黄土区降水降尘输入农田土壤中的氮素评估

随着人类活动引起大气活性氮的急剧增加,大气氮沉降亦明显增加,由此引发的各生态系统的响应也逐渐表现出来.研究黄土区氮沉降,对农业生态系统的氮素循环与平衡提供一定的数据支持,同时为农民科学合理施肥提供依据,为研究氮沉降的环境生态效应和生物有效性提供科学支撑.用APS-2A型降水降尘自动采样器对陕西杨凌和洛川地区2006～2007年的降水降尘输入氮总量、月动态变化及各形态N的贡献率进行了监测与分析.结果显示杨凌点2006年总降雨量为507.8 mm,总N沉降通量为20.6 kg/(hm2·a),其中N湿沉降通量为19.1 kg/(hm2·a),占93%;降尘输入的N通量为1.5 kg/(hm2·a),占7%.总N沉降通量中NO-3-N为7.3 kg/(hm2·a),占36%.洛川点2006年6月～2007年5月总降雨量为579.5 mm,总N沉降通量为12.7 kg/(hm2·a),其中N湿沉降通量为11.4 kg/(hm2·a),占90%;降尘输入N的通量为1.2 kg/(hm2·a),占10% .总N沉降通量中NO-3-N为8.7kg/(hm2·a),占69%.两个点N沉降通量和氮素形态的差异在很大程度上反映了活性N主要来自人为活动,即农业生产排放的活性N.     

冬麦田臭氧干沉降过程的观测

地表臭氧作为近地层最主要的大气污染物之一,其不断上升的浓度及其对粮食作物的影响受到越来越多的关注.本研究利用微气象学观测方法,探明自然条件下冬麦田的臭氧沉降过程,分析了影响臭氧沉降过程的环境因子.结果表明: 观测期内(小麦生长旺期)臭氧通量均值为-0.35 μg·m^-2·s^-1(负号表示沉降方向指向地面),臭氧沉降平均速率为0.55 cm·s^-1,空气动力学阻力均值为30 s·m^-1,粘性副层阻力均值为257 s·m^-1,冠层阻力均值为163 s·m^-1,且均存在明显的日变化趋势.臭氧沉降阻力大小受摩擦速度、太阳辐射强度、温度和相对湿度等因素的影响.     

Atmospheric deposition to a rural tropical site

Chemical analysis of Na, K, Ca and Mg in bulk deposition, using 230 events, showed that variations in atmospheric deposition are explained better by measured concentration than by precipitation amount. In addition, measured concentration is related to precipitation by a significant power function with the exponent near –1. These observations led us to propose an inverse linear model which makes it possible to calculate two parameters: one of them is indicative of the mean composition of cloud rain and is assumed to be typical for the study area; the other parameter is representative of particulates, aerosols and gases that are washed out from the atmosphere in the initial phases of precipitation, including dry deposition. This initial component represents an average of 64% of the bulk deposition for the cations studied. The functions that explain the relations between atmospheric deposition and measured concentration are, within statistical limits, equal for the four cationsAbbreviations D Atmospheric deposition (g/ha) on an event basis - P Precipitation amount (mm) on an event basis - C Measured concentration (mg/l) on an event basis - i Sampling replicates     

陕西省不同生态区大气氮素干湿沉降的时空变异

为研究陕西省不同生态区大气氮素干湿沉降的时空变化规律,于2009年11月至2010年10月对4个生态区5个监测点的干湿沉降输入量进行为期1a的观测。结果表明:监测期内,榆林、洛川、西安、杨凌和安康地区总N沉降量分别为4.7、11.9、25.8、31.9和19.2 kg/hm2,其中N湿沉降量分别为2.9、10.4、24.8、27.7和16.3 kg/hm2,占总沉降的62%—96%,N干沉降量分别为1.8、1.5、1.0、4.1和2.9 kg/hm2,占4%—38%,且湿沉降与降雨量之间呈正相关关系,干沉降与之相反;各地区NH+4-N沉降量分别为2.0、6.4、17.0、17.2和11.9 kg/hm2,占总沉降的44%—66%,NO-3-N沉降量分别为2.6、5.5、8.8、14.7和7.3 kg/hm2,占34%—56%,除榆林地区外,其他地区以NH+4-N沉降为主。     

陕北典型农区大气干湿氮沉降季节变化

为了研究大气通过干湿沉降输入到农田土壤的氮通量,2007年6月至2008年5月在陕西榆林和洛川两地进行了为期一年的观测试验.结果表明:榆林和洛川地区大气总无机氮沉降通量分别为22.17和16.95 kg·hm~(-2)·a~(-1),湿沉降分别占95.1%和90.4%,干沉降分别占4.9%和9.6%,两个地区氮沉降均以湿沉降为主.总无机氮沉降中,NO_3~--N分别为12.22和9.24 kg·hm~(-2)·a~(-1),分别占总无机氮沉降量的55.1%和54.5%.由于污染水平、气象条件、下垫面特性等的差异,总无机氮沉降中,湿沉降量和NO_3~--N沉降量均是榆林地区大于洛川地区.     

The atmospheric deposition of phosphorus in Lake Victoria (East Africa)

Wet and dry atmospheric fluxes of total phosphorus (TP) and soluble reactive phosphorus (SRP) measured at four sites over a 12-month period were used to estimate lake-wide atmospheric phosphorus (P) deposition to Lake Victoria, East Africa. Atmospheric samples were collected in plastic buckets with top diameter of 25.5 cm by 30 cm deep. The highest P loading rates of 2.7 (TP) and 0.8 (SRP) kg ha^–2 year^–1 were measured at Mwanza compared to less than 1.9 (TP) and 0.65 (SRP) kg ha^–2 year^–1 measured in other three sites. By applying these loading rates to the lake surface, it was estimated that 13.5 ktons (13.5 × 10³ kg) of TP were deposited annually into the lake from the atmosphere. Thirty-two percent of the total was found to be in the SRP form. Dryfall, a component ignored in previous studies exceeded wet deposition by contributing 75% of the total P input. However, materials deposited by dryfall made a lesser contribution to soluble form of phosphorus, as SRP concentrations in the wet samples were 2–3 times higher than SRP concentrations in dry samples. The annual fluxes of phosphorus measured on the south and western shores of Lake Victoria (1.8–2.7 kg ha^–2 year^–1) are near the upper range of similar fluxes measured in the tropics. In comparison with the existing estimates of municipal and runoff P inputs from other studies, it is estimated that atmospheric deposition represent 55% of the total phosphorus input to the Lake Victoria. The four sampling sites were fairly clustered and wet and dry P deposition data were collected from shore/land stations and applied to open lake areas to estimate lake-wide P deposition. In this regard, the estimates determined here should be viewed as a first order approximation of actual P load deposited into the lake.     

Sensitivity of continental United States atmospheric budgets of oxidized and reduced nitrogen to dry deposition parametrizations

Reactive nitrogen (N_r) is removed by surface fluxes (air–surface exchange) and wet deposition. The chemistry and physics of the atmosphere result in a complicated system in which competing chemical sources and sinks exist and impact that removal. Therefore, uncertainties are best examined with complete regional chemical transport models that simulate these feedbacks. We analysed several uncertainties in regional air quality model resistance analogue representations of air–surface exchange for unidirectional and bi-directional fluxes and their effect on the continental N_r budget. Model sensitivity tests of key parameters in dry deposition formulations showed that uncertainty estimates of continental total nitrogen deposition are surprisingly small, 5 per cent or less, owing to feedbacks in the chemistry and rebalancing among removal pathways. The largest uncertainties (5%) occur with the change from a unidirectional to a bi-directional NH₃ formulation followed by uncertainties in bi-directional compensation points (1–4%) and unidirectional aerodynamic resistance (2%). Uncertainties have a greater effect at the local scale. Between unidirectional and bi-directional formulations, single grid cell changes can be up to 50 per cent, whereas 84 per cent of the cells have changes less than 30 per cent. For uncertainties within either formulation, single grid cell change can be up to 20 per cent, but for 90 per cent of the cells changes are less than 10 per cent.     

藏东南大气氮湿沉降动态变化——以林芝观测点为例

利用量雨器和湿沉降收集仪在藏东南通过2a的试验, 研究了该区大气氮素沉降的浓度、沉降量以及季节变化规律.结果表明:藏东南大气氮素湿沉降(无机氮)为1.33～3.05 kg/ (hm2·a),平均值为2.36 kg/ (hm2·a),降水中铵态氮和硝态氮的平均浓度分别为0.36 mg/L和0.10 mg/L ,NH+4-N/ NO-3-N接近4 .各形态氮月均浓度之间差别较大,具有明显的季节性,其中NH+4-N月均浓度动态变化明显,5、6、7月份浓度较高(＞0.5 mg/L),NO-3-N 12月份浓度(0.49 mg/L)为全年最高;氮浓度的季节变化,以春冬较高,夏秋季较低,离散程度以春季最大.降水量与各形态氮沉降呈一定幂型负相关,相关系数为0.705,0.641,分别达到0.006 (NH+4-N)和0.019(NO-3-N)的显著水平.氮月沉降以5～6月份最高,占全年的32.3%;氮季沉降以夏季所占比例最高,约占50%,冬季最低(2%～3%).     

鄂西北丹江口库区大气氮沉降

利用雨量器在鄂西北丹江口库区连续3a采集降雨样品,研究了大气氮沉降的变化动态。结果表明:2009—2011年月均总氮(TN)浓度为3.70—10.36 mg/L,与当月降雨量呈极显著线性负相关(R=-0.592**,n=32),季均TN浓度为冬季(8.21 mg/L)春季(3.94 mg/L)秋季(3.23 mg/L)夏季(2.70 mg/L),年均TN浓度为3.70 mg/L。大气氮素年均干湿总沉降量为26.53 kg/hm2,其中干沉降为7.80 kg/hm2,占总沉降量的29.4%;湿沉降为18.73 kg/hm2,占总沉降量的70.6%。干沉降中铵态氮(NH+4-N)、硝态氮(NO-3-N)、可溶性有机氮(DON)和颗粒态氮(PN)分别占TN的22.1%、16.8%、37.2%和23.9%,湿沉降中它们分别为TN的36.6%、34.4%、12.9%和16.1%。     

山西北部农村区域大气活性氮沉降特征

利用DELTA系统、被动采样器和雨量器在山西省北部生态脆弱区朔州的一个监测点通过一整年的监测试验,研究了该地区农村区域大气氮素干湿沉降的月际变化。结果表明:2011年该地区大气氮素湿沉降为12.43kgN hm~(-2)a~(-1),远低于华北平原大气氮素混合沉降的平均值28.0kg N hm~(-2)a~(-1),降水中铵态氮、硝态氮和有机氮平均分别为1.24 mg N/L、1.27 mg N/L、1.26mg N/L。大气氮素湿沉降的年内分布不均,60%的沉降集中在降水较丰沛的4-10月份。试验区干沉降以氧化态氮(HNO_3NO_2和pNO_3~-)的沉降为主,氧化态氮的干沉降量是还原态氮(NH_3和pNH_4~+)的1.37倍,大气氮素干沉降总量为35.43 kg N hm~(-2)a~(-1)。总体来看,作为典型的干旱区,该地区氮的干沉降是湿沉降的3倍,氮素干湿沉降总量达到47.86kg N hm~(-2)a~(-1)。此外,硝态氮和铵态氮在雨水中呈线性相关,而在PM_(10)颗粒物中乘幂正相关;雨水中总碳和总氮呈线性正相关,而PM_(10)颗粒物中二者呈二次多项式关系。鉴于朔州地区古城镇较高的氮沉降数量,应该对该地区输入农田的氮素环境养分引起足够重视。     

我国雷州半岛典型农田大气氮沉降

近一个半世纪以来,粮食和能源需求导致活性氮创造的急剧增加,从而导致各种活性氮的排放及其沉降的增加。氮沉降引起土壤酸化,水体富营养化,及敏感生态系统植物多样性的丧失等不良生态效应。因此定量不同生态系统氮沉降量对于确定该地区生态系统安全及氮循环有重要意义。南方地区氮沉降已有较多研究,主要集中于湿沉降的研究,选取雷州半岛地区典型农田综合研究了大气氮素的干湿沉降。结果表明:大气活性氮浓度NH3、HNO3、NO2、pNH+4和pNO-3浓度分别为5.62、0.88、3.16、3.30、2.02μg N/m3。采用欧洲氮沉降监测网的氮干沉降速率估算了大气氮干沉降量为17.6 kg N hm-2a-1。大气降雨NO-3-N浓度为(0.86±0.36)mg N/L,NH+4-N浓度为(1.11±0.68)mg N/L,大气降雨无机氮含量冬季最高,夏季最低。大气无机氮年湿沉降总量为25.3 kg N/hm2。湿沉降NH+4-N和NO-3-N,干沉降NH3、HNO3、NO2、pNH+4、pNO-3分别占沉降量的30.8%、28.0%、23.7%、5.4%、2.8%、3.9%、5.4%。湿沉降NH+4和干沉降NH3在氮沉降中占主导地位显示氮肥施用导致的NH3挥发对大气活性氮浓度及氮沉降的显著贡献。鉴于研究可观的氮沉降量(总沉降量42.9 kg N hm-2a-1),其向农田的养分的输入不容忽视;氮沉降对该地区水体,自然生态系统的环境影响需要受到重视。     

The chemistry of wet deposition for a tallgrass prairie ecosystem: inputs and interactions with plant canopies

The chemistry and nutrient inputs of wet deposition, and the N chemistry of throughfall, were characterized for a tallgrass prairie in north-central Kansas. Dominant ions in wetfall were NH ₄ ⁺ , Ca²⁺, H⁺, NO ₃ ^- , and SO ₄ ^2- ; weighted mean pH was 4.79. Principal sources of ions appeared to be natural emissions and wind-blown soils. Concentrations of NO ₃ ^- -N, NH ₄ ⁺ -N, and organic N in wet deposition were 0.31, 0.30, and 0.17 mg/L, respectively, resulting in N inputs of 2.5, 2.5, and 1.4 kg · ha^-1 · yr^-1. Comparisons with bulk precipitation suggested that at least 50% of atmospheric N inputs were from dry deposition. Concentrations of NO ₃ ^- -N, NH ₄ ⁺ -N, and organic N in unburned prairie throughfall were 0.27, 0.28, and 1.28 mg/L, and in burned prairie throughfall were 0.33, 0.37, and 0.91 mg/L, respectively. The prairie canopy intercepted up to 48% of incident precipitation. Lower inorganic N and higher organic N concentrations in throughfall relative to wet deposition probably resulted from leaf uptake of N and immobilization by microbes associated with the standing dead plant materials of the prairie canopy. The removal of these materials by fire is important in maintaining N availability for tallgrass prairie. Much of the N immobilization appeared to have been of N that was supplied to the prairie canopy by dry deposition.     

Nitrogen on microbial and global scales

Several temporal and spatial scales have been considered during the Symposium, and the presentations by Wallenda & Kottke (1998) and by Norby (1998) represent two extreme points in a wide range. They both deal with short and long-term impacts on the local as well as the global scale. I present here a few additional thoughts, and a subject that both papers have touched only slightly will be expanded: the differential impact of different forms of nitrogen deposition.     

Global change pressures on soils from land use and management

Soils are subject to varying degrees of direct or indirect human disturbance, constituting a major global change driver. Factoring out natural from direct and indirect human influence is not always straightforward, but some human activities have clear impacts. These include land‐use change, land management and land degradation (erosion, compaction, sealing and salinization). The intensity of land use also exerts a great impact on soils, and soils are also subject to indirect impacts arising from human activity, such as acid deposition (sulphur and nitrogen) and heavy metal pollution. In this critical review, we report the state‐of‐the‐art understanding of these global change pressures on soils, identify knowledge gaps and research challenges and highlight actions and policies to minimize adverse environmental impacts arising from these global change drivers. Soils are central to considerations of what constitutes sustainable intensification. Therefore, ensuring that vulnerable and high environmental value soils are considered when protecting important habitats and ecosystems, will help to reduce the pressure on land from global change drivers. To ensure that soils are protected as part of wider environmental efforts, a global soil resilience programme should be considered, to monitor, recover or sustain soil fertility and function, and to enhance the ecosystem services provided by soils. Soils cannot, and should not, be considered in isolation of the ecosystems that they underpin and vice versa. The role of soils in supporting ecosystems and natural capital needs greater recognition. The lasting legacy of the International Year of Soils in 2015 should be to put soils at the centre of policy supporting environmental protection and sustainable development.     

Atmospheric Deposition to the Turkey Lakes Watershed: Temporal Variations and Characteristics

We investigated the atmospheric concentrations and deposition fluxes of major ions to the Turkey Lakes Watershed (TLW) between 1980 and 1996. During that time, daily SO₄ ²⁻ concentrations in precipitation decreased markedly, while NO₃ ⁻, NH₄ ⁺, and H⁺ concentrations remained roughly constant. It appears that precipitation acidity did not decrease in spite of declining SO₄ ²⁻ concentrations due to a concurrent and counterbalancing decrease in the concentrations of Ca²⁺, Mg²⁺, and K⁺ in precipitation. The reasons for the decline in base cations are unknown, but this decline is probably related to decreasing emissions of soil-derived particles from agricultural, industrial, and road sources. A similar situation was seen during the same period in other parts of Canada, the eastern United States, and Europe. Wet, dry, and total (wet + dry) deposition fluxes of sulphur (S) and nitrogen (N) were estimated annually for the years 1980–96. The 17-year mean annual total (wet + dry) deposition of S to the watershed was estimated at 38.5 mmol m⁻² y⁻¹ (range 24.3–50.3). Total S deposition decreased by 35% from the early 1980s (1982–84) to the mid-1990s (1994–96), a decline consistent with the 23% decline in annual SO₂ emissions in eastern North America during the same period. In contrast, the annual total (wet + dry) deposition of oxidized N ranged from 39.8 to 60.4 mmol m⁻² y⁻¹, with a 15-year mean of 50.1 mmol m⁻² y⁻¹ and a net increase of 10% between the early 1980s (1983–85) and the mid-1990s (1994–96). This is in keeping with a 10% increase in NO_x emissions in eastern North America during the same period. For both S and N (oxidized), wet deposition dominated over dry deposition as the major mechanism for atmospheric input to the watershed. Annually, wet deposition accounted for approximately two-thirds of the total atmospheric deposition of both S and N. Dry S deposition was due more to gaseous SO₂ deposition (two-thirds of dry S deposition) than to particulate SO₄ ²⁻ deposition (one-third of dry S deposition). Dry deposition of oxidized N, however, was dominated (95%) by gaseous HNO₃ deposition, with minimal input from particulate NO₃ ⁻ deposition. Compared to several selected watershed/forest sites in Canada, the United States, and Europe, the estimated total deposition of S and N at the TLW was relatively high during the measurement period. Received 5 October 1999; accepted 1 March 2001.     

长白山森林生态系统大气氮素湿沉降通量和组成的季节变化特征

2009—2010年期间,利用雨量计收集法在长白山森林生态系统定位站开展定位观测,分析降水中氮素浓度,研究了该区域大气氮素湿沉降通量和组成的季节变化特征。结果表明,各形态氮素月均浓度之间差别较大,具有明显的季节性;其降水中浓度主要受降水量和降水频次的影响。全年氮素湿沉降中TN、TIN和TON的沉降量分别为27.64 kg N hm-2a-1、11.05 kg N hm-2a-1和16.59 kg N hm-2a-1,TON为沉降主体,占60.02%;其大气氮沉降量主要由降水量和降水中氮素浓度共同决定。该地区氮湿沉降量已处于我国中等水平,考虑到氮素的干湿沉降比例,本区域的年氮沉降量已接近或超过本区域的营养氮沉降临界负荷,存在一定的环境风险。该地区生长季(5—10月)的氮沉降量(16.59 kg N hm-2a-1)占全年氮沉降量的比例达到73.20%。生长季的氮沉降对于促进植物生长直接生态意义重大,而非生长季的氮沉降对于大量补充次年植物生长初期所需养分的间接生态意义明显。     

Characteristics and partitioning of ozone dry deposition measured by eddy-covariance technology in a winter wheat field

Aims Anthropogenic pollutants cause an increase in ground-level ozone concentration, which is a known threat to plant growth and yield and has been extensively observed worldwide. Since ozone is only slightly soluble in water, it is deposited mainly through dry deposition in terrestrial ecosystem. The object of this study was to analyze the characteristics of ozone dry deposition and to estimate the contribution of stomatal and non-stomatal ozone deposition pathways to total ozone deposition in a winter wheat field.Methods The research site was a winter wheat (Triticum aestivum) field located in Yongfeng experimental station of Nanjing University of Information Science & Technology. The data used in this study were collected from March 16, 2016 to May 30, 2016. We observed ozone dry deposition with an eddy-covariance system. This system mainly included a 3D sonic anemometer, an open-path infrared absorption spectrometer, a fast-response ozone chemiluminescent analyzer and a slow-response ozone monitor. We simultaneously measured meteorological data including solar radiation (SR), air temperature (T), air relativity humidity (RH), wind speed, net radiation, and rainfall. All raw data were recorded with data-logger and averaged every 30 min.Important findings Half hourly means of ozone concentrations (C_O3), ozone flux (F_O3) and ozone dry deposition velocity (V_d) in the winter wheat field were 32.9 nL·L^-1, -5.09 nmol·m^-2·s^-1, 0.39 cm·s^-1, and the ranges of them were 16-58 nL·L^-1, -2.9- -11.7 nmol·m^-2·s^-1, 0.17-0.63 cm·s^-1, respectively. F_O3 and C_O3/V_d were found to be mismatched with phase peaks occurring at different time intervals. The ecosystem was more effective on ozone dry deposition, under conditions of moderate to high SR (SR ≥ 400 W·m^-2), moderate T and humility (T = 18 °C and RH > 40%). The relationship between V_dmax and SR was this function (y = 1.06 -exp (-0.0094 - x)). V_dmax increased with SR When SR < 400 W·m^-2, and V_dmax reached its maximum when SR =400 W·m^-2. V_dmax maintained its maximum when SR ≥ 400 W·m^-2. The relationship between V_dmax and T was “bell” curve (y = 1.06 - (x - 18)²/169). V_dmax reached its maximum when T = 18 °C. V_dmax decreased with RH when RH < 40 % (y = 0.030x - 0.106). The variation of V_d might uncertainty when RH was high. There was a liner positive relationship between friction velocity (u*) and V_d, but this relationship was not significant. The mean day-to-day and daytime contributions of stomatal and non-stomatal ozone deposition pathway to total ozone deposition were 32%, 68% and 42%, 58%, respectively, during the whole experimental period.     

Radon dosimetry applications ofin vitro tracheobronchial-deposition measurements

Deposition efficiencies of monodisperse ammonium fluorescein aerosols have been measured in simulated human lungs made of replica laryngeal casts combined with trachebronchial systems. Other tests, with radiolabelled submicron-sized particles, combined the larynges with replica tracheobronchial casts. The laryngeal casts had internal flow rate-specific geometries. Data indicate thatin vitro bifurcations have ?hot spots? or highly localized deposits, particularly at carinal ridges, suggesting that epithelial cells at airway branching sitesin vitro receive increased exposures to inhaled particulate matter. For dosimetry purposes, therefore, the lung should be likened to a series of Y-shaped airway junctures. The data have risk assessment applications for ambient radon progeny and radioactive airborne particles found in uranium mining and milling operations.