天然水体中酚的降解动力学

本文报道了天然水体中低浓度酚的降解动力学;计算了它的降解速率常数、降解活化能等。降解半表期是t_(1/2)=1.5d~(-1)(10℃),t_(1/2)=O.74d~(-1)(30℃)。低浓度酚的降解动力学跟天然水体中酚的降解情况比较接近。本文的结果对环境评价、蓄水库工程设计等很有参考价值。     

Assessing degradation capability of aerobic indigenous microflora in PAH-contaminated brackish sediments

A study was conducted to determine polycyclic aromatic hydrocarbons (PAHs) distribution and microbial population changes in brackish sediments from an Italian lagoon included in the Ramsar List of Wetlands of International Importance. The presence and level of PAH-degrading bacteria were estimated by the most probable number (MPN) enumeration technique, whereas degradation capability towards target compounds was checked against loss of spiked PAHs (Phenanthrene, Anthracene and Fluoranthene) in MPN tubes after incubation in optimal conditions. Chemical analyses and microbiological counts suggested a potential for PAHs biodegradation by natural occurring populations of sediment microorganisms, thus indicating an "optimal range" in sediment PAHs concentrations, outside of which the natural selection of the indigenous microflora did not occur. The MPN procedure here described, provided an effective and reliable way to simultaneously determine microbial population densities and subsequent confirmation of the biodegradation capability of sediment indigenous microflora when exposed to laboratory and environmental concentrations of PAHs.     

Degradation in Cemented Marine Clay Subjected to Cyclic Compressive Loading

The influence of cyclic loading on the strength and deformation behavior of cemented marine clay has been studied. This marine clay is of recent Pleistocene origin and deposited in a shallow water marine environment. Open pits were dug in sheeted enclosures and from these pits, undisturbed samples were taken for strength testing. A series of standard triaxial shear tests and stress controlled one-way cyclic load tests were conducted at consolidation stress ranges below and above the preconsolidation pressure. For the stress levels below the preconsolidation pressure, the cyclic loading has brought about the collapse of the cementation bond through an increase in strains, and at higher pressure ranges, the soil behaves like typical soft clay. This experiment studied the rate of development of strain and pore water pressure and shows that rate is a function of number of cycles, applied stress, and stress history. In addition, soil degradation during cyclic loading is studied in terms of Degradation Index. Attempt has been made to predict stain, pore water pressure, and degradation index through an empirical model.     

Impact of the tsunami and earthquake of 26th December 2004 on the vital coastal ecosystems of the Andaman and Nicobar Islands assessed using RESOURCESAT AWiFS data

Tsunami waves struck the Indian coast on 26th December 2004 affecting the Andaman and Nicobar group of islands. A quick assessment of the status of the vital coastal ecosystems has been made using pre- and post-tsunami Advance Wide Field Sensor (AWiFS) data of Indian satellite RESOURCESAT with an accuracy of 87–90% and the Kappa ranging from 0.8696 to 0.9053. Among the coastal ecosystems the coral reefs have suffered the maximum with the Nicobar reefs (69% eroded and 29% degraded) bearing the brunt more than the Andaman reefs (54% eroded and 22% degraded). Significant improvement to the condition of the reef damaged due to backwash has been noted. About 41% of the Sentinel reef area has undergone significant improvement. The continuance of the erosion of the southwestern Andaman reefs is due to the impact of recurring earthquakes. The impact on mangroves of both the groups of islands has been due to uprooting as well as inundation of seawater and resulting stagnation. Changes are expected in community structure of mangroves as a result of tsunami.     

Discrimination between climate and human-induced dryland degradation

In this study we present a technique to discriminate between climate or human-induced dryland degradation, based on evaluations of AVHRR NDVI data and rainfall data. Since dryland areas typically have high inter-annual rainfall variations and rainfall has a dominant role in determining vegetation growth, minor biomass trends imposed by human influences are difficult to verify. By performing many linear regression calculations between different periods of accumulated precipitation and the annual NDVI_max, we identify the rainfall period that is best related to the NDVI_max and by this the proportion of biomass triggered by rainfall. Positive or negative deviations in biomass from this relationship, expressed in the residuals, are interpreted as human-induced. We discuss several approaches that use either a temporally fixed NDVI peaking time or an absolute one, a best mean rainfall period for the entire drylands or the best rainfall period for each individual pixel. Advantages and disadvantages of either approach or one of its combinations for discriminating between climate and human-induced degradation are discussed. Depending on the particular land-use either method has advantages. To locate areas with a high likelihood of human-induced degradation we therefore recommend combining results from each approach.     

Centralization in the global avoided deforestation collaboration network

Reducing Emissions from Deforestation and Forest Degradation projects currently cover an area approximately twice the size of Germany and challenge traditional concepts of centralization and decentralization in studies of environmental governance. Emerging from the interactions of a complex network of actors, Reducing Emissions from Deforestation and Forest Degradation demonstrates that transnational governance networks of organizations can become spatially centralized. Using a historical analysis of the development of Reducing Emissions from Deforestation and Forest Degradation, we argue that the evolution of Reducing Emissions from Deforestation and Forest Degradation policy has been directed primarily from donor countries, especially in North America and Europe. Adopting a social network analysis approach, we present findings from a new dataset of collaboration on 276 Reducing Emissions from Deforestation and Degradation, avoided deforestation, and sustainable forest management projects that began some on-the-ground operations between 1989 and June 2012, finding that organizations in donor countries have from the beginning been the central actors in the Reducing Emissions from Deforestation and Forest Degradation network. We conclude that Reducing Emissions from Deforestation and Forest Degradation exhibits spatial centralization within transnational governance architectures despite institutional fragmentation, raising important normative questions about participation in transnational forest governance.     

ON SOME KEY SEDIMENTATION PROBLEMS OF THREE GORGES PROJECT (TGP)

I. INTRODUCTIONThe Three Gorges Project (TGP) being planned is to be located on the Yangtze River at Sandouplug, 44 km upstream of Yichang (Fig. l). A scheme studied in the feasibility stage has the crest ofthe dam placed at 185 m with a maximums height o…     

黄土高原晋陕蒙毗邻地区土地退化遥感分析

本文利用遥感技术通过典型区的分析,对黄土高原土地退化现状及其成因过程进行了深入研究。结果表明,黄土高原地区由于特殊的自然条件,加以长期人类活动影响,土地退化十分严重,并处于不断发展之中,主要表现为水土流失和土地沙化等。     

From pastoralism to tourism: The historical impact of changing land use practices in Namaqualand

We use the concept of ecological revolutions to explain the environmental history of Namaqualand, from the advent of pastoralism 2000 years BP, to colonial settlement in the 18th century and finally to the recent trend of de-agrarianization from the middle of the 20th century. Early traveller's records and census data are used to assess changes in the human population of the region and how this affected wildlife and agricultural practices. Pre-colonial indigenous hunter-gatherer (Bushmen) and pastoralist (Khoekhoen) populations in Namaqualand consisted of probably no more than a few thousand individuals. Over the next three centuries, the general population rose steadily to more than 65,000 people but has fallen in recent years. Wildlife appears not to have been abundant in Namaqualand's pre-colonial landscapes and large springbok ‘treks’ were probably a rare event. The number of domestic livestock in Namaqualand peaked in 1957 largely as a result of an increase in the number of sheep which have fallen steadily since this time. Crop production was absent from Namaqualand's pre-colonial landscapes but increased to cover nearly 30,000 ha in the early 1970s. The area under cultivation has declined by nearly two thirds since this time largely as a result of the large-scale abandonment of wheat farming in marginal environments. We touch on differences between the communal areas and private farms, particularly in terms of their human populations and agricultural impact on the land. Repeat landscape photographs support our main findings which suggest that both rocky, upland habitats and rivers have not been transformed substantially by land use practices in Namaqualand. Instead, sandy pediments have borne the brunt of human impacts in the region. Finally, we highlight the beginning of a new ecological revolution in Namaqualand due to changes in the global and national political economy.     

Modelling the sustainability and productivity of pastoral systems in the communal areas of Namaqualand

We investigated the effects of rainfall and the number of animals on changes in vegetation and on the output of milk and meat from the communal areas of Namaqualand. Previously published short- and long-term models link processes that range from the levels of tissue (in, for example, the mammary gland), to the milk yields of individual animals, to the growth and survival of their young and to long-term changes in plant species populations at the ecosystem level. These models have been used to study how different factors and management strategies affect livestock productivity and vegetation composition on a 20,000 ha rangeland in Namaqualand. First, the inter-relations between rainfall, stocking rate and productivity were studied using the short-term model. This model shows that in addition to total rainfall and stocking rate, the timing of rainfall within a year also influences doe live weight and survival to the end of the year. When the long-term model is run, using recorded rainfall, predictions of small stock numbers agree closely with livestock data recorded over the same 30-year period. One thousand replicates of 100-year runs of the long-term model were then used to study the probable impact of different upper limits to stock numbers on animal performance. Off take (sales and slaughterings) are maximal when stock numbers are limited to 2000 adults. Animal numbers increase marginally as the limit is increased above this level, but the variability between years in numbers increases. Secondly, the long-term model was used to study the long-term effects of the stocking rate strategies on rangeland condition. The model predicts that although these effects are variable, when moderately degraded range is stocked with an upper limit at the recommended level it is unable to recover to less degraded states over 100 years. Thirdly, the model was used to examine the effects of reduction in stock numbers and slaughtering of kids in a drought year on goat numbers during the subsequent 5 years. Finally, the model predicts that a 10% reduction in mean annual rainfall will lead to a 35% reduction in animal numbers over 200 years.