Study of microelement composition of Lake Ladoga freshwater mollusks' shells with use LA-ICP-MS method
The information about the chemical composition of the shells of the mollusks of Lake Ladoga is scarce and is known mainly for heavy metals. Obtaining new data on it with use of modern precise methods of analysis of the shells' substance and the extension of the investigated elements number is very important. In our study we investigated a broad range of trace elements (34 elements) contained in the shells of bivalves of Lake Ladoga Anadonta cygnea and Unio pictorum, with the aim to establish patterns of trace elements accumulation in the shells of freshwater mollusks. We used the method of mass spectrometry with inductively coupled plasma with use of laser ablation (LA-ICP-MS). The results showed the specificity of the composition of shells: the high content of strontium, barium and manganese, which are capable isomorphically replace calcium in calcite and aragonite of shells; the difference from carbonate rocks; low correlation of most of the elements with the chemistry of the bottom grounds in which the mollusks Live; Lack of heavy metals bioconcentration (except copper and nicket) in relation to grounds. However, the difference in pollution Levels in different parts of the Lake affects the chemistry of Ladoga Bivalvias, which allows their use in bioindication purposes. The differences in accumulation of some trace elements depend on the species of mollusk. At, Sr, Mn, Ba, Zn, Sn and Sb concentrations were higher in Anadonta cygnea compared to Unio pictorum, whereas for Zr, TL, and La. It has been established that for Sr, Ba and most part of heavy metaLs, except Ni, there is a decrease in concentration in the shells with age in mollusks. For most elements, the highest concentration observed for the inner Layer - hypostracum. A smaLL group of substances has a high concentration in the outer Layer - periostracum. The data obtained give an idea about the biochemistry of the mollusk fauna of Lake Ladoga, factors influencing it and indicate the perspectivity of using LA-ICP-MS for analysis of the shells chemical composition.