土壤环境多氯二苯并二噁英/呋喃(PCDD/Fs)污染及其修复研究进展

多氯二苯并二噁英/呋喃(PCDD/Fs)是持久性有毒有机污染物,易沉积在土壤环境中,通过生物放大和生物富集最终输入到人和动物体内,对生态系统和人体健康有极大的威胁.本文在对PCDD/Fs环境行为与污染来源进行阐述的基础上,概述了PCDD/Fs污染的地域性特点以及土壤中PCDD/Fs的背景值和污染控制参考值;分析了我国土壤PC-DD/Fs污染状况和潜在污染源,江西、广州贵屿、长江三角洲、台湾南部、浙江台州、天津某化工厂等6个区域污染较严重,主要污染源有含氯化学品的生产与使用,垃圾焚烧和纸浆生产.最后,介绍了PCDD/Fs污染土壤的处置方法与修复技术,主要有物理化学处置方法、微生物修复方法、植物修复方法、植物-微生物联合修复方法,并对今后该研究方向进行了展望.     

Day length regulates seasonal patterns of stomatal conductance in Quercus species

Vapour pressure deficit is a major driver of seasonal changes in transpiration, but photoperiod also modulates leaf responses. Climate warming might enhance transpiration by increasing atmospheric water demand and the length of the growing season, but photoperiod-sensitive species could show dampened responses. Here, we document that day length is a significant driver of the seasonal variation in stomatal conductance. We performed weekly gas exchange measurements across a common garden experiment with 12 oak species from contrasting geographical origins, and we observed that the influence of day length was of similar strength to that of vapour pressure deficit in driving the seasonal pattern. We then examined the generality of our findings by incorporating day-length regulation into well-known stomatal models. For both angiosperm and gymnosperm species, the models improved significantly when adding day-length dependences. Photoperiod control over stomatal conductance could play a large yet underexplored role on the plant and ecosystem water balances.     

Habitat disturbance modifies dominance,coexistence, and competitive interactions in tropical ant communities

1. Interspecific competition is a major structuring principle in ecological communities. Despite their prevalence, the outcome of competitive interactions is hard to predict, highly context-dependent, and multiple factors can modulate such interactions. 2. We tested predictions concerning how competitive interactions are modified by anthropogenic habitat disturbance in ground-foraging ant assemblages inhabiting fragmented Inter-Andean tropical dry forests in southwestern Colombia, and investigated ant assemblages recruiting to baits in 10 forest fragments exposed to varying level of human disturbance. 3. Specifically, we evaluated how different components of competitive interactions (patterns of species co-occurrence, resource partitioning, numerical dominance, and interspecific trade-offs between discovery and dominance competition) varied with level of habitat disturbance in a human-dominated ecosystem. 4. Multiple lines of evidence suggest that the role of competitive interactions in structuring ground-foraging ant communities at baits varied with respect to habitat disturbance. As disturbance increased, community structure was more likely to exhibit random co-occurrence patterns, higher levels of monopolization of food resources by dominant ants, and disproportionate dominance of a single species, the little fire ant (Wasmannia auropunctata). At a regional scale, we found evidence for a trade-off between dominance and discovery abilities of the 15 most common species at baits. 5. Together, these results suggest that human disturbance modifies the outcome of competitive interactions in ground-foraging ant assemblages and may promote dominant species that reduce diversity and coexistence in tropical ecosystems.     

Share the wealth: Trees with greater ectomycorrhizal species overlap share more carbon

The mutualistic symbiosis between forest trees and ectomycorrhizal fungi (EMF) is among the most ubiquitous and successful interactions in terrestrial ecosystems. Specific species of EMF are known to colonize specific tree species, benefitting from their carbon source, and in turn, improving their access to soil water and nutrients. EMF also form extensive mycelial networks that can link multiple root‐tips of different trees. Yet the number of tree species connected by such mycelial networks, and the traffic of material across them, are just now under study. Recently we reported substantial belowground carbon transfer between Picea, Pinus, Larix and Fagus trees in a mature forest. Here, we analyze the EMF community of these same individual trees and identify the most likely taxa responsible for the observed carbon transfer. Among the nearly 1,200 EMF root‐tips examined, 50%–70% belong to operational taxonomic units (OTUs) that were associated with three or four tree host species, and 90% of all OTUs were associated with at least two tree species. Sporocarp ¹³C signals indicated that carbon originating from labelled Picea trees was transferred among trees through EMF networks. Interestingly, phylogenetically more closely related tree species exhibited more similar EMF communities and exchanged more carbon. Our results show that belowground carbon transfer is well orchestrated by the evolution of EMFs and tree symbiosis.     

Evaluation of FT-IR spectroscopy as a tool to quantify bacteria in binary mixed cultures

Fourier-transform infrared (FT-IR) spectroscopy is known as a high-resolution method for the rapid identification of pure cultures of microorganisms. Here, we evaluated FT-IR as a method for the quantification of bacterial populations in binary mixed cultures consisting of Pseudomonas putida and Rhodococcus ruber. A calibration procedure based on Principal Component Regression was developed for estimating the ratio of the bacterial species. Data for method calibration were gained from pure cultures and artificially assembled communities of known ratios of the two member populations. Moreover, to account for physiological variability, FT-IR measurements were performed with organisms sampled at different growth phases. Measurements and data analyses were subsequently applied to growing mixed cultures revealing that growth of R. ruber was almost completely suppressed in co-culture with P. putida. Population ratios obtained by fatty acid analysis as an independent reference method were in high agreement with the FT-IR derived ratios.     

Identifying and mapping the protective forests of southeast Mt. Olympus as a tool for sustainable ecological and silvicultural planning, in a multi-purpose forest management framework

Rural development in forested lands and high altitude ecosystems created new regimes and disturbances that set protective function of forests as the most fundamental of all forest functions. Considering protective forests as engineering structures against natural hazards and risks, such as erosion, able to replace costly manmade infrastructures, a methodology is presenting aiming at their spatial identification in a changing mountainous environment. The methodology followed is based on field observations, calibrated models, topographical, geological and climatic data as well as human presence indicators combined properly in a GIS environment. Analysis showed that some forest soils are prone to erosion hazard unable to absorb disturbances like selective logging, revealing the protective role of their forest cover. The spatial identification of the forests with a particular protective function is the necessary step required for the design of a sustainable management of high elevated ecosystems.     

Investigation of intermittent air exposure on four-stage and one-stage anaerobic semi-continuous mixed-acid fermentations

This study evaluated anaerobic mixed-acid countercurrent fermentations in both strict S (minimal oxygen) and relaxed R (high oxygen) conditions. In relaxed fermentations, filter solids and liquids were exposed to air for 90 min every 56 h. The total acid concentrations for four-stage trains were 23.0 (4S) and 22.1 (4R) g/L_Liq, and for one-stage trains were 17.2 (1S) and 18.4 (1R) g/L_Liq. The strict and relaxed trains had statistically similar exit yields. The strict trains had significantly more high-molecular-weight carboxylic acids. The relaxed trains had slightly higher conversion and slightly lower selectivity, but not significantly. Air exposure had no significant effect on the bacterial profiles of the strict and relaxed fermentations. For all fermentations, the most abundant bacterial genus was Prevotella, a strict anaerobe. This study shows that the mixed-culture community is oxygen tolerant because it maintains fermentation performance during oxygen-induced stress.     

Improving the simultaneous removal efficiency of COD and color in a combined HABMR-CFASR system based MPDW. Part 1: optimization of operational parameters for HABMR by using response surface methodology

The aim of this study was to implement central-composite design (CCD) and response surface methodology (RSM) to optimize the operational parameters for hybrid anaerobic baffled microbial reactor (HABMR) remedying mixed printing and dyeing wastewater (MPDW). The individual and interactive effects of three variables, hydraulic retention time (HRT), pH, sludge loading rate (SLR) on the COD and color removal rates were evaluated. In the area of HRT: 12.5-13.9 h, pH: 9.0-9.5 and SLR: 0.27-0.33 kg COD/(kg MLVSSd), COD and color removal rates of HABMR exceeded 40% and 60%, simultaneously. The check experiment revealed that the amount of COD and color in the effluent could be decreased by 9.97% and 10.12% compared to the usual operating conditions, respectively. The results verified that the RSM was useful for optimizing the operational parameters of HABMR in treating MPDW.     

Exploring the properties of mixed valence cyanide bridged dinuclear complexes: Solvent stabilization of electronic isomers

We report here the synthesis and properties of a family of mixed-valence cyanide-bridged dinuclear complex ions trans-[(L′L₄Ru^II(μ-NC)Fe^III(CN)₅]⁻ (with L = pyridine or 4-dimethylaminopyridine (dmap) and L′ = pyridine, 4-methoxypyridine (meopy) or 4-dimethylaminopyridine)) whose properties could be adjusted smoothly by changing the acceptor properties of the solvent and the σ donor properties of the L′ pyridine ligand. In solution these complexes exhibit an intense solvent-dependent MM′CT (Ru^II → Fe^III) absorption in the near infrared region. Analysis of this band in different complexes and solvents suggests an enhanced interaction as the energies of the metal centers come closer. From this trend the anion trans-[(dmap)₅Ru(μ-NC)Fe(CN)₅]⁻ (dmap = 4-dimethylaminopyridine) in water is expected to belong to the class II-III, but its spectral properties indicates a ground state with Ru(III)-Fe(II) character. The stabilization of this electronic isomer is probably related to the better donor properties of the hexacyanoferrate(II) moiety and its stronger interaction with water.