▁concentration ▁of ▁nit r ates ▁near ▁the ▁source ▁of ▁Lim estone ▁Run ▁was ▁ 1 . 2 ▁and ▁ 5 . 0 ▁mill igr ams ▁per ▁liter ▁on ▁September ▁ 2 0 ▁and ▁October ▁ 1 8 , ▁ 2 0 0 3 , ▁respectively . ▁In ▁the ▁middle ▁of ▁the ▁stream , ▁the ▁concentration ▁of ▁nit r ates ▁was ▁ 6 . 2 ▁and ▁ 7 . 6 ▁mill igr ams ▁per ▁liter ▁on ▁those ▁dates ▁and ▁was ▁ 4 . 4 ▁and ▁ 5 . 4 ▁mill igr ams ▁per ▁liter ▁slightly ▁up stream ▁of ▁Lewis burg . ▁The ▁nit rate ▁concentration ▁in ▁Lewis burg ▁was ▁ 3 . 9 ▁on ▁September ▁ 2 0 ▁and ▁ 5 . 0 ▁on ▁October ▁ 1 8 ▁and ▁was ▁ 3 . 9 ▁and ▁ 4 . 9 ▁at ▁the ▁mouth ▁on ▁those ▁dates , ▁respectively . ▁These ▁nit rate ▁concentr ations ▁are ▁relatively ▁high ▁due ▁to ▁the ▁fact ▁that ▁Lim estone ▁Run ▁flows ▁through ▁large ▁amounts ▁of ▁agricult ural ▁land . ▁ ▁There ▁are ▁no ▁ph osph ates ▁in ▁the ▁waters ▁of ▁Lim estone ▁Run ▁and ▁its ▁trib ut aries , ▁except ▁for ▁the ▁head w aters , ▁which ▁had ▁a ▁ph osph ate ▁concentration ▁of ▁ 0 . 3 ▁and ▁ 0 . 1 ▁mill igr ams ▁per ▁liter ▁on ▁September ▁ 2 0 , ▁ 2 0 0 3 ▁and ▁October ▁ 1 8 , ▁ 2 0 0 3 , ▁respectively . ▁ ▁The ▁concentration ▁of ▁ch lor ides