Lake Baikal in southern Siberia is the deepest lake in the world – up to 1.6 km deep in places – and has a unique ecosystem. It is also a wonderfully undeveloped area as illustrated in the photograph from when I was there in 2004. Endemic species of sponges are known to inhabit the lake from ancient times. These sponges act as biological filters for the lake water and contribute greatly to silicon circulation in the lake. In recent years a research institute at Irkutsk, the only significant town in the area, has been studying the sponges’ composition and have published a series of articles (1,2,3). Below we delve a little deeper into these studies.
Oxidative stress of Lake Baikal organisms can be caused by pollution with anionic surfactants or heavy metals, although some specific heavy metals are essential for aquatic organisms. The first article (1) describes the use of wavelength dispersive X-ray fluorescence spectrometry to study the sponges at the southern end of the lake. The concentrations in the sponges of 19 elements, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, and Ba, were determined using synthetic calibration standards, prepared by mixing plant certified reference materials and silicon dioxide.
Baikal sponges Lubomirskia baicalensis have also been tested as potential bio-monitors of chemical pollution (2). The elemental composition of sponges, water and substrate samples were collected in two areas of Lake Baikal where the impact of human activities was very different. Lubomirskia baicalensis accumulates predominantly Cu and Cd and, to a lesser extent, Br, Ba, and Zn. The content of Cl, Ca, V, Zn, As, Se, Ba, Cd, and Cu in the sponges collected in the more polluted waters of Listvennichny Bay was significantly higher than in Bolshye Koty Bay. Sponges accumulate mainly Cd, Cu and Br from the substrate, and most of the elements from the water. They demonstrated that the sponges were suitable bioindicators to assess the pollution of Lake Baikal.
Pashkova et al. (3) investigated the applicability of total reflection x-ray fluorescence (TXRF) to determine heavy metals in the sponges. It was shown that TXRF method can be successfully applied to the fast and reliable quantification of Cu, Zn, Fe, and Mn. Acid digestion by HNO 3 /H 2 O 2 mixture proved to be the optimal procedure for the preparation of sponges. It improved sensitivity and eliminate the effects of particle size and specimen heterogeneity compared with suspension preparation. The TXRF results were agreed well when compared with the data obtained by wavelength dispersive x-ray fluorescence spectrometry.
In all the investigations ultrapure water from an ELGA LabWater PURELAB unit was used in sample preparation, to produce standards and to clean equipment. Total reflection x-ray fluorescence is a particularly, sensitive technique measuring low elemental levels in small samples and requires high purity reagents to ensure accuracy.
Dr Paul Whitehead
After a BA in Chemistry at Oxford University, Paul focused his career on industrial applications of chemistry. He was awarded a PhD at Imperial College, London for developing a microwave-induced-plasma detector for gas chromatography. He spent the first half of his career managing the analytical support team at the Johnson Matthey Research/Technology Centre,specialising in the determination of precious metals and characterising applications such as car-exhaust catalysts and fuel cells. Subsequently, as Laboratory Manager in R&D for ELGA LabWater, he has been involved in introducing and developing the latest water purification technologies. He now acts as a consultant for ELGA.
Analyses of unusual ecosystems and those in a state of flux bring extra demands to all aspects of the analysis, requiring increased confidence in the data obtained. The consistent quality of the purified water used is a key feature of such confidence. ELGA has a well- established track record in providing that confidence.