BACKGROUND AND OBJECTIVES: Heavy metals can enter the food chain in the aquatic environment and become available for accumulation in biota. Industrialization and agricultural developments are progressively causing ecological concerns, which must be addressed. This study aimed to ascertain the heavy metals in Tamiraparani River sediments using contamination factor and contamination degree, which would help administrative bodies implement control measures. For heavy metal analysis, this study is unique in that it focuses on the far downstream, where the sediment deposition is higher.
METHODS: Using an atomic absorption spectrophotometer, the abundance of iron, manganese, copper, and chromium was determined in this study. In this study, the heavy metals in the sediments are selected on the basis of previous studies. Additionally, to assess sediment pollution status, contamination factor, contamination degree, and pollution load index were used. Furthermore, a geographical information system was used to analyse the temporal variations of heavy metals in the sediments for different spatial locations downstream of the river.
FINDINGS: The study revealed that iron > manganese > chromium > copper concentration ranges from 3838 to 853, 68 to 7.8, 8.3 to 0.5, and 5.6 to 0.26 milligram per kilogram, respectively. The contamination factor ranges from 0.006 to 0.093 among all the sampling locations, heavy metals, and seasons, indicating that the pollution is in a low-level category. The contamination degree ranges from 0.039 to 0.378 among sampling stations and seasons, also indicating low-category pollution. The pollution load index value ranges from 0.004 to 0.092, which is less than 1 (guideline value), indicating less pollution impact. The seasonal variation shows that the post-monsoon is highly polluted because of the excessive sediment deposit from upstream after monsoon rainfall.
CONCLUSION: The contamination factor and contamination degree are within the acceptable limit. However, they are in an increasing phase during monsoon seasons, which indicates that heavy metals are from industries and are built up along the river banks upstream. Additionally, chromium and copper are in high concentrations during post-monsoon (chromium = 6.643, copper = 5.636) than during pre-monsoon because of anthropogenic activities and industrial waste discharge into the river stream.
- Heavy metals have an increasing tendency with sampling location (S5 > S4 > S3 > S2 > S1) due to salinity and tidal fluctuation.
- The heavy metal copper was found due to the erosion of the catchment area with natural copper deposits. Other heavy metals, chromium, iron, and manganese, were found due to industrial discharge, agricultural runoff, and discharge of untreated sewage.
- Temporal analysis shows the concentration is higher in the post-monsoon dry season and lowest in the pre-monsoon season.
- All the stations have contamination factor, contamination degree, and pollution load index under the low category.
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