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391.
The main aim of this study was to increase our knowledge on how fish farm effluents influences the surface water quality in the Åland archipelago (Baltic Sea). A second aim was to conduct critical model tests of three models that predicts the impact of farm emitted phosphorus on total phosphorus (TP), chlorophyll and Secchi depth. Extensive field studies were conducted between 1997 and 1999 in nine defined coastal areas with, and four reference areas without, fish farms. According to our results the most significant effects on TP concentrations, periphytic growth and phytoplankton standing crop was observed in two coastal bays with small to moderate fish farm production (≈70 tonnes per year). The significant effects in each bay was mainly due to the small size of the bay (0.48 and 0.73 km2) and the shallow mean water depth (3 and 3.8 m), rather than long water retention times (2 and 6 days). Due to a very large fish farm production (800 tonnes per year), we also observed significant effects in a coastal area of moderate size (8 km2), which had a theoretical water retention time of about 8 days. No significant effects of fish farm effluents on the surface water quality were observed in the other six areas. Furthermore, our data shows that, besides the fish farm effluents, the import of nutrients from the surrounding sea and the sediment resuspension may have a decisive effect on the water quality in the studied areas. Finally, we can conclude that at least two of the tested models are useful in context of environmental management. 相似文献
392.
Maija Pesonen Tiiu Hansson Lars Förlin Tommy Andersson 《Fish physiology and biochemistry》1990,8(2):141-145
The regional distribution of microsomal cytochrome P-450-mediated reactions with exogenous and endogenous substrates in the
kidney of rainbow trout was studied. The cytochrome P-450-dependent 7-ethoxyresorufin- and 7-ethoxycoumarin-0-deethylase activities
were significantly higher (3–4 and 10–14 fold, respectively) in the trunk kidney than in the head kidney, whereas ethylmorphine-N-demethylase
activity was evenly distributed along the kidney. The microsomal cytochrome P-450-dependent steroid hydroxylases and steroid
reducing enzymes when using androstenedione as substrate also exhibited a regional distribution in trout kidney. The 6β- and
16-hydroxylase activities as well as the 5α-reductase and 17 hydroxysteroid oxidoreductase activities were higher in the anterior
part of the trunk kidney than in the head kidney and posterior trunk kidney. 相似文献
393.
The concentration of Hg in muscle was monitored during 10 to 12 years in different size and age groups of pike (Esox lucius) and perch (Perca fluviatilis). The study was performed in one reference and five lime treated lakes. Before liming, the highest levels of Hg in fish were measured in a lake with an annual mean pH just above 5.0. Lower levels were obtained both in lakes which were more acidified and in those which were less acidified. After the start of liming, the fastest and largest changes were obtained in the lakes which were moderately acid before liming (mean pH 5.4–5.8). In small perch, the Hg-concentration was markedly reduced in two years and showed an 80 % decrease in ten years. A slower response was registered in the lakes originally having about 0.5 units lower pH. In the most acidified lake (pH 4.9) the concentrations even increased the first years after liming, but decreased again later on. The possible mechanisms involved are discussed. 相似文献
394.
Ylva Andrist‐Rangel Magnus Simonsson Stefan Andersson Ingrid
born Stephen Hillier 《植物养料与土壤学杂志》2006,169(5):605-615
The study was conducted to investigate the relationship between some standard measures of soil reserve potassium (K) and soil mineralogy. Eight different agricultural soils from the N temperate and S boreal regions were studied and analyzed both by standard methods (exchangeable K, 2 M HCl‐ and aqua regia–extractable K) and by quantitative mineralogical methods based on X‐ray powder diffraction analysis of spray‐dried bulk soils. Linear regression and multivariate methods were used to assess the relationships between standard measures of soil reserve K and a number of soil chemical, physical, and mineralogical properties. A mineralogical budgeting approach, to estimate total K and its speciation between different mineral phases, is shown to be accurate after validation against total K analyzed geochemically. This approach enabled us to determine that both HCl‐ and aqua regia–extractable K were highly correlated with K in dioctahedral phyllosilicates and extracted 1%–17% and 5%–45% of total K, respectively. Neither extraction showed any obvious relationship to K in feldspar, which is frequently a larger reservoir of K in the soils examined. 相似文献
395.
Bengt Hasselrot Ingvar B. Andersson Ingemar Alenäs Hans Hultberg 《Water, air, and soil pollution》1987,32(3-4):341-362
Occurrence of stratified acidic water is described for five forest lakes situated in the westcoast region of Sweden. Differentiation between two types of acid events is made related to origin; one is caused by heavy rains and the other associated with snowmelt during winter and spring. Acid events are due to incomplete mixing between lake and inflow water. Both mixing forces like wind and density differences are important factors regulating the actual stratification. As observed in the lakes studied, stratification therefore occurs during periods of ice-cover when wind-induced mixing is impeded and generally results in an acidic surface water of varying depth. However, in this study we also describe the stratification of acidic inflow water at the sediment-water interface. This type of inlayering is presumably less frequent as a complex set of conditions must be satisfied for its occurrence. Our study shows that acid events may cause temporal and spatial water chemistry changes even in lakes and streams with relatively high pH and buffer capacity. Thus, early biotic damages can be expected in neutral and limed (soft water) lakes. 相似文献
396.
beta-(1-->3),(1-->4)-D-Glucan (beta-glucan) was extracted from 93 Swedish and 41 American oat samples using hot water containing CaCl(2) and thermostable alpha-amylase. The samples showed a large variation in both the content of extractable beta-glucan (0.76-3.68%) and the average molecular weight ((1.25-1.78) x 10(6) g mol(-1)). An analysis of the variance of beta-glucan content and the molecular weight of Swedish oat samples grown in 2000 and 2001 was done with cultivar and harvest year as factors. It showed that the extractable beta-glucan content was a heritable trait whereas molecular weight depended more on environmental factors. The American oat samples had a higher average content of extractable beta-glucan (2.24%) and a somewhat higher average molecular weight (1.58 x 10(6) g mol(-1)) than the Swedish oat samples (1.43% and 1.49 x 10(6) g mol(-1)). 相似文献
397.
It is now widely accepted that many plants and mycorrhizal fungi have the ability to take up organic nitrogen (N) in the form of amino acids, although the importance of this uptake in the field is less clear. In the laboratory it has been shown that uptake affinity and uptake kinetics of ammonium and some amino acids are comparable. The relative uptake of either N form from the soil solution would thus be related to the relative concentration in the soil solution accessed by roots. We sampled soil solution from the F- and H-layers under a Spruce stand in a fertilisation experiment in Flakaliden, northern Sweden. Tension lysimeters were installed in plots receiving irrigation (I) or irrigation plus liquid fertilisation (IL). The soil solution samples were analysed for ammonium, nitrate, free amino acids, hydrolysable amino acids, total organic N and total organic C. In I plots the concentrations of both ammonium and free amino acids were very low with no obvious dominance of either form. In IL plots inorganic N concentrations were higher and amino acid concentrations were lower compared to I plots, and thus the inorganic N dominated over amino acids. There was no difference in H-layer ammonium concentration between I and IL plots despite the high N addition rate on the soil surface during nights of sampling. The lower amino acid concentrations in IL plots might be an effect of a decreased proteolytic activity due to the documented shift in mycorrhizal fungi species composition at the site. 相似文献
398.
Castiñeira Gómez Mdel M Brandt R Jakubowski N Andersson JT 《Journal of agricultural and food chemistry》2004,52(10):2953-2961
Elemental patterns are often used for the classification or identification of the origin of wines. A prerequisite is that the concentration of the elements is not strongly influenced by the addition of different substances such as yeast and fining products during the winemaking process. Inductively coupled plasma-mass spectrometry (ICP-MS) has been used in this study to determine in total 63 elements (including some nonmetals and the rare earth elements) in five German white wines from five regions of origin. The whole winemaking process was studied, from the must to the ready wine. Microwave acid digestion was used for sample preparation, and indium was added as internal standard for a semiquantitative analysis. Two winemaking processes were compared: with the addition of clarifying agents (bentonites) before and after the fermentation. The concentration of only a few elements such as Li, B, Mg, Ca, Rb, Cs, and Pb seems to be constant throughout the whole winemaking process (changes of <+/-50%) and are independent of the time of addition of the bentonites. When bentonites are added before fermentation, the concentration of other elements, such as V, Co, and Fe, remains constant. If bentonites are added after fermentation, the concentration of some other elements such as Sr, Zn, and Mn is nearly unaffected. These elements are therefore robust elements for origin studies in German white wines. 相似文献
399.
We investigated the fate of added N and its effect on N fluxes in a long-term nitrogen fertilisation experiment. Ammonium nitrate was added annually (30 years) at mean rates of 0 (N0), 35 (N1), 73 (N2) and 108 (N3) kg N ha?1 yr?1 to a spruce forest in Sweden, which initially showed signs of N deficiency. Net N mineralisation and N leaching were measured in situ together with soil N pools. We used the PnET-CN model to model the maximum sustainable net N mineralisation rate. The short-term fate of added N was studied by addition of 15NH4Cl. In N1 and N2 most of the added N (80–120%) was retained in the system, compared to 45% in N3. A major fraction was retained in the organic horizons (58–79%). The internal N fluxes had increased considerably as a result of the N additions. Net N mineralisation in N1 had increased by a factor 10 and litterfall N flux by a factor 4. The PnET-CN model could not mimic the fast changes in tree growth and N mineralisation, but the maximum N mineralisation rate seems realistic. The ratio of actual to maximum mineralisation rate indicates that the N1 treatment now is close to N saturation, and nitrate was occasionally found in soil solution from the B-horizon in N1. The N retained was probably to a great extent immobilised directly by mycorrhizal fungi, as indicated by the high amounts of 15N found in the L and F layers and by the great fraction of 15N found in amino sugars compared to amino acids. 相似文献
400.
Burning of the vegetation in the African savannahs in the dry season is widespread and may have significant effects on soil chemical and biological properties. A field experiment in a full factorial randomised block design with fire, ash and extra grass biomass as main factors was carried out in savannah woodland of the Gambella region in Ethiopia. The microbial biomass C (Cmic) was 52% (fumigation-extraction) and 20% (substrate-induced respiration) higher in burned than unburned plots 12 d after burning. Both basal respiration and potential denitrification enzyme activity (PDA) immediately responded to burning and increased after treatment. However, in burned plots addition of extra biomass (fuel load) led to a reduction of Cmic and PDA due to enhanced fire temperature. Five days after burning, there was a short-lived burst in the in situ soil respiration following rainfall, with twice as high soil respiration in burned than unburned plots. In contrast, 12 d after burning soil respiration was 21% lower in the burned plots, coinciding with lower soil water content in the same plots. The fire treatment resulted in higher concentrations of dissolved organic C (24-85%) and nitrate (47-76%) in the soil until 90 d after burning, while soil NH4+-N was not affected to the same extent. The increase in soil NO3−-N but not NH4+-N in the burned plots together with the well-aerated soil conditions indicated that nitrifying bacteria were stimulated by fire and immediately oxidised NH4+-N to NO3−-N. In the subsequent rainy season, NO3−-N and, consequently, PDA were reduced by ash deposition. Further, Cmic was lower in burned plots at that time. However, the fire-induced changes in microbial biomass and activity were relatively small compared to the substantial seasonal variation, suggesting transient effects of the low severity experimental fire on soil microbial functioning. 相似文献