engleski

Leaching of Some Pollutants into Drainage Water in Croatia

This study was designed to determine the concentration and total leaching of nitrate, atrazine and heavy metals (Pb, Zn and Cd) in drainage water and their contents in soil (until 0.30 m) at four different pipe drainage spacings (15 m, 20 m, 25 m and 30 m) and to determine the yield of corn for each spacing. The study was conduced on reclamed field of hydroameliorated Gleyic Podzoluvisol over five years. The corn was grown and the same agricultural practices were applied to all drainage pipe variants in each of the five trial years. Weed protection was primextra (6 dm3.ha-1) and the nitrogen fertilization rate ranged from 145 kg.ha-1 to 175 kg.ha-1 and varied from year to year. Drainage discharge was measured continually by automatic limnimeters. Drainage was sampled three times each month during the discharge period. Nitrate content was determined using yellow coloring of phenol disulphonic acid, atrazine content was determined using chromatographic analysis, and heavy metal content (Pb, Zn and Cd) was measured by AAS. The annual quantities of leached nitrogen, atrazine and heavy metals were estimated on the basis of average yearly concentration and yearly quantity of drainage discharge. Data were statistically processed by means of the analysis of variance. Based on the results, we confirmed that maximum and average concentrations of NO3 – N and atrazine in drainage waters from all pipe drainage spacing exceeded the allowable values of 10 mg.dm-3 and 0.1 μ g.dm-3, respectively. One-year average concentrations of NO3 – N at all variants were below allowable values. The maximum concentration of NO3 – N recorded was 32.82 mg.dm-3 and the maximum concentration of atrazine recorded was 7.58 μ g.dm-3. The quantity of nitrogen leached per pipe spacing variant fluctuated from 35.7 kg.ha-1 (or 20.4% relative to the total N added with fertilization) to 15.8 kg.ha-1 ( or 10.2%). The quantity of atrazine leached fluctuated from 5.07 g.ha-1 (or 0.42% ) to 1.71 g.ha-1 (or 0.14%). Concentrations of heavy metals in drainage water and in soil at all pipe spacing variants and in all years were below allowable values. Concentrations of nitrogen and atrazine and the amounts leached varied from variant to variant and from year to year. The highest soil concentrations (and amounts leached) of all pollutants in drainage water and at all variants were recorded soon after fertilizer was applied and after higer precipitation events (t.i. drainage discharge). There were no statistically significant differences between the tested variants and pollutants in drainage water and in soil in any particular year. As a rule, the highest yields were achieved in the drainpipe spacing variant of 15 m and the lowest in drainpipe spacing variant of 30 m. The yields fluctuated from 88 dt.ha-1 (15 m) to 43.48 dt.ha-1 (30 m).

leaching; polutants; drainage; water; Croatia

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