三峡库区汛期极端降水非均匀性特征

利用极端降水量集中度和集中期讨论三峡库区汛期极端降水量的非均匀性分布特征。结果表明: 三峡库区极端降水量空间分布表现为西南部和东北部地区相对较少,中部、东南部相对较多。库区汛期极端降水集中度和集中期的空间差异不大,集中程度总体较差,东北部和西部地区极端降水相对集中,中部相对分散。库区极端降水主要集中在6月底和7月上中旬,东北部和西部偏西地区集中期相对较晚,中部地区集中期相对较早。库区汛期极端降水量的分配状况与同期极端降水量存在较好的关系,即极端降水量越少,则极端降水量越集中、集中期越早;反之极端降水量越多,则极端降水量越分散、集中期越晚,尤其是在库区东北部地区最为显著。三峡库区蓄水后极端降水集中程度在空间上一致性较好,表现为蓄水后更为分散;极端降水量和集中期则在空间上差异显著,大致表现为蓄水后东北部极端降水增加并延迟;西南部极端降水减少并提前     

三峡工程蓄水运用期库区干流水质分析

分析了三峡库区蓄水前后（1998～2009年）干流水质的变化及原因。结果表明,同蓄水前相比,蓄水后库区干流水质变好,库区干流断面月度达标率均值由蓄水前的623%变为蓄水后的783%,库区干流超标污染物主要为高锰酸盐指数、总磷、铅等。蓄水后水质时空分布出现新的特点,近坝水体悬浮物、浑样高锰酸盐指数、总磷、铅等可吸附污染物浓度显著降低。蓄水后年内悬浮物及浑样高锰酸盐指数、总磷和铅浓度仍然是丰水期＞平、枯水期,但近坝水体不同水期间浓度差别比蓄水前明显减小。蓄水后,库区干流浑样高锰酸盐指数、总磷、铅浓度整体上表现为从库尾至库首沿程下降,尤以丰水期沿程下降最为突出。浑样高锰酸盐指数、总磷、铅浓度以上变化特征主要缘于库区水位抬高后,流速减小导致的澄清作用,即高锰酸盐指数所代表污染物、磷、铅等随泥沙发生了不同程度的沉降。蓄水前后清样高锰酸盐指数和总磷未发生明显变化,156 m蓄水后至今,清样铅浓度明显低于蓄水前。     

上海城市样带土壤有机碳空间变异性研究

为揭示城市化、工业化等人为活动对土壤有机碳的影响,选择能反映上海城郊乡梯度差异的城市样带,采用地统计学方法对表层土壤样品土壤有机碳的空间变异结构和分布格局进行了分析。结果表明：城市表层土壤有机碳含量均属中等变异,徐汇区土壤有机碳含量呈正态分布,奉贤区、闵行区和所研究样带土壤有机碳含量呈对数正态分布。半方差函数模型拟合结果显示徐汇和闵行区土壤有机碳符合指数模型,奉贤和所研究样带土壤有机碳符合球状模型。通过泛克里格插值得到城市表层土壤有机碳含量空间分布图,发现徐汇、闵行区土壤有机碳呈岛状,奉贤区呈条带状,而所研究样带呈条带和岛状分布相结合的特点。土壤有机碳含量城郊乡梯度差异明显,工业化、城市化、肥料投入与管理等人为因素对城市土壤有机碳空间分布密切相关     

长江干流不同江段鱼卵及仔鱼漂流特征昼夜变化的初步分析

根据2007~2009年在长江干流的泸州、珞璜、宜都、武穴4个江段分别采集的数据,对这些江段鱼卵及仔鱼漂流特征的昼夜变化规律进行初步分析。结果显示,长江上游泸州江段和珞璜江段鱼卵及仔鱼昼夜漂流密度有一定差异,但不显著;长江中游宜都江段,鱼卵漂流密度在昼夜时间上有显著性差异（〖WTBX〗n=38,p〖WTBZ〗=000）,表现为6〖DK〗∶00的平均漂流密度13.02 ind./100 m3明显大于18〖DK〗∶00的密度3.28 ind./100 m3,仔鱼夜间漂流密度明显大于白天,于22〖DK〗∶00达到高峰值;武穴江段仔鱼漂流密度在昼夜时间上有显著性差异（〖WTBX〗n=62,p〖WTBZ〗=000）,8〖DK〗∶00的平均漂流密8621 ind./100 m3明显大于18〖DK〗∶00的密度4485 ind./100 m3。不同物种的鱼卵及仔鱼漂流密度亦呈现出一定的昼夜差异,宜都江段贝氏〖FK（W*5/5。1〗〖PS黎明政造字2.EPS;%84%84,BP〗〖FK)〗,草鱼和银鲴鱼卵主要分布在白天,鳙、鲢等种类分布在夜间;另外,鳙、银鮈、铜鱼和翘嘴鲌等多数种类的仔鱼仅在夜间有分布,而飘鱼属的种类主要分布在白天。通过采集到鱼卵发育期推算,四大家鱼、贝氏〖FK（W*5/5。1〗〖PS黎明政造字2.EPS;%84%84,BP〗〖FK)〗、银鲴和翘嘴鲌的繁殖时间主要集中在夜间,而花斑副沙鳅和鳊全天均有繁殖     

2008年低温雨雪冰冻对武汉城市公共交通的影响评估

为了对2008年低温雨雪期间气象条件对城市交通运输的影响给出定量评估,运用天气分析及统计学方法,分析了低温雨雪冰冻期间武汉市主要气候特征,利用2008年初持续低温雨雪期间武汉城市公共交通线路（包括公交车、轮渡、汽渡）逐日停运数据,定义了持续低温雨雪冰冻过程城市公共交通影响度,通过统计分析,找到了关键气象因子、关键期和低温临界指标,建立了气象评估模型。结果表明：在持续低温雨雪冰冻过程中,初发时期是公共交通影响的关键时期之一,影响度与积雪深度关系最密切,在公交车、轮渡、汽渡3种交通工具中,公交车影响度与气象要素的相关最密切,对武汉城市公交车造成明显影响的临界气温是17℃。该结论在实际的气象灾害评估业务工作中进行了运用,效果良好     

Inside-sediment partitioning of PAH, PCB and organochlorine compounds and inferences on sampling and normalization methods

Comparability of sediment analyses for semivolatile organic substances is still low. Neither screening of the sediments nor organic-carbon based normalization is sufficient to obtain comparable results. We are showing the interdependency of grain-size effects with inside-sediment organic-matter distribution for PAH, PCB and organochlorine compounds. Surface sediment samples collected by Van-Veen grab were sieved and analyzed for 16 PAH, 6 PCB and 18 organochlorine pesticides (OCP) as well as organic-matter content. Since bulk concentrations are influenced by grain-size effects themselves, we used a novel normalization method based on the sum of concentrations in the separate grain-size fractions of the sediments. By calculating relative normalized concentrations, it was possible to clearly show underlying mechanisms throughout a heterogeneous set of samples. Furthermore, we were able to show that, for comparability, screening at <125 μm is best suited and can be further improved by additional organic-carbon normalization.     

Nitrogen deposition effects on Mediterranean-type ecosystems: an ecological assessment

We review the ecological consequences of N deposition on the five Mediterranean regions of the world. Seasonality of precipitation and fires regulate the N cycle in these water-limited ecosystems, where dry N deposition dominates. Nitrogen accumulation in soils and on plant surfaces results in peaks of availability with the first winter rains. Decoupling between N flushes and plant demand promotes losses via leaching and gas emissions. Differences in P availability may control the response to N inputs and susceptibility to exotic plant invasion. Invasive grasses accumulate as fuel during the dry season, altering fire regimes. California and the Mediterranean Basin are the most threatened by N deposition; however, there is limited evidence for N deposition impacts outside of California. Consequently, more research is needed to determine critical loads for each region and vegetation type based on the most sensitive elements, such as changes in lichen species composition and N cycling.     

Combustion-derived substances in deep basins of Puget Sound: historical inputs from fossil fuel and biomass combustion

Reconstructions of 250 years historical inputs of two distinct types of black carbon (soot/graphitic black carbon (GBC) and char-BC) were conducted on sediment cores from two basins of the Puget Sound, WA. Signatures of polycyclic aromatic hydrocarbons (PAHs) were also used to support the historical reconstructions of BC to this system. Down-core maxima in GBC and combustion-derived PAHs occurred in the 1940s in the cores from the Puget Sound Main Basin, whereas in Hood Canal such peak was observed in the 1970s, showing basin-specific differences in inputs of combustion byproducts. This system showed relatively higher inputs from softwood combustion than the northeastern U.S. The historical variations in char-BC concentrations were consistent with shifts in climate indices, suggesting an influence of climate oscillations on wildfire events. Environmental loading of combustion byproducts thus appears as a complex function of urbanization, fuel usage, combustion technology, environmental policies, and climate conditions.     

Is the reproduction of Donax trunculus affected by their sites of origin contrasted by their level of contamination?

The reproductive cycle of bivalves is regulated by several natural environmental factors but exposure to chemical pollutants can also interfere and may result in advanced or delayed spawning season. To our knowledge, the gametogenic cycle of the suspension-feeder bivalve Donax trunculus has not yet been used as biomonitoring tool in ecotoxicological surveys. The aim of this study was to examine over a year physiological reproductive endpoints (sex-ratio, gametogenic and energy reserve cycles) and biological indices (condition index, allometry) in D. trunculus originating from two sites differing by their level of contamination. Specimens were collected bimonthly from November 2008 to October 2009 from a polluted site (Radès Méliane) and a comparatively reference site (Sidi Jehmi) in the Gulf of Tunis (Tunisia). Five stages were depicted by histological examination of gonads: undifferentiated, developing, mature, spawn and spent. Differences in the gametogenic cycle according to the site of origin of bivalves were observed. The spawning period began in March and was maximum in May in bivalves from both sites, but the percentage of spawning animals was higher in the polluted site vs the reference site. The spawning period was shorter in animals from the polluted site comparatively to the reference site. Energy reserves (glycogen, lipids) were higher in March and May comparatively to the other studied periods in bivalves from both sites. Lower energy reserves levels were usually observed in animals from the polluted site compared to the reference site. Seasonal variations of the condition index were associated to the reproductive and nutritive status of bivalves. Differences in allometry were depicted between bivalves from both studied sites. If we try to link allometry, energy reserves and reproduction, it can be hypothesized that for bivalves from the reference site, energy reserves are allocated to gametogenesis and length growth. For bivalves from the polluted site, energy reserves could be devoted to tolerance to chemical stress and to reproductive processes. Therefore, D. trunculus appears as a suitable sentinel species for the assessment of the ecotoxicological risk of contaminants such as endocrine disruptors.     

Modifications of black carbons and their influence on pyrene sorption

Sorption of pyrene on black carbons (BCs) obtained by heating sawdust at two temperatures (400 and 700 °C, denoted as 400BC and 700BC, respectively), as well as on modified BCs (via oxidation, oximation, and hydrolysis) was studied to investigate the role of BC structural characteristics in sorption of hydrophobic organic compounds. Pyrene was bound strongly by 700BC and 400BC, with organic carbon normalized distribution coefficients (K_oc) of 10^5.04-10^5.86 and 10^4.65-10^5.16, respectively, at equilibrium pyrene concentrations of 10-100 μg L⁻¹. Both chemical composition and pore distribution of the two BCs changed after modifications, which led to changes in their sorption characteristics for pyrene. After modifications, the linearity of pyrene sorption isotherm increased for 700BC but decreased for 400BC. For 700BC, both oxidation and oximation reduced pyrene sorption, with K_oc decreasing by 69.1-73.7% and 18.7-33.9%, respectively, whereas hydrolysis did not exert a significant influence. For 400BC, oxidation and hydrolysis reduced K_oc by 2.28-25.9% and 29.2-33.9%, respectively, while oximation increased K_oc. In most cases, the change in sorption capacity could be explained by the changes in C content and type, polarity, surface area, and micropore volume of the BCs; however, the role of conformation (the accessibility to sorption sites) could not be ignored.