Open Path Boundary Monitoring

The objective of this work was to investigate suitable options and implement a real-time monitoring method that would provide accurate detection of PM movement across significant and critical sections of a site boundary, with the potential to be visualised in real-time.

Such a demonstration could assist the mining industry by providing early detection of adverse PM movements across site boundaries. Real-time information will enable the industry to better manage on-site dust emissions, reduce unnecessary production stoppages and improve general air quality in the area.

The study involved an initial literature review to compare candidate open-path methods suitable for this application. This aided in selection of the experimental equipment and methods.

Locations to carry out the field component of the work were selected in consultation with industry partners / site personnel. The selected locations represented critical boundary locations (over an open pit and along a fence-line adjacent to a public road).

Following site selection, the experimental design and sampling protocol were developed and field monitoring was undertaken.

Field measurements at the Hunter Valley Operations mine identified dust emissions from blasting, hauling and activities within the pit, and confirmed that the (MiniMPL) lidar technology is suitable for detecting PM10 plumes from specific dust-generating events.

The field monitoring portion of the study also involved a calibration of the lidar with conventional real-time particulate (DustTrak) monitors, completed at Mount Thorley Warkworth (MTW) mine. This exercise revealed that there is a relationship between the cross-polarised components of the normalised relative backscatter (NRBcross) recorded by the lidar and PM10 concentration. This relationship was used to infer indicative PM concentrations during field monitoring.

Field monitoring at MTW established that the MiniMPL lidar was able to identify PM10 plumes crossing the fence line, and would therefore be useful in providing early warning of the potential for boundary exceedances caused by site activities.

Sampling was also undertaken at Fort Scratchley in Newcastle where sulfur particles from diesel emissions originating from ship movements were detected. Aerosol plumes were also identified from the Kooragang Island ammonium nitrate facility using NRBco data.

The findings suggest that lidar is suitable for use at mines and other industrial complexes for detecting PM plumes, evaluating the effectiveness of dust mitigation and control strategies and tracking of dust plume movement and dispersion at critical fence lines locations. Monitoring demonstrated that both spherical and non-spherical aerosol plumes can be identified using the NRBco and NRBcross lidar data respectively

The outcomes of the monitoring confirm that the technology is suitable for use on an open-cut coal mine to identify sources of dust emissions, indicative concentrations and particulate matter (PM) movement under different meteorological conditions across critical site boundaries including fence lines and open pits.

Potential areas for future work include investigation of:

· Longer term field trials of lidar instrumentation at a mine fence line or open pit location, co-located with conventional particulate monitoring;

· Investigation of the relationship between PM10, extinction and NRBcross at particulate concentrations < 50 μg/m3;

· Calculation of the extinction coefficient and the aerosol optical depth in the Hunter Valley which would improve the accuracy of the PM concentration calculations;

· Use of direct extinction measurement through the dust plume concurrent with Lidar observations;

· Further enhancement of emission calculations.