BEIJING, May 23 (Reuters) – * China’s April scrap aluminium imports fell by 27.8 percent from March to 130,000 tonnes, after the country slapped a 25 percent import tariff on aluminium scrap from the United States, its biggest supplier of the material, with effect from Apr. 2 * April scrap aluminium imports also fell 23.1 percent year on year, data from the General Administrations of Customs showed on Wednesday * China Jan-April scrap aluminium imports were down 11.4 percent year on year at 620,000 tonnes * China this year introduced new impurity thresholds on imported waste, including metals, as part of a crackdown on “foreign garbage,” sending imports significantly lower. * China’s April scrap metal imports fell 35.9 percent year on year to 440,000 tonnes * Jan-April scrap metal imports were down 31 percent year on year at 1.94 mln tonnes * China April scrap copper imports down 36.7 pct year on year at 180,000 tonnes * China Jan-April scrap copper imports down 38.5 percent year on year at 740,000 tonnes * China, for the second month in a row, imported zero waste plastic in April