During the Puja festival in West Bengal, a huge number of idols are immersed in the river Ganga every year. The idols are painted with different metal based paints. On immersion of these idols in the river, the river water is contaminated with these metal paints and a change in chemical load in the river body is expected. With this objective in mind , like last year , the Board decided to monitor the effect of idol immersion in the river Ganga with respect to change in Dissolved Oxygen in the river body and metal contamination.

The monitoring was conducted between October 2002 and June 2003in two phases. The first phase was conducted during immersion of Kali Idols in the period between 07.11.2002 and 09.11.2002 at Police Jetty near Babughat. The results were compared with the results of control samples collected in June 2003.

During the first phase , every four hours composite samples were collected at hourly interval by Automatic Sampler and were subsequently analyzed for metal contents. Besides this the Dissolved Oxygen of the river body were monitored at hourly interval using portable DO meter. Solids samples from river bank of the said spot were also collected to study the metal deposition in them in comparison to control solid samples collected later . Part of Idol was also collected to study the metal content in them.

Finally water & soil samples were collected from the same spot after a couple of months when the river was almost free from Idol Immersion activities and studied for metal contamination or deposition if any.

The results thus obtained are tabulated below:

TABLE - 1: Dissolved Oxygen monitoring

TABLE - 2A: STUDY OF METALS IN CONTROL RIVER WATER SAMPLES

TABLE - 2B : STUDY OF METALS IN COMPOSIT RIVER WATER SMPPLES COLLECTED DURING IMMERSION

TABLE - 3A: STUDY OF METALS IN CONTROL SOIL SAMPLE

TABLE - 3B: STUDY OF METALS IN SOIL SAMPLE COLLECTED AFTER IMMERSION ACTIVITIES

TABLE - 3B: STUDY OF METALS IN PART OF IDOL SAMPLE COLLECTED DURING IMMERSION

From the above tabulated results the following interpretations may be drawn :

1) The DO values of the samples indicated only little or no significant changes.

2) A part of Kali idol was collected and metal content of the paints on the idol part was analysed. The values obtained indicated presence of significant amount of metals like chromium and lead .

3) The hexavalent and total Chromium , Cadmium, Copper, Nickel, Lead, Zinc content in the digested water samples indicated little or no significant contamination in river water due to idol immersion as compared to their respective controls.

4) The study of the water samples collected a couple of months later from the same spots when the river was almost free from idol immersion activities indicated very little or no significant metal or chemical contamination in the river body. The contamination observed during idol immersion had been carried away during the lapse of time.

5) The soil samples collected from the river bank at the immersion sites a couple of days after the immersion indicated some deposition of metal based material and similar study of the soil samples collected a couple of months later indicated that the deposition had been washed away during the lapse of time.

CONCLUSION:Comparison of the results obtained in this study with the review of water quality objectives, requirements and zoning and classification for Indian water Bodies, published by CPCB, June 2001, indicated that the average chemical and metal contamination due to idol immersion activities in the samples collected from the river Ganga is not a major environmental problem. Though in some isolated cases the values obtained are high enough, as the rivers are open systems, the retention time is very low. Any alteration in water quality or discharge of pollution would thus, not remain at one location for long. As seen in this particular study, the metal content of the parts of idols which is high enough contributed only a little in the water body of the river Ganga and the contamination whatsoever is subsequently carried away in the flow of river.

For other parameters which are being regularly monitored under GAP project, namely pH, BOD, Nitrate ,Nitrite and Electrical conductivity etc. have values which indicate that the water body of the river in the vicinity of the idol immersion spots are of excellent to desirable quality. For total and feacal Coliform results however indicate that the river body is not within excellent, desirable or acceptable quality. This is because of anthropogenic and other natural and industrial sources.

Human interests and religious sentiments can not be ignored or downgraded in importance and variation in dissolved oxygen content, metal and chemical contamination during idol immersion activities in the river under study is not posing a serious environmental threat as seen in the case study for the last three years.

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