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Agricoltura di terza generazione, paesaggio e storia locale. Analisi agro-ambientale e culturale del territorio di Rolle (Tv).
No full textFive year water and nitrogen balance for a constructed surface flow wetland treating agricultural drainage waters
No full textThe performance of a constructed surface flow wetland in reducing diffuse N pollution coming from croplands is being investigated in an ongoing experiment, begun in 1998 in NE Italy. The 0.32 ha wetland is vegetated with Phragmites australis (Cav.) Trin. and Typha latifolia (L.). It receives drainage water from 6 ha of land managed for an experiment on drainage systems, where maize, sugarbeet, winter wheat and soybean are cultivated. During the period 1998–2002, the wetland received from 4698 to 8412 mm of water per year (on average, about 9 times the environmental rainfall); its water regimen was discontinuous and flooding occurred on a variable number of days per year (from 13 to 126). Nitric nitrogen was the most important form of element load. Its concentration in the inflow water over time was rather discontinuous, with median values ranging from 0.2 (in 2001) to 4.5 (in 2000) mg L− 1. Inflow nitric N concentrations were occasionally in the 5–15 mg L− 1 range. Concentrations reduced passing through the wetland, with a more evident effect in the last year. Over 5 years, the wetland received slightly more than 2000 kg ha− 1 of nitrogen, 87% in nitric form mostly from farmland drainage. The remaining 13% of N was applied as organic slurry directly onto the wetland, with 5 distributions during 1998 to assess wetland performance in treating occasional organic loads. Field drainage loads had a discontinuous time pattern and occurred mostly during autumn–winter, with the exception of the 2001–2002 season which was a very dry. The wetland discharged 206 kg ha− 1 of N, over the 5-year period, with an apparent removal efficiency of about 90%. The disappearance was mostly due to plant uptake (1110 kg ha−1) and soil accumulation (570 kg ha−1), with the contribution of denitrification being estimated at around 7%
The agro-environmental structures and their multiple roles at local scale. A case study in the River Sile Natural Park (Italy)
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Performance of a floating treatment wetland for in-stream water amelioration in NE Italy
No full textFloating treatment wetlands are innovative systems and their processes are still scarcely known within the traditional methods of phytodepuration. To gain initial information on their performance and potential in removing pollutants two experiments have been conducted in north-east Italy, in a Natural Park with resurgent water. Barriers formed by a new patented floating element were tested in real climatic and water flow conditions. One experiment was conducted in a channel receiving aquaculture effluents, while the other was set in two cleaner channels to test two installation designs (two barriers composed of two lines of elements -2X2 design- and two composed of three lines of elements -2x3 design-). Different macrophyte species were used (Phragmites australis, Carex elata, Juncus effusus, Typha latifolia, Chrysopogon zizanioides, Sparganium erectum, Dactylis glomerata).
The floating systems were easily installed and required few maintenance operations. Native plants grew successfully, developing roots 90-135 cm deep one year after planting. Conversely, Chrysopogon zizanioides showed scarce adaptation to local conditions.
In the first experiment median chemical oxygen demand (COD) in water passing through the floating wetland system was reduced by 66%, biochemical oxygen demand by 52%, and total phosphorus by 65%. In the second experiment the 2x3 design had a slightly better performance than 2x2 in reducing COD (38% and 28% of removal respectively). The two designs performed similarly on NO3-N, reducing the incoming concentrations by 12% (2x3 design) and 14% (2x2). This form of nitrogen represents almost all the total nitrogen, which was abated by 13% by the 2x3 design and by 29% by 2x2 design
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