Abstract:
Contamination status and spatial distribution of DDTs and HCHs were investigated in sediments collected
from ponds and riverine system from districts Nagaon and Dibrugarh, North East India. A total of 113
surface sediment samples were collected from both the districts including 43 from ponds/wetlands and
70 from rivers/streams. Based on dry weight (dw), the mean concentration of ΣHCH and ΣDDT in
sediments were found to be 287 ng/g (71.2–834 ng/g) and 321 ng/g (30.1–918 ng/g) for district Dibrugarh
while 330 ng/g (39.2–743 ng/g) and 378 ng/g (72.5–932 ng/g) for district Nagaon, respectively. DDTs and
HCHs in sediments were well influenced by total organic carbon, clay and silt content of sediments.
Source identification revealed that sediment residue levels have originated from long and recent mixed
source of technical HCH and Lindane for HCHs and mainly technical DDT for DDTs. Majority of samples
exceeded the sediment quality guidelines (SQG) for γ-HCH, p,p′-DDT and ΣDDT indicating potential
environmental risk. This baseline data can be used as reference for regular ecological and future POPs
monitoring program.
