干活性污泥吸附水中染料的试验研究

以城市污水处理厂干活性污泥为吸附剂对染料直接深棕M、酸性媒介棕RH进行了吸附研究,结果表明,吸附过程能很好地用二级速率表达式表示,同时也可用Lagergren一级速率方程描述。其一级吸附速率常数k1分别为0.0204min-1和0.0068min-1,二级吸附速率常数k2分别为0.00592和0.00589gmg-1min-1。两者的吸附特性不同,其吸附等温线前者符合Freundlich方程,后者既符合Freundlich方程也符合Langmuir方程。吸附平衡时间、去除率亦不同,前者明显大于后者,达到吸附平衡的时间分别为120min和240min。两种染料的正辛醇/水分配系数logP计算数值分别为4.65和-0.22,这一顺序与两种染料在干污泥上的吸附行为相符。     

Effects of ozone on inter- and intra-species competition and photosynthesis in mesocosms of Lolium perenne and Trifolium repens

Trifolium repens and Lolium perenne were exposed as both monocultures and two-species mixtures to an episodic rural ozone regime in large, well-watered containers within solardomes for 12 weeks. There were reductions in biomass for T. repens, but not L. perenne, and the proportion of T. repens decreased in ozone-exposed mixtures compared to the control. In addition, leaf biomass of T. repens was maintained at the expense of biomass partitioning to the stolons. The decreased growth corresponded with decreased photosynthetic capacity for T. repens, however, by the end of the exposure there was also decreased photosynthetic capacity of L. perenne, a species previously considered insensitive to ozone. The observed decreases in photosynthetic efficiency and capacity in elevated ozone indicate that the ability of such ubiquitous vegetation to act as a sink for atmospheric carbon may be reduced in future climates.     

Polycyclic aromatic hydrocarbon (PAH) contamination of surface sediments and oysters from the inter-tidal areas of Dar es Salaam, Tanzania

Surface sediment and oyster samples from the inter-tidal areas of Dar es Salaam were analyzed for 23 polycyclic aromatic hydrocarbons (PAHs) including the 16 compounds prioritized by US-EPA using GC/MS. The total concentration of PAHs in the sediment ranged from 78 to 25,000 ng/g dry weight, while oyster concentrations ranged from 170 to 650 ng/g dry weight. Hazards due to sediment contamination were assessed using Equilibrium Partitioning Sediment Benchmarks and Threshold Effect Levels. Diagnostic indices and principle component analysis were used to identify possible sources. Interestingly, no correlation between sediment and oyster concentrations at the same sites was found. This is supported by completely different contamination patterns, suggesting different sources for both matrices. Hazard assessment revealed possible effects at six out of eight sites on the benthic communities and oyster populations. The contribution of PAH intake via oyster consumption to carcinogenic risks in humans seems to be low.     

Specificity of communication channels in four limacodid moths: Darna bradleyi, Darna trima, Setothosea asigna, and Setora nitens (Lepidoptera: Limacodidae)

Summary. Darna bradleyi Holloway, D. trima Moore, Setothosea asigna van Eecke and Setora nitens Walker are sympatric and coseasonal limacodid moths in plantations of oil palm, Elaeis guineensis Jacq. (Arecales: Palmae), in Borneo, southeast Asia. We tested the hypothesis that these four species maintain reproductive isolation through specificity in diel periods of communication, microlocation for communication and/or communication signal (pheromone). Studying diel periodicity of calling behavior by female moths and response by male moths to traps baited with virgin females or synthetic pheromone, we determined that sexual communication of D. bradleyi and D. trima took place from ˜17:30 to 18:45 hr and that of S. asigna and S. nitens from ˜18:45 to 20:00 hr and from ˜18:30 to 19:30 hr, respectively. Over 80% of male S. asigna and S. nitens were captured in pheromone-baited traps suspended >5 m high, whereas male D. bradleyi and D. trima were captured mostly in traps <5 m high. Synthetic pheromone baits attracted male moths in a species-specific manner. Moreover, baits containing both S. asigna and S. nitens pheromones failed to attract any male moths, indicating that female S. asigna and S. nitens, with overlapping communication periods, use bifunctional pheromone components that attract conspecific males while repelling heterospecifics. Similarly, addition of D. bradleyi pheromone to S. asigna or S. nitens pheromone reduced attraction of male S. asigna and S. nitens. The failure of D. bradleyi and D. trima, which overlap in time and microlocation for communication, to evolve bifunctional pheromones may be attributed to the recent occurrence of sympatry between D. bradleyi and D. trima in Borneo, apparently too recent for bifunctional pheromones to have evolved. We conclude that D. bradleyi, D. trima, S. asigna and S. nitens utilize any or all of diel periodicity, intra and interspecific effects of communication signal and/or microlocation for signaling, allowing these limacodids to co-inhabit the same habitat and remain reproductively isolated. Received 5 May 2000; accepted 18 August 2000     

Seasonal variation and partition of trace metals (Fe, Zn, Cu, Mn, Cr, Cd and Pb) in surface sediments: relationship with physico-chemical variables of water from the Calabar River, South Eastern Nigeria

The seasonal variation and partition of trace metals (Fe, Cu, Zn, Mn, Cd, Cr and Pb) in the surface sediments of the Calabar River are reported. Chemical partition of the metals in the sediments reveals that 2–30% of the total metal load was contributed by the non-detrital (acid-soluble) fraction, while fine-grained host minerals/compounds are the main carriers of the detrital (acid-insoluble) fraction (70–98%). Using multivariate statistical analysis, the seasonal fluctuations in the distribution of some of the metals show significant influence by physio-chemical changes (dissolved oxygen, pH, salinity and conductivity) in the water column. Fe–Mn oxide grain coatings and sulphide materials have been identified as scavengers of some of the non-detrital and detrital trace metals in the sediments. On the basis of index of geoaccumulation (I-geo) and comparison with previous studies, the Calabar River surface sediments have been classified as unpolluted.     

Partitioning of heavy metals in the surface sediments of Quanzhou Bay wetland and its availability to Suaeda australis

In order to investigate distributions of heavy metal pollution in Quanzhou Bay wetland, the total concentration and chemical partitioning of a number of heavy metals （Cu, Zn, Cd, Pb, Cr, Hg） in sediments of three sampling sites of Quanzhou Bay wetland and their availability to Suaeda australis were analyzed. The Geoaccumulation Index （Igeo） values reveal that the sediments of three sampling sites may all be considered as moderately contaminated for Pb and Zn, and all sediments might be strongly contaminated with cadmium. The partitioning analyses revealed the measured heavy metals in three sites are bound to the exchangeable fraction at lower concentrations. The measured metals in a considerable amount are bound to the reducible and oxidizable fractions, and a high proportion of the measured heavy metals were distributed in the residual fraction in the sediment samples. The concentrations of Cd in each chemical phase extracted from the sediments are above natural global background levels and should be further investigated because of its toxicity. Suaeda australis has different accumulation abilities for the measured heavy metals. For the root and stem, the bioaccumulation ability assessed by bioaccumulation factor （BAF） for the measured heavy metals follows the decreasing order as： Cu〉Cr〉 Zn〉Cd, Pb, Hg. In the leaf, stronger bioaccumulation ability for Hg is exhibited. The heavy metal concentrations in Suaeda australis roots have positive correlations with their available fractions, while the exchangeable fraction of Cu and Cd might have be more important to both mature plant roots and seedling roots uptake than other fractions; as for Cr, the oxidizable fraction might make a greater contribution to the plant root uptake; as for Zn, the reducible fraction might make so contribution ; and for Pb, the oxidizable fraction might make a significant contribution to the mature plant root uptake, however, the exchangeable fraction might have a significant contribution to the seedling root uptake.     

Refinement of the density-modified displacement method for efficient treatment of tetrachloroethene source zones

A novel method to remediate dense nonaqueous phase liquid (DNAPL) source zones that incorporates in situ density conversion of DNAPL via alcohol partitioning followed by displacement with a low interfacial tension (IFT) surfactant flood has been developed. Previous studies demonstrated the ability of the density-modified displacement (DMD) method to recover chlorobenzene (CB) and trichloroethene (TCE) from heterogeneous porous media without downward migration of the dissolved plume or free product. However, the extent of alcohol (n-butanol) partitioning required for in situ density conversion of high-density NAPLs, such as tetrachloroethene (PCE), could limit the utility of the DMD method. Hence, the objective of this study was to compare the efficacy of two n-butanol delivery approaches: an aqueous solution of 6% (wt) n-butanol and a surfactant-stabilized macroemulsion containing 15% (vol) n-butanol in water, to achieve density reduction of PCE-NAPL in two-dimensional (2-D) aquifer cells. Results of liquid-liquid equilibrium studies indicated that density conversion of PCE relative to water occurred at an n-butanol mole fraction of 0.56, equivalent to approximately 5 ml n-butanol per 1 ml of PCE when in equilibrium with an aqueous solution. In 2-D aquifer cell studies, density conversion of PCE was realized using both n-butanol preflood solutions, with effluent NAPL samples exhibiting density reductions ranging from 0.51 to 0.70 g/ml. Although the overall PCE mass recoveries were similar (91% and 93%) regardless of the n-butanol delivery method, the surfactant-stabilized macroemulsion preflood removed approximately 50% of the PCE mass. In addition, only 1.2 pore volumes of the macroemulsion solution were required to achieve in situ density conversion of PCE, compared to 6.4 pore volumes of the 6% (wt) n-butanol solution. These findings demonstrate that use of the DMD method with a surfactant-stabilized macroemulsion containing n-butanol holds promise as an effective source zone remediation technology, allowing for efficient recovery of PCE-DNAPL while mitigating downward migration of the dissolved plume and free product.     

Divergent evolution of feeding substrate preferences in a phylogenetically young species flock of pupfish (Cyprinodon spp.)

A fundamental question in sympatric speciation is how trophic divergence is achieved. We used an extremely young (<8,000 years) species flock of pupfish (Cyprinodon spp.) from Laguna Chichancanab in south-eastern Mexico to examine divergent evolution of preferences for different feeding substrates. In a test aquarium, we presented four feeding substrates (sand, gravel, a plastic plant, and blank bottom), but no actual food was offered. The four feeding substrates were chosen to mirror the most common substrate types in Laguna Chichancanab. Previous studies demonstrated that benthic food items prevail in the diet of most Cyprinodon species. C. beltrani preferred sand, whereas C. labiosus preferred gravel. F₁ hybrids of both species showed intermediate preferences. C. maya searched for food equally at all substrates. As the test fish were reared under identical laboratory conditions (i.e., in the absence of feeding substrates), the species-specific preferences appear to be genetically fixed, suggesting rapid divergent evolution of feeding behaviors.     

Concentrations and distribution of novel brominated flame retardants in the atmosphere and soil of Ny-Ålesund and London Island, Svalbard, Arctic

Novel brominated flame retardants (NBFRs) were investigated in Arctic air and soil samples collected from Ny-Ålesund and London Island, Svalbard, during Chinese scientific research expeditions to the Arctic during 2014–2015. The concentrations of Σ₉NBFRs in the Arctic air and soil were 4.9–8.7 pg/m³ (average 6.8 pg/m³) and 101–201 pg/g dw (average 150 pg/g dw), respectively. The atmospheric concentration of hexabromobenzene (HBB) was significantly correlated with that of pentabromotoluene (PBT) and pentabromobenzene (PBBz), suggesting similar source and environmental fate in the Arctic air. No significant spatial difference was observed among the different sampling sites, both for air and soil samples, indicating that the effects of the scientific research stations on the occurrence of NBFRs in the Arctic were minor. The fugacities from soil to air of pentabromoethylbenzene (PBEB), 2,3-dibromopropyl 2,4,6-tribromophenyl ether (DPTE), and decabromodiphenylethane 1,2-bis (pentabromophenyl) ethane (DBDPE) were lower than the equilibrium value, indicating a nonequilibrium state of these compounds between air and soil, the dominant impact of deposition and the net transport from air to soil. The correlation analysis between the measured and predicted soil-atmosphere coefficients based on the absorption model showed that the impact of the soil organic matter on the distribution of NBFRs in the Arctic region was minor. To the best of our knowledge, this work is one of the limited reports on atmospheric NBFRs in the Arctic and the first study to investigate the occurrence and fate of NBFRs in the Arctic soil.     

Effects of Climate Change on Population Persistence of Desert-Dwelling Mountain Sheep in California

Abstract:  Metapopulations may be very sensitive to global climate change, particularly if temperature and precipitation change rapidly. We present an analysis of the role of climate and other factors in determining metapopulation structure based on presence and absence data. We compared existing and historical population distributions of desert bighorn sheep ( Ovis canadensis ) to determine whether regional climate patterns were correlated with local extinction. To examine all mountain ranges known to hold or to have held desert bighorn populations in California and score for variables describing climate, metapopulation dynamics, human impacts, and other environmental factors, we used a geographic information system (GIS) and paper maps. We used logistic regression and hierarchical partitioning to assess the relationship among these variables and the current status of each population (extinct or extant). Parameters related to climate—elevation, precipitation, and presence of dependable springs—were strongly correlated with population persistence in the twentieth century. Populations inhabiting lower, drier mountain ranges were more likely to go extinct. The presence of domestic sheep grazing allotments was negatively correlated with population persistence. We used conditional extinction probabilities generated by the logistic-regression model to rank native, naturally recolonized, and reintroduced populations by vulnerability to extinction under several climate-change scenarios. Thus risk of extinction in metapopulations can be evaluated for global-climate-change scenarios even when few demographic data are available.