只有一点要更正的:
ppm = part per million (百万分之一, 1/1000,000)
ppb = part per billion (十亿分之一, 1/1000,000,000)
ppm = part per million (百万分之一, 1/1000,000)
ppb = part per billion (十亿分之一, 1/1000,000,000)