三峡库区水体中可溶性C、N变化及影响因素

为了解三峡库区水体中可溶性C、N的变化,本研究于2011年3月至2012年8月在三峡水库涪陵段进行了每周一次的水样采集,分析其中可溶性C、N成分的变化及其来源特征.结果表明,库区水中DOC浓度范围为0.64~9.07 mg·L~(-1),且有明显的季节变化,表现为:夏季春季、秋季冬季,DOC年入库总量为1.78×109kg,入库量具有与浓度相似的季节变化趋势;DTN的浓度范围为2.59~4.35 mg·L~(-1),春季冬季夏季秋季,年入库总量为1.32×109kg,入库量的季节变化特征:夏季秋季春季冬季,其中DON、NO-3-N分别占DTN的30.35%~63.45%、35.87%~67.72%.DOC受降水和温度的影响明显,水中DOC主要来自外源输入,春季、夏季降雨径流其外源输入量增加,而秋季、冬季则内源贡献有所增加;DTN受人为排放和水体稀释的影响相对较大.相关分析表明,DOC与DON呈显著负相关(P0.05),通常以DOC/DON比值反映水中DOM的来源,库区DOC/DON范围为0.35~7.28,DOM来源具有明显的季节特征.夏季DOC/DON较高,DOM主要来自流域侵蚀;冬季DOC/DON较低,DOM主要来自生活污水排放和内源现场产生;春季、秋季DOC/DON介于两者之间,DOM来源包括流域侵蚀、生活污水排放及现场产生等.     

Tissue S/N ratios and stable isotopes (δS and δN) of epilithic mosses (Haplocladium microphyllum) for showing air pollution in urban cities in Southern China

In urban cities in Southern China, the tissue S/N ratios of epilithic mosses (Haplocladium microphyllum), varied widely from 0.11 to 0.19, are strongly related to some atmospheric chemical parameters (e.g. rainwater SO₄²⁻/NH₄⁺ ratios, each people SO₂ emission). If tissue S/N ratios in the healthy moss species tend to maintain a constant ratio of 0.15 in unpolluted area, our study cities can be divided into two classes: class I (S/N > 0.15, S excess) and class II (S/N < 0.15, N excess), possibly indicative of stronger industrial activity and higher density of population, respectively. Mosses in all these cities obtained S and N from rainwater at a similar ratio. Sulphur and N isotope ratios in mosses are found significantly linearly correlated with local coal δ³⁴S and NH₄⁺-N wet deposition, respectively, indicating that local coal and animal NH₃ are the major atmospheric S and N sources.     

Association of plutonium with sediments from the Ob and Yenisey Rivers and Estuaries

The present study applied sequential extraction techniques to investigate the binding and mobility of plutonium (Pu) in sediments from the rivers and estuaries of the Ob and Yenisey. As a study site, the Ob and Yenisey are particularly interesting as both rivers have weapons-grade Pu sources in their catchment areas, including the Russian Pu production and reprocessing plants at Mayak, Tomsk-7 and Krashnoyarsk, and the Semipalantinsk nuclear weapons testing site in Kazakhstan. Plutonium activity and ²⁴⁰Pu/²³⁹Pu ratios were determined using accelerator mass spectrometry (AMS). Sequential extractions showed that between 47 and 80% of the Pu in Yenisey River sediments and 35–53% of the Pu in soils around the Techa River are mobilized with weak oxidising agents, which can indicate that Pu is bound to organic material. In contrast, Pu in Ob and Yenisey Estuarine sediments was more strongly bound, with 60–100% being found in the HNO₃-extractable fraction. This change in speciation could reflect either that Pu bound to organic material in the Techa and Yenisey River sediments becomes more fixed to the sediments with time, or that organic-bound Pu is mobilized and released to the water when the sediments encounter the more saline water of the Ob and Yenisey estuaries. In general, ²⁴⁰Pu/²³⁹Pu ratios were relatively consistent between different extraction fractions, although, in whole sediments, an increase in ratio was observed with distance from the source. This reflects the increased influence of weapon fallout from catchment runoff within the river systems, as compared to the weapons-grade sources close to the production and reprocessing plants. Knowledge of Pu speciation in the Ob and Yenisey Rivers, and the processes controlling its behaviour in estuarine systems, can improve predictions of its transfer and subsequent environmental impact to Arctic Seas.     

Testing hypotheses on shape and distribution of ecological response curves

Niche theory with hypotheses on shape and distribution of ecological response curves is used in the studies of resource sharing of competing plant species. Predictions based on theory should be applicable when, e.g., effects of competing species on the ecological tolerances are assessed or species’ diversity along a resource gradient is evaluated. We studied the ecological response curves of competing plant species along a resource gradient in boreal forests. The study was based on nation-wide soil and vegetation data collected from 455 sample plots on boreal forests in Finland. Species response curves along a soil fertility gradient (in terms of C/N ratio) were estimated using generalized additive models. Distribution of species optima and the relationship of niche width and skewness to the location of the optimum were analyzed with new bootstrap tests. The developed tests can account for the effects of truncation observed in the response curves of several species and for the uneven distribution of observations on the gradient.The estimated response curves of the major field layer species of boreal forests were not evenly distributed along soil C/N gradient. The density of optima peaked with relatively high nitrogen availability. Species with optima at low nitrogen availability had relatively broad realized niches. Niche width was negatively correlated with the density of optima. Species optima were packed and niches were narrow at high resource levels. This result suggests that a greater number of more specialized species can occur and interspecific competition decreases niche widths at high resource levels. Species were packed in the gradient where the C/N ratio was lower than 25, i.e., in conditions where nitrification can take place. This indicates that the majority of the vascular plants of boreal forests are favoured by the availability of NO₃⁻. Those few species thriving at high C/N ratios have broader realized niches.     

新型玻纤／P84复合针刺毡的开发及应用

阐述了玻纤／P84复合毡过滤材料的研制过程、技术方法、使用效果及其应用。玻纤／P84复合针刺毡既要满足高性能、低成本的生产要求，还要适应不断提高的环保要求及复杂工况的要求。     

C/N比和曝气量影响MBR同步硝化反硝化的研究

通过连续运行MBR研究了C/N比和曝气量对同步硝化反硝化的影响，结果表明，在环境温度13～23℃，MLSS为6.0～6.8 g/L，进水NH⁺₄-N浓度50 mg/L，曝气量0.5 m³/h，HRT为6 h实验条件下，总氮去除率随着进水C/N比的增加而增加，在C/N比为6∶1～8∶1时，TN去除率达到79%～89%，低的C/N比抑制反硝化，过高的C/N比增加了碳源补加的成本。改变反应曝气量，当C/N比为6∶1，曝气量为0.4 m³/h时，TN的去除率达到了最大值85%。曝气量过高或过低，TN去除率均下降。并对在不同曝气量下MBR 内的DO 值分布进行了初步研究。     

Effects of deltamethrin on hepatic microsomal cytochrome p450‐dependent monooxygenases in carp

Abstract The in vivo effects of sublethal concentrations of deltamethrin (DM), a pyrethroid insecticide, on the hepatic microsomal cytochrome P450 (Cyt P450) content and the Cyt P450‐dependent monooxygenase activities (para‐nitrophenetole‐O‐deethylase, pNPOD; aminopyrene‐N‐demethylase, APND; ethylmorphine‐N‐demethylase, EMND; 7‐ethoxycoumarin‐O‐deethylase, ECOD; and ethoxyresorufin‐O‐deethylase, EROD) were examined in adult carp (Cyprinus carpió L.).

0.2 μg/1 DM treatment resulted in significant increases in APND, EMND and ECOD activities, whereas 2 μg/1 DM resulted in significant inhibitions of all studied isoenzyme activities with the exceptions of pNPOD and APND after 72 h. EROD was the only enzyme for which a slight increase in activity was observed. On repeated treatment, Cyt P450 could not be detected after 48 h, but the Cyt P420 level increased. All tested isoenzyme activities were inhibited, with the exception ofthat of EROD, which was enhanced.

All these changes in enzyme activities and Cyt P450 content demonstrate the effects of DM on fish. DM treatment at low concentration is presumed to cause induction of the Cyt P450‐dependent monooxygenases which may lead to faster metabolization of the insecticide. In contrast, DM at higher concentration strongly inhibited the activities of the studied enzymes. This finding may be due to the damaging effect of DM on the xenobiotic metabolizing enzyme systems offish.     

Genotoxicity of chromium in vitro on yeast: Interaction with DNA†

The genotoxicity of chromium chloride was investigated in cells of D₇ strain of Saccharomyces cerevisiae harvested either from logarithmic or stationary growth phase.

A weak induction of mifotic gene conversion and point reverse mutation was obtained when the incubations were performed using phosphate buffer. No genetic effect was observed when the incubations were performed using Tris‐HCl buffer.

The experiments with ⁵¹Cr radiotracer demonstrated that Cr³⁺ ion enters the yeast cells and binds to DNA even if the incubation mixture was performed with Tris HCl buffer. This behaviour could be due to the highest concentration of CrCl₃ that cause some damages to cytoplasmatic membrane.     

Rain‐washing of foliar deposits of Dimilin®WP‐25 formulated in four different carrier liquids

Abstract

Dimilin^® WP‐25, a wettable powder formulation of diflubenzuron (DFB) [1‐(4‐chlorophenyl)‐3‐(2,6‐difluorobenzoyl) urea], was formulated in four different carrier liquids, viz., water; a light petroleum paraffinic oil, ID 585; a heavy paraffinic oil, Sunspray^® 7N; and a 1:2 mixture of a light petroleum aromatic solvent (Cyclosol^® 63) and canola oil; to provide four end‐use mixtures, Dim‐W, Dim‐585, Dim‐7N and Dim‐Cy‐C respectively, each containing 28 g of DFB per litre. Balsam fir branch tips clipped from greenhouse‐grown seedlings, and sugar maple branch tips clipped from field‐grown young trees, were exposed to uniform‐sized droplets (ranging in diameters from 135 to 190 μm) of the four end‐use mixtures which were atomized using a monodispersed droplet generator. Droplets were collected on the fir and maple branch tips and the initial residue per g fresh weight of foliage was determined by high‐performance liquid chromatography (HPLC). The branch tips were exposed to cumulative rainfall of 3, 6 and 10 mm at an intensity of 5 mm/h and at time intervals of 1, 12, 36 and 72 h after DFB treatment, to test the influence of ‘ageing’ of foliar residues on rainfastness. Foliar samples were collected for residue determination just before the onset of rainfall, and at 0.5 h post‐rain. DFB was quantified by the HPLC method. In the case of fir foliage, the Dim‐W formulation was the most susceptible to rain‐washing and the rainfastness did not increase with the ageing period of foliar deposits. In contrast, the three oil‐based mixtures showed greater rainfastness depending upon the carrier liquid and the ageing period. Rainfastness decreased in the order of Dim‐Cy‐C > Dim‐7N > Dim‐585 > Dim‐W. In contrast, the data on maple foliage indicated that the ageing of deposits increased the rainfastness of all the 4 end‐use mixtures. Dim‐585 was the most susceptible to rain washing, and rainfastness decreased in the order of Dim‐W > Dim‐Cy‐C > Dim‐7N > Dim‐585.     

The evolution of the Canadian mining industry: The role of regulatory punctuation

In this study, we analyze the evolution of Canada's mining industry from 1929 to 2006, focussing on the determinants of the number of firms in the industry and why this number changed over that period. Most empirical studies of industry evolution have focused on manufacturing industries that share similar structural characteristics. Perhaps because of this, extant models of industry evolution tend to ignore industry-specific and national-specific factors that can cause atypical trajectories, that is, heterogeneous industry evolution. Initial inspection of the Canadian mining industry shows that it is atypical in that it exhibits “negative skew” over time in the number of firms rather than the typical “positive skew.” We review two dominant theoretical approaches to industry evolution: the density-dependence theory and variants of industrial organization economics. We also consider possible sources of industry evolution heterogeneity, focussing particularly on “regulatory punctuation”. Using Canadian mining data, we find that the traditional models do not fully explain the changes in population size in Canada's mining industry. As a result, we introduce a number of hybrid models. The results from these hybrid models suggest that Canadian-specific regulatory punctuations, particularly the introduction of significant new taxes, environmental legislation, and incentives have shaped the trajectory of mining firm participation.