Seasonal variation of the concentrations of 137Cs in sediment,sea water,and some organisms collected from Izmir Bay and Didim

¹³⁷Cs in the marine environment mainly originates from fallout of atmospheric nuclear weapon tests, accidental releases from nuclear facilities, and from the Chernobyl accident. After the latter accident, many studies have been carried out in Turkey. The objective of this study is to assess the spatial distribution of ¹³⁷Cs in the coastal marine environment of the Aegean Sea.

The concentrations of ¹³⁷Cs in sediment, sea water, mussel (Mytilus galloprovincialis), and fish samples collected from the coast of the Aegean Sea at Izmir Bay and near Didim (Akbük) have been monitored for seasonal variability by the means of gamma spectroscopy: they vary between 0.10 ± 0.01 and 1.5 ± 0.3 Bq kg^?1, 1.3 ± 0.1 and 4.3 ± 0.4 Bq m^?3, <0.2 and 1.3 ± 0.3 Bq kg^?1, and 0.20 ± 0.03 and 1.8 ± 0.3 Bq kg^?1, respectively.     

Temperature effects on accumulation and retention of radionuclides in the sea star,Asterias forbesi: implications for contaminated northern waters

Radioactive waste disposal and nuclear testing concentrated in high latitudes in the northern hemisphere have resulted in the accumulation of radionuclides in Arctic marine ecosystems, but little is known of the consequences for marine biota in these waters. Under controlled laboratory conditions in May through September 1994, we examined the bioaccumulation in sea stars, Asterias forbesi (Desor), or the radionuclides ²⁴¹Am, ⁵⁷Co and ¹³⁷Cs, all of which are important components of disposed radioactive wastes. Experiments at 2 and 12°C determined the relative importance of food (the bivalve, Macoma balthica) and water as sources of radionuclides and assessed the influence of temperature on radionuclide influx and efflux rates. The lower temperature greatly increased the retention of radionuclides ingested with food; for instance, the biological half-life (tb _1/2) of ²⁴¹Am in the sea stars was 31 d at 12°C, but was virtually infinite at 2°C. Retention of ingested ⁵⁷Co was also increased at 2°C (tb _1/2=41 d). ¹³⁷Cs was not accumulated from food. Low temperature significantly reduced net influx rates of ¹³⁷Cs from water, but did not affect net uptake of ²⁴¹Am or ⁵⁷Co. Temperature had little effect on the retention of all three isotopes obtained from the dissolved phase. These experiments suggest that extrapolation of results of previous radioecological studies, conducted at warmer temperatures, to polar or temperate winter environments may be problematic, and that nuclear waste isotopes obtained through trophic transfer may be retained far more efficiently in high latitude marine biota than by fauna from warmer ecosystems.     

Retention of 137cesium in acid sulphate soils of South Central Thailand

Adsorption and desorption of ¹³⁷Cs by acid sulphate soils from the Nakhon Nayok province, South Central Plain of Thailand located near the Ongkarak Nuclear Research Center (ONRC) were investigated using a batch equilibration technique. The influence of added limestone (12 and 18 tons ha^?1) on ¹³⁷Cs adsorption–desorption was studied. Based on Freundlich isotherms, both adsorption and desorption of ¹³⁷Cs were nonlinear. A large portion (98.26–99.97%) of added ¹³⁷Cs (3.7?×?10³?7.03?×?10⁵ Bq l^?1) was sorbed by the soils with or without added lime. The higher lime treatments, however, favoured stronger adsorption of ¹³⁷Cs as compared with soil with no lime, which was supported by higher K _ads values. The addition of lime, the cation exchange capacity and pH of the soil increased and hence favoured the stronger adsorption of ¹³⁷Cs. Acid sulphate soils with a high clay content, medium to high organic matter, high CEC, and predominant clay types consisting of a mixture of illite, kaolinite, and montmorillonite were the main soil factors contributing to the high ¹³⁷Cs adsorption capacity. Competing cations such as NH₄ ⁺, K⁺, Na⁺, Ca²⁺, and Mg²⁺ had little influence on ¹³⁷Cs adsorption as compared with liming, where a significant positive correlation between K _ads and soil pH was observed. The ¹³⁷Cs adsorption–desorption characteristics of the acid sulphate soils studied exhibited a very strong irreversible sorption pattern. Only a small portion (0.09–0.58%) of ¹³⁷Cs adsorbed at the highest added initial ¹³⁷Cs concentration was desorbed by four successive soil extractions. Results clearly demonstrated that Nakhon Nayok province acid sulphate soils have a high ¹³⁷Cs adsorption capacity, which limits the ¹³⁷Cs bioavailability.     

Sediment environmental capacity of 137Cs in Daya Bay

Sediment environmental capacity of pollutants is very important for marine environmental management. Based on the methodology of a study on water, soil environmental capacity, and mass conservation theory in a system, the concept and model on sediment environmental capacity for ¹³⁷Cs in Daya Bay were developed. The static capacity for ¹³⁷Cs in the upper sediment near the shore at a shallow area was calculated, and the annual dynamic capacity and total dynamic capacity were also calculated through determination of the typical biomass in the sediment. The results showed that the estimated environmental capacity for ¹³⁷Cs in sediments was approximately equal to the current input of ¹³⁷Cs into the sediments. Controlling the input of ¹³⁷Cs in the sediments within the environmental capacity guarantees the sustainability of the current situation of the Daya Bay ecosystem and avoidance of a significant degradation of the system.     

Etude de la décontamination d'Arenicola marina (annélide,polychète) après contamination expérimentale par le caesium 137 ou le cobalt 60

From a nuclear protection standpoint, problems of decontamination are of great interest. In Arenicola marina L. a comparative study has been made on the elimination of two radionuclides, the metabolic functions of which are very different: ¹³⁷Cs and ⁶⁰Co. After experimental contamination with ¹³⁷Cs, significant decontamination is possible; however, elimination of ¹³⁷Cs accumulated in muscles is very slow. The elimination of ⁶⁰Co is very slow; its biological half-life in A. marina is about 3 months.     

Uptake and depuration of cesium in the green mussel Perna viridis

 The accumulation and depuration of Cs in the green mussels (Perna viridis) commonly found in the subtropical and tropical waters were studied under the laboratory conditions using radiotracer techniques. Following an initial rapid sorption onto the mussel's tissues, uptake of Cs exhibited linear patterns over a short exposure time (8 h) at different ambient Cs concentrations. The concentration factor was independent of ambient Cs concentration. The calculated uptake rate and initial sorption constant of Cs were directly proportional to the ambient Cs concentration. The calculated uptake rate constant from the dissolved phase in the mussels was as low as 0.026 l g⁻¹ d⁻¹. Uptake rates of Cs in the mussels were inversely related to the ambient salinity. Uptake increased about twofold when the salinity was reduced from 33 to 15 ppt. The effect of salinity on Cs uptake was primarily due to the change in ambient K⁺ concentration. The uptake rate decreased in a power function with increasing tissue dry weight of the mussels, although the initial sorption was not related to the mussel's body size. The efflux rate constant of Cs in the mussels was 0.15 to 0.18 d⁻¹, and was the highest recorded to date among different metals in marine bivalves. The efflux rate constant also decreased in a power function with increasing tissue dry weight of mussels. A simple kinetic model predicted that the bioconcentration factor of Cs in the green mussels was 145, which was higher than measurements taken in their temperate counterparts. The bioconcentration factor also decreased in a power function with increasing tissue dry weight of mussels. Received: 27 October 1999 / Accepted: 16 June 2000     

A model of radiocesium cycling in a sand hills—Turkey Oak (Quercus laevis) ecosystem

Digital simulation models of radiocesium cycling in Turkey Oaks were developed from in situ ¹³⁴Cs tagging studies. Predictions of ¹³⁴Cs steady-state distribution for 3-, 4- and 5-compartment, donor-controlled models were compared with the estimated fallout ¹³⁷Cs distribution as a measure of model validation; output from the 5-compartment model compared best. Sensitivity analysis demonstrated that Turkey Oak burden of ¹³⁴Cs was equally sensitive to the output rate from the tree compartment and the availability of ¹³⁴Cs for uptake (i.e., presence in the root zone) but not the rate of uptake by Turkey Oaks. Observed distribution and model predictions indicate that radiocesium is readily bioaccumulated by Turkey Oaks (～13% of the ecosystem burden) from the soil and is cycled within the sand hills—Turkey Oak ecosystem.     

A study on the elimination of 137Cs in mussels under contaminated fields and laboratory conditions

The natural depuration or bioelimination of ^l37Cs was investigated in Mytilus galloprovincialis under contaminated field and laboratory conditions. The depuration result represented by a single component and biological half‐life was found to be 63 days under Chernobyl condition during 1986–1987. On the other hand, the biological half‐life of ¹³⁷Cs were found in the range 19.7–27.1 days in the laboratory experiment. The bioelimination process was also found biphasic and dependent of temperature at 5°C and 13°C under laboratory conditions. The results obtained in the contaminated field and the laboratory are not comparable in the mussels.     

Cäsium-137 in Böden saarländischer Waldökosysteme

Scopes and main features

In order to explain the behaviour of the artificial radioisotope¹³⁷Cs towards landscape resources in the Saar-Lor-Lux-Region, the cross-border region between southwestern Germany/ Saarland, France/Lorraine and Luxembourg, regional distribution as well as downward translocation and depth functions of¹³⁷Cs in the main soil substrates of forest ecosystems in the Saarland were investigated.

Results

The study shows that the highest¹³⁷Cs activities are found in the north of the Saarland, whereas the south and south-eastern regions show distinctly lower concentrations of¹³⁷Cs. Migration rates range between 0.25 cm/a and 1.0 cm/a. On an average, the highest migration rates were found in the clayey-silty substrates of the lime stone areas in theMuschelkalk regions (Middle Triassic) (0.66 cm/a), followed by the loamy substrates of Lower Permian clastic sediments (Unterrotliegendes) (0.53 cm/a) and the sandy substrates of theBuntsandstein areas (Lower Triassic sandstone) (0.41 cm/a). 90 to 95% of the¹³⁷Cs activities in the clay-poor soils of the Unterrotliegendes and the Buntsandstein were traced in the upper 10 cm of the humus topsoil. The substrates of the lime stone areas (Muschelkalk), in contrast to this, reveal a¹³⁷Cs activity of only 70–76% at the same depth.

Conclusions

Due to the fact that the primary and secondary pores of the soil pore system, in their function as translocation pathways, decrease with increasing soil depth, a significant reduction in the migration rates of¹³⁷Cs can be expected with increasing soil depth. On the other hand, the maximal migration depth of 40 cm found in shallow soils on jointed parent material, as well as on sites with high groundwater tables, implies a possible contamination of near-surface groundwater.

Future outlook

Based on the results of this study, a permanent monitoring of¹³⁷Cs was added to the long-term Soil Monitoring Program run by the Federal Administrative Office of Environment of the Saarland (Landesamt für Umweltschutz des Saarlandes)     

Determination of natural and artificial radionuclide materials in the Ma’assel used in hubbly-bubbly (Shisha) in Jordan

In the last decade the habit of smoking the hubbly-bubbly has increased sharply in many regions, including Europe, North America and Australia. Jordan is considered as having one of the highest consumptions of hubbly-bubbly in the world with respect to the general population. Our investigation was initiated due to the increasing trend of cancer cases in the last 10 years. The aim of this study was to determine the radioactive content in tobacco products available in the Jordanian market together with the related supplies. This study showed that all 13 samples investigated contained one or more radionuclides, from ²¹⁰Pb, ⁴⁰K, ¹³⁷Cs, ²³⁸U, and ²²⁶Ra. Most of the samples contained natural potassium ⁴⁰K and uranium ²³⁸U, lead ²¹⁰Pb was found in three samples, while radium ²²⁶Ra was present only in one sample. Five samples contained the anthropogenic ¹³⁷Cs. The estimated daily intake of U was found in the range between 4.4 and 115.8?µg per day (0.05–1.43 Becquerel (Bq) per day ²³⁸U), with geometric mean of 17.3?µg per day (0.2?Bq per day ²³⁸U). The geometric mean of U daily intake found represents 25% of the reference dose (RfD) value, where the highest determined U content represents 165% of the RfD value. This study demonstrated that a water vessel of hubbly-bubbly trapped less than 1.5% of the total U in Ma’assel samples. It is misleading to the public to indicate that a water vessel serves as an active filter for toxic and radiotoxic elements.     

Experimental study on vanadium transfer in the benthic fish Gobius minutus

The radiotracer vanadium-48 was used to examine accumulation, assimilation, tissue distribution and elimination of vanadium in the benthic fish Gobius minutus (Pallas). After 3 wk exposure to ⁴⁸V in sea water, mean whole-body concentration factors were low (0.8). The tissue distribution of ⁴⁸V indicated that ⁴⁸V accumulated from water penetrates little into internal tissues, muscle or liver, and is preferentially fixed in tissues in direct contact with the sea water. Concentrations of stable vanadium in fishes collected during summer 1988 from the littoral zone near Monaco displayed the same trends. Vanadium accumulated directly from water is rapidly lost, as evidenced by a 19 d biological half-life of ⁴⁸V. Likewise, assimilation of vanadium through the food-chain is low; only 2 to 3% of ⁴⁸V ingested with prey is retained in the tissues of the goby. The results suggest that the relatively low vanadium toxicity observed in benthic fish by other investigators is a consequence of the low degree of uptake of this metal from food or water. The relative importance of uptake from food and from water to the vanadium levels in benthic fish is discussed in the light of the ⁴⁸V distribution recorded in experimental individuals and the distribution of stable vanadium in similar samples from the natural environment.     

Deltamethrin-induced alterations in serum calcium and prolactin cells of a freshwater teleost,Heteropneustes fossilis

Deltamethrin, a pyrethroid insecticide widely used in many countries, causes significant adverse effects in aquatic ecosystems. The concentration of deltamethrin in water reservoirs and the run off from agricultural areas (in water) in many countries range up to 24.0?µg?L^?1 which is higher than the recommendation of the European Union standard. Hence, in this study the effects of deltamethrin were investigated, i.e. its toxic impacts on the freshwater catfish Heteropneustes fossilis in terms of serum calcium and prolactin cells (located in the rostral pars distalis region of the pituitary). The fish were subjected to deltamethrin for a short-term experiment (96?h; 1.5?µg?L^?1 e.0.8 of 96?h LC₅₀) and a long-term experiment (28 days; 0.37?µg?L^?1 e.0.2 of 96?h LC₅₀). After short-term deltamethrin exposure, serum calcium levels decrease. No histological change in prolactin cells is noticed throughout the short-term experiment. Fish exposed to deltamethrin for 7 days also exhibit a decrease in serum calcium level. This decrease persisted until the end of the experiment (28 days). Prolactin cells of fish treated for 14 days with deltamethrin exhibit increased nuclear volume and degranulation, increasing progressively from the 21st day onwards. After 28 days, a few degenerated cells are discerned. The results of this study show that deltamethrin is moderately toxic for the freshwater fish H. fossilis by producing adverse effects on serum calcium and prolactin cells. Hence, it should be used with caution in areas near fish-inhabited waters.     

Lindane toxicity range-finding test in Senegal sole (Solea senegalensis) juvenile: note on histopathological alterations

The purpose of this study was to examine the sublethal and/or lethal effects produced by exposure of teleostean fish Solea senegalensis to γ isomer of lindane, γ-hexachlorocyclohexane (γ-HCH). S. senegalensis was exposed to 0.1, 1 or 10 mg L^?1 of lindane for 96 h. Samples of different tissues (gills, liver and kidney) were extracted and processed for histopathological observations. The 72 h LC₅₀ value of pesticide was found to be 0.16 ± 0.04 mg L^?1 γ-HCH. Histological observations including aneurysms and hypertrophy of lamellar epithelia in gills, blood stagnation and vacuolization in liver and alterations in the hematopoietic tissue in kidney were observed. The results of the study show the sensitivity of juvenile of S. senegalensis to lindane and histology as a reliable tool to detect the sublethal effects of pollutants on the environment and aquatic biota. The toxicological implications arising from these results are the subject for further multi-concentration tests useful in establishing water quality criteria.     

Sediment accumulation and bio-diffusion mixing rates derived from excess <Superscript>210</Superscript>Pb and <Superscript>137</Superscript>Cs profiles in sediment cores of Mumbai Harbor Bay

Bio-diffusion mixing rates (D_b) were estimated from depth profiles of excess ²¹⁰Pb and ¹³⁷Cs in three sediment cores collected from Mumbai Harbour Bay (MHB) using a steady state vertical advection - diffusion model. The mean of ²¹⁰Pb and ¹³⁷Cs derived D_b values along the studied area were obtained to be about 23 and 36 cm²y^?1 respectively. These derived values were within the range of literature values reported for other equivalent environment internationally. The relatively higher D_b values for ¹³⁷Cs profiles demonstrated that particles have diffused more intensely within the surface layer of sediments over 1 year. Conversely, low D_b values for ²¹⁰Pb indicate slow mixing rates in the sediment profile which might be resulted from low ²¹⁰Pb flux and diffusion of ²²²Rn to the seafloor. The significant differences between ²¹⁰Pb and ¹³⁷Cs derived D_b values among cores indicate that there appeared to be as regional differences in sediment properties and local variability in the intensity of seafloor mixing. Furthermore, D_b values also depend on differences in characteristic time and depth scales of radionuclides in cores, benthic fauna abundances, organic carbon flux to the sediments and primary production in overlying surface waters. Comparison of ²¹⁰Pb derived D_b values with those calculated from ¹³⁷Cs distributions reveals better agreement for core 2 than core 1 and 3. The agreement may be fortuitous because ¹³⁷Cs appears significantly deeper than ²¹⁰Pb in all cores. It was also observed that D_b values increases as sediment accumulation rate increases for both radionuclide.     

High immobilization of soil cesium using ball milling with nano-metallic Ca/CaO/NaH2PO4: implications for the remediation of radioactive soils

This report shows that cesium can be immobilized in soils with an efficiency of 96.4% by ball milling with nano-metallic Ca/PO₄. In Japan, the major concern on ¹³⁷Cs deposition and soil contamination due to the emission from the Fukushima Daiichi nuclear power plant showed up after a massive quake on March 11, 2011. The accident rated 7, the highest possible on the international nuclear event scale, released 160 petabecquerels (PBq) of iodine ¹³¹I and 15 PBq of ¹³⁷Cs according to the Japanese Nuclear and Industrial Safety Agency. Both ¹³⁷Cs and ¹³¹I radioactive nuclides are increasing cancer risk. Nonetheless, ¹³⁷Cs, with a half-life of about 30 years compared with 8 days for ¹³¹I, is a major threat for agriculture and stock farming and, in turn, human life for decades. Therefore, in Japan, the ¹³⁷Cs fixation and immobilization in contaminated soil is the most important problem, which should be solved by suitable technologies. Ball milling treatment is a promising treatment for the remediation of cesium-contaminated soil in dry conditions. Here, we studied the effect, factors and mechanisms of soil Cs immobilization by ball milling with the addition of nano-metallic Ca/CaO/NaH₂PO₄, termed “nano-metallic Ca/PO₄.” We used scanning electron microscopy combined with electron dispersive spectroscopy (SEM/EDS) and X-ray diffraction. Results show that immobilization efficiency increases from 56.4% in the absence of treatment to 89.9, 91.5, and 97.7 when the soil is ball-milled for 30, 60 and 120 min, respectively. The addition of nano-metallic Ca/PO₄ increased the immobilization efficiency to about 96.4% and decreased the ball milling time. SEM/EDS analysis allows us to observe that the amount of Cs decreased on soil particle surface. Use of nano-metallic Ca/PO₄ over a short milling time also decreases Cs leaching. Therefore, ball milling with nano-metallic Ca/PO₄ treatment may be potentially applicable for the remediation of radioactive Cs-contaminated soil in dry conditions.     

Release,deposition and elimination of radiocesium (137Cs) in the terrestrial environment

Radionuclide contamination in terrestrial ecosystems has reached a dangerous level. The major artificial radionuclide present in the environment is ¹³⁷Cs, which is released as a result of weapon production related to atomic projects, accidental explosions of nuclear power plants and other sources, such as reactors, evaporation ponds, liquid storage tanks, and burial grounds. The release of potentially hazardous radionuclides (radiocesium) in recent years has provided the opportunity to conduct multidisciplinary studies on their fate and transport. Radiocesium’s high fission yield and ease of detection made it a prime candidate for early radio-ecological investigations. The facility setting provides a diverse background for the improved understanding of various factors that contribute toward the fate and transfer of radionuclides in the terrestrial ecosystem. In this review, we summarize the significant environmental radiocesium transfer factors to determine the damaging effects of radiocesium on terrestrial ecosystem. It has been found that ¹³⁷Cs can trace the transport of other radionuclides that have a high affinity for binding to soil particles (silts and clays). Possible remedial methods are also discussed for contaminated terrestrial systems. This review will serve as a guideline for future studies of the fate and transport of ¹³⁷Cs in terrestrial environments in the wake of the Fukushima Nuclear Power Plant disaster in 2011.     

Geochemical Associations of Sellafield-Derived Radionuclides in Saltmarsh Deposits of the Solway Firth

This paper describes a study of the geochemical associations of Sellafield waste radionuclides in saltmarsh sediments from south-west s]Scotland. The contaminant radionuclides are transported to this environment in association with particulate material and ¹³⁷Cs was found to be predominantly (80-98%) non-extractable. In the case of ^239+240Pu there was a redistribution from the oxalate extractable oxide fraction to the pyrophosphate extractable organic fraction as a consequence of on-shore transfer of contaminated sediment. The relatively aggressive nature of the chemical extractants required to remove the radionuclides from the sediments suggests that they were in a form which was unlikely to result in their being released into the aquatic environment or taken up by plants. Plutonium had a greater potential mobility or bioavailability than Cs. Values of K^D for the desorption of ¹³⁷Cs from the sediment by freshwater, groundwater and seawater were all approximately 10⁵ L kg^-1, confirming its immobility in this environment. The desorption K_D values for stable ¹³³Cs were all approximately 10⁶ L kg^-1, so the stable Cs did not have a significant influence on the radiocaesium in this sediment.     

Experimental studies on elimination of zinc-65, cesium-137 and cerium-144 by euphausiids

The elimination of 3 radionuclides from Euphausia pacifica was measured over a 5 month period. The biological half-lives for ⁶⁵Zn, ¹³⁷Cs, and ¹⁴⁴Ce, calculated after the euphausiids had ingested radioactive Artemia nauplii, were found to be 140 days, 6 days, and 7.5 h, respectively. The percentages of body burdens lost in molts were greatest for the fission products, ¹⁴⁴Ce (21%) and ¹³⁷Cs (7%), and least for ⁶⁵Zn (1%). Elimination of the isotopes in the feces could not be followed because of the difficulty in collecting fecal material for analysis; however, 1 sample collected 2 months after the beginning of the elimination experiment had no measurable radioactivity. Loss of ⁶⁵Zn from molts and time to disintegration of the molts were found to be temperature dependent over a 5° to 15°C range, and the sinking rate of molts was both temperature and salinity dependent. Calculations showed that, in areas in the North Pacific outside the influence of upwelling, percentage ⁶⁵Zn loss from sinking molts (before disintegration of the molts) was likely to be the same throughout the year, since the molts would be exposed to about the same mean temperature in the water column in all seasons. Even though temperature structure in the upper layers changes with season, mean temperatures change very little when calculated over the sinking distance of intact molts. Intact molts would sink to slightly over 400 m in the absence of turbulence, and would lose 87% of their ⁶⁵Zn by the time they reached this depth. Sinking molts thus might contribute substantially to the vertical transport of ⁶⁵Zn in the sea. If loss of ⁶⁵Zn in fecal pellets is assumed to be small under our experimental conditions, and molting loss is only 1% of ⁶⁵Zn body burden, the major mechanism of ⁶⁵Zn loss from euphausiids feeding on non-radioactive food must be isotopic exchange with the water. Approximately 96% of the initial body burden was eliminated over a period of 5 months.Supported by USAEC research contract AT (45-1)1830, PHS grant ES00026, and a Richland Graduate Fellowship to S. W. Fowler.     

Reduced hypoosmoregulatory ability and alteration in gill chloride cell distribution in mature chum salmon (Oncorhynchus keta) migrating upstream for spawning

Osmoregulatory ability of mature chum salmon (Oncorhynchus keta) during spawning migration was examined by following the changes in gill Na⁺, K⁺-ATPase activity and in the distribution and morphology of chloride cells. Mature chum salmon caught in Otsuchi Bay, northern Honshu Island, Japan, died within 5 d in seawater (SW) in association with a marked increase in plasma osmolality, whereas the fish transferred to fresh water (FW) maintained plasma osmolality efficiently. Gill Na⁺, K⁺-ATPase activity decreased in both SW-maintained and FW-transferred fish. Well-developed chloride cells, identified by immunocytochemical staining specific for Na⁺, K⁺-ATPase, were present mainly in the filament epithelium of immature fish caught in the ocean. In mature fish caught in the bay, however, additional chloride cells were also found in the lamellar epithelium. The number of filament chloride cells decreased markedly in the mature fish both in SW and in FW, whereas the number of lamellar chloride cells was maintained. These results suggest that the loss of hypoosmoregulatory ability in mature chum salmon may be attributable to the decrease in filament chloride cells and associated decrease in gill Na⁺, K⁺-ATPase activity, and also that appearance of lamellar chloride cells may be preparatory to the forthcoming upstream migration. Received: 14 April 1997 / Accepted: 5 May 1997     

Histopathological impact of industrial wastewater on the vital organs of Oreochromis mossambicus

The acute toxicity of paper mill wastewater to Oreochromis mossambicus was investigated with the lethal concentration (LC50) value 6.5% for 96?h exposure. This concentration was used as a baseline to study the effects of paper mill effluent on histopathological changes in gills, liver, kidney, and brain of fish. In the gills, filament cell proliferation, cellular infiltration, hemorrhage, and epithelial lifting were observed. In the liver, vacuolation of hepatocytes and necrosis were noted. In kidney, exfoliation and swollen with pyknotic nuclei were identified. Similarly, the brain also showed enlarged pyramidal cells, binucleated nuclei, vacoulation, and necrosis. These changes occurred predominantly in 21days following exposure of fish to the industrial waste water. Paper mill wastewater was found to be highly toxic to fish.