F. Al-Misned

Tissue Metal Distribution and Risk Assessment for Important Fish Species from Saudi Arabia

Abstract The concentrations of nine heavy metals (Cr, Cd, Pb, Ni, Cu, Zn, Mn, As and Fe) in the muscle tissue of four fish species (Oreochromis niloticus, Clarias gariepinus, Poecilia latipinna and Aphanius dispardispar) collected from Wadi Hanifah were detected in two different seasons. The concentrations of the studied heavy metals, except for Cd, Pb, Ni and Cu in A. d. dispar and P. latipinna, were found to be below the safe limits recommended by various authorities and thus provide an indication of the extent of pollution of these metals. The present study also demonstrates that Zn and Cr were the most and least accumulated metals, respectively, in the studied fish muscle tissues. From the standpoint of human health, this study suggests that there is a possible health risk to consumers due to the current consumption rate of A. d. dispar and P. latipinna in Saudi Arabia.

Heavy metals contamination of a Mediterranean Coastal Ecosystem, Eastern Nile Delta, Egypt

The concentrations of Fe, Mn, Zn, Cu, Pb and Cd in bottom sediment and surface water in the Egyptian coastal waters along the Mediterranean Sea, and thence the soft tissues of the bivalve (Donax trunculus) were determined. The mean concentrations (µg g-1) of heavy metals in bottom sediment were as follows: Fe: 1748.2-2030, Mn: 191.4-254.3, Zn: 28-42.2, Cu: 4-9.4, Pb: 18.4-24.8, Cd: 1.4-2.3, and in surface water: Fe: 744-896, Mn: 162-198, Zn: 242.6-300, Cu: 12.6-19.3, Pb: 31.3-56, Cd: 0.8-3.1,while in soft tissues of the bivalve D. trunculus, the mean concentrations (µg g-1 dry weight) were as follows: Fe: 47.2-66.4, Mn: 4.8-8.4, Zn: 22-36.4, Cu: 3.2-4.8, Pb: 5.6-9.2, Cd: 1.6-2.4. The present study has revealed that the concentrations of Cd and Pb in the soft tissues of the edible bivalve D. trunculus were above the maximum acceptable concentrations for human consumption proposed by FAO/WHO, EU. Moreover, estimation of concentration factor (Cf) for the studied metals in the soft tissues of the edible bivalve D. trunculus recorded high accumulation rates of Cd and Cu. The present study confirmed that, the examined bivalve species was associated with enhanced metal content in its soft tissues and was not safe within the limits for human consumption. Water and bottom sediments showed apparent seasonal variations of metals accumulation with maximum concentrations during summer and winter, respectively. Mean metal concentrations were found to be higher in some of the selected five sites than others, but, these differences in heavy metal concentrations were not statistically significant (P>0.05), suggesting that common and main anthropogenic sources contributing to the heavy metal pollution at this Egyptian coastal area on the Mediterranean sea. The results obtained in this study were compared with those reported in earlier studies and concluded that, the area of the present study was in general not considered a metal polluted area according to the OME and EPA classification criteria. However, concentrations of Cd and especially, Pb did give some cause for concern, and warrants a continued monitoring programme for inorganic and chemical organic compounds in sediments, water, and biota along the Egyptian Mediterranean coasts.

Simultaneous removal of tetracycline hydrochloride and As(III) using poorly-crystalline manganese dioxide.

Simultaneous removal of antibiotic tetracycline hydrochloride (TC) and As(III) by poorly-crystalline Mn dioxide was investigated. TC and As(III) can be effectively oxidized and removed by MnO2. High concentrations of TC and As(III) competed with each other for oxidation or adsorption sites on MnO2 and thus affected their removal efficiency. The intermediates and products of TC after reaction with poorly-crystalline manganese dioxide were identified by LC-ESI-MS (liquid chromatography-electrospray ionization-mass spectrometry), and the decomposition pathways of TC by MnO2 were proposed. This study is helpful for understanding the importance of environmental Mn dioxides in the decontamination of combined pollution by organic pollutants and metal(loid)s.

Fish Cholinesterases as Biomarkers of Sublethal Effects of Organophosphorus and Carbamates in Tissues of Labeo Rohita

Organophosphates and carbamates are major agrochemicals that strongly affect different neuroenzymes and the growth of various fish species. Here, we study the effect of sublethal concentrations of profenofos and carbofuran on the activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) and the associated health risk in fish. Labeo rohita fingerlings were exposed to three sublethal concentrations of profenofos and carbofuran. The minimum cholinesterase activities in the brain, gills, muscle, kidney, liver, and blood were after exposure to profenofos (0.06 mg/L). The minimum AChE and BuChE activities in the brain, gills, muscle, kidney, liver, and blood were after exposure to carbofuran (0.28 and 0.198 mg/L). Exposure to both types of pesticides affected the functions of these organs, including metabolism and neurotransmission, to various extents at different exposure concentrations. These findings suggest that they are required to be properly monitored in the environment, to reduce their toxic effects on nontarget organisms

Aerobic and anaerobic biosynthesis of nano-selenium for remediation of mercury contaminated soil.

Selenium (Se) nanoparticles are often synthesized by anaerobes. However, anaerobic bacteria cannot be directly applied for bioremediation of contaminated top soil which is generally aerobic. In this study, a selenite-reducing bacterium, Citrobacter freundii Y9, demonstrated high selenite reducing power and produced elemental nano-selenium nanoparticles (nano-Se0) under both aerobic and anaerobic conditions. The biogenic nano-Se0 converted 45.8-57.1% and 39.1-48.6% of elemental mercury (Hg0) in the contaminated soil to insoluble mercuric selenide (HgSe) under anaerobic and aerobic conditions, respectively. Addition of sodium dodecyl sulfonate enhanced Hg0 remediation, probably owing to the release of intracellular nano-Se0 from the bacterial cells for Hg fixation. The reaction product after remediation was identified as non-reactive HgSe that was formed by amalgamation of nano-Se0 and Hg0. Biosynthesis of nano-Se0 both aerobically and anaerobically therefore provides a versatile and cost-effective remediation approach for Hg0-contaminated surface and subsurface soils, where the redox potential often changes dramatically.

Bioimmobilization of Heavy Metals in Acidic Copper Mine Tailings Soil

ABSTRACT Heavy metal contamination of mine tailings is one of the most serious environmental challenges facing the mining industry worldwide. Conventional technologies used for the treatment of such tailing soils are expensive both in terms of operation and capital costs as well as being not so effective. In the present study, an indigenous calcifying urease producing bacterial strain was isolated from copper mine tailing soil and used for bioimmobilization of copper, lead and cadmium in contaminated mine tailing soils. Phylogenetic analysis of the 16S rRNA gene sequence identified it as Bacillus firmus. The efficiency of metal bioimmobilization was based on microbially induced calcite precipitation (MICP). A five-stage sequential soil extraction procedure was carried out to obtain distribution patterns for the different metals. The mobility of the toxic metals was found to be significantly reduced in the exchangeable fraction with their concentrations markedly increasing in the carbonated fraction after bioremediation. Scanning electron microscopy showed the precipitation of calcite in association with the bacterial cells. Calcium carbonate minerals such as calcite, gwihabaite and aragonite were identified in the bioremediated tailings soils using X-ray diffraction (XRD). It is concluded that MICP holds considerable promise for the remediation of mine tailing soils by efficient immobilization of toxic metals such as copper, lead and cadmium.

Effects of dietary copper exposure on accumulation, growth, and hematological parameters in Cyprinus carpio

The influence of dietary copper (Cu) exposure on accumulation, growth, and hematological parameters was investigated in Cyprinus carpio after sub-chronic ingestion of 0, 250, 500, 750 or 1000 mg kg−1 for 60 days. The profile of Cu accumulation among tissues in C. carpio was dependent on the exposure period and Cu concentration. Liver of C. carpio was the predominant storage tissue and the order of Cu accumulation in tissues was liver > intestine > gill > kidney > muscle. Cu concentration at >125 mg kg−1 reduced growth rate, and was inversely related to growth. The RNA : DNA ratios were not affected by exposure and there was no correlation between growth rate and RNA : DNA ratio in liver and muscle. There were no significant effects of exposure on blood parameters except for magnesium. Cu exposure time and dose increased the serum glutamic-oxaloacetic transaminase (SGOT) and serum glutamic-pyruvic transaminase (SGPT) activity levels.

Effects of irradiation and pH on fluorescence properties and flocculation of extracellular polymeric substances from the cyanobacterium Chroococcus minutus.

Microbial extracellular polymeric substances (EPS) may flocculate or be decomposed when environmental factors change, which significantly influences nutrient cycling and transport of heavy metals. However, little information is available on the stability of EPS in natural environments. Fluorescence and flocculation properties of EPS from Chroococcus minutus under different irradiation and pH conditions were studied. Two aromatic protein-like fluorescence peaks and one tyrosine protein-like peak were identified from the excitation-emission-matrix (EEM) fluorescence spectra of EPS. UVB (ultraviolet B) and solar irradiation increased the fluorescence intensity of all the three peaks while UVC (ultraviolet C) irradiation had little effect. EPS formed unstable flocs after exposure to UV (ultraviolet) irradiation and formed stable flocs under solar irradiation. EPS were prone to flocculation under highly acidic conditions and minimal fluorescence of peaks was observed. The fluorophores in EPS were relatively stable under neutral and alkaline conditions. These findings are helpful for understanding the behavior of EPS in aquatic environments and their role in biogeochemical cycles of the elements.

Monitoring of trace metals in tissues of Wallago attu (lanchi) from the Indus River as an indicator of environmental pollution

We aimed to assess the bioaccumulation of selected four trace metals (Cd, Ni, Zn and Co) in four tissues (muscles, skin, gills and liver) of a freshwater fish Wallago attu (lanchi) from three different sites (upstream, middle stream and downstream) of the Indus River in Mianwali district of Pakistan. Heavy metal contents in water samples and from different selected tissues of fish were examined by using flame atomic absorption spectrometry. The data were statistically compared to study the effects of the site and fish organs and their interaction on the bioaccumulation pattern of these metals at P < 0.05. In W. attu the level of cadmium ranged from 0.004 to 0.24; nickel 0.003–0.708; cobalt 0.002–0.768 and zinc 47.4–1147.5 μg/g wet weight. The magnitude of metal bioaccumulation in different organs of fish species had the following order gills > liver > skin > muscle. The order of bioaccumulation of these metals was Ni < Zn < Co < Cd. Heavy metal concentrations were increased during the dry season as compared to the wet season. The results of this study indicate that freshwater fish produced and marketed in Mianwali have concentrations below the standards of FEPA/WHO for these toxic metals.

Bioremediation of Nitrate- and Arsenic-Contaminated Groundwater Using Nitrate-Dependent Fe(II) Oxidizing Clostridium sp. Strain pxl2

ABSTRACT Groundwater in many parts of the world is contaminated with arsenic and nitrate. To date no technology is available that can in situ remediate arsenic and nitrate pollution of groundwater using one single bacterial species. In this study, a novel anaerobic nitrate-dependent Fe(II)-oxidizing bacterium, Clostridium sp. strain PXL2, was isolated from anoxic activated sludge. The strain PXL2 could efficiently oxidize Fe(II) associated with the reduction of nitrate. Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared Spectrometry (FTIR) analysis showed that strain PXL2 formed nanosize and poorly crystalline Fe(III) oxides which encrusted the cells, with the viability and function of the cells might being inhibited by the encrustation of Fe(III) oxides. It was found that strain PXL2 was an excellent candidate microbe for bioremediation of nitrate and arsenic pollution. It could effectively and simultaneously remove As(III) and nitrate from water due to its Fe(II) oxidation and denitrtification activity. 40.6–100% of NO3− was removed from an initial concentration of 12.3 mM. High concentrations of As(III) decreased nitrate removal. With initial concentrations of 10 μM, 65 μM and 125 μM As(III), 100% of As(III) was removed in a 20 d treatment. Arsenic was removed by adsorption to the biogenic Fe(III) oxides but not by adsorption to the cells. Strain PXL2 was also able to oxidize As(III) to less mobile and less toxic As(V) and this may significantly enhance the performance of bioremediation of arsenic pollution. Anaerobic nitrate-dependent Fe(II)-oxidizing species, such as strain PXL2, has great application potential for in situ remediation of nitrate and metal(loid)s polluted groundwater with advantages of high efficiency and low cost.