Radon (222Rn) levels in ground waters from Mutomo area, in Kitui county

Abstract

All living organisms continuously are exposed to natural radiation, which contributes most of the effective dose equivalent they receive. Radon, a naturally occurring colorless, tasteless and odorless radioactive gas is one of these radiations. The gas exists naturally in various environmental media such as water, geological sediments and air. It has gained focus since it is the largest contributor to radiation doses received by the human population via inhalation and ingestion posing great health risks. The main objective is to determine the radon levels in underground waters in Mutomo Sub County, in Kitui County using the RAD 7 alpha detector. The study further examined the radium levels in sediments collected from the proximity of sampled water sources using high purity germanium (HPGe) gamma-ray spectrometer to establish the correlation with radon in water. The radon concentration in water ranged from 0 - 120±6 kBqm-3 with an average value of 30±1.5 kBqm-3 which is above the recommended limit of 11 kBqm-3 suggested by US-EPA, WHO and EU bodies. The calculated values for the absorbed dose are in the range 1.26 - 3.24 mSvy−1, which is well below the recommended level. The annual effective dose (AED) via ingestion averaged 0.006±0.0003 mSvy-1 while the radon in air from water averaged 0.07±0.003 mSvy-1, which are both below the safety limit of 0.1 mSvy-1 recommended by WHO 2004, and ICRP 2005 for ingestion and inhalation. Radium in sediments reported an average of 41 ±2.07 Bq/Kg which is above the world’s average of 35 Bq/ kg reported in UNSCEAR reports. The radiation doses in water from sampled underground water are insignificant to term the water unsuitable for drinking and other domestic purposes. Correlational analyses between radium in sediments and radon in the water reported a weak positive coefficient suggesting a difference in the geological composition of surface matter and underground aquiver holding water.