Lead, chromium and cadmium concentrations are beyond permissible limits

The concentration of heavy metals such as lead, chromium and cadmium continues to increase in the Pallikaranai marsh. This came to light during the preparation of a long-term management plan for the marshland.

The plan, prepared jointly by CareEarth, BNHS and three other organisations, said the concentration of these heavy metals was beyond permissible limits. Various organisations and the Forest department have taken up studies on pollution levels since 2002. The levels of heavy metals in the marsh have been increasing at an alarming rate.

A few years ago, IIT-Madras collected solid waste samples from varying depths in the marsh and conducted an analysis. The results revealed the presence of 408 milligram per kg (mg/kg) of lead as against the permissible limit of 100 mg/kg and 335 mg/kg of chromium against the permissible level of 41 mg/kg. High concentration of heavy metals would cause serious health problems to those living around, the study had warned.

Garbage dumping, release of sewage and disposal of sludge into the marsh were cited as reasons for the increasing metal concentration.

Research on environmental pollution in the past several years in and around the marsh has indicated that due to local topographic conditions, a hydraulic gradient is created, which recharged the ground water in the marsh. This condition facilitated the flow of leachate and hazardous waste from the Perungudi garbage dump towards the central and southern portions of the marsh.

The Conservation Authority for Pallikaranai Marsh entrusted the management plan work to organisations with the active participation of stakeholders. Of the many components that were addressed in the management plan, the issue of mitigating environmental pollution, notably that of water within the marsh, has been accorded immense importance.

Given the evidence of the negative environmental impact caused by the dump at Perungudi, it is quite clear that dumping could not be continued if the integrity of the marshland is to be maintained. The planned closure of the dumping yard followed by a thorough remediation is the most logical plan of action, the management plan suggested.