分点进水A/O工艺处理低碳源生活污水的脱氮性能研究

针对低C/N比污水脱氮的难点问题,在缺氧段不同点设置进水口,采用分点进水A/O工艺处理校园生活污水.考察了在污泥回流比为100%,硝化液回流比为200%,分流比为1∶1,缺氧池水力停留时间(HRT)分别为2、2.4和3 h情况下,分点进水A/O工艺的反硝化性能,并与传统的A/O工艺进行比较.结果表明,当缺氧池的水力停留...     

皂素提取头道液的典型有机物组成研究

利用紫外、红外拉曼光谱和GC/MS对传统皂素生产工艺、S-F工艺和E-S工艺头道液废水的有机物组成进行了分析。结果表明,传统工艺、S-F和E-S工艺头道液废水的有机物主要是醛类,此外,传统工艺头道液中检测到的22种有机物中,还有大量生物难降解的杂环类（12.24%）;而S-F和E-S工艺头道液中检测到的25种和31种有...     

全球实施《21世纪议程》的主要进展与趋势

从全球角度对世界环境与发展大会以来《21世纪议程》的主要实施进展进行了总结.分析表明,全球经济实现了大幅增长,在消除贫困、推进城市化、节约集约利用资源等方面取得积极进展,但在有关国际公约和承诺的履行方面尚需付出巨大努力.通过对当前全球可持续发展面临的重大挑战和未来趋势进行的分析,认为当前全球可持续发展主要面临三大挑战,即重大全球性环境问题对人类生存构成的直接威胁加大、发展空间争夺更趋激烈和全球性民生问题凸显;全球可持续发展主要呈现四大趋势,即可持续发展进一步由理念向全球行动转化、全球向绿色发展转型、新兴发展中国家成为全球可持续发展的重要推动力和可持续发展领域国际关系呈现竞争性合作.     

Determining C/N ratios for typical organic wastes using biodegradable fractions

It is well established that an optimal aerobic and anaerobic microbial metabolism is achieved with a C/N ratio between 20 and 30. Most studies are currently based on chemically-measured carbon and nitrogen contents. However, some organic wastes can be composed of recalcitrant carbon fractions that are not bioavailable. To know the biodegradable C/N ratio, two different methods to determine the aerobic and anaerobic biodegradable organic carbon (BOC_AE and BOC_AN) are proposed and used to analyze a wide variety of different organic samples. In general, raw wastes and digested products have more amount of BOC_AE. On the contrast, the samples collected after an aerobic treatment have higher content of BOC_AN. In any case, all the BOC fractions are lower than the total organic carbon (TOC). Therefore, the C/N ratios based on BOC are always lower than the total C/N ratio based on the TOC measure. The knowledge of the real bioavailable C/N ratio is crucial for the biological treatments of organic materials. To reduce the test time necessary for BOC determination, the values of BOC for all the samples obtained at different times were compared and correlated with the final BOC. A method that allows for the determination of BOC_AE in 4 d is proposed. In relation to the anaerobic assay, the biogas potential calculated after 21 and 50 d was positively correlated with the final potential defined after 100 d of assay.     

Stable isotope signatures reflect competitiveness between trees under changed CO2/O3 regimes

Here we synthesize key findings from a series of experiments to gain new insight on inter-plant competition between juvenile beech (Fagus sylvatica) and spruce (Picea abies) under the influence of increased O₃ and CO₂ concentrations. Competitiveness of plants was quantified and mechanistically interpreted as space-related resource investments and gains. Stable isotopes were addressed as temporal integrators of plant performance, such as photosynthesis and its relation to water use and nitrogen uptake. In the weaker competitor, beech, efficiency in space-related aboveground resource investment was decreased in competition with spruce and positively related to Δ¹³C, as well as stomatal conductance, but negatively related to δ¹⁸O. Likewise, our synthesis revealed that strong belowground competition for water in spruce was paralleled in this species by high N assimilation capacity. We suggest combining the time-integrative potential of stable isotopes with space-related investigations of competitiveness to accomplish mechanistic understanding of plant competition for resources.     

Studying soil organic matter using 13C CP-MAS NMR: the effect of soil chemical pre-treatments on spectra quality and representativity

¹³C CP-MAS NMR spectroscopy is a technique that has proved to be useful in studying soil organic matter (SOM). Nevertheless, NMR spectra exhibit a weak signal and have very low resolution due to: the low natural abundance of ¹³C (1.1 % of C) in SOM, the generally low SOM content of soils, and the presence of paramagnetic impurities. This paper studies the effects of soil chemical pre-treatments on ¹³CP-MAS NMR spectra quality and spectra representativity i.e. soil C mass balance.

After chemical pre-treatment to increase total organic carbon (TOC) content and C/Fe ratio, eight soils characterized by different levels of organic carbon content and C/Fe ratios were studied using ¹³CP-MAS NMR. Moreover, where chemical treatments were not applicable due to high carbon losses, the number of ¹³CP-MAS NMR scans was increased in order to obtain satisfactory spectra.

Results show that chemical pre-treatment of soils with C/Fe > 1 caused high C losses. Bulk soils were therefore studied by increasing the number of ¹³CP-MAS NMR scans. Acceptable spectra were obtained from 8K scans (1K = 1024 transient). On the other hand, even when a large number of scan (32K) are used, soil with C/Fe < 1 cannot be studied. As these soils are characterized by low C losses after HCl treatments (range of 2.9–25.4%), a pre-treatment of at least 1.39 mol l⁻¹ HCl removes excess Fe and at the same time increases C/Fe ratio resulting in 32K scans providing good spectra.     

Effects of long-term soil amendment with sewage sludges on soil humic acid thermal and molecular properties

Sewage sludges are frequently used as soil amendments due to their high contents of organic matter and nutrients, particularly N and P. However, their effects upon the chemistry of soil humic acids, one of the main components of the soil organic matter, need to be more deeply studied in order to understand the relation between organic matter structure and beneficial soil properties. Two sewage sludges subjected to different types of pre-treatment (composted and thermally dried) with very different chemical compositions were applied for three consecutive years to an agricultural soil under long-term field study. Thermal analysis (TG–DTG–DTA) and solid-state ¹³C NMR spectroscopy were used to compare molecular and structural properties of humic acids isolated from sewage sludges, and to determine changes in amended soils. Thermally dried sewage sludge humic acids showed an important presence of alkyl and O/N-alkyl compounds (70%) while composted sludge humic acids comprised 50% aromatic and carbonyl carbon. In spite of important differences in the initial chemical and thermal properties of the two types of sewage sludges, the chemical and thermal properties of the soil humic acids were quite similar to one another after 3 years of amendment. Long-term application of both sewage sludges resulted in 80–90% enrichment in alkyl carbon and organic nitrogen contents of the soil humic acid fraction.