River plastic emissions to the world's oceans

Modelled plastic inputs into the ocean from rivers worldwide. The shapefile contains 40,760 input points (EPSG:4326, WGS 84) with the following attributes:i_[ level ]: plastic input in tonnes per year. (level=low, mid or high for lower, midpoint and upper estimates)i_[ level ]_[ month ]: plastic input in tonnes per month. (level=low,mid,high; month=jan,feb,...,dec)runoff_[ month ]: monthly averaged runoff in catchment in mm per day. (month=jan,feb,...,dec)mpw: mismanaged plastic waste production in catchment in tonnes per year. area: catchment area in square kilometers.

本数据集模拟了全球河流向海洋的塑料输入通量。其配套的矢量文件（shapefile）包含40760个输入点位，坐标系采用EPSG:4326（WGS 84），附带以下属性字段：
1. `i_[level]`：代表流域每年的塑料输入量，单位为吨/年，其中level取值为low、mid、high，分别对应低、中、上限估算值；
2. `i_[level]_[month]`：代表每月的塑料输入量，单位为吨/月，level取值为low、mid、high，month为jan至dec（即1至12月的英文缩写）；
3. `runoff_[month]`：代表流域内逐日平均月度径流量，单位为毫米/天，month取值同前；
4. `mpw`：流域内管理不当塑料废弃物（mismanaged plastic waste）的年产量，单位为吨/年；
5. `area`：流域面积，单位为平方千米。