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91.
Tropical deforestation is occurring at an alarming rate, threatening the ecological integrity of protected areas. This makes it vital to regularly assess protected areas to confirm the efficacy of measures that protect that area from clearing. Satellite remote sensing offers a systematic and objective means for detecting and monitoring deforestation. This paper examines a spectral change approach to detect deforestation using pattern decomposition (PD) coefficients from multitemporal Landsat data. Our results show that the PD coefficients for soil and vegetation can be used to detect deforestation using change vector analysis (CVA). CVA analysis demonstrates that deforestation in the Kinabalu area, Sabah, Malaysia has significantly slowed from 1.2% in period 1 (1973 and 1991) to 0.1% in period 2 (1991 and 1996). A comparison of deforestation both inside and outside Kinabalu Park has highlighted the effectiveness of the park in protecting the tropical forest against clearing. However, the park is still facing pressure from the area immediately surrounding the park (the 1km buffer zone) where the deforestation rate has remained unchanged. 相似文献
92.
The interconversion of the stereoisomers contained in technical 1,2,5,6,9,10-hexabromocyclododecane, a major brominated flame retardant increasingly found in the environment and in biota, was investigated at elevated temperatures. The application of pure enantiomers of the three constituents alpha-, beta-, and gamma-HBCD enabled the unambiguous elucidation of the individual isomerisation reactions as well as the quantification of all respective rate constants. At 160 degrees C the rate constants range over two orders of magnitude from 1.50x10(-3) to 1.88x10(-5)mol(%)s(-1). A preliminary mechanistic explanation for the differences of the rate constants which govern the composition of HBCD diastereomers at equilibrium is given. 相似文献
93.
Spectroscopic investigation of magnetite surface for the reduction of hexavalent chromium 总被引:1,自引:0,他引:1
The reduction of Cr(VI) to Cr(III) by magnetite in the presence of added Fe(II) was characterized through batch kinetic experiments and the effect of Fe(II) addition and pH were investigated in this study. The addition of Fe(II) into magnetite suspension improved the reductive capacity of magnetite. Eighty percent of Cr(VI) was reduced by magnetite (6.5 g l(-1)) with Fe(II) (80 mg l(-1)) within 1 h, while 60% of Cr(VI) was removed by magnetite only. However, the extent of improved reductive capacity of magnetite with Fe(II) was less than that predicted by the summation of each reduction capacity of magnetite and Fe(II). The reduction of Cr(VI) in the magnetite suspension with Fe(II) increased with the increase of molar ratio of Fe(II) to Cr(VI) (0.6, 1, 1.5, 2.3) in the range of 0-2.3 and with the decrease of pH in the range of pH 8.0-5.5. The speciation of chromium, iron, and oxygen on the surface of magnetite was investigated by X-ray photoelectron spectroscopy. Cr 2p3/2, Fe 2p3/2, and O 1s peaks were mainly observed at 576.7 and 577.8 eV, at 711.2 eV, and at 530.2 and 531.4 eV, respectively. The results indicates that Cr(III) and Fe(III) were the dominant species on the surface of magnetite after reaction and that the dominant species covered the magnetite surface and formed metal (oxy)hydroxide. 相似文献
94.
This study examines the effect of iron-bearing phyllosilicates on dechlorination rates of chlorinated aliphatic hydrocarbons (CAHs) in iron-based degradative solidification/stabilization (DS/S-Fe(II)). Laboratory batch experiments were conducted to evaluate dechlorination rates of 1,1,1-trichloroethane (1,1,1-TCA) in a mixture solution of Fe(II), cement and three different iron-bearing phyllosilicates (biotite, vermiculite, and montmorillonite). A first-order rate model was generally used to describe the dechlorination kinetics and the rate constants were dependent on soil mineral type (biotite, vermiculite, and montmorillonite), Fe(II) dose, and the mass ratio of cement to soil mineral. The pseudo-first-order rate constant for montmorillonite was lower than that for biotite and vermiculite by factors of 11-27 when the mass ratio of cement to phyllosilicates was fixed at one. The presence of biotite and vermiculite increase and the presence of montmorillonite decrease the degradation rate that would be observed in their absence. The effect of cement/mineral ratio on rate constants with three different soil minerals indicates that biotite was more reactive than the other two phyllosilicates. This may be due to high accessible natural Fe(II) content in biotite. Montmorillonite appears to inhibit dechlorination by either inactivating Fe(II) by ion exchange or by physically blocking active sites on cement hydration products. 相似文献
95.
Performance of an immobilized cell biofilter for ammonia removal from contaminated air stream 总被引:3,自引:0,他引:3
The performance of a lab scale biofilter packed with biomedia, encapsulated by sodium alginate and polyvinyl alcohol was used for treating ammonia (NH(3)) gas at different loading rates. The metabolic end products during NH(3) oxidation were NH(4)(+), NO(3)(-) and NO(2)(-). It is noteworthy to mention that the immobilized cell biofilter required no separate acclimatization period and showed high removal efficiencies during the start of continuous experiments. The removal efficiency was nearly 100% when ammonia loading was 4.5gm(-3)h(-1) and the maximum elimination capacity achieved in this study was 5.5gNH(3)m(-3)h(-1) at a loading rate of 7.5gm(-3)h(-1). Shock loading studies were carried out to ascertain the response of the immobilized cells to fluctuations in inlet concentration and flow rate. The inlet loading rates were varied between 0.05 and 6gNH(3)m(-3)h(-1) during this phase of operation. The biofilter responded effectively to these shock loading conditions and recovered rapidly within 4-8h. Pressure drop values were consistently less and insignificant. The results from this study indicated that this immobilized cell biofilter could be considered as a potential option to treat NH(3) under steady and transient state operation. 相似文献
96.
Using a time-varying stochastic frontier model, this paper examines the technical efficiency of firms in the iron and steel industry to try to identify the factors contributing to the industry's efficiency growth. Industry observers and policymakers tend to cite most frequently three possible sources of efficiency growth: privatization; economies of scale; and vintage of equipment. Our study corroborates these factors. Based on our findings, which pertain to 52 iron and steel firms over the period of 1978–1997, privatization is likely to improve the efficiency of iron and steel firms to a great extent as evidenced in various industries. This study also provides systematic evidence that iron and steel production shows economies of scale. In addition, newer vintages of equipment are found to be closely correlated with higher levels of efficiency. This clearly indicates that investment in new plants and equipments is critical in pursuit of efficiency in the iron and steel industry. 相似文献
97.
98.
99.
Jung MC 《Environmental geochemistry and health》2008,30(3):205-217
The objective of this study was to investigate heavy metal contamination and geochemical characteristics of mine wastes, including
tailings, from 38 abandoned mines classified as five mineralization types. Mine waste materials including tailings and soils
were sampled from the mines and the physical and chemical characteristics of the samples were analyzed. The particle size
of tailings was in the range of 10–100 μm. The pH of the waste covered a wide range, from 1.73 to 8.11, and was influenced
by associated minerals and elevated levels of Cd, Cu, Pb, and Zn, extracted by a Korean Standard Method (digestion with 0.1 mol L−1 HCl), which were found in the wastes. Half of the samples contained heavy metals at levels above those stipulated by the
Soil Environmental Conservation Act (SECA) in Korea. In addition, extremely high concentrations of the metals were also found
in mine wastes extracted by aqua regia, especially those from mines associated with sulfide minerals. Thus, it can be expected
that trace elements in mine wastes may be dispersed both downstream and downslope through water and wind. Eventually they
may pose a potential health risk to residents in the vicinity of the mine. It is necessary to control mine wastes by using
a proper method for their reclamation, such as neutralization of the mine wastes using a fine-grained limestone. 相似文献
100.
Human health risk assessment of explosives and heavy metals at a military gunnery range 总被引:1,自引:0,他引:1
In this research, a risk assessment was undertaken in order to develop the remediation and management strategy of a contaminated
gunnery site, where a nearby flood controlling reservoir is under construction. Six chemicals, including explosives and heavy
metals, posing potential risk to environmental and human health, were targeted in this study. A site-specific conceptual site
model was constructed, based on effective, reasonable exposure pathways, to avoid any overestimation of the risk. Also, conservative
default values were adapted to prevent underestimation of the risk when site-specific values were not available. The risks
posed by the six contaminants were calculated using the API’s Decision Support System for Exposure and Risk Assessment, with
several assumptions. In the crater-formed-area (Ac), the non-carcinogenic risks (i.e., HI values) of tri-nitro-toluene (TNT)
and Cd were slightly larger than 1, but for RDX (Royal Demolition Explosives) was over 50. The total non-carcinogenic risk
of the whole gunnery range was calculated to be 62.5, which was a significantly high value. The carcinogenicity of Cd was
estimated to be about 10−3, while that for Pb was about 5 × 10−4, which greatly exceeded the generally acceptable carcinogenic risk level of 10−4–10−6. It was concluded from the risk assessment that there is an immediate need for remediation of both carcinogens and non-carcinogens
before construction of the reservoir. However, for a more accurate risk assessment, further specific estimations of the changes
in environmental conditions due to the construction of the reservoir will be required; and more over, the effects of the pollutants
to the ecosystem will also need to be evaluated. 相似文献