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1.
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   

2.
Forested headwater streams in the Catskill Mountains of New York show significant among-catchment variability in mean annual nitrate (NO3 -) concentrations. Large contributions from deep groundwater with high NO3 -concentrations have been invoked to explain high NO3 -concentrations in stream water during the growing season. To determine whether variable contributions of groundwater couldexplain among-catchment differences in streamwater, we measuredNO3 - concentrations in 58 groundwater seeps distributed across six catchments known to have different annual average streamwater concentrations. Seeps were identified based on release from bedrock fractures and beddingplanes and had consistently lower temperatures than adjacentstreamwaters. Nitrate concentrations in seeps ranged from neardetection limits (0.005 mg NO3 --N/L) to 0.75 mg NO3 --N/L. Within individual catchments, groundwaterresidence time does not seem to strongly affect NO3 -concentrations because in three out of four catchments therewere non-significant correlations between seep silica (SiO2) concentrations, a proxy for residence time, andseep NO3 - concentrations. Across catchments, therewas a significant but weak negative relationship betweenNO3 - and SiO2 concentrations. The large rangein NO3 - concentrations of seeps across catchmentssuggests: 1) the principal process generating among-catchmentdifferences in streamwater NO3 - concentrations mustinfluence water before it enters the groundwater flow system and 2) this process must act at large spatial scales becauseamong-catchment variability is much greater than intra-catchmentvariability. Differences in the quantity of groundwater contribution to stream baseflow are not sufficient to account for differences in streamwater NO3 - concentrationsamong catchments in the Catskill Mountains.  相似文献   

3.
成都平原农区地下水中NO3--N含量变化规律研究   总被引：11，自引：0，他引：11       下载免费PDF全文
采用硝酸根电极法对成都平原温江县天府乡农区田间和水井的地下水NO-3 N含量进行了一年多的连续测定 ,探讨了该农区地下水中NO-3 N的变化规律和氮肥用量的影响。结果表明 :(1)田间地下水NO-3 N含量周年变化规律是冬春枯水季较高 ,且变幅较大 (0 3 6～ 2 62mgL- 1) ,平均值为 2 59mgL- 1;夏秋丰水季较低 ,且变幅较小 (0 84～ 5 48mgL- 1) ,平均值为 1 10mgL- 1。 (2 )前作麦季氮肥施用量 ,对稻季地下水中NO-3 N含量有明显影响 ,当前作施纯氮达 3 75kghm- 2 时 ,稻季地下水NO-3 N含量最高达 3 4 6mgL- 1,其平均值为 17 97mgL- 1,是施纯氮 150kghm- 2 平均值 1 3 0mgL- 1的 13 7倍。 (3 )井水中NO-3 N含量变化幅度为 0 14～ 16 53mgL- 1,3口井水平均值分别为 2 54、3 60、6 52mgL- 1,未超出我国生活饮用水卫生标准 ,但明显高于灌溉水NO-3 N含量的平均值 1 81mgL- 1。 (4)地下水位的高低与井水中NO-3 N含量没有线性关系  相似文献   

4.
大孔隙分布对坡地产汇流及溶质运移的影响   总被引：2，自引：0，他引：2  
以室内土槽为平台,采用人工模拟降雨试验,研究了粉砂壤土中两种不同大孔隙分布情况下,土槽中土壤含水量、坡面流速、地面径流、地下径流及溶质运移的变化。结果表明,相对于面大孔隙度为19%,容积大孔隙度为0.095%的未加密型的土槽,面大孔隙度为57%,容积大孔隙度为0.285%的大孔隙加密型土槽中各层土壤含水量增加幅度、平均坡面流速及地面径流量相对偏小,地下流出现时间较早且径流量较大,地面径流中溴离子、铵根离子浓度、硝酸根离子浓度偏小。在地下水出流前期,大孔隙加密型土槽中的铵根离子浓度和浓度变化幅度都偏小,但溴离子、硝酸根离子浓度则偏大。  相似文献   

5.
To determine whether NO3 ? concentration pulses in surface water in early spring snowmelt discharge are due to atmospheric NO3 ?, we analyzed stream δ15N-NO3 ? and δ18O-NO3 ? values between February and June of 2001 and 2002 and compared them to those of throughfall, bulk precipitation, snow, and groundwater. Stream total Al, DOC and Si concentrations were used to indicate preferential water flow through the forest floor, mineral soil, and ground water. The study was conducted in a 135-ha subcatchment of the Arbutus Watershed in the Huntington Wildlife Forest in the Adirondack Region of New York State, U.S.A. Stream discharge in 2001 increased from 0.6 before to 32.4 mm day?1 during snowmelt, and element concentrations increased from 33 to 71 μmol L?1 for NO3 ?, 3 to 9 μmol L?1 for total Al, and 330 to 570 μmol L?1 for DOC. Discharge in 2002 was variable, with a maximum of 30 mm day?1 during snowmelt. The highest NO3 ?, Al, and DOC concentrations were 52, 10, and 630 μmol L?1, respectively, and dissolved Si decreased from 148 μmol L?1 before to 96 μmol L?1 during snowmelt. Values of δ15N and δ18O of NO3 ? in stream water were similar in both years. Stream water, atmospherically-derived solutions, and groundwaters had overlapping δ15N-NO3 ? values. In stream and ground water, δ18O-NO3 ? values ranged from +5.9 to +12.9‰ and were significantly lower than the +58.3 to +78.7‰ values in atmospheric solutions. Values of δ18O-NO3 ? indicating nitrification, increase in Al and DOC, and decrease in dissolved Si concentrations indicating water flow through the soil suggested a dilution of groundwater NO3 ? by increasing contributions of forest floor and mineral soil NO3 ? during snowmelt.  相似文献   

6.
The chemical composition of snowmelt, groundwater, and streamwater was monitored during the spring of 1991 and 1992 in a 200-ha subalpine catchment on the western flank of the Rocky Mountains near Steamboat Springs, Colorado. Most of the snowmelt occurred during a one-month period annually that began in mid-May 1991 and mid-April 1992. The average water quality characteristics of individual sampling sites (meltwater, streamwater, and groundwater) were similar in 1991 and 1992. The major ions in meltwater were differentially eluted from the snowpack, and meltwater was dominated by Ca2+, SO 4 2? , and NO 3 ? . Groundwater and streamwater were dominated by weathering products, including Ca2+, HCO 3 ? (measured as alkalinity), and SiO2, and their concentrations decreased as snowmelt progressed. One well had extremely high NO 3 ? . concentrations, which were balanced by Ca2+ concentrations. For this well, hydrogen ion was hypothesized to be generated from nitrification in overlying soils, and subsequently exchanged with other cations, particularly Ca2+. Solute concentrations in streamwater also decreased as snowmelt progressed. Variations in groundwater levels and solute concentrations indicate that most of the meltwater traveled through the surficial materials. A mass balance for 1992 indicated that the watershed retained H+, NH 4 + , NO 3 ? , SO 4 2? and Cl? and was the primary source of base cations and other weathering products. Proportionally more SO 4 2? was deposited with the unusually high summer rainfall in 1992 compared to that released from snowmelt, whereas NO 3 ? was higher in snowmelt and Cl? was the same. The sum of snowmelt and rainfall could account for greater than 90% of the H+ and NH 4 + retained by the watershed and greater than 50% of the NO 3 ? .  相似文献   

7.
As nitrogen (N) fertilizer-use efficiency rarely exceeds 50% in most agricultural systems, the potential leaching of N to the groundwater, particularly under irrigated conditions, has economic, health, and environmental implications. Research in the Akarsu irrigation district in the Lower Seyhan Plain in southern Turkey sought to determine spatial and temporal variability of groundwater (GW) nitrate (NO3) concentrations in 2007–2008. Shallow groundwater observation wells 3 m deep were installed at different locations to represent the whole irrigation district. Groundwater samples were collected (February, April, July, October) and analyzed for ammonium (NH4) and NO3 concentrations. Because NH4 values were negligible, only NO3 data were processed to determine spatial and temporal variability and then used to develop regional NO3 maps using geographic information systems. Groundwater NO3 concentrations ranged between 0.17 and 55.96 mg L–1 during the 2 years, only exceeding the critical 50 mg L–1 concentration in 1% of the area sampled. The areal mean of NO3 concentration was greatest in February, indicating a potential N leaching of unused N from the early season with intensive rainfall, especially in wheat-growing areas. Groundwater NO3 concentrations decreased after February; however, during the peak irrigation season in July, NO3 was relatively low because of crop uptake during spring and summer. In about half the area, groundwater NO3 concentrations ranged between 20 and 50 mg L–1 and were thus marginal relative to the critical pollution level. As N fertilizer use will continue to increase, especially with the expanded irrigation that is now occurring in the Mediterranean region, regular monitoring of groundwater NO3 is advisable under such conditions.  相似文献   

8.
Ion concentrations in water collected within a forest of sugar maple and yellow birch at the Turkey Lakes Watershed near Sault Ste. Marie, Ontario were examined from 1982 to 1984 to determine sources of acidity and the extent of cation leaching from forest floor horizons. Volume-weighted concentrations and ion fluxes in throughfall and forest-floor percolate during the growing and dormant seasons were calculated. Hydrogen ion content of the forest-floor percolate decreased in relation to that of throughfall in the dormant season and increased in the growing season. Hydrogen ion deposition in throughfall could account for 100% of the flux of H+ through the forest floor in the dormant period, and 40% of the flux during the growing season. In forest-floor percolate, Ca2+ concentrations were positively correlated with those of SO4 2-, NO3 - and organic anions during both dormant and growing seasons. Sources of NO3 - and organic anions within the ecosystem and major external inputs of NO3 - and SO4 2- were critical factors that influenced cation mobility in the forest floor.  相似文献   

9.
Harriman  R.  Curtis  C.  Edwards  A.C. 《Water, air, and soil pollution》1998,105(1-2):193-203
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   

10.
Nitrate (NO-3) and nitrite (NO2-) leaching threatens groundwater quality.Soil C:N ratio,i.e.,the ratio of soil organic carbon to total nitrogen,affects mineralization,nitrification,and denitrification;however,its mechanism for driving soil NO-3 and NO-2 accumulation and leaching remains unclear.Here,a field investigation in a fluvo-aquic soil and a soil column experiment were performed to explore the relation...  相似文献   

11.
Abstract

Successful implementation of vegetative buffers requires inclusion of plant species that facilitate rapid dissipation of deposited contaminants before they have a chance to be transported in surface runoff or to shallow groundwater. Thirty‐six field lysimeters with six different ground covers [bare ground, orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), smooth bromegrass (Bromus inermis Leyss.), timothy (Phleum pratense L.), and switchgrass (Panicum virgatum L.)] were established to evaluate the ability of grasses to reduce nutrient levels in soils and shallow groundwater. Nitrate (NO3 ?) and orthophosphate (PO4 3?) were uniformly applied to each lysimeter. In addition, half of the lysimeters received an application of atrazine, and the other half received isoxaflutole (Balance?) at levels indicative of surface runoff from cropland. The leachate from each lysimeter was collected after major rainfall events during a 25‐day period, and soil was collected from each lysimeter at the end of the 25‐day period. Water samples were analyzed for NO3‐N and PO4‐P, and soil samples were analyzed for NO3‐N. Grass treatments reduced NO3‐N levels in leachate by 74.5 to 99.7% compared to the bare ground control, but timothy was significantly less effective at reducing NO3‐N leaching than the other grasses. Grass treatments reduced residual soil NO3‐N levels by 40.9 to 91.2% compared to the control, with tall fescue, smooth bromegrass, and switchgrass having the lowest residual levels. Switchgrass decreased PO4‐P leaching to the greatest extent, reducing it by 60.0 to 74.2% compared to the control. The ability of the forage grasses to reduce nutrient levels in soil or shallow groundwater were not significant between herbicide treatments. Quantification of microbial NO3 ? dissipation rates in soil suggested that denitrification was greatest in switchgrass, smooth bromegrass, and tall fescue treatments. The overall performance of these three grasses indicated that they are the most suitable for use in vegetative buffers because of their superior ability to dissipate soil NO3 ? and reduce nutrient transport to shallow groundwater.  相似文献   

12.
为探索太湖流域水网地区农田土壤氮素通过地表径流与耕层渗漏的流失特征及其影响因素,在浙江省嘉兴市、上海市的松江县和青浦县,选择稻田、种植年限短的菜地、种植年限长的菜地3种类型农田,采用原位模拟降雨,研究渗漏与地表径流方式下的农田氮素流失量、流失形态特征,以及土壤养分含量对氮素流失的影响。结果表明,3种农田在地表径流方式下农田总氮流失量差异不显著;渗漏方式下种植年限长的菜地和种植年限短的菜地总氮流失量差异也不显著。渗漏方式下总氮流失量显著高于地表径流方式。农田0—5、0—20 cm土壤硝态氮含量分别为31.24~72.9和33.21~71.1 mg/kg时,与渗漏液硝态氮、水溶性总氮、总氮的流失量、流失浓度呈极显著正相关。  相似文献   

13.
华北山前平原农田土壤硝态氮淋失与调控研究   总被引：11，自引：5，他引：6  
本文依托中国科学院栾城农业生态系统试验站小麦-玉米一年两熟长期定位试验, 应用土钻取土和土壤溶液取样器取水的方法, 研究了不同农田管理措施下土壤硝态氮的累积变化, 计算了不同氮肥处理通过根系吸收层的硝态氮淋失通量。结果表明, 小麦-玉米生长季土壤硝态氮累积量和淋失量随着施氮量的增加显著增加, 相同氮肥水平下增施磷、钾肥增加了作物的收获氮量, 施磷肥增加的作物收获氮量最高可达123kg·hm-2·a-1, 施钾肥增加的作物收获氮量最高为31 kg·hm-2·a-1。不同灌溉水平下0~400 cm 土体累积硝态氮随着灌溉量的增加而降低, 控制灌溉(小麦季不灌水, 玉米季灌溉1 水)、非充分灌溉(小麦季灌溉2~3 水, 玉米季按需灌溉)、充分灌溉(小麦季灌溉4~5 水, 玉米季按需灌溉)各处理剖面累积硝态氮量分别为1 698 kg·hm-2、1148 kg·hm-2 和961 kg·hm-2。与非充分灌溉和充分灌溉处理相比, 控制灌溉在100~200 cm 土层硝态氮累积量显著高于其他层次, 2003~2005 年间控制灌溉剖面增加的硝态氮量占施肥总量的23%; 非充分灌溉处理剖面增加的硝态氮量占施肥总量的22%; 充分灌溉处理剖面增加的硝态氮量占施肥总量的47%。免耕措施降低了作物产量, 影响土壤水的运移, 增加了硝态氮的淋失风险。根据作物所需降低氮素投入(N 200 kg·hm-2·a-1), 增施磷、钾肥, 控制灌溉量是减少华北山前平原地区硝态氮淋失, 保护地下水的有效措施。  相似文献   

14.
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   

15.
We used ionic tracers to estimate the volume of old (soil and ground) water interacting with snowmelt in eleven Adirondack, NY watersheds. The contribution of old water varied from 66 to 90%, with no general relationship between old water % and soil depth to till. This approach also discriminated between watershed retention and release of particular ions to lake outlet water during snowmelt. Most watersheds released NO3 ? during snowmelt, in addition to the snowpack NO3 ?. Nitrification of snowpack NH4 + explained part of the additional NO3 ? in lake out outlet water, but some NO3 ? was likely mineralized nitrogen from soil organic matter. All watersheds retained NH4 + as well. Nitrogen release was greatest in the acidic watersheds in the southwestern Adirondacks, a region thought to be impacted by anthropogenic deposition. During snowmelt, Ca2+ and Mg2+ ions (presumably from soil exchange sites) were also released from most watersheds. In watersheds with acidic (minimum pH<4.6) lake outlet water, Al was also released during snowmelt. Thus, lake outlet water acidification during snowmelt was both buffered by cation release, and intensified by NO3 ? release. If the soil exchangeable cation pools were not replenished prior to snowmelt, or NO3 ? mobilization were increased, acidification during snowmelt would intensify.  相似文献   

16.
Lin  N.-H.  Lee  H.-M.  Chang  M.-B. 《Water, air, and soil pollution》1999,113(1-4):241-260
This work investigated the characteristics of acid precipitation collected in Taipei, Taiwan during 1991–1995 by performing cluster analysis. The extent to which meteorological conditions influence precipitation chemistry was also elucidated. Three potential sources of water-soluble ions in rainwater were identified: seasalt aerosols (Na+, Cl- and Mg2+), anthropogenic pollutants (H+ and NO3 -), and mixing sources associated with sulfate (nss-SO4 2-, NH4 + and Ca2+). As the northeast flow prevailed during the northeast monsoon season, the concentrations of seasalt and sulfate ions in rainwater were significantly high. During that season, a typically high ratio of nss-SO4 2-/NO3 - was also observed, indicating that Taipei might receive foreign pollutants via a long-range transport. In contrast, when the Pacific high dominated the region, nitrate concentration in rainwater was significantly elevated. Also during that period, the ratio of nss-SO4 2-/NO3 - was substantially lower, indicating the prominence of acidic substances contributed by local sources.  相似文献   

17.
Large quantities of the nitrate leaching below the crop root-zone, particularly during the wet season, in the tropical Far North Queensland (FNQ) of Australia, may be entering off and on-site the water bodies. The objectives of this study were to (i) provide quantitative information on NO3-N in the shallow fluctuating groundwater (GW) that develops during the rainy season (January through May) in the Johnstone River Catchment (JRC) of FNQ and (ii) determine whether this NO3-N is potentially transportable to creeks/streams. The NO3-N concentration and GW table heights were monitored, at least at weekly intervals, in 6 piezometers, installed to 8.5–12.0 m depth in 6 different soil types under fertilized sugarcane (Saccharum Officinarum-S) in the JRC during the 1999 rainy season.Depending on the location of piezometers on the landscape and time of water sampling, the GW table fluctuated between from 1.5 to 11.5 m abovethe piezometer bottom. The NO3-N concentration in the fluctuating GW also showed spatio-temporal dynamics and it ranged from 0.60 to 3.70 mg L-1. The NO3-N adsorbed at anion exchanges sites, up to 10 m depth, ranged from 154 to 3956 kg ha-1, compared with 21 kgha-1 under rainforest. In the fluctuating GW, the NO3-N concentration increased with increasing GW table height and the NO3-N adsorbed at anion exchange sites (R2 = 0.96). The NO3-N load in the GW ranged from 40 to 110 kg ha-1 and it increased with increasing GW table and GW NO3-N concentration. The estimated N-load in the GW that was discharged into creeks/streams when the GW receded ranged from 21 to 81 kg ha-1. The results provide evidence that a(i) a major proportion of the NO3-N that was leaching below the sugarcane root-zone entered the shallow GW that developed during the rainy season, and (ii) a significant proportion of the NO3-N inthe GW was transported to creeks/streams when the GW table receded.  相似文献   

18.
北京地区潮土表层中NO3--N的转化积累及其淋洗损失   总被引：34，自引：2，他引：34       下载免费PDF全文
本试验利用渗滤池设施，采用化学分析和同位素技术相结合的方法研究了北京地区潮土表层中施用氮肥后ＮＯ３＾－－Ｎ转化积累及其１３０ｃｍ土体的淋洗状况。常规分析结果表明，在春小麦和夏玉米的生育前期可以观察到氮素明显地向ＮＯ３＾－－Ｎ的转化积累，其强度随尿素施用量的增加而明显增加，而尿素、硝铵、硫铵等不同氮肥品种处理之间有差异但大多不显著。同时夏玉米期间转化积累作用比春小麦期间强烈。＾１５Ｎ标记试验结果表明  相似文献   

19.
Variations in sulphate (SO4 2-) concentration of porewater and net SO4 2- mobilization were related to differences in water level fluctuations during wet and dry summers in two conifer swamps located in catchments which differed in till depth and seasonality of groundwater flow. Sulphate depletion at the surface and in 20 cm porewater coincided with anoxia and occurred mainly during the summer when water levels were near the peat surface and water flow rates were low in both catchments. There was an inverse relationship between net SO4 2- mobilization and water level elevation relative to the peat surface, explaining variation in SO4 2- dynamics between the swamps during summer drought periods. Aeration of peat to 40 cm and a large net SO4 2- mobilization (10–70 mg SO4 2- m-2 d-1) occurred during a dry summer in which the water level dropped to 60 cm below the surface in the swamp receiving ephemeral groundwater inputs from shallow tills within the catchment. This resulted in high SO4 2- concentrations in the surface water and porewater (30–50 mg L-1), and elevated SO4 2- concentrations remained through the fall and winter. In contrast, within the swamp located in the catchment with greater till depth (> 1 m), continuous groundwater inputs maintained surface saturation during the dry summer, and SO4 2- mobilization and concentrations of SO4 2- in the pore water during the following fall did not increase. Susceptibility to large water table drawdown and mobilization of accumulated SO4 2- is influenced by the occurrence of ephemeral vs. continuous groundwater inputs to valley swamps during dry summer periods in the Canadian Shield landscape. This study reveals that extrapolation of results of SO4 2- cycling from one wetland to another requires knowledge of the hydrogeology of the catchment in which the wetlands are located.  相似文献   

20.
应重视硝态氮同化过程在降低土壤硝酸盐浓度中的作用   总被引：5，自引：1，他引：4  
程谊  黄蓉  余云飞  王慎强 《土壤学报》2017,54(6):1326-1331
在保证生产力条件下,采取合理的氮肥管理措施降低土壤硝态氮浓度对降低氮污染至关重要。当前,应用硝化抑制剂能够有效延缓铵态氮的硝化速率,进而降低土壤硝态氮淋溶损失和氮氧化物排放,但是其缺点显而易见:促进氨挥发并引起硝化抑制剂污染。好氧条件下,土壤硝态氮净变化量取决于产生(硝化)和消耗(硝态氮同化)的量。但是,一直以来,受微生物优先利用铵态氮这一传统观点的影响,人们普遍认为农田土壤微生物较少利用硝态氮,很大程度上忽视了对硝态氮同化过程的研究。该过程独具优势,它将硝态氮转变为微生物生物量氮进行短期储存并发生再矿化,具有保氮功能且环境友好。加入特定的碳源可以提高硝态氮同化这已是不争的事实,未来应加强硝态氮同化降低土壤硝酸盐累积方面的研究:(1)外源碳影响硝态氮同化的微生物驱动机制是什么?(2)怎样才能操控硝态氮同化和再矿化过程,使得作物氮需求和土壤氮供应相匹配,进而降低氮损失?(3)在碳源充足的条件下,反硝化作用亦会增强,如何才能做到在提高硝态氮同化的同时避免反硝化氮损失?  相似文献   

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