填埋场沼气发电的温室气体减排效益分析

填埋场沼气是垃圾卫生填埋场产生的可利用资源.以深圳下坪垃圾填埋场为例,定量分析垃圾填埋气体发电的温室气体减排效益.结果表明,填埋场沼气发电具有很好的经济效益和环境效益,可作为与发达国家进行CDM(清洁发展机制)项目合作的优先技术领域.     

A methodology for assessing urban sustainability: Aalborg commitments baseline review for Riga, Latvia

Both the Aalborg Commitments and the guidance on integrated urban environmental management and sustainable urban transport plans proposed by the EU Thematic Strategy on the Urban Environment foresee a baseline review as the first step in developing integrated urban management plans and systems. A baseline review of urban sustainability undertaken in Riga reveals significant discrepencies between the sustainability criteria of the Aalborg Commitments and the: responsibilities and competencies of the municipal government and administration as defined by statutes; policy goals and measures defined in municipal planning documents; policy goals and measures defined in the Riga Development Plan. To better orient the mandate of the municipality towards sustainable development, municipal statutes should be supplemented to more fully reflect the issues defined by the Aalborg Commitments and should include sustainability as a goal. In order to strengthen the implementation of sustainable development specific policy goals, measures and targets should be formulated for all the Aalborg Commitments issues when revising existing municipal planning documents or developing a municipal sustainable development management plan. An analysis of the European Common Indicators and the State of the Environment in Riga 2001 indicators indicates that they can only partially fulfill a monitoring function for the implementation of the Aalborg Commitments. This highlights a need to better coordinate sustainable development initiatives at the European level. The methodology used for the baseline review in Riga is useful for assessing the status of urban sustainability when preparing integrated urban management plans or systems, but requires testing elsewhere. Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue.     

Baseline soil levels of PCDD/Fs established prior to the construction of municipal solid waste incinerators in China

In order to determine the baseline contamination by polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in different areas in China, prior to the construction of municipal solid waste incinerators (MSWIs), a total of 32 representative soil samples was collected near 16 incinerators and analyzed for their PCDD/F concentrations. The PCDD/F baseline concentrations in the soil samples ranged from 0.32 to 11.4 ng I-TEQ kg⁻¹ (dry matter), with average and median value of 2.73 and 2.24 ng I-TEQ kg⁻¹ (dry matter), respectively, and a span between maximum and minimum recorded value of 36. The PCDD homologues predominated in 26 out of 32 soil samples, with the ratio (PCDDs)/(PCDFs) ranging from 1.1 to 164; however in the other 6 samples, PCDF homologues were larger, with the same ratio varying from 0.04 to 0.8. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to examine PCDD/F amount and profile in these soil samples, and their possible associations with known emission sources: in this process 6 really distinct isomer fingerprints were identified. Background PCDD/F levels and profiles were comparable to those found in soils from China and other countries and indicate a rather low baseline PCDD/F contamination of soils. The present data provide the tools for future assessment of a possible impact of these MSWIs.     

Assessing health impacts in complex eco-epidemiological settings in the humid tropics: Modular baseline health surveys

The quantitative assessment of health impacts has been identified as a crucial feature for realising the full potential of health impact assessment (HIA). In settings where demographic and health data are notoriously scarce, but there is a broad range of ascertainable ecological, environmental, epidemiological and socioeconomic information, a diverse toolkit of data collection strategies becomes relevant for the mainly small-area impacts of interest. We present a modular, cross-sectional baseline health survey study design, which has been developed for HIA of industrial development projects in the humid tropics. The modular nature of our toolkit allows our methodology to be readily adapted to the prevailing eco-epidemiological characteristics of a given project setting. Central to our design is a broad set of key performance indicators, covering a multiplicity of health outcomes and determinants at different levels and scales. We present experience and key findings from our modular baseline health survey methodology employed in 14 selected sentinel sites within an iron ore mining project in the Republic of Guinea. We argue that our methodology is a generic example of rapid evidence assembly in difficult-to-reach localities, where improvement of the predictive validity of the assessment and establishment of a benchmark for longitudinal monitoring of project impacts and mitigation efforts is needed.     

Application of arsenic baselines in the assessment of soil contamination in Finland

In Finland, a new Government Decree on the Assessment of Soil Contamination and Remediation Needs (214/2007) came into force on 1 June 2007. According to the Decree, natural baseline concentration levels should be taken into account when assessing potential soil contamination and the need for remediation. This applies particularly in the case of toxic metallic elements, since baseline concentrations may naturally be rather high. The new decree prescribes soil screening values for 52 substances or groups of substances. The natural baseline concentrations have been taken into account in the definition of the screening values for inorganic pollutants. The Geological Survey of Finland (GTK) carried out a nation-wide geochemical mapping of till on a reconnaissance scale in 1983 and on a regional scale during 1984–1992. These surveys have provided information on natural elemental distribution in subsoils of the glacial till. However, some important trace elements in regional mapping such as arsenic are missing from the analysis, and subsoil samples do not reflect the diffuse anthropogenic input. Thus, GTK has continued the survey work by determining geochemical baselines around suburban areas. Samples have been taken from humus, topsoil and subsoil layers, and the soil parent material has covered sandy soils, glacial tills and fine-grained sediments. According to the studies, a regional difference in the levels of arsenic and some other trace elements can be clearly seen, especially in minerogenic soils. The results illustrate the importance of information on regional baseline concentrations while assessing potential soil contamination.     

Uncertainties associated with the assessment of vegetation

The Environmental Impact Statement (EIS) attempts to portray the current character of a given ecosystem. This provides a Baseline against which future possible changes can be assessed. Ecosystems, however, are dynamic and in a constant state of change. Consequently, data representing a single year reflect conditions only for that year and can be misleading if compared against any other year. In addition to this temporal variation, considerable spacial variation exists in species composition and cover. Ample sampling is required to compensate for this heterogeneity. Variation, or background noise, can be minimized by the use of similarity indexes and sampling over a period of at least two years.     

Urban geochemical mapping studies: how and why we do them

Geochemical mapping is a technique rooted in mineral exploration but has now found worldwide application in studies of the urban environment. Such studies, involving multidisciplinary teams including geochemists, have to present their results in a way that nongeochemists can comprehend. A legislatively driven demand for urban geochemical data in connection with the need to identify contaminated land and subsequent health risk assessments has given rise to a greater worldwide interest in the urban geochemical environment. Herein, the aims and objectives of some urban studies are reviewed and commonly used terms such as baseline and background are defined. Geochemists need to better consider what is meant by the term urban. Whilst the unique make up of every city precludes a single recommended approach to a geochemical mapping strategy, more should be done to standardise the sampling and analytical methods. How (from a strategic and presentational point of view) and why we do geochemical mapping studies is discussed.

An assessment of metal contamination along the Irish coast using the seaweed Ascophyllum nodosum (Fucales, Phaeophyceae)

The relative abundance and variation of Cr, Co, Cd and Pb in Ascophyllum nodosum and intertidal surface sediments from six locations around the coast were assessed over six seasons. Higher Cd and Pb levels in Galway Docks and Cork Harbour were attributed to localised inputs of these metals from municipal and domestic waste, while at a reference site (Ballyconneely), high algal Cr concentrations were considered a function of geological setting rather than anthropogenic loading. Little seasonal variation was observed, with the exception of higher Co levels in plants in winter, associated with growth dynamics and increased fluvial inputs. In comparison with previously published data for metals in A. nodosum from the North Atlantic, with the exception of localised hot spots, the Irish coastline is still a relatively pristine environment. A. nodosum may be successfully and easily used as a biomonitor of metal contamination in coastal waters.     

Projecting Large-Scale Area Changes in Land Use and Land Cover for Terrestrial Carbon Analyses

One of the largest changes in US forest type areas over the last half-century has involved pine types in the South. The area of planted pine has increased more than 10-fold since 1950, mostly on private lands. Private landowners have responded to market incentives and government programs, including subsidized afforestation on marginal agricultural land. Timber harvest is a crucial disturbance affecting planted pine area, as other forest types are converted to planted pine after harvest. Conversely, however, many harvested pine plantations revert to other forest types, mainly due to passive regeneration behavior on nonindustrial private timberlands. We model land use and land cover changes as a basis for projecting future changes in planted pine area, to aid policy analysts concerned with mitigation activities for global climate change. Projections are prepared in two stages. Projected land use changes include deforestation due to pressures to develop rural land as the human population expands, which is a larger area than that converted from other rural lands (e.g., agriculture) to forestry. In the second stage, transitions among forest types are projected on land allocated to forestry. We consider reforestation, influences of timber harvest, and natural succession and disturbance processes. Baseline projections indicate a net increase of about 5.6 million ha in planted pine area in the South over the next 50 years, with a notable increase in sequestered carbon. Additional opportunities to expand pine plantation area warrant study of landowner behavior to aid in designing more effective incentives for inducing land use and land cover changes to help mitigate climate change and attain other goals.     

Distribution and mobility of mercury in soils of a gold mining region, Cuyuni river basin, Venezuela

An extensive and remote gold mining region located in the East of Venezuela has been studied with the aim of assessing the distribution and mobility of mercury in soil and the level of Hg pollution at artisanal gold mining sites. To do so, soils and pond sediments were sampled at sites not subject to anthropological influence, as well as in areas affected by gold mining activities. Total Hg in regionally distributed soils ranged between 0.02 mg kg(-1) and 0.40 mg kg(-1), with a median value of 0.11 mg kg(-1), which is slightly higher than soil Hg worldwide, possibly indicating long-term atmospheric input or more recent local atmospheric input, in addition to minor lithogenic sources. A reference Hg concentration of 0.33 mg kg(-1) is proposed for the detection of mining affected soils in this region. Critical total Hg concentrations were found in the surrounding soils of pollutant sources, such as milling-amalgamation sites, where soil Hg contents ranged from 0.16 mg kg(-1) to 542 mg kg(-1) with an average of 26.89 mg kg(-1), which also showed high levels of elemental Hg, but quite low soluble+exchangeable Hg fraction (0.02-4.90 mg kg(-1)), suggesting low Hg soil mobility and bioavailability, as confirmed by soil column leaching tests. The vertical distribution of Hg through the soil profiles, as well as variations in soil Hg contents with distance from the pollution source, and Hg in pond mining sediments were also analysed.