Nitrate Sorption in an Agricultural Soil Profile

Abstract

Increasing concentrations of <svg style="vertical-align:-3.25793pt;width:39.275002px;" id="M1" height="15.8375" version="1.1" viewBox="0 0 39.275002 15.8375" width="39.275002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.55)"><path id="x4E" d="M719 650v-28q-43 -2 -62 -15t-22 -44q-6 -47 -6 -169v-403h-31l-426 524h-2v-251q0 -111 6 -169q4 -37 24 -50.5t72 -16.5v-28h-237v28q45 2 64.5 16t23.5 49q6 62 6 171v220q0 54 -3 68.5t-17 32.5q-16 19 -34.5 26.5t-54.5 10.5v28h147l418 -502h3v246q0 117 -7 166&#xA;q-4 34 -24.5 47t-73.5 15v28h236z" /></g><g transform="matrix(.017,-0,0,-.017,12.574,11.55)"><path id="x4F" d="M381 665q131 0 226.5 -93t95.5 -239q0 -158 -96 -253t-238 -95q-137 0 -231 95t-94 238q0 142 92.5 244.5t244.5 102.5zM359 629q-89 0 -151 -74.5t-62 -208.5q0 -141 69 -233t175 -92q90 0 150.5 74t60.5 211q0 152 -69 237.5t-173 85.5z" /></g> <g transform="matrix(.012,-0,0,-.012,25.275,15.637)"><path id="x33" d="M285 378v-2q65 -13 102 -54.5t37 -97.5q0 -57 -30.5 -104.5t-74 -75t-85.5 -42t-72 -14.5q-31 0 -59.5 11t-40.5 23q-19 18 -16 36q1 16 23 33q13 10 24 0q58 -51 124 -51q55 0 88 40t33 112q0 64 -39 96.5t-88 32.5q-29 0 -64 -11l-6 29q77 25 118 57.5t41 84.5&#xA;q0 45 -26.5 69.5t-68.5 24.5q-67 0 -120 -79l-20 20l43 63q51 56 127 56h1q66 0 107 -37t41 -95q0 -42 -31 -71q-22 -23 -68 -54z" /></g><g transform="matrix(.012,-0,0,-.012,31.6,3.4)"><path id="x2212" d="M535 230h-483v50h483v-50z" /></g> </svg> in surface water and groundwater can cause ecological and public health effects and has come under increased scrutiny by both environmental scientists and regulatory agencies. For many regions though, including the Sahel of Tunisia, little is known about the <svg style="vertical-align:-3.25793pt;width:39.275002px;" id="M2" height="15.8375" version="1.1" viewBox="0 0 39.275002 15.8375" width="39.275002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.55)"><use xlink:href="#x4E"/></g><g transform="matrix(.017,-0,0,-.017,12.574,11.55)"><use xlink:href="#x4F"/></g> <g transform="matrix(.012,-0,0,-.012,25.275,15.637)"><use xlink:href="#x33"/></g><g transform="matrix(.012,-0,0,-.012,31.6,3.4)"><use xlink:href="#x2212"/></g> </svg> sorption capacity of soils. In this project we measured <svg style="vertical-align:-3.25793pt;width:39.275002px;" id="M3" height="15.8375" version="1.1" viewBox="0 0 39.275002 15.8375" width="39.275002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.55)"><use xlink:href="#x4E"/></g><g transform="matrix(.017,-0,0,-.017,12.574,11.55)"><use xlink:href="#x4F"/></g> <g transform="matrix(.012,-0,0,-.012,25.275,15.637)"><use xlink:href="#x33"/></g><g transform="matrix(.012,-0,0,-.012,31.6,3.4)"><use xlink:href="#x2212"/></g> </svg> sorption by a profile of an <i >iso-humic </i>soil from Chott Meriem, Tunisia. Soil samples were collected from four soil depths (0&#x2013;25, 25&#x2013;60, 60&#x2013;90, and 90&#x2013;120&#x2009;cm) on 1 June 2011, and their sorption capacity was determined using batch experiments under laboratory conditions. The effects of contact time, the initial concentration, and the soil-solution ratio on <svg style="vertical-align:-3.25793pt;width:39.275002px;" id="M4" height="15.8375" version="1.1" viewBox="0 0 39.275002 15.8375" width="39.275002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.55)"><use xlink:href="#x4E"/></g><g transform="matrix(.017,-0,0,-.017,12.574,11.55)"><use xlink:href="#x4F"/></g> <g transform="matrix(.012,-0,0,-.012,25.275,15.637)"><use xlink:href="#x33"/></g><g transform="matrix(.012,-0,0,-.012,31.6,3.4)"><use xlink:href="#x2212"/></g> </svg> sorption were investigated. In general, the results suggested that <svg style="vertical-align:-3.25793pt;width:39.275002px;" id="M5" height="15.8375" version="1.1" viewBox="0 0 39.275002 15.8375" width="39.275002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.55)"><use xlink:href="#x4E"/></g><g transform="matrix(.017,-0,0,-.017,12.574,11.55)"><use xlink:href="#x4F"/></g> <g transform="matrix(.012,-0,0,-.012,25.275,15.637)"><use xlink:href="#x33"/></g><g transform="matrix(.012,-0,0,-.012,31.6,3.4)"><use xlink:href="#x2212"/></g> </svg> was weakly retained by the Chott Meriem soil profile. The quantity of <svg style="vertical-align:-3.25793pt;width:39.275002px;" id="M6" height="15.8375" version="1.1" viewBox="0 0 39.275002 15.8375" width="39.275002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.55)"><use xlink:href="#x4E"/></g><g transform="matrix(.017,-0,0,-.017,12.574,11.55)"><use xlink:href="#x4F"/></g> <g transform="matrix(.012,-0,0,-.012,25.275,15.637)"><use xlink:href="#x33"/></g><g transform="matrix(.012,-0,0,-.012,31.6,3.4)"><use xlink:href="#x2212"/></g> </svg> sorption increased with depth, contact time, initial concentration, and soil-solution ratios. To evaluate the sorption capacities of the soil samples at concentrations ranging between 25 and 150&#x2009;mg&#x2009;L<sup >&#x2212;1</sup> experimental data were fitted to both Freundlich and Langmuir isotherm sorption models. The results indicated that Freundlich model was better for describing <svg style="vertical-align:-3.25793pt;width:39.275002px;" id="M7" height="15.8375" version="1.1" viewBox="0 0 39.275002 15.8375" width="39.275002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.55)"><use xlink:href="#x4E"/></g><g transform="matrix(.017,-0,0,-.017,12.574,11.55)"><use xlink:href="#x4F"/></g> <g transform="matrix(.012,-0,0,-.012,25.275,15.637)"><use xlink:href="#x33"/></g><g transform="matrix(.012,-0,0,-.012,31.6,3.4)"><use xlink:href="#x2212"/></g> </svg> sorption in this soil profile.