凡纳滨对虾咸淡水养殖系统内细菌群落组成的PCR-DGGE分析

采用PCR(polym erase chain reaction)-DGGE(denaturing grad ient gel electrophoresis)及传统的微生物培养方法对凡纳滨对虾Litopenaeus vannam ei咸淡水养殖系统内各种环境的细菌群落组成进行了比较研究。传统的微生物培养计数表明,从海湾水、养殖池水到对虾粪样,细菌和弧菌的数量表现出依次增加的趋势,粪样及肠壁中弧菌的数量高出外界水环境1—4个数量级。相对于外界水环境,粪样中有很高的芽孢杆菌孢子含量,但是肠壁定植细菌中不存在芽孢杆菌(孢子)。PCR-DGGE及聚类分析结果表明,从海湾沿岸、养殖池、对虾粪便到对虾肠壁,细菌群落的多样性由高到低,无论是在哪种环境,群落的优势种都十分明显,且只有2—4种。来自同一环境各样品间的细菌群落组成非常相似,来自不同环境的样品,其细菌群落组成差别较大。聚类图上各簇的排列顺序反映了样品在取样空间分布上的毗邻次序和它们的相似程度。     

东海围垦滩地强夯作用下孔隙水压力响应试验研究

围垦滩地饱和粉土地基属于软土地基的一种,其含水量高,渗透性差,强夯加固作用使地基土中的孔隙水压力瞬时升高,且短时间内得不到消散,容易出现“橡皮土”。通过现场试验研究了饱和粉土地基在强夯作用下孔隙水压力的响应规律,确定了两遍强夯之间的间歇时间和强夯的影响深度,以便优化强夯参数,正确指导强夯施工。     

密度胁迫对日本囊对虾生长和水环境的影响

为了探讨密度胁迫对日本囊对虾(Marsupenaeus japonicus)生长、存活及水质因子的影响, 作者设置了100尾/m²(DD)、200 尾/m²(GD)、400 尾/m²(GZ)、600 尾/m²(GG)4个养殖密度, 分析了不同养殖密度下日本囊对虾的生长量、存活率、肥满度及水质因子的差异。结果表明, 实验所监测的水质因子均在对虾生长的安全阈值内, 氨态氮、亚硝态氮、总氮和总磷含量表现出随养殖密度增加逐渐升高的趋势; 体长和体质量增长量、存活率与养殖密度呈负相关, 其中存活率处理间均达到极显著水平(P< 0.01), 且当养殖密度高于200尾/m²时存活率迅速降低; 低养殖密度(DD)处理的对虾肥满度与其他处理间差异均达到显著水平(P< 0.01)。因此, 在相似养殖条件下, 日本囊对虾的适宜养殖密度应该不高于200尾/m²。本实验过程中, 各处理间水质因子均在对虾生长的适宜范围内, 说明水质不是造成对虾死亡的主要原因。所以, 推测密度胁迫可能是造成日本囊对虾存活率低的主要原因。     

长江河口青草沙水库最长连续不宜取水天数

为解决上海日益增长的用水需求, 保障淡水资源安全, 需要建设长江河口避咸蓄淡特大型水库。本文应用改进的三维长江河口盐水入侵数值模式, 采用2007和2008年10个水文站盐度资料对模式进行验证, 计算青草沙水库最长不宜取水天数。本文以径流量特枯的1978—1979年作为水文计算年, 考虑三峡工程、南水北调东线工程和沿江引排水对大通实测逐日径流量的修正, 考虑潮汐、风应力和混合等作用。根据2003年地形计算得出青草沙水库的最长连续不宜取水天数为68天, 这个水库设计的重要参数已在水库建设中采用。根据2008年地形计算得出青草沙水库的最长连续不宜取水天数为54天, 已被水库调度采用。2003年至2008年北支上段河势发生了明显变化, 导致北支盐水倒灌减弱, 因此这期间的最长不宜取水天数减少。     

Hydrodynamic effect of the regulation project of Yangtze River deepwater channel downstream of Nanjing

A two-dimensional flow numerical model of the tidal reaches, which total length is more than 700 km, is established from Datong to the Yangtze River estuary. The tidal levels, velocities, diversion ratios and dynamic axes before and after the separate regulation of each reach and combined regulation of all reaches are obtained. The comparative analysis shows that the regulation project of a separate reach basically has no impact on velocity distributions and variations of diversion ratios of upper and lower reaches, the variations of dynamic axes are only within the local scope of the project. The regulation project of a separate reach also has less impact on the water level in the lower adjacent reaches, but will make the water levels in the upper reaches rise. After the implementation of the regulation projects for all reaches, the rise of water level in the upstream reaches will have a cumulative impact.     

Land‐use impacts and water quality targets in the intensive dairying catchment of the Toenepi Stream,New Zealand

Water quality monitoring in Toenepi Stream, New Zealand, started in 1995 in a study of dairy farming influences on lowland stream quality and has continued since then with brief interruptions. Surveys have provided information about changes in farm and soil management practices as they relate to environmental sustainability. Although average water quality in Toenepi Stream has changed little during 1995–2004, there have been some notable improvements. Water clarity measured by black disc has improved from 0.6m to 1.5m, and median ammonia‐N and nitrate‐N concentrations have declined by 70% and 57%, respectively. The frequency and magnitude of extreme concentrations have declined—most notably for nitrogen (N) forms, which also had decreased mean values. Specific yields for suspended solids (SS) and phosphorus (P) forms in 2002–04 were 47–67% of 1995–97 values, mainly because of lower water yields. Reduced specific yields for N forms in 2002–04 (34–37% of 1995–97 yields) were also attributable to lower mean concentrations in stream water. Faecal bacteria concentrations have not abated and are on average 2–3 times recommended guideline values for contact recreation. Fewer dairy farms and an increased proportion irrigating dairyshed effluent to land, rather than discharging it to the stream via two‐pond systems, were likely causes of improvement in water quality. Water quality targets were developed for Toenepi Stream to achieve contact recreation criteria for the Piako River (downstream) and for intrinsic habitat values for Toenepi Stream. A range of mitigation measures has been formulated to meet these targets, but substantial uptake of sustainable farming practices is needed to improve water quality in Toenepi Stream.     

Vulnerability Assessment at Village Level Due to Tides,Surges and Wave Setup

An assessment of cyclone risk and vulnerability at the village level has evolved, which is an important component of the information system for local level development action plans for preparedness and mitigation. Here, a case study for the Nellore district along the east coast of India is considered. Using maximum probable surges along the coast, total water level (TWL) due to the combined effect of surge, tide, and wind wave is computed for the most vulnerable coastal villages of the Nellore district due to any tropical cyclones. The computations suggest that the TWL along the Nellore coast varies from 2 m in the south to 4 m in the north.     

Potential Seismic Risk in Taiwan Strait Region

GPS observation indicates that the Fujian coastal region of China mainland, the region of Taiwan Strait and northern Taiwan island all show a generally homogenous horizontal motion with weak deformation. Historical earthquake record over more than 800 years and modern instrumental data reveal that there is potential seismic risk in and around Taiwan Strait region. After the National Seismic Zoning Map of China (2001) the expected seismic risk in northern part of the Taiwan Strait is lower than that in middle and southern part. The suggested northern route of the Taiwan Strait passage project seems to be relatively save seismically.     

海水中二甲基硫(DMS)的测定方法及其来源的研究

本文综述了目前国内外有关海水中二甲基硫（ＤＭＳ）的测定方法及其来源的研究,指出ＤＭＳＰ是海洋生物降解产生ＤＭＳ的主要来源。     

大亚湾养殖水域沉积物-海水界面营养盐扩散通量

1998年5月10日和11日分别在大亚湾的大鹏澳和澳头养殖水域现场调查,分析了底层海水、上覆水、沉积物间隙水中营养盐的含量和磷的化学形态。结果表明：大亚湾养殖水域NH,HPO和H4SiO4含量从大至小为：间隙水,上覆水,底层海水;NO和NO含量变化不大。估算了沉积物一海水界面营养盐扩散通量,NH,NO,NO,HPO,H4SiO4平均通量分别为302．0,－0．06,－1．82,2．53,47．96μmol·（m2·d）－1。水体和沉积物中磷的主要化学形态分别为DOP（占TP的54％）和无机态（占总态的60％）。大亚湾养殖水域浮游生物生长由磷控制。沉积物间隙水中NO,NO,HPO,H4SiO4的浓度垂直分布变化不大,而NH的浓度垂直分布呈指数下降特征。