An improved sampling system for atmospheric mercury in remote areas

Abstract

Monitoring atmospheric pollutants requires robust sampling and determination methods. Trace pollutants often necessitate prolonged sampling with pre-concentration, demanding careful management to maintain sampling integrity, stable flow, and accurate volume measurements. Certified flow devices and pumps can ensure stability, but in remote areas, challenges arise: availability of stable power, battery-operated equipment may run out of power during extended sampling, and flow accuracy can be compromised by power fluctuations or interruptions, common in battery-powered systems. In such situations, atmospheric passive samplers, which use a sorbent material and do not rely on active extraction, are an alternative. However, they face calibration issues in field conditions, and atmospheric factors like temperature, pressure, and humidity influence the sampling rate, leading to high uncertainty in uptake rates. Long periods are needed to achieve sufficient mass loadings due to low uptake rates. A new remote sampling system is proposed using an intelligent solar battery-powered pump for prolonged sampling. This system's key advantage is obtaining an accurate sampling volume via a datalogger that constantly records the flowrate. Two systems were tested in parallel for atmospheric mercury (Hg) sampling on gold Amasil™ Traps, verified by comparing with mains-powered mass-flow controllers (MFCs) and pumps, and online automated atmospheric Hg analysis. Indoor and outdoor sampling yielded comparable results. The combined uncertainty for determining atmospheric Hg via atomic fluorescence spectrometry (AFS) was under 5 % (k = 2) using the new system. The contribution of sampling volume determination to the overall uncertainty was under 1 %, which is a significant improvement over passive sampler devices. With the ability to back-calculate flowrate at any point, the final volume is more accurate compared to current remote sampling systems without electrical facilities. Volume loadings are significantly greater than passive samplers, providing improved time resolution for data and lower detection limits.