Why is storm water runoff a problem for water pollution?

Humans are believed to have evolved in coastal regions in east africa. the region had an abundant supply of fish for early humanoids to eat. when scientists analyze the fads gene they see an interesting pattern. people whose families have lived in this area of east africa for generation show a high level of diversity in alleles for the fads gene. conversely, people whose families had migrated inland a moderate distance from sources of fish showed a much lower diversity for fads gene alleles. additionally, the fads alleles found in people whose family has lived inland for generation are almost all gene alleles which produce fads proteins with a high level of function and activity. how do anthropologists explain this?

What happens when water’s salinity increases? mass decreases. freezing point decreases. buoyancy of objects decreases. the amount of dissolved minerals decreases.

In the sentence "a mining company will consider the distribution of coal when deciding how to mine the coal," what does the word distribution mean?