Chemical deterioration of Sliema to Mellieha coastline

The chemical status of the stretch of coastline between Sliema and Mellieha, which includes most tourism development in the island, has deteriorated substantially over the past decade to the extent that it won’t achieve good chemical status by 2021.

This emerges from Malta’s Second Water Catchment Plan for the years 2015-2021 presented to the EU commission in April. 

The chemical status in this stretch of coastline was assessed to be good in 2008. But while its ecological status has remained good, its chemical status has deteriorated.

The body fails to achieve good chemical status due to mercury and PAH contaminants found at levels that exceeded the Environmental Quality Standards on more than one occasion during 2012-2013. 

Polycyclic aromatic hydrocarbons, which were found in excess of what is required by EU directives in this part of the coastline, are organic compounds containing only carbon and hydrogen formed during the incomplete combustion of organic materials such as coal, fossil fuel, volcanic activity and petroleum seeps. PAC result in, reduced reproductive success in fish and may be harmful to human health when contaminated shellfish are consumed. 

The potential sources of PAH and mercury contamination are not known and still being investigated. 

Additional monitoring and investigations into the possible sources for such contamination is required according to the report. The necessary improvements in the chemical status of the water body cannot be reasonably achieved by 2021 due to the fact that the scale of improvements required can only be achieved over a longer period of time.

Mercury found 3 times higher than allowed

Moreover the average mercury annual values registered by all monitoring stations measuring the quality of Maltese coastal waters were about 2-3 folds higher than the Maximum Allowable Concentration-Environmental Quality Standard as set by EU Directives. Mercury levels also exceeded 2008 levels in all monitoring stations.

The document makes it clear that the situation cannot be redressed by 2021. While confirming Malta’s “poor chemical status” when it comes to mercury, the report describes mercury as Malta’s “only failure” when it comes to the good chemical quality of its coastal waters.

In fact when mercury in not considered only three marine bodies, namely the stretch between Sliema and Mellieha, the area of the Grand Harbour and Cottonera and the stretch between Xghajra and Marsaskala failed to achieve good chemical status.  But when mercury is considered the whole island failed to achieve good status.

The only risk to human health from mercury contamination comes from consuming large fish such as tuna and swordfish, that would have been in longer contact with contaminated water than small fish, and would present a risk to human health from the effects of mercury.

Mercury is seen to be a major concern “not only due to its exceedances (of EU directives) but also due to its ubiquitous nature, even in water bodies that are considered to be relatively pristine”.

According to the report a Mercury Management Plan will be investigating potential sources of mercury and potential mitigation measures. 

The investigation, estimated to cost €50,000, will involve the inspection of all potential sources of mercury pollution including land-based, air based and transboundary sources.

The second stage would be to identify potential measures to mitigate Mercury contamination coming from sources that can be controlled from land. 

According to the report apart from anthropogenic sources of mercury, volcanic activity and geologic cinnabar (mercury ore) deposits are also known to contribute to mercury levels in the environment. 

“Malta is yet to understand what can be considered to be the natural occurring background level of mercury in the Mediterranean and what could be contributing to increments in mercury found in our waters”. 

The report also indicates the Ta’ Barkat sewage treatment plant and the Delimara power station as possible sources of the high levels of mercury in Maltese coastal waters. Ship and bilge waste could also be another source. 

This is because high levels of mercury contamination in Malta’s surface waters occurs not only where there is a high mercury contamination in sediments but also where the mercury concentrations in the sediments were low.  

However trans-boundary sources could also have a part to play in contributing to the presence of mercury all around Maltese coastal waters. 

Mercury emission usually occurs during the fuel combustion of coal, waste or oil. Municipal sewage discharge can also potentially be a source of mercury contamination in the environment. The atmospheric deposition of mercury could also be a main contributor.