Sea-level rise, as a result of climate change, will likely inflict considerable economic consequences on coastal regions, particularly low-lying island states like Singapore. Although the literature has addressed the vulnerability of developed coastal lands, this is the first economic study to address nonmarket lands, such as beaches, marshes and mangrove estuaries. This travel cost and contingent valuation study reveals that consumers in Singapore attach considerable value to beaches. The contingent valuation study also attached high values to marshes and mangroves but this result was not supported by the travel cost study. Although protecting nonmarket land uses from sea-level rise is expensive, the study shows that at least highly valued resources, such as Singapore's popular beaches, should be protected. 相似文献
Genetic structure was studied in Platygyra sinensis from six sites in Hong Kong by allozyme electrophoresis using an isoelectric focusing gel (IEF). Seven variable loci were detected using six enzyme systems. The number of alleles per locus ranged from 3.3 to 3.6 in the six samples, and heterozygosity from 0.429 to 0.540. Genotype frequencies were generally close to Hardy–Weinberg expectations. The values of unique multilocus genotype to the number of individuals for each sample (NG/N) and observed genotypic diversity to expected genotypic diversity (GO/GE) were high, indicating a high level of sexual reproduction. Variation in allele frequencies among sites was low (FST=0.017), as was Nei's unbiased genetic distance (D), suggesting genetic similarity among sites.Communicated by T. Ikeda, Hakodate 相似文献
Columnar packed-bed (PB) reactors with a specific surface area of 127 m2/m3 were investigated in this study for treating nitrate wastewater. This study demonstrated that a single-stage packed bed was able to achieve total nitrogen (TN) and chemical oxygen demand (COD) removal efficiencies higher than 83 and 75%, respectively. The highest achievable TN and COD removal rates were 47.2 g N/m2 x d and 158.0 g COD/m2 x d, respectively. The substrate removal rate in the PB column was found to follow half-order reaction kinetics, with a reaction coefficient, kappa, of 53.62 (mg/L)1/2/d. A dual-stage PB system was capable of achieving TN and COD removal efficiencies greater than 99 and 98%, respectively. Effluent TN and COD concentrations less than 6.5 mg NO3(-)-N/L and 50.0 mg COD/L, respectively, were obtained when the dual PB system was used. 相似文献
The effects of formaldehyde on biofilm morphology and biomass activity were investigated in an ultracompact biofilm reactor (UCBR) for carbonaceous wastewater treatment. The wastewater contained a fixed amount of glucose (with a chemical oxygen demand concentration of 600 mg/L) and an increasing concentration of formaldehyde (ranging from 21.4 to 271.1 mg/L). An influent formaldehyde concentration higher than 75 mg/L could facilitate filamentous growth (on biofilm) control and lead to a higher biofilm density, which is desirable as it enhanced the UCBR performance stability. However, at an influent formaldehyde concentration higher than 214.4 mg/L, biomass production was inhibited and deteriorations of biofilm morphology and biomass activity were observed. This study showed that it was desirable to maintain an influent formaldehyde concentration lower than 202.2 mg/L, as this concentration could achieve a good biofilm morphology while not inhibiting its microbial activity. 相似文献
Climate change issues are calling for advanced methods to produce materials and fuels in a carbon–neutral and circular way. For instance, biomass pyrolysis has been intensely investigated during the last years. Here we review the pyrolysis of algal and lignocellulosic biomass with focus on pyrolysis products and mechanisms, oil upgrading, combining pyrolysis and anaerobic digestion, economy, and life cycle assessment. Products include oil, gas, and biochar. Upgrading techniques comprise hot vapor filtration, solvent addition, emulsification, esterification and transesterification, hydrotreatment, steam reforming, and the use of supercritical fluids. We examined the economic viability in terms of profitability, internal rate of return, return on investment, carbon removal service, product pricing, and net present value. We also reviewed 20 recent studies of life cycle assessment. We found that the pyrolysis method highly influenced product yield, ranging from 9.07 to 40.59% for oil, from 10.1 to 41.25% for biochar, and from 11.93 to 28.16% for syngas. Feedstock type, pyrolytic temperature, heating rate, and reaction retention time were the main factors controlling the distribution of pyrolysis products. Pyrolysis mechanisms include bond breaking, cracking, polymerization and re-polymerization, and fragmentation. Biochar from residual forestry could sequester 2.74 tons of carbon dioxide equivalent per ton biochar when applied to the soil and has thus the potential to remove 0.2–2.75 gigatons of atmospheric carbon dioxide annually. The generation of biochar and bio-oil from the pyrolysis process is estimated to be economically feasible.
In this work, a novel approach is proposed for expressing the risks of process plants consisting of a large number of scenarios, in the form of a risk metrics of leading indicators to prevent potential high profile industry accidents. The methodology includes: 1) risk estimation of a portfolio by CPQRA (or QRA), 2) monetization of the tangible risks with the inclusion of the lost time of production, 3) estimation of the maximum portfolio loss using Value-at-Risk approach, 4) inclusion of intangible risks using FN-curve and, 5) generation of F$-curve of tangible risks. The proposed methodology can particularly help in understanding the stakes at risk by performing the overall cost-benefit analysis, for identifying the most risky scenarios and identifying critical equipments to enable better risk-informed decision making in order to adopt appropriate risk mitigation measures. This work establishes the groundwork for developing measures for understanding and comparing the large number of risk values derived from QRA studies for large portfolios. It will aid in less subjective decision making as it enables the decision maker to choose the most preferred portfolio option among alternatives. Decisions made with the accurate understanding of the consequences of risks can significantly reduce potential work-related fatalities, property losses and save millions of dollars. 相似文献