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181.
The performance of different policy design strategies is a key issue in evaluating programmes for water quality improvement
under the Water Framework Directive (60/2000). This issue is emphasised by information asymmetries between regulator and agents.
Using an economic model under asymmetric information, the aim of this paper is to compare the cost-effectiveness of selected
methods of designing payments to farmers in order to reduce nitrogen pollution in agriculture. A principal-agent model is
used, based on profit functions generated through farm-level linear programming. This allows a comparison of flat rate payments
and a menu of contracts developed through mechanism design. The model is tested in an area of Emilia Romagna (Italy) in two
policy contexts: Agenda 2000 and the 2003 Common Agricultural Policy (CAP) reform. The results show that different policy
design options lead to differences in policy costs as great as 200–400%, with clear advantages for the menu of contracts.
However, different policy scenarios may strongly affect such differences. Hence, the paper calls for greater attention to
the interplay between CAP scenarios and water quality measures. 相似文献
182.
The levels of extractable aluminum (Al) in soils of tea plantations, Al concentrations in tea leaves and the impact of nitrogen
fertilization on these two parameters were investigated. In addition, the properties of soils from tea plantations were compared
to those from soils of adjacent non-tea fields to evaluate the effect of land use conversion (from non-tea soils to tea soils).
Exchangeable Al (extracted in 1 mol l−1 KCl) ranged from 0.03 to 7.32 cmolc kg−1 in 94 tea fields and decreased rapidly with increasing soil pH. In comparison with non-tea soils, tea soils had a significantly
lower pH and exchangeable Mg2+ concentration but higher organic matter contents and exchangeable K+ concentration. Contents of extractable Al were not different (P > 0.05) between these two soils. The concentrations of Al in mature tea leaves correlated significantly with exchangeable
Al in soil samples taken at a depth of 20–40 cm and with exchangeable Al saturations in soil sampled at␣depths of 0–20 and
20–40 cm. In the pot experiment, nitrogen fertilization significantly increased extractable Al levels but decreased soil pH
and the levels of exchangeable base cations. Nevertheless, the levels of Al in mature leaves and young shoots were significantly
reduced by the application of large amounts of N fertilizer. 相似文献
183.
The determination of nitrogen (N) based loading rates for land application of biosolids is challenging and site specific. Over loading may contribute to environmental, agricultural, or human health problems. The objective of this study was to monitor N mineralization and losses in a moderately alkaline and calcareous desert soil amended with either anaerobically digested (AN) or lime-stabilized (LS) biosolids, and irrigated with and without urea enriched water. For Experiment 1, N inputs, leaching and residuals in soil were evaluated in an open soil column system. For Experiment 2, ammonia (NH3) emissions were evaluated in a closed soil column system. In Experiment 1, AN and LS biosolids increased soil ON (organic N) by three and two fold, respectively. Respective net N mineralization of ON from biosolids alone was 90% and 62% without urea, and 71% and 77%, respectively with added urea. Nitrogen leaching losses and residuals in amended soil did not account for all N inputs into the soil/biosolids system. In Experiment 2, NH3 emissions were not significantly different among treated soils with or without added urea, except LS amended soil receiving urea. Ammonia losses did not account for unaccounted N in Experiment 1. We concluded that deep placement and rapid mineralization of AN biosolids promoted anaerobic soil conditions and denitrification, in addition to the high denitrification potential of desert soil. LS biosolids showed greater potential than AN biosolids for safe and beneficial land application to desert soils regardless of biosolids placement and the inclusion of N rich irrigation water. 相似文献
184.
Spokes L Jickells T Weston K Gustafsson BG Johnsson M Liljebladh B Conley D Ambelas-Skjødth C Brandt J Carstensen J Christiansen T Frohn L Geernaert G Hertel O Jensen B Lundsgaard C Markager S Martinsen W Møller B Pedersen B Sauerberg K Sørensen LL Hasager CC Sempreviva AM Pryor SC Lund SW Larsen S Tjernström M Svensson G Zagar M 《Environmental pollution (Barking, Essex : 1987)》2006,140(3):453-462
This paper summarises the results of the EU funded MEAD project, an interdisciplinary study of the effects of atmospheric nitrogen deposition on the Kattegat Sea between Denmark and Sweden. The study considers emissions of reactive nitrogen gases, their transport, transformations, deposition and effects on algal growth together with management options to reduce these effects. We conclude that atmospheric deposition is an important source of fixed nitrogen to the region particularly in summer, when nitrogen is the limiting nutrient for phytoplankton growth, and contributes to the overall eutrophication pressures in this region. However, we also conclude that it is unlikely that atmospheric deposition can, on its own, induce algal blooms in this region. A reduction of atmospheric nitrogen loads to this region will require strategies to reduce emissions of ammonia from local agriculture and Europe wide reductions in nitrous oxide emissions. 相似文献
185.
/ A study was conducted to determine the extent of nitrogenpollution in agricultural lands in the Lower Fraser River basin of BritishColumbia, Canada. The specific objectives were to determine the distributionof leachable nitrogenand estimate the nitrogen concentration in groundwaterrecharges. Nitrogen and water mass balances were conducted on the entirebasin and on each of the four districts comprising it over the period1971-1991 in intervals of five years. The results indicated that the averagenitrogen concentration in the groundwater recharge for the entire basin rosefrom nondetectable in 1971 to 6 mg/liter in 1991. Estimates for theindividual districts ranged from 4 to 14 mg/liter in Central Fraser and fromnondetectable to 7 mg/liter in Fraser-Cheam and 3 mg/liter in both GreaterVancouver and Dewdney-Alouette. So far, excessive levels of nitrogen areconfined to Central Fraser. Although they have remained within the acceptablerange, nitrogen concentrations in the other three districts have definitelyincreased over the 20-year study period. Sensitivity analyses indicated thatanimal manure and fertilizer had the largest contribution in groundwaterrecharge. Decreasing the rate of manure application to agricultural lands issuggested as the most practical way of reducing nitrogen pollution in CentralFraser.KEY WORDS: Nitrogen balance; Water balance; Sensitivity analysis 相似文献
186.
The sulphur dioxide and nitrogen oxides emissions from all sources in Alberta, Canada, during 1982 amounted to 488,297 and 353,511 tonnes, respectively. During this year deposition of wet sulphate from all stations in the province, 8 kg ha–1 yr–1, compares well with the five-year average (1978–1982) value of 10 kg ha–1 yr–1. These measurements are about one-half of the wet sulphate deposition criteria of 20 kg ha–1 yr–1 established for protecting the moderately sensitive aquatic ecosystem in eastern Canada. Due to dry, cold, continental climate conditions of Alberta, dry sulphate or sulphur deposition is equally or more important than wet deposition. No effects of the long-range transport of atmospheric pollutants (LRTAP) on the ecosystems in Alberta have been observed to date. Atmospheric deposition target loadings of SO4
–2, NO3
–, and H+ for Alberta and western Canadian environmental conditions should be developed to protect the highly sensitive ecosystems. Some future research and monitoring priorities for Alberta and western Canada are outlined. 相似文献
187.
Eutrophication of Buttermilk Bay,a cape cod coastal embayment: Concentrations of nutrients and watershed nutrient budgets 总被引:2,自引:0,他引:2
Nutrient concentrations in Buttermilk Bay, a coastal embayment on the northern end of Buzzards Bay, MA, are higher in the nearshore where salinities are lower. This pattern suggests that freshwater sources may contribute significantly to nutrient inputs into Buttermilk Bay. To evaluate the relative importance of the various sources we estimated inputs of nutrients by each major source into the watershed and into the bay itself. Septic systems contributed about 40% of the nitrogen and phosphorus entering the watershed, with precipitation and fertilizer use adding the remainder. Groundwater transported over 85% of the nitrogen and 75% of the phosphorus entering the bay. Most nutrients entering the watershed failed to reach the bay; uptake by forests, soils, denitrification, and adsorption intercepted two-thirds of the nitrogen and nine-tenths of the phosphorus that entered the watershed. The nutrients that did reach the bay most likely originated from subsoil injections into groundwater by septic tanks, plus some leaching of fertilizers.Buttermilk Bay water has relatively low nutrient concentrations, probably because of uptake of nutrients by macrophytes and because of relatively rapid tidal flushing. Annual budgets of nutrients entering the watershed showed a low nitrogen-to-phosphorus ratio of 6, but passage of nutrients through the watershed raised N/P to 23, probably because of adsorption of PO4 during transit. The N/P ratio of water that leaves the watershed and presumably enters the bay is probably high enough to maintain active growth of nitrogenlimited coastal producers. There is a seasonal shift in N/P in the water column of Buttermilk Bay. N/P exceeded the 161 Redfield ratio during midwinter; the remainder of the year N/P fell below 161. This suggests that annual budgets do not provide sufficiently detailed data with which to interpret nutrient-limitation of producers. Further, some idea of water turnover is also needed to evaluate impact of loading rates. Urbanization of watersheds seems to increase loadings to nearshore environments, and to shift the nutrient loadings delivered to coastal waters to relatively high N-to-P ratios, potentially stimulating growth of nitrogen-limited primary producers. 相似文献
188.
Effects of stream channelization on exports of nitrogen and phosphorus from north Carolina coastal plain watersheds 总被引:1,自引:0,他引:1
Laura A. Yarbro Edward J. Kuenzler Patrick J. Mulholland Robert P. Sniffen 《Environmental management》1984,8(2):151-160
Nitrogen and phosphorus exports from channelizedstream watersheds were elevated over those from nearby natural swamp-stream watersheds. Nitrate exports were significantly greater from channelized-stream watersheds, and higher exports were attributed to faster groundwater drawdown, continual streamflow, and transformation of former floodplain to croplands following channelization. Exports of total organic nitrogen and total nitrogen were also significantly greater from channelized-stream watersheds. Differences in the exports of ammonium, filterable reactive phosphorus, and filterable unreactive phosphorus between the two watershed types were not detectable. Particulate phosphorus exports were significantly higher from channelized-stream watersheds, presumably because of greater erosion potential of nearby croplands and steep channel banks in the altered watersheds. The presence of nonpoint sources of pollution increased watershed exports of nutrients regardless of stream morphology. Examination of nutrient budgets for a portion of swamp floodplain at the base of one natural-stream watershed revealed that changes in local groundwater hydrology and stream morphology associated with channelization appeared to have greater effect on nutrient exports than simply the loss of bordering forested floodplain. 相似文献
189.
190.
Long- and short-chain AHLs affect AOA and AOB microbial community composition and ammonia oxidation rate in activated sludge 总被引:1,自引:0,他引:1
Jie Gao Yu Duan Ying Liu Xuliang Zhuang Yichen Liu Zhihui Bai Wenlin M Guoqiang Zhuang 《环境科学学报(英文版)》2019,31(4):53-62
Quorum sensing (QS) regulation of the composition of ammonia-oxidising archaea (AOA) and ammonia-oxidising bacteria (AOB) communities and functions in wastewater treatment was investigated. Specifically, we explored the role of N-acyl-l-homoserine lactones (AHLs) in microbial community dynamics in activated sludge. On average, the specific ammonia-oxidising-rate increased from 1.6 to 2.8?mg?NH4+-N/g?MLSS/hr after treatment with long-chain AHLs for 16?days, and the addition of AHLs to sludge resulted in an increased number of AOA/AOB amoA genes. Significant differences were observed in the AOA communities of control and AHL-treated cultures, but not the AOB community. Furthermore, the dominant functional AOA strains of the Crenarchaeota altered their ecological niche in response to AHL addition. These results provide evidence that AHLs play an important role in mediating AOA/AOB microbial community parameters and demonstrate the potential for application of QS to the regulation of nitrogen compound metabolism in wastewater treatment. 相似文献