<p>This study investigated the effect of grain size and temperature on arsenic leaching from non-acid generating waste rock containing gersdorffite, sourced from the Whale Tail pit at the Amaruq gold mine in Nunavut, Canada. Nine column tests were conducted over a one-year period using North Komatiite waste rock with five different grain sizes (50–15&#xa0;mm to &lt; 0.85&#xa0;mm) and three temperature conditions (21&#xa0;°C, 5&#xa0;°C, −&#xa0;2&#xa0;°C). Results show that finer materials produced higher arsenic concentrations in leachates, despite a lower gersdorffite content, indicating that particle size and mineral liberation strongly influence arsenic release. Additionally, the temperature variations had a measurable but limited effect on arsenic mobility. At temperatures close to and above and below 0°C, arsenic concentrations were half that at 20&#xa0;°C, but some leaching still occurred, confirming that gersdorffite remains reactive at subzero conditions due to its salt-like behavior. Arsenic was found primarily as arsenate (As⁵⁺) in solution, and dissolution followed a congruent path with no evidence of surface passivation. Our findings highlight the importance of considering both physical properties and arsenic source mineralogy when designing mine waste management and closure strategies, particularly in cold environments.</p> Graphical abstract <p></p>