DNDC模型在长江三角洲农田生态系统的CH4和N2O排放量估算中的应用

长江三角洲是我国农业发达地区之一,其农业生产所排放的CH₄和N₂O,早已引起了研究者的重视.本研究在分析总结现有的野外观测结果的基础上,验证了估算区域痕量气体排放量的生物地球化学模型DNDC,估算出长江三角洲地区的CH₄和N₂O排放量分别为1.69(1.29～2.09)Tg·a^-1和0.019(0.014～0.024)Tg·a^-1,分别占全国农田CH₄和N₂O排放量的16.7%和6.1%.     

土壤氮素生物地球化学循环的研究现状与进展

氮素的生物地球化学循环不仅影响土壤生产力,还会引起全球环境变化,其过程主要包括氮素矿化、固氮、 氮素硝化和反硝化、铵离子的吸附和释放。文章全面综述了氮素生物地球化学过程研究的现状与进展及其可能存 在的问题。     

海洋碳循环与海洋生态系统动力学

在讨论了目前海洋碳循环研究的现状和存在的问题基础上,分析了海洋生态系统动力学在海洋碳循环中的作用.早期的碳循环研究着重在无机碳循环,随着研究的深入,考虑简单生物地球化学过程甚至带显式生态系统的碳循环模式正在逐步发展.指出了碳循环研究的未来方向,除了要更加准确理解物理过程外,发展带显式生态系统的碳循环模式是一个重要的研究方向.为此,要研究生态系统动力学中的某些关键过程的参数化方法,确定一些重要的参数值.期望今后的模式可更加准确地用于研究海洋生态系统和碳循环对全球变化的响应.     

Modeling the seasonal autochthonous sources of dissolved organic carbon and nitrogen in the upper Chesapeake Bay

In this paper we investigate the seasonal autochthonous sources of dissolved organic carbon (DOC) and nitrogen (DON) in the euphotic zone at a station in the upper Chesapeake Bay using a new mass-based ecosystem model. Important features of the model are: (1) carbon and nitrogen are incorporated by means of a set of fixed and varying C:N ratios; (2) dissolved organic matter (DOM) is separated into labile, semi-labile, and refractory pools for both C and N; (3) the production and consumption of DOM is treated in detail; and (4) seasonal observations of light, temperature, nutrients, and surface layer circulation are used to physically force the model. The model reasonably reproduces the mean observed seasonal concentrations of nutrients, DOM, plankton biomass, and chlorophyll a. The results suggest that estuarine DOM production is intricately tied to the biomass concentration, ratio, and productivity of phytoplankton, zooplankton, viruses, and bacteria. During peak spring productivity phytoplankton exudation and zooplankton sloppy feeding are the most important autochthonous sources of DOM. In the summer when productivity peaks again, autochthonous sources of DOM are more diverse and, in addition to phytoplankton exudation, important ones include viral lysis and the decay of detritus. The potential importance of viral decay as a source of bioavailable DOM from within the bulk DOM pool is also discussed. The results also highlight the importance of some poorly constrained processes and parameters. Some potential improvements and remedies are suggested. Sensitivity studies on selected parameters are also reported and discussed.     

Natural Recovery of Technogenic Landscapes in Open Larch Forests in Northeastern Russia

Studies on the vegetation and soil complexes in areas of the Kolyma River basin disturbed by mining, in the northeast of the Chukchi Peninsula, have been performed to reveal trends in natural restorative processes in posttechnogenic landscapes. Data on the flora, phytomass stock, chemical composition of plants pioneering in the overgrowing of disturbed areas, and physicochemical properties of soils and technogenic eluvia have been obtained. The results have shown that plant cover restoration in disturbed areas depends primarily on the type (genesis) of technogenic substrates, the content of fine earth in the surface layer, and the distance from natural plant complexes that serve as a source of seeds coming to the disturbed area.     

Ecological-biogeochemical role of macrophytes in aquatic ecosystems of urbanized territories (an example of small water bodies of St. Petersburg)

The accumulation of heavy metals (Fe, Mn, Zn, Cu, Cr, Ni, Pb, Cd) and biogenic elements (P, S, K, Ca, Na) in leaves has been studied in macrophytes of different ecological groups growing in small water bodies of St. Petersburg. The ecogeological and biogeochemical role of macrophytes in the water-aquatic plants-bottom sediments system and their contribution to the stability of aquatic ecosystem functioning under conditions of a megalopolis are considered. Prospects for using macrophytes for bioindication and phytoremediation of polluted aquatic ecosystems are discussed.     

A Critical Appraisal of Field Evidence From A Regional Survey for Acid Deposition Effects On Scottish Moorland Podzols

Samples have been collected from major horizons of 34 podzol profiles distributed throughout Scotland, all developed from granite or granitic tills and under Calluna moorland. the pH in water and calcium chloride pastes, exchangeable cations and cation exchange capacity, and extractable aluminium of the soils collected have been measured, and the results studied in relation to reported atmospheric deposition of H⁺, non-marine sulphur and nitrate. for all horizons, significant positive correlations were found between soil pH and rainfall mean pH, as might be expected when the critical load of H⁺ deposition is exceeded. Acidifying pollutant deposition also apparently increased soil extractable aluminium concentrations in the B and C horizons. However, exchangeable base cation concentrations tended to increase, rather than decrease, with increasing precipitation acidity. This effect was attributed to increases in biogeochemical cycling of base cations, increases in leaching inputs of base cations from overlying A/E horizon soils, and increases in the inputs of base cations leached from upslope. the results suggest that the simple steady state mass approach to the quantification of critical loads, as often applied, may be an oversimplification.     

Present status of aerosol research in China

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中国农业土壤N_2O排放量估算

采用针对农业土壤痕量气体排放估算开发的、基于N2 O的产生、传输和消耗机理的反硝化分解模型 (DNDC模型 ) ,在建立的有关中国气候、农业土壤和农业生产的分县数据库基础上 ,估计了我国目前农业土壤N2 O的排放量 ,并分析了气候变化和农业耕作措施对全国N2 O排放的影响 .结果表明 ,中国农田土壤的N2 O排放总量为 0 31(0 18— 0 44 )Tg(N)·a - 1,化肥使用量的变化对N2 O排放量的影响最大 .     

Isolation and characterization of ferrous- and sulfur-oxidizing bacteria from Tengchong solfataric region, China

Microbial oxidation and reduction of iron and sulfur are important parts of biogeochemical cycles in acidic environments such as geothermal solfataric regions. Species of Acidithiobacillus and Leptospirillum are the common ferrous-iron and sulfur oxidizers from such environments. This study focused on the Tengchong sofataric region, located in Yunnan Province, Southwest China. Based on cultivation, 9 strains that grow on ferrous-iron and sulfuric compounds were obtained. Analysis of 16S rRNA genes of the 9 strains indicated that they were a liated to Acidithiobacillus, Alicyclobacillus, Sulfobacillus, Leptospirillum and Acidiphilium. Physiological and phylogenetic studies indicated that two strains (TC-34 and TC-71) might represent two novel members of Alicyclobacillus. Strain TC-34 and TC-71 showed 94.8%–97.1% 16S rRNA gene identities to other species of Alicyclobacillus. Di erent from the previously described Alicyclobacillus species, strains TC-34 and TC-71 were mesophilic and their cellular fatty acids do not contain !-cyclic fatty acids. Strain TC-71 was obligately dependent on ferrous-iron for growth. It was concluded that the ferrous-iron oxidizers were diversified and Alicyclobacillus species were proposed to take part in biochemical geocycling of iron in the Tengchong solfataric region.