BORON CONTENTS AND ISOTOPIC COMPOSITIONS OF HOG MANURE, SELECTED FERTILIZERS, AND WATER IN MINNESOTA

Boron-isotope (delta(11)B) values may be useful as surrogate tracers o f contaminants and indicators of water mixing in agricultural settings . This paper characterizes the B contents and isotopic compositions of hog manure and selected fertilizers, and presents delta(11)B data for ground and surface water from two agricultural areas, Boron concentra tions in dry hog manure averaged 61 mg/kg and in commercial fertilizer s ranged from below detection limits in some brands of ammonium nitrat e and urea to 382 mg/kg in magnesium sulfate, Values of delta(11)B of untreated hog manure ranged from 7.2 to 11.2 parts per thousand and of N fertilizers were -2.0 to 0.7 parts per thousand. In 22 groundwater samples from a sand-plain aquifer in east-central Minnesota, B concent rations averaged 0.04 mg/L and delta(11)B values ranged from 2.3 to 41 .5 parts per thousand. Groundwater beneath a hog feedlot and a cultiva ted field where hog manure was applied had B-isotope compositions cons istent with the water containing hog-manure leachate, In a 775-km(2) w atershed with silty-loam soils in southcentral Minnesota: 18 samples o f subsurface drainage from corn (Zea mays L.) and soybean (Glycine maw L. Merr.) fields had average B concentrations of 0.06 mg/L and delta( 11)B values of 5.3 to 15.1 parts per thousand; 27 stream samples had a verage B concentrations of 0.05 mg/L and delta(11)B values of 1.0 to 1 9.0 parts per thousand; and eight groundwater samples had average B co ncentrations of 0.09 mg/L and delta(11)B values of -0.3 to 23.0 parts per thousand. Values of delta(11)B and B concentrations, when plotted against one another, define a curved miro ng trend that suggests subsu rface drainage and stream water contain mixtures of B From shallow and deep groundwater.