共查询到20条相似文献，搜索用时 31 毫秒
1.
Veselý Josef Hruška Jakub Norton Stephen A. Johnson Chris E. 《Water, air, and soil pollution》1998,108(1-2):107-127
Temporal changes in major solute concentrations in six Czech Republic lakes were monitored during the period 1984–1995. Four chronically-acidic lakes had decreasing concentrations of strong-acid anions (CSA = SO4 2- + NO3 - + Cl-), at rates of 3.0 to 9.0 μeq L-1 yr-1. Decreases in SO4 2-, NO3 -, and Cl- (at rates up to 5.1 μeq L-1 yr-1, 3.2 μeq L-1 yr-1, and 0.6 μeq L-1 yr-1, respectively) occurred. The response to the decrease in deposition of S was rapid and annual decline of SO4 2- in lake water was directly proportional to SO4 2- concentrations in the acidified lakes. Changes in NO3 - concentrations were modified by biological consumption within the lakes. The decline in CSA was accompanied in the four most acidic lakes by decreases in AlT, increases in pH at rates of 0.011 to 0.016 pH yr- 1, and decreases of Ca2+ and Mg2+ (but not Na+) in three lakes. The acid neutralizing capacity (ANC) increased significantly in all six lakes. Increases in base cation concentrations (CB = Ca2+ + Na+ + Mg2+ + K+) were the principal contributing factor to ANC increases in the two lakes with positive ANC, whereas decrease in CSA was the major factor in ANC increases in the four chronically-acidic lakes. The continued chemical recovery of these lakes depends on the uncertain trends in N deposition, the cycling of N in the lakes and their catchments, and the magnitude of the future decrease in S deposition. 相似文献
2.
Meijun Cai John S. Schwartz R. Bruce Robinson Stephen E. Moore Matt A. Kulp 《Water, air, and soil pollution》2011,219(1-4):547-562
The recovery potential of stream acidification from years of acidic deposition is dependent on biogeochemical processes and varies among different acid-sensitive regions. Studies that investigate long-term trends and seasonal variability of stream chemistry in the context of atmospheric deposition and watershed setting provide crucial assessments on governing biogeochemical processes. In this study, water chemistries were investigated in Noland Divide watershed (NDW), a high-elevation watershed in the Great Smoky Mountains National Park (GRSM) of the southern Appalachian region. Monitoring data from 1991 to 2007 for deposition and stream water chemistries were statistically analyzed for long-term trends and seasonal patterns by using Seasonal Kendall Tau tests. Precipitation declined over this study period, where throughfall (TF) declined significantly by 5.76?cm?year?1. Precipitation patterns play a key role in the fate and transport of acid pollutants. On a monthly volume-weighted basis, pH of TF and wet deposition, and stream water did not significantly change over time remaining around 4.3, 4.7, and 5.8, respectively. Per NDW area, TF SO4 2- flux declined 356.16?eq?year?1 and SO4 2- concentrations did not change significantly over time. Stream SO4 2- remained about 30???eq L?1 exhibiting no long-term trends or seasonal patterns. SO4 2- retention was generally greater during drier months. TF monthly volume-weighted NH4 + and NO3 - concentrations significantly increased by 0.80???eq L?1?year?1 and 1.24???eq L?1?year?1, respectively. TF NH4 + fluxes increased by 95.76?eq?year?1. Most of NH4 + was retained in the watershed, and NO3 - retention was much lower than NH4 +. Stream monthly volume-weighted NO3 - concentrations and fluxes significantly declined by 0.56???eq L?1?year?1 and 139.56?eq?year?1, respectively. Overall, in NDW, inorganic nitrogen was exported before 1999 and retained since then, presumably from forest regrowth after Frazer fir die-off in the 1970s from balsam wooly adelgid infestation. Stream export of NO3 - was greater during winter than summer months. During the period from 1999 to 2007, stream base cations did not exhibit significant changes, apparently regulated by soil supply. Statistical models predicting stream pH, ANC, SO4 2-, and NO3 - concentrations were largely correlated with stream discharge and number of dry days between precipitation events and SO4 2- deposition. Dependent on precipitation, governing biogeochemical processes in NDW appear to be SO4 2- adsorption, nitrification, and NO3 - forest uptake. This study provided essential information to aid the GRSM management for developing predictive models of the future water quality and potential impacts from climate change. 相似文献
3.
Samples were collected from 13 upland sites (main inflow and loch outflow) in the UK along an N deposition gradient of 12-50 kg ha-1 yr-1 to determine the relationship between N deposition and NO3 - concentrations in surface waters. There was no direct correlation between NO3 - leaching and soluble inorganic N deposition at these sites, but a significant relationship with NO3 - was found using a deposition function incorporating dissolved organic carbon (DOC) flux from each catchment. A similar but less significant relationship was found between NO3 - concentration and DOC:DON ratio in runoff water. Catchments showed evidence of N saturation, i.e., when mean NO3 - concentration exceeded 5 µeq L-1, when the mean DOC:DON ratio fell below an approximate value of 25. Five other large loch sites (LLS) with multiple subcatchments were used to test these relationships and for four of these mostly heathland sites the predicted NO3 - concentrations closely matched measured values. At the fifth site, where most subcatchments were forested, the deposition function and DOC:DON ratios gave conflicting predictions and both methods generally underestimated measured NO3 - concentrations. If the capacity of these catchments to retain deposited N is determined by C supply then many upland catchments in the UK may experience increasing NO3 - concentrations in runoff in the future at current or increased levels of N deposition. 相似文献
4.
Fenn M. E. de Bauer L. I. Quevedo-Nolasco A. Rodriguez-Frausto C. 《Water, air, and soil pollution》1999,113(1-4):155-174
Mexico City experiences some of the most severe air pollution in the world. Ozone injury has been documented in sensitive tree species in urban and forested areas in the Valley of Mexico. However, little is known of the levels of other atmospheric pollutants and their ecological effects on forests in the Valley of Mexico. In this study bulk throughfall deposition of inorganic nitrogen (N) and sulfur (S) was measured for one year at a forested site upwind (east) and downwind (southwest) of Mexico City. Edaphic and plant (Pinus hartwegii Lindl.) indicators of N and S nutrient status were also measured. Streamwater NO3 - and SO4 2- concentrations were also determined as an indicator of watershed-level N and S loss. Annual bulk throughfall deposition of inorganic N and S at the high-pollution forested site 23 km southwest of Mexico City (Desierto de los Leones National Park; DL) was 18.5 and 20.4 kg ha-1. Values for N and S deposition at Zoquiapan (ZOQ), a relatively low-pollution site 53 km east of Mexico City, were 5.5 and 8.8 kg ha-1 yr-1. Foliar concentrations of N, foliar N:P and C:N ratios, extractable soil NO3 -, and streamwater NO3 - concentrations indicate that the forest at DL is N enriched, possibly as a result of chronic N deposition. Sulfur concentrations in current-year foliage were also slightly greater at DL than at ZOQ, but S concentrations in one-year-old foliage were not statistically different between the two sites. Streamwater concentrations of NO3 - ranged from 0.8 to 44.6 μEq L-1 at DL compared to 0.0 to 11.3 μEq L-1 at ZOQ. In summary, these findings support the hypothesis that elevated N deposition at DL has increased the level of available N, increased the N status of P. hartwegii, and resulted in export of excess N as NO3 - in streamwater. 相似文献
5.
Based on studies of high-elevation, Sierra Nevada catchments during the period from 1983 through 1996, we describe temporal variations in the concentrations of NO3 - and SO4 2- in surface waters. During snowmelt, some catchments had a pattern of NO3 - increase to a plateau between the start of snowmelt and some weeks before runoff peaked, and a decline as runoff increased to its maximum. In other catchments, NO3 - concentrations peaked during the autumn and winter. Long-term trends in surface water chemistry were evident in only two catchments: an increase in SO4 2- concentrations in surface waters of the Ruby Lake basin, and a lowering of annual maxima and minima of NO3 - concentrations at Emerald Lake. From October 1987 through April 1994, SO4 2- concentrations increased from about 6 µeq L-1 to about 12 µeq L-1 in Ruby Lake, and in Emerald Lake, NO3 - maxima declined by 25-50 %. 相似文献
6.
Jérôme Molénat Patrick Durand Chantal Gascuel-Odoux Philippe Davy Gérard Gruau 《Water, air, and soil pollution》2002,133(1-4):161-183
In French Brittany, water pollution with nitrate due tointensive agriculture has become one of the major environmentalconcerns. In this article, the nitrate, sulfate and chlorideconcentrations from the groundwater and the stream of a first-order agricultural watershed, are analyzed to infer the mechanisms responsible for the distribution and transfer of nitrate within the watershed. The aquifer is constituted by three layers: the thin soil cover, the weathered shale and thefissured shale. The weathered shale groundwater appears to bea large reservoir of nitrate in the watershed. Indeed the amount of nitrate is estimated at about 450 kg N ha-1, 5 to 9 times the total annual nitrate flux in the stream. In the upslope zones, this groundwater exhibited high nitrate concentrations (up to 138.4±10.5 mg NO3 - L-1), which decreased along the flow paths towards the stream (77.1±13.8 mg NO3 - L-1). Unlike nitrate, sulfate concentrations showed an increase from uphillto downhill (from 6.1±0.8 to 12.5±5.4 mg SO4 2- L-1) with little change in chloride concentrations. These patterns are presumed to result from upward flows from fissured shale groundwater where denitrification by oxidation of pyrite occurs with sulfate as end product. A scheme of nitrate transfer is proposed where stream discharge would result from the mixing of three end members which are: uphill weathered groundwater, deep groundwater and water in the uppermost soil horizons ofthe bottomlands. Temporal variability of nitrate concentrationsin base flow reflects changes in the relative contribution of each end member. 相似文献
7.
8.
Fisher T.R. Lee K.-Y. Berndt H. Benitez J.A. Norton M.M. 《Water, air, and soil pollution》1998,105(1-2):387-397
The Choptank River basin is a coastal plain catchment dominated by agriculture (52% of land use). We summarize an 11 year data set of discharge and chemistry from a gauged subbasin. Discharge exhibited seasonal variations driven by seasonal evapotranspiration. There were double seasonal maxima of pH, NH4 +, NO3 -, total N, Fe, and total P concentrations in late spring and fall as the saturated zone rose and fell within the soil. Significant interannual variability in discharge was the result of rainfall variation. There were positive nterannual trends in NO3 - concentrations and negative interannual trends in NH4 + and PO4 3- concentrations. These data were combined to estimate N and P export coefficients of 3-11 kg N ha-1 yr-1 and 0.14-0.66 kg P ha-1 yr-1, driven primarily by interannual variations in discharge. These export coefficients are low compared to other coastal plain watersheds dominated by agriculture and may be responsible for the small anthropogenic effects in the Choptank estuary compared to other Chesapeake drainages. 相似文献
9.
Elmi Abdirashid A. Madramootoo C. Egeh Mohamud Hamel C. 《Water, air, and soil pollution》2004,151(1-4):117-134
Nitrate-N (NO3 --N) pollution of water resources is a widely recognized problem. Water and nitrogen fertilizer are the two most important factors affecting NO3 --N movement to surface and groundwater. Field trials were conducted from 1998 to 2000 growing seasons to investigate the combined impacts of water table management (WTM) and N fertilization rate on NO3 --N concentration in the soil profile and in drain discharge. There were two water table treatments: free drainage (FD) with open drains at a 1.0 m depth from the soil surface and subirrigation (SI) with a target water table depth of 0.6 m below the soil surface, and two N fertilizer rates: 120 kg N ha-1 (N120) and 200 kg N ha-1 (N200) in a split-plot design. Compared to FD, SI reducedNO3 --N concentration in the soil by up to 50% averaged over the two N rates. Concentrations of NO3 --N in drainage water fromSI plots were lower than those from FD by 55 to 73%. These findings suggest that SI can be used as a means of reducing soil NO3 --N pollution and drainage water NO3 --N concentrations. 相似文献
10.
中国太湖地区稻麦轮作农田硝态氮动态与氮素平衡 总被引：1，自引：0，他引：1
Nitrate-nitrogen (NO 3--N) dynamics and nitrogen (N) budgets in rice (Oryza sativa L.)-wheat (Triticum aestivum L.) rotations in the Taihu Lake region of China were studied to compare the effects of N fertilizer management over a two-year period. The experiment included four N rates for rice and wheat, respectively: N1 (125 and 94 kg N ha-1 ), N2 (225 and 169 kg N ha-1 ), N3 (325 and 244 kg N ha-1 ), and N0 (0 kg N ha-1 ). The results showed that an overlying water layer during the rice growing seasons contributed to moderate concentrations of NO 3--N in sampled waters and the concentrations of NO 3--N only showed a rising trend during the field drying stage. The NO 3--N concentrations in leachates during the wheat seasons were much higher than those during the rice seasons, particularly in the wheat seedling stage. In the wheat seedling stage, the NO 3--N concentrations of leachates were significantly higher in N treatments than in N0 treatment and increased with increasing N rates. As the NO 3--N content (below 2 mg N L-1 ) at a depth of 80 cm during the rice-wheat rotations did not respond to the applied N rates, the high levels of NO 3--N in the groundwater of paddy fields might not be directly related to NO 3--N leaching. Crop growth trends were closely related to variations of NO 3--N in leachates. A reduction in N application rate, especially in the earlier stages of crop growth, and synchronization of the peak of N uptake by the crop with N fertilizer application are key measures to reduce N loss. Above-ground biomass for rice and wheat increased significantly with increasing N rate, but there was no significant difference between N2 and N3. Increasing N rates to the levels greater than N2 not only decreased N use efficiency, but also significantly increased N loss. After two cycles of rice-wheat rotations, the apparent N losses of N1, N2 and N3 amounted to 234, 366 and 579 kg N ha-1 , respectively. With an increase of N rate from N0 to N3, the percentage of N uptake in total N inputs decreased from 63.9% to 46.9%. The apparent N losses during the rice seasons were higher than those during the wheat seasons and were related to precipitation; therefore, the application of fertilizer should take into account climate conditions and avoid application before heavy rainfall. 相似文献
11.
Fertilizers applied to turfgrass may pose a threat to surface and groundwater quality, and hence, a study was carried out to evaluate the fate of fertilizer applied to turfgrass of the Clearwater Bay Golf and Country Club in Hong Kong. Lysimeters with reconstituted soils collected from fairways and greens with Bermudagrass (Cynodon dactylon) growing in the surface were used to evaluate the leaching loss of nitrate (NO3 -), ammonium (NH4 +), and phosphate (PO4 3-) for 22 weeks under greenhouse condition. Both soils received a slow release fertilizer at an application rate of 25 (low) or 50 (high) kg N ha-1, and an application frequency of monthly and fortnightly for fairways and greens, respectively, simulating the fertilizer application strategy of the golf course. Both low and high fertilizer application rate supported the same amount of biomass production for each soil type. Breakthrough of NO3 - occurred only in greens after 11 weeks of leaching, but the total amount of NO3 - leached did not differ significantly for the two different fertilizer application rates. The continued addition of fertilizer to greens resulted in a final leachate NO3 - concentration exceeding 45 mg L-1, while fairways maintained a concentration below 5 mg L-1. Also PO4 3- concentration in leachate of greens exceeded the surface water standard of 0.3 mg L-1. The results of the lysimeter study showed that the current application rate on greens would create adverse environmental impacts on the surface water and groundwater due to leaching loss of PO4 3 - and NO3 -. 相似文献
12.
An Estimation of the Nitrogen and Phosphorus Loading by Wet Deposition over Lake Maracaibo,Venezuela
Morales J. A. Albornoz A. Socorro E. Morillo A. 《Water, air, and soil pollution》2001,128(3-4):207-221
In order to make an estimation of thewet deposition levels of the major nitrogen compoundsin Lake Maracaibo system, the precipitation wascollected by events at five sites located on shorearound the Lake from 1991 to 1994. Also the phosphorusconcentrations were determined in rain samples. RainpHs averaged about 5 to 6. NH4 + levels weresignificantly higher (up to 1.44 mg L-1NH4-N) than NO3 -plus NO2 -ions which resulted in the highest pHs values in thestrait Maracaibo. The strait is the nearest zone toAmmonia Plant located upwind at the TablazoPetrochemical Complex. At the strait, theinorganic-nitrogen ((NH4 + NO3 +NO2)-N) concentrations were greater than organicnitrogen levels, but at the other sites were lower.Phosphorus levels were low, ranging from undetectableto 1.5 mg L-1; organic-P was estimated to accountfor about 40% of total-P. Total mean nitrogen wetdepositions were 6.93 kg ha-1 yr-1 (≈59% asNH4-N) at the strait and 9.85–16.84 kg ha-1yr-1 (≈55% as organic-N) around the lakeshore.Inorganic and organic nitrogen account for about equalportions of the total nitrogen loading. These amountsrepresents ≈24% of the annual total-N inputsby the tributary rivers to the lake and aresubstantially higher than those reported in the shoreof Lake Valencia (north-central part of Venezuela) andother tropical areas. The contribution ofprecipitation to P in lake is very small; ≈0.6 kg ha-1 of total-P are added annually. The N and Pinputs were greater than the sewage contributions. Themean molar ratio N/P is ≈22 at the straitsite whilst at lake sites the N/P ratio isconsistently >22 (about 35～1 to 100～1). The results of this preliminary study show that the atmosphere represents a significant factor for the total nitrogen loading to Lake Maracaibo system. 相似文献
13.
Gunnar Wiklander Gertrud Nordlander Rune Andersson 《Water, air, and soil pollution》1991,55(3-4):263-282
Water balance and leaching of plant nutrients, with special reference to N, were described for a 46-ha catchment consisting mainly of coniferous forest (one third of it clear-cut) during the period January 1982-August 1988. The atmospheric N load in this region is high compared with most other parts of Scandinavia. On average, annual N leaching amounted to 9.5 kg ha?1 in the form of NO3-N (83%), org-N (15%) and NH4-N (2%). The highest monthly rate of N transport observed was 3.9 kg ha?1. The NO3-N levels in groundwater in the 60-yr-old coniferous stand ranged from 0.5 to 3.1 mg L?1. The effect of clear-cutting on groundwater-NO3-N levels lasted 4 yr. The highest annual NO3-N transport from the clear-cut area observed was 18 kg ha?1. The groundwater in the spruce forest was very acidic (pH=4.3) in contrast to the stream water (pH=6.3). The relatively higher pH-value of the stream water was probably a result of chemical and biological processes occurring in the highly humified, periodically waterlogged peat soil (alder swamp) in the vicinity of the small stream. 相似文献
14.
硝酸盐反射仪和SPAD法对玉米氮素营养诊断的比较 总被引：1，自引：0，他引：1
精准的营养诊断是了解作物氮素营养及推荐施肥的基础。本文在田间滴灌条件下利用SPAD叶绿素仪(SPAD-502 Plus)和硝酸盐反射仪(RQ flex10)两种诊断方法对玉米关键生育时期的氮素营养诊断进行研究,旨在筛选出适宜的诊断方法,并依据诊断值建立滴灌玉米不同生育时期的施肥模型。试验设置0 kg(N)·hm~(-2)(N0)、225 kg(N)·hm~(-2)(N225)、330 kg(N)·hm~(-2)(N330)、435 kg(N)·hm~(-2)(N435)和540 kg(N)·hm~(-2)(N540)5个施氮水平,在不同生育时期测定了玉米叶片SPAD值和叶鞘NO_3~-含量,并分别与施氮量、植株全氮含量、产量进行方程拟合,比较两种诊断方法对玉米氮素营养的响应。研究结果表明:1)玉米叶片SPAD值和叶鞘NO_3~-含量均随施氮量的增加而显著升高,且在拔节期对施氮量的响应最敏感。叶鞘NO_3~-含量对施氮量变化的响应较SPAD值大,其与施氮量及玉米产量的拟合度均高于SPAD值,说明硝酸盐反射仪法对滴灌玉米氮素丰缺的反应更灵敏。2)玉米全氮含量与叶片SPAD值呈显著线性关系,而与叶鞘NO_3~-含量则以线性加平台表示。当叶鞘NO_3~-含量小于186 mg·L~(-1)时,植株全氮与NO_3~-间呈显著线性相关;当叶鞘NO_3~-含量大于186 mg·L~(-1)时,植株全氮随NO_3~-含量增加趋于不变。3)本农作区滴灌玉米最佳经济施氮量为402.5 kg·hm~(-2),对应的玉米产量为17 049 kg·hm~(-2)。玉米拔节期、抽雄吐丝期和灌浆期的临界叶鞘NO_3~-含量分别为729.3 mg·L~(-1)、536 mg·L~(-1)和81.2 mg·L~(-1)。SPAD叶绿素仪和硝酸盐反射仪均可对滴灌玉米进行氮素营养诊断,但硝酸盐速测值能更敏感地反映氮素丰缺状况,基于硝酸盐反射法进行作物氮素营养诊断及推荐施肥具有较好的准确性与适用性。 相似文献
15.
Hagedorn Frank Schleppi Patrick Bucher Jürg Flühler Hannes 《Water, air, and soil pollution》2001,129(1-4):119-142
The responses of nitrogen transformations and nitrate (NO_3 -) leaching to experimentally increased N deposition were studied in forested sub-catchments (1500 m2) with Gleysols in Central Switzerland. The aim was toinvestigate whether the increase in NO3 - leaching,due to elevated N deposition, was hydrologically driven orresulted from N saturation of the forest ecosystem.Three years of continuous N addition at a rate of 30 kgNH4NO3-N ha-1 yr-1 had no effects on bulksoil N, on microbial biomass N, on K2SO4-extractableN concentrations in the soil, and on net nitrification rates.In contrast, N losses from the ecosystem through denitrification and NO3 - leaching increased significantly. Nitrate leaching was 4 kg N ha-1yr-1at an ambient N deposition of 18 kg N ha-1 yr-1.Leaching of NO3 - at elevated N deposition was 8 kg Nha-1 yr-1. Highest NO3 - leaching occurredduring snowmelt. Ammonium was effectively retained within theuppermost centimetres of the soil as shown by the absence ofNH4 + in the soil solution collected with microsuction cups. Quantifying the N fluxes indicated that 80% ofthe added N were retained in the forest ecosystem.Discharge and NO3 - concentrations of the outflow from the sub-catchments responded to rainfall within 30 min. The water chemistry of the sub-catchment outflow showed thatduring storms, a large part of the runoff from this Gleysol derived from precipitation and from water which had interactedonly with the topsoil. This suggests a dominance of near-surface flow and/or preferential transport through this soil. The contact time of the water with the soil matrix wassufficient to retain NH4 +, but insufficient for a complete retention of NO3 -. At this site with soilsclose to water saturation, the increase in NO3 - leaching by 4 kg N ha-1 yr-1 through elevated N inputsappeared to be due to the bypassing of the soil and the rootsystem rather than to a soil-internal N surplus. 相似文献
16.
A 5-year study was conducted to monitor patterns of NO3 - accumulation following the addition of plant residues of varying C:N ratios to the soil surface, to determine whether the availability of NO3 - following these applications would be timely and sufficient for typical annual crop uptake. Microbial respiration was measured in the last 3 years of the study to investigate how microbial activity was related to treatment differences in NO3 - accumulation. Treatments included: hairy vetch (Vicia villosa Roth) cut at mid-bloom; wheat (Triticum aestivum L.) straw applied at 4 Mg ha-1; vetch with 4 Mg ha-1 wheat straw; and a bare ground control. Soil NO3 - and respiration rates were correspondingly high for the 3–4 weeks following residue placement. Peak NO3 --N accumulation in vetch treatments occurred between 25 June and 10 July and ranged from 100 to 168 kg ha-1, with an average of 140 kg NO3 ?-N ha-1. Nitrate was sufficient and timely enough to meet most summer annual crop needs in the region. Over 5 years, peak NO3 ?-N was approximately 100 kg ha-1 higher in vetch than non-vetch treatments and roughly twice as high at 0–5 cm than at 5–20 cm. The addition of wheat straw caused a reduction of approximately 20% NO3 --N throughout the season as compared to vetch alone. 相似文献
17.
Norman E. Peters 《Water, air, and soil pollution》1991,59(3-4):201-215
The chemistry of precipitation, throughfall, soil water, ground water, and surface water was evaluated in two forested lake-watersheds over a 4-yr period to assess factors controlling Cl? cycling. Results indicate that Cl? cycling in these watersheds is more complex than the generally held view of the rapid transport of atmospherically derived Cl? through the excosystem. The annual throughfall Cl? flux for individual species in the northern hardwood forest was 2 to 5 times that of precipitation (56 eq ha?1), whereas the Na+ throughfall flux, in general, was similar to the precipitation flux. Concentrations of soil-water Cl? sampled from ceramic tension lysimeters at 20 cm below land surface generally exceeded the Na+ concentrations and averaged 31 μeq L?1, the highest of any waters sampled in the watersheds, except throughfall under red spruce which averaged 34 μeq L?1. Chloride was concentrated prior to storms and mobilized rapidly during storms as suggested by increases in streamwater Cl? concentrations with increasing flow. Major sources of Cl? in both watersheds are the forest floor and hornblende weathering in the soils and till. In the Panther Lake watershed, which contains mainly thick deposits of till (>3 m), hornblende weathering results in a net Cl? flux 3 times greater than that in the Woods Lake watershed, which contains mainly thin deposits of till. The estimated accumulation rate of Cl? in the biomass of the two watersheds was comparable to the precipitation Cl? flux. 相似文献
18.
R. Nieder E. Neugebauer A. Willenbockel K. C. Kersebaum J. Richter 《Biology and Fertility of Soils》1996,22(1-2):179-183
In 1991, field experiments on loess (with winter wheat) and sandy soils (with summer barley) were conducted to study N dynamics in the microbial biomass and non-exchangeable NH
inf4
sup+
. The measurements showed a mass change in microbial N, with a maximum increase of 100 kg N ha-1 30 cm-1 from March to July in the loess soil, and a change for only 1 month (May) in the sandy soil. Plots treated with conventional levels of N fertilizer (213 kg N ha-1 on a loess soil to winter wheat and 130 kg ha-1 on the sandy soil to summer barley), reduced levels of N (83% and 62% of the conventional N application), or no N showed no consistent fertilizer N effect on microbial biomass N. From March to July, non-exchangeable NH
inf4
sup+
in loess soils under winter wheat decreased by 110 kg N ha-1 30 cm-1 in conventionally fertilized plots and by 200 kg N ha-1 30 cm-1 in a plot with no N fertilizer. After harvest, the pool of non-exchangeable NH
inf4
sup+
increased due to increasing mineral N concentrations in the soil. 相似文献
19.
SULLIVAN T. J. EILERS J. M. COSBY B. J. VACHÉ K. B. 《Water, air, and soil pollution》1997,95(1-4):313-336
Assessments of the aquatic effects of acidic deposition have focused on sulfur, as have recent efforts to control the emissions of acidifying compounds. Nitrogen dynamics were excluded from most acidic deposition modeling studies because it was believed that terrestrial ecosystems strongly retain N and because modeling N is a more formidable task than modeling S due to the influence of complex biological processes on N cycling. Re-examination of available data for the Adirondack Mountains of New York suggests that N deposition may be contributing to both chronic and episodic acidification of freshwaters to a greater extent than is generally believed. Previous research concluded that N has played a limited role in acidification processes in these lakes, based on regional averages of chronic chemistry. However, it is now known that historic acidification responses have been spatially variable within the Adirondack Mountains and that the declines in lakewater pH have been less than previously believed. Lakewater NO3 - concentrations are commonly in the range of 5 to 25 μeq L-1 on a chronic basis in portions of the Adirondack region that have experienced significant chronic acidification. These NO3 - concentrations correspond in magnitude to inferred historical acidification. Furthermore, the relative importance of NO3 - as an agent of acidification increases dramatically during snowmelt when conditions are most toxic to fish. The consequence of not addressing N in formulating acidification recovery strategies for the Adirondacks includes the likelihood that we will overestimate the response of surface water to the mandated sulfur emissions reductions. 相似文献
20.
保护地蔬菜轮作体系中两种不同复合肥对产量的影响及其氮素动态特征 总被引：1，自引：1，他引：1
Yield and N uptake of tomato (Lycopersicum esculentum Mill.) and pepper (Capsicum annuum L.) crops in five successive rotations receiving two compound fertilizers (12-12-17 and 21-8-11 N-P2O5-K2O) were studied to determine 1) crop responses, 2) dynamics of NO3-N and NH4-N in different soil layers, 3) N balance and 4) system-level N efficiencies. Five treatments (2 fertilizers, 2 fertilizer rates and a control), each with three replicates, were arranged in the study. The higher N fertilizer rate, 300 kg N ha-1 (versus 150 kg N ha-1), returned higher vegetable fruit yields and total aboveground N uptake with the largest crop responses occurring for the low-N fertilizer (12-12-17) applied at 300 kg N ha-1 rather than with the high-N fertilizer (21-8-11). Ammonium-N in the top 90 cm of the soil profile declined during the experiment, while nitrate-N remained at a similar level throughout the experiment with the lower rate of fertilizer N. At the higher rate of N fertilizer there was a continuous NO3-N accumulation of over 800 kg N ha-1. About 200 kg N ha-1 was applied with irrigation to each crop using NO3-contaminated groundwater. In general, about 50% of the total N input was recovered from all treatments. Pepper, relative to tomato, used N more efficiently with smaller N losses, but the crops utilized less than 29% of the fertilizer N over the two and a half-year period. Local agricultural practices maintained high residual soil nutrient status. Thus, optimization of irrigation is required to minimize nitrate leaching and maximize crop N recovery. 相似文献