Because the precipitate in the rain is the first thing to be caught by peoples attention , we call it acid rain 因为最早引起人们注意的是雨中含有这种沉降物，所以习惯上称为酸雨。
The total dose increases continuously from the time of arrival of the fallout toward the limiting ( infinite time ) value 总剂量从沉降物抵达时开始就不断上升直到极限值（无限时间） 。
The food supplies necessary to sustain the large vent communities , however , must be many times the ordinary fallout 然而，维持喷口处庞大动物群所必需的食物供应必须数倍于一般的沉降物。
The factors mainly include soil acidifying , higher organic matter content in the soil , lead of precipitum in the air and the processing of the tea leaves in the factory 这些来源主要包括：茶园土壤酸化和较高的有机质含量，大气沉降物中的铅和茶叶的加工过程。
