Preliminary studies on the use of the heterotrophic activity method to evaluate acid-stress effects in aquatic environments

This paper concerns the usefulness of the “heterotrophic activity method” in studying the effects of acidification on mineralization activity in a lake in which acid rain is simulated, and in an acid-stressed lake. In the fall, the rates of glucose mineralization by the planktonic microflora of Bethel Lake followed Michaelis-Menten kinetics at the in situ pH (7.5 and at the two experimental pH's (5.5 and 5.0). Turnover times for glucose increased with decreasing pH and, correspondingly, V_max values decreased with decreasing pH. During ice-cover, only the in situ pH (6.85) gave a Michaelis-Menten response for glucose mineralization. At the experimental pH's, glucose mineralization activity was negligible. Analyses for soluble copper and nickel, the most important heavy metals in this environment with respect to concentration, indicated that the reduced glucose mineralization rates were not the result of our acidification increasing the heavy metal concentrations (and, therefore, their toxicity).For the acid-stressed Silver Lake, glucose mineralization was negligible at the in situ pH (4.3) and at the experimental pH's (5.5 and 7.0) as well. The application of this method in the study of acid-stressed lakes is discussed.     

The effect of heavy metals on laboratory populations of two polychaetes with comparisons to the water quality conditions and standards in Southern California marine waters

Polychaetous annelid assays were performed with laboratory inbred cultures of juvenile and adult Neanthes arenaceodentata and Capitella capitata to cadmium, chromium, copper, lead, mercury, and zinc in sea water. Data were presented as 96-h and 28-day LC₅₀ concentrations. Mercury and copper were the two most toxic with zinc and chromium generally the next most toxic followed by lead and cadmium. The adult stages of both species were more tolerant to these metals than the juveniles. Comparisons of these six metals present in the two large domestic sewage outfalls in Los Angeles County indicate that the amount of copper and zinc present in the effluent exceeds the 28-day LC₅₀ of these two polychaetes. The results were compared to the water quality standards for discharges in the State of California.     

Cycling of elements in duckweed (Lemna perpusilla) in an ash settling basin and swamp drainage system

Duckweed (Lemna perpusilla Torrey), inhabiting a stream-swamp drainage system that received high quantities of coal ash or thermal discharges from a fossil fuel power plant, was the only abundantly occurring macrophyte. For a period of 1 yr, accumulations of 22 elements in components of this system (water, sediments and duckweed) were determined at six stations using neutron activation analysis. Abiotic processes (e.g. settling, solution) were important in cycling some elements including heavy metals, while some potentially toxic elements (e.g. Hg and Se) were bioconcentrated by duckweed. In those stations where ash influence was greater in water and sediments, elemental uptake by duckweed was also higher. Approximately 1200 m² of swamp area was necessary to facilitate the removal of most ash influence. The use of duckweed as food may be a potential source of bioaccumulation or biomagnification of toxic elements by migratory wildfowl that frequent ash-impacted drainage systems.     

Determination of organochlorines in river sediment by capillary gas chromatography: Application to Dutch river sediment

An analytical method is described for the capillary gas chromatographic determination of 17 organochlorines, such as HCB, α-, β- and γ-HCH, aldrin, dieldrin, endrin, isodrin, telodrin, C-601 (1,2,3,4,7,7-hexachlorobicyclo-[2,2,1]-heptadieen-2,5), C-773 (1,2,3,4,5,7,7-heptachlorobicyclo-[2,2,1]-hepteen-2), heptachlor, β-heptachlorepoxide and the DDT-complex, in soil and river sediment. C-601 and C-773 are by-products of the aldrin and dieldrin synthesis. Several solvents were compared for the extraction from clay, peat and river sediment. Acetone gave the best results, also after a long period between spiking of soil and sediment samples with organochlorines and extraction. 14 Organochlorines were determined without interference from PCBs. The analysis of heptachlor, aldrin and p·p′-DDT can be interfered with by PCB components.The results of a monitoring program in tributaries of the Rhine River, Western Scheldt and in some harbour basins of Rotterdam are presented. HCB occurred frequently. The most contaminated sediment was found in a harbour basin near a pesticide producing plant. In this sediment the mean concentrations were 0.86 mg kg⁻¹ and 0.18 mg kg⁻¹ for dieldrin and endrin, respectively, on a dry weight basis.     

Toxicity of cadmium, cobalt, uranium and zinc to Zoogloea ramigera

The toxic effects of cadmium, cobalt, uranium and zinc to the bacterium Zoogloea ramigera have been studied. This organism, which is abundant in sewage-treatment plants, responded to media supplemented with heavy metals by showing a prolonged lag phase and by decreasing its growth rate. The length of the lag phase was proportional to the metal concentration when Z. ramigera was exposed to cadmium, cobalt and zinc. When exposed to uranium (uranyl ions) the organism altered its growth behavior by showing an extended lag phase almost independent of the metal concentration. The order of toxicity of the metals to Z. ramigera was Cd²⁺ = Zn²⁺ > Co²⁺ > UO₂²⁺.     

Behavior of Mn, Fe, Cu, Zn, Cd and Pb discharged from a wastewater treatment plant into an estuarine environment

To obtain information on the fate of trace metals discharged to an estuarine environment, analyses have been made on water and sediment samples from Back River, MD., and on effluent from the large wastewater treatment plant that discharges there. Within 2–3 km of the outfall, the concentration (in μg 1⁻¹) of all metals decreases as follows: Mn, > 120-90; Fe, > 570-300; Cu, 53-7; Zn, 280-9; Cd, 3.5-0.5 and Pb, 31-<4. Except possibly for Mn and Fe, these decreases are much greater than can be ascribed to simple dilution, so physical, chemical or biological processes must be removing metals to the sediments. Correspondingly, sediment concentrations of Cu, Zn, Cd and Pb are approximately one order of magnitude higher than normally found in uncontaminated areas. After the initial decrease, concentrations of Mn and Cd in the water begin to rise again, suggesting remobilization from the sediments. Comparison of the estimated annual discharge of 8 trace metals to the Chesapeake Bay from wastewater treatment plants and from rivers suggests that the wastewater input may be within one order of magnitude of the fluvial input for Cr, Cu, Zn, Cd and Pb. Of the metals studied, Cd presents the greatest potential for serious pollution because its input from wastewater probably exceeds fluvial input, it appears to be readily remobilized from sediments, and it is known to be toxic to many organisms.     

A toxicity warning monitor using the weakly electric fish, Gnathonemus petersi

A technically simple fish monitor was developed using the weakly electric fish, Gnathonemus petersi, as the test organism. The test system consists of a plexiglass test chamber (21., 27°C) with a flow-through of 4–5 times the chamber volume per hour. The spontaneous electric organ discharges (EOD) are recorded as activity signals. EODs, which have a potential of about 500 mV, last 0.3 ms and they can be converted to computer-compatible signals by a simple amplifier. The EOD-activity is analyzed by a low-cost desk-top computer. Two different modes of analysis which represent two levels of response sensitivity, are possible either alternatively or simultaneously. The toxicity response of Gnathonemus petersi was measured in experiments with the toxicants Hg²⁺, Cu²⁺, NaAsO₂ and CN⁻. The sensitivity to acutely toxic concentrations was found to be as high as that of trout or minnows.     

Speciation (including adsorbed species) of copper, lead, nickel and zinc in the Meuse River: Observed results compared to values calculated with a chemical equilibrium computer program

The adsorption of trace metals on sediments of the Meuse River was interpreted in terms of competition between metals and protons for surface sites. Surface constants (^*β₁^surf) were determined for Cu, Zn and Cd (10^−1.8, 10^−3.6 and 10^−3.7). The constants for Pb, Ni, Ca and Mg (10^−1.7, 10^−3.8, 10^−6.5 and 10^−5.2) were estimated using a correlation between hydrolysis and surface constants. A chemical equilibrium computer program in which surface sites (for adsorption reactions) are treated as conventional ligands was used to calculate the speciation of Cu, Pb, Ni and Zn in the Meuse River. Calculated values of the adsorbed/dissolved distribution agreed well with observed values, after some realistic data manipulation. This work indicates that dissolved trace metal concentrations in the Meuse River are controlled by adsorption and not by precipitation mechanisms. The relationship between organic matter and suspended matter greatly influences the adsorption of metals like Cu and Pb.     

Mercury in edible mushrooms and underlying soil: Bioconcentration factors and toxicological risk

Wild growing mushrooms are a popular delicacy in many countries, but some species accumulate high levels of toxic heavy metals, e.g., mercury, both in unpolluted and mildly polluted areas. In this study, we examined the accumulation capacity of mercury in edible mushrooms in relation to certain factors and their possible toxicological implications. Total concentrations of mercury were determined by an anodic stripping voltammetric technique using a gold disc as the working electrode in 238 samples of the fruiting bodies of 28 wild growing edible mushrooms species and the underlying soil. The mushrooms were collected from different sites in the province of Lugo (NW Spain). The hymenophore (H) and the rest of the fruiting body (RFB) were analysed separately. The highest mean mercury concentrations (mg/kg dry weight) were found in Boletus pinophilus (6.9 in H and 4.5 in RFB), Agaricus macrosporus (5.1 in H and 3.7 in RFB), Lepista nuda (5.1 in H and 3.1 in RFB) and Boletus aereus (4.6 in H and 3.3 in RFB), while the lowest was found in Agrocybe cylindrica (0.34 in H and 0.26 in RFB) and Fistulina hepatica (0.30 in H and 0.22 in RFB). All mushroom species accumulated mercury (BCF > 1) in relation to the underlying soils. There were no statistically significant differences between the mercury levels in the hymenophore and in the rest of the fruiting body. The total mercury concentrations were compared to data in the literature and to levels set by legislation. It was concluded that consumption of the majority of the studied mushrooms is not a toxicological risk as far as mercury content is concerned, although the species B. pinophilus, A. macrosporus, L. nuda and B. aereus should be consumed in low amounts.     

Accumulation de quelques metaux lourds (Cd, Cu, Pb et Zn) chez l'eperlan (Osmerus mordax) preleve sur la rive Nord de l'Estuaire du Saint-Laurent

Heavy metals in trace amounts are normal constituents of marine organisms. At sufficiently high concentrations, heavy metals are toxic to living organisms and so it is important to know by how much their concentration may be increased before effects on marine or estuarine populations can be detected or commercial species become unsuitable as food. A method of removing metals is by storage in a particular tissue. Several different sites for storing metals were investigated and concentrations of Cd, Cu, Pb and Zn were examined in muscle, liver and gonads of the smelt (Osmerus mordax) from the North shore of the St Lawrence estuary. Copper and zinc are constituents of several enzymes and are absolutely essential for normal growth and development, while cadmium and lead are not known to have necessary physiological function. A modified wet digestion procedure was used to prepare biological samples for the determination of trace elements by flameless atomic absorption spectrophotometry procedure, using calibration standards made up in a matrix of similar acidity (Table 1). NBS reference material bovine liver was analyzed along with the samples and the results were within the specified tolerance (Table 2). Analyses were reported on a dry weight basis (Table 3) and the correlations with total body weight were determined by regression analysis. Copper (range 0.3–3.3 μg g⁻¹) and zinc (range 19–38 μg g⁻¹) in muscle fillets were found to be negatively correlated with total body weight (Fig. 1). Apparent decreasing concentrations in these two metal levels in muscle sample with increasing body weight were possibly due to factor such as dilution with growth. Growth may dilute metal concentrations in an organism if tissue is added faster than metal. Livers and gonads contained greater levels of the four metals than somatic muscle. Liver metal concentrations of Zn (range 29–108 μg g⁻¹) and Cd (range 0.06–0.37 μg g⁻¹) increased with total body weight. All equations fit data at P < 0.01 (Fig. 2). Positive correlations between size and metal concentrations suggest that net uptake may occur. Inessential, slowly exchanging metals such as Cd appear to reflect an uptake which tend to become a cumulative process (age dependence of concentrations). The occurrence of insignificant correlation between liver concentrations of Cu (mean value: 4 μg g⁻¹) and environmental concentrations of this metal was consistent with equilibration. Since fish are known to possess the metal binding protein metallothionein, a sequestering agent, detoxification of these metals in fish liver may be by sequestration rather than elimination. Increasing metal concentrations in liver may represent storage of sequestered products in that organ. In the gonads, no significant relationship exists between total body weight and trace metal contents. Results of t-test indicated that females had significantly greater Cu and Zn concentrations, but no significant difference existed between males and females for Cd concentrations (Figs 3 and 4). Thus, the relation between concentration and total body weight appears to be specific as to the species, tissues analyzed and environmental conditions. The comparison of metal concentrations in fish to assess variations in contamination levels requires understanding the relationship between metal concentration and body size within each population.     

Attenuation of heavy metal toxicity of the activated sludge process by treatment with ferric chloride

Industrial wastes containing heavy metals can interfere with the normal operation of municipal wastewater treatment plants utilizing biological treatment processes. It is well known, however, that activated sludge can become acclimated to toxic levels of heavy metals if the dosages are increased gradually. Although such an acclimation procedure could prevent inhibitory effects of slug loads of toxins, the use of toxic heavy metals for normal plant operation is too perilous for consideration. It is, however, acceptable to utilize a nontoxic metal that may give general tolerance to toxic metals.

Laboratory experiments were conducted to examine the use of ferric chloride acclimation for treatment against heavy metal toxicity of an activated sludge process. The oxygen uptake of acclimated and unacclimated seed was measured by respirometry to determine the inhibitory effects of Ag and Pb.

The toxic effects of Ag and Pb were greatly reduced for acclimated seed. The experimental data area utilized in kinetic rate equations, and families of curves are developed to show the inhibition of Ag and Pb at a range of concentrations when the activated sludge is acclimatized at different concentrations of Fe(III).     

Antibiotic resistance and tolerance to heavy metals demonstrated by environmental pathogenic bacteria isolated from the Kahwa River,Bukavu Town,Democratic Republic of the Congo

Increasing concentration of heavy metals and antibiotics within bacterial microenvironments contribute to medical problems. This research confirmed the presence of enteropathogenic bacteria in the sediment and water of Kahwa River. Vibrio cholerae, Shigella dysenteriae, Salmonella typhi and Salmonella paratyphi showed resistance to antibiotics and tolerance to heavy metals. The bacteria, particularly Vibrio, were extensively resistant to Ampicillin; less so to Chloramphenicol, Co-trimoxazole and Tetracycline with a relatively reduced resistance shown to Ciprofloxacin. Higher levels of antibiotic resistance were noticed in bacteria isolated from river sediment when compared to bacteria isolated from river water (p < 0.05). Tolerance to cadmium and lead was also more obvious in bacteria isolated from river sediment. An increasing association was observed between multiple antibiotic resistance and tolerance to heavy metals. Bacterial growth in the presence of cadmium was restricted when compared to lead.     

Effects of copper, zinc and cadmium on Selanastrum Capricornutum

The algicidal and algistatic effects of copper, zinc and cadmium on Selanastrum capricornutum, a unicellular green algae were analyzed by using a modification of the Algal Assay Procedures Bottle Test.Algicidal concentrations of copper, zinc and cadmium were 0.30, 0.70, and 0.65 mg 1⁻¹. Treatment of Selanastrum with various concentrations of the metals resulted in similar growth rates characterized by extended lag growth phases.Combinations of copper, zinc and cadmium were similar in toxicity to equal concentrations of zinc. Combinations of copper and cadmium resulted in a greater growth rate than equal concentrations of copper suggesting that cadmium inhibits copper toxicity.Selanastrum was able to exist in waters from the upper South Fork and North Fork of the Coeur d'Alene River where zinc and other metals were in low concentration. However, the algae was not able to tolerate zinc concentrations greater than 0·5 mg 1⁻¹ from waters of other parts of the drainage. These observations were consistent with laboratory findings where 0.7 mg 1⁻¹ zinc was algicidal and 0.1 mg 1⁻¹ inhibited the growth of Selanastrum.     

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.     

Electrochemical determination of pollutants in sea water: Toxic substances and nutrients

Coastal marine waters have a wide variety of important human uses and therefore must be protected against contamination. The main sources of their pollution (by toxic substances and nutrients) are the discharge of municipal sewage and runoff from agricultural areas. Excessive nutrient enrichment in the form of inorganic nitrogen (NH₄⁺, NO₂^?, NO₃^?) may be directly estimated by the use of ion selective electrodes (ISE), whereas the inorganic phosphorus can only be estimated indirectly. The total content of N, P and heavy metals may be estimated after decomposition of organic substances, using the ISE method in the case of P and N determination and the differential pulse anodic stripping voltammetry (DPASV) method for determining the heavy metals.     

Heavy metals: confounding factors in the response of New Zealand freshwater fish assemblages to natural and anthropogenic acidity

Acidification of freshwaters is a global phenomenon, occurring both through natural leaching of organic acids and through human activities from industrial emissions and mining. The West Coast of the South Island, New Zealand, has both naturally acidic and acid mine drainage (AMD) streams enabling us to investigate the response of fish communities to a gradient of acidity in the presence and absence of additional stressors such as elevated concentrations of heavy metals. We surveyed a total of 42 streams ranging from highly acidic (pH 3.1) and high in heavy metals (10 mg L⁻¹ Fe; 38 mg L⁻¹ Al) to circum-neutral (pH 8.1) and low in metals (0.02 mg L⁻¹ Fe; 0.05 mg L⁻¹ Al). Marked differences in pH and metal tolerances were observed among the 15 species that we recorded. Five Galaxias species, Anguilla dieffenbachii and Anguillaaustralis were found in more acidic waters (pH< 5), while bluegill bullies (Gobiomorphus hubbsi) and torrentfish (Cheimarrichthys fosteri) were least tolerant of low pH (minimum pH 6.2 and 5.5, respectively). Surprisingly, the strongest physicochemical predictor of fish diversity, density and biomass was dissolved metal concentrations (Fe, Al, Zn, Mn and Ni) rather than pH. No fish were detected in streams with dissolved metal concentrations > 2.7 mg L⁻¹ and nine taxa were only found in streams with metal concentrations < 1 mg L⁻¹. The importance of heavy metals as critical drivers of fish communities has not been previously reported in New Zealand, although the mechanism of the metal effects warrants further study. Our findings indicate that any remediation of AMD streams which seeks to enable fish recolonisation should aim to improve water quality by raising pH above ≈ 4.5 and reducing concentrations of dissolved Al and Fe to < 1.0 mg L⁻¹.     

Biomonitoring of maritime pollution by heavy metals (Pb and Zn) in the coast of Jijel (Algeria)

This paper reports a study of pollution in the coastal waters of Jijel, Algeria, using algae Ulva lactuca and Corallina officinalis as bioindicators. Samples of seawater and algae were collected at four different stations from the coast of Jijel, during the period of April–June 2014. The heavy metal content (Pb and Zn) was determined in seawater and in the algae tissue by the technique of atomic absorption spectrophotometry. In seawater, the contents of heavy metals vary from 0.017 to 0.03 mg/l (Pb) and 0.235 to 0.873 mg/l. In the algae tissues, metals concentrations vary between 1.88 to 6.25 μg g^?1 dry weight (Pb), and from 92 to 178.9 μg g^?1 dry weight (Zn). These levels differ by site and species. The calculation of the bioconcentration factor (BCF) leads us to conclude that algae bioaccumulate significant levels of Pb and Zn metals in their tissues. Our results shows that the species of C. officinalis bioaccumulate the metals Pb and Zn more than U. lactuca, where, high biosorption of Zn was observed with BCF values between 203.21 and 238.40. Zn content in seawater and algae tissues appear higher than standards set by USEPA and guides values of Certified Reference Materials, but Pb levels appear lower than this standard.     

The toxicity of chlorine to a common vascular aquatic plant

Myriophyllum spicatum was exposed to various chlorine concentrations on a continuous and intermittent basis in 96-h toxicity studies utilizing a proportional diluter. Continuous exposure to chlorine concentrations as low as 0.05 mg l⁻¹ total residual chlorine (TRC) depressed shoot and total plant dry weights approx. 30% relative to controls. Shoot length was depressed approx. 16% at this concentration. Chlorophyll a was depressed 25% at 0.1 mg l⁻¹ TRC. However, intermittent exposure of plants to chlorine for three 2-h periods daily for 96 h indicated an insensitivity to repeated short term chlorine exposure at all concentrations but 1.0 mg l⁻¹ TRC. These results indicate that high level chlorine discharges from waste water facilities and electric generating plants could be a contributing factor impacting nearby submerged aquatic vegetation.     

Heavy metal removal in anaerobic semi-continuous stirred tank reactors by a consortium of sulfate-reducing bacteria

Removal of heavy metals by an enriched consortium of sulfate-reducing bacteria (SRB) was evaluated through the abundance of SRB, sulfate reduction, sulfide production and heavy metal precipitation. Five parallel anaerobic semi-continuous stirred tank reactors (CSTR, V = 2 L) (referred as R1-R5) were fed with synthetic wastewater containing mixtures of Cu²⁺, Zn²⁺, Ni²⁺, and Cr⁶⁺ in the concentrations of 30, 60, 90, 120, and 150 mg L⁻¹ of each metal and operated with a hydraulic retention time of 20 days for 12 weeks. The loading rates of each metal in R1-R5 were 1.5, 3, 4.5, 6, and 7.5 mg L⁻¹ d⁻¹, respectively. The results showed that there was no inhibition of SRB growth and that heavy metal removal efficiencies of 94-100% for Cu²⁺, Zn²⁺, Ni²⁺, and Cr⁶⁺ were achieved in R1-R3 throughout the experiment and in R4 during the first 8 weeks. The toxic effect of heavy metals on the SRB consortium was revealed in R5, in which no SRB could survive and almost no heavy metal precipitation was detected after four weeks of operation.     

Accumulation of zinc, cadmium and lead by field populations of Lemanea

A study has been made of the concentrations of zinc, cadmium and lead in populations of the red alga Lemanea growing in fast-flowing rivers in Britain, France. Germany, Ireland and Sardinia (Italy). The sites were selected to provide a wide range of aqueous concentrations of these metals. Many of the sites are influenced by past or present mining activities and Lemanea was found at aqueous concentrations of zinc up to 1.16 mg 1⁻¹. In contrast to previous studies with filamentous green algae, no evidence could be found to support the hypothesis that populations differ genetically in their ability to tolerate these heavy metals. Samples of alga consisted of pooled 2 cm long terminal tips of filaments detached from approx. 1 cm² rock surface. Significant positive correlations were found between the logarithm of the mean concentration of zinc, cadmium and lead in four such samples collected from within 10 m reaches at 59 sites and the logarithm of the concentration of each metal in both unfiltered and filtered water. The enrichment ratios for each metal decreased with increasing aqueous metal concentrations. Although the aqueous concentrations of the three metals were strongly intercorrelated, differences in the ratio of metal concentrations were reflected in the composition of Lemanea filaments. The results suggest that high levels of calcium (and/or magnesium) result in decreased uptake of zinc. Intensive sampling from a single population showed that part of the zinc content of filaments is sensitive to short-term fluctuations in concentrations in the surrounding water. In the particular population studied this was about 20%; a similar percentage could be eluted in the laboratory with EDTA. Transplants of Lemanea were made between reaches with different aqueous concentrations of zinc and in all cases the zinc concentration in filament tips increased or decreased to stabilise at a concentration similar to that in filaments native to the reach. It is suggested that chemical analyses of natural or transplanted populations of Lemanea could provide a valuable aid in monitoring contamination of rivers by zinc, cadmium or lead.