High volume samplers (Graseby Anderson/GMW) each with a PM10 head and a flow rate of 1.13 m3 min−1 were employed through the whole monitoring program. Whatman quartz fiber filters (8×10 in2) were used for the aerosol collection. Normally one sampling campaign was conducted in each season and each sample had a sampling duration of about 24 h starting from 4 p.m. Details of our PM10 sampling are summarized in Table 1. No sampling took place in autumn 2000 in Hamilton for technical reasons.