Studies on BOD sub(5) and dissolved oxygen in the Kadinamkulam Kayal, Southern Kerala

Abstract

Salient features associated with the variation in the BOD sub(5) and dissolved oxygen concentration in the Kadinamkulam Kayal, Kerala, India based on fortnightly data from two selected stations from October 1987 to September 1988 are discussed. The BOD sub(5) ranged from 5.76 to 24.39 mg/l in the surface water and from 4.96 to 22.60 mg/l in the bottom water at station-1 whereas at station-2, it ranged from 0 to 3.74 mg/l and from 0 to 3.40 mg/l respectively. The dissolved oxygen concentration ranged from 0 to 0.72 mg/l in the surface water and from 0 to 0.42 mg/l in the bottom water at station-1. At station-2 it ranged from 2.69 to 6.21 mg/l in the surface water and from 1.97 to 5.74 mg/l in the bottom water. The pre-monsoon period showed the highest BOD sub(5) of 16.68 mg/l while the monsoon period showed the lowest of 0.61 mg/l. The dissolved oxygen concentration reached its peak during the monsoon period (5.52 mg/l). Long spells of anoxic condition during the post and pre-monsoon periods was a characteristic feature of the retting zone