A Box-Behnken design for determining the optimum experimental condition of the fungicide (Vapam) sorption onto soil modified with perlite

In the present study, response surface methodology (RSM) based on the Box-Behnken design (BBD) was employed to investigate the effects of the different operating conditions on the removal of the fungicide (Vapam) onto soil modified with perlite using sorption process. The process parameters such as pH of the fungicide solution (2, 5 and 8), temperature (15, 25 and 35°C), shaking time (2, 13 and 24 h) and the percentage of perlite in the modified soil (0, 2 and 4 %) were investigated using a four-factor-three-level Box-Behnken design at an initial fungicide concentration of C(0) = 1.6 mg/L as a fixed input parameter. A second-order quadratic model suggested the optimum conditions to be as follows: fungicide solution pH of 3.57, temperature of 15°C, shaking time of 3.5 h and 4% of perlite in the modified soil which resulted in the improvement of Vapam sorption. Under optimum conditions, the fungicide (Vapam) removal was predicted 12.88 μg/g by BBD. The confirmatory experiments were conducted and the results revealed that the fungicide removal was 13.14 μg/g which indicated that the predicted and the observed values of response (Vapam removal) were in close agreement. Therefore, the soil modified with perlite holds good potential for Vapam sorption. This is the first report on fungicide Vapam sorption onto soil modified with perlite using statistical experimental design employing response surface methodology.     

Fate of metolachlor under subirrigation in a sandy soil: A lysimeter study

Abstract

A three‐year field lysimeter study was conducted to investigate the role of subirrigation systems in reducing the risk of water pollution from metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methlphenyl)‐N‐(2‐methoxy‐l‐methylethyl)acetamide). Nine large PVC lysimeters, 1 m long x 0.45 m diameter, were packed with a sandy soil. Three water table management treatments, i.e. two subirrigation treatments with constant water table depths of 0.4 and 0.8 m, respectively, and a free drainage treatment in a completely randomized design with three replicates were used. Corn (Zea mays L.) was grown in each lysimeter, and at the beginning of summer of each year metolachlor was applied, at the locally recommended rate of 2.75 kg a.i./ha. Soil and water samples were collected at different time intervals after each natural or simulated rainfall event. Metolachlor was extracted from these samples and analyzed using Gas Chromatography.

Results obtained in this three year study, (1993–1995), lead to the conclusion that metolachlor is quite mobile since it leached to a depth of 0.85 m below the soil surface quite early in the growing season. Metolachlor concentrations decreased with depth as well as with time. The shallower water table in the 0.4 m subirrigation treatment showed less residues in the soil solution than that of other treatments. However, a mass balance study, supported by an independent laboratory investigation, shows that water table management, statistically, has no significant effect on the reduction of metolachlor residues in sandy soils.     

Uptake and distribution of phenanthrene and pyrene in roots and shoots of maize (Zea mays L.)

Polycyclic aromatic hydrocarbons as byproducts of carbon-based fuel combustion are an important group of pollutants with wide distribution in the environment. Polycyclic aromatic hydrocarbons are known as toxic compounds for almost all organisms. Different plant species can uptake polycyclic aromatic hydrocarbons by roots and translocate them to various aerial parts. The aim of this study is to investigate the uptake, translocation, and accumulation of pyrene and phenanthrene in maize under controlled conditions. Seeds were cultivated in perlite containing 25, 50, 75, and 100 ppm of phenanthrene and pyrene, and their concentrations in the roots and shoots of the plants were measured using high-performance liquid chromatography technique after 7, 14, and 21 days. The results revealed that phenanthrene naturally existed in maize and its concentration showed a time-dependent decrease in shoots and roots. In contrast, the concentration of pyrene was increased in the roots and reduced in the shoots. Although pyrene had higher uptake than phenanthrene in roots of maize, the translocation factor value for pyrene was lower than for phenanthrene. According to these findings, phenanthrene could be metabolized in maize in the shoot and root tissues, but pyrene had more tendency to be accumulated in roots.

     

Biodegradation of low-density polyethylene (LDPE) using the mixed culture of Aspergillus carbonarius and A. fumigates

Low-density polyethylene (LDPE) possesses various applications in several industries owing to its durability, low-cost, and many mechano-thermal properties. Unfortunately, LDPE waste creates an environmental threat. The level of biodegradation of black LDPE sheets with fungi isolated from different landfills sites in Sharqiyah Governorate, Egypt, was evaluated. LDPE sheets, the only source of carbon, along with minimal salt medium were incubated on a rotary shaker at 30 °C and 120 rpm for 16 weeks. Aspergillus carbonarius MH 856457.1 and A. fumigatus MF 276893 confirmed to be good candidates for LDPE biodegradation. A mixed culture of two strains showed the excellent weight loss% of sheets as compared to single isolate. Further efforts to improve the degrading capacity through physical and chemical treatments were performed. The biodegradation was significantly stimulated by 39.1% (thermal treatment), 17.76% (HNO₃ treatment), and 5.79% (Gamma-irradiation treatment). Laccases and manganese peroxidases activities were assayed. LDPE biodegradation was analyzed by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and gas chromatography–mass spectrometry (GC–MS). FTIR spectra showed the appearance of new functional groups assigned to hydrocarbon biodegradation and confirmed the role of manganese peroxidase in process. The changes in the FTIR spectra of the mixed culture biomass before and after the biodegradation (Δ73 cm^?1) and the surface changes in the biodegraded LDPE (as indicated from SEM) confirmed the depolymerization of LDPE. From GC–MS analysis, the plasticizers bis(2-ethylhexyl) phthalate, Diisssctyl phthalate, 1,2-benzenedicarboxylic acid diisooctyl ester, and tributyl acetylcitrate completely biodegraded. Moreover, several antioxidants, antimicrobial, and anticancer compounds, and methyl esters of fatty acids were produced.

     

Flooding and the interannual variability of hydrologic quantities in the Missouri River basin

The six mainstem reservoirs in the Missouri River basin (MRB) are managed mainly to prevent flooding from snowmelt and heavy rainfall, a goal for which the interannual variabilities of precipitation ($P$), evapotranspiration ($\mathit{ET}$), and surface air temperature ($T_{\mathrm{air}}$) are vitally important. We tested the hypothesis that under the expected higher variability owing to global climate change, the months with the highest contributions to the interannual variability of $P$, $\mathit{ET}$, and $T_{\mathrm{air}}$ in the MRB will remain unchanged and quantified likely temporal trends in these quantities. Using high-resolution, downscaled Coupled Model Intercomparison Project Phase 5 multi-model ensemble data sets, we compared the multi-year ratio of monthly and annual interannual variability and temporal trends in $P$, $\mathit{ET}$, and $T_{\mathrm{air}}$ during 2011–2020 with three future decades. Results showed that the 6 months with the highest interannual variability in $P$ and $\mathit{ET}$ (April–September) are the same in all four decades. However, for $T_{\mathrm{air}}$, only 4 months (December–March) retain their status as highly variable throughout the four decades; September and October variability is exceeded by the variability in other months. This implies that, compared to $P$ and $\mathit{ET}$, the cyclical change in the probabilities of $T_{\mathrm{air}}$ in the MRB is less stable under future global climate change. This finding can be used to consider the need to alter existing strategies for reservoir release while minimizing the likelihood of aggravating flooding below the reservoirs.     

Leachate generation and biogas energy recovery in the Jebel Chakir municipal solid waste landfill,Tunisia

A survey was conducted between 2006 and 2008 in order to identify municipal solid waste (MSW) composition and its influence on leachate generation and to assess the amount of biogas yield from the Jebel Chakir landfill in Tunis City. The organic fraction was the predominant compound in the MSW, followed by paper, fine, plastic, leather, rubber, metal, textile, glass and ceramic. The average MSW moisture content varies from 60 % in the wet season to 80 % in the dry one. The recognised MSW composition is well representative if compared to that of cities in developing countries. A large leachate quantity is produced in the landfill of Jebel Chakir, despite the negative water balance of the site. Based on the annual MSW landfilled quantities and using the LandGEM model, the expected peak landfill gas (LFG) production is estimated to occur 1 year after the landfill closure with a rate of 3.53 × 10⁷ m³/year. The analysis of the potential conversion of LFG to electric energy shows it at a total LFG-to-electricity energy of around 257 GWh with a heating value of 4,475 kcal/m³ based on an LFG collection efficiency of 33 % and energy efficiency of 33 % giving an economic feasibility for a 10 MW power plant.     

A detailed kinetic investigation on the effects of hydrogen enrichment on the performance of gas-fueled SI engine

This study investigates the effects of hydrogen enrichment on formation of pollutants and greenhouse gases in gas-fueled spark ignition engines. To this end, a previously validated detailed mechanism is embedded with a comprehensive one-dimensional engine model and the results are verified with experimental observations at different compression ratios and engine loads. The simulations are then performed for different mixtures of hydrogen and natural gas. The results indicate that adding hydrogen increases the cylinder peak pressure at different loads and compression ratios, despite the fact that reduces the amount of carbon monoxide, carbon dioxide, and methane in all the conditions.     

Geochemical characterisation of pyrite oxidation and environmental problems related to release and transport of metals from a coal washing low-grade waste dump, Shahrood, northeast Iran

Pyrite oxidation and release of the oxidation products from a low-grade coal waste dump to stream, groundwater and soil was investigated by geochemical and hydrogeochemical techniques at Alborz Sharghi coal washing plant, Shahrood, northeast Iran. Hydrogeochemical analysis of water samples indicates that the metal concentrations in the stream waters were low. Moreover, the pH of the water showed no considerable change. The analysis of the stream water samples shows that except the physical changes, pyrite oxidation process within the coal washing waste dump has not affected the quality of the stream water. Water type was determined to be calcium sulphate. The results of the analysis of groundwater samples indicate that the pH varies from 7.41 to 7.51. The concentrations of the toxic metals were low. The concentration of SO4 is slightly above than its standard concentration in potable water. It seems that the groundwater less affected by the coal washing operation in the study area. Geochemical analysis of the sediment samples shows that Fe concentration decreases gradually downstream the waste dump with pH rising. SO(4) decreases rapidly downstream direction. Copper, Zn and Co concentrations decrease with distance from the waste dump due to a dilution effect by the mixing of uncontaminated sediments. These elements, in particular, Zn are considerably elevated in sediment sample collected at the nearest distance to the waste dump. There is no doubt that such investigations can help to develop an appropriate water remediation plan.