JWSS - Journal of Water and Soil Science

Water and soil pollution with heavy metals has become a worldwide environmental issue. Therefore, development of efficient and low-cost methods for removal of metals from water or metal stabilization in soil has been identified as priority research areas. Biochar, produced from plant biomass and agricultural wastes, has recently been used to remove heavy metals from aqueous solutions as an effective sorbent. In this study, biochars were made from pyrolysis of palm tree residues at different temperatures of 200, 400 and 600 °C. The prepared biochars were then used to remove Ni from aqueous solutions in batch systems without pH adjustment and with pH adjustment at 7. To investigate Ni sorption rate, kinetic experiments were also carried out at a Ni concentration of 10 mg/L. The results of kinetic tests showed that the biochar prepared at 600 °C had more Ni sorption rate with equilibration time of about 5 h. Power function and Elovich models were the best equations fitted the kinetic data. Langmuir and Freundlich isotherms described sorption of Ni on the sorbents very well. According to the Langmuir model predictions, the biochar produced at 600 °C and the palm raw residues had highest and the lowest capacity to sorb Ni from the solution, respectively, and the biochars produced at 200°C and 400°C were intermediate in this respect. Both the capacity and affinity of the biochars for Ni sorption increased with pH. Overall, under the experimental conditions applied in this study, the biochar prepared at 600 °C showed the highest efficiency for Ni removal from aqueous solution.

Growing concerns about water pollution and its potentially harmful effects on human being have stimulated serious efforts to develop reliable biological monitoring techniques. The bioluminescent analysis is one of the most promising approaches for the biomonitoring of the environment, due to the sensitivity of the luminescent system to even micro quantities of the pollutants. The aim of the current study was to assess the petroleum compounds toxicity using Vibrio fischeri bacterium. The growth pattern of the bacterium was determined in photobacterium broth using the optical density measurement at 600 nm, which showed the optimum growth time of 16-18 hours after inoculation. In this research, the effects of environmental parameters such as temperature, pH and various concentrations of oil on the growth and luminescence of Vibrio fischeri were examined. The results revealed that the optimum growth conditions of the bacterium after 16 hours included the temperature of 25 °C and pH 7. Besides, the growth and luminescence intensity of Vibrio fischeri were a function of total petroleum hydrocarbon concentrations in the medium, which were significantly reduced in oil concentrations by more than 4% w/v. Therefore, the Vibrio fischeri could, therefore, have the potential for monitoring of petroleum pollutants in the aqueous media.

One of the key factors in agricultural production is the availability of sufficient and usable nutrients for plant growth, and among these, nitrogen plays a particularly important role. The waste of nitrogen fertilizers due to the low efficiency of using fertilizers has caused environmental problems such as pollution of surface and groundwater by nitrate or ammonium. In this study, the influence of fertigation as a combination of urea, ammonium nitrate, natural zeolite of Semnan (CP), and modified zeolite by surfactant (SMZ) in the reduction of waste and manure fertilizer was evaluated. Two separate experiments with a completely randomized design with three replications were used for loam soil columns. Treatments consisted of four levels of zeolite application (0, 4, 8, and 16 g/Kg) and a fertilization level with a concentration of 60 mg per liter nitrate applied at three fertigations during six irrigations. In the first part of the study, the role of nitrogen fertilizers in fertigation as a combination of urea and ammonium nitrate (UAN) for ordinary soil was examined to reduce the concentration of nitrate and ammonium in the drainage water, and the results were compared with one of the fertigation applications. The results showed that the loss of fertilizer in the form of nitrate was reduced by 40 percent for the UAN treatment during the first period of fertigation. Since the results of the first part of the experiment showed that the concentration of ammonium nitrate does not reduce to the same level as drinking water, in the second part of the experiment, the soil amendments were used. The measured nitrate removal showed that the highest nitrate removal belonged to the soil mixed with 16 g/kg of modified zeolite in the surface layer of soil (SM16) treatment, and it was equivalent to 90 percent. The highest ammonium removal belonged to the soil mixed with 16 g/kg of natural zeolite in the surface layer of soil (CP16) treatment, and it was 85 percent. Therefore, the use of fertigation as a combination of nitrogen fertilizers with soil amendments for conditions where there is a potential for groundwater pollution by nitrate leaching is recommended.