Nonexchangeable K constitutes a slowly available reserve that may significantly influence K fertility of soils. Laboratory and greenhouse experiments were conducted to characterize the K supply and nonexchangeable K -release kinetics in 10 calcareous soils using 0.01 M CaCl 2 and 0.01 M oxalic acid extractions. Total K uptake by wheat (Triticum aestivum L.) grown in the greenhouse was used to measure plantavailable K . The release of K was characterized by an initial fast rate followed by a slower rate. The nonlinear relationship in the early stages of the K release may be attribu-ted to the edge sites, and release of K from interlayer exchange sites may be responsible for the second part of the K release. Kinetics of K release was described best with power function, which showed the best fit of the four models tested. Parameters of kinetics models in 0.01 M CaCl 2 were significantly related to K uptake by wheat. Potassium release was also correlated to initial NH 4 OAc-extratable K and to HNO 3 -extractable K .

Nitrogen (N) leaching has become a matter of worldwide concern. The objectives of this study were: (1) to use soil columns to investigate the leaching of nitrate ([Formula: see text]), ammonium ([Formula: see text]), and nitrite ([Formula: see text]) from calcareous soils that had received an average of 200 kg(-1) N ha(-1) year(-1) for the previous 30 years and (2) to determine the relationship between soil properties and [Formula: see text], [Formula: see text], and [Formula: see text] leaching. The soils used in this study ranged in texture from clay to sandy loam. Leaching experiments were conducted under saturation conditions and consisted of the collection of 1,047-2,524 mL of leachate (12 pore volumes (PVs)), which was equivalent to 534-1,286 mm from rainfall or irrigation. Losses of [Formula: see text] ranged from 62 to 437 kg ha(-1), while losses of [Formula: see text] and [Formula: see text] ranged from 2.5 to 19.3 kg ha(-1) and 0.1 to 10.6 kg ha(-1), respectively. Leaching rates differed between soil samples. The initial and secondary rate of [Formula: see text] leaching was determined using an exponential model, and it ranged from 2.8 to 14.7 mg kg(-1) PV(-1) and 0.11 to 0.32 mg kg(-1) PV(-1). Greater leaching rates in the initial period could be due to leaching of [Formula: see text] in solution, while the secondary leaching might be attributable to the diffusion-controlled transfer of [Formula: see text] between mobile and immobile liquid phases. Analysis of variance indicated that the effects of soil type on total [Formula: see text] leaching were highly significant (p < 0.001). The results showed that soil [Formula: see text] concentration was positively correlated with the peak concentration of [Formula: see text] (r = 0.86; p < 0.01) and the total [Formula: see text] leached (r = 0.93; p < 0.01). In addition, the total [Formula: see text] leached was positively correlated with silt (r = 0.67; p < 0.05), clay (r = 0.61; p < 0.05), and pH (r = 0.77; p < 0.01), which suggests that soil parameters might be useful indicators of [Formula: see text] and [Formula: see text] leaching from calcareous soils. Nitrate leaching from soils could threaten groundwater supplies, so possible strategies for minimizing [Formula: see text] leaching losses may need to be considered.

No abstract

The potential for groundwater and surface water pollution by nutrients in organic residues, primarily nitrogen (N) and base cations (K+, Na+, Ca2+, Mg2+), is a consideration when applying such residues to land. In this study, we used a laboratory column leaching procedure to examine the leaching of N, K+, Na+, Ca2+ and Mg2+ in soils treated with two types of raw organic residues (poultry manure and potato residues) and one municipal waste compost, which are currently recycled on agricultural land in Iran. Each organic residue was thoroughly mixed with two different soils (sandy loam and clay) at the rate of 3%. Soil columns were leached at 4-d intervals for 92 d with distilled water, and effluents were analysed for pH, EC, nitrate (NO3(-)-N), ammonium (NH4(+)-N) K+, Na+, Ca2+ and Mg2+. The results indicated that the amounts of NO3(-)-N and NH4(+)-N leached from the poultry manure and potato residues could represent very important economic losses of N and pose an environmental threat under field conditions. The sandy loam soil amended with poultry manure lost the highest amount of NO3(-)-N (206.4 kg ha(-1)), and clay soil amended with poultry manure lost the highest amounts of NH4(+)-N (454.3 kg ha(-1)). The results showed that a treatment incorporating 3% of municipal waste compost could be used without negative effects to groundwater N concentration in clay soil. Significant amounts of K+, Na+, Ca2+, and Mg2+ were leached owing to the application of poultry manure, potato and municipal waste compost to soils. There was a positive relationship between K+, Na+, Ca2+, and Mg2+ with NO3(-)-N and NH4(+)-N leached in soils. Analysis of variance detected significant effects of amendment, soil type and time on the leaching NO3(-)-N, NH4(+)-N, K+, Na+, Ca2+ and Mg2+.

The traditional drinking water purification process is inefficient in removing nitrate significantly. Adsorption can be the most practical method for the removal of nitrate from drinking water. In this study, novel MgO, CeO2, and ZnO nanoparticles (NPs) were utilized for nitrate removal. The MgO, CeO2, and Zn NPs were characterized by Fourier transform infrared spectrometry (FT‐IR), scanning electron microscopy‐energy disperse X‐ray (SEM‐EDX), and X‐ray diffractometer (XRD) analysis. The efficiency of nitrate removal was examined through batch adsorption experiments. The influence of various parameters was studied, namely pH (3–8), temperature (15–40°C), time (10–1440 min), and liquid/solid weight ratio (L/S =25 mL/0.025 g). The optimum conditions from mentioned parameters were used in isotherm experiments with initial nitrate concentration (22–220 mg/L). The adsorption kinetics and isotherm data obeyed well Pseudo‐second‐order and linear and Freundlich models, indicating the multi layer‐chemisorption of nitrate ions. The maximum adsorption capacities of nitrate (N‐ NO3−1) calculated by final point of isotherm experiments were 86.4 mg/g for MgO, 57.6 mg/g for ZnO, and 58.6 mg/g for CeO2. The thermodynamic parameters ( ΔG°, Δ H °, ΔS°) were evaluated. From the thermodynamic parameters, it is suggested that the adsorption of nitrate on NPs followed the endothermic and spontaneous processes. The desorption potential of MgO, CeO2, and ZnO also showed the stability and reusability. Our findings also revealed that among studied NPs from this study and literature MgO NPs is potentially the best adsorbent for removal of nitrate from aqueous solutions. © 2018 American Institute of Chemical Engineers Environ Prog, 37: 1901–1907, 2018