土地渗滤系统对造纸废水深度处理的研究

采用土地快速渗滤深度处理造纸废水,模拟土柱经10个掩埋期的生化培养,经过土地渗滤系统处理,CODcr去除率达90%左右,BOD5可达95%以上,出水达到造纸废水排放标准。     

Dynamics in input and output coefficients for land use studies: a case study for nitrogen in crop rotations

Increasingly, model-based approaches play a role in the design and development of new land use systems. Simulation modeling may play a role in the generation of land use systems for land units, and optimization modeling (e.g. linear programming – LP) may be used in the upscaling to farm and region. In the quantification of new land use systems for land units, often equilibrium conditions with respect to soil resources are assumed, following a so-called target-oriented approach. This facilitates ex ante computation of inputs and emissions of nutrients and allows their use in static optimization models based on LP. The condition of equilibrium in soil resources is often not met, nor is it the ultimate aim. Hence, the dynamics in new systems are insufficiently dealt with. This paper presents an approach for the design of land use systems (crop rotations) and their quantification in terms of input and output coefficients, using particular yields and dynamics in soil resources as targets. Interactions between N input and output of succeeding crops are explicitly taken into account. A simple N-balance model is used describing major processes affecting soil N-dynamics. For the Koutiala region in Mali five crop rotations are evaluated that differ in target crop yield, crop choice, crop residue management and external N source. Modeled crop rotations aiming at high yields, in combination with incorporation of crop residues and legumes, result in depletion of soil N stock. Only in crop rotations aiming at high yields and with incorporation of crop residues combined with a supply of large quantities of animal manure, soil N depletion can be prevented. Four approaches are presented of how to use the dynamic input–output coefficients of these systems in land use studies using LP: (i) use of average coefficients, (ii) use of discounted coefficients, (iii) use of pessimistic estimates of coefficients in an optimization of the land use allocation followed by a recalculation of the objective values for the optimized land use with optimistic coefficients, and (iv) a combined use of systems characteristics, i.e. cumulative N-inputs of land use systems over the time horizon and the magnitude of the soil N pool at the end of the time horizon, which can be used as filters for land use systems. Though none of the approaches completely captures the dynamics in input–output coefficients, they enable a well-founded consideration of the consequences of dynamics in, for instance, soil N stocks in static optimization approaches for farm and regional studies.     

Spatial and temporal variability in excessive soil phosphorus levels in eastern North Carolina

Numerous studies have shown that accumulation of excessive soil phosphorus raises the potential for phosphorus export and eutrophication of adjacent surface waters. Soil phosphorus data from the North Carolina Agronomy Division's database were analyzed for two-year periods spanning the decades of the 1980s and 1990s for 39 eastern North Carolina counties. Eastern North Carolina supported extensive row crop agriculture, rapidly growing intensive livestock industries, and a growing human population during these decades. Excessive soil phosphorus levels, defined as having a soil phosphorus index (P-I, based on Mehlich III testing) > 100, occurred in over 40% of almost a million samples reported for the three two-year periods analyzed. Excessive soil P-I levels were most frequent in central eastern North Carolina, declined in the 1980s and rose again in the 1990s. The distribution of row crop area with excessive soil P-I levels was very similar in time and space. Increases in the area harvested for cotton (+635%) and pasture (+523%) with excessive soil P-I levels were particularly large during the 1990s, when crop areas harvested associated with excessive soil P-I levels for other major crops (corn, tobacco, peanuts) declined. Residential and recreational land uses were associated with similarly high frequencies of excessive soil P-I levels, but these land uses were relatively unimportant (<5% area) compared to agricultural land use (~34%) in the region. Recent increases in fertilizer shipments (approximately twofold in the late 1990s) likely reflected increased cotton production. Rapid growth in concentrated animal production (almost twofold increase in total animal units (AU) between 1992 and 2001), with accompanying land application of wastes, accounted for increases in soil P-I values in pasturelands in the 1990s, particularly in central eastern North Carolina, where these activities were concentrated. The potential threat to water quality from export of excessive soil phosphorus is therefore greatest in this region. North Carolina is currently developing a Phosphorus Loss Assessment Tool (PLAT) in an attempt to manage the challenge posed by excessive soil phosphorus levels.     

Long-term impact of chronosequential land use change on soil carbon stocks on a Swedish farm

Agricultural practices and land use significantly influence soil carbon storage. The processes that are affected by land use and management are generally understood, but uncertainties in projections are high. In this paper, we investigate the long-term effects of chronosequential land use change from grassland to cropland and vice versa on soil carbon stock dynamics in four fields on a Swedish farm. Between 1850 and 1920, three of the fields were converted from grassland into cropland, and one was converted back to grassland in 1971. The fourth (control) field is a grassland that has never been ploughed. In 1937, the four fields were sampled at 111 points in a regular grid (25 or 50 m) and the dried soil samples were stored at our Department. In 1971 and 2002, the original grid points were revisited and re-sampled. Land use changes affected the soil C stock significantly. In 1937, carbon stocks were significantly smaller in the arable fields than in the grassland soil. In the field that was converted from arable back to grassland, soil C increased significantly at an average rate of about 0.4 Mg ha⁻¹ year⁻¹. A soil C balance model (ICBM) driven by standard meteorological data and soil carbon input estimated from yield records described soil carbon dynamics reasonably well, although the range of simulated relative changes in C stocks between 1937 and 2002 in the four fields (from −7.4 to +8.8%) was narrower than those measured (from −19.5 to +16.5%). There are only few long-term studies in Northern Europe available for quantifying the effect of land use change on soil carbon stocks and the results presented here are therefore useful for improving predictions of changes in soil carbon driven by land use change.     

灌阳县新街乡土地整治项目土地平整设计

根据灌阳县新街乡土地整治项目的基本情况,介绍了土地平整思路、设计原则及要点,总结经验,指出土地平整中应注意的一些问题,为类似工程的设计提供参考。     

新疆吉木萨尔县基本农田整治项目经济效益分析

结合新疆吉木萨尔县基本农田整治项目区的实际情况,采用盈亏分析法对整治项目进行了经济效益分析,结果:整治后新增耕地12.70 hm~2,项目区的年总纯收入提高465.71万元,静态投资收益率达到37.58%,经济效益较显著。     

Google Earth在水利水电工程建设征地移民中的应用

遥感技术在水利水电工程建设征地移民中得到了广泛的应用.Google Earth软件具有简单、开放、便捷、高效等优势,本文立足水利水电工程征地移民的实际需要,探讨Google Earth在征地移民规划设计工作中直观和动态展示设计成果的应用方法、实践和过程.结合山口岩水利枢纽工程利用Google Earth制作的项目区卫星影像图、库区淹没示意图、水库淹没3d模型图、淹没区飞行动画视频等成果,应用效果良好.     

A bottom-up assessment and review of global bio-energy potentials to 2050

In this article, a model for estimating bioenergy production potentials in 2050, called the Quickscan model, is presented. In addition, a review of existing studies is carried out, using results from the Quickscan model as a starting point. The Quickscan model uses a bottom-up approach and its development is based on an evaluation of data and studies on relevant factors such as population growth, per capita food consumption and the efficiency of food production. Three types of biomass energy sources are included: dedicated bioenergy crops, agricultural and forestry residues and waste, and forest growth. The bioenergy potential in a region is limited by various factors, such as the demand for food, industrial roundwood, traditional woodfuel, and the need to maintain existing forests for the protection of biodiversity. Special attention is given to the technical potential to reduce the area of land needed for food production by increasing the efficiency of food production. Thus, only the surplus area of agricultural land is included as a source for bioenergy crop production. A reference scenario was composed to analyze the demand for food. Four levels of advancement of agricultural technology in the year 2050 were assumed that vary with respect to the efficiency of food production. Results indicated that the application of very efficient agricultural systems combined with the geographic optimization of land use patterns could reduce the area of land needed to cover the global food demand in 2050 by as much as 72% of the present area. A key factor was the area of land suitable for crop production, but that is presently used for permanent grazing. Another key factor is the efficiency of the production of animal products. The bioenergy potential on surplus agricultural land (i.e. land not needed for the production of food and feed) equaled 215–1272 EJ yr⁻¹, depending on the level of advancement of agricultural technology. The bulk of this potential is found in South America and Caribbean (47–221 EJ yr⁻¹), sub-Saharan Africa (31–317 EJ yr⁻¹) and the C.I.S. and Baltic States (45–199 EJ yr⁻¹). Also Oceania and North America had considerable potentials: 20–174 and 38–102 EJ yr⁻¹, respectively. However, realization of these (technical) potentials requires significant increases in the efficiency of food production, whereby the most robust potential is found in the C.I.S. and Baltic States and East Europe. Existing scenario studies indicated that such increases in productivity may be unrealistically high, although these studies generally excluded the impact of large scale bioenergy crop production. The global potential of bioenergy production from agricultural and forestry residues and wastes was calculated to be 76–96 EJ yr⁻¹ in the year 2050. The potential of bioenergy production from surplus forest growth (forest growth not required for the production of industrial roundwood and traditional woodfuel) was calculated to be 74 EJ yr⁻¹ in the year 2050.     

Life cycle assessment of greenhouse gas emissions of feedlot manure management practices: Land application versus gasification

Animal waste is an important source of anthropogenic GHG emissions, and in most cases, manure is managed by land application. Nevertheless, due to the huge amounts of manure produced annually, alternative manure management practices have been proposed, one of which is gasification, aimed to convert manure into clean energy-syngas. Syngas can be utilized to provide energy or power. At the same time, the byproduct of gasification, biochar, can be transported back to fields as a soil amendment. Environmental impacts are crucial in selecting the appropriate manure strategy. Therefore, GHG emissions during manure management systems (land application and gasification) were evaluated and compared by life cycle assessment (LCA) in our study. LCA is a universally accepted tool to determine GHG emissions associated with every stage of a system. Results showed that the net GHG emissions in land application scenario and gasification scenario were 119 and -643 kg CO₂-eq for one tonne of dry feedlot manure, respectively. Moreover, sensitive factors in the gasification scenario were efficiency of the biomass integrated gasification combined cycle (BIGCC) system and energy source of avoided electricity generation. Overall, due to the environmental effects of syngas and biochar, gasification of feedlot manure is a much more promising technique as a way to reduce GHG emissions than is land application.