Government programs to reduce acid rain have resulted in cleaner emissions from u. s. industries in recent years. as a result, the sulfate concentration in rainwater has declined significantly. but the sulfate concentration in some lakes is showing little, if any, change. why might this be true?

This is still true because there are still manufacturing companies out there that are not really following protocols and procedures that are geared towards a green environment. The sulfate concentrations in lakes show little changes because contaminants are still present within the atmosphere, hydrosphere, and troposphere of the Earth. It would take a long time before such lakes will be rejuvenated into their original state.