quality estimates retain the spatial distribution of model results while calibrating the value with observations.The results show that the mean PM_2.5concentration in November 2010 decreased by 3.5μg/m~3 compared to that in 2009 due to the emission control measures.From the analysis,we estimate that the air quality improvement avoided 106 premature deaths,1869 cases of hospital admission,and 20,026 cases of outpatient visits.The overall cost benefit of the improved air quality is estimated to be 165 million CNY,with the avoided premature death contributing 90%of this figure.The research demonstrates that Ben MAP-CE is capable of assessing the health and cost benefits of air pollution control for sound policy making. 相似文献
An initial reclamation of the Young Dong coal mine site, located in northeastern South Korea, was completed in 1995. Despite the filling of the adit with limestone, acid rock drainage (ARD) enters Young Dong tributary and is then discharged to Imgok Creek. This ARD carries an average of 500 mg CaCO3/l of mineral acidity, primarily as Fe(II) and Al. Before spring runoff, the flow of Imgok Creek is 3.3–4 times greater than that of the tributary and has an alkalinity of 100 mg CaCO3/l, which is sufficient to eliminate the mineral acidity and raise the pH to about 6.5. From April through September 2008, there were at least two periods of high surface flow that affects the flow of ARD from the adit. Flow of ARD reaches 2.8 m3/min during spring runoff. This raised the concentrations of Fe and Al in the confluence with Imgok Creek. However, by 2 km downstream the pH of the Imgok Creek is 6.5 and only dissolved Fe is above the Korean drinking water criteria (0.30 mg/l). This suggests only a minor impact of Young Dong Creek water on Imgok Creek. Acid digestion of the sediments in Imgok Creek and Young Dong Tributary reveals considerable abundances of heavy metals, which could have a long-term impact on water quality. However, several water-based leaching tests, which better simulate the bioavailable metals pool, released only Al, Fe, Mn, and Zn at concentrations exceeding the criteria for drinking water or aquatic life.
An anoxic biofilm involved in continuous denitrificationprocess was monitored to investigate the effect of differentconcentrations of influent dissolved oxygen (DO) or nitrite onthe biofilm. Microelectrode measurements evidenced nitrateremoval activity of biofilm. When different concentrations ofDO were applied to the reactor, generally decreasedconcentrations of DO were observed as bed depth increased fromthe bottom of the reactor. Greatest decrease of the DO wasobserved in the lower 20% of the bed depth. Nitrate removalefficiency was inversely proportional to influent DOconcentrations (8.3-11.9 DO mg L-1) or nitrite loadingrates (0-5.5 N-NO2- kg m-3 day-1) employed in this study. Nitrite loading rates to achieve morethan 90% of nitrate removal efficiency were 1.46 N-NO2-kg m-3 day-1 or less at pH 7.5 and 0.34 N-NO2- kg m-3 day-1 or less at pH 6.8. Nitrate removal efficiency was 63% or more within the lower 20% of the bed depth at the nitrite loading rates that allowed more than 90% of nitrate removal efficiency of the reactor. The results of this study provide first quantitative data that nitrate removalperformance of an anoxic biofilm is inhibited by DO or nitrite,reported to be a limiting factor in the suspended biologicaldenitrification process. 相似文献
The activities of two families of nitrifying bacteria weremeasured by applied respirometer and fluorescence insitu hybridization (FISH) for the purpose of monitoring nitrogenremoval. Oxygen uptake rates (OUR) for Nitrosomonas andNitrobacter were separately measured with the dosing ofselective inhibitors during respirometric monitoring. The FISHmethod was applied to analyze microorganism communities. In 5mg NH4+-N/L solution, the total nitrogen oxygendemand (NOD) was found to be 6,672 mg DO/L-day with ammoniaand nitrite oxidation rate of 4,512 and 2,160 mg DO/L-day,respectively. The oxygen consumption by endogenous oxidationwas 288 mg DO/L-day and the biological oxygen demand 936 mgDO/L-day. Respirometric measurements were well matched by theFISH result, which described the presence and quantity of eachnitrifying bacteria as nitrification proceeded. It was foundthat when coupled with OUR data, FISH could provide valuableinformation about the nitrogen removal process in manypractical wastewater treatment systems. 相似文献
This study examined the relationship between environmental concern and ratings of acceptability of environmental impacts among visitors at two national park settings. Based on the concept of a social ecological paradigm shift, it was hypothesized that individuals with greater levels of environmental concern are less accepting of environmental impacts in national parks than individuals with lesser degrees of concern. Sample data came from Cape Lookout National Seashore (N=392) and Moores Creek National Battlefield (N=236), two national park units in the south-eastern U.S.A. Environmental concern was measured by the New Ecological Paradigm scale. Acceptability was measured by visitor responses to 25 items covering different types of environmental park impacts. Analysis of variance and Tukey's means comparison procedure were used to test for differences between groups defined by levels of environmental concern on impact acceptability. Significant relationships were found between environmental concern and 15 of the 25 specific impacts in the Cape Lookout sample and 13 significant relationships were found in the Moores Creek sample. However, the relationships between environmental concern and acceptability varied somewhat across the two samples. These findings suggested that individuals with greater environmental concern were less accepting (or tolerant) of certain types of park impacts, while individuals with lesser degrees of environmental concern were more accepting of certain park impacts. Differences across the study settings were attributed to the different orientations of park visitors between the two national park units and recency effects. While the data reported are preliminary, they should be informative for park management purposes, particularly in the determination of standards for park impacts. 相似文献