Heavy metals accumulation in irrigated soil on lettuce production (Lactuca sativa) in Gombe state, Nigeria

The study was conducted in Gombe State, Nigeria. The objective of the study was to determine the concentration and distribution of heavy metals inirrigated soil as it affect Lettuce (Lactuca sativa) production in Gombe state. Three zones that make up the state namely Gombe North, Gombe Central and Gombe South were used for the study. From each zone three locations were selected, plant (Lettuce) samples and soil samples were collected randomly from the locations and air dried in a room, sieved, grinded and digested as describe by USEPA (1996) and analysed in standard laboratory. The result showed that plant (Lettuce) heavy metals concentration were in descending order of Fe>Zn>Cu>Pb>Cd>Cr>Ni>As, and ranged as follows (Fe.4.31b – 7.15amgkg-1),(Zn 3.40b – 7.97amgkg-1), (Cu 2.19b – 2.76a), (Pb 0.80b – 2.46a mgkg-1), (Cd 0.22b – 0.45amgkg-1), (Cr 0.17b – 0.30a mgkg-1), (Ni 0.10b – 0.45amgkg-1) and (As0.06b – 0.10amgkg-1) across the zones. All the concentration of heavy metals in lettuce plant was within the permissible limit of food standard committee and WHO. The result from the study suggested that significant difference existed in heavy metal concentration in lettuce plant analysed which might be due, partly, to the geology of the soil and anthropogenic activities of the communities. Though the concentration in the plant (lettuce) was low, there is tendency of accumulation in future. Regular monitoring of heavy metals in plant was suggested to avoid excessive build up in future and further research on other crops grown in the study areas was also recommended.