垃圾填埋场区域氨氮污染地下水的修复方案比选

早期建设的简易生活垃圾填埋场的防渗措施不足,易发生渗漏,造成填埋场周围地下水的氨氮浓度升高。文章针对华中地区某垃圾填埋场区域氨氮污染地下水,提出抽取处理加异位生物修复、空气注入加原位生物修复两种修复方案,并采用AHP-TOPSIS(层次分析法-逼近理想排序)方法进行方案的比选。在建立合适的比选指标体系基础上,采用AHP-TOPSIS方法进行综合比选研究。结果表明,空气注入+原位生物修复技术更适合于该区域地下水的修复。TOPSIS方法由于缺乏确定评价指标权重的过程,在层次多元分析中的应用受到限制,而AHP是多层次多因素权重确定的有效工具,将二者结合起来,先由AHP确定指标权重,再运用TOPSIS对备选地下水修复方案进行排序,从而弥补了二者各自的不足。AHP-TOPSIS方法可作为环境工作者进行场地修复方案比选的有效工具。     

猫跳河流域梯级水库磷的夏季变化特征

调查了我国第一条全流域梯级水电开发的河流——猫跳河中梯级水库对磷的拦截效应。于2007年丰水期7~9月在猫跳河流域采集水库坝前分层水样以及下泄水，分析和测试水样中的总磷和正磷酸盐。结果表明：丰水期猫跳河流域梯级水库内部总磷和可溶性正磷酸盐变化趋势相似，而下泄水的磷含量均大于该水库表层水体的磷含量。在猫跳河流域的梯级水库中，上游水库（红枫湖和百花湖）的磷含量明显高于各下游水库，即猫跳河流域各水库顺水流方向磷含量具有逐渐减少的特征，说明该流域梯级水库开发对于全流域磷具有梯级拦截效应；另一方面，各水库的富营养化指数表明该流域各水库均处于较高的富营养化状态，全流域富营养化状态差别与磷的分布特征相似，表现为顺水流方向减弱的规律。     

Assessment of nitrogen leaching from arable land in large river basins: Part II: regionalisation using fuzzy rule based modelling

This study deals with fuzzy rule based modelling of nitrogen (N)-leaching from arable land. Main purpose is the elaboration of a method, which allows dynamical regionalisation of results from process-based models for large regions and can be efficiently included in metamodels or decision support systems for rapid integrated assessment of water resources. The paper is the second part of a two-part paper. In the first paper the distributed ecohydrological model SWIM had been applied to calculate and analyse nitrogen dynamics in arable soils for a set of representative natural and management conditions in the Saale River basin (Ecol. Model. (in press)). Here, in the second paper the results from those simulation experiments are used to define, train and validate fuzzy rule systems for the estimation of N-leaching. Nine fuzzy rule systems, specific for nine soil classes, were created from the simulation experiments, representing the conditions for the whole Saale River basin. The fuzzy rule systems operate on monthly time steps and consist of 15 rules and seven input variables each, which are compiled from time series of precipitation, percolation and evapotranspiration as well as from information about fertilizer and crop specific nitrogen uptake. Simulated annealing as a non-linear discrete optimisation method is used for automatic rule assessment. Validation of the fuzzy rule systems, carried out by split sampling of 30-year simulation period, shows satisfactory performance on an annual basis and good performance on the long-term basis with average correlation between SWIM-simulated and fuzzy rule-estimated N-leaching values of 0.78 and 0.94, respectively.     

Integrated and comprehensive estimation of greenhouse gas emissions from land systems

Exchanges of carbon and nitrogen between the atmosphere and terrestrial ecosystems involve a complex set of interactions affected by both natural and management processes. Understanding these processes is important for managing ecosystem productivity and sustainability. Management processes also affect the net outcome of exchanges of greenhouse gases between terrestrial ecosystems and the atmosphere. In developing a national carbon accounting system (NCAS) for Australia to account for emissions and removal of greenhouse gases to and from the atmosphere, a carbon:nitrogen mass balance ecosystem model (FullCAM) was developed. The FullCAM model is a hybrid of empirical and process modelling. The approach enables application to a wide range of natural resource management issues, because it is at land-management-relevant spatial and temporal resolution and captures the main process and management drivers. The scenario-prediction capability can be used to determine the emissions consequences of different management activities. Because, in Australia, emissions of greenhouse gases are closely related to the retention of dead organic matter and the availability of nitrogen for plant growth, the carbon and nitrogen cycling as modelled are good indicators of ecosystem productivity and condition. The NCAS also emphasizes the advantages of a comprehensive and integrated approach to developing a continental scale ecosystem-modelling system that has relevance both to estimation of greenhouse gas emissions and sustainable management of natural resources.     

Organic matter composition in sediments of the Oman Margin

The quantity and biochemical composition of organic matter (OM) in the sediments underlying and below oxygen minimum zone (OMZ) in the Arabian Sea were studied to provide information on the diagenetic processes of organic carbon under different environmental conditions. Concentrations of total organic carbon (TOC), total nitrogen (TN) and total hydrolysable amino acids (THAA) were significantly higher in sediments within rather than below OMZ, while those of total carbohydrates (TCHO) were slightly lower in the latter, suggesting the presence of a larger supply of labile compounds into the sea bottom at the shallower site (i.e. within OMZ). Hydrolysable amino acid and carbohydrate contribution to TOC were even lower (about 10% in surficial sediments) than the values obtained from the abyssal oligotrophic North Pacific, suggesting that OM food availability in the Oman Margin sediments within OMZ was lower than that observed at abyssal depths. The presence of the highest THAA and TCHO concentrations in the top 40 mm of the sediment core at both sites reflected the presence of bioturbation processes. In contrast with the general view of the deep sea as a stable and constant system, below OMZ in the Arabian Sea sediments, some differences were observed in the two investigated cores indicating the presence of a certain spatial variability in OM content and diagenesis.     

沈阳市大气氮氧化物污染状况及控制对策

阐述了沈阳市各类污染源排放废气中NOx排放量所占比例、排放特征,分析了环境空气中NOx的污染状况、各功能区环境空气中二氧化氮浓度差异,污染源排放及其分布、气象条件等因素对沈阳NOx污染分布的影响,并提出确定重点控制行业和地区、建立NOx相应的监测、统计、评估体系、修订和完善环境空气质量标准和一批行业NOx排放标准、应用先进的烟气脱硝技术等几方面的NOx控制对策。     

Spatial and temporal variation of below-ground N transfer from a leguminous tree to an associated grass in an agroforestry system

Nitrogen (N) transfer from leguminous trees can be a major N source for the associated crop in low-input agroforestry systems. The aim of this study was to identify the main climatic and soil factors controlling N transfer from the leguminous tree Gliricidia sepium (Jacq.) Walp to the associated grass Dichanthium aristatum (Poir.) C.E. Hubb, in a 16-year-old tropical agroforestry system. Nitrogen transfer was estimated using the natural ¹⁵N abundance method. Before tree pruning, total N transfer represented 57% of the N uptake of the grass, including 31% coming from N₂ fixation. The spatial variation induced by the tree was well described by soil organic N content (ON). In this system, ON is an index of soil available N as well as of tree root density. Rainfall (R) and evapotranspiration (ETP) were the main climatic factors controlling N transfer. Multiple regression analysis indicated that R, ETP and ON explained 79% of the temporal and spatial variation of N transfer. Transferred N cannot be estimated after pruning because of the change in the isotopic signature of the soil N source. This was related to N release from root turnover. The results suggest that grass showed a preferential uptake of N coming from the tree, which could be due to a lower energy cost compared to obtaining absorbed N from the clayey soil used in this work.     

Model evaluation of different mechanisms driving freeze–thaw N2O emissions

N₂O emissions from soil contribute significantly to global warming. Pulse emissions of N₂O from soils during freeze-thawing were recently recognized as important atmospheric sources. In this modelling study we explore three different hypotheses for explaining freeze–thaw related N₂O emissions: (1) soil frost or snow cover may reduce gas diffusion and create anaerobic conditions that stimulate N₂O production via denitrification, (2) microbes that die of frost deliver easy decomposable organic carbon and nitrogen to the soil, which stimulates microbial growth and vigorous N₂O production during freeze–thaw, and (3) the enzyme nitrous oxide reductase, which is responsible for the reduction of N₂O to N₂ during denitrification, is more sensitive to low temperatures than other enzymes, so that N₂O becomes the dominating end-product of denitrification at low temperatures. These hypotheses were tested with a biogeochemical model that combines hydrology and physics calculations with a newly developed, parameter-poor biochemistry module. The model was first calibrated with field datasets on soil–atmosphere fluxes of N₂O, NO and CO₂ and soil NO₃ and NH₄ concentrations that were measured in a spruce forest in Southeast Germany in the years 1994–1997. Subsequently, additional model mechanisms were implemented that allow the model to describe the outlined mechanisms potentially driving freeze–thaw N₂O fluxes. After each implementation the model was recalibrated. We were able to mimic dimension and timing of high N₂O emissions when either one of the first two hypotheses were assumed, but found no confirmation for the third. The best model fit was achieved by combining hypothesis one and two, indicating that freeze–thaw N₂O emissions are not mono-causal.     

氮素在土壤-作物中迁移转化的试验研究

为研究氮素在土壤和作物体系中的运移规律。本文开展土壤箱栽试验,分析农作物玉米在关中盆地3种不同类型土壤中对氮素的吸收以及土壤中氮素的迁移转化规律。结果表明,在试验初期,3种土壤中三氮主要以NH4＋的形式存在,随着农作物生长NH4＋含量减少,同时NO2-和NO3-含量均有不同程度的累积。作物收获后,土壤和作物体系中有相当数量的氮素残留,而且土壤中氮残留相对较高,导致氮素的损失率较大,流失的N素必将会对土壤、甚至地下水产生污染,因此建议该地区针对不同的土壤类型控制氮肥施用量,合理施用氮肥。     

Controls over soil microbial biomass responses to carbon amendments in agricultural systems: A meta-analysis

Soil microbial biomass (MB) facilitates key ecosystem functions such as soil aggregation and nutrient cycling and makes a substantial contribution to soil organic matter. While agricultural conversion drastically reduces MB, the use of organic amendments is an effective way to rebuild depleted MB. Yet, little is known about broad-scale, global controls over MB responses to organic inputs. We used a meta-analysis to identify the degree to which soil properties, agricultural management, and geographic location regulate MB response (carbon, C_mic; nitrogen, N_mic; and C:N ratio, C:N_mic) to animal manure-based inputs relative to inorganic fertilizers. We show that organic amendments increased C_mic by 36% and N_mic by 27% across all observations. The chemistry of amendments and their application rates were the strongest regulators of C_mic but edaphic properties were also important. C:N_mic averaged 8.6 and was not influenced by organic amendments under any conditions, providing evidence that the physiological requirements of microbes, rather than management or environmental factors, constrain their elemental stoichiometry. Our study indicates that even small quantities of organic amendments can be used to rapidly restore MB across a range of cropping systems but specific responses depend upon the type and rate of inputs as well soil characteristics.