China's Yellow River tributaries have been "seriously polluted" by an oil spill last week, further contaminating badly-tainted drinking water resources, state media has said. Last week a ruptured pipe operated by China's oil giant, PetroChina, sent 150,000 litres of fuel down two major tributaries of the Yellow River… China National Petroleum Corporation, the parent company and the country's largest oil producer, said the leak was caused by a "third party" during construction work…The Yellow River is one of China's longest and a key watercourse that provides drinking water for millions of people including the population of eight cities downstream from the oil spill, the Xinhua news agency said…