Sapropel resources of Lake Kubalakh, Yakutsk

Abstract

The article discusses the results of a geological study (search and evaluation) of sapropel deposit in the subsurface area “Lake Kubalakh” (38 km of the Vilyui motorway). The identification of sapropel deposits of the lake includes a complex of various studies, such as geological and hydrogeological description of the object of study, sounding drilling, testing, topographic and geodetic and laboratory work.
Probing manual drilling was carried out from the ice in order to clarify the boundaries of the deposit, to obtain data on the properties, conditions of occurrence, and capacities of deposits. The sounding network of the lake consisted of five cross-sections with a lake area of 34.89 hectares, located in parallel through 180 meters. A picket line is laid across 40 meters. At each picket, the deposits were probed with simultaneous determination of sapropel power, water depth and the nature of the mineral bottom.
The results of the study revealed that zoogenic-algal, mixed-algal and diatom sapropel species are developed in the subsurface area. The thickness of the deposits varies from 0.3 to 2.60 m, averaging 1.66 m. The main sapropel deposit is concentrated at the northern end of the lake. Agrochemical indicators of sapropel deposits: ash content – 38.8, humidity – 80.52, organic matter – 30.85 %; total nitrogen – 0.89, potassium oxide – 0.17, calcium oxide – 4.32, phosphorus oxide – 0.16 % on ABC. The concentration of 9 trace elements-metals, including cadmium, arsenic, mercury, lead is set within the permissible concentrations. Studies on ⁴⁰K, ²²⁶Ra, ²³²Th and ¹³⁷Cs have shown the radiological safety of sapropel deposits of the lake. Bacteriological studies of sapropels have shown the absence of pathogens of salmonellosis, anthrax, anaerobic and pseudomonas microflora, pathogenic proteus, E. coli.
The estimated geological reserves of sapropels amounted to 525.8 thousand m³, the balance reserves of sapropel deposits in category C₁ – 301.2 thousand m³.