首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
We determined proton budgets of surface soils in a deciduous forest (Df) and a coniferous forest (Cf) of Volcanogenous Regosols in Tomakomai, Hokkaido of northern Japan. The total H+ source was 12.9 and 11.6 kmolc ha?1 y?1 at Df and Cf respectively, and the external H+ was 1% at Df and 2% at Cf. The primary H+ sources were vegetation uptake of base cations and nitrification, while the major H+ sinks were release of base cations and NO3 + uptake by vegetation. Leaching incubation experiments using A horizon soils including Df and Cf with NH4 + solutions (5.3, 15.9 mg N L?1) showed that H+ from nitrification was generally higher in the Df soil than Cf soil, and nitrification of Tomakomai Df soil was the highest in both treatments. Results of multiple regression analyses suggested that pHkCl and exchangeable Ca2+ contributed to the H+ generation via nitrification. Leaching experiments with dilute HCl (pH 3.3) revealed that cation release (mainly Ca2+) occurred, and the proportion of release by decrease of exchangeable cations was higher than that by mineral weathering. Mineral weathering in the Tomakomai soil was higher than the other soils.  相似文献   

2.
为探究三峡库区2种土地利用方式下土壤交换性盐基离子及土壤碳氮含量对氮添加的响应,以湖北省秭归县的林地和果园土壤为研究对象,进行室内土柱淋溶模拟试验,研究4种不同氮添加量(0,50,120,200 kg/(hm2·a))下,土壤中交换性Ca2+、Mg2+、Na+、K+以及NO3--N、DOC的变化。结果表明：随着氮添加量的增加,林地土壤中的交换性盐基离子淋失量显著增加(p<0.05),而果园土壤中的交换性盐基离子淋失量无显著变化,且林地土壤中交换性盐基离子淋失总量与各盐基离子淋失量均高于果园土壤;经N1、N2、N3处理后,与对照组(N0)相比,林地土壤中的交换性盐基离子淋失总量分别增加1.78%,4.45%,8.49%,且NO3--N淋失量分别增加89.21%,77.73%,157.25%,说明氮添加通过加剧土壤中NO3--N的淋失带走土壤中交...  相似文献   

3.
The characteristics of production and immobilization of NO3-N were evaluated for soils from four forest types in Kochi Prefecture, southern Japan. Net NO3-N production during the laboratory incubation differed among the soils from the four forest types, being high under Japanese cedar (Cryptomeria japonica D. Don) and deciduous hardwood, and negligible under Japanese red pine (Pinus densiflora Sieb. et Zucc.) and hinoki cypress (Chamaecyparis obtusa Endlicher). Nitrification under Japanese cedar and hardwood was mainly autotrophic based on the fact that nitrification was inhibited by acetylene or nitrapyrin, and was not affected by cycloheximide. Net NO3-N production in these soils increased by glycine addition, but did not increase appreciably by NH4Cl addition. However, net NO3-N production increased after the addition of CaCO3 with NH4Cl. These results indicate that the substrate of nitrification is NH3 rather than NH4 + and that the added NH4 + is not utilized by nitrifiers at low pH values. With NO3-N addition to soils under red pine and hinoki cypress, immobilization of NO3-N was observed followed by rapid production of NH4-N. These findings suggested that mobile NO3-N can be converted to less mobile NH4-N by the activities of soil microorganisms. This microbial process may play an important role in retaining nitrogen within forest ecosystems where the potential of N loss is high due to the high precipitation in the area.  相似文献   

4.
Rain water at two forested sites in Guangzhou (south China) show high concentrations of SO4 2?, NO3 ? and Ca2+ and display a remarkable seasonal variation, with acid rain being more important during the spring and summer than during the autumn and winter. The amount of acid rain represents about 95% of total precipitation. The sources of pollutants from which acid rain developed includes both locally derived and long-middle distance transferred atmosphere pollutants. The seasonal variation in precipitation chemistry was largely related to the increasing neutralizing capacity of base cations in rainwater in winter. Soil acidification is highlighted by high H+ and Al3+ concentrations in soil solutions. The variation in elemental concentration in soil solution was related to nitrification (H+, NH4 + and NO3 ?) and cation exchange reaction (H+, Al3+) in soil. The negative effect of soil acidification is partly dampened by substantial deposition of base cations (Ca2+, Mg2+ and K+) in this area.  相似文献   

5.
In a forest in Flanders (Belgium), situated in a region of intensive livestock production, comparable stands of Corsican pine and silver birch were studied for (1) NH4 + and NO3 - concentrations in throughfall water and soil solution and (2) depositions and leaching of NH4 + and NO3 - to groundwater. In each stand, throughfall collectors and porous cup lysimeters at three depths (0.1m, 0.5m and 1m) were installed in three replicated sets. Throughfall concentrations of ammonium and nitrate were significantly different for both species as well as soil solution concentrations of nitrate at all depths. Under pine, nitrate concentrations of the soil solution at 1m depth clearly exceeded the Belgian critical level for drinking water (50 mg.1-1). Under birch, this level was only sporadically exceeded. During the sampling period, the depositions of NH4 +-N and NO3 --N reached respectively 21.6 kg/ha and 6.3 kg/ha under birch and 81.3 and 15.2 kg/ha under Corsican pine. Nitrate-N leaching under silver birch amounted 25.4 kg/ha whereas 56.4 kg/ha was measured under Corsican pine.  相似文献   

6.
Solution chemistry was measured in two major inlets, lake water column, lake outlet, and soils of the South Lake watershed in the Adirondack Mountains, New York. The east inlet had greater concentrations of H+, sulfate-S, and Al and smaller concentrations of base cations and silica than the west inlet (70, 116, 25, 90, 64 and 4, 99, 8, 228, 148 μeq L?1 of H+ and sulfate-S, μmol L?1 Al, μeq L?1 total base cations and μmol L?1 silica in east and west inlets, respectively). Concentrations of base cations in C horizon soil solutions (157 μeq L?1 total base cations) were smaller and greater than west and east inlets, respectively. This suggests that water flowing into the west inlet contacted deeper mineral layers, whereas water reaching the east inlet did not. Lake and lake outlet concentrations were also intermediate between the two inlets, and the lake was acidic (pH 4.9 to 5.1) with relatively high total monomeric Al concentrations (8 to 9 μmol Al L?1). The east inlet also had greater DOC concentrations than the west (0.38 and 0.24 μmol C L?1, respectively), again indicating that soil solutions entering the east inlet passed through the forest floor but had more limited contact with deeper mineral layers in comparison with the west inlet. Differences between the streams are hypothesized to be related to contact of percolating solutions with mineral soil horizons and underlying glacial till, which provides neutralization of acidic solutions and releases base cations. This work indicates that processes controlling surface water acidification can be spatially quite variable over a small watershed.  相似文献   

7.
Soil chemical properties affecting NH4+ sorption in forest soils   总被引：2，自引：0，他引：2  
Fourteen European forest soils from the boreal to the mediterranean climate on different parent materials were investigated with respect to their ability to store NH4+ in exchangeable form, using sorption isotherms. Distribution coefficients for NH4+ sorption per unit weight of soil were in the range of 0.02 to 0.77. NH4+ sorption coefficients were usually highest in the forest floor of a given soil. NH4+ sorption behaviour of mineral soil horizons was correlated to soil parameters that are determined during routine soil analysis. A combination of CEC and base saturation explained up to 95% of the variability Of NH4+ sorption. In the forest floors, variability in NH4+ sorption could not be explained quantitatively from independent soil parameters. The affinity of the sorption sites for NH4+ was the most important factor for explanation of the variability in NH4+ sorption in the forest floors but was of low importance in mineral soil horizons. As NH4+ exchanges predominantly base cations, susceptibility of NH4+ to transport through the soil profile increases with Iowbase saturation of a soil as well as with low CEC values.  相似文献   

8.
Field experiments were conducted to determine the effect of nitrogen (N) fertilizer forms and doses on wheat (Triticum aestivum L.) on three soils differing in their ammonium (NH4) fixation capacity [high = 161 mg fixed NH4-N kg?1 soil, medium = 31.5 mg fixed NH4-N kg?1 soil and no = nearly no fixed NH4-N kg?1 soil]. On high NH4+ fixing soil, 80 kg N ha?1 Urea+ ammonium nitrate [NH4NO3] or 240 kg N ha?1 ammonium sulfate [(NH4)2SO4]+(NH4)2SO4, was required to obtain the maximum yield. Urea + NH4NO3 generally showed the highest significance in respect to the agronomic efficiency of N fertilizers. In the non NH4+ fixing soil, 80 kg N ha?1 urea+NH4NO3 was enough to obtain high grain yield. The agronomic efficiency of N fertilizers was generally higher in the non NH4+ fixing soil than in the others. Grain protein was highly affected by NH4+ fixation capacities and N doses. Harvest index was affected by the NH4+ fixation capacity at the 1% significance level.  相似文献   

9.
Research was initiated in 1984 in an attempt to quantify and test possible hypotheses for the systematic decline and mortality of red spruce (Picea rubens Sarg.) observed in the southern Appalachian Mountains. Field surveys have documented increases in decline symptoms. By 1986, 7% of all tagged red spruce trees in permanent plots were dead. This number, partially due to the effects of severe weather, increased to 41% in 1987. An insect and disease survey initiated in 1985 on 100 permanent plots has yielded little significant pathology or insect infestation. With the exception of the balsam wooly adelgid (Adelges picea (Ratz)), few signs or symptoms of disease or insect attack were noted on either Fraser fir (Abies fraseri) (Pursh Poir) or red spruce populations. Cultures from destructively-sampled root systems yielded few significant pathogens that could contribute to decline symptoms. Measurements of throughfall in 1986 yielded estimates of total wet deposition for NO3 ? and SO4 2? of 25 and 75 kg ha?1 yr?1 respectively. Using net throughfall quantities, we estimate that between 40 and 60% of this input was due to cloud impact. Mean-volume-weighted pH per cloud event was 3.5. Over 75% of the cloud events sampled had a pH < 4.0. Cloud and rain water was dominated by H+, NH4 +, NO3 ?,, and SO4 2? ions. Interaction with the forest canopy resulted in an enrichment of throughfall with base cations (K+, Ca2+, and Mg2+) and a loss of H+ and NH4 +. Mean-volume-weighted pH for throughfall was 3.9. The effects of simulated acidic cloud water on the epicuticular waxes of red spruce needles were studied during the summer of 1987. The cuticle proper of both 1986 and 1987 needles did not appear to be damaged by the treatments. The wax crystals which constitute the stomatal wax plugs, however, exhibited substantial degradation by simulated treatments at or below pH 3.5.  相似文献   

10.
The contribution of atmospheric acids to cation leaching from a podzolic soil under mature maple-birch forest in central Ontario was examined during 1983. The movement of base cations was associated largely with NO3 ?, SO4 2? and organic acid anions in surface soil horizons, with SO4 2? and NO3 ? below the effective rooting zone, and SO4 2? and HCO3 ? in streamflow. Mineral soil horizons could adsorb little additional SO4 2? or associated cations at current soil solution SO4 2? concentrations. Therefore it is concluded that the soil in situ lacks a strong affinity for SO4 2?. Current annual inputs to the forest of SO4 2? and NO3 ? in bulk precipitation (26.4 and 18.2 kg ha?1, equivalent to 8.8 kg S and 4.1 kg N ha?1 , respectively) contributed significantly to cation leaching from the soil. In order to maintain exchangeable cations in soil at current levels, a rate of weathering yielding 29.6, 5.0, 4.4 and 2.2 kg ha?1 yr?1 of Ca2+, Na+, Mg2+ and K+, respectively, would be required.  相似文献   

11.
A study was carried out to investigate the potential gross nitrogen (N) transformations in natural secondary coniferous and evergreen broad-leaf forest soils in subtropical China. The simultaneously occurring gross N transformations in soil were quantified by a 15N tracing study. The results showed that N dynamics were dominated by NH4+ turnover in both soils. The total mineralization (from labile and recalcitrant organic N) in the broad-leaf forest was more than twice the rate in the coniferous forest soil. The total rate of mineral N production (NH4+ + NO3−) from the large recalcitrant organic N pool was similar in the two forest soils. However, appreciable NO3− production was only observed in the coniferous forest soil due to heterotrophic nitrification (i.e. direct oxidation of organic N to NO3−), whereas nitrification in broad-leaf forest was little (or negligible). Thus, a distinct shift occurred from predominantly NH4+ production in the broad-leaf forest soil to a balanced production of NH4+ and NO3− in the coniferous forest soil. This may be a mechanism to ensure an adequate supply of available mineral N in the coniferous forest soil and most likely reflects differences in microbial community patterns (possibly saprophytic, fungal, activities in coniferous soils). We show for the first time that the high nitrification rate in these soils may be of heterotrophic rather than autotrophic nature. Furthermore, high NO3− production was only apparent in the coniferous but not in broad-leaf forest soil. This highlights the association of vegetation type with the size and the activity of the SOM pools that ultimately determines whether only NH4+ or also a high NO3− turnover is present.  相似文献   

12.
In a laboratory study, KCI- a neutral salt - equivalent to 300kg K/ha and 272 kg CI/ha was applied to the surface of undisturbed columns of a forest soil (Terra Fusca Rendzina) under steady state unsaturated flow conditions (1.0 cm/day). The effluent of the five soil columns was collected daily, and pH, cation- and anion concentrations were measured. Most of the applied K ions were retained in the top 10cm of the soil and moved in decreasing amounts further down the column. Among the cations studied Ca++, Mg++, and Na+ were lost from the system, K+, NH4, Fe+++, Mn++, H+, and Al+++ were retained. Nitrate and sulfate concentrations in the leachates showed a temporary decrease when CI passed through the columns. This decrease was accompanied with a decrease in pH. CI?, NO3?, and SO4? exhibited leaching losses. Besides these anions, HCO3? played an important role.  相似文献   

13.
Precipitation chemistry was discussed from the viewpoint of potential sources for four rural sites where wet-only daily-basis measurement data sets were available during the period from April 1996 to March 1997 in Japan. Annual volume-weighted mean concentrations of nss-SO4 2? and NO3 ? ranged from 18.0 to 34.6 µeq L?1, and from 9.3 to 23.1 µeq L?1, respectively. The degree of neutralization of input acidity in terms of the concentration ratio, [H+] / ([nss-SO4 2?] + [NO3 ?]), ranged from 0.46 to 0.63. This suggests that about half of the input acidity due to H2SO4 and HNO3 was neutralized by NH4 + and nss-Ca2+ to produce the pH values of 4.46 to 4.82 for these sites. Maximum likelihood factor analysis was then performed on the logarithmically transformed daily wet deposition of major ions. Two factors successfully explained a total of about 80% of the variance in the data for each site. Interpreting varimax rotated factor loadings, we could identify two source types: (1) acid source with large loadings on ln(H+), ln(nss-SO4 2?), ln(NO3 ?) and ln(NH4 +), (2) sea-salt source with large loadings on ln(Na+), ln(Cl?), ln(Mg2+) and ln(K+). The rural wet deposition over Japan appears to have a similar structure in terms of the kinds of sources and their relative location.  相似文献   

14.
Ion mass and H+ budgets were calculated for three pristine forested catchments using bulk deposition, throughfall and runoff data. The catchments have different soil and forest type characteristics. A forest canopy filtering factor for each catchment was estimated for base cations, H+, Cl? and SO 4 2? by taking into account the specific filtering abilities of different stands based on the throughfall quality and the distribution of forest types. Output fluxes from the catchments were calculated from the quality and quantity of the runoff water. Deposition, weathering, ion exchange, retention and biological accumulation processes were taken into account to calculate catchment H+ budgets, and the ratio between external (anthropogenic) and internal H+ sources. In general, output exceeded input for Na+, K+, Ca2+, Mg2+, HCO 3 ? (if present) and A? (organic anions), whereas retention was observed in the case of H+, NH 4 + , NO 3 ? and SO 4 2? . The range in the annual input of H+ was 22.8–26.3 meq m?2 yr?1, and in the annual output, 0.3–3.9 meq m?2 yr?1. Compared with some forested sites located in high acid deposition areas in southern Scandinavia, Scotland and Canada, the catchments receive rather moderate loads of acidic deposition. The consumption of H+ was dominated by base cation exchange plus weathering reactions (41–79 %), and by the retention of SO 4 2? (17–49 %). The maximum net retention of SO 4 2? was 87% in the HietajÄrvi 2 catchment, having the highest proportion of peatlands. Nitrogen transformations played a rather minor role in the H+ budgets. The ratio between external and internal H+ sources (excluding net base cation uptake by forests) varied between 0.74 and 2.62, depending on catchment characteristics and acidic deposition loads. The impact of the acidic deposition was most evident for the southern Valkeakotinen catchment, where the anthropogenic acidification has been documented also by palaeolimnological methods.  相似文献   

15.
The effects of incubation time, vegetation type (represented by a pine plantation, a protected and a periodically burnt eucalypt forest), lime and finely ground pine needles on the transformation of (15NH4)2SO4 and K15NO3 were studied in incubation experiments with a sandy lateritic podzolic soil from south-east Queensland. Microorganisms were counted so as to relate N transformations to particular groups of microorganisms.The heterotrophic miroflora utilized NH+4 as a source of N in preference to NO?3, and autotrophic nitrifiers seemed to be weak competitors for NH+4. Lime caused a slight loss of NO?3 and this was accompanied by an increase in the population of denitrifying bacteria.Lime promoted immobilization of NH+4 by heterotrophic bacteria and subsequent mineralization by nitrifying bacteria, but when pine needles were also added the nitrifiers were suppressed and immobilization by heterotrophic bacteria dominated. Pine needles alone stimulated fungi to immobilize NH+4.While reforestation with exotic pines caused a loss of total-N there was evidence of increased turnover, i.e. more rapid immobilization and nitrification, in pine plantation soils. Prescribed burning also promoted nitrification while reducing total-N.  相似文献   

16.
Root development responds not only to the quantity of inorganic nitrogen in the rhizosphere, but to its form, NH4+ or NO3?. Root growth of tomato showed a hyperbolic response to soil levels of inorganic nitrogen: very few roots were found in soil blocks depleted in inorganic nitrogen, roots proliferated as soils increased to 2 μg NH4+-N g?1 soil or 6 μg NO3?-N g?1 soil, and root growth declined in soils with the higher levels of inorganic nitrogen. High NH4+ concentrations inhibited root growth, but low concentrations promoted the development of an extensive, fine root system. Supply with NO3? as the sole nitrogen source led to a more compact root system. These differences in root morphology under NH4+ and NO3? nutrition may be mediated through pH. Rice and maize roots absorbed NH4+ most rapidly right at the apex and appeared to assimilate this NH4+ in the zone of elongation. During NH4+ assimilation, root cells must release protons, and the resulting acidification around the walls of cells in this region should stimulate root extension. By contrast, NO3? absorption reached a maximum in the maturation zone of rice and maize roots, and this NO3? was probably assimilated in more basal regions. Absorption of NO3? requires proton efflux, whereas NO3? assimilation requires proton influx. The net result under NO3? nutrition was only subtle shifts in rhizosphere pH that probably would not influence root elongation. The signal through which roots detect changes in rhizosphere NH4+ and NO3? levels is still obscure. It is proposed that a product of nitrogen metabolism such as nitric oxide serves as a signal.  相似文献   

17.
On the Problem of Protecting the Base Area beneath intermediate manure Storage Piles on Non-Permanent Sites with Bentonite or Straw The suitability of bentonite and straw as materials for protecting the soil against the infiltration of leached nutrients was testet on an intermediate storage pile of cattle manure established during the winter months of 93/94. During the 185-day storage period, 205 g of Nt (68% in the form of NH4+) and 695 g K+/m3 were leached out of the manure. These nutrients seeped away into the soil, but with increasing depth, the concentrations of NH4+-N and K+ in the soil water dropped while those of NO3? rose not to harmful levels. Under the test piles whose base areas had been protected with bentonite, the concentrations of NH4+-N and K+ in the soil water were in all cases significantly lower than under the test piles with straw base or no base protection. Both cations were to a large degree absorbed by the bentonite layer, and thus were readily available for recycling. The Nmin content in particular was reduced in the soil beneath the straw layer. One possible explanation for this fact is that nitrogen was reincorporated by microorganisms due to the plentiful supply of carbon.  相似文献   

18.
Changes in soil solution composition and concentrations of exchangeable cations and mineral N in undisturbed cores of pasture soil were investigated in two experiments following applications of sheep urine to the cores. The major cations applied in the urine were K+ and Na+, and the major anions were HCO3? and Cl?. Addition of urine increased concentrations of exchangeable K+, Na+ and NH4+ and measured ionic strength of the soil solution throughout the surface 15 cm of soil, demonstrating that the urine moved through the core by macropore flow immediately following addition. Immediately following urine application the ionic strength in soil solution in the surface 2.5 cm of soil increased from 4–6 MM to 24–41 mM. Hydrolysis of urine-urea was extremely rapid, and in less than 1 d high concentrations of NH4+-N (i.e. 270–370 mg N kg?1) had accumulated in the surface 0–2.5 cm of the urine patch, and soil pH had risen by over one unit. Nitrification then proceeded and, after approximately 15 d, NO3? became the dominant form of mineral N present. During nitrification, soil pH declined and the ionic strength of the soil solution increased substantially with NO3? becoming the dominant anion present in solution. There were concomitant increases in the concentrations of Ca2+ and, to a lesser extent, Mg2+ in the soil solution as NO3? concentrations increased. After approximately 30 d, concentrations of exchangeable NO3? had risen to 250–330 mg N kg?1, soil solution NO3? concentrations had increased to about 80 mmol, dm?3, and ionic strength in the soil solution had increased to 130–140 mM. These results demonstrate the dominating effect of N transformations in causing large fluctuations in the pH, ionic composition and ionic strength of the soil solution in the urine patch. It was concluded that nutrient availability in the patch was affected directly by nutrient addition in urine, and also probably indirectly through the fluctuations in soil solution pH and ionic strength that occur.  相似文献   

19.
为了研究氮沉降对次生林土壤碳氮组分和酶活性的影响,以华西雨屏区湿性常绿阔叶次生林为对象,从2014年1月起进行野外定位模拟氮沉降试验,分别设置对照(CK,+0 g/(m^2·a))、低氮(LN,+5 g/(m^2·a))和高氮(HN,+15 g/(m^2·a))3个氮添加水平。在氮沉降进行27个月后,按照腐殖质层和淋溶层表层进行取样,测定不同土层土壤总有机碳(TOC)、可浸提溶解性有机碳(EDOC)、易氧化碳(ROC)、全氮(TN)、硝态氮(NO_3^-—N)和铵态氮(NH_4^+—N)含量以及蔗糖酶、脲酶、酸性磷酸酶和多酚氧化酶活性。结果表明:模拟氮沉降显著增加该次生林腐殖质层土壤的TOC和NH_4^+—N含量,显著增加腐殖质层和淋溶层表层土壤的NO_3^-—N含量,腐殖质层土壤C/N显著升高。淋溶层表层土壤TOC、NH_4^+—N、C/N以及2层土壤的EDOC、ROC、TN和NH_4^+—N/NO_3^-—N均无显著影响。2层土壤的多酚氧化酶活性均随着氮添加量的升高而降低,其中淋溶层表层达到显著差异。模拟氮沉降对蔗糖酶、脲酶和酸性磷酸酶活性均无显著影响。腐殖质层中,NH_4^+—N和NO_3^-—N含量与TOC含量存在极显著正相关关系。2层土壤的多酚氧化酶活性均与NO_3^-—N含量呈极显著负相关。结果说明,模拟氮沉降使该次生林中原本较高的腐殖质层土壤TOC含量进一步显著增加,并且促进土壤无机氮的积累,而模拟氮沉降对多酚氧化酶的抑制作用更加有利于土壤有机质的积累。  相似文献   

20.
Nitrogen (N), ammonium (NH4+) and nitrate (NO3?), is one of the key determinants for plant growth. The interaction of both ions displays a significant effect on their uptake in some species. In the current study, net fluxes of NH4+ and NO3? along the roots of Picea asperata were determined using a Non-invasive Micro-test Technology (NMT). Besides, we examined the interaction of NH4+ and NO3? on the fluxes of both ions, and the plasma membrane (PM) H+-ATPases and nitrate reductase (NR) were taken into account as well. The results demonstrated that the maximal net NH4+ and NO3? influxes were detected at 13–15?mm and 8–10.5?mm from the root apex, respectively. Net NH4+ influx was significantly stimulated with the presence of NO3?, whereas NH4+ exhibited a markedly negative effect on NO3? uptake in the roots of P. asperata. Also, our results indicated that PM H+-ATPases and NR play a key role in the control of N uptake.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号