We would like to invite you to participate in the Analytical Challenge, which is a series of puzzles designed to entertain and challenge our readers. The special ABC feature 'Analytical Challenge' has established itself as a truly unique quiz series, with a new scientific puzzle published every second month. Readers can access the complete collection of published problems with their solutions on the ABC homepage at www.springeronline.com/journal/00216. Test your knowledge and tease your wits in diverse areas of analytical and bioanalytical chemistry by viewing this collection. Quality assurance is the topic of the present challenge. And please note: there is a prize to be won (a Springer book from our catalogue up to a value of euros 75,-). Please read on...

Biosensing Techniques↗

PubMed2004

Information theory for evaluating environmental classification systems.

Environmental pollution data are often ranked in rule-based classification systems. These environmental data are separated in predetermined classes of a classification system for a better and smarter characterization of the state of pollution. Often the measured values are transformed, e.g. in pseudocolor maps, and can then be presented in maps. For some environmental compartments different classification systems for evaluating environmental loadings are used. Because of the dissimilarity of the various classification systems direct visual comparison is difficult. However, by means of information theory an objective comparison of these various classification systems based on their information content enables a decision to be made about which system is the most informative for objective assessment of the state of pollution. By means of the new measure "multiple medium information content" (multiple entropy) objective and simultaneous comparison of all channels (in an environmental classification system: pollutants) of each classification system is now possible. Furthermore the development of the state of pollution over the whole investigation period can be detected by means of information theory. On the basis of the conditions of the established rule-based systems the use of information theory enables definition of new ranges of classes in order to reach the optimum of information during conversion into the environmental classification system.

Journal Article↗

PubMed2004

Chemometrics in analytical chemistry.

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Chemistry, Analytic↗

PubMed2004

Time series analysis of long-term data sets of atmospheric mercury concentrations.

Different aspects and techniques of time series analysis were used to investigate long-term data sets of atmospheric mercury in the Northern Hemisphere. Two perennial time series from different latitudes with different seasonal behaviour were chosen: first, Mace Head on the west coast of Ireland (53 degrees 20'N, 9 degrees 54'W), representing Northern Hemispherical background conditions in Europe with no indications for so-called atmospheric mercury depletion events (AMDEs); and second, Alert, Canada (82 degrees 28'N, 62 degrees 30'W), showing strong AMDEs during Arctic springtime. Possible trends were extracted and forecasts were performed by using seasonal decomposition procedures, autoregressive integrated moving average (ARIMA) methods and exponential smoothing (ES) techniques. The application of time series analysis to environmental data is shown in respect of atmospheric long-term data sets, and selected advantages are discussed. Both time series have not shown any statistically significant temporal trend in the gaseous elemental mercury (GEM) concentrations since 1995, representing low Northern Hemispherical background concentrations of 1.72+/-0.09 ng m(-3) (Mace Head) and 1.55+/-0.18 ng m(-3) (Alert), respectively. The annual forecasts for the GEM concentrations in 2001 at Alert by two different techniques were in good agreement with the measured concentrations for this year.

Journal Article↗

PubMed2003

Measurements of atmospheric mercury species at a coastal site in the Antarctic and over the south Atlantic Ocean during polar summer.

Mercury and many of its compounds behave exceptionally in the environment because of their volatility, capability for methylation, and subsequent biomagnification in contrast with most of the other heavy metals. Long-range atmospheric transport of elemental mercury, its transformation to more toxic methylmercury compounds, the ability of some to undergo photochemical reactions, and their bioaccumulation in the aquatic food chain have made it a subject of global research activities, even in polar regions. The first continuous high-time-resolution measurements of total gaseous mercury in the Antarctic covering a 12-month period were carried out at the German Antarctic research station Neumayer (70 degrees 39' S, 8 degrees 15' W) between January 2000 and February 2001. We recently reported that mercury depletion events (MDEs) occur in the Antarctic after polar sunrise, as was previously shown for Arctic sites. These events (MDEs) end suddenly during Antarctic summer. A possible explanation of this phenomenon is presented in this paper, showing that air masses originating from the sea-ice surface were a necessary prerequisite for the observations of depletion of atmospheric mercury at polar spring. Our extensive measurements at Neumayer of atmospheric mercury species during December 2000-February 2001 show that fast oxidation of gaseous elemental mercury leads to variable Hg0 concentrations during Antarctic summer, accompanied by elevated concentrations, up to more than 300 pg/m3, of reactive gaseous mercury. For the first time in the Southern Hemisphere, atmospheric mercury species measurements were also performed onboard of a research vessel, indicating the existence of homogeneous background concentrations over the south Atlantic Ocean. These new findings contain evidence for an enhanced oxidizing potential of the Antarctic atmosphere over the continent that needs to be considered for the interpretation of dynamic transformations of mercury during summertime.

Air Pollutants↗

PubMed2002

Antarctic springtime depletion of atmospheric mercury.

Unlike other heavy metals that are inherently associated with atmospheric aerosols, mercury in ambient air exists predominantly in the gaseous elemental form. Because of its prolonged atmospheric residence time, elemental mercury vapor is distributed on a global scale. Recently, Canadian researchers have discovered that total gaseous mercury levels in the lower tropospheric boundary layer in the Canadian Arctic are often significantly depleted during the months after polar sunrise. A possible explanation may involve oxidation of elemental mercury, followed by adsorption and deposition of the oxidized form, leading to an increased input of atmospheric mercury into the Arctic ecosystem. Here we present the first continuous high-time-resolution measurements of total gaseous mercury in the Antarctic covering a 12-month period between January 2000 and January 2001 at the German Antarctic research station Neumayer (70 degrees 39' S, 8 degrees 15' W). We report that mercury depletion events also occur in the Antarctic after polar sunrise and compare our measurements with a data setfrom Alert, Nunavut, Canada. We also present indications that BrO radicals and ozone play a key role in the boundary-layer chemistry during springtime mercury depletion events in the Antarctic troposphere.

Adsorption↗

PubMed2002

Small-scale variability of metals in soil and composite sampling.

Soil pollution data is also strongly scattering at small scale. Sampling of composite samples, therefore, is recommended for pollution assessment. Different statistical methods are available to provide information about the accuracy of the sampling process. Autocorrelation and variogram analysis can be applied to investigate spatial relationships. Analysis of variance is a useful method for homogeneity testing. The main source of the total measurement uncertainty is the uncertainty arising from sampling. The sample mass required for analysis can also be estimated using an analysis of variance. The number of increments to be taken for a composite sample can be estimated by means of simple statistical formulae. Analytical results of composite samples obtained from different fusion procedures of increments can be compared by means of multiple mean comparison. The applicability of statistical methods and their advantages are demonstrated for a case study investigating metals in soil at a very small spatial scale. The paper describes important statistical tools for the quantitative assessment of the sampling process. Detailed results clearly depend on the purpose of sampling, the spatial scale of the object under investigation and the specific case study, and have to be determined for each particular case.

Environmental Monitoring↗