parts per million

基本解释

The light reflected by the newfound extrasolar planet, or exoplanet, changed by only about 6.5 parts per million, relative to the brightness of the host star.
这颗新发现的太阳系外行星——或者称为外行星——所反射的光线变化相对于其恒星的亮度只有百万分之6.5。
At 250 parts per million CO2, the shellfish grew vigorously, and at 750 ppm and higher they were crippled, feeble creatures with thin shells and weak connective tissues.
在 CO2 含量为百万分之 250 时，甲壳类生物生长得很好，而到了百万分之 750 或更高时，它们的甲壳变薄、连结物质变弱，成了残破而虚弱的生物。
They added that concentrations of carbon dioxide, the main greenhouse gas, should be limited to 350 parts per million of the atmosphere -- below current levels of 387 ppm.
同时应该把大气中二氧化碳的含量应该控制在百万分之350个单位，目前的含量水平为百万分之387个单位。

The team found levels of lead as high as thirty-two thousand parts per million in tests on some paint samples from Ecuador.
Breathing in two hundred parts per million of carbon monoxide will cause the first signs of poisoning.
Twelve thousand parts per million of the gas will cause death in one to three minutes.

Floating sensors hold the oxygen to between 2 and 2.5 parts per million of water.
FORBES: Muckraker