通常的人们只知道牲畜排泄的臭气难闻，令人作呕，却很少认识到这些臭气同汽车尾气一样有害。它能使树木枯死，并导致土壤酸化，侵蚀沙岩等建筑材料。据德国环保部门的一项研究表明，仅在德国，1994年就有53．3万吨氨气从农场排放到空气中。欧洲乡村的空气已经因集约化畜牧业的 The usual people only know that the bad smell of livestock excretion, disgusting, but rarely realize that these odors are as harmful as the car exhaust. It can make trees dead and lead to soil acidification, erosion sandstone and other building materials. According to a study by the German environmental protection agency, in Germany alone, 533,000 tons of ammonia was released from the farm to the air in 1994 alone. The air in the European countryside has been due to intensive livestock husbandry