A new approach for chemical oxygen demand (COD) measurement at high salinity and low organic matter samples

Background, aim, and scope  

Chemical oxygen demand (COD) is used as a discharge standard parameter in wastewater treatment plant design, environmental modelling and many other applications. Chloride interference is an important problem of COD measurement for wastewaters containing low organic matter and high chloride concentrations. In case of chloride concentrations up to 2,000 mg/L, mercury sulphate addition at a ratio of 10:1 (HgSO₄:Cl⁻) can adequately mask the interference. When chloride concentration exceeds 2,000 mg/L, this ratio becomes ineffective to hinder the interference. At this point, it is proposed to use a greater and constant ratio of mercury sulphate addition. However, this application sometimes results in extra mercury sulphate addition which is not necessary. Even in some cases, greater addition of mercury sulphate alone is not a solution to erroneous measurement results. The purpose of the study is to determine optimum HgSO₄:Cl⁻ ratios according to the chloride concentrations of the samples and to show the importance of the strength of the digestion solution for the correct determination of the COD parameter.     

Assessment of imidacloprid toxicity on reproductive organ system of adult male rats

In the current study it was aimed to investigate the toxicity of low doses of imidacloprid (IMI) on the reproductive organ systems of adult male rats. The treatment groups received 0.5 (IMI-0.5), 2 (IMI-2) or 8 mg IMI/kg body weight by oral gavage (IMI-8) for three months. The deterioration in sperm motility in IMI-8 group and epidydimal sperm concentration in IMI-2 and IMI-8 groups and abnormality in sperm morphology in IMI-8 were significant. The levels of testosterone (T) and GSH decreased significantly in group IMI-8 compared to the control group. Upon treatment with IMI, apoptotic index increased significantly only in germ cells of the seminiferous tubules of IMI-8 group when compared to control. Fragmentation was striking in the seminal DNA from the IMI-8 group, but it was much less obvious in the IMI-2 one. IMI exposure resulted in elevation of all fatty acids analyzed, but the increases were significant only in stearic, oleic, linoleic and arachidonic acids. The ratios of 20:4/20:3 and 20:4/18:2 were decreased and 16:1n-9/16:0 ratio was increased. In conclusion, the present animal experiments revealed that the treatment with IMI at NOAEL dose-levels caused deterioration in sperm parameters, decreased T level, increased apoptosis of germ cells, seminal DNA fragmentation, the depletion of antioxidants and change in disturbance of fatty acid composition. All these changes indicate the suppression of testicular function.     

Sensitivity of the solution of the Elder problem to density, velocity and numerical perturbations

In this paper the Elder problem is studied with the purpose of evaluating the inherent instabilities associated with the numerical solution of this problem. Our focus is first on the question of the existence of a unique numerical solution for this problem, and second on the grid density and fluid density requirements necessary for a unique numerical solution. In particular we have investigated the instability issues associated with the numerical solution of the Elder problem from the following perspectives: (i) physical instability issues associated with density differences; (ii) sensitivity of the numerical solution to idealization irregularities; and, (iii) the importance of a precise velocity field calculation and the association of this process with the grid density levels that is necessary to solve the Elder problem accurately. In the study discussed here we have used a finite element Galerkin model we have developed for solving density-dependent flow and transport problems, which will be identified as TechFlow. In our study, the numerical results of Frolkovic and de Schepper [Frolkovic, P. and H. de Schepper, 2001. Numerical modeling of convection dominated transport coupled with density-driven flow in porous media, Adv. Water Resour., 24, 63-72.] were replicated using the grid density employed in their work. We were also successful in duplicating the same result with a less dense grid but with more computational effort based on a global velocity estimation process we have adopted. Our results indicate that the global velocity estimation approach recommended by Yeh [Yeh, G.-T., 1981. On the computation of Darcian velocity and mass balance in finite element modelling of groundwater flow, Water Resour. Res., 17(5), 1529-1534.] allows the use of less dense grids while obtaining the same accuracy that can be achieved with denser grids. We have also observed that the regularity of the elements in the discretization of the solution domain does make a difference in obtaining a unique stationary solution for this problem. The results of our study also indicate that the density differences are critical in the solution of the Elder problem and that high density differences lead to the physical instability that is inherent with this problem. Other than the physical instability associated with the level of density differences used in the Elder problem, the following two points should be considered in solving the Elder problem in a consistent manner: (i) strict attention should be paid to the vertical grid Peclet number in developing the criteria for convergent grid selection; and, (ii) with a globally continuous velocity calculation stable solutions can be obtained at lower grid densities.     

Stochastic modeling approaches based on neural network and linear–nonlinear regression techniques for the determination of single droplet collection efficiency of countercurrent spray towers

This paper presents a new mathematical model and a two-layer neural network approach to predict the single droplet collection efficiency (SDCE), η _d, of countercurrent spray towers. SDCE values were calculated using MATLAB^® algorithm for 205 different artificial scenarios given in a large range of operating conditions. Theoretical results were compared with outputs obtained from a two-layer neural network and DataFit^® scientific software. The predicted model developed from linear–nonlinear regression analysis and network outputs agreed with the theoretical data, and all predictions proved to be satisfactory with a correlation coefficient of about 0.921 and 0.99, respectively. By using the proposed model, iterations between Reynolds number (Re), drag coefficient (C _D) and terminal velocity values (v _T) were neglected for a large range of operating conditions. SDCE values were also obtained speedily and practically for five main operating inputs used in the model.     

An in silico approach to target RNA-dependent RNA polymerase of COVID-19 with naturally occurring phytochemicals

Environment, Development and Sustainability - The novel coronavirus disease 2019 (COVID-19) was firstly reported from Wuhan city of China and found as a highly contagious, transmittable and...     

Detoxification and reproductive system-related gene expression following exposure to Cu(OH)2 nanopesticide in water flea (Daphnia magna Straus 1820)

Environmental Science and Pollution Research - The extensive use of copper-based nanopesticides in agriculture has led to their release into the aquatic environment and causes a potential risk to...     

Elemental composition of Marrubium astracanicum Jacq. growing in tungsten-contaminated sites

Environmental Science and Pollution Research - This study evaluates the elemental (W, Mo, Zn, Fe, Cu, Cd, Mn, Pb, Cr, Co, B, and Bi) composition of Marrubium astracanicum Jacq. (Lamiaceae), around...     

Endosulfan is toxic to the reproductive health of male freshwater fish, <Emphasis Type="Italic">Cyprinion watsoni</Emphasis>

Endosulfan is an organochlorine pesticide that is toxic to aquatic life. Endosulfan might hamper the reproductive health of indigenous fish in agricultural areas of Pakistan where this pesticide is sprayed widely. The aim of the current study is to investigate the toxic effects of endosulfan on selected reproductive parameters of male freshwater fish, Cyprinion watsoni. Two concentrations of endosulfan (0.5 and 1 ppb for 30 days exposure) were tested for their effects on body weight, body length, and testicular weight, length, and width. Testicular testosterone was assayed from tissue extracts using enzyme immunoassay (EIA). A significant increase in the mortality rate was observed in both treated groups during both spawning and quiescent seasons. The overall behavior of fish in the aquarium was normal in all control and treated groups. However, the treated fish exhibited anxiety after treatment with endosulfan. The body weight and length, and testicular weight, length and width were not significantly different to the control group. The testicular testosterone concentrations were significantly lower in both endosulfan-treated groups compared to the control. The decrease was dose-dependent, with a significant difference between the two treated groups. The histomorphological results demonstrated various testicular alterations in the treated groups. These alterations included an increase in interlobular areas and clumping patterns in spermatocytes/spermatids. Because spermatids eventually differentiate into sperms, their low count will directly result in lower sperm count. Taken together, these results suggest that endosulfan is a toxicant that at least disturbs testosterone levels (possibly others) and negatively impacts the reproductive health of male freshwater fish.     

The effect of sodium hypochlorite solutions on in vitro seedling growth and shoot regeneration of flax (Linum usitatissimum)

The aim of this study was to determine the effect of concentration (40, 60, and 80%) and temperature (0, 10, 20, and 30°C) of sodium hypochlorite (NaOCl) solutions on seed germination, in vitro viability and growth of flax seedlings and regeneration capacity of hypocotyl explants. Results showed that seed germination, seedling growth and shoot regeneration were negatively affected by increasing concentration and temperature of disinfectant. The best results in seedling growth and shoot regeneration were obtained when 40% disinfectant concentration at 10°C was used.