Unpolluted River Research Articles

Heavy metals in sediments from the Paraguay River: a preliminary study

The first results ever obtained on heavy metal concentrations (Fe, Mn, Cr, Cu, Zn and Pb) in the Paraguay River surface sediments are presented. Samples collected at 11 locations, along a distance of 570 km, between the cities of Bahia Negra and Alberdi in Paraguay, for six different periods between November 1991 and 1993, were analyzed. The Paraguay sediments appeared to have features of an unpolluted river even though significant amounts of domestic and industrial effluents are discharged near the river channel. The relative heavy metal enrichment in sediments between Bella Vista and Asunción, caused by local domestic sewage and industrial outfalls, is less than for the shale standard values. The heavy metal content of the sediments exhibited seasonal variations. Enhanced organic matter content and biochemical oxygen demand of the river load in winter caused most likely a retainment of the heavy metals in a dissolved state. Consequently, the sediments deposited in the winter were relatively depleted in these elements.

Benthic macroalgae of an unpolluted tropical river (Rio Savegre, Costa Rica)

A survey of the benthic macroalgae and physical data was monthly performed in Rio Savegre from its headwaters to its lowplain course. The macroalgae were observed with a viewing box at 20 cm intervals following a fixed rope across the stream and microscopical observations were made at laboratory. The species composition of benthic macroalgae found in Rio Savegre is characteristic for unpolluted. clear. carbonate poor streams. From the source to the mouth a change from species adapted to cold. fast flowing streams to species adjusted to higher temperatures. lower current velocity and periodic desiccation was observed. There was a replacement of the multilayered. well structured macroalgal community in the upper part of the river by surface films formed by microalgae in the lower part. In addition a high-light community consisting of Spirogyro sp., Nostoc verrucosum and Tetraspora sp. could be distinguished from the dim-light species Prosiola mexicana and Hildenbrandia sp.

Ecological role of thiosulfate and sulfide utilizing purple nonsulfur bacteria of a riverine ecosystem

The screening of purple nonsulfur bacteria (PNSB) from the polluted and unpolluted zones of the river Ganga and from the discharged effluents (pollutants), revealed that the population densities of PNSB were highest in the discharged pollutants followed by polluted and unpolluted river waters in decreasing order. The allochthonous input of PNSB affected the ambient PNSB population. In all the monitored sites, the PNSB population utilizing malate as electron donor was higher than those utilizing thiosulfate or sulfide or both as electron donors. The physico-chemical parameters of the river water related to the distribution of PNSB were recorded. Twenty-four isolates of PNSB utilizing sulfide and thiosulfate, assigned to Rhodopseudomonas palustris including a morphophysiological variant of the species, Rhodobacter capsulatus and Rhodocyclus gelatinosus (= Rubrivivax gelatinosus), were screened from river Ganga. The surviving ability of PNSB population under simulated condition differed amongst the monitored sites. The isolated strains of PNSB were able to convert thiosulfate to sulfate or to elemental sulfur and also were able to oxidize sulfide. However, there was heterogeneity with respect to the rates at which they transformed these sulfur compounds. The overall thiosulfate transformation rate by the PNSB isolates in the river water was 117.3 μmol d −1 mg −1 and that of sulfide transformation was in the order of 0.15 μmol d −1 mg −1. The ecological significance of sulfide utilization in the aquatic bodies by the isolates of PNSB is discussed.

Inhibitors of the multixenobiotic resistance mechanism in natural waters: In vivo demonstration of their effects

AbstractXenobiotics in water that can inhibit the multixenobiotic resistance (MXR) defense mechanism in water organisms, the chemosensitizers, may cause severe ecotoxicological effects. We determined their concentrations in polluted and unpolluted river waters and seawaters using different methods. Here we present the method that enables direct determination of MXR‐inhibitory potential in natural waters. This method measures the modulating potential of river water or seawater on the rate of rhodamine B (RB) accumulation in gills of a freshwater clam (Dreissena polymorpha) or a marine mussel (Mytilus galloprovincialis), respectively. The sensitivity of the method with RB even enabled the determination of MXR inhibitors by measuring their potential to modulate the rate of efflux of RB from gills of mussels. The concentrations of MXR inhibitors found by these methods (expressed in μM of verapamil‐equivalents) were higher in natural waters from polluted rivers or in natural seawaters from polluted marine sites than in natural waters from unpolluted rivers or in natural seawaters from unpolluted sites. Polluted waters enhanced accumulation or decreased efflux rate of RB, a good substrate of P‐glycoprotein, demonstrating that the complex mixture of chemicals present in polluted waters contains MXR‐inhibiting potential. In addition, the efflux version of the method with RB has the clear advantage of not requiring that organisms be killed and so allows repeated use of the same individuals. In addition, it is the simplest and the most reliable method for measuring the activity of MXR in these organisms.

Flow cytometric analysis of bacterial respiratory and enzymatic activity in the natural aquatic environment

The respiratory and enzymatic activity of bacteria in polluted and unpolluted river water was investigated by flow cytometry. Double staining with 6CFDA (6-carboxy fluorescein diacetate) and PI (propidium iodide) was used to examine bacterial esterase activity. CTC (5-cyano-2,3-ditolyl tetrazolium chloride) was employed as the indicator of bacterial respiration. The ratios of colony-forming units to total bacterial number were less than 2%, except highly polluted sites. The number of respiring bacteria determined by flow cytometry amounted to 10-15% of the total bacterial number at both unpolluted and polluted sampling stations, while it was 30% at the highly polluted station. Almost 50% of total bacteria demonstrated esterase activity in the unpolluted areas, whereas 70-90% of total bacteria retained this enzymatic activity in the polluted areas. Thus, many of the non-culturable bacteria in the natural aquatic environment have enzymatic activity regardless of the pollution level, and 6CFDA was more superior in the sensitivity for the evaluation of physiological activity of bacteria in the natural environment. The ratio of bacteria with esterase activity increased in direct proportion to the pollution level of river water and suggested that this ratio would be a useful indicator in evaluating the pollution levels in an aquatic environment.

Levels and speciation of heavy metals in unpolluted river water

The levels of Cu, Cd, Zn and Pb and their speciation at four sampling sites located along a river course relatively untouched by industrial or urban influence were monitored voltammetrically over a one‐year period. The metal levels found were well below those legally allowed. In those cases where the overall concentrations were high enough, the speciation patterns for Pb, Cu and Zn were obtained.

An intergrated waste survey and environmental effects of COGIDO, a bleached pulp and paper mill in Vietnam, on the receiving waterbody

An integrated investigation on wastewater characterization and the environmental effects from the COGIDO pulp and paper mill in Bien Hoa Industrial Estate, Vietnam, a chlorine bleached soda integrated pulp and paper mill operating without a chemical recovery system, on the receiving water body was conducted during the rainy and dry seasons in 1993 and 1995. The pollution load from the mill was very high in terms of BOD, COD and SS (CODm: 58.7 t/d; BOD: 33.3 t/d and SS: 25.1 t/d). The effluent toxicity was determined using four toxicity tests: the green micro-alga, Selenastrum capricornutum, Microtox (marine bacteria: Photobacterium phosphoreum), the duckweed, Lemna aequinoctialis, and fish (silver barb: Puntius gonionotus, and Tilapia: Tilapia nilotica). Selenastrum capricornutum was the most sensitive among the tested organisms. The mill toxicity emission rate (TER) was as high as 338 610 (Selenastrum test). The bleaching-pulp and semi-chemical pulp plants which contributed the largest pollution load to the total COGIDO effluent, therefore, were targeted for abatement measures. Physico-chemical parameters as well as qualitative and quantitative aquatic organism composition for the river water were established. The BOD5 and COD values exceeded the potable surface water standard by a factor of 2 to 4. The species diversity and abundance of the phytoplankton, zooplankton and zoobenthos were found to be lower (20–40%) than that of unpolluted rivers in Vietnam, whereas pollution-indicator species increased up to four times during the dry season 1995.

The impact of the River Ntahangwa, the most polluted Burundian affluent of Lake Tanganyika, on the water quality of the lake

Sources of pollution at the north end of Lake Tanganyika are concentrated around Bujumbura, Burundi. The impact of River Ntahangwa on the water quality of this part of Lake Tanganyika was compared with that of an unpolluted river, the Mugere. A shallow bay, not influenced by a river, was used as a reference station. Chemical analyses were carried out at four week intervals during nearly a year. Samples were taken at different distances from the shore and at different depths. River impact was detected up to 100 m from both river mouths. Even at 50 m from the mouth of the polluted River Ntahangwa, no important decrease of dissolved oxygen was detected. Chlorophyll-a maxima were found 100 m from the Ntahangwa mouth, but this was also the case 100 m from shore in the unpolluted bay. Lake water at 60 m depth was saturated with oxygen during the dry season, as it used to be in 1956. The rivers studied descent initially within the lake due to greater sediment load and lower water temperature. Nevertheless, it appears that these rivers mix completely in the lake within 100–300 m from the river mouths. The direct effects from organic pollution of the Ntahangwa on the lake seem to be rather negligible. Appropriate anti-erosion measures should reduce massive sediment discharge into the lake.

THE EPILITHIC DIATOM FLORA OF A PRISTINE AND A POLLUTED RIVER IN COSTA RICA, CENTRAL AMERICA

Results from a study on the epilithic diatom communities of a polluted river (Rio Grande de Tarcoles basin) and an unpolluted river (Rio Savegre) in the Central and Southern part of Costa Rica are presented. In this context the taxonomy of diatoms, the most abundant group of algae found in both rivers, is discussed. Altogether 125 diatom taxa were identified in the epilithic communities of these two rivers. The most abundant species in the R. Grande de Tarcoles basin were: Navicula goeppertiana, Gomphonema parvulum, G. sp. aff. pumilum, Nitzschia palea, N. amphibia, N. inconspicua, N. clausii, N. frustulum, Navicula seminulum and N. schroeterii var. escambia. The most abundant species in the R. Savegre were: Achnanthes minutissima, Cymbella sinuata, Rhoicosphenia abbreviata, Cocconeis placentula, Gomphonema rhombicum, Nitzschia fonticola, Fragilaria pinnata and Achnanthes subhudsonis. In addition, Navicula cryptotenella, N. capitatoradiata, Fragilaria ulna and Achnanthes sp. aff. ricula were distributed u...

Micronucleus test in erythrocytes of Barbus plebejus (Teleostei, Pisces) from two natural environments: a bioassay for the in situ detection of mutagens in freshwater

Erythrocyte micronucleus frequencies in wild fish from two riverine environments and in fish reproduced and reared under controlled conditions (control group) were compared, with the aim to evaluate the suitability of the MN test for the in situ detection of mutagens in freshwaters. Fish were caught in different months in two rivers of central Italy which have different pollution levels. As indicator species, the barbel ( Barbus plebejus) was chosen because of its ecological significance. Blood samplings were performed on wild fish immediately after capture and repeated at different time intervals on the same individuals, which were maintained in controlled conditions after capture. A total of 10 000 eythrocytes per specimen were scored. No significant differences in micronucleus frequencies were observed between the control group and fish from the unpolluted river (Mignone). A significant higher frequency of micronuclei was observed in fish caught in the polluted river (Tiber), in comparison to both the controls and the Mignone river fish. No significant seasonal differences were observed. Barbels examined 50 and 100 days after capture presented a remarkable decrease in micronucleus frequency in comparison with the frequency observed in barbels at capture. The micronucleus test in fish erythrocytes was shown to be a sensitive bioassay for detecting mutagenic pollution in fresh water environments.

Estimation of Bacterial Biovolume and Biomass by Scanning Electron Microscopic Image Analysis.

A scanning electron microscopic (SEM) image analysis system was used to measure bacterial biovolume in fresh water. Halation, which is a problem encountered in epifluorescence microscopy, is avoided in SEM image analysis. The biovolume-to-carbon and nitrogen conversion factors, which are used to estimate bacterial biomass, were determined in four standard strains and five river water isolates. These factors for carbon and nitrogen were 0.34±0.06pg C/μm3 and 0.094±0.014pg N/μm3 respectively. There was no noticeable difference among bacterial species or growth phases. Bacterial size and biomass were measured in polluted and unpolluted river water. The average volume of bacterial cell was twice as high in polluted water, while the bacterial biomass was 35 times higher than in unpolluted water.

First data on trace metal level and behaviour in two major Arctic river-estuarine systems (Ob and Yenisey) and in the adjacent Kara Sea, Russia

Dissolved and colloidal trace element concentrations (Cd, Cu, Fe, Ni and Pb) were determined in the Ob and Yenisey river-estuary systems and in the adjacent Kara Sea in September 1993. The data show a natural low concentration level of ‘dissolved’ (< 0.4 μm) trace metals (Cd, Cu, Fe, Ni and Pb) in the two rivers and in the Kara Sea as compared to world unpolluted rivers and the central Arctic Ocean, suggesting that the region studied is pristine with respect to trace metals. The pathway of trace metals transported from rivers to the ocean seems to be complicated, and largely influenced by biogeochemical processes taking place in the estuarine mixing zone. Colloidal material (10 4 Daltons-0.4 μm), in addition to its significant contribution to the so-called ‘dissolved’ fraction, has been shown to play a fundamental role in determining the behaviour of both conservative and non-conservative trace metals during estuarine mixing. Hence, colloids may control to a large extent the fate of ‘dissolved’ trace metals as well as their net input from the rivers to the Kara Sea.

Environmental impact of former gold mining on the Orangi river, Serengeti N.P., Tanzania

The Orangi river is an important all-year source of water for wildlife in the northern part of the Serengeti National Park. At two points along the river in the Banagi area, tributaries draining the adit and tailings of the Kilimafeza mine impact the Orangi. The former Au-Cu mine is subject to occasional wet season flooding leading to the release of iron ochres from the adit and physical as well as chemical mobilization of tailings material. The unpolluted river chemistry is essentially Na-Ca-HCO 3 − and well-buffered. Drainage water; from the tailings are characterized by low pH (2.3) and high concentration of sulphate (up to 3280 mg/l), aluminium (275 mg/l), arsenic (324 mg/l), copper (125 mg/l), iron (622 mg/l), lead (21 mg/l), manganese (65 mg/l), and zinc (126 mg/l). Adit-drainage waters are typically of a lower pH (4.6) and have a lower concentration of sulphate (up to 1840 mg/l) and metals (up to 25 mg/l Al, 92 mg/l As, 42 mg/l Cu, 258 mg/l Fe, 9.6 mg/l Pb, 53 mg/l Mn, and 102 mg/l Zn). Mixing of these acidic waters with the alkaline river leads to rapid metal precipitation as Fe-ochre coatings on clastic sediment. This effect is more noticeable in the dry season. Consequently, although the tributaries draining the two sources are heavily contaminated, the effective buffering of the mine drainage waters restricts any potential pollution to within 1 km of the mine workings. Faecal coliforms show an antipathetic relationship to low pH and high metal conditions. The only mobile metals in the water outside this area are Mn and Zn and their contamination can be biologically monitored using a protozoan-based bioassay.

Occurrence of nickel in the Canadian environment

Nickel is present in Canadian freshwater and terrestrial environments because of human activities including mining, smelting, refining, alloy processing, scrap metal reprocessing, other metal operations, fuel combustion, and waste incineration. Nickel can also enter the environment as a result of the natural weathering and leaching of rocks. Entry to the Canadian environment from anthropogenic activities results in measurable concentrations of nickel in various media to which organisms may be exposed. Although current anthropogenic rates of emission per tonne of nickel produced are less than 20 years ago, large quantities are still being emitted to the Canadian environment. Nickel is persistent in terrestrial and aquatic environments. While a large data base is available on concentrations of nickel in freshwater, sediment, soil, and terrestrial plants in Canada, relatively few data on concentrations in aquatic and terrestrial organisms are available. From data collected from 1981 to 1992, most unpolluted rivers and lakes in Canada contained between 0.1 and 10 μg nickel/L with the exception of the naturally elevated site of Smoking Hills, N.W.T. (which is at least three orders of magnitude greater), while industrial sites generally contained between 50 and 2000 μg nickel/L. Nickel levels in sediment collected from 1983 to 1992 from polluted sites such as the Welland River, some Sudbury lakes, and Hamilton and Toronto Harbours ranged between 20 and 5000 μg/g dry weight, while natural or background levels in the Niagara River, Lake Erie, Lake Superior, and Lake Huron were a full two orders of magnitude lower. With respect to drinking water sampled from 1984 to 1991, the trend has been a slight decrease in nickel levels with time but with a greater range emerging, which could be due to more sensitive detection equipment installed in 1986 (minima dropped from 1.0 μg/L to an order of magnitude lower). From data collected from 1984 to 1991, the more urbanization and industrialization associated with the city, the higher the means and medians of nickel levels in air. For example, Halifax, Montréal, Quebec, Windsor, Hamilton, and Toronto had greater air nickel levels than Ottawa, Winnipeg, and Edmonton. This trend was also confirmed with the subgroup of data collected from 1987 to 1990. Sudbury was by far the site with the greatest nickel concentrations (average 124 ng/m3). Furthermore, nickel accumulation in wildlife varied with species. For example, mice seemed to accumulate more nickel in their organs than did rats and other larger rodents, while beavers and minks, on average, accumulated more nickel in their livers than did birds in similar sites near Sudbury. Similar trends have been found in Canadian soil pore water, flora, and soil.Key words: nickel compounds, occurrence, Canadian environment.

清浄河川（高見川）と汚濁河川（佐保川）における付着珪藻群集と有機汚濁指数ＤＡＩｐｏの季節変化

清浄河川（高見川）と汚濁河川（佐保川）における付着珪藻群集と有機汚濁指数ＤＡＩｐｏの季節変化

Evaluation of biodegradation kinetics of organic wastewater in a laboratory river model

A laboratory river model for the study of biodegradation kinetics of organic pollution in surface waters is presented. It enables an engineering - technological prediction of the impact of wastewater biodegradation on DO and TOC profile in a river downstream from the point of entry of wastewater effluent thus providing rapidly and inexpensively significant design information to an environmental scientist or engineer. The method was applied to the determination of degradation of pharmaceutical wastewaters. Biodegradation during adaptation and a comparative study on organic constituents, biodegradation rates in polluted and unpolluted river waters were simulated.

The relationships of Hg(II) volatilization from a freshwater pond to the abundance ofmer genes in the gene pool of the indigenous microbial community

The role of biological activities in the reduction and volatilization of Hg(II) from a polluted pond was investigated. Elemental mercury was evolved from pond water immediately following spiking with(203)Hg(NO3)2, whereas an acclimation period of 36 hours was required in control samples collected from a nearby, unpolluted river before onset of volatilization. Genes encoding the bacterial mercuric reductase enzyme (mer genes) were abundant in DNA fractions extracted from biomass of the pond microbial community, but not in samples extracted from control communities. Thus, evolution of Hg(0) was probably due to activities mediated by the bacterial mercuric reductase. Of four characterizedmer operons, the system encoded by transposon 501 (mer(Tn501)) dominated and likely contributed to the majority of the observed Hg(II) volatilization. Thus,mer-mediated reduction and volatilization could be used to reduce Hg(II) concentrations in polluted waters, in turn decreasing rates of methylmercury formation by limiting substrate availability.

Trace metal behaviour in a highly stratified Mediterranean estuary: the Krka (Yugoslavia)

The distribution of total dissolved trace metals (Pb, Cd, Cu, Ni and Fe) in the Krka River estuary was studied in May 1988 during the high-productivity period. The dissolved metal concentrations in the freshwater end-member are: Pb 0.08 nM; Cd 0.044 nM; Cu 1.78 nM; Ni 2.47 nM; and Fe 24.1 nM. These concentrations are of the same order of magnitude as those observed in unpolluted rivers throughout the world and are in accordance with the carbonate nature of the catchment of the Krka River, which is, further, located in a national park. The trace metals in the plume show low reactivity during estuarine mixing. In contrast to most estuarine data, dissolved trace metal concentrations are generally lower in the river water than in seawater. However, the bottom saline waters of the estuary are inhomogeneous with regard to dissolved trace metal concentrations, which increase with water age. This may be due to degradation of organic matter. There is no clear evidence for accumulation of dissolved trace metals at the freshwater-seawater interface. This is dependent on the physico-chemical properties of the metals involved and may be more readily detected at downstream sites.

Variation in Species Composition of Diatom Assemblages in an Unpolluted River.

Spatial variation of attached diatom assemblages was surveyed in an unpolluted river, the River Saguri in Niigata Prefecture, Japan, and the causes of the observed variation were analyzed. The result of cluster analysis indicated that the spatial variation of diatom assemblages was correlated to stream order and current velocity. Relative abundance of Fragilaria vaucheriae (Kutz.) Peters, Gomphonema angustum Ag. and Rhoicosphenia abbreviata (Ag.) Lange-B. in the assemblages collected from the first-order streams was less than that in the assemblages collected from the higher-order streams. In the first-order streams, a group of diatoms such as Gomphonema gracile Ehr., G. hebridense Greg., and Navicula angusta Grun. occurred when the current velocity was quite slow. There was little variation in the species composition between different substrata.

The Microbial Degradability of Aniline in River Water and an Attempt to Use the Level of the Biodegradability as an Indicator of Water Pollution.

The microbial degradation of 6 chemicals in river water samples was tested using the cultivation method (Handai Method). Since aniline showed a regional difference, its microbial degradability was investigated in detail using the modified Handai Method to evaluate the possibility of its indication of water pollution caused by organic substances. The results were as follows. n-Butylacrylate was easy biodegradable and Diazinon was degraded to some degree. The microbial degradability of aniline in river water was different. The biodegradation rate increased slowly in unpolluted river water from rural areas, but increased rapidly in polluted river water from urban areas. Additionally, the biodegradation of aniline in these test samples was assumed to tend to be slightly higher in summer than in winter. This suggested that the microbial degradability of aniline in urban river water could be an indicator of water pollution because of the close correlation with the degree of water quality.