Mitigation of climate change impacts on maize productivity in northeast of Iran: a simulation study

Development and evaluation of mitigation strategies are fundamental to manage climate change risks. This study was built on (1) quantifying the response of maize (Zea mays L.) grain yield to potential impacts of climate change and (2) investigating the effectiveness of changing sowing date of maize as a mitigation option for Khorasan Province which is located in northeast of Iran. Two types of General Circulation Models (GCM: (United Kingdom Met Office Hadley Center :HadCM3) and (Institute Pierre Simon Laplace: IPCM4)) and three scenarios (A1B, A2 and B1) at four locations (Mashhad, Birjand, Bojnourd and Sabzevar) employed in this study. Long Ashton Research Station-Weather Generator (LARS-WG) was employed for generating the future climate. The Cropping System Model (CSM)-CERES-Maize was used for crop growth simulation under projected climate conditions. The results showed the simulated grain yields of maize gradually would decrease (from −1% to −39%) during future 100 years compared to baseline under different scenarios and two GCM at all study locations. The simulation results suggested that delayed sowing date from May to June at all study locations, except Sabzevar location is the most effective mitigation option for avoiding thermal stress at end of growth period. In addition, shifting in sowing date to March or April will be beneficial in terms of obtaining higher yields in Sabzevar. Grain yield did not show special trend from north to south of Khorasan Province in the future climate. In general, change of sowing date may be quite beneficial to mitigate climate change impacts on grain yield of maize in northeast of Iran.     

Groundwater-level trends and implications for sustainable water use in the Kabul Basin, Afghanistan

The Kabul Basin, which includes the city of Kabul, Afghanistan, with a population of approximately 4 million, has several Afghan, United States, and international military installations that depend on groundwater resources for a potable water supply. This study examined groundwater levels in the Kabul Basin from 2004 to 2012. Groundwater levels have increased slightly in rural areas of the Kabul Basin as a result of normal precipitation after the drought of the early 2000s. However, groundwater levels have decreased in the city of Kabul due to increasing water use in an area with limited recharge. The rate of groundwater-level decrease in the city is greater for the 2008–2012 period (1.5 meters per year (m/yr) on average) than for the 2004–2008 period (0–0.7 m/yr on average). The analysis, which is corroborated by groundwater-flow modeling and a non-governmental organization decision-support model, identified groundwater-level decreases and associated implications for groundwater sustainability in the city of Kabul. Military installations in the city of Kabul (the Central Kabul subbasin) are likely to face water management challenges resulting from long-term groundwater sustainability concerns, such as the potential drying of shallow water-supply wells. Installations in the northern part of the Kabul Basin may have fewer issues with long-term water sustainability. Groundwater-level monitoring and groundwater-flow simulation can be valuable tools for assessing groundwater management options to improve the sustainability of water resources in the Kabul Basin.     

Determination of ultra-trace amounts of cadmium by ET-AAS after column preconcentration with a new sorbent of modified MWCNTs

The present research reports on the application of modified multiwalled carbon nanotubes as a new, easily prepared, and stable solid sorbent for the column preconcentration of ultra-trace amounts of cadmium in aqueous solution. Multiwalled carbon nanotubes were oxidized with concentrated HNO₃ and modified with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and then were used as a solid phase for the column preconcentration of Cd(II). Elution was carried out with 0.5 mol?L^?1 HNO₃. The amount of eluted Cd(II) was measured using electrothermal atomic absorption spectrometry. Various parameters such as pH, sample and eluent flow rate, eluent concentration, breakthrough volume, and interference of a great number of anions and cations on the retention of analyte on sorbent were studied. Under the optimized conditions, the calibration graph was linear in the range of 0.67 ng?L^?1 to 5.0 μg?L^?1 and the detection limit (3S_b, n?=?7) was 0.14 ng?L^?1 in initial solution. A preconcentration factor of 300 and relative standard deviations of ±3.6 % for seven successive determinations of 3 ng of Cd(II) were achieved. The column preconcentration was successfully applied to the analysis of river water, waste water, and Persian Gulf water sample.     

Heterogeneous photocatalysis for removal of microbes from water

Increasing water pollution by microbes has become a source of serious health concern across the globe. Production of potentially carcinogenic disinfection by-products has marred credibility of traditional water purification techniques like chlorination. Photocatalysis has emerged as a promising alternative technique for the disinfection of water with minimal risk of harmful by-products. The process involves a wide band gap semiconductor material which, upon irradiation of light, produces electrons and holes with high redox potential to degrade organic contaminants and microbes. In this review, we analyze the research trends in photocatalytic inactivation of water borne microorganisms. This report analyzes the major factors that affect the disinfection efficiency using this process. The discussion also includes plausible mechanisms of microbial degradation as well as a kinetic model of the inactivation process. Different approaches, like doping of semiconductors or energy band engineering or plasmon coupling, have been reported for the enhancement and utilization of ambient solar light. Photocatalysis could be a cost-effective and environmentally friendly water purification technique though further research is required to enhance its efficiency with the use of solar light.     

Salicylic acid minimizes nickel and/or salinity-induced toxicity in Indian mustard (Brassica juncea) through an improved antioxidant system

Introduction  

This study was hypothesized that salicylic acid elevates the level of antioxidant system that will protect plants from the stress generated by nickel and/or salinity.     

Application of ANN and ANFIS models for reconstructing missing flow data

Hydrological yearbooks, especially in developing countries, are full of gaps in flow data series. Filling missing records is needed to make feasibility studies, potential assessment, and real-time decision making. In this research project, it was tried to predict the missing data of gauging stations using data from neighboring sites and a relevant architecture of artificial neural networks (ANN) as well as adaptive neuro-fuzzy inference system (ANFIS). To be able to evaluate the results produced by these new techniques, two traditionally used methods including the normal ratio method and the correlation method were also employed. According to the results, although in some cases all four methods presented acceptable predictions, the ANFIS technique presented a superior ability to predict missing flow data especially in arid land stations with variable and heterogeneous data. Comparing the results, ANN was also found as an efficient method to predict the missing data in comparison to the traditional approaches.     

Economic valuation of Shadegan International Wetland,Iran: notes for conservation

Wetlands are among the most productive ecosystems on the earth. They produce various market and non-market goods and services, which have a significant role in human welfare. Despite the great opportunities from sustainable development, wetlands all over the world are under serious threat from a diverse range of non-sustainable activities. One of the major reasons for excessive depletion and the conversion of wetland resources is due to underestimating the non-market values of wetlands during development decisions. Shadegan International Wetland (SIW) in southern Iran is one of these wetland areas that is threatened by undervaluation and overexploitation from commercial activities. This study utilizes the contingent valuation method to estimate the economic benefits of SIW from the view point of peoples’ willingness to pay (WTP). The logit model was defined based on dichotomous choice to measure individuals’ WTP. The estimated mean WTP was US$ 1.74 per household as a onetime donation. This study concludes that the benefits of SIW to society could encourage managers to set priorities to ensure that the health of the ecosystem, its integrity, and its uniqueness would be conserved in a proper manner.     

Hydration of geosynthetic clay liners from clay subsoil under simulated field conditions

Use of Geosynthetic Clay Liners (GCLs) in landfill barrier design has been the focus of recent studies investigating their ability to prevent contaminant transport to groundwater. In this paper, the hydration of two GCL products placed in contact with clay subsoils at different initial moisture contents is described under both isothermal conditions at room temperature, and daily thermal cycles. The rate of hydration of the GCL and its final equilibrium moisture content were significantly influenced by the amount of moisture made available to it through the subsoil. The two types of GCLs were also found to exhibit different hydration behaviors under similar experimental conditions. The study revealed that GCLs undergoing daily thermal cycles absorbed much less moisture over time than the GCLs kept at constant room temperature (ratio 1:4). In comparison with other types of subsoils, the final equilibrium moisture content attained by the GCL from clay subsoil was significantly less than that for sand subsoil.     

Non-users’ trade-off between natural scenery, water quality, ecological functions and biodiversity conservation: a way to preserve wetlands

The inclusion of both non-use values and values placed by non-users provide more reliable results about the real values of wetlands. A choice experiment method was conducted to estimate the willingness to pay for environmental conservation in non-users’ communities adjacent to the Shadegan International Wetland (SIW) in Iran. A random parameter logit (RPL) model was developed to derive the marginal value and compensating surplus of the respondents for five attributes of the non-market values of SIW. The trade-off between five different wetland attributes showed that water quality improvement and biodiversity conservation were the most highly valued attributes. The results demonstrated that about 66 % of non-users were willing to donate money for the contribution in SIW conservation, suggesting that non-users have the potential to contribute to SIW conservation programs.     

The performance of Electro-Fenton oxidation in the removal of coliform bacteria from landfill leachate

Leachate pollution is one of the main problems in landfilling. Researchers have yet to find an effective solution to this problem. The technology that can be used may differ based on the type of leachate produced. Coliform bacteria were recently reported as one of the most problematic pollutants in semi-aerobic (stabilized) leachate. In the present study, the performance of the Electro-Fenton process in removing coliform from leachate was investigated. The study focused on two types of leachate: Palau Borung landfill leachate with low Coliform content (200 MPN/100 m/L) and Ampang Jajar landfill leachate with high coliform content (>24 × 10⁴ MPN/100 m/L). Optimal conditions for the Electro-Fenton treatment process were applied on both types of leachate. Then, the coliform was examined before and after treatment using the Most Probable Number (MPN) technique. Accordingly, 100% removal of coliform was obtained at low initial coliform content, whereas 99.9% removal was obtained at high initial coliform content. The study revealed that Electro-Fenton is an efficient process in removing high concentrations of pathogenic microorganisms from stabilized leachate.