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This paper discusses research into the seasonal variability of concentrations of total carbon (TC), dissolved organic substances (DOC), and humic substances (HS) migrating with ground water from cultivated fields. Moreover, the effects of biogeochemical barriers such as meadow belts, shelterbelts and small field ponds on limiting migration of the chemical compounds in the agricultural landscape were analysed. It was found that ground water of the studied area contains high concentrations of all examined elements averaging from 44.7 to 73.1 mg/1 of TC, from 224 to 43.6 mg/1 of DOC, and from 6.84 to 20.3 mg/1 HS. It was shown that a 20 m wide meadow belt reduces concentration of TC in ground water by 29%, that of DOC by 44%, and HS by 52%. Moreover, it was found that surface waters of the studied area also contain high concentrations of TC (mean from 65.7 to 78.3 mg/1), DOC (47.8 mg/1), and HS (from 21.3 to 34.0 mg/1). The study results show that such biogeochemical barriers as meadow belts and small field ponds effectively limit the spread of organic compounds migrating with ground water through agricultural landscapes.
Different forms of nitrogen (total, organic, amino acids in dry mass and in humic acids) as well as humus substances, dry mass, activity of ureasein ground water and in soils under mild-field deciduous afforestation were measured. Experiments were carried out during an entire year. Afforestation decreased total organic substancesin ground waters, as well as total nitrogenand free and bound amino acids to humic acids. In soil under afforestationthe decreaseof pH, activity of urease,and the content of amino acids in humic acids was observed.
The investigations were carried out from 1997 to 2001. It was shown the function of the leafy shelter-belt as biogeochemical barrier of total length 114 m by changes of different forms of nitrogen in soil (total, nitrate, ammonium and organic) and in the ground water under shelterbelt and also activity of urease in soil. This shelterbelt is located on two kinds of soil. It was found the impact of the edge of the shelterbelt on the changes of different forms of nitrogen in soil and in ground water and also activity of urease in soils. It was observed that the significant impact on the decrease of nitrogen in ground water and in soils exerts the distance from the edge of shelterbelt. The highest decrease of analyzed compounds was observed in the first sector of shelterbelt (16.5 m). Additionally the effect of eluted cations Ca+2 and Mg+2 on the compensation of pH value of the ground water was also observed.
The aim of this paper is to compare the chemistry of surface waters taken from two areas: Poland (Wielkopolska) and Lithuania. These two areas have different environments and different agricultural utilization. The high concentration of both nutritive compounds and dissolved humic substances were found in the Wielkopolska Region, where a great proportion of cultivated fields and intensive agrotechnics are observed. Surface waters located in Lithuania, with a high percentage of wasteland such as bogs, pastures and meadows, showed much lower concentrations of the analysed components. The analysis of content of heavy metals in surface waters showed much greater concentrations of manganese, lead and zinc in Lithuanian water, which can be related to considerable atmospheric pollution of this area.
This paper presents a study on the concentration of dissolved organic carbon (DOC) and humic substances (HS) in the waters of two different small ponds located in agricultural environments. DOC and HS content is high in the water of pond R adjacent to cultivated fields (DOC 42.0 mg/1, HS 34.2 mg/1) and in pond H surrounded by a wide belt of meadow and settled by macrophytes (DOC 48.0 mg/1, HS 37.2 mg/1). The total amounts of cations and cations bounded with humic substances dissolved in water of these two ponds have been analyzed. These studies indicate that small field ponds are a good biogeochemical barrier controlling organic compound migration with water from arable fields into water reservoirs.
The study included the measurement of the concentrations of N-NO₃⁻, N-NH₄⁺and organic nitrogen in the ground water of cultivated fields, and in the water of the subdrain as well as in the water of a small pond. The investigation included different forms of nitrogen in the precipitation and the run-off water. The water of the subdrain was characterized by a relatively richness in nitrates. The highest concentrations of nitrates were measured in the water of the subdrain. However, N-NH₄⁺ dominated in the precipitation water. Moreover, the contents of organic nitrogen were the highest in the water of the run-off. It was observed that 57% of the total amount of nitrogen supplies to the pond remained in a dissolved form. In general, the small pond showed a high decrease in different forms of nitrogen and showed a high degree of biological transformation. Evidently, the small pond of the agricultural landscape functions as a very efficient biogeochemical barrier.
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