Particulate and dissolved trace metals in Lake Ontario

Particulate metal concentrations in the nearshore waters of Lake Ontario have been determined to be 690 ng l⁻¹ for Cu; 40 ng l⁻¹ for Cd; 180 ng l⁻¹ for Ni; 1690 ng l⁻¹ for Zn; 2100 ng l⁻¹ for Mn; and 700 μg l⁻¹ for Fe. These values are considerably higher than the particulate metal concentrations in the offshore waters: 130, 8, 34, 230, 110, 260 and 9000 ng l⁻¹ for Cu, Cd, Ni, Zn, Pb, Mn and Fe respectively. In general, 50–80% of the Cu, 10–40% of the Ni, 20–60% of the Cd and >60% of the Pb in the lake water were bound to the suspended particulates. From the standing crop of the particulate metals and the estimated rates of their deposition on the lake bottom, the residence times of the particulate metals in the lake water column have been estimated to be about 0.5 yr. on the average. The suggestion is made that particulate organic matter may be an important vehicle for metal transport to the Lake Ontario sediments.     

Concentrations of heavy metals in small Norwegian lakes

As part of regional surveys of lakes in Norway the concentrations of Zn, Pb, Cu and Cd were measured in surface- and bottom-water samples collected from representative, small, pristine lakes (136 in southern Norway sampled in October 1974, 58 resampled in March 1975, and 77 in northern Norway sampled in March 1975). The lakes, a statistically representative sample of small lakes in Norway, were chosen such that their watersheds are undisturbed. Heavy-metal concentrations in these lakes thus reflect only natural inputs and anthropogenic inputs via the atmosphere.The generally low concentrations (Zn 0.5–12.0 μg l⁻¹; Pb 0–2.0 μg l⁻¹; Cu 0–2.0 μg l⁻¹; Cd 0.1-0.5 μg l⁻¹) measured in lakes in central and northern Norway provide estimates of natural “background” levels. These estimates may be too high because they include the global-scale deposition of heavy metals from the atmosphere which has increased as a result of industrial activities.Concentrations of Zn and Pb in lakes in southernmost and southeastern Norway lie above these “background” levels, apparently because of atmospheric deposition associated with the acidic precipitation that falls over southern Scandinavia. Increased heavy-metal concentrations in acid lakes may also be due to increased mobilization of metals due to acidification of soil- and surface-waters.     

Zinc, cadmium and lead in water, sediments and submerged plants of the Derwent Reservoir, Northern England

A partial budget is presented of the zinc, cadmium and lead entering the Derwent Reservoir. The mean levels in the water column upstream of the site of inflow are: Zn, 0.216 mg 1⁻¹ ; Cd, 0.003 mg 1⁻¹; Pb, 0.065 mg 1⁻¹; the levels after passage through the 4.1 km² reservoir fall by: Zn, 70.3%; Cd, 98.3%; Pb, 89.2%. Most of these metals are deposited in sediments, the mean values for which are: Zn, 1035 μg⁻¹; Cd, 13μg⁻¹; Pb, 827μg⁻¹. Lead, a higher percentage of which occurs as particulate material, is deposited more rapidly than zinc; this effect is especially obvious when streaming of colder water along the bottom of the reservoir takes place at the time of floods. Macroscopic plants are only occasional in this reservoir, due perhaps in part to heavy metal toxicity. Of the two most common submerged species, Nitella flexilis probably accumulates almost all of its metal content directly from the water, but the data suggest that sediments are a source of some of the heavy metals accumulated by Glyceria fluitans.     

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.     

Submersible integrating water sampler for heavy metals

A simple submersible apparatus for the collection of a continuous composite water sample, suitable for heavy metal determination, is described. A comparison between results obtained for Cd, Pb, Cu, Zn and Hg using this sampler and a series of hand collected samples showed a satisfactory level of agreement. The apparatus is suitable for pollution monitoring purposes in relatively shallow (<20 m) waters where the concentrations of Cd, Pb, Cu, Zn and Hg are expected to exceed 0.05, 0.2, 0.2, 0.4 and 0.02 μg l⁻¹ respectively.     

Distribution of species of Cu, Pb, Zn and Cd in a water profile of the Yarra river estuary

The behaviour of Cu, Pb, Zn and Cd in a highly stratified estuary was examined. The distribution of ionic and ‘organically bound” forms of the metals was determined by differential pulse anodic stripping voltammetry (dpasv) before and after u.v. irradiation. The two forms of the metals were compared with the water characteristics of salinity, temperature, turbidity, flow, and inorganic and organic carbon.Irradiation increased the concentration of all four elements detectable by dpasv. The greatest increase was for Cu in the 1 m depth river water which yielded 7.5 μg l⁻¹ before irradiation and 29 μg l⁻¹ after irradiation. Cu and Cd showed minimum concentrations in the seawater layer at 4 m depth, corresponding to the fresh seawater flowing upstream below the halocline. The concentrations of Cu and Cd were higher in the river water than in the underlying seawater. Zn concentration in the river water was lower than in the seawater. Relationships between the trace metal concentrations and the characteristics of the water column are not clear, but the direction of water movement is a major influence.     

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.     

The crayfish as a “biological indicator” of aquatic contamination by heavy metals

Cu, Cd. Mg, Mn and Ni concentrations in whole Cambarus bartoni, trapped from Nepahwin Lake, Joe Lake and Wizard Lake, lying at distances of 10, 30 and 150 km, respectively, from the Sudbury smelters in Northeastern Ontario, showed an inverse relationship with the distance of the habitat from the emission site. Highest concentrations of Cu were observed in the hepatopancreas, Cd in the hepatopancreas and the gut, Fe and Mn in the gut, and Mg in the exoskeleton. Tissue concentrations of Ni and Zn were highly variable. Differences between males and females at each sampling site were not significant at the 5% level. The general relationship between crayfish tissue metal concentrations at the three sites was Cu > Mg > Mn > Zn > Ni > Cd. This observed relationship, except for Mg and Mn, agreed with the concentration relationship of these metals in the water and the sediments (top 10–20 cm) in the three lakes. In laboratory studies, Cu concentrations in the hepatopancreas, gills, exoskeleton and the viscera increased significantly over the control during the 4-weeks exposure to 125,250 and 500 μg Cu 1⁻¹. Hepatopancreas, in general, had the highest Cu concentration, and the exoskeleton, the lowest. Relationship between Ni exposure and the tissue Ni concentrations in the four treatments was 800 μg Ni l⁻¹ > 400 μg Ni l⁻¹ = 200 μg Ni l⁻¹ > control, while between the exposure periods and the tissue Ni concentrations was week 4 > week 1 > week 3 = week 2. Highest Ni concentrations at the end of the 4-week exposure to Ni were observed in the gut, gills and the hepatopancreas, and the lowest in the viscera. The present study suggests that Cambarus bartoni is a reliable indicator of the presence of class B and borderline elements with specific gravity > 5 in the aquatic environment. However, their value as biomonitors of variations in Cu and Ni concentrations in freshwater ecosystems is debatable.     

Trace metals in the marine bivalve Macoma balthica in the westerschelde estuary, The Nertherlands. Part 3: Variability of the role of cytosol in metal uptake by the clams

Tellinid clams Macoma balthica were sampled every 2 months for 2.5 years at two locations from the Westerschelde estuary (The Netherlands) and submitted to in vitro short-term exposure to Cd, Cu and Zn. Total and heat-stable cytosolic metal concentrations have been measured before and after exposure to study the effects of the sampling season on metal uptake by the bivalve. We observed much higher uptakes of Cd and, to a lesser extent, Cu in winter than in summer, while Zn appears to be constantly regulated. These phenomena are amplified in the cytosol, especially for Cd, a non-essential element, for which the concentrations after exposure can reach 35–45 μg·g⁻¹ (dry wt.) in winter, but only a maximum of 0.5 μg·g⁻¹ in summer, all natural values being between 0.01 and 0.1 μg·g⁻¹ on average. The contents (μg) of the various elements, either at the total or at the cytosolic level, are not constant, hence showing that the seasonal body weight fluctuation of the clams (dilution or concentration effect) is not the only parameter responsible for the metal uptake variability. Furthermore, we have shown that the proportion of cytosolic metal is not constant, but increases with the absolute cytosolic concentration up to 35–40. Therefore, the cytosolic phase of the cells plays a growing role in Cd, Cu and Zn storage as long as their total concentration increases.     

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.     

Heavy metals in animals of Lake Balaton

Hg, Cd, Cu, Pb, Zn, Fe and Mn concentrations were measured in Chironomidae larvae, Crustacea plankton, as well as in various organs of mussels and fishes collected from the open water area of Lake Balaton. The values were comparatively low. However, there were significant differences in the metal concentrations of species and tissue.Most Cd was found in the gill of Unio pictorum L., most Pb, Zn and Mn in the gill of Anodonta cygnea L., most Cu in Crustacea plankton and in the liver of Abramis brama L., and most Hg and Fe in Chironomidae larvae. Low concentrations occurred in fishes, the lowest in the flesh of Stizostedion lucioperca L.Accumulation of metals in organs as compared with their concentration in the lake water was in the range of 3.4 × 10²−2.6 × 10³ for Hg; 7.0 × 10²−6.8 × 10³ for Cd; 3.3 × 10²−9.7 × 10³ for Cu; 6.9 × 10²−8.1 × 10³ for Zn; 1.5 × 10³−2.4 × 10⁴ for Pb; 3.5 × 10²−3.1 × 10⁴ for Fe; and 5.0 × 10¹−3.5 × 10⁵ for Mn.     

Anodic stripping voltammetric study of the lability of Cd, Pb, Cu ions sorbed on humic acid particles

The sorption of Cd, Pb and Cu by humic acid particles has been studied at μg l⁻¹ levels using A.S.V. on a Hg film electrode as the measuring technique. The variables examined included amount of solid present (0.01–0.2% w/v), initial metal ion concn (10–100 μg l⁻¹), systems pH (5.3, 6.35, 8.15) and base electrolyte composition. The calculated capacity for specific adsorption of the metal ions was a few mmol M²⁺ kg⁻¹, or less. The apparent lability of part of the sorbed material was examined by analysing the base solution before and after filtering, and by adding Chelex 100 particles to the suspension. Some sorbed Cd²⁺ was A.S.V. labile, another fraction transferred to the resin. The effect of solution reactions on uptake was studied by making the 1 M CH₃COONa base solution 0.2 M in a range of Na⁺ salts (8 different anions), or in carboxylic acid content (5 acids) or in compounds having S-type bonding groups. Formation of complex ions in solution altered the extent of metal ion uptake, and in the case of Cu A.S.V. peak size, shape and position were varied. It is suggested that natural waters containing suspended matter should be analysed by A.S.V. “as received”, as well as after filtration since response differences provide guidance in respect to the lability of sorbed ions.     

Mercury fluxes in a natural forested Amazonian catchment (Serra do Navio, Amapá State, Brazil)

Mercury (Hg total) fluxes were calculated for rainwater, throughfall and stream water in a small catchment located in the northeastern region of the Brazilian Amazon (Serra do Navio, Amapá State), whose upper part is covered by a natural rainforest and lower part was altered due to deforestation and activities related to manganese mining. The catchment area is 200 km from the nearest gold mining (garimpo). Minimum and maximum Hg concentrations were measured monthly from October 1996 to September 1997 and were 3.5–23.4 ng l⁻¹ for rainwater, 16.5–82.7 ng l⁻¹ for throughfall (March–August 1997) and 1.2–6.1 and 4.2–18.8 ng l⁻¹ for stream water, in natural and disturbed areas, respectively. In the natural area, the inputs were 18.2 μg m⁻² year⁻¹ in rainwater and 72 μg m⁻² year⁻¹ in throughfall. This enrichment was attributed to dry deposition. The stream output of 2.9 μg m⁻² year⁻¹ indicates that Hg is being recycled within the forest as other chemical species or is being retained by the soil system, as confirmed by the cumulative Hg burden in the 0–10 cm surface layer, which was 36 480 μg m⁻². When the disturbed area of the catchment was included, the stream output was 9.3 μg m⁻², clearly indicating the impact of the deforestation of the lower part of the basin on the release of mercury. The Hg burden in the disturbed area was 7560 μg m⁻² for the 0–10 cm surface layer.     

Application de la spectrometrie d'absorption atomique zeeman aux dosages de huit elements traces (Ag, Cd, Cr, Cu, Mn, Ni, Pb et Se) dans des matrices biologiques solides

The use of biological indicators in studies of aquatic pollution (in fresh, estuarine or sea waters), as well as research about the metal transfers in food chains, need a great accuracy of the trace element determination. Therefore, as shown by the results of international intercalibration exercises, the mastery of analytical techniques is far from being perfect in all the laboratories.One of the main sources of error in atomic absorption results from non-specific absorptions due to the presence of important organic and mineral matrixes in biological materials and especially in aquatic and marine organisms. In this case, the correction of unspecific absorption by using deuterium lamp was insufficient and the determination of trace elements had to be preceded by a pre-instrumental stage which allowed the elimination of the organic matter by mineralization and of a large part of the mineral matrix by extraction. The previous separation was long and induced contamination risks. The use of the Zeeman effect background correction allows the transfer of most processes from the pre-instrumental to the instrumental stage. Moreover, the Zeeman effect has three advantages: (1) the background correction is effective up to 2 units of absorbance; (2) the correction is effective from 190 to 900 nm; (3) the method of the double beam is optimalized.The aim of this study was to apply the Zeeman effect to the determination of eight trace elements (Ag, Cd, Cr, Cu, Mn, Ni, Pb, Se) in three different biological solid samples, two originated from the marine environment (lobster hepatopancreas TORT-1, standard reference material from the National Research Council Canada; oyster tissues SRM 1566 from the US National Bureau of Standards) and one from the vegetable kingdom (tomato leaves, SRM 1573 from the US NBS).The experimental procedure is reduced to a minimum since it consists in the digestion of an aliquot of 100 mg of the powdered sample with 1 ml of concentrated nitric acid at 95°C for 1 h. Then the volume is adjusted to 4 ml with deionized water. The metal analysis is carried out using a graphite furnace coated with tantalum carbide.This analysis is achieved according to the method of standard addition. The three added concentrations used for each element are listed in Table 1. The analytical conditions and graphite atomizer program are indicated in Table 2. The temperature program has to be modified according to the type of equipment.The internal quality control of the suggested method related to four criteria: sensitivity, repeatability, accuracy, practicability. The results are shown in Table 3. The threshold of sensitivity (3 times the SD of a series of eight results obtained for a blank of digestion) are low: < 1 μg kg⁻¹ for Ag, Cd and Mn; 1 μg kg⁻¹ for Cr and Pb; 5 μg kg⁻¹ for Cu and Ni and 15 μg kg⁻¹ for Se. The variation coefficients, calculated for both two series of six determinations each, are generally included between 5 and 10%. The trace element concentrations determined by using this method are in perfect agreement with the certified values of the US NBS and NRC Canada (Table 3.)The quality of the results establishes the possibility of using a very easy and fast method to determine the level of eight trace elements in materials with high mineral and organic matter content.     

Environmental chemistry of copper in Lake Monona, Wisconsin

Lake Monona, located at Madison, Wisconsin, received over 1.5 × 10⁶ pounds of copper sulfate in the past 50 yr to control excessive algal growth. Dissolved copper on Lake Monona epilimnion is inversely related to pH which indicates possible control of dissolved copper by basic copper carbonate. Concentrations as high as about 4 μg Cu l⁻¹ were found in Lake Monona epilimnion, which also contains 3.3 me l⁻¹ (milliequivalents per liter) of alkalinity, mostly bicarbonate. Concentrations of dissolved copper were consistently lower (0.3 μg Cu l⁻¹) in the hypolimnion. Sulfide probably controls dissolved copper in the hypolimnion during anoxic conditions because of sulfide insolubility. Particulate copper concentrations of about 3 μg l⁻¹ increased slightly with depth. The highest concentrations of copper in Lake Monona sediments (650 mg kg⁻¹) were found approximately 60 cm below the current sediment surface. Surface sediments of Lake Monona contained approximately 250 mg Cu kg⁻¹ sediment dry weight.     

Total metal concentrations and partitioning of Cd, Cr, Cu, Fe, Ni and Zn in sewage sludge

Application of the BCR three-step sequential extraction procedure to sewage sludge samples collected at an urban wastewater treatment plant (Dom ale, Slovenia) is reported. The total concentrations of Cd, Cr, Cu, Fe, Ni and Zn and their concentrations in fractions after extraction were determined by flame or electrothermal atomic absorption spectrometry (FAAS, ETAAS) under optimised measurement conditions. Total acid digestion including hydrofluoric acid (HF) treatment and aqua regia extraction were compared in order to estimate the efficiency of aqua regia extraction for determination of total metal concentrations in sewage sludge. It was found experimentally that aqua regia quantitatively leached these heavy metals from the sewage sludge and could therefore be applied in analysis of total heavy metal concentrations. The total concentrations of 856 mg kg⁻¹ Cr, 621 mg kg⁻¹ Ni and 2032 mg kg⁻¹ Zn were higher than those set by Slovenian legislation for sludge to be used in agriculture. Total concentrations of 2.78 mg kg⁻¹ Cd, 433 mg kg⁻¹ Cu and 126 mg kg⁻¹ Pb were below those permitted in the relevant legislation. CRM 146R reference material was used to follow the quality of the analytical process. The results of the BCR three-step sequential extraction procedure indicate high Ni and Zn mobility in the sludge analysed. The other heavy metals were primarily in sparingly soluble fractions and hence poorly mobile. Due to the high total Ni concentration and its high mobility the investigated sewage sludge could not be used in agriculture.     

Aspects of the aquatic chemistry of cadmium and zinc in a heavy metal contaminated lake

Concentrations of the heavy metals cadmium (Cd) and zinc (Zn) were determined at several sites in Palestine Lake, Indiana, and in the stream (Williamson Ditch) which transports metal-bearing wastes to the lake. Average dissolved Cd and Zn concentrations in the lake were as high as 17.3 μg 1^-1 and 293 μg 1^-1, respectively, while corresponding suspended levels were 30.3 μg Cd 1^-1 and 270 μg Zn 1^-1. Average levels of both Cd and Zn in the dissolved fraction exceeded those in the suspended fraction, except at one site in the lake where suspended Cd was higher. During anaerobic conditions occurring in lake's hypolimnion, a marked decrease in the dissolved fraction and concomitant increase in the suspended fraction of both Cd and Zn were noted. A cadmium-specific ion electrode was used to determine the chemical forms of dissolved Cd present in the lake. Free Cd²⁺ was the dominant form; however, Cd-organic complexes sometimes comprised a significant portion of the total dissolved Cd.     

Cardiovascular-respiratory responses of rainbow trout (Salmo gairdneri) during chronic exposure to sublethal concentrations of cadmium

The effects of exposure to 3.6 and 6.4 μg l⁻¹ cadmium for periods up to 178 days on cardiac and ventilatory rates, hematocrit, hemoglobin concentration and erythrocyte adenosine triphosphate concentration in adult rainbow trout, Salmo gairdneri, were investigated. Except for slight transitory responses, 3.6 μg l⁻¹ cadmium had no effect on any of the cardiovascular/respiratory parameters. Significant increases in cardiac and ventilatory rates, blood hematocrit and hemoglobin were observed in fish exposed to 6.4 μg l⁻¹ Cd over the entire exposure period while erythrocyte ATP concentration declined during the last stages of exposure. Further experiments on the responses of fish exposed to 6.4 μg l⁻¹ Cd for 30 days demonstrated an impairment of oxygen transfer across the gill. The results are discussed in terms of possible gill impairment and hyperactivity as toxic responses to cadmium.     

Acute toxicity and behavioral responses of coho salmon (Oncorhynchus kisutch) and shiner perch (Cymatogaster aggregata) to chlorine in heated sea-water

The acute toxicity and behavioral response to chlorinated and heated sea-water was determined for coho salmon smolts and 1–3 month old shiner perch. LC₅₀'s were determined for 7.5, 15, 30 and 60 min exposure times; 13, 16 and 20°C (Δt = 0, 3, 7°C) temperatures and total residual oxidant (TRO) concentrations ranging from 0.077 to 1.035 mg l⁻¹. The mean 60 min LC₅₀ for shiner perch was significantly reduced (P ≤ 0.05) from 308 μg l⁻¹ TRO at 13°C to 230 μg l⁻¹ TRO at 20°C. The 60 min LC₅₀ for coho salmon decreased from 208 μg l⁻¹ TRO at 13°C to 130 μg l⁻¹ at 20°C. The LC₅₀'s for coho salmon in chlorinated sea-water averaged 55% of those for shiner perch. The relationship between TRO concentration, exposure time, and percent survival in chlorinated sea-water at 13°C is presented for both species.A significant (P ≤ 0.01) avoidance threshold for coho salmon occurred at 2 μg l⁻¹ TRO and was reinforced with increasing temperature. A significant (P ≤ 0.01) avoidance threshold for shiner perch occurred at 175 μg l⁻¹ TRO, while a significant preference (P ≤ 0.05 or 0.01) response at 16°C and 20°C occurred at 10, 25, 50 and 100 μg l⁻¹ TRO. The ecological implications of the toxicity tests and the behavioral responses are discussed.     

Removal of heavy metals from electroplating rinsewaters by precipitation, flocculation and ultrafiltration

Chromium, nickel, copper and zinc can be effectively removed from electroplating rinsewaters by hydroxide precipitation, flocculation and ultrafiltration. Prior to precipitation, chromium is reduced from the hexavalent to the trivalent form by ferrous sulfate and cyanide in copper and zinc rinsewaters are oxidized by sodium hypochlorite. Minimum metal concentrations in the permeate from separate batches of chromium, nickel, copper and zinc rinsewaters were found to be, respectively, 0.17 mg 1⁻¹ Cr (T), 0.26 mg 1⁻¹ Ni, 0.30 mg 1⁻¹ Cu and 1.84 mg 1⁻¹ Zn. These solubilities are in good agreement with the theoretical solubility curves, except for copper where the formation of stable copper cyanide complexes appears to increase the solubilities at least two orders of magnitude relative to those predicted on the basis of the equilibrium constants for copper hydroxides and oxides. A simple mass balance model, assuming concentrate recycle and constant metal concentration in the permeate, is adequate for the prediction of feed and permeate concentrations as a function of the volume filtered up to a relative volume of about 0.3. Above this value, the feed concentrations are lower than predicted, apparently because of entrapment of metal precipitate in the strainer. Water recoveries are strongly dependent on the specific metal removed and are found to be 24% for Ni with a 0.20 μm membrane, 10% for Cr with a 0.80 μm membrane, 6.5% for Cu and 3.7% for Zn, both with a 0.45 μm membrane.