Phosphorus removal from aqueous solution using modified walnut and almond wooden shell and recycling as soil amendment.

Modified walnut wooden shell (MWWS) and almond wooden shell (MAWS) as novel anion exchangers were used to remove phosphorus (P) from aqueous solution. The raw and modified agricultural wastes were characterized using total N, total P, FT-IR spectra, SEM, BET, and EXD analysis. The effect of different parameters such as pH (4 to 8), contact time (5 to 600 min), and adsorbent dosage (1 to 8 g L-1) on P adsorption was investigated. Adsorption of P onto MWWS and MAWS was studied using the batch technique with different concentration of P (5 to 200 mg L-1) at 25 ± 2 °C. The P adsorption isotherms were fitted with the Freundlich and Langmuir equations. The k and n values were 1.57 mg g-1 and 1.88 for MWWS and 1.91 mg g-1 and 2.24 for MAWS, respectively. The maximum P adsorption capacities for MWWS and MAWS were 22.73 and 14.71 mg g-1, respectively. The desorption-regeneration experimental results indicated about 4% and 3% reductions in MWWS and MAWS P adsorption efficiency after four consecutive regeneration cycles, respectively. The data well fitted with Pseudo-second-order kinetic model (R2 ≥ 0.99), indicating that chemical interactions dominate the P adsorption process. Incubation studies showed the rate of P release in treated soil with P-loaded modified biosorbents was higher than control. Therefore, the MWWS and MAWS can potentially be used as an excellent adsorbent in remediation of contaminated waters by P and then recycled to soil.

Leaching of nitrogen from calcareous soils in western Iran: a soil leaching column study.

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.

Leaching of nitrogen and base cations from calcareous soil amended with organic residues.

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+.