The negative impact of agricultural pollution with biogenic materials on surface water bodies is a relevant problem. This problem is addressed by limiting or prohibiting certain activities in the so called buffer areas. The biogenic materials are carried by surface or groundwater runoff. Water infiltration is influenced by the lithological composition of sediments. River basins of sandy lithological structure were selected throughout the territory of Lithuania. An installed system of lysimeters in the boreholes allowed monitoring the change of water quality of sediments over time. The migration patterns of nutrients where identified during the investigation in the spring, summer and autumn seasons.

Establishment of sedimentation ponds is a method to reduce the negative impact of forest management (fellings, drainage) on the quality of nearby rivers, lakes and streams. The aim of the study was to determine the efficiency of sedimentation ponds in forest drainage systems during high precipitation periods. Nine sedimentation ponds with different drainage areas were analysed. The sedimentation ponds are located in the northern part of Latvia on different types of soils and managed by the Joint Stock Company ‘Latvia’s State Forests’. In order to determine efficiency of these ponds the following parameters in water samples were measured: nitrate (NO3 -), ammonium (NH4 +), phosphate ion (PO4 3-), total nitrogen and total suspended solid concentration. The amount of precipitation was taken into account. Results show that there is a correlation between the amount of precipitation and concentrations of total suspended solids and total nitrogen. Ammonium ion concentration was the only parameter that significantly exceeded water quality standards in Latvia. Only one of the objects had high concentration of pollutants, which could be explained with the peaty soil of its drainage area. In further studies data should be collected more frequently, three or four days during one precipitation period.

The objective of the present studies has been to estimate peculiarities of nitrogen removal in constructed wetlands of different construction. In limited companies (LTD) 'Pastoge' and 'Nikola', constructed wetlands of vertical flow (VFCW) are arranged, while limited company (LTD) 'Agaras' has two-stage constructed wetlands of horizontal flow (HFCW). In all the objects the supplied wastewater is after primary treatment. Having compared the efficiency of ammonium and nitrite nitrogen removal in two types of constructed wetlands (VFCW and HFCW) it was determined that larger amounts of total nitrogen are removed in HFCW (38.1%) rather than in VFCW (24.4%). However, in VFCW smaller amounts of ammonium and nitrite nitrogen are discharged with wastewater. No significant effect of the fluctuations of ambient temperature on the removal of ammonium and nitrite nitrogen was observed in HFCW (difference in average values of cold and warm periods was 3-8%). A rather reliable relation (R2 = 0:738) was determined between ammonium nitrogen concentrations in wastewater outflow and HFCW load according to total nitrogen, however, ammonium nitrogen amounts in treated wastewater (when filter load according to total nitrogen is 0.3 to 4.6 g mE-2 dE-1) exceeded the maximum allowable concentration (MAC) and were fluctuating from 6 to 32 mg lE-1.