No abstract

Constant use of treated wastewater (TWW) for irrigation over prolonged periods may cause buildup of heavy metals up to toxic levels for plants and animals, and entails environmental hazards in different aspects. However, application of TWW on agricultural land might be an effective and sustainable strategy in arid and semi-arid countries where fresh water resources are under great pressure, as long as potential harmful effects on the environment including soil, plants, and fresh water resources, and health risks to humans are minimized. The aim of this study was to assess the effect of deep emitters on limiting potential heavy metal accumulation in soils and grains, and health risk under drip irrigation with treated municipal wastewater. A field experiment was conducted according to a split block design with two treatments (fresh and wastewater) and three sub-treatments (0, 15, and 30 cm depth of emitters) in four replicates on a sandy loam Calcic Argigypsids, in Esfahan, Iran. The annual rainfall is about 123 mm, mean annual ETo is 1457 mm, and the elevation is 1590 m above sea level. A two-crop rotation of wheat (Triticum spp.) and corn (Zea mays) was established on each plot with wheat growing from February to June and corn from July to September. Soil samples were collected before planting and after harvesting for each crop in each year. Edible grain samples of corn and wheat were collected at harvest. Elemental concentrations (Cu, Zn, Cd, Pb, Cr, Ni) in soil and grains were determined using an atomic absorption spectrophotometer. Results showed that the concentrations of heavy metals in the wastewater-irrigated soils were not significantly different (P > 0.05) compared with the freshwater-irrigated soils. No significant difference (P > 0.05) in heavy metal content in soil between different depths of emitters was found. A pollution load index (PLI) showed that there was no substantial buildup of heavy metals in the wastewater-irrigated soils compared to the freshwater-irrigated soils. Cu, Pb, and Zn concentrations in wheat and corn grains were within the permissible US Environmental Protection Agency (EPA) limits, but concentrations of Cd (in wheat and corn) and Cr (in corn) were above the safe limits of the EPA. In addition, concentrations of Ni in wheat and corn seeds were several folds higher than the EPA standards. A health risk index (HRI) which is usually adopted to assess the health risk to hazard materials in foods showed values higher than 1 for Cd, particularly for wheat grain (HRI >2.5). Results also showed that intake of Cu through consumption of edible wheat grains posed a relatively high potential health risk to children (HRI >1.4), whereas children might also be exposed to health risk from Cd and Cr from corn grains (HRI >1.4). Based on aforementioned results, it can be concluded that the emitter depth in drip irrigation does not play a significant role in the accumulation of heavy metals from TWW in our sandy loam soil. Although their accumulation in the soil was limited and similar to using f...

Using basic soil properties could save time and costs in determining field capacity (FC) and permanent wilting point (PWP). The objectives of this study were to investigate the relationship between FC and PWP and basic soil properties, develop two new equations for estimating FC and PWP, and evaluating their performance as compared to some existing pedotransfer functions (PTFs) in predicting FC and PWP. For this purpose, 210 soil samples of UNSODA dataset and 45 soil samples of HYPRES dataset were used for development and validation of the PTF, respectively. Graphical exploration of relations between soil texture component, geometric mean particle-size diameter (dg), bulk density (BD), and organic matter (OM) with FC and=or PWP showed that relations of FC was nonlinearly related to percentage of clay (positive) and dg (negative) and relations of PWP was linearly and nonlinearly related to percentage of clay (positive) and dg (negative), respectively. Based on standardized independent variable weight (W), dg showed the highest influence on FC (W ¼ 0.81), followed by percentage of clay (W ¼ 0.70), OM and BD (W ¼ 0.49). PWP was primarily affected by percentage of clay (W ¼ 0.89) and dg (W ¼ 0.64), whereas BD and OM with Wof 0.30 were less effective. The two new functions suggested and evaluated for predicting FC and PWP had root mean squares error (RMSE) of 0.06 and 0.02 m 3 m À3 , geometric mean error (GMER) 1.03 and 1.10 m 3 m À3 and Akaike's information criterion (AIC) of À262 and À349, respectively. As such, their prediction performance was higher than that of other FC and PWP PTFs found in literature.