ASSESSMENT OF THE TOXICITY OF SUBSTANCE MAX PLEX TO HYDROBIONTS

At present a large-scale oil and gas development work is carried out on the Russian sea shelf. Therefore it is necessary to know toxicity of the preparation MAX PLEX used on drilling platforms as there is a real possibility that its residual quantity could get in the soil posing harm to biological water resources. The preparation toxicity was assessed in accordance with «The Guidelines for determining toxicity of water, bottom deposits, pollutants, drilling fluid Huids using a biotesting method». Toxicity assessment was based on determining mean lethal concentrations EC₅₀ and LC₅₀ characterizing changes in survival (death) of standard sea test-organisms (Phytoplankton Phaedactylum tricornutum Bohin; zooplankton — Aryemia salina, fishes, one-day old fishes- Poecillia reticulate Peters) by 50% for a determined time period — 72, 48 and 96 hours (EC₅₀/72h and LC₅₀/48 and 96 h). Based on toxicity assessment of the preparation for hydrobionts, it was established that the most sensitive test-object is Phaedactylum tricornutum Bohin having EC₅₀/72h= 8.3 mg/l. According to the classification proposed by L.A. Lesnikov and K.K. Vrochinskiy, based on grading of acute toxicity to hydrobionts, the preparation MAX PLEX is classified as moderately toxic (for phytoplankton LC₅₀ is 8.3 mg/l during 72h ).