خيارات البحث
النتائج 1 - 10 من 11
Leeches as indicators of dietary mercury exposure in non-piscivorous waterfowl in central Ontario, Canada
1997
McNicol, D.K. | Mallory, M.L. | Mierle, G. | Scheuhammer, A.M. | Wong, A.H.K. (Canadian Wildlife Service, Ontario Region, 49 Camelot Drive, Nepean, Ontario K1A 0H3 (Canada))
PCBs and PCDD/Fs in lake sediments of Grosser Arbersee, Bavarian forest, South Germany
1997
Bruckmeier, B.F.A. | Juttner, I. | Schramm, K.W. | Winkler, R. | Steinberg, C.E.W. | Kettrup, A. (GSF-National Research Center for Environment and Health, Institute of Ecological Chemistry, D-85764, Obserschleissheim (Germany))
Environmental concerns in the Laguna de Bay basin [Philippines]
1997
Tomboc, C.C. | Francisco, F.F. (Laguna Lake Development Authority, Pasig, Metro Manila (Philippines))
Isolation, identification and bioremediation potential of oil-degrading bacteria from Manila Bay and Pasig River [Philippines]
1997
Dela Cruz, J. | Halos, P.M.
Oil-degrading bacteria were isolated from waters and sediments of the Manila Bay and Pasig River [Philippines]. Five types of bacteria were isolated from Manila Bay and four from Pasig River. The identified crude oil degrading species are Vibrio sp., Alcaligenes sp., Flavobacterium indologenes and Acinetobacter sp. from Manila Bay, and Pseudomonas aeruginosa, Bacillus sp., Micrococcus sp. and Pseudomonas putida from Pasig River. These isolates were identified through morphological and physiological characterization. The bioremediation potential for each of the isolates was assessed. The percentages oil conversion for the bacterial isolates ranged from 2.99 percent - 53.44 percent in one week's time. Alcaligenes sp. exhibited the highest biodegradation potential for all isolates. Statistical analysis revealed that the mean percentages diesel oil conversion by the isolates were significantly higher than their mean percentages crude oil conversion. Pure and mixed cultures did not give significant differences in their mean percentages crude oil conversion
اظهر المزيد [+] اقل [-]Key water quality parameters for sustainable development of Laguna de Bay, Philippines
1997
Barril, C.R. | Tumlos, E.T. (Philippines Univ. Los Banos, College, Laguna (Philippines). Inst. of Chemistry)
Review of the biological studies on Laguna de Bay [Philippines] in relation to aquatic pollution
1997
Guerrero, R.D. III (Philippine Council for Aquatic Marine Research and Development, Los Banos, Laguna (Philippines))
Laguna de Bay is the largest freshwater body in the Philippines with multiple-use. The primary use of the lake is to serve as the future domestic water supply at Metro Manila. The biota of the lake consists of 25 species of fish, 24 species of zooplankton, two species of shrimps, 6 species of mollusks, 42 species of aquatic macrophytes and 154 species of algae. A total of 60 mesophilic anaerobic and facultative anaereobic bacteria and 453 bacterial strains belonging to 22 genera have been identified. A review of 12 papers dealing with biological studies on Laguna de Bay in relation to aquatic pollution is presented. Studies on the impact of heavy metal, pesticide and thermal pollution on the biota of the lake have been sporadic and cursory. There is need for a more comprehensive and systematic monitoring of the lake's pollutants to provide time-series for pollution abatement
اظهر المزيد [+] اقل [-]Sources of trace metals in streams and headwater lakes in finland
1997
TARVAINEN, TIMO | Lahermo, Pertti | MANNIO, JAAKKO
Distributions of Mn, Zn, Cu, Ni, Cr, Pb, As, and Cd in Finnish surface waters were studied by comparing two data sets: samples from 154 headwater lakes collected by the Water and Environment Administration in 1992 and samples from 1165 headwater streams collected during the environmental geochemical mapping program of the Geological Survey of Finland in 1990. It was expected that headwater lakes with catchments smaller than 1 km²; and high lake percentage (ratio of lake area to catchment size) would be more influenced by atmospheric trace metal deposition than the streams, with average catchment size of 30 km²;.The lakes with highest arsenic concentrations lie in an area with greenstones and arsenic-rich black schists. The same lakes have high copper concentrations, which evidently are derived from the Cu-rich greenstones of the catchment. The high copper concentrations of streams and lakes in the industrialized region of the southwest coast are due to several anthropogenic sources.The highest concentrations of chromium occur in brown stream and lake waters rich in humic matter, while manganese and zinc concentrations, which are controlled by acidity, tend to be elevated in low-pH waters. The high nickel concentrations in lakes in southwestern Finland probably are due to anthropogenic input, while Ni anomalies in stream and lake water in eastern Finland are correlated with high Ni contents of glacial till. The lead concentrations in lakes are mainly of airborne anthropogenic origin.The pattern of atmospheric deposition is reflected in the concentrations of Cd, As, Cu, Zn, and Ni in headwater lakes, but land-use, the natural distribution of metals in the overburden, water acidity, and the amount of humic substances influence the distribution of trace metals in both lakes and streams. Thus the trace metal distribution in headwater lakes cannot be used alone to estimate the contribution of anthropogenic atmospheric deposition to metal anomalies in Finnish surface waters.
اظهر المزيد [+] اقل [-]Recent lake acidification and recovery trends in southern Quebec, Canada
1997
Bouchard, André
A total of 51 lakes in southern Quebec, Canada, were sampled between 1985 and 1993 to study changes in water chemistry following reductions in SO₂ emissions (main precursor of acid precipitation). Time series analysis of precipitation chemistry revealed significant reductions in concentrations and deposition of SO₄ ²⁻ from 1981 to 1992 in southern Quebec as well as reductions in concentrations and deposition of base cations (Ca²⁺, Mg²⁺), NO₃ ⁻ and H⁺ in the western section of the study area. Reductions in atmospheric inputs inputs of SO₄ ²⁻ have resulted in decreased lakewater SO₄ ²⁻ concentrations in the majority of the lakes in our study, although only a small fraction (9 of 37 lakes used in the temporal analysis) have improved significantly in terms of acidity status (pH, acid neutralizing capacity — ANC). The main response of the lakes to decreased SO₄ ²⁻ is a decrease in base cations (Ca²⁺+Mg²⁺), which was observed in 17 of 37 lakes. Seventeen lakes also showed significant increases in dissolved organic carbon (DOC) over the period of study. The resulting increases in organic acidity as well as the decrease in base cations could both play a role in delaying the recovery of our lakes.
اظهر المزيد [+] اقل [-]Whole-catchment liming at Tjønnstrond, Norway: An 11-year record
1997
Traaen, T. S. | Frogner, T. | Hindar, A. | Kleiven, E. | Lande, A. | Wright, R. F.
In June 1983 a whole-catchment liming experiment was conducted at Tjønnstrond, southernmost Norway, to test the utility of terrestrial liming as a technique to restore fish populations in remote lakes with short water-retention times. Tjønnstrond consists of 2 small ponds of 3.0 and 1.5 ha in area which drain a 25-ha catchment. The area is located at about 650–700 meters above sea-level in sparse and unproductive forests of spruce, pine and birch with abundant peatlands. A dose of 3 ton/ha of powdered limestone were spread by helicopter to the terrestrial area. No limestone was added to the ponds themselves. The ponds were subsequently stocked with brown and brook trout.Liming caused large and immediate changes in surface water chemistry; pH increased from 4.5 to 7.0, Ca increased from 40 to 200μeq/L, ANC increased from −30 to +70μeq/L, and reactive-Al decreased from about 10 to 3μmol/L. During the subsequent 11 years the chemical composition of runoff has decreased gradually back towards the acidic pre-treatment situation. The major trends in concentrations of runoff Ca, ANC, pH, Al and NO₃ in runoff are all well simulated by the acidification model MAGIC. Neither the measured data nor the MAGIC simulations indicate significant changes in any other major ion as a result of liming.The soils at Tjønnstrond in 1992 contained significantly higher amounts of exchangeable Ca relative to those at the untreated reference catchment Storgama. In 1992 about 75% of the added Ca remains in the soil as exchangeable Ca, 15% has been lost in runoff, and 10% is unaccounted for.The whole-catchment liming experiment at Tjønnstrond clearly demonstrates that this liming technique produces a long-term stable and favourable water quality for fish. Brown trout in both ponds in 1994 have good condition factors, which indicate that the fish are not stressed by marginal water quality due to re-acidification. The water quality is still adequate after 11 years and >20 water renewals. Concentrations of H⁺ and inorganic Al have gradually increased and approach levels toxic to trout, but the toxicity of these are offset by the continued elevated Ca concentrations. Reduced sulphate deposition during the last 4 years (1990–94) has also helped to slow and even reverse the rate of reacidification. The experiment at Tjønnstrond demonstrates that for this type of upland, remote terrain typical of large areas of southern Norway, terrestrial liming offers a suitable mitigation technique for treating acidified surface waters with short retention times.
اظهر المزيد [+] اقل [-]Whole-catchment liming at Tjoennstrond, Norway: an 11-year record
1997
Traaen, T.S. (Norwegian Inst. for Water Research, Oslo (Norway).) | Frogner, T. | Hindar, A. | Kleiven, E. | Lande, A. | Wright, R.F.