The relationship between the characteristics of Biochar produced at different temperatures and its impact on the uptake of NO3--N

Background: Nitrogen leaching from agricultural lands is a major threat to groundwater and surface waters. This study investigated the relationship between the characteristics of wheat-straw biochar produced at different temperatures and its impact on the uptake of NO3--N. Methods: Three types of biochar were produced from wheat straw at three different pyrolysis temperatures of 300, 400 and 500°C, and sampling was done 3 times for each biochar. Physical and chemical characteristics of biochar were determined using a variety of methods including specific surface with methylene blue adsorption method, and elemental content with elemental analyzer, and water solubility with standard ASTM (D5029-28) method. Statistical analysis was performed using Freundlich and Langmuir models. Nitrate concentration was measured using a UV-V spectrophotometer with a wavelength of 500 nm. Results: It was indicated that with an increase in biochar pyrolysis temperature from 300 to 500°C, the hydrogen, oxygen and nitrogen in the biochar were significantly decreased (P < 0.05) while the carbon content, surface area, density and water solubility in biochar (P < 0.05) were increased. The results also showed that the maximum nitrate adsorptive capacity of the three types of biochar occurred at pH=6 and contact time of 120 minutes. With increasing the temperature of biochar preparation, the efficiency of biochar nitrate adsorption increased significantly. Conclusion: The present study shows that pyrolysis temperature greatly influences the biochar chemical and physical characteristics, and subsequently nitrate adsorption ability of the biochars. The wheat straw biochar, which is produced at a pyrolysis temperature of 500°C, has the highest adsorption capacity for nitrate. Keywords: Biochar, Nitrates, Adsorptio

INVESTIGATING THE EFFECT OF DIFFERENT HYDRAULIC CROSS SECTIONS OF DENITRIFICATION BEDS ON THE AMOUNT OF EFFLUENT EC

Nitrate loadings from agricultural drainage to surface water resources cause’s serious water quality concerns in many parts of the world. Denitrification bioreactors are suitable option for removing nitrate from agricultural drainage water. The objectives of this study was to investigate the effect of different hydraulic cross sections of denitrification beds on the amount of effluent EC. In this study, three denitrification beds were constructed with a semicircular, triangle and a rectangle cross sections, filled with wood chips of beech tree. Samples were taken from the outlets of all three beds at a depth at 25 and 50 cm from the bottom of the bed for two months. EC of the samples was meassured using EC-meter. After determining the EC of the samples, data were analyzed by T-test and Univariate tests. The results showed that the shape of the cross-section of the denitrification beds and the saturation depth had a significant effect on EC and the amount of EC of the outflow was increased

Evaluation of Phytoremediation Potential and Yield of Helianthus annuus under Sewage Sludge

Many ornamental plants have the ability to extract toxic metals from the soil and are able to store large amounts of metals in their organs with no health problems for humans as they do not enter the human food chain. This study aimed to investigate the effect of sewage sludge application on the performance of Helianthus annuus and to investigate its phytoremediation ability for heavy metals (Pb, Ni and Cd) in soil. This study was carried out with three levels of sewage sludge related to southern Tehran wastewater treatment plant, including 0, 10 and 20 percent by weight of soil in three replications in a completely randomized block design on Helianthus annuus. The results showed that the application of sewage sludge caused a significant increase in the concentration of heavy metals and wet and dry yield of different parts of the flower in the plant. Application of sewage sludge at 20 percent by weight of soil was more suitable for growth index and accumulation of heavy metals in plant in terms of growth index such as wet weight (root 12.03 g and shoot 48.56 g), dry weight (root 1.97 g and shoot 8.69 g), stem diameter (0.78 cm), stem height (19.4 cm) and flower diameter (7.44 cm) as well as concentration of heavy metals Pb (root and shoot 9.09 and 4.35 mg/kg respectively), Ni (root and shoot 3.65 and 2.04 mg/kg respectively) and Cd (root and shoot 0.598 and 0.364 mg/kg respectively). Due to root bioaccumulation factor above 1 and transfer factor less than 1, Helianthus annuus is a plant suitable for the uptake and transfer of heavy metals, which prevents the entry of heavy metals into the shoot parts by a plant stabilization mechanism

Investigation of Nitrate Removal from Zarjoub River Water of Rasht Using a Hybrid Wetland System

With the influx of agricultural, industrial and hospital pollutants into surface and groundwater, human health and other living organisms are facing a serious threat. Zarjoub River is one of the most polluted rivers in the country, which passes through the center of Rasht and all kinds of dangerous pollutants such as nitrate, phosphate and dangerous heavy metals flow into it. Artificial wetlands are one of the low-cost and environmentally friendly wastewater treatment methods that have received a lot of attention today. In this study, the use of artificial wetlands in sequential using three different plant species of phragmites, lemna and vetiver with two different arrangements to remove nitrate in autumn of 2019 and summer of 2020 has been investigated. The results showed that the average percentage of nitrate reduction by two plant treatments was 73% and 68%, and for the control treatment it was 35%, which indicates the effect of plants in wetlands. Also, the result showed that the amount of nitrate reduction from the effluent was directly related to temperature changes and growth status of plants. The results showed that the use of hybrid wetlands can have a good removal efficiency for pollutants compared to their individual use, but the difference in plant arrangement in wetlands, although statistically significant at a probability level of 1%, had little effect on the nitrate removal process on effluent

Growth, Yield, and Water Productivity Responses of Pepper to Sub-Irrigated Planter Systems in a Greenhouse

A sub-irrigated planter (SIP) is a container irrigation technique in which water is supplied to the crop from the bottom, stored in a saturated media-filled reservoir beneath an unsaturated soil, and then delivered by capillary action to the root zone. The aim of this study was to optimize the water management and to assess the performance of this technique in terms of water use efficiency, soil moisture, and solute distribution in comparison with surface irrigation in a Mediterranean greenhouse. The experiment consisted of four SIP treatments, with a constant water level in the bottom reservoir in order to evaluate the effect of two different irrigation salinities (1.2 and 2.2 dS m−1) and two depths of substrate profiles (25 and 15 cm). The results showed that SIP is capable of significantly improving both water-use efficiency and plant productivity compared with surface irrigation. Also, a 24% average reduction in water consumption was observed while using SIP. Moreover, SIPs with a higher depth were recommended as the optimum treatments within SIPs. The type of irrigation method affected the salinity distribution in the substrate profile; the highest salinity levels were registered at the top layers in SIPs, whereas the maximum salinity levels for the surface treatments were observed at the bottom layers. SIPs provide a practical solution for the irrigation of plants in areas facing water quality and scarcity problems

Growth, Yield, and Water Productivity Responses of Pepper to Sub-Irrigated Planter Systems in a Greenhouse

A sub-irrigated planter (SIP) is a container irrigation technique in which water is supplied to the crop from the bottom, stored in a saturated media-filled reservoir beneath an unsaturated soil, and then delivered by capillary action to the root zone. The aim of this study was to optimize the water management and to assess the performance of this technique in terms of water use efficiency, soil moisture, and solute distribution in comparison with surface irrigation in a Mediterranean greenhouse. The experiment consisted of four SIP treatments, with a constant water level in the bottom reservoir in order to evaluate the effect of two different irrigation salinities (1.2 and 2.2 dS m&minus;1) and two depths of substrate profiles (25 and 15 cm). The results showed that SIP is capable of significantly improving both water-use efficiency and plant productivity compared with surface irrigation. Also, a 24% average reduction in water consumption was observed while using SIP. Moreover, SIPs with a higher depth were recommended as the optimum treatments within SIPs. The type of irrigation method affected the salinity distribution in the substrate profile; the highest salinity levels were registered at the top layers in SIPs, whereas the maximum salinity levels for the surface treatments were observed at the bottom layers. SIPs provide a practical solution for the irrigation of plants in areas facing water quality and scarcity problems