Heavy metal contents in plants growing in the Russian Baltic coastal area

Introduction. Prior to use in the production of food additives, ingredients, and biologically active substances, wild plants should be assessed in terms of heavy metal (HM) accumulation. This task is also relevant because wild plants can be consumed by the survived after accidents, disasters, or military operations at sea.

Objective. To assess the HM-related danger of coastal flora in the areas of potential landing of shipwrecked crews in the seas of the Russian Federation.

Materials and methods. The study objects were coastal algae and higher plants growing in the coastal area of the Gulf of Finland. Plant samples were collected in the Bolshoy Beryozovy Island, Hogland Island, and the Kurgalsky Peninsula. Prior to elemental analysis, the samples were dried at 80°C to a constant weight; their dry weight was estimated with an accuracy of 1 mg. The raw mass was estimated based on the dry weight data and the assumption that the water content in native tree leaves comprises 75%, in grass leaves — 85%, and in F. vesiculosus thalli — 70%. The dried material was mineralized by an MS-6 microwave sample preparation system (Volta, Russia). Elemental analysis was performed using an MGA-915M atomic absorption spectrometer. The measurement results were processed using the Statistica software.

Results. The Cu and Pb content in the studied plants was found to range within permissible limits. The permissible level of cadmium was exceeded by 2–4 times in A. ptarmica, C. angustifolium, and U. dioica on the Kurgalsky Peninsula, indicating the risk of food consumption. The minimum values of Mn content (less than 20 mg/kg of dry matter) were typical of two plant species (L. japonicus and Salix sp.) from the Bolshoy Beryozovy Island and A. podagraria from the Kurgalsky Peninsula. The toxic effects of Mn begin to appear when the daily intake exceeds 2 mg/day, while the maximum Mn content in the studied objects was 11.9 mg/kg. The high Zn content was typical of all plants on the Hogland Island, as well as T. repens and A. podagraria from the Kurgalsky Peninsula and Salix sp. and L. japonicas from the Bolshoy Beryozovy Island. The maximum amount of plant material that can be safely consumed was calculated to be approximately 0.17 kg/day of raw leaf mass.

Conclusions. The absence of daily intake limits for essential elements in regulatory documents makes it difficult to assess the severity of consequences of using plant raw materials for food and medicinal purposes and to apply a risk-based approach to assessing food safety. The high degree of danger associated with the use of plants from the Kurgalsky Peninsula (A. ptarmica, C. angustifolium, and U. dioica) is due to a significant excess of Cd limits. The Cu and Pb levels in all the studied plants was below the limits, indicating the absence of danger associated with these elements. The Zn content can be considered safe, since more than 1 kg of raw leaf mass must be consumed daily to meet the daily requirement, which is practically impossible in actual conditions.

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