Nitrate removal processes in a constructed wetland treating drainage from dairy pasture

作者：Matheson Fleur E^*; Sukias James P

来源：Ecological Engineering, 2010, 36(10): 1260-1265.

DOI：10.1016/j.ecoleng.2010.05.005

• Denitrification
• Dissimilatory nitrate reduction to ammonium
• Immobilisation
• Lemna minor
• Plant uptake
• Typha orientalis

(15)N-labelled NO(3)(-) was used in a surface-flow constructed wetland in spring to examine the relative importance of competing NO(3)(-) removal processes In situ mesocosms (025 m(2)) were dosed with 21 of (15)NO(3)(-) (NaNO(3), 300 mg Nl(-1). 99 atom% (15)N) and bromide (Br(-)) solution (LiBr, 43 gl(-1), as a conservative tracer). Concentrations of NO(3)(-), Br(-), dissolved oxygen and (15)N(2) were monitored periodically and replicate mesocosms were destructively sampled prior to and 6 clays after (15)N addition. Denitrification, immobilisation, plant uptake and dissimilatory NO(3)(-) reduction to NH(4)(+) (DNRA) accounted for 77, 11, 9 and 2% of (15)NO(3)(-) transformed during the experiment Only 6% of denitrification gases were directly measured as atmospheric or dissolved (15)N(2): the remainder (71%) was determined via (15)N mass balance This indicated that a large proportion of the denitrification gases were entrapped within the soil matrix and/or plant aerenchyma The floating plant Lemna minor exhibited a significantly higher NO(3)(-) uptake rate (221 mg kg(-1) d(-1)) than Typha orientalis (10 mg kg(-1) d(-1)), but periodic harvest of plants would remove <3% of annual NO(3)(-) inputs Our results suggest that this 6-year-old constructed wetland functions effectively as a sink for NO(3)(-) during the growing season with less than one-quarter of the NO(3)(-) processed sequestered into wetland plant, algal and microbial N pools and the balance permanently removed by denitrification.

• 出版日期2010-10