Determination of chlorinated solvents in industrial water and wastewater by DAI–GC–ECD

A very simple and quick analytical method, based on direct aqueous injection, for determination of halogenated solvents in refinery water and wastewater, is described. There is a need to determine halogenated solvents in refinery water streams, because they may originate from several processes. There is also a need to develop methods enabling VOX to be determined in samples containing oil fractions. The method described enables simultaneous determination of 26 compounds with low detection limits (sub-μg L−1) and excellent precision, especially for highly halogenated solvents. The matrix effects of four types of sample were evaluated—the method seemed to be relatively insensitive to variations in matrix composition. Deuterated 1,2-dichloroethane was used as internal standard and surrogate compound in quantitative analysis; application of isotopically labelled compounds is rarely reported when non-mass spectrometric detectors are used for analysis. Analysis of real samples showed that the most frequently detected compounds were dichloromethane and 1,2-dichloroethane

Analysing chromatographic data using data mining to monitor petroleum content in water

Chromatography is an important analytical technique that has widespread use in environmental applications. A typical application is the monitoring of water samples to determine if they contain petroleum. These tests are mandated in many countries to enable environmental agencies to determine if tanks used to store petrol are leaking into local water systems. Chromatographic techniques, typically using gas or liquid chromatography coupled with mass spectrometry, allow an analyst to detect a vast array of compounds—potentially in the order of thousands. Accurate analysis relies heavily on the skills of a limited pool of experienced analysts utilising semi-automatic techniques to analyse these datasets—making the outcomes subjective. The focus of current laboratory data analysis systems has been on refinements of existing approaches. The work described here represents a paradigm shift achieved through applying data mining techniques to tackle the problem. These techniques are compelling because the efficacy of preprocessing methods, which are essential in this application area, can be objectively evaluated. This paper presents preliminary results using a data mining framework to predict the concentrations of petroleum compounds in water samples. Experiments demonstrate that the framework can be used to produce models of sufficient accuracy—measured in terms of root2 Geoffrey Holmes, Dale Fletcher, Peter Reutemann and Eibe Frank mean squared error and correlation coefficients—to offer the potential for significantly reducing the time spent by analysts on this task

Responses of two Mediterranean seagrasses to experimental changes in salinity

The aim of this study is to examine the effects of variations in salinity levels on growth and survival of two fast-growing Mediterranean seagrasses, Cymodocea nodosa and Zostera noltii. We also tested the capacity of C. nodosa to acclimate to a gradual increase in salinity and to discover how it responds to a sharp rise in salinity in combination with other factors, such as increases in temperature, seasonality and different plant-population origins. Several short-term (10 days) experiments were conducted under controlled conditions. For each experiment, ten marked shoots were placed in 5-l aquaria, where they were exposed to different salinity treatments (ranging from 2 to 72 psu). Growth and survival of both species were significantly affected by salinity. A significant effect between salinity and temperature on the shoot growth rate of C. nodosa was also detected, but not on shoot mortality. When C. nodosa plants were acclimated by gradually increasing the salinity level, it was observed that acclimatisation improved tolerance to salinity changes. A different response to salinity variations, depending on the origin of the plants or the season of the year, was also detected. These results indicated that Z. noltii plants tolerate conditions of hyposalinity better than C. nodosa, and that the tolerance range of C. nodosa may change depending on the temperature, the season or the population.This research was financed by an ACUAMED contract and by an FPI grant (FPI 01 A 002) from the Generalitat Valenciana