Evaluation of Temperature Trend In Contaminated Tidal Flat In The Ariake Sea, Japan

Abstract

Thermal environment of the tidal flat is one of the major parts of the contaminated geo-environment of the Ariake Sea. The activities of marine ecosystem in tidal flats depend strongly on the thermal environment. In order to get a clear idea about the thermal environment of the tidal flats of the Ariake Sea, two study areas, Iida and Higashiyoka tidal flats were selected. By installing five nos. of thermocouple (Tokyo Sokki co., Model no.: N004853) at different specified depths ( 0.10 m,0.20 m,0.50 m,1.0 m and 2.0 m) connected with data logger (TDS-530) were used to observe diurnal variation of temperature during the 1^st April to 8^th April, 2006 at Higashiyoka tidal flat. The measured temperature was stored automatically at 1 h interval in the data logger. To observe seasonal variation of temperature in different depths , temperature was measured by inserting the thermocouple at 0.10 m depths interval in the last week of every month at both study areas in the Ariake sea tidal flat. The diurnal temperature variation was more visible near the surface (0.10 m and 0.20 m) indicating the influence of solar radiation in that portion, however in the deeper region (1.0 m and 2.0 m depth) the temperature was dominated by thermal properties of the mud. From seasonal variation of temperature it was seen that during spring and summer heat was transferred from subsurface to the deeper area but during winter and autumn opposite phenomenon was observed. A correlation is proposed to get the temperature profile in the tidal flat in different seasons.