▁ ▁The ▁concentration ▁of ▁organ ic ▁nit ro gen ▁in ▁Spring ▁Brook ▁at ▁the ▁community ▁of ▁Spring ▁Brook ▁was ▁measured ▁to ▁be ▁ 0 . 0 9 ▁mill igr ams ▁per ▁liter ▁in ▁ 1 9 7 5 . ▁The ▁concentration ▁of ▁am mon ia ▁in ▁the ▁form ▁of ▁nit ro gen ▁was ▁measured ▁to ▁be ▁ 0 . 0 4 0 ▁mill igr ams ▁per ▁liter . ▁The ▁concentration ▁of ▁nit r ates ▁in ▁the ▁form ▁of ▁nit ro gen ▁was ▁ 0 . 7 4 ▁mill igr ams ▁per ▁liter ▁and ▁the ▁concentration ▁of ▁nit rit es ▁in ▁the ▁form ▁of ▁nit ro gen ▁r anged ▁from ▁ 0 . 0 4 5 ▁to ▁ 0 . 2 9 ▁mill igr ams ▁per ▁liter ▁in ▁ 1 9 7 1 . ▁ ▁The ▁concentration ▁of ▁sod ium ▁and ▁pot ass ium ▁( as ▁Na ) ▁in ▁Spring ▁Brook ▁r anged ▁from ▁ 1 . 4 ▁to ▁ 3 . 9 ▁mill igr ams ▁per ▁liter . ▁The ▁concentration ▁of ▁mag nes ium ▁r anged ▁from ▁ 0 . 9 0 ▁to ▁ 1 . 6 0 ▁mill igr ams ▁per ▁liter ▁and ▁the ▁calci um ▁concentration ▁r anged ▁from ▁ 7 . 3 0 ▁to ▁ 8 . 8 0 ▁mill igr ams ▁per ▁liter . ▁The ▁concentration ▁of ▁recover able ▁iron ▁in ▁the ▁stream ▁was ▁measured ▁to ▁be ▁ 6 0 ▁micro gram s ▁per ▁liter ▁in ▁ 1 9 7 5 . ▁ ▁The ▁concentration ▁of ▁al kal inity