Adding virtual measuring stations to a network for urban air pollution mapping

Maps of pollutants concentration are usually generated by means of interpolation and extrapolation methods. The quality of the results depends mainly of the number of permanent or temporary measuring stations. This paper deals with a method for the virtual densification of the network of stations. The method creates "virtual measuring stations". It aims at improving the quality of interpolation by increasing the number of data on pollutant concentration. The virtual stations are determined by the means of a classification method applied to each pixel of the area under concern. Discriminating elements are pollutants emission classes, land cover types, urban morphological indicators created to this purpose and distance to major roads. A first implementation was made for particulate matter (PM) for the city of Strasbourg (France) using thin-plates spline interpolation method in Arcview 9 GIS. The relative Root Mean Square Error decreases from 49% for five input stations down to 15% for the virtual stations.     

Earthworm assisted bioremediation of organic contaminants

Due to their biological, chemical and physical actions, earthworms can be directly employed within bioremediation strategies to promote biodegradation of organic contaminants. Earthworms have been shown to aerate and bioturbate soils and improve their nutritional status and fertility, which are variables known to limit bioremediation. Earthworms have also been shown to retard the binding of organic contaminants to soils, release previously soil-bound contaminants for subsequent degradation, and promote and disperse organic contaminant degrading microorganisms. This review discusses these earthworm actions upon the soil environment and how they might influence the fate and behaviour of soil associated organic contaminants, subsequently improving bioremediation potential. The latter part of this review considers organic compounds in the following order: agrochemicals, petroleum and crude oil hydrocarbons, PAHs and PCBs.     

The role of plant leaf attributes in linking land use to ecosystem function in temperate grassy vegetation

We tested predictions of the relative changes in plant leaf traits in response to land uses in Australian eucalypt grassy ecosystems. Predictions were determined from responses observed in European landscapes in relation to disturbances associated with agricultural land uses. We measured specific leaf area (SLA) and leaf dry matter content (LDMC) across five land uses: reference sites (closest to pre-European state), native pastures (unfertilized), fertilized pastures, sown pastures (cultivated and fertilized) and enriched grassland (previously fertilized, no longer grazed). Leaves were expected to have higher SLA and lower LMDC at sites with increasing fertility and/or disturbance.The predictions were confirmed, with SLA increasing progressively in land uses associated with (1) grazing; (2) grazing and fertilization; (3) grazing, fertilization and cultivation. Values for LDMC were closely (but inversely) correlated with those of SLA. For both traits, there were relationships with available soil phosphorus but not with soil total nitrogen. The positive correlation of SLA with phosphorus was not evident above 30 mg kg⁻¹, the recommended level of phosphorus for improved pastures.Results confirm patterns of leaf-trait response to disturbance that reflect fundamental constraints to plant survival in habitats with different levels of resources and disturbances. A conservative strategy for low productivity undisturbed habitats is associated with low SLA and high dry matter content in contrast to fertile disturbed habitats which select for high SLA and low dry matter content. The changes in leaf traits across land uses resulted from species substitution rather than variation within species across sites, and most notably the replacement of native by annual exotic species as land use intensifies.Recommended fertilization rates for pasture production convert the ground layer to plants with soft, digestible leaves, that are responsive to fertilizer and desirable for livestock production. However, fertilization also drastically reduces the diversity of native plants and annual plants tend to dominate. The trade-off associated with high production includes increased vulnerability to soil erosion, due to reduced plant cover and low persistence of cover. If alternative ecosystem values such as erosion control, water quality, salinity control and biodiversity persistence are required, incentives may be needed to offset the loss of production that can be gained from fertilizer application.     

Breeding skylarks (Alauda arvensis) on organic and conventional arable farms in The Netherlands

The aim of this study was to analyse the effects of differences in cropping pattern between organic and conventional arable farms on the breeding activity of skylarks and to assess the effects of arable crop management on skylark nest survival. Skylark nest density was seven times higher on organic farms than on conventional farms (0.63 vs. 0.09 nest per 10 ha). Skylarks showed a strong preference for spring cereals, lucerne and grass leys, all of which were mainly or exclusively grown on organic farms. On organic farms nests were initiated during the entire breeding season, but on conventional farms no nesting activity was found during the peak of the season (early May to early June). On organic farms 27% of all nests was successful. Increasing the availability of suitable breeding habitat during the peak of the breeding season on conventional farms might provide one means of enhancing breeding skylark populations. On organic farms, crop management should focus on reducing nest loss due to farming operations.     

有机氧同位素分馏作用研究进展

植物有机质的氧同位素分馏机制较为复杂,受着多种因素的影响,限制了其在农业、生态学和古环境方面的广泛应用。本文探讨了植物有机质中氧元素的来源、氧同位素分馏机制及影响因素,以期有助于有机氧同位素的应用研究。     

太湖CDOM紫外吸收特性及其分子量时空分布特征

基于2006年8月16日、2007年3月28日对太湖梅梁湾15个样点和2007年11~12月对全湖61个样点的有色溶解性有机物(CDOM)吸收系数观测数据,对CDOM分子量相对大小的时空差异及其影响因素进行了分析.结果表明,梅梁湾地区主要富集的是高分子量CDOM,而大太湖地区则较为复杂,北部地区主要是高分子量的CDOM占据主导地位;而在太湖东西部,主要是低分子量的CDOM;南太湖区域,高分子量的CDOM和低分子量的CDOM相对平衡.不同波长范围内CDOM吸收模型的斜率系数(S)值对CDOM的分子组成的敏感性具有一定的差异性,UVR最为敏感,其次是UV-A,再次为UV-B,UV-C最不敏感.梅梁湾CDOM主要影响因素是陆源,陆源影响的强度随季节的变化具有一定的差异,其中8月份最强,其次是3月份,最弱为11月份.     

Clogging processes caused by biofilms growth and organic particles accumulation in lab-scale vertical flow constructed wetlands

The accumulation of organic matter in substratum pores is regarded as an important factor causing clogging in the subsurface flow constructed wetlands.In this study,the developing process of clogging separately caused by biofilm growth and organic particles accumulation instead of total organic matter accumulation was investigated in two groups of lab-scale vertical flow constructed wetlands (VFCWs) fed with glucose (dissolved organic matter) and starch (particulate organic matter) influent.Results showed that the growth of biofilms within the substratum pores certainly caused remarkable reduction of effective porosity,especially for the strong organic wastewater,whereas its influence on infiltration rate was negligible.It was implied that the most important contribution of biofilm growth to clogging is accelerating the occurrence of clogging.In comparison with biofilm growth,particles accumulation within pores could rapidly reduce infiltration rate besides effective porosity and the clogging occurred in the upper 0-15 cm layer.With approximately equal amount of accumulated organic matter,the effective porosity of the clogged layer in starch-fed systems was far less than that of glucose-fed systems,which indicated that composition and accumulation mode of the accumulated organic matter played an important role in causing clogging besides the amount.According to the results,some related methods to prevent and recover the clogging phenomenon were suggested.     

秋季南海珠江口和北部湾溶解有机物的光降解

利用三维荧光光谱分析手段,结合吸收光谱测定,分析了2007年10月中国珠江口及北部湾水体中4个典型有色溶解有机物(CDOM)样在太阳光辐照下的光降解特性.结果表明,珠江口及广西沿海CDOM样受陆源输入影响较大,而北部湾中部的HX样具有典型海洋CDOM特征,80m水深的HN样则受到北部湾环流的主要影响.这些CDOM样品中均观测到类腐殖质荧光峰A、C、M以及类色氨酸荧光峰R、T,它们的荧光峰强度及吸收系数a(280)在秋季短期日光辐照下发生了较明显的光化学降解,受陆源输入影响较大的珠江口及广西沿海样品的光降解程度高于北部湾的远岸样品,反映出它们含有更多的发色团.光降解未引起CDOM荧光峰位置的显著变化,类腐殖质荧光峰M和A、类蛋白质荧光峰R和T的强度变化趋势一致,表明这两对峰具有相似的性质.A峰区存在的双峰现象表明其为多个荧光组分的叠加.CDOM吸收光谱的光谱斜率S(270～350)随光辐射而逐渐增加,可用于指示光降解引起的CDOM分子量的减小趋势.研究表明,光降解在南海生源要素的生物地球化学循环中起重要作用.     

堆肥嗜热纤维素分解菌的筛选鉴定及其强化堆肥研究

对采集于农业堆肥高温期的微生物样品进行30d的高温驯化,驯化完成后从中筛选得到15株嗜热纤维素分解菌,经形态学特征、生理生化反应及16S rDNA序列同源性比对鉴定为:Bacillus sp3株,Paenibacillus sp1株,Bacillus licheniformis3株,Bacillus subtilis4株,Brevibacillus borstelensis1株,Bacillus coagulans3株.将筛选得到的菌种添加至高纤维素含量的堆体进行效果验证,结果表明添加嗜热纤维素分解菌对堆肥pH变化无显著影响,但可提高堆肥高温期温度、延长高温期并显著地降低堆肥产品的C/N和有机质含量,显著降低纤维素和半纤维素含量,加快堆肥腐熟.堆体有机质降解动力学结果表明,堆体接菌和不接菌处理的有机质最大降解度分别为62.5481%和61.7101%,速率常数分别为0.1250d-1和0.1051d-1,接菌处理的堆肥比对照堆肥提前6d达到稳定.研究表明,添加筛选的嗜热纤维素分解菌能缩短堆肥周期.     

滇池水体总悬浮物散射系数参数化模型

总悬浮物的散射系数是水体非常重要的固有光学量之一,散射系数的参数化研究,对于水体生物光学模型的构建具有非常重要的意义.2009年9月对滇池水体25个样点进行野外采样,对滇池水体水质参数、悬浮物的吸收、散射特征进行分析,并利用乘幂模型对散射系数进行参数化,分析了模型精度与色素颗粒物吸收之间的关系,进而改进乘幂模型.结果表明,在色素颗粒物吸收较强的波段,普通乘幂模型的平均相对误差为0.08,模型改进后相对误差缩小为0.02;在色素颗粒物吸收较弱的波段,会出现模型的过修正,这主要取决于色素颗粒物的吸收,因此,没有必要对乘幂模型进行修正.