Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

The POC / Th ratio of settling particles isolated using split flow-thin cell fractionation (SPLITT)

The common assumption that the ratio between particulate organic carbon (POC) and particulate ²³⁴Th obtained from shallow sediment traps and filterable particles are representative of the ratio in the total particle settling flux should be treated with caution in view of well-known biases associated with tethered shallow sediment traps and the decoupling between size and settling velocity of many natural particle regimes. To make progress toward reliably constraining the POC / ²³⁴Th ratio on truly settling particles, we have tested here a settling collection technique designed to remove any hydrodynamic bias; split flow-thin cell fractionation (SPLITT). These first results from a North Sea fjord and an open Baltic Sea time-series station indicates that the POC / ²³⁴Th ratio on the more complete particle-settling spectrum, isolated with SPLITT, was higher than the POC / ²³⁴Th ratio obtained simultaneously from tethered shallow sediment traps in seven out of seven parallel deployments with an average factor of 210%. The POC / ²³⁴Th ratio from the SPLITT was either in the same range or higher than that obtained on filtered “bulk” particles. To explain this novel data we hypothesize that the slowest settling fraction is organic-matter rich and does not strongly complex ²³⁴Th (i.e., high POC / ²³⁴Th). We suggest that this ultra-slow sinking fraction is better collected by SPLITT than with tethered sediment traps because of minimized hydrodynamic bias.This was tested using the ratio of POC / Al as a tracer of detrital mineral-ballast influenced settling velocity. The higher POC / Al ratios in SPLITT samples relative to in traps is consistent with the hypothesis that SPLITT is better suited for collecting also the slow-settling component of sinking particles. This important slow-settling component appears to here consist primarily of non-APS/TEP components of plankton exudates or other less-strongly ²³⁴Th-complexing organic matter. Further applications of the SPLITT technique are likely to return increasingly new insights on the composition (including “truly settling” POC / ²³⁴Th) of the total spectrum of particles settling out of the upper ocean.     

基于IGS超级跟踪站的近实时GPS气象研究及应用

目前国内许多城市开始将CORS综合应用网服务于气象部门,为给地基GPS气象研究人员提供一个真实的研究环境,本文基于IGS超级跟踪站网络搭建了一个近实时GPS气象系统,并结合实测数据验证了该系统的有效性。基于该平台可以系统地研究GPS遥感水汽、层析水汽三维分布、数值天气预报同化GPS水汽以及利用电离层分布进行空间天气预报等理论。     

水泥粉煤灰加固有机质土的试验研究

对于高有机质含量的泻湖相软土,单纯采用水泥不能有效提高该软土的力学性能,因此提出了采用水泥和粉煤灰作为固化剂的加固方法。通过不同水泥掺入量、粉煤灰掺入量和龄期下水泥土的无侧限抗压强度试验,分析了水泥粉煤灰固化土的强度规律和变形规律,探讨了水泥和粉煤灰加固高有机质含量软土的机理。结果表明,粉煤灰对于水泥试块的早期强度影响较小,对后期强度影响较大;粉煤灰最佳掺入量为12％,超过此掺入量水泥土强度反而会降低,粉煤灰水泥土的破坏应变、E50也在粉煤灰掺量为12％时分别达到最低值和最大值。水泥掺加粉煤灰可有效地提高高有机质含量软土的强度。     

CDN技术在国土资源信息服务系统中的应用——以资源网为例

国土资源信息服务类网站信息服务覆盖广、浏览量大、易受到黑客和病毒的攻击。本文以资源网为例,主要介绍CDN技术在国土资源信息服务系统中的应用。CDN技术的引入,可以大规模多区域加速,保证用户的就近访问,隐藏源站服务器,对于提高国土资源信息服务类网站的响应速度,提高网站的安全性具有重大的现实意义。     

GPS-RTK联合全站仪的野外数据采集

对于地形测绘和其它环境条件复杂的地区,用常规方法进行数据采集比较困难,传统的测绘方法越来越不能满足测量效率和成本的要求,但采用GPS RTK与全站仪联合作业,使RTK与全站仪优势互补,在保证测量精度的前提下,可大幅度提高测量速度和效率。     

Dynamics and interaction of organic carbon, turbidity and bacteria in a karst aquifer system

The dynamics of organic carbon (OC), turbidity, faecal indicator bacteria and physicochemical parameters was studied in a karst system near Yverdon, Switzerland. Online measurements and sampling were done at a swallow hole draining an agricultural surface (the input), and two groups of springs (the outputs) that often show bacterial contamination. A fluorescent tracer that was injected into the swallow hole during low-flow conditions first arrived at the springs 10–12 days after injection; the total recovery rate was 29%. Previous tracer tests during high-flow conditions gave shorter travel times. After a major rainfall event, a primary turbidity peak was observed at the springs. It coincides with the rising limb of the hydrograph, indicating remobilisation of autochthonous particles from the aquifer. A secondary turbidity peak occurs several days later, suggesting the arrival of allochthonous particles from the swallow hole. Wider peaks of OC and bacteria were observed simultaneously. Applying methods from molecular microbiology (PCR-DGGE) allowed characterisation of the bacterial communities at the swallow hole and the springs. The results demonstrate that the swallow hole is an important source of groundwater contamination, while its contribution to aquifer recharge is insignificant. OC appears to be a better indicator for bacterial contamination than turbidity.     

三种高程传递方法的精度分析

通过试验对悬挂钢尺、GPS测高和全站仪垂直测高三种高程传递方法进行了理论分析与精度比较,并讨论了各种方法在实际应用中的优点与局限性。     

根据Dobson和TOMS资料分析北京和昆明大气臭氧总量变化特征

用约２０年 Ｄｏｂｓｏｎ和ＴＯＭＳ资料来分析北京（３９.９３°Ｎ，１１６.４０°Ｅ）和昆明 （２５.０２°Ｎ，１０２．６８°）两地大气臭氧总量的变化特征，结果表明：（１）在１９７９－２０００年间北京大气臭氧长期变化趋势是－０．６４２ ＤＵ／年，而昆明在１９８０－２０００年间的趋势是－０.００９ ＤＵ／年；（２）北京和昆明两地大气臭氧都有很强的季节内变化（尤其冬季更强），与季节性变化强度相当；（３）在北京和昆明，由记录较短的大气臭氧资料分析得到的长期变化趋势，与较长记录得到的结果有显著差异；（４）在北京（中纬度）和昆明（低纬度）大气臭氧都有显著的准两年振荡信号；（５）两个站点大气臭氧的年际变化主要由长期趋势项和准两年振荡信号组成；（６）Ｄｏｂｓｏｎ仪测量得到的臭氧总量与ＴＯＭＳ资料非常一致。