The study of biologically active compounds and gross β-radioactivity of some vegetables and medicinal plants in conditions of outdoor hydroponic systems and soil culture in Ararat Valley

Abstract

Background: It is known that various natural (40K, 234Th, 231Th, etc.) and technogenic (90Sr, 89Sr, 137Cs, 134Cs, etc.) radionuclides (RN) may enter into the biosphere during the operation of nuclear power plants (NPP). Moving along the transfer chains of irrigation water – soil - plant and hydroponic nutrient solution – substrate - plant, the RN may penetrate human organisms and potentially cause various dangerous diseases. Thus, monitoring the gross β-radioactivity of plant materials (such as vegetables, medicinal plants, fruits, etc.) and ensuring the production of radioecologically safe plant raw materials is a contemporary challenge.Since 1996, we have been conducting radiomonitoring studies in Ararat Valley in the water-soil-plant ecosystem of the zones within the 2-15, 20, and 30 km radius of Armenian NPP (ANPP) technogenic influence. Objective: To reveal the optimal conditions for radio-ecologically safe plant raw material, we compared the gross β-radioactivity of the edible parts of several valuable vegetables (rhubarb - Rheum undulatum L., Chinese cabbage - Brassica rapa subsp. Chinensis, kale - Brassica oleracea var. Sabellica L., spicy pepper - Capsicum frutescens L., (varieties - “Bishops crown”, “Cayenne”, “Chili De arbol”, “Little Elf”, ”Fresno”), cicer - Cicer arietinum L., (varieties - “Kapuli” introduced from the USA, “Desi” introduced from Canada and “Leningradskaya 313” introduced from Russia)) as well as the plant raw materials of medicinal plants (ashwagandha - Withania somnifera L., Moroccan mint - Mentha spicatavar. Crispa, Marokko, Japanese pagoda tree - Sophora japonica L., holy basil - Ocimum tenuiflorum L., and rosemary - Rosmarinus officinalis L.). These plants were introduced into Armenia and grown under various outdoor hydroponic systems (organic, NFT, water stream, drip, and classical hydroponics) and in soil.hydroponics) and soil. The studies were done at the Institute of Hydroponics Problems (IHP) in Ararat Valley (a zone of ANPP with a 30 km radius). It has concrete practical significance since it allows radio-ecologically safe plant raw material to be received. Methods: The gross β-radioactivity of the plant samples was determined using a small background UMF-1500 radiometer. Results: The results of the radiochemical study have shown that in the same zone of radio voltage and climatic conditions of Ararat Valley, several varieties of crops cultivated in hydroponic and soil conditions have accumulated different amounts of β-emitting technogenic and natural RN. The gross β-radioactivity of vegetables fluctuated between 230 - 590 Bq/kg in classic hydroponics and 140 - 480 Bq/kg in soil, and the gross β-radioactivity of medicinal plants was between 320 - 680 Bq/kg in hydroponics and 240 - 450 Bq/kg in soil. In both hydroponic systems andsoil, the gross β-radioactivity of the edible parts of vegetables and medicinal plants follows the same decreasing order: for vegetables, the order is rhubarb > Chinese cabbage > kale > spicy pepper > chickpea; and for medicinal plants, the order is ashwagandha > Moroccan mint > holy basil > Japanese pagoda tree > rosemary. Conclusion: Regardless of the crop varieties and cultivation methods (organic, water stream, drop, classical hydroponics, and soil culture), the plant raw material is considered radio-ecologically safe because their gross β- radioactivity doesn’t exceed the radio-ecological safety threshold stated by the World Health Organization – 1000 Bq/kg. Keywords: vegetables, medicinal herb, radionuclides, nutrient solution, radio-ecological safety