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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.
The study was carried out in the hydrologic year 2006 and comprised two small agricultural catchments in the Masurian Lakeland. Both catchments possessed very large water retention potential (presence of buffer zones and surface waters in the catchments) but they differed in the intensity of agricultural production. The study has demonstrated that the concentration of phosphorus in the surface waters flowing from the catchments ranged from 0.12 to 0.43 mg⋅dm-3. The catchments were characterised by low indices of water overland flow (0.32-1.67 dm3⋅s-1⋅km-2), which was a decisive factor shaping the runoff of phosphorus (from 0.013 to 0.060 kg⋅ha-1⋅year-1. A subcatchment dewatered by a pipe drain system, which was used for comparison, had a water flow of 3.54 dm3⋅s-1⋅km-2 and exported much more phosphorus with its surface waters (0.39 kg⋅ha-1⋅year-1). The results obtained during our study emphasise an important role played by small landscape water retention elements in both catchments and the efficiency of buffer zones at a contact of water bodies and fields in reducing the runoff of biogenic substances, especially when agricultural production carried out on a given catchment is intensive.
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.
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 contents of calcium, magnesium and mineral carbon were investigated in the ground and surface water of shelterbelts and also in four small ponds of different surroundings as well as in water-courses of agricultural landscape. In these studies, differences among the concentrations of calcium, magnesium and mineral carbon were attributed solely to different surroundings of the ponds and water-courses, and also to width of the shelterbelt. The biogeochemical barrier in the form of shelterbelt efficiently decreases the concentration of chemical substances included in the dry mass from 30 to 75%, calcium from 20 to 54%, magnesium from 46 to 72% and also mineral carbon from 58 to 71%. The smallest contents of every investigated substance characterized the water of pond surrounded by a wide zone of meadow.
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