Explosives-originated nitrogen emissions from dimension stone quarrying in Varpaisjärvi, Finland

As the emissions of nitrogen (N) compounds from mining areas can have detrimental effects on the aquatic environment through eutrophication, oxygen deficiency or direct toxicity, the management and mitigation of these compounds have received increasing attention in recent years, especially at large mine sites. Much less is known about the nitrogen emissions from smaller-scale quarrying operations although they are considerably more numerous and widespread than large mines and often have less resources to mitigate their emissions. To investigate the amounts and balances of explosives-originated N compounds at smaller-scale mining activities, the surface waters around a dimension stone quarry located in Varpaisjärvi in Finland were monitored throughout a year. According to the results obtained from the target quarry, the explosives-originated N drainage of natural stone quarrying is relatively low, on the scale of tens of kilograms per year, most of which is released during the spring floods in April–June. The low amount of N drainage is mainly related to the use of small total amounts of N-poor explosives. However, estimates of N released from the target quarry correspond to a relatively high 16–28 % loss of N from blasting explosives commonly used in natural stone extraction. Although some undetonated explosives are carried to the waste rock piles along with the stone material, the main sources of N emissions at the dimension stone quarrying site seem to be pit dewatering water.