Heavy Metal Composition and Some Characteristics of the Soils of Mangrove Forests of Andamans-Indian Islands

Variation in soil properties and heavy metal content and their distribution along tidal gradients of mangrove at five different sites in Andamans were investigated. Two transects A & B were established perpendicular to the shoreline. Vegetation in Transect A was least disturbed by human activities; while transect B was higly disturbed, being close to human settlement. Concentration of organic C was high in landwards sites and decreased gradually along tidal gradient, while pH and salinity increased with distance from landward to seaward sites. Transect A had higher organic matter content than transect B. Iron, Mn, AI, Ni, Zn & Cr were concentrated in sediments deposited within 60–80 m of the sea shore showing thereby restricted movement of metals due to the presence of mangroves. pH of highly disturbed mangrove soils had a significant and positive correlation with Fe, AI, Mn and Cr, but such correlations were absent in the least disturbed soils except Cu. Higher concentration of Cr metal in the highly disturbed soil may cause adverse effect on crops due to higher bioavailability in the absence of mangrove barrier.