Technical Note: Could benzalkonium chloride be a suitable alternative to mercuric chloride for preservation of seawater samples?

Instrumental equipment unsuitable or unavailable for fieldwork as well as lack of ship space can necessitate the preservation of seawater samples prior to analysis in a shore-based laboratory. Mercuric chloride (HgCl2) is routinely used for such preservation, but its handling and subsequent disposal incur environmental risks and significant expense. There is therefore a strong motivation to find less hazardous alternatives. Benzalkonium chloride (BAC) has been used previously as microbial inhibitor for freshwater samples. Here, we assess the use of BAC for marine samples prior to the measurement of oxygen-to-argon (O2 / Ar) ratios, as used for the determination of biological net community production. BAC at a concentration of 50 mg dm−3 inhibited microbial activity for at least 3 days in samples tested with chlorophyll a (Chl a) concentrations up to 1 mg m−3. BAC concentrations of 100 and 200 mg dm−3 were no more effective than 50 mg dm−3 . With fewer risks to human health and the environment, and no requirement for expensive waste disposal, BAC could be a viable alternative to HgCl2 for short-term preservation of seawater samples, but is not a replacement for HgCl2 in the case of oxygen triple isotope analysis, which requires storage over weeks to months. In any event, further tests on a case-by-case basis should be undertaken if use of BAC was considered, since its inhibitory activity may depend on concentration and composition of the microbial community

Structure and evolution of planetary nebulae

Imperial Users onl

Choked flow analogy for very low quality two-phase flows Technical report no. 18

Choked flow analogy for very low quality two-phase flows - homogeneous flow and hydraulic jump theoretical models for predicting axial pressure distributio

Cavitation damage characteristics in water and mercury from studies in a cavitating Venturi Technical report no. 17

Cavitating damage characteristics in water and mercury studied in cavitating Ventur

A multimedia tutorial shell with qualitative assessment in biology

The project is developing methods to produce multimedia tutorials relatively quickly and cheaply, using a generic software shell suitable for any subject area. The shell is a version of one produced originally as part of the HEFC-funded TLTP initiative by the Biodiversity Consortium. Tutorials presented in the shell will provide the student with a structured learning experience that will allow their initial knowledge level or their knowledge acquisition and progress to be qualitatively and quantitatively assessed. Where areas of weakness are revealed by the assessment, students will be advised to study particular parts of the tutorial in order to improve their understanding

The UK Digital Marine Atlas Project: An Evolutionary Approach Towards a Marine Information System

In common with many organizations the United Kingdom Natural Environment Research Council (NERC) collects large quantities of spatial data. Within the marine sciences the cataloguing, promotion, and dissemination of information is a major undertaking. In order to assist with, and develop this task, a recent study has looked at the potential use of computerised information systems, ranging from simple digital catalogues to geographic information systems. This paper discusses the characteristics and problems involved in handling and disseminating marine information and outlines the results of trials with a simple demonstrator system based on a digital version of an existing paper-based marine atlas and the development of an operational digital marine atlas system. More recent experiments with a proprietary Geographic Information System (GIS) suggest that current GIS technology can only go so far in providing a solution and that new techniques must be developed for coping with the diverse spatial nature of marine information