In this work, we theoretically design a new π-conjugated thieno[3,4-b]pyrazine derivative intended for organic electronics. The geometric, electronic, optical, photovoltaic, and nonlinear optical (NLO) properties of the studied molecule were investigated using calculations based on density functional theory (DFT) and its time-dependent variant (TD-DFT) at the B3LYP/6-31G(d,p) level. The structural modification of the reference molecule results in a small energy gap (Eg = 1.68 eV) and a significant enhancement in optical absorption in the visible region, with maxima observed at λmax = 877 nm (TD-B3LYP) and λmax = 668 nm (CAM-B3LYP).

Herein, we theoretically design four new π-conjugated thieno[3,4-b]pyrazine derivatives for organic solar cells (OSCs), denoted 2,3-di([2,2′:5′,2″:5″,2‴-quaterthiophen]-5-yl)-5,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine, 2,3-bis(5'''-(4-fluorophenyl)-[2,2':5',2'':5'',2'''-quaterthiophen]-5-yl)-5,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine, 2,3-bis(5'''-(4-methoxyphenyl)-[2,2':5',2'':5'',2'''-quaterthiophen]-5-yl)-5,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine, and 2,3-bis(5'''-(9-methyl-9H-carbazol-2-yl)-[2,2':5',2'':5'',2'''-quaterthiophen]-5-yl)-5,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine. The geometric, electronic, optical, photovoltaic, and nonlinear optical (NLO) properties of the investigated chemical structure were investigated using Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations at the B3LYP/6-31G(d,p) level. Structural changes on the chemical structure induce a narrow energy gap in the range (2.08 – 2.12 eV), and an enhancement of the absorption in the visible range (λmax = 682 – 688 nm). In addition, a low value of exciton binding energies is obtained (Eb = 0.28 – 0.31 eV). Analysis of the density of states (DOS), transition density matrix (TDM), electron localization function (ELF), and localized orbital locator (LOL) showed effective charge delocalization and donor-to-acceptor electron transfer. The photovoltaic performance was assessed using the open circuit voltage (Voc) obtained between Highest Occupied Molecular Orbital (HOMO) donor to Lowest Unoccupied Molecular Orbital (LUMO) acceptor levels and was found promising (Voc = 1.32 – 1.44 V). The large hyperpolarizability and high nonlinearity response of the NLO results also indicated the potential for these molecules to be used in various optoelectronic applications.

This study used 30 cm long packed by 3 kg soil columns to explore the effects of peat, compost, and charcoal at 5% on the movement of fipronil (99.9 % purity) in clay loam soil and sandy clay loam soil. The soil columns were preconditioned with calcium chloride solution (0.01 M) before applying the pesticide and potassium iodide. Potassium iodide solution (0.2 M) was added at a rate of 10 mL as a water tracer and a quantity of fipronil solution (10 µg g^-1soil) was applied on the soil surface of each column. Next, fipronil was leached from the soil columns with a calcium chloride solution (0.1 M) and the leachates were collected and analyzed. The results show that water tracer I^- leached fast in soil columns. The breakthrough curve of fipronil appeared from leachates of soil columns after iodide for a while, indicating that fipronil is a moderate or lower mobile compound depending on type of soil and type of soil amendments. In general, adding soil amendments (peat, compost, and charcoal) to clay loam soil and sandy clay loam soil resulted in improved fipronil adsorption and decreased the amount of fipronil that leached into groundwater. This study is very useful for preserving groundwater from pollution, especially in the Middle East due to the lack of water sources.

The dissipation and side-effect of metribuzin (MBZ) were studied with various factors; two soil types (clay loam and sandy loam), soil amendment (wheat straw and without amendment), two temperature levels (25 and 50°C), sterilization (sterilized and unsterilized soil) and time of incubation (15 and 30 days) and designed by Windows version of MINITAB software package to reduce the time and the cost as well as increased the precision. Determination of MBZ by HPLC with recoveries ranged from 50.85 to 108.09%. The MBZ residues were detected in all samples up to 60 days of storage, respectively with decline in their concentrations with the time of incubation. The clay loam soil showed higher dissipation than the sandy loam soil. The different factors in the present study confirmed that the wheat straw amendment, non-sterilization and incubation at 50°C caused higher dissipation of MBZ than without wheat straw, sterilization and incubation at 25°C. The dissipation was described mathematically by a first order equation with t0.5 was ranged from 9.62 to 16.82 days in clay loam soil and from 10.01 to 16.04 days in sandy loam soil. The side-effect of MBZ was tested on soil dehydrogenase activity that can be considered as an indicator of the biological activity and microbial degradation. The result proved that the enzyme activity was significantly decreased in all treatments compared with the controls at 1 and 3 days of incubation then it was gradually increased at 7, 10, 15 and 30 days of incubation. Treatments of wheat straw, non-sterilized and incubated at 25°C or 50°C showed the lowest enzyme inhibition among all treatments.

The food industry consumes large amounts of water although there is an increasing demand for water and a rapid decrease in the level of natural water resources. Wastewater resulting from food industries needs to be assessed for their compliance to standards. In this study, wastewater treatment steps from the food industry were investigated for accurate assessment of wastewater loading by analyzing parameters of the concentration of compounds present in the effluents. The results revealed that the parameters of treated wastewater were as follow, electrical conductivity 2931 μs/cm, total suspended solids 100 mg/L, biochemical oxygen demand 90 mg/L, chemical oxygen demand 250 mg/L, total phosphorus 7.9 mg/L, and total nitrogen 70 mg/L. This exerts a huge load on the biological treatment unit. Thus, this study offers an understanding and support in selecting appropriate treatment for industrial wastewater to obtain an effluent suitable in compliance with standards of the environmental quality.

Herbicides used on a regular basis could endanger non-target species like earthworms. The aim of this work was to test the toxic effect of atrazine and metribuzin on Aporrectodea caliginosa by filter paper contact and soil mixing techniques. Atrazine had the highest intrinsic toxicity to earthworms, with LC50 of 0.026 µg mL-1 after 72 hr of treatment. While the LC50 of metribuzin was 0.063 µg mL-1 after 72 hr by filter paper contact test. LC50 was reduced from 11.121 to 3.118 and 164.824 to 19.113 μg g soil-1 in clay soil, from 32.221 to 17.33 and 324.141 to 41.028 μg g soil-1 in soil (1:1) and from 41.234 to 30.804 and 462.255 to 70.902 μg g soil-1 in sandy clay loam soil of atrazine and metribuzin after 5 and 10 day. Generally, atrazine is more toxic than metribuzin in both tests.

The soil type and temperature are considered important parameters that can influence the rates and equilibria of different environmental processes. Therefore, the adsorption and desorption isotherms of fipronil in clay loam, clay, sandy loam, sandy clay loam, sand and loamy sand soils at 25 and 50˚C was studied. The amount of fipronil adsorbed and desorbed by different soils was significantly influenced by the temperature. Adsorption was higher in clay loam, clay, sandy clay loam and sandy soil at 25°C, while sand soil and loamy sand soil at 50°C. The non-desorbed amount was greater at 25°C in different types of soil except for clay loam soil. The negative ΔG˚ indicated that the adsorption/desorption in different types of soil was spontaneous at different temperatures. The value of standard enthalpy change (ΔH˚) was positive in clay soil, sandy loam soil, sandy clay loam soil and loamy sand soil for adsorption and sandy loam soil, sand soil and loamy sand soil for desorption. Moreover, the standard entropy change (ΔS˚) was negative in soils for adsorption and desorption isotherms except clay loam soil. Adsorption and desorption isotherms trends as well as the values of the correlation coefficients indicated that the adsorption and desorption isotherms of fipronil in tested soils were fitted to the Freundlich model because the correlation coefficient is very close to 0.999.