Problem/Challenge:

One harbour/port in Mossel Bay, South Africa – although relatively small, hosts maritime and vehicular activities that contribute to air emissions. The challenge was to assess whether these emissions posed a significant risk to ambient air quality and nearby sensitive receptors, including residential areas, schools, and healthcare facilities. This assessment was necessary to ensure that port operations comply with air quality standards and do not adversely impact human health or the environment.

Solution/Approach Taken:

An updated Air Quality Impact Assessment was conducted, focusing on dispersion modelling of emissions from key port-related sources. These included:

• Maritime fuel combustion from ocean-going and domestic vessels.
• Emissions from heavy-duty and light motor vehicles.

Excluded from the study due to insufficient data were emissions from recreational boats, cargo handling equipment, locomotives, and stationary petrochemical transfer activities.

Rayten Engineering Solutions used a combination of emission inventory data and high-resolution meteorological inputs (CALMET and WRF data) to run CALPUFF dispersion modelling simulations. The assessment focused on key pollutants such as PM10, PM2.5, NOX, SO2, CO, NH3, VOCs, and lead (Pb). Predicted ground-level concentrations were compared against South African National Ambient Air Quality Standards (NAAQS) and Alberta international guidelines where necessary.

Findings showed:

• Predicted pollutant concentrations across all modelled receptors were well below applicable ambient air quality standards.
• No exceedances were observed at the port or nearby sensitive receptors.
• The residual risk to air quality from port operations was rated as low, with a highly unlikely likelihood of significant impact.

Role of Rayten Engineering:

Rayten Engineering Solutions served as the air quality specialist for the project. Their responsibilities included:

• Reviewing site operations and emission sources.
• Compiling and updating the emissions inventory.
• Conducting dispersion modelling using industry-standard tools and methods.
• Assessing pollutant impacts against national and international air quality standards.
• Providing expert opinion on risk significance and recommending mitigation where needed.

Through their technical expertise, Rayten confirmed that current port activities pose a low air quality risk and provided the scientific basis to support ongoing environmental compliance.