Interactions between metals accumulated in the narrow-clawed crayfish Astacus leptodactylus (Eschscholtz, 1823) in Dikilitaş Lake,Turkey

The accumulations of Al, Cd, Cr, Cu, Fe, Ni, Pb and Zn in the exoskeleton, gills, hepatopancreas and abdominal muscles of crayfish Astacus leptodactylus (Eschscholtz, 1823) were determined. The strongest correlation observed was between Cr and Ni in the gills (r?=?0.904); moderate to strong correlations between Al, Cr, Fe, Ni and Cu were also observed in gill tissue. Disregarding the gills, the strongest correlation was found between Cu and Zn in the hepatopancreas (r?=?0.808); the correlation between these two metals might have been a result of metallothionein activity. The accumulation of Pb was found to correlate with that of Cd in the exoskeleton, Cd and Zn in the gills, Zn and Cu in the hepatopancreas and Cu in the abdominal muscle. None of these correlations were present in lakewater and sediment samples, suggesting that the crayfish metabolism may be responsible for the co-accumulation of metal–metal pairs. As all correlations in non-gill tissues are observed between divalent metals, a shared transporter such as divalent metal transporter 1 might be involved in the accumulation of these metals.     

The effects of alginate microspheres on phytoremediation and growth of Lemna minor in the presence of Cd

Today, the removal of increased amount of contaminant concentrations in nature such as metals, nanoparticles, has become an essential issue to struggle with. In this paper, both the toxic effects of non-essential Cd on Lemna minor in presence of alginate microspheres and metal removal capacity of Cd-exposed L. minor and microspheres were investigated. Three test groups were constructed: group (L) containing Lemna, group (M) containing alginate microsphere and group (L?+?M) containing alginate microsphere and Lemna. Five different levels of Cd concentrations were added into these groups. Estimation models were constructed to estimate Cd removal capacities of L. minor and microspheres, and time-concentration-dependent growth (GRC) rates of both microsphere-containing and non-containing groups were modelled by regression analysis. It was seen that microspheres alone only had no positive or negative effects on Lemna growth. It was observed that, for all test groups the time-dependent growth rate has both increase–decrease trends in general. The toxicity effect of Cd on Lemna growth was reduced by adding microspheres into medium. Furthermore, the results stated that test groups containing only microspheres (M, 0–97.56%) and consortium groups (M?+?L, 0–98.26%) were slightly more successful in Cd removal process compared to Lemna (L) groups (L, 0–97.32%).     

Bioremediation of heavy metal contaminated medium using Lemna minor,Daphnia magna and their consortium

Single, dual and triple mixtures of totally seven different mixture combinations of the metals Al, Ba and Fe were examined in Lemna minor (L) culture, Daphnia magna (D) culture and in a consortium culture consisting of L. minor and D. magna. In this study: (a) differences in removed metal proportions at the end of 24 and 48?h, (b) differences in removed metal amounts due to cultures, (c) differences in the removed proportions of a metal in distinct mediums and (d) removal correlation of the metals due to cultures were investigated. The study results showed that among the metals Al, Ba and Fe, Al has the most toxic effect on organisms involved in this study. Although similar toxicity results of Al and Fe on test groups were observed, Ba gave different toxicity results on test groups. An overview of the bioremediation results indicates that L. minor removes the metals Al and Fe more successfully than Ba. Different mixture combinations of metals performed dissimilar removal results in the same cultures. According to the correlations analysis for the metals Ba and Fe, a high correlation was recorded between the consortium group and test groups containing only D. magna, r?=?0.88, r?=?0.91, respectively.     

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.     

Recovery of volatile fatty acids via membrane contactor using flat membranes: Experimental and theoretical analysis

Volatile fatty acid (VFA) separation from synthetic VFA solutions and leachate was investigated via the use of a membrane contactor. NaOH was used as a stripping solution to provide constant concentration gradient of VFAs in both sides of a membrane. Mass flux (12.23 g/m² h) and selectivity (1.599) observed for acetic acid were significantly higher than those reported in the literature and were observed at feed pH of 3.0, flow rate of 31.5 ± 0.9 mL/min, and stripping solution concentration of 1.0 N. This study revealed that the flow rate, stripping solution strength, and feed pH affect the mass transfer of VFAs through the PTFE membrane. Acetic and propionic acid separation performances observed in the present study provided a cost effective and environmental alternative due to elimination of the use of extractants.     

Yield and leaf area index estimations for sunflower plants using unmanned aerial vehicle images

Vegetation is commonly monitored to improve efficiency of various agricultural practices. Spatial and temporal changes in plant growth and development can be monitored with the aid of remote sensing techniques employing ground, aerial, and satellite platforms. Unmanned aerial vehicles (UAV) and multi-spectral cameras developed for UAVs have an important potential for agricultural management activities with high-resolution spatial and temporal images. However, UAV images should be assessed based on ground measurements for using these images as a decision-support tool in agriculture. This study was conducted to estimate sunflower leaf area index (LAI) and yield with the aid of Normalized Difference Vegetation Index (NDVI) images generated from raw UAV images. Furthermore, UAV-based NDVI values were compared with NDVI values calculated by using hyper-spectral measurements carried out with a ground-based spectroradiometer. Between July and August of 2017, six flight missions were conducted and spectral measurements were made simultaneously. A significant correlation (R²?=?0.77) was determined between NDVI values that belong to UAV platform and spectroradiometer. Also, regression models developed for sunflower LAI and yield estimation depending UAV-based NDVI have R² values of 0.88 and 0.91, respectively.     

Accumulation trends of metals and a metalloid in the freshwater crayfish Astacus leptodactylus from Lake Yeniçağa (Turkey)

This study aims to determine the extent of metal pollution in Lake Yeniça?a (Bolu, Turkey) by investigating the accumulation trends of five metals (Al, Cu, Fe, Ni and Zn) and a metalloid (As) in gills, exoskeleton, hepatopancreas and abdominal muscles of the freshwater crayfish Astacus leptodactylus. Principal component analysis (PCA), cluster analysis (CA), correlation analysis and analysis of variance (ANOVA) were utilised to determine the accumulation profiles of each element over four seasons. The greatest element accumulation was found to occur in the gills. All elements in exoskeletal tissue displayed positive correlations with each other, a similar trend was also observed in the hepatopancreas samples. Strong (r=0.868) and very strong (r=0.960) positive correlations were found between the accumulations of Al and Fe in gills and the exoskeleton, respectively. Correlations in tissue accumulation rates are discussed in the context of metabolic roles and impacts associated with the elements tested. Elemental compositions of Yeniça?a water and sediment samples were also investigated to determine whether the composition of the surrounding environment matches the metal accumulation trends of tissue samples. We demonstrate that, by the criteria set by the United States Environmental Protection Agency, Lake Yeniça?a is heavily polluted in terms of As and Ni.