Hydrogen, carbon and sulphur isotope ratios in peat: the role of diagenessis and water regimes in reconstruction of past climates

We demonstrate that carbon, hydrogen and sulphur isotope ratios both, in the total peat (¹³C_tp=–25.52 to –28.27, D_tp=–78.67 and –109.24, ³⁴S=4.35 to 19.87), and in cellulose from the peat (¹³C_nc=–25.06 to –27.33 and D_nc=–92.43 to –118.02) are not affected by postdepositional changes. Therefore, the original isotope composition of plants are in general preserved in the peat and represent an archive of the past environmental variations. These can be supported by (i) good correlations between ¹³C_tp and ¹³C_nc, and between D_tp and D_nc, (ii) high horizontal homogeneity of ¹³C_tp and ¹³C_nc in the scale of one peat-bog – the same major factor(s) control(s) C isotopic ratios, (iii) no correlation between organic sulphur concentrations and ³⁴S value –³⁴S results from variations in the water level.This revised version was published online January 2005 with corrections to the title.     

Removal of textile dyes from water by the electro-Fenton process

An environmentally friendly electrochemical treatment, electro-Fenton process, was applied to the depollution of a synthetic dismissal composed of three dyes, yellow drimaren, congo red and methylene blue, frequently used in textile and dyehouses. Here, we show that those dyes and their mixture are quickly degraded under current controlled electrolysis conditions, leading to an almost complete mineralization. The results show the efficiency of electro-Fenton process to quickly degrade aqueous effluents polluted by synthetic organic dyes.     

The emergence of stable isotopes in environmental and forensic geochemistry studies: a review

In the past decade, environmental forensics has emerged as a discipline directed toward determining parties liable for causing spills of contaminants into the environment. Such investigations, while geared toward determining the guilty parties in order to recover costs of the cleanup and remediation, require various questions to be addressed. These include determination of the nature of the product; Where did it come from?; Extent of weathering, if any; How long has it been there?; and Is it degrading naturally? Traditionally, these studies have been addressed through utilization of techniques such as gas chromatography (GC) and gas chromatography–mass spectrometry (GCMS). However, in recent years, stable isotopes, primarily determined through the use of combined gas chromatography–isotope ratio mass spectrometry (GCIRMS), have emerged as an equally important tool in environmental forensics. For relatively low molecular, volatile compounds such as MTBE, BTEX, or chlorinated solvents, the isotopes, primarily carbon and hydrogen, have been used extensively for evaluating the onset of natural attenuation. For larger molecules such as PCBs or PAHs, in which the effects of biodegradation on the isotope composition of these molecules is minimal, the isotopic fingerprints of the individual compounds can be used for correlation purposes. In this paper, a brief introduction to isotope geochemistry will be given, followed by a review of applications of stable isotopes to a variety of environmental problems. While the review may not necessarily be exhaustive, it will provide a comprehensive overview of areas where isotopes have been used and potential applications for the future. Most of the review is concerned with carbon and hydrogen isotopes, although a brief overview of the emerging area of chlorine isotopes will also be discussed.     

Gas-phase degradation of CCl<Subscript>4</Subscript>, CHCl<Subscript>3</Subscript> and CH<Subscript>2</Subscript>Cl<Subscript>2</Subscript> over metallic Fe

We studied the hydrolysis of gas-phase carbon tetrachloride (CCl₄), chloroform (CHCl₃), and dichloromethane (CH₂Cl₂) over a metallic Fe surface for its application in combination with air stripping and soil vapour extraction. The effects of chlorocarbon concentration, type and preparation of the iron-containing material, humidity, and temperature on process performance are reported. The hydrolysis of chlorinated methane derivatives is catalysed by metallic iron resulting in a noticeable decrease of the reaction temperature. The reaction kinetics were found to be consistent with the Langmuir-Hinshelwood model.     

SPACSYS: Integration of a 3D root architecture component to carbon, nitrogen and water cycling—Model description

It is an ongoing challenge to develop and demonstrate management practices that increase the sustainability of agricultural systems. Soil carbon and nitrogen dynamics directly affect soil quality, crop productivity and environmental impacts. Root systems are central to the acquisition of water and nutrients by plants, but are also a major pathway for the inputs of carbon and nutrients to soil. The complexity of both biotic and abiotic interactions, combined with stochastic changes in root architecture, makes it difficult to understand below-ground dynamics on the basis of experimentation alone. The integration of dynamic models of above-ground growth, three-dimensional root system demography, and interactions between plants and the environment, into one single model is a major challenge because of the complexity of the systems.In order to understand the interaction between a plant and the environment, it is advantageous to develop a model framework to integrate submodels that simulate various plant and environmental components. The objective of this paper is to outline a mechanistic and process-based model, which is capable of simulating interactions among environmental conditions around plants, plant growth and development, nitrogen and carbon cycles, with a three-dimensional root system submodel as an interface.The model presented in this paper is a mixed dimensional, multi-layer, field scale, weather-driven and daily time-step dynamic simulation model. The current version includes a plant growth and development component, a nitrogen cycling component, a carbon cycling component, plus a soil water component that includes representation of water flow to field drains as well as downwards through the soil layers, together with a heat transfer component. The components themselves and linkage among components are designed using object-oriented techniques, which makes the model robust, understandable and reusable. The components are implemented in the C++ programming language, and inputs and outputs of all components are organised as a database in either Microsoft^® SQL Server 2000, Access 2000 or MySQL5.0. Root architecture is visualised by using the OpenGL graphics system. Preliminary validation with two separate experimental datasets shows that the model can reasonably simulate root systems, nitrogen cycling, water movement and plant growth.     

生态足迹改进模型在可持续发展评价中的应用研究

生态足迹分析通过计算生物物理量来衡量人类经济活动对自然生态系统服务的需求与自然生态系统承载力之间的协调程度,因为该方法思路新颖、计算简便而被广泛应用于国家和地区的可持续发展评价中。文章针对Rees W E等提出的生态足迹模型中存在的问题与不足(如:产量因子和当量因子参数选取偏差,生态功能差异表现不充分,模型不具动态性等)提出了改进生态足迹模型。利用改进后的生态足迹模型计算天津市1995—2005年的生态足迹及其动态变化值,天津市耕地、牧草地、林地、水域和化石能源用地人均生态足迹盈亏分别为0.0009,-0.3224,-0.1991,0.0255,-1.9600hm2·人-1,除耕地和水域略有盈余外,牧草地、林地和化石能源用地人均生态赤字均呈递增趋势。1995—2005年间天津市单位产值能耗居高不下、人口规模增长与建筑用地扩张是导致人均生态赤字扩大的根本原因。文章提出的生态足迹改进模型可以动态指示区域或城市经济发展水平与自然生态系统承载力之间的协调程度,为区域可持续发展战略制定和实施提供决策依据。     

Biotechnology to develop innovative syntheses using CO2

We present an overview of possible biotechnological applications for using carbon dioxide for the synthesis of chemicals. These approaches are very appealing as they contribute to the implementation of new synthetic methodologies that reduce waste and make a better use of carbon and energy. Several synthetic approaches will be considered including both the incorporation of the whole COO moiety or its reduction to other C₁ molecules. Each option will be discussed making a comparison between the natural and artificial process in order to highlight the possibility to learn from Nature and develop useful mimetic or enzymatic systems.     

Cold season CH4, CO2 and N2O fluxes from freshwater marshes in northeast China

Cold season (winter and thaw) CH₄, CO₂ and N₂O fluxes from freshwater marshes (47°35′N, 133°31′E, Northeast China) were measured, using the static chamber method. The mean CH₄ and CO₂ fluxes from Carex lasiocarpa (Cl) were 0.5 ± 0.19 and 6.23 ± 1.36 mg C m⁻² h⁻¹, respectively, and those from Deyeuxia angustifoli (Da) were 0.18 ± 0.15 and 5.22 ± 2.48 mg C m⁻² h⁻¹, respectively in winter. There was no significant difference between Cl and Da (p > 0.05). The contributions of winter CH₄ fluxes were about 5.5% and 3% in the Cl and Da, respectively. Marshes are an important potential N₂O sink in winter season in northeast China. During thaw, the CH₄ and CO₂ emissions rapidly increased, 4.5–6 times of winter emissions. Wetland became a source of N₂O. Cold season gases flux from northern wetlands play an important role in the seasonal gas exchange.     

Quantifying chlorinated ethene degradation during reductive dechlorination at Kelly AFB using stable carbon isotopes

Stable isotope analysis of chlorinated ethene contaminants was carried out during a bioaugmentation pilot test at Kelly Air Force Base (AFB) in San Antonio Texas. In this pilot test, cis-1,2-dichloroethene (cDCE) was the primary volatile organic compound. A mixed microbial enrichment culture, KB-1, shown in laboratory experiments to reduce chlorinated ethenes to non-toxic ethene, was added to the pilot test area. Following bioaugmentation with KB-1, perchloroethene (PCE), trichloroethene (TCE) and cDCE concentrations declined, while vinyl chloride (VC) concentrations increased and subsequently decreased as ethene became the dominant transformation product. Shifts in carbon isotopic values up to 2.7 per thousand, 6.4 per thousand, 10.9 per thousand and 10.6 per thousand were observed for PCE, TCE, cDCE and VC, respectively, after bioaugmentation, consistent with the effects of biodegradation. While a rising trend of VC concentrations and the first appearance of ethene were indicative of biodegradation by 72 days post-bioaugmentation, the most compelling evidence of biodegradation was the substantial carbon isotope enrichment (2.0 per thousand to 5.0 per thousand) in ?13C(cDCE). Fractionation factors obtained in previous laboratory studies were used with isotope field measurements to estimate first-order cDCE degradation rate constants of 0.12 h(-1) and 0.17 h(-1) at 115 days post-bioaugmentation. These isotope-derived rate constants were clearly lower than, but within a factor of 2-4 of the previously published rate constant calculated in a parallel study at Kelly AFB using chlorinated ethene concentrations. Stable carbon isotopes can provide not only a sensitive means for early identification of the effects of biodegradation, but an additional means to quantify the rates of biodegradation in the field.     

上海市路边环境空气黑碳气溶胶污染特征及影响因素研究

为研究上海市路边环境空气黑碳(BC)的污染特征,采用连续监测方法对2016年1月至2018年12月上海市路边环境空气BC浓度进行了监测,并同步监测了气象因子,分析了BC的时间变化特征,探讨了气象因素对BC的影响以及不同空气质量等级下BC浓度水平。结果表明:2016、2017、2018年上海市路边环境空气BC年均质量浓度分别为(2 908±2 189)、(2 959±2 224)、(2 824±2 002) ng/m3,呈现出下降趋势;2016、2017、2018年BC与PM2.5年均质量浓度比分别为9. 30%、9. 20%、9. 50%;BC季节变化特征明显,整体表现为春夏高、秋冬低的特点;昼夜变化特征均呈现出双峰分布,第一个峰值均出现在06:00,第二个峰值均出现在16:00-19:00,且第一个峰值高于第二个峰值。气象因素对BC有一定影响,在降水、相对湿度低以及非静风条件下BC浓度较低。随着上海市空气质量由好转差,上海市路边环境空气BC浓度均呈现上升趋势,空气质量为良、轻度污染、中度污染、重度污染时路边环境空气BC平均浓度分别较空气质量为优时增加了0. 38、0. 96、1. 61、1. 96倍。