sentences:  In June 2016, Norilsk shut down one of its factories, which was emitting 380,000 tonnes of sulphur dioxide every year, 25% of the total of sulfur emissions in the city, in an effort to clean up its environmental record.It also said it would invest £3.5bn to modernise manufacturing by 2020.At the end of 2016, Nornickel signed a major contract worth $1.7 billion with Canadian company SNC-Lavalin, to install sulfur dioxide filtration and storage technologies on its plant in Norilsk, in what is said to be one of the largest environmental projects of its kind.