Enabling accurate mercury measurement for increasingly stringent emissions controls

Mercury has been elevated to the status of a pollutant of global concern owing to some of its unique toxic properties which pose environmental and health risks. A chemical element, mercury is found both naturally and as an introduced contaminant in the environment, mainly from high-temperature industrial processes such as alkali and metal processing, incineration of coal and oil in electric power stations, foundries, waste combustion and oil and gas processing.

Mercury rapidly moved up the pollution control agenda in the European Union (EU), the USA and Asia prior to the legally binding UNEP global treaty on mercury, the Minamata Convention, adopted in 2013 and signed by 128 countries. The objective of the Minamata Convention is to protect human health and the environment from anthropogenic emissions and releases of mercury and mercury compounds. In late 2011, the US EPA finalised the Mercury and Air Toxics Standards (MATS), the first national Clean Air standards to reduce emissions of mercury and other toxic air pollutants from new and existing coal and oil-fired power plants. In the EU, the Community Strategy concerning mercury was adopted in 2005 and reviewed in 2010. It focuses on mercury emissions to air, the banning of mercury exportation (including certain mercury compounds) and enforcing restrictions on products containing mercury and industrial processes using mercury. In regard to industrial emissions of mercury, the EU Industrial Emissions Directive (IED) addresses the issue via the Reference documents on the Best Available Techniques (BREF). The European Parliament has also recently issued the Medium Combustion Plants Directive (MCPD) from 2018 for new plants and from 2025 for existing installations. The MCPD does not currently include mercury within the controlled pollutants but there is an expectation that mercury may indeed be included in the scope of MCPD in a future update.

As legislation and action plans grow in number and stringency, the importance of monitoring and quantifying emission pollutants in an accurate and transparent manner are becoming priorities. Typical analytical instruments in this application include Atomic Absorption Spectrometers (AAS) and Inductively Coupled Plasma (ICP) mass spectrometers.

The Linde Group was the first company to offer to the market gaseous mercury calibration standards for the monitoring and detection of emissions. A comparison is made between these calibration gas standards and other methods of calibrating analytical instruments.