As the most desirable option for sustainable development of tourism industry, ecotourism still suffers from lack of a clear-cut and widely accepted definition, posing many risks and threats in its practices. Based on collection and collation of various concepts and explanations of ecotourism both at home and abroad, this paper reflects on the current connotations of ecotourism in terms of four aspects, namely, objects of ecotourism, ecotourists, nature of ecotourism as well as the relationship between ecotourism and communities. In-depth analysis was performed in an effort to revise the misinterpretation of ecotourism and provide implications for ecotourism initiatives. The main conclusions and fruits of this article include: 1) The objects of eeotourism should go beyond natural, pristine, or even only primitive natural areas to including cultural resources together with their natural context which also deserve preservation. 2) Tourism operators, compared to tourists, have more leverage and hence should shoulder more responsibilities for conservation. 3) Ecotourism should serve as a principle to guide tourism initiatives towards sustainability, rather than merely a special tour package. 4) The theoretic foundation was laid for community participation in ecotourism. 相似文献
The farmland irrigation with the sewage is a common and better pathway to save the resource of groundwater in Northern China. The investigation was conducted in the farmland along the Fuhe River to explore characteristics of heavy metals in soils and grains of wheat and maize from a long-term sewage-irrigated area of Baoding region. The results showed that the topsoil with long-term sewage irrigation accumulated more Cd, Pb, and Hg compared with that of soil irrigated with groundwater and their corresponding natural background values. Cd concentrations in 48% of sewage-irrigated soil samples exceeded the Chinese safety limitation at 0.6 mg/kg, but less Cd accumulated in crop grains and did not pose the potential health risk. On the contrary, Pb levels in soils irrigated with sewage were lower than the safety limitation but Pb concentrations in 24% of wheat grain samples exceeded the Chinese national safety limit. Long-term sewage irrigation did not increase As, Cr, and Ni concentrations in soils or crop grains. The target hazard quotient (THQ) of heavy metals in edible grains of crops was selected to assess their risk to human health. Total THQ values were higher than 1.0 for the wheat samples from sewage-irrigated area and both sewage-irrigated and smelter-impacted areas, and As is the main contributor to the total THQ and posed the potential risk to human health. Therefore, the accumulation of Cd, Pb, Hg, and As in soils and crops in sewage-irrigated area should be monitored continuously to ensure food safety and security.
Size–fractioned atmospheric aerosol particles were collected during a typical heavy air pollution event in Beijing. The organic and inorganic components on the surfaces of the samples were analyzed using time–of–flight secondary ion mass spectrometry(TOF–SIMS).The variation characteristics of the surface chemical composition and influencing factors were studied, and the possible sources of these chemical compositions were identified through principal component analysis. The results showed that inorganic components such as crustal elements and sulfate, and organic components such as aliphatic hydrocarbons and oxygen–containing organic groups were present. Some surface components, such as polycyclic aromatic hydrocarbons, heavy metals and fluorides may exert adverse effects on human health. The species and relative percentages of the chemical components varied with particle size, diurnal and pollution progress. During a heavy pollution event, the species and relative percentages of secondary components such as oxygen–containing organic groups and sulfurous compounds increased, indicating that particles aged during this event. The surface chemical composition of the aerosol particles was affected mainly by emissions from coal combustion and motor vehicles. In addition, air pollution, meteorological factors, and air mass transport also exerted a significant effect on the surface chemical composition of aerosol particles. 相似文献