A 50-million-litre acid spill from a Chinese-owned copper mine in Zambia is now threatening to kill ties with Beijing, experts say.A massive acid spill from a Chinese-owned copper mine in Zambia, which has caused severe environmental damage along a major river, could also cause severe diplomatic damage between the two countries, according to observers.On February 18, a tailings dam containing acid waste from the Sino-Metals Leach Zambia copper mine – which is majority-owned by China Nonferrous Metals Industry Group – collapsed, sending 50 million litres of concentrated acid waste into a stream that connects to the Kafue River.The river is...