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131.
氮氧化物(NOX)在对流层中的收支与循环的研究 总被引:2,自引:0,他引:2
对氮氧化物(NOx)在对流层中的收支与循环问题,及其在对流层中的各种源汇过程进行了综述与讨论。其中包括NOx的人为排放与自然排放,干、湿沉降的清除及其相对重要性等。并对我国NOx的人为排放与自然排放进行了估算。 相似文献
132.
The contribution of nitrogen and phosphorus due to precipitation constitutes the second most important route after superficial runoff. The sampling carried out during a two-year period by means of a precipitation collector allows us to determine the contribution of this route both qualitatively and quantitatively. Nitrogen is mainly supplied in an inorganic form, while phosphorus is principally supplied as orthophosphate. During the period of this study (March 1986–February 1988) it was found that in the Santillana Reservoir Watershed the level of nitrogen supplied by precipitation constitutes an average of 4.87% and the level of phosphorus constitutes 8.01%. The contribution of nitrogen varies in inverse ratio to precipitation and the contribution of phosphorus varies in direct ratio. 相似文献
133.
H. D. Freyer 《Pure and Applied Geophysics》1978,116(2-3):393-404
Preliminary nitrogen isotope data for ammonia from animal urine, fuel combustion, fertilizer use and fertilizer factories have been measured or estimated. It turns out that direct nitrogen isotope measurements of atmospheric ammonia at Jülich are in the expected range calculated from the ranges of different sources. For deposition of atmospheric ammonium in Jülich-rain a depletion in15N with respect to atmospheric ammonia has been found which is explained by isotope fractionations during rainout and washout. In correspondence with this fractionation model are nitrogen isotope data of rain-ammonium from coastal areas, which are enriched in15N due to the fact that sea water acts as a sink for atmospheric ammonia.For Jülich rain-nitrate a pronounced seasonal trend has been detected with lower15N data in spring and summer than in autumn and winter. This trend is interpreted by different nitrogen isotope data of anthropogenic and natural nitric oxides which have been measured or estimated from isotope fractionation effects during nitrification and denitrification reactions in soils. It should be possible to get better global estimations for anthropogenic and natural nitric oxides from nitrogen isotope measurements. 相似文献
134.
The hydrogeochemistry of the Lake Waco drainage basin,Texas 总被引:1,自引:0,他引:1
The origin of surface water chemistry in highly impacted drainage basins must be investigated on a drainage-basin scale if the causes of the pollution are to be elucidated. This study characterizes and deciphers the surface water chemistry of a nutrient polluted river system in central Texas. Four tributaries of the Lake Waco reservoir were chemically characterized temporally and spatially in order to gain a complete understanding of the nature and origin of dissolved solids being transported into the lake. Temporal chemical variations measured at the base of each of the drainage basins are repetitive and seasonal. The most periodic and well-defined variation is exhibited by nitrate concentrations although many of the other solutes show seasonal changes as well. These temporal chemical changes are controlled by seasonal precipitation. During rainy seasons, the shallow aquifer is recharged resulting in stream discharge that is high in nitrate, calcium, and bicarbonate. When the shallow flow system is depleted in the summer, stream waters are dominated by deeper groundwater and become rich in sodium. Spatial variations in the chemistry of South Bosque surface waters were characterized using the snapshot technique. The spatial distribution of nitrate in surface waters is controlled by fertilizer application to row crops and the location of a munitions factory. The concentrations of naturally derived solutes such as Ca+, Na+, Cl–, and SO4–2are controlled by underlying lithologies. 相似文献
135.
A field trial on 3-year-old Prosopis alba growing on pH 8.5 soils in Argentina was conducted to identify mineral nutrients that were most limiting growth and to determine correlations among these nutrients. As applications of nutrients such as Zn, Cu and P would be soon rendered unavailable due to the high pH, combinations of elemental S to decrease the pH were examined along with macro and micronutrient soil additions. Thirty trees were selected with stem diameters ranging from 2.8 to 4.5 cm and divided into five treatments in a completely randomized design with 1 tree per replicate. The treatments were: (1) control, (2) addition of elemental S to lower the pH, (3) addition of S and triple superphosphate (P), (4) addition of S, P and a complete blend of micronutrients and (5) addition of S, P, micronutrients and K and Mg. Biomass increases were estimated using regression equations on stem diameter increases. A small non-significant decrease in pH of about 0.3 pH was obtained in the treatments with S, except for treatment which contained micronutrients in the form of strong base oxides. There was a significant increase in electrical conductivity due to the oxidation of the S. The best treatment containing S, P and micronutrients had a 42% increase significant biomass increase over the control. Growth was positively correlated with leaf levels (decreasing order of significance) of K, S, P, and Zn and negatively correlated with leaf Na and Ca. The leaf K, which had the highest positive correlation with growth, was highly significantly positively correlated with leaf S, P, N, and Zn and highly significantly but negatively correlated with leaf Ca, Mg and Mn. Leaf N was very highly correlated with leaf Zn, S and P concentrations. Indian workers have found that 20 years after establishment Prosopis juliflora changed the soil pH from 10.4 to 8.0. Since trees on 10 m×10 m spacings are suggested to be ultimate climax density for these ecosystems, apparently it will only necessary to add inexpensive small quantities of elemental S, Zn and K directly around 100 small trees ha−1 to effect a major soil reclamation over the entire ha. 相似文献
136.
Fertilizers and liming agents are generally used to achieve optimal economic yields. However, several negative effects of long‐term annual fertilization of nitrogen (N) in particular have been observed, such as reduced cation exchange capacity and decreased base saturation, which may stimulate accelerated leaching loss of other nutrients. Equilibrium‐tension lysimeters installed at a depth of 1.4 m were used to evaluate leaching of soil‐solution ionic constituents from a tallgrass prairie restoration and optimally and deficiently N‐fertilized, no‐tillage (NT) and chisel‐plowed (CP) maize (Zea mays L.) agroecosystems on Plano silt loam soil (fine‐silty, mixed, superactive, mesic Typic Argiudoll). This study was conducted in south‐central Wisconsin, USA during a 1‐year period of above‐normal precipitation between January 2000 and January 2001. The loss of soluble constituents added to agroecosystems to maintain adequate soil fertility and pH, such as N, phosphorus, potassium, calcium, and magnesium, was generally numerically smaller from the natural prairie 25 years after conversion from cultivated agriculture than from optimally and deficiently N‐fertilized, NT and CP maize agroecosystems, though the differences were not significant. Tillage and fertilizer N‐rate generally did not significantly affect drainage, ionic concentrations, or their leaching losses in the maize agroecosystems, though all parameters evaluated tended to be numerically smaller in the deficiently than optimally N‐fertilized maize agroecosystems. Nitrate‐N leaching losses were generally significantly positively correlated with leaching losses of K, Ca, Mg, and Na in the maize agroecosystems, but not for the prairie, indicating that nitrate‐N leaching plays a significant role in the concomitant loss of cations to maintain soil‐solution charge balance in N‐fertilized maize agroecosystems in a temperate environment. 相似文献
137.
The present paper reports recent improvements in sealed tube combustion technique used for the determination of N isotopic composition in various rocks characterized by low N contents (i.e. few ppm). Nitrogen is extracted from samples by combustion in quartz tubes sealed under vacuum. The nitrogen gas purified using Cu, CuO and CaO, is quantified as dinitrogen N2 by capacitance manometry in ultra-high vacuum line. Nitrogen isotopic analysis is performed on a triple-collector static vacuum mass spectrometer, allowing measurement of nanomole quantity of N2. Nitrogen amount and isotopic composition of the analytical blanks are low and describe Gaussian distribution with mean values of 0.65 ± 0.30 nmol N and − 3.7‰ ± 2.7‰, respectively (2σ). Systematic analyses of international and internal standards demonstrate that this technique provides accurate and precise results. The precision on N content and isotopic composition are better than ± 8% and ± 0.5‰ respectively, even for samples containing less than 2 ppm N. The sealed tube combustion technique is shown to apply successfully to rocks of various lithologies such as metagabbros, metaperidotites and altered basalts. It is thus suitable for studying oceanic crust in a perspective to better constrain N exchanges between Earth mantle and surface reservoirs. The investigation can also be extended to analysis of small size samples, particularly when little sample exists and when high spatial resolution is required. 相似文献
138.
The concentrations of particulate Polycyclic aromatic hydrocarbons (PAHs) were measured at Gosan, a background site in Korea for 1 year between November 2001 and November 2002. The total concentrations of 14 PAH compounds at Gosan were between 0.52 and 14.76 ng m− 3 and about 3–15 times higher than those at other rural or remote sites in the world. Seasonal trend was observed for particulate PAHs concentrations at Gosan with higher levels during heating season due to increased fossil fuel usage and the movement of air parcels from Asian continent. Principal component factor analysis (PCF) for PAHs showed three factors; combination of coal combustion and vehicular emission, natural gas combustion, and unidentified one. However, PCF for the combined data of PAHs, inorganic ions, and elements revealed that the unidentified factor consists of crustal species, sea salts, and four PAH compounds. Thus, this factor is thought to be transport of crustal species with organics from combustion sources. The major variables which determine the sources of PAHs are the heating season and the movement of air parcels from Asian continent. 相似文献
139.
Particulate organic carbon (POC) of 161 water samples collected from 8 depths (surface to 1000 m) at 21 stations was measured. The POC concentrations ranged from 154 to 554 ¼g per litre at the surface and decreased in the upper 300 m water column. At greater depths (> 300 m), POC concentrations increased and were similar (145 to 542 ¼g1?1) to those observed at surface. Deep water POC maximum was embedded within the oxygen minimum layer and was also associated with high phosphate-phosphorus. The POC contents increased, whereas oxygen decreased as the distance away from the shore increased. Phytoplankton biomass was a major source of POC. The observed pattern of POC is discussed with respect to some physicochemical and biological factors. 相似文献
140.
The chemical reactivity of NO and NO2 is so rapid that their fluxes and concentrations can be considerably modified from that expected for conserved variables in the atmospheric surface layer, even as low as a meter above the surface. Fitzjarrald and Lenschow (1983) have calculated flux and mean concentration profiles for NO, NO2 and O3 in the surface layer using numerical techniques. However, their solutions do not approach the photostationary state at large heights. Here we solve a simpler set of equations analytically (i.e. we assume a constant O3 concentration and neutral hydrodynamic stability), and are able to show how the flux profiles behave at large heights assuming that the concentrations approach their photostationary values. We find, for example, that at large heights the ratio of the flux of NO to that of NO2 is equal to the ratio of their concentrations. These results are relevant to estimating surface fluxes of NO and NO2, and are most applicable to nonurban environments where NO and NO2 concentrations are usually much less than O3 concentration.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献