Cytotoxic effect of sodium arsenite on Nile tilapia (Oreochromis niloticus) in vivo

This study showed the relevance of using chromosomal aberration (CA) as potential indicators of sodium arsenite (SA; NaAsO₂) cytotoxicity. The study investigated cytotoxic potential of SA in Oreochromis niloticus using CA assessment. The fish were exposed to four different concentrations of SA (5, 10, 20 and 40 mg/L) for 24 hours in comparison to a control group. The As concentrations in the samples were analysed by inductively coupled plasma atomic emission spectrometry. The differences in As concentrations in the water and O. niloticus samples between the control and experimental groups were significant (p<0.05), whereas the within experimental group differences were not significant. The cytotoxic assessment of SA in O. niloticus revealed five types of CAs, including single chromatid gaps (SCG), single chromatid break (SCB), centric gap (CG), fragmentation (F) and deletion (D). The most common CA in the O. niloticus samples was SCG. A total of 2.33, 10.67, 18.67, 18.00 and 23.67% of the cells in the control and experimental groups exhibited CAs. The numbers of CAs and cells with CAs from the control and experimental groups of fish were significantly different (p<0.05); additionally, the fish exposed to 5 and 40 mg/L showed significant within experimental group differences (p<0.05).     

Cytotoxic assessment of flying barb fish (Esomus metallicus) from a gold mine area with heavy metal contamination

This study aimed to investigate contamination by heavy metals including arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), and manganese (Mn) and to conduct a cytotoxic assessment of Esomus metallicus from a gold mine area compared with that from the non-affected area. The E. metallicus samples were collected downstream of a gold mine area. The heavy metal concentrations were analysed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The average amounts of As, Cd, Cr, Pb and Mn in water and E. metallicus samples from the gold mine area were 0.368 ± 0.009, 0.008 ± 0.006, 0.009 ± 0.001, 0.006 ± 0.002, 1.438 ± 0.058 mg/L, 0.65 ± 0.25, 0.03 ± 0.03, 2.12 ± 0.05, 0.25 ± 0.07 and 18.28 ± 6.82 mg/kg, respectively. The difference of As, Cr and Mn concentrations in E. metallicus samples between gold mine and non-affected areas was statistically significant (p < 0.05) except for Cd and Pb. The diploid chromosome number of E. metallicus from both areas was 2n = 50. There are six types of chromosomal aberrations including centric fragmentation (CF), centric gap (CG), single chromatid gap (SCG), fragmentation (F), deletion (D) and polyploidy (P). The most common chromosomal aberration type in the samples from the gold mine area was CG, and the difference in chromosomal aberration and the number of cells with chromosomal aberrations in E. metallicus between the study areas was statistically significant (p < 0.05). The percentages of chromosomal aberrations in the E. metallicus samples from gold mine and non-affected areas were 14.66 and 3.00, respectively.     

Concentrations and risks of polycyclic aromatic hydrocarbons in smoke-cured fish products in Nigeria

The concentrations of polycyclic aromatic hydrocarbons (PAHs) were determined in nine popular smoked fish species, (Clarias gariepinus, Parachana obscura, Heterotis niloticus, Pseudotolithus senegalensis, Gymnarchus niloticus, Ethmalosa fimbriata, Sardinella aurita, Scromber scrombus and Trachurus trachurus), in the Nigerian market by using gas chromatography-mass spectrometry after extraction by ultrasonication with hexane/dichloromethane. The mean concentrations of ∑16 PAHs in these species ranged from 52.4 μg kg^?1 to 1230 μg kg^?1. The estimated margins of exposure (MOE values) were less than 10,000 for C. gariepinus, G. niloticus and E. fimbriata indicating serious concern for the consumers’ health. The estimated excess cancer risk factors for these fish species investigated indicate that approximately 1 to 65 out of 10⁶ equally exposed adults may suffer from cancer and cancer-related diseases during their lifetime through the ingestion of carcinogenic PAHs from smoked fish in their diet.     

Separation of a compound effective against Biomphalaria alexandrina snails from the filtrate of Penicillium janthinellum

Biomphalaria alexandrina snails, as intermediate hosts of schistosomiasis, play a central role in dissemination of the disease. Control of these snails by chemical molluscicides adversely affects the aquatic environment, causing toxic and carcinogenic effects on non-target organisms. Searching for promising substances from biological origin becomes an urgent need to overcome these drawbacks. Screening tests were carried out on 236 fungal genera isolated from the habitat of freshwater snails in four Egyptian governorates. Twenty species were effective against B. alexandrina snails, but the most potent was Penicillium janthinellum as the value of LC₅₀ was 1.03%. Chemical analyses of this filtrate resulted in the separation of a compound effective against snails; it was identified as methyl gallate. Protein electrophoresis showed that both fungal filtrate and methyl gallate affect the protein pattern of snails’ haemolymph. Little or no mortality of Daphnia pulex individuals was observed after their exposure to sub lethal concentrations of each treatment.     

Arsenic uptake potential of water lettuce (Pistia Stratiotes L.)

Arsenate uptake by aquatic plant water lettuce (Pistia stratiotes L.) was studied in the laboratory condition to investigate a low cost natural aquatic treatment system for pollutant removal. The plants were harvested from a local pollution‐free pond in young condition and hydroponically cultured in the laboratory. Bio‐accumulation was noticed to be both concentration and duration dependent. The results show that the plant could effectively absorb arsenic between a range of 0.25 to 5.0 mg/l to the extent of 82.0 to 22.8% for a biomass of 20 g/l at pH 7.0 after 144 h. The results were also plotted in Langmuir and Freundlich isotherms and the data were well fitted. The sorption capacity was evaluated as 1.43 mg/g for the Langmuir isotherm and 1.01 mg/g for the Freundlich isotherm. The removal efficiency was, however, noted to be maximum (87.5%) at pH 6.5. The effect of biomass quantity has also been investigated along with some metabolic parameters.     

Vertical variation in magnitude and partitioning of oxygen demand in a contaminated sediment

Antimicrobial resistance is a phenomenon of increasing importance. Sewage treatment processes are a vehicle for dissemination of resistant bacteria in both aquatic and terrestrial environments. To assess the number of antimicrobial resistant E. coli present in the wastewater inflow, effluent and sludge from urban sewage treatment plants in Portugal, 42 samples of crude inflow, treated effluent and sludge were collected in 14 municipal sewage treatment plants in Portugal. A total of 940 E. coli strains were recovered and tested, using the diffusion agar method, regarding their sensitivity to 12 different antimicrobial drugs. Resistance to tetracycline, ampicillin, trimethoprime/sulfamethoxazole, streptomycin and ciprofloxacin was found in 42.2, 32.6, 23.3, 26.4 and 11.9% of the isolates, respectively. No correlation was found with regards to medical antimicrobial use in Portugal. The highest resistance rates were found in E. coli strains isolated from the district capitals sampled. Wastewater treatment resulted in E. coli decrease between less than one log to four logs; nevertheless, an average of 1.17 × 10⁶ CFU/100 ml were present in the outflow of the plants. This investigation highlights the necessity for constant monitoring of the final effluent and sludge from these treatment facilities.     

Bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans in the foodweb of Ya-Er Lake area, China

Bioaccumulation of PCDD/F in the foodweb was investigated in the Ya-Er Lake area, which was heavily polluted by PCDD/F. The high concentrations of PCDD/F in sediment can be transferred and bioaccumulated by aquatic organisms and humans through various pathways. Benthonic invertebrate animals and aquatic plants with a lot of fibers in the root can accumulate PCDD/F from sediment and water. Snail (Bellamya aeruginosa), shrimp (Macrobranchium sp.) and freshwater mussel (Acuticosta chinensis (Lea)) took up PCDD/F from the water and maintained the emission patterns, whereas fish tended to selectively accumulate 2,3,7,8-substituted isomers. The tissues of fish-eating bird and duck (Anas platyrhynchos) were very highly contaminated by PCDD/F due to ingestion of fish and other aquatic organisms from sediment. The residual concentration in breast milk depended on the original concentration of PCDD/F in the food. A resident in Ya-Er Lake area showed a daily intake of PCDD/F of about 9.14 pg TEQ/kg body weight/day. This is higher than the tolerable daily intake (TDI) for PCDD/F (1 pg TEQ/kg body weight/day), which was recommended by the World Health Organization (WHO).     

Study on swelling properties of an expansive soil deposit in Saskatchewan, Canada

The main objective of this paper was to study the swelling properties of Regina clay. The deposit comprises a topsoil (surface to 0.3 m depth), an expansive clay (0.3–8 m), and a bottom till (8–9 m). High liquid limit (70 ± 15 %) and plastic limit (33 ± 4 %) indicated high water retention and adsorption capacity for the clay. Irrespective of the cover type (vegetation and cracked road), the field water content in summer closely matched the plastic limit. The clay was characterized by medium-to-high swelling that was best predicted by SP = 0.16 (I _p)^1.188. The soil had 51 % clay minerals including smectite (32 %), illite (7 %), kaolinite (5 %), and chlorite (3 %). With a CEC of 40 cmol(+)/kg, Ca²⁺ and Mg²⁺ were found to be the main exchangeable cations: the specific surface area was 50 m²/g. The SP and P _s for a 1.2 m deep sample measured 12 % and 260 kPa, respectively, and the estimated surface heave of 180 mm gradually diminished to 3.6 m depth. These values matched well with consistency-based correlations.     

Mercury contamination in the vicinity of a derelict chlor-alkali plant Part II: contamination of the aquatic and terrestrial food chain and potential risks to the local population

This study investigated the environmental impact and level of risk associated with mercury (Hg) contamination near a derelict chlor-alkali plant in Pavlodar, Northern Kazakhstan. Several species of fish were sampled from the highly polluted Lake Balkyldak and the nearby river Irtysh, to assess the extent of Hg bioaccumulation in the aquatic food chain and potential human health risks. A small number of bovine tissue samples, water samples, soil and plant samples from a nearby village were also investigated in order to make a preliminary assessment of potential impacts on the terrestrial food chain. Mercury levels in fish caught from Lake Balkyldak ranged from 0.16 to 2.2 mg kg(-1) and the majority of fish exceeded current human health criteria for Hg. Interspecies comparisons indicated that Hg is accumulated in the order dace>carp>tench. Site-specific bioaccumulation factors (BAF) were calculated for THg, and were estimated for MeHg. Fish from the river Irtysh and floodplain oxbow lakes contained between 0.075 and 0.159 mg kg(-1) of Hg and can be regarded as uncontaminated. Soils were found to be impacted by past atmospheric emissions of Hg. Cattle grazing in the surroundings of the factory are exposed to Hg from contaminated soils, plants and surface water, but the consumption of contaminated fish from the lake appears to be the main route of exposure for humans.     

Cytotoxicity in the frog (Fejervarya limnocharis) after acute cadmium exposure in vivo

Chromosome aberrations (CA) in frogs (Fejervarya limnocharis) exposed to 5, 10 and 20 mg/L of cadmium chloride (CdCl₂) for 24, 48 and 72 h were invetegated. Treated frogs were compared to a control group. Cadmium (Cd) was not detected in the water or control frogs. The highest Cd concentrations in water and frog samples were found at 20 mg/L exposed for 72 h. The water samples indicated that exposure to 10 mg/L of Cd for 24 h was significantly different from the control (p < 0.05). Cd concentrations in frogs differed significantly between the control and experimental groups (p < 0.05). The cytotoxicity assessment revealed ten types of CA in the frogs, including single chromatid gap (SCG), isochromatid gap, single chromatid break, isochromatid break, iso-arm fragmentation, single chromatid decomposition, centric fragmentation, centromere gap, deletion and fragmentation. The most common CA in the study was SCG. The statistical analysis indicated significant differences in the percentage of cells with CA for exposures of 20 mg/L (24 h), 10 and 20 mg/L (48 h) and 5, 10 and 20 mg/L (72 h) compared to the control (p < 0.05). The results of this study show that high Cd concentrations and long duration exposure can cause CA in frogs.     

Evaluation of organochlorine and organophosphorus pesticides residues in the sediment and muscles of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) fish from a River Nile Canal,Egypt

The paper reports the levels of multi-pesticide residues in the sediment and fish (Oreochromis niloticus) muscle collected from Bahr Shebeen Canal (BSC), a River Nile Canal, from September 2014 to December 2015. Samples were analysed using capillary GC chromatography, and average pesticide residue concentrations were determined. The results indicated the presence of different types of organophosphorus (OPPs) and organochlorine (OCPs) pesticides in varying degrees. Both types of residue in the sediment samples were higher than in fish muscle. The spatial and seasonal variations of OPPs and OCPs levels in sediment and fish muscle are discussed. It was found that these levels were higher than those detected from other Egyptian localities and also higher than the international permissible limits. Therefore, it is recommended to monitor the pesticide residues continuously in this, and similar, water resources to ensure the protection of the aquatic food resources.     

Nitrification in modified sewerage stabilisation ponds prior to discharge into the Ugandan side of Lake Victoria

Large volumes of wastewater in the Ugandan capital Kampala have seriously polluted Lake Victoria, from which the city draws its freshwater. Untreated effluent drains directly into this lake. In tropical temperatures, oxidation ponds are used for wastewater treatment, especially for organic matter. This technology should be the focus of work to improve its efficacy, and thus to secure the sustainability of the lake and its freshwater fish which are marketed worldwide. A pilot scale plant was set up comprising an anaerobic tank, a facultative pond and four fibre‐glass maturation tanks. The total nitrification rates in the tanks T₁–T₄ were 5.5, 7.5, 10.1 and 6.4 (±0.4) mg‐N/l/day, respectively. For more efficient wastewater treatment stabilisation pond systems, a modification similar to that in T₃ should be considered. T₃ was constructed with biofilm attachment surfaces in a manner which allowed effluent to be channelled round them, contrary to direct T₁ flow which is currently in use.     

Potential of citric acid to alter pH and metal uptake in reeds in acid mine drainage solutions

Phragmites australis (common reed) is often used to treat acid mine drainage (AMD) sites contaminated with high concentrations of heavy metals and low pH. This study investigated the effects of different levels (low 0.34 g/L, middle 17.86 g/L and high 33.62 g/L) of the biodegradable chelator citric acid (CA) on pH change, metal (i.e. Fe, Al and Mn) accumulation and translocation in reeds cultured in aqueous AMD contaminated media for 4 and 12 weeks. The results indicated that CA inhibited further deceases in AMD pH as well as increased Fe and Mn accumulation in both belowground and above ground tissues of reeds. As expected, increasing CA dosage and treatment time increased metal accumulation in plants. By 12 weeks, 0.18 ± 0.01 mg Mn/g, 56.78 ± 7.63 mg Fe/g and 0.60 ± 0.01 mg Al/g were accumulated in roots; while 0.06 ± 0.01 mg Mn/g; 6.38 ± 0.06 mg Fe/g; and 0.19 ± 0.01 mg Al/g were sequestered in stems of reeds treated with 33.62 g/L CA. Further research is needed to study the application of CA to enhance the phytoremediation efficiency of AMD contaminated field.     

Assessment and biomonitoring of aquatic pollution by heavy metals (Cd,Cr, Cu,Pb and Zn) in Hammam Grouz Dam of Mila (Algeria)

Concentrations of Cd, Cr, Cu, Pb and Zn were determined in water, sediment and tissues of fish (Cyprinus carpio and Barbus setivimensis) from November 2014 to August 2015, in order to estimate the aquatic pollution in Hammam Grouz dam, by the technique of atomic absorption spectrophotometry. The concentrations of heavy metals in the water and sediment were higher than the WHO standards. The calculation of Bioconcentration factor showed that all fish species studied have accumulated heavy metals in their tissues (gill, liver, muscle and kidney). The concentrations of metals in B. setivimensis were higher than those in C. carpio. The highest concentration of heavy metals was recorded in the gill while the lowest was recorded in the muscle and kidney. Our study reveals that these fish species can be used as bioindicators in the biomonitoring of metallic pollution in aquatic ecosystem.     

Impact of urbanization on the quality of water in a natural reservoir: a case study with the Deepor Beel in Guwahati city,India

The Deepor Beel is a natural, freshwater wetland in the south-west corner of Guwahati, India. The Beel harbours a large number of migratory aquatic birds, especially in winter, and is a Ramsar site since 2002. The wetland provides livelihood to the people of the surrounding villages through collection and sale of fish, nymphaea nuts and flower, ornamental fish, orchids, medicinal plants, etc. The water quality of the Beel is threatened by excessive fishing, hunting of water birds, pollution from pesticides and fertilizers and infestation by water hyacinth. The present work reports on the water quality of the wetland by continuous monitoring from February to July, covering the dry, temperate period and the wet, hot and humid period. Sampling was carried out at 10 sites for physical and aggregate properties, metallic and nonmetallic constituents, organic contaminants and microbiological parameters.     

Acute toxicity of 12 industrial chemicals to freshwater and saltwater organisms

Aquatic animal toxicity is a major criterion used by the U.S. EPA to designate and classify hazardous substances other than oil. This research developed basic toxicity data for twelve industrial chemicals with which little or no previous testing had been done. Static 96h toxicity tests were performed with one freshwater species (fathead minnow, Pimephales promelas) and one saltwater species (grass shrimp, Palaemonetes pugio or white shrimp, Penaeus setiferus) on the following chemicals: ammonium fluoride, arsenic trisulfide, benzoyl chloride, benzyl chloride, cupric acetate, o-dichlorobenzene, p-dichlorobenzene, mercuric acetate, mercuric thiocyanate, resorcinol, sodium hypochlorite and toluene-2,4-diisocyanate (TDI). As defined by 96 h LC50's ≤ 500 mg l⁻¹, all 12 chemicals were hazardous to freshwater minnows, and all but TDI were hazardous to saltwater shrimp. The physicochemical behaviors of the compounds greatly influenced their aquatic toxicities.     

Assessment of heavy metals contamination and its effects on oyster (Saccostrea cucullata) biometry parameters in the Asaluyeh port coasts,Persian Gulf,Iran

The current study examines biometric parameters and concentration of some heavy metals in soft tissues of Saccostrea cucullata in the Asaluyeh coast, Persian Gulf, Iran. The metals concentration in the soft tissue of the Saccostrea cucullata ranged as: Zn: 765–3411 mg kg^?1, Cu: 120.3–580.6 mg kg^?1, Cd: 0.13–3.5 mg kg^?1, As: 0.39–3.3 mg kg^?1, Pb: 0.05–1.64 mg kg^?1, Ni: 0.02–0.44 mg kg^?1, V: 0.06–0.32 mg kg^?1, Cr: 0.02–0.16 mg kg^?1 and Hg: 0.002–0.068 mg kg^?1. The results showed that the concentration of total heavy metals in oysters of the control station (CA) is usually lower. The results also indicated lack of correlation between oyster biometric parameters and bioaccumulated heavy metals, except between Cu and longitudinal diameter (R = 0.77). The concentration of heavy metals is higher than limits recommended by the World Health Organization, except for Cd and Pb.     

Effects of lead toxicity on the total chlorophyll content and growth changes of the aquatic plant Ceratophyllum demersum L.

This paper reports results of a laboratory-scale experiment conducted to determine the effects of different initial concentrations of a toxic heavy trace metal (lead) on the total chlorophyll (a + b) content of aquatic plant tissues Ceratophyllum demersum L., and also to monitor the visible growth changes during the experiment under different lead concentrations (2, 4 and 6 mg/L), as well as in control plants (without any addition of lead nitrate solution). Lead concentrations in water and plant samples were determined using AAS, where the total chlorophyll content in plant leaf tissues was measured every 15 days during the experimental period using a UV/VIS Spectrophotometer, Model 160A, Shimadzu, with wavelengths of 665 and 649 nm. The results showed that the content of total chlorophyll decreased noticeably, with increasing initial concentrations of lead throughout the exposure time. Decreases in total chlorophyll content in the tissues of C. demersum over the period of the experiment were accompanied by different morphological changes in the plants, depending on the initial lead concentration and exposure duration. These changes in morphology and growth affected the number and length of branches, the number of leaves and the number of leaflets.     

Comparing the anaerobic digestion of Ascophyllum nodosum,the organic fraction of municipal solid waste and white rice in batch reactors

The biogas potential of marine macroalga Ascophyllum nodosum was compared with the organic fraction of municipal solid waste (OFMSW) and white rice to determine the applicability of the feedstock for anaerobic digestion. For OFMSW three dry matter contents were compared, 3%, 10% and 25%, to determine the effect of dry matter on methane yield. Biogas was evolved in each system, but the rate of evolution of biogas changed with moisture content. The highest total methane yield was obtained from 3% OFMSW but A. nodosum yielded more methane at 176±37.62 L/kg VS than white rice and the drier anaerobic digestion of OFMSW. The substrates were digested using wastewater treatment plant inoculum to determine gas yield and gas quality under batch mesophilic digestion conditions.     

Potential nitrous oxide (N2O) emission from aquaculture in Nepal

Nitrous oxide has a greenhouse potential 310 times that of carbon dioxide (CO₂) over a 100-year lifespan. N₂O has been produced in the aquaculture system via nitrification and denitrification. This study mainly concerns estimation of the annual N₂O emission from aquaculture in Nepal and potential emission by the years 2020 and 2030. Theoretically, this study estimates emission of N₂O-N from aquaculture in Nepal in 2020 and 2030 to be 1.1 × 10⁸ g N₂O-N (±5.2%) and 2.24 × 10⁸ g of N₂O-N (±2.5%) of 95% confidence limit, respectively, with the emission factor 1.69 g of N₂O-N/kg of fish. In terms of carbon dioxide equivalent (CO₂eq), these values are 5.36 × 10¹⁰ g and 1.1 × 10¹¹ g, respectively, in 2020 and 2030, which accounts for 0.57% and 0.70% of Nepal’s CO₂ emission in 2020 and in 2030, respectively. This study also briefly deals with the parameters that stimulate N₂O emission and some potential technologies likely to reduce the N₂O emission in aquaculture. Greenhouse gas emission from aquaculture should be included by all countries in their estimation of global warming and climate change matters.