Mepa raises alarm on deteriorating soil quality

Soil in Malta is facing the threats of erosion, decline in organic matter, contamination and salinisation, Mepa warned today in the State of the Environment report for 2008.

It explained that soil organic carbon content is one of the primary indicators of soil quality, as it is a source of plant nutrients and influences the exchange of nutrients, water retention, soil structure and its stability, and soil biodiversity.

In 2006, the average organic matter in the sampled topsoils was 2.1 per cent, 0.2 per cent more than in 2002 "and just above the 2.0 per cent soil organic carbon threshold below which potentially serious decline in soil quality is expected to occur."

Mepa said soil contamination could pose risks to human health, soil function and the wider environment.

Since data on soil contamination remains scanty, lead concentrations in topsoils were used as a proxy to monitor contamination.

The average lead content in 16 sites which were monitored increased from 78 milligrams per kilogram in 2002 to 125mg/kg in 2006, with the highest concentrations at Paola (451mg/kg) up from 266 mg/kg in 2002.

Lead concentrations were found to generally exceed 100mg/kg in south and central Malta.

The possible causes of lead in soil included remnants from car exhaust, paint, used pellets from hunting or emissions from industrial activities.

The reports says that soil salinisation - the excessive increase of soluble salts in the soil - was among the most important and widespread of soil degradation processes.

Maltese soil is vulnerable to soil salinisation, with irrigation using salt-rich groundwater being a major cause.

Between 2002 and 2006, average soil conductivity (indicating salinity) increased by 30 per cent from 581 micro Siemen per centimetre to 756 at the sites which were monitored.

The highest values ere recorded in the coastal areas owing to sea spray.

The report says Malta need to update legislation and build capacity for monitoring and enforcement in this area.