Nitrate Sorption in an Agricultural Soil Profile

Abstract

Increasing concentrations of NO 3 − 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 NO 3 − sorption capacity of soils. In this project we measured NO 3 − sorption by a profile of an isohumic soil from Chott Meriem, Tunisia. Soil samples were collected from four soil depths (0-25, 25-60, 60-90, and 90-120 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 NO 3 − sorption were investigated. In general, the results suggested that NO 3 − was weakly retained by the Chott Meriem soil profile. The quantity of NO 3 − 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 mg L −1 experimental data were fitted to both Freundlich and Langmuir isotherm sorption models. The results indicated that Freundlich model was better for describing NO 3 − sorption in this soil profile.

Nitrate Adsorption on Clay Kaolin: Batch Tests

“…A number of researchers [7,8,[29][30][31] reported that two nonlinear adsorption isotherms, namely, Langmuir and Freundlich, are the best models to explain the trend of adsorption based on the essence of absorbents saturated with adsorbate after enough contact time.…”

“…However, the increasing rate of nitrate adsorption decelerated with further increase in nitrate concentration. This behavior is due to the increase in the driving force of the concentration gradient, as further increase in the initial nitrate concentration overcomes the limitations of low adsorption by absorbent [7]. Such phenomenon is common in a batch test with either constant adsorbent dose or varying initial adsorbate concentration or vice versa [34].…”

“…Since 1970s nitrate leaching to subsoil has become an important environmental quality and human health issue, especially due to high use of nitrogen as nutrient in agriculture [3][4][5]. Inorganic nitrogen is used as an essential fertilizer in intensive agriculture to produce sufficient food for growing population and food security, a substantial part of which finally infiltrates into subsurface and contaminates soil and groundwater [6][7][8]. Nitrate itself is relatively nontoxic, but nitrite derived by the reduction of nitrate, which can cause various human health problems such as methemoglobinemia, liver damage, and even cancers [9].…”

Decadal Delays in Groundwater Recovery from Nitrate Contamination Caused by Low O2 Reduction Rates

“…The transport of nitrate in groundwater under oxic redox conditions can be assumed to be conservative since nitrate shows no or only little sorption effects on the aquifer matrix and does not precipitate as mineral phase (Hamdi et al, ; Harper, ; Singh & Kanehiro, ). In such oxic aquifers, the residence time of nitrate in groundwater may vary from less than 1 year to several decades or even centuries depending on the apparent mean transit times (MTT) of groundwater (Koh et al, ; Sebilo et al, ; Wassenaar et al, ).…”

Utilization of Anion Exchange Resins: Amberlyst A21 for Sulfate Reduction in Drinking Ground Water and its Characterization

“…Langmuir and Freundlich are the best models to explain the trend of adsorption based on the essence of absorbents saturated with adsorbate after enough contact time. (33), (34), (35), (36 279 absorbance by spectrophotometer (using kits).And the data was fitted into the following isotherms: Langmuir, Freundlich, which are shown in Fig (9a, b).…”