A phospho-compost biological-based approach increases phosphate rock agronomic efficiency in faba bean as compared to chemical and physical treatments

Under arid and semi-arid conditions, direct application of phosphate rock (PR) as a source of phosphorus (P) for crop production is likely influenced by agricultural practices and soil properties. Different approaches could be used to improve the agronomic efficiency of low-grade PR over a wider range of soils and crops. In this study, biological, physical, and chemical treatments of low-grade Moroccan PR were investigated and compared through agronomic trials on faba bean grown under alkaline soil conditions. The physical treatment was based on blending PR with triple superphosphate (TSP) at 75:25 and 50:50 ratios, the biological treatments involved co-application of PR with compost at 50:50 ratio and phospho-compost elaborated from PR (20%), sewage sludge (46%), and wheat residues (34%), while the chemical treatment was obtained by a 30% acidulation of PR by phosphoric acid. Control treatments consisting of zero P application (control), PR alone, and TSP alone were considered to assess the effectiveness of the abovementioned techniques to improve PR agronomic efficiency. A pot experiment was conducted in sandy soil (Jorf Lasfar, central Morocco) for 60 days in a completely randomized design considering eight treatments. All treatments, except the control, were amended with 52 mg kg^?1 of P from different PR-based fertilizers before sowing. At the flowering stage (60-day-old plants), results indicated that all PR treatments significantly improved plant growth, root nodulation, and nutrient uptake compared to the control. The relative agronomic efficiency of pretreated PR was significantly higher with phospho-compost treatment (86%) than the partially acidulated PR (78%) or the PR/TSP blend 50:50 (64%). Likewise, P uptake, P use efficiency, number of root nodules, and N uptake all were improved under PR treatments. Our finding revealed that the biological technique based on phospho-compost yielded better compared to chemical and physical treatments.

     

Behavioral and metabolic effects of sublethal doses of two insecticides,chlorpyrifos and methomyl,in the Egyptian cotton leafworm, <Emphasis Type="Italic">Spodoptera littoralis</Emphasis> (Boisduval) (Lepidoptera: Noctuidae)

Insecticides have long been used as the main method in limiting agricultural pests, but their widespread use has resulted in environmental pollution, development of resistances, and biodiversity reduction. The effects of insecticides at low residual doses on both the targeted crop pest species and beneficial insects have become a major concern. In particular, these low doses can induce unexpected positive (hormetic) effects on pest insects, such as surges in population growth exceeding what would have been observed without pesticide application. Methomyl and chlorpyrifos are two insecticides commonly used to control the population levels of the cotton leafworm Spodoptera littoralis, a major pest moth. The aim of the present study was to examine the effects of sublethal doses of these two pesticides, known to present a residual activity and persistence in the environment, on the moth physiology. Using a metabolomic approach, we showed that sublethal doses of methomyl and chlorpyrifos have a systemic effect on the treated insects. We also demonstrated a behavioral disruption of S. littoralis larvae exposed to sublethal doses of methomyl, whereas no effects were observed for the same doses of chlorpyrifos. Interestingly, we highlighted that sublethal doses of both pesticides did not induce a change in acetylcholinesterase activity in head of exposed larvae.     

Field evaluation of a model for predicting nitrogen losses from drained lands

The N simulation model, DRAINMOD-N II, was field-tested using a 6-yr data set from an artificially drained agricultural site located in eastern North Carolina. The test site is on a nearly flat sandy loam soil which is very poorly drained under natural conditions. Four experimental plots, planted to a corn (Zea mays)-wheat (Triticum aestivum L.)-soybean (Glycine max.) rotation and managed using conventional and controlled drainage, were used in model testing. Water table depth, subsurface drainage, and N concentration in drain flow were measured and meteorological data were recorded continuously. DRAINMOD-N II was calibrated using the data from one plot; data sets from the other three plots were used for model validation. Simulation results showed an excellent agreement between observed and predicted nitrate-nitrogen (NO(3)-N) losses in drainage water over the 6-yr period and a reasonable agreement on an annual basis. The agreement on a monthly basis was not as good. The Nash-Sutcliffe modeling efficiency (EF) for monthly predictions was 0.48 for the calibration plot and 0.19, 0.01, and -0.02 for the validation plots. The value of the EF for yearly predictions was 0.92 for the calibration plot and 0.73, 0.62, and -0.10 for the validation plots. Errors in predicting cumulative NO(3)-N losses over the 6-yr period were remarkably small; -1.3% for the calibration plot, -8.1%, -2.8%, and 4.0% for the validation plots. Results of this study showed the potential of DRAINMOD-N II for predicting N losses from drained agricultural lands. Further research is needed to test the model for different management practices and soil and climatological conditions.     

Kinetic degradation of the pollutant guaiacol by dark Fenton and solar photo-Fenton processes

This work is first intended to optimize the experimental conditions for the maximum degradation of guaiacol (2-methoxyphenol) by Fenton’s reagent, and second, to improve the process efficiency through the use of solar radiation. Guaiacol is considered as a model compound of pulp and paper mill effluent. The experiments were carried out in a laboratory-scale reactor subjected or not to solar radiation. Hydrogen peroxide solution was continuously introduced into the reactor at a constant flow rate. The kinetics of organic matter decay was evaluated by means of the chemical oxygen demand (COD) and the absorbance measurements. The experimental results showed that the Fenton and solar photo-Fenton systems lead successfully to 90% elimination of COD and absorbance at 604 nm from a guaiacol solution under particular experimental conditions. The COD removal always obeyed a pseudo-first-order kinetics. The effect of pH, temperature, H₂O₂ dosing rate, initial concentration of Fe²⁺, and initial COD was investigated using the Fenton process. The solar photo-Fenton system needed less time and consequently less quantity of H₂O₂. Under the optimum experimental conditions, the solar photo-Fenton process needs a dose of H₂O₂ 40% lower than that used in the Fenton process to remove 90% of COD.     

Does irrigation with reclaimed water significantly pollute shallow aquifer with nitrate and salinity? An assay in a perurban area in North Tunisia

In Tunisia, reclaimed water is increasingly used for irrigation in order to mitigate water shortage. However, few studies have addressed the effect of such practice on the environment. Thus, we attempted in this paper to assess the impact of irrigation with reclaimed water on the nitrate content and salinity in the Nabeul shallow aquifer on the basis of satellite images and data from 53 sampled wells. Ordinary and indicator kriging were used to map the spatial variability of these groundwater chemical parameters and to locate the areas where water is suitable for drinking and irrigation. The results of this study have shown that reclaimed water is not an influential factor on groundwater contamination by nitrate and salinity. Cropping density is the main factor contributing to nitrate groundwater pollution, whereas salinity pollution is affected by a conjunction of factors such as seawater interaction and lithology. The predictive maps show that nitrate content in the groundwater ranges from 9.2 to 206 mg/L while the electric conductivity ranges from 2.2 to 8.5 dS/m. The high-nitrate concentration areas underlie sites with high annual crop density, whereas salinity decreases gradually moving away from the coastline. The probability maps reveal that almost the entire study area is unsuitable for drinking with regard to nitrate and salinity levels. Appropriate measures, such as the elaboration of codes of good agricultural practices and action programs, should be undertaken in order to prevent and/or remediate the contamination of the Nabeul shallow aquifer.     

Transboundary Pollution and Absorptive Capacity

The impact of the investment in absorptive capacity on transboundary pollution is studied by considering two countries, each of them regulating a firm. Firms can invest in inventive research and in absorptive research to lower their pollution intensity. The absorptive research enables a firm to capture part of the inventive research made by the other one. We show that by means of adequate emission taxes, original and absorptive research and development (R&D) subsidies, regulators can reach the non-cooperative social optimum. Interestingly, we show that the investment in absorptive research enables non-cooperating regulators to better internalize transboundary pollution. The higher is the learning parameter of absorption, the greater is the proportion of transboundary pollution internalized. Therefore, it is recommended for the international community to make the patent laws more flexible and enabling learning from the research made by others more interesting. Moreover, the investment in absorptive R&D may lead to multiple equilibria necessitating non-cooperating countries to coordinate on an equilibrium, which constitutes an incentive for them to cooperate.     

Ecotoxicological impact assessment of some heavy metals and their distribution in some fractions of mangrove sediments from Red Sea, Egypt

The total and fraction concentrations of heavy metals (Mn, Cu, Ni, Pb, Co, and Cd) were analyzed in some sediment fractions (Φ2, Φ3, Φ4, Φ5) of selected mangrove ecosystems collected from the Egyptian Red Sea shoreline. The results revealed that manganese had the highest mean value (133?±?97 mg/kg) followed by copper (49.9?±?46.0 mg/kg), nickel (28.1?±?11.8 mg/kg), lead (19?±?13 mg/kg), cobalt (6.7?±?4.0 mg/kg), and cadmium (3.327?±?1.280 mg/kg). The concentrations of heavy metals in the different sediment fractions showed that there was a preferential accumulation of Cu, Co, Mn, and to a lesser degree Cd in the silt and clay fractions rather than in the sand-sized. The sediment quality was performed by using some sediment quality guidelines. Additionally, the contamination and the risk assessment of these heavy metals were achieved by different methods including, potential ecological risk index, contamination factor, pollution load index, and geoaccumulation index. According to the Sediment Quality Guidelines comparisons, the concentrations of Mn and Pb were low and showed no possibility of detrimental effects on the local environment. The levels of Cu and Ni were high, however, could not be considered to present serious threat to the mangrove ecosystem. The data showed that the mangrove ecosystems were affected by the Cd risk.     

Removal of estrogenic activity of natural and synthetic hormones from a municipal wastewater: efficiency of horseradish peroxidase and laccase from Trametes versicolor

Some researches studied the removal of steroid estrogens by enzymatic treatment, however none verified the residual estrogenicity after the enzymatic treatment at environmental conditions. In this study, the residual estrogenic activities of the key natural and synthetic steroid estrogens were investigated following enzymatic treatment with horseradish peroxidase (HRP) and laccase from Trametes versicolor. Synthetic water and municipal wastewater containing environmental concentrations of estrone, 17beta-estradiol, estriol, and 17alpha-ethinylestradiol were treated. Liquid chromatography-mass spectrometry analysis demonstrated that the studied steroid estrogens were completely oxidized in the wastewater reaction mixture after a 1-h treatment with either HRP (8-10 U ml(-1)) or laccase (20 U ml(-1)). Using the recombinant yeast assay, it was also confirmed that both enzymatic treatments were very efficient in removing the estrogenic activity of the studied steroid estrogens. The laccase-catalyzed process seemed to present great advantages over the HRP-catalyzed system for up-scale applications for the treatment of municipal wastewater.