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201.
The inorganic nitrogen transformations occurring at a municipal waste leachate treatment facility were investigated. The treatment
facility consisted of a collection well and an artificial wetland between two aeration ponds. The first aeration pond showed
a decrease in ammonium (from 3480 (± 120) to 630(± 90) mg ⋅ L−1), a reduction in inorganic nitrogen load (3480 to 1680 mg N ⋅ L−1), and an accumulation of nitrite (< 1.3 mg-N ⋅ L−1 in the collection well, to 1030 mg-N ⋅ L−1). Incomplete ammonium oxidation was presumably the result of the low concentration of carbonate alkalinity (∼2 mg ⋅ L−1), which may cause a limitation in the ammonium oxidation rate of nitrifiers. Low carbonate alkalinity levels may have been
the result of stripping of CO2 from the first aeration pond at the high aeration rates and low pH. Various chemodenitrification mechanisms are discussed
as the reason for the reduction in the inorganic nitrogen load, including; the reduction of nitrite by iron (II) (producing
various forms of gaseous nitrogen); and reactions involving nitrous acid. It is suggested that the accumulation of nitrite
may be the result of inhibition of nitrite oxidizers by nitrous acid and low temperatures. Relative to the first aeration
pond, the speciation and concentration of inorganic nitrogen was stable in the wetlands and 2nd aeration pond. The limited
denitrification in the wetlands most probably occurred due to low concentrations of organic carbon, and short retention times. 相似文献
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为了研究氮化肥施入农田对地表水和地下水的影响 ,在一种特殊的大型人工模拟土层和地下水装置中进行试验。研究结果表明 :即使尿素和生物矿质复混肥以中、低施肥量施入水田 ,也会造成地表淹水、耕层土壤和不同深度土层溶液有较高含量的有机 N和 N H3- N,并对地下水补给状况极差的地下水有明显的污染 ;水田中 N O- 3 - N很难长期存在 ,其污染程度可忽略不计 相似文献
206.
207.
De Schrijver A Staelens J Wuyts K Van Hoydonck G Janssen N Mertens J Gielis L Geudens G Augusto L Verheyen K 《Environmental pollution (Barking, Essex : 1987)》2008,153(2):295-303
This paper compares different vegetation types (coniferous and deciduous forest, grassed and pure heathland) in terms of input (throughfall deposition) and output (seepage flux) in a region with intermediate nitrogen load (+/-20kg Nha(-1)y(-1) via bulk precipitation) in comparable conditions in north Belgium. Coniferous forest (two plots Pinus sylvestris and two plots Pinus nigra) received significantly higher nitrogen and sulphur throughfall deposition than deciduous forest and heathland. Grassed and pure heathland had significantly highest throughfall quantities of Ca(2+) and Mg(2+), respectively. The observed differences in throughfall deposition between the different vegetation types were not univocally reflected in the ion seepage flux. Considerable seepage fluxes of NO(3)(-), SO(4)(2-), Ca(2+) and Al(III) were only found under the P. nigra plots. We discuss our hypothesis that the P. nigra forests already evolved to a situation of N saturation, while the other vegetation types did not. 相似文献
208.
Subsurface soils near Clyde Forks, Ontario, Canada, can have naturally high concentrations of mercury (Hg) from local geological sources. To investigate Hg in local aquatic food webs, Hg was measured in fish dorsal muscle (mainly yellow perch [YP] and pumpkinseed sunfish [PS]) and surface sediments from 10 regional lakes. Water chemistry, along with fork length, weight, and stable isotopes (delta15N, delta13C, delta34S) in fish were also measured. No lake sediments had elevated (>0.3microg/g dw) Hg, and average Hg concentrations in fish were not sufficiently high (<1microg/g dw) to be of concern for fish-eating wildlife. Variance in fish Hg was best explained by dietary carbon source (delta13C), and certain lake variables (e.g., pH for YP). PS with more pelagic feeding habits had higher delta34S and Hg than those with more littoral feeding habits. Potential biological linkages between fish Hg and delta34S, a parameter that may be related to the lake sulphate-reducing bacteria activity, requires further investigation. 相似文献
209.
Changes in the dynamics of inorganic N species transformations with depth have been investigated for seven soil profiles from a nitrogen-impacted ancient grassland on a nature reserve outside York in the UK, using incubation experiments. In five of the profiles, both ammonification and nitrification are occurring below the rooting zone, probably partly in response to the low C:N ratio in the soils. This contributes to elevated nitrate concentrations found in an adjacent stream. Accumulation of ammonium during incubation in the sub-soils of these five profiles suggests a high probability of ammonium leaching down the profiles as ammonium inputs and outputs at a given depth approach equilibrium. This ammonium may also be nitrified at depth. However, in the two profiles with the most acidic surface horizons, net mineralization was negligible or negative; some initial ammonium-N and ammonium-N produced during incubation were nitrified, so the loss in ammonium-N was closely balanced by nitrate-N production. 相似文献
210.
Boxman AW Peters RC Roelofs JG 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):1252-1259
In a Scots pine forest the throughfall deposition and the chemical composition of the soil solution was monitored since 1984. (Inter)national legislation measures led to a reduction of the deposition of nitrogen and sulphur. The deposition of sulphur has decreased by approximately 65%. The total mineral-nitrogen deposition has decreased by ca. 25%, which is mainly due to a reduction in ammonium-N deposition (−40%), since nitrate-N deposition has increased (+50%). The nitrogen concentration in the upper mineral soil solution at 10 cm depth has decreased, leading to an improved nutritional balance, which may result in improved tree vitality. In the drainage water at 90 cm depth the fluxes of NO3− and SO42− have decreased, resulting in a reduced leeching of accompanying base cations, thus preserving nutrients in the ecosystem. It may take still several years, however, before this will meet the prerequisite of a sustainable ecosystem. 相似文献