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 15 毫秒
1.
Land development has caused runoff of red soil into the ocean on the north side of Okinawa Island, Japan. In an attempt to clarify the impacts of this “red soil pollution” on the oxidizing power of seawater, we studied the formation of hydroxyl radical (?OH), the most potent oxidant in the environment, in red soil-polluted waters using a 313-nm monochromatic light. ?OH was photochemically formed in the red soil-polluted water samples, and the formation rates of ?OH decreased as salinity increased, i.e., as red soil-polluted river water gets mixed with seawater. The photo-formation rates of ?OH showed good correlations with dissolved Fe concentrations (R 2?=?0.96) and [NO2 ?]?+?[NO3 ?] concentrations (R 2?=?0.87), while a negative and weak correlation was found with dissolved organic carbon concentrations (R?=??0.78). Theoretical calculation showed that direct photolysis of NO3 ?, Fe(OH)2+, and hydrogen peroxide all together accounted for less than 10% of the observed ?OH formation in the red soil-polluted waters. Comparison between filtered and unfiltered samples showed that red soil particles were not the main sources of ?OH, and the photolysis of NO2 ? could account for at most 78% of the observed ?OH formation rates. We found that the Fenton’s reaction (a reaction between Fe(II) and H2O2) could possibly account for the observed formation of ?OH in the red soil-polluted waters.  相似文献   

2.
In present study, pollutant effects on needle surface characteristics of Pinus sylvestris in the area affected by a nitrogen fertilizer plant have been investigated over 1994–1997 year period. Near the factory, sites with 15–25-year-old trees on a 0.5–22 km interval were chosen. Mean monthly concentrations of NO2 and NH3 varied across the transect in the range of 1.8–8.8 µg m?3 and 1.8 – 69.3 µg m?3, respectively. NH3 concentrations exceeded the critical level (>23 µg m?3) only in the 0.5 km vicinity. Assessment of needle surface wettability by measuring contact angles (CA) of water droplets and surface quality by measuring stomatal area covered by structural wax (SW) revealed significant (p<0.05) needle age, site, and year of sampling related differences. Comparison of SW between sites showed reliably (p<0.05) higher surface wax erosion on one-year-old needles sampled in the area, where ammonia concentration exceeds critical level. Significant correlations between site SW on one-year-old needles and distance from the pollution source, NO2 and NH3 concentrations were detected (r = 0.539; r = ? 0.495; r = ? 0.426; p<0.001, respectively). Correlations between CA and factors mentioned were lower.  相似文献   

3.
The effect of medium-term (5 years) application of organic and inorganic sources of nutrients (as mineral or inorganic fertilizers) on soil organic carbon (SOC), SOC stock, carbon (C) build-up rate, microbial and enzyme activities in flooded rice soils was tested in west coast of India. Compared to the application of vermicompost, glyricidia (Glyricidia maculate) (fresh) and eupatorium (Chromolaena adenophorum) (fresh) and dhaincha (Sesbania rostrata) (fresh), the application of farmyard manure (FYM) and combined application of paddy straw (dry) and water hyacinth (PsWh) (fresh) improved the SOC content significantly (p < 0.05). The lowest (p < 0.05) SOC content (0.81%) was observed in untreated control. The highest (p < 0.05) SOC stock (23.7 Mg C ha?1) was observed in FYM-treated plots followed by recommended dose of mineral fertilizer (RDF) (23.2 Mg C ha?1) and it was lowest (16.5 Mg C ha?1) in untreated control. Soil microbial biomass carbon (Cmb) (246 µg g?1 soil) and Cmb/SOC (1.92%) were highest (p < 0.05) in FYM-treated plot. The highest (p < 0.05) value of metabolic quotient (qCO2) was recorded under RDF (19.7 µg CO2-C g?1 Cmb h?1) and untreated control (19.6 µg CO2-C g?1 Cmb h?1). Application of organic and inorganic sources of nutrients impacted soil enzyme activities significantly (p < 0.05) with FYM causing highest dehydrogenase (20.5 µg TPF g?1 day?1), phosphatase (659 µg PNP g?1 h?1) and urease (0.29 µg urea g?1 h?1) activities. Application of organic source of nutrients especially FYM improved the microbial and enzyme activities in flooded and transplanted rice soils. Although the grain yield was higher with the application of RDF, but the use of FYM as an organic agricultural practice is more useful when efforts are intended to conserve more SOC and improved microbial activity.  相似文献   

4.
The soil nitrogen cycle was investigated for several watershed forests of which stream waters have distinctively different nitrate (NO3 ?) concentrations. In a watershed with stream water NO3 ? of more than 100 µM, soil NO3 ? content increased even beneath the rooting zone, revealing "nitrogen saturation" status. A laboratory soil experiment demonstrated that the proportion of net NO3 ? production to CO2 production was largely regulated by a soil C/N ratio, suggesting a key parameter for NO3 ? abundance. In the respective watershed soils, little nitrogen was actually present as NO3 ? above a soil C/N ratio of 20. The annual mean soil temperature recorded at the sites was correlated with a shift in the C/N ratio in watershed soils (a soil C/N ratio increase of 0.5 per 1°C decrease) along the stream NO3 ? gradient of 30 fold. The results suggest that soil microbial metabolisms affected by C/N ratio may be a direct agent regulating NO3 ? leaching from watersheds under the influence of an atmospheric nitrogen load and climate.  相似文献   

5.
Azaarenes are one of several classes of organic compounds which contain mutagenic and carcinogenic substances that are found in synthetic fuels effluents. This study investigated the potential for a mutagenic azaarene, acridine, to accumulate in freshwater fish (Pimephales promelas) via four possible pathways: (1) direct uptake from water, (2) uptake via interaction with contaminated sediments, (3) uptake via ingestion of contaminated zooplankton (Daphnia pulex), and (4) uptake via ingestion of benthic invertebrates (Chironomus tentans) living in contaminated sediments. The results showed that acridine was rapidly accumulated from water by fathead minnows. Equilibrium concentration was attained within 24 h at a concentration factor ([acridine]fish, wet wt/[acridine]water) of 125±10. Depuration was rapid and appeared to occur in two stages, with a net elimination rate of 0.23 h?1 [acridine]fish at equilibrium. Equilibrium concentration factors of 51±5, 30±2, and 874±275 were observed forChironomus, Daphnia, and sediment, respectively. The calculated rates of uptake of acridine via ingestion of contaminated invertebrates (0.02 μg g?1 h?1) and ingestion of sediment (0.01 μg g?1 h?1) were negligible compared with direct uptake from water (1.40 μg g?1 h?1) in a hypothetical system with all compartments in equilibrium.  相似文献   

6.
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   

7.
Investigations were made on living strains of fungi in a bioremediation process of three metal (lead) contaminated soils. Three saprotrophic fungi (Aspergillus niger, Penicillium bilaiae, and a Penicillium sp.) were exposed to poor and rich nutrient conditions (no carbon availability or 0.11 M d-glucose, respectively) and metal stress (25 µM lead or contaminated soils) for 5 days. Exudation of low molecular weight organic acids was investigated as a response to the metal and nutrient conditions. Main organic acids identified were oxalic acid (A. niger) and citric acid (P. bilaiae). Exudation rates of oxalate decreased in response to lead exposure, while exudation rates of citrate were less affected. Total production under poor nutrient conditions was low, except for A. niger, for which no significant difference was found between the poor and rich control. Maximum exudation rates were 20 µmol oxalic acid g?1 biomass h?1 (A. niger) and 20 µmol citric acid g?1 biomass h?1 (P. bilaiae), in the presence of the contaminated soil, but only 5 µmol organic acids g?1 biomass h?1, in total, for the Penicillium sp. There was a significant mobilization of metals from the soils in the carbon rich treatments and maximum release of Pb was 12% from the soils after 5 days. This was not sufficient to bring down the remaining concentration to the target level 300 mg kg?1 from initial levels of 3,800, 1,600, and 370 mg kg?1in the three soils. Target levels for Ni, Zn, and Cu, were 120, 500, and 200 mg kg?1, respectively, and were prior to the bioremediation already below these concentrations (except for Cu Soil 1). However, maximum release of Ni, Zn, and Cu was 28%, 35%, and 90%, respectively. The release of metals was related to the production of chelating acids, but also to the pH-decrease. This illustrates the potential to use fungi exudates in bioremediation of contaminated soil. Nonetheless, the extent of the generation of organic acids is depending on several processes and mechanisms that need to be further investigated.  相似文献   

8.
Anaerobic ammonium oxidation (anammox process) widely occurs in paddy soil and may substantially contribute to permanent N removal; however, little is known about the factors controlling this process. Here, effects of temperature, pH, organic C, and substrates on potential rate of anammox and the relative contribution of anammox to total N2 production in a paddy soil were investigated via slurry incubation combined with 15N tracer technique. Anammox occurred over a temperature range from 5 to 35 °C with an optimum rate at 25 °C (1.7 nmol N g?1 h?1) and a pH range from 4.8 to 10.1 with an optimum rate at pH 7.3 (1.7 nmol N g?1 h?1). The presence of glucose and acetate (5–100 mg C L?1) significantly inhibited anammox activities and the ratio of anammox to total N2 production. The response of potential rates of anammox to ammonium concentrations fitted well with Michaelis-Menten relationship showing a maximum rate (Vmax) of 4.4 nmol N g?1 h?1 and an affinity constant (Km) of 6.3 mg NH4+-N L?1. Whereas, nitrate addition (5–15 mg 15NO3?-N L?1) significantly inhibited anammox activities and the ratio of anammox to total N2 production. Our results provide useful information on factors controlling anammox process and its contribution to N loss in the paddy soil.  相似文献   

9.
The effects of seven different fertilization treatments on nitrification in the organic horizons of a Myrtillus-type (MT) and a Calluna-type pine forest in southern Finland were studied. No (NO?3 + NO?2)-N accumulated in unfertilized soils during 6 weeks at 14 or 20°C in the laboratory. Net nitrification was stimulated by urea in both soils (but more in the MT pine forest soil) and to a lesser degree by wood ash but not by ammonium nitrate or nitroform (ureaformaldehyde). Nitrification was not detected in nitroform fertilized soils although ammonium accumulation was high during incubation. In the MT pine forest soil, net nitrification appeared to be stimulated by apatite, biotite and micronutrients. Nitrapyrin inhibited nitrification indicating that it was carried out by autotrophic nitrifiers. In the urea-fertilized MT pine forest soil, nitrification took place at an incubation temperature of 0°C. Accumulation of (N0?3 + NO?2)-N was highest in soil sampled at < 10°C.  相似文献   

10.
Inoculation of western red cedar with Paenibacillus polymyxa P2b-2R, an endophytic diazotroph of a pine, was previously shown to result in biological nitrogen fixation (BNF) in seedlings grown under N-limited conditions, but biomass accumulation was reduced after a 9-month growth period. To determine if the seedling growth reduction was temporary, we inoculated cedar seed with strain P2b-2R and grew seedlings for up to 13 months in a N-limited soil mix containing 0.7 mM of available N labeled as Ca(15NO3)2. P2b-2R developed a persistent endophytic population comprising 102–106?cfu g?1 plant tissue inside pine roots, stems, and needles. At the end of the growth period, P2b-2R had reduced 15N foliar N abundance by 36 % and increased shoot biomass by 46 % compared to controls. Our results indicate that inoculated seedlings derived 36 % of foliar N from the atmosphere and suggest that BNF by P. polymyxa can significantly enhance growth of cedar in a N-limited soil if seedlings are grown for a sufficient amount of time. These findings support the hypothesis that endophytic diazotrophs may facilitate regeneration and growth of western red cedar at N-poor sites.  相似文献   

11.
The kinetics of cadmium uptake by Selenastrum capricornutum Printz was studied at 21 °C and 0 °C and at four different concentrations of free cadmium (10?9, 10?8, 10?7 and 10?3 M). The free cadmium concentrations in the medium were kept constant through buffering by a chelating agent (NTA). Initial uptake occurred within 10 min at both temperatures, indicating a fast process. At 21 °C, the cadmium uptake increased during the experimental sampling times from 0.12 to 50 h, whereas at 0 °C, the cadmium uptake remained constant after the first sampling time. Apparently, two different processes were involved in cadmium uptake, a first fast, probably passive process and a second slower, possibly physiological process. The cadmium uptake processes are described with a generalized metalligand complex formation model. The experimental dissociation constants for the fast (K R,F ) and the slow process (K R,S ) were reproducible for different experiments and they were both in the order of 5 10?6 mol L?1. For the slow process, the uptake- and release rate constants (k1 and k2) were quantified; for two experiments, the mean value for ki was 111±28 L mol?1 h?1 and the mean value for k 2 was (5.1±1.8) 10?4 h?1. These values were calculated using the fitted value of the cadmium uptake in the fast process.  相似文献   

12.
The delafossite CuCrO2 is a promising candidate for the visible light driven catalysis. The NO2 ? removal by photoelectrochemical process is studied under mild conditions, close to that encountered in the natural environment. CuCrO2 exhibits a long term chemical stability with a corrosion rate of 0.34 μmol m?2 year?1 in KCl (0.5 M). A forbidden band of 1.3 eV has been evaluated from the diffuse reflectance spectrum. The flat band potential (?0.07 V SCE) determined from the Mott–Schottky plot is close to the photocurrent onset potential (0 V SCE). Hence, the conduction band is positioned at ?1.08 V SCE and thus lies below the NO2 ? level leading to a feasible reduction upon visible illumination. The conversion occurs in less than ～5 h with a quantum efficiency of ～0.5%. The possibility of identifying the reaction products via the intensity–potential characteristics was explored by using standard solutions. The decrease of the conversion rate over time is attributed to the competitive water reduction. In absence of catalyst, NO2 ? is oxidized to NO3 ? in air equilibrated solution and the reaction follows a first order kinetic with a half life of 21 h, NO3 ? has been identified by iodometry through copper titration.  相似文献   

13.
Understanding the temporal distribution of NO3-N leaching losses from subsurface drained ‘tile’ fields as a function of climate and management practices can help develop strategies for its mitigation. A field study was conducted from 1999 through 2003 to investigate effects of the most vulnerable application of pig manure (fall application and chisel plow), safe application of pig manure (spring application and no-tillage) and common application of artificial nitrogen (UAN spring application and chisel plow) on NO3-N leaching losses to subsurface drainage water beneath corn (Zea mays L.)–soybean (Glycine max L.) rotation systems as a randomized complete block design. The N application rates averaged over five years ranged from 166 kg-N ha?1 for spring applied manure to 170 kg-N ha?1 for UAN and 172 kg-N ha?1 for fall applied manure. Tillage and nitrogen source effects on tile flow and NO3-N leaching losses were not significant (P?<?0.05). Fall applied manure with CP resulted in significantly greater corn grain yield (10.8 vs 10.4 Mg ha?1) compared with the spring manure-NT system. Corn plots with the spring applied manure-NT system gave relatively lower flow weighted NO3-N concentration of 13.2 mg l?1 in comparison to corn plots with fall manure-CP (21.6 mg l?1) and UAN-CP systems (15.9 mg l?1). Averaged across five years, about 60% of tile flow and NO3-N leaching losses exited the fields during March through May. Growing season precipitation and cycles of wet and dry years primarily controlled NO3-N leaching losses from tile drained fields. These results suggest that spring applied manure has potential to reduce NO3-N concentrations in subsurface drainage water and also strategies need to be developed to reduce early spring NO3-N leaching losses.  相似文献   

14.
Increasing nitrogen deposition due to human activity might have a serious impact on ecosystem functions such as the nitrogen transformations conducted by microbes. We therefore focused on nitrous oxide (N2O) production as an indicator of soil microbial activity. The rates of N2O emission from the forest floor were measured every two weeks in two forest stands in the central part of Japan: a red pine stand at Kannondai and a deciduous stand at Yasato. Nitrogen deposition rates by throughfall were 30.6 kg N ha?1 y?1 at Kannondai and 15.7 at Yasato. The rates of N2O emission ranged from 0.5 to 14.2 µg N m?2 h?1 (mean 4.5) at Kannondai and from 0.2 to 7.0 µg N m?2 h?1 (mean 2.3) at Yasato. The N2O emission rate showed significant positive relationships with soil temperature and nitrogen deposition during the preceding two weeks. The annual emission rates of N2O were 0.38 kg N ha?1 y?1 at Kannondai and 0.20 at Yasato. As a the annual nitrogen deposition, these rates were 1.23% at Kannondai and 1.27% at Yasato.  相似文献   

15.
Over 60 natural streams with forested catchments were surveyed for nitrate (NO3 ?) concentration in central Japan. Stream NO3 ? concentrations showed a clear zonal gradient with a range nearly as large as 100-fold, where their small seasonal variations (av. CV = 27%) justified respective statuses. Elevated NO3 ? concentrations (more than 70 µM) described a distribution of N saturation along a course of polluted air advection in the Kanto Plain. The extent of NO3 ? leaching from forests was not proportional to atmospheric N deposition probably because of ecosystem N retention. A dependency of NO3 ? level on the watershed altitude and quite constant δ15N of stream NO3 ? over a wide NO3 ? range were observed, which could be also related to this cause.  相似文献   

16.

Purpose

Rice-paddy-dominated watersheds in eastern China are intensively cultivated, and lands with two crops receive as much as 550–600 kg?ha–1?year–1 of nitrogen (N), mainly through the addition of N-based fertilizers. However, stream N concentrations have been found to be relatively low. Waterways in the watersheds are assumed to be effective “sinks” for N, minimizing its downstream movement. We directly measured net sediment denitrification rates in three types of waterways (ponds, streams/rivers, and a reservoir) and determined the key factors that control net sediment denitrification. Such information is essential for evaluating the impact of the agricultural N cycle on the quality of surface water.

Materials and methods

The pond–stream–reservoir continuum was sampled every 2 months at nine sites in an agricultural watershed between November 2010 and December 2011. Net sediment N2 fluxes/net sediment denitrification rates were determined by membrane inlet mass spectrometry and the N2/Ar technique. A suite of parameters known to influence denitrification were also measured.

Results and discussion

Net denitrification rates ranged between 28.2?±?18.2 and 674.3?±?314.5 μmol N2–N?m–2?h–1 for the streams, 23.7?±?23.9 and 121.2?±?38.7 μmol N2–N?m–2?h–1 for the ponds, and 41.8?±?17.7 and 239.3?±?49.8 μmol N2–N?m–2?h–1 for the reservoir. The mean net denitrification rate of the stream sites (173.2?±?248.4 μmol N2–N?m–2?h–1) was significantly higher (p?<?0.001) than that of the pond sites (48.3?±?44.5 μmol N2–N?m–2?h–1), and the three types of waterways all had significantly higher (p?<?0.01) mean net denitrification rates in summer than in other seasons. Linear regression and linear mixed effect model analysis showed that nitrate (NO3 ?–N) concentration in surface water was the primary controlling factor for net sediment denitrification, followed by water temperature. Using monitoring data on NO3 ?–N concentrations and temperature of the surface water of waterways and an established linear mixed effect model, total N removed through net sediment denitrification in the pond–stream–reservoir continuum was estimated at 46.8?±?24.0 t?year–1 from July 2007 to June 2009, which was comparable with earlier estimates based on the mass balance method (34.3?±?12.7 t?year–1), and accounted for 83.4 % of the total aquatic N. However, the total aquatic N was only 4.4 % of the total N input to the watershed, and thus most of the surplus N in the watershed was likely to be either denitrified or stored in soil.

Conclusions

High doses of N in a rice-paddy-dominated watershed did not lead to high stream N concentrations due to limited input of N into waterways and the high efficiency of waterways in removing N through denitrification.  相似文献   

17.
Several fog episodes occurred in California’s San Joaquin Valley during winter 2000/2001. Measurements revealed the fogs to generally be less than 50 m deep, but to contain high liquid water contents (frequently exceeding 200 mg/m3) and large droplets. The composition of the fog water was dominated by ammonium (median concentration?=?608 μN), nitrate (304 μN), and organic carbon (6.9 ppmC), with significant contributions also from nitrite (18 μN) and sulfate (56 μN). Principal organic species included formate (median concentration?=?32 μN), acetate (31 μN), and formaldehyde (21 μM). High concentrations of ammonia resulted in high fog pH values, ranging between 5.8 and 8.0 at the core measurement site. At this high pH aqueous phase oxidation of dissolved sulfur dioxide and reaction of S(IV) with formaldehyde to form hydroxymethanesulfonate are both important processes. The fogs are also effective at scavenging and removal of airborne particulate matter. Deposition velocities for key solutes in the fog are typically of the order of 1–2 cm/s, much higher than deposition velocities of precursor accumulation mode aerosol particles. Variations were observed in deposition velocities for individual constituents in the order NO2 ??>?fogwater?>?NH4 +?>?TOC ～ SO4 2??>?NO3 ?. Nitrite, observed to be enriched in large fog drops, had a deposition velocity higher than the average fogwater deposition velocity, due to the increase in drop settling velocity with size. Species enriched in small fog drops (NH4 +, TOC, SO4 2?, and NO3 ?) all had deposition velocities smaller than observed for fogwater. Typical boundary layer removal rates for major fog solute species were estimated to be approximately 0.5–1 μg m?3 h?1, indicating the important role regional fogs can play in reducing airborne pollutant concentrations.  相似文献   

18.
Abstract

To determine the means and variations in CH4 uptake and N2O emission in the dominant soil and vegetation types to enable estimation of annual gases fluxes in the forest land of Japan, we measured monthly fluxes of both gases using a closed-chamber technique at 26 sites throughout Japan over 2 years. No clear seasonal changes in CH4 uptake rates were observed at most sites. N2O emission was mostly low throughout the year, but was higher in summer at most sites. The annual mean rates of CH4 uptake and N2O emission (all sites combined) were 66 (2.9–175) µg CH4-C m?2 h?1 and 1.88 (0.17–12.5) µg N2O-N m?2 h?1, respectively. Annual changes in these fluxes over the 2 years were small. Significant differences in CH4 uptake were found among soil types (P < 0.05). The mean CH4 uptake rates (µg CH4-C m?2 h?1) were as follows: Black soil (95 ± 39, mean ± standard deviation [SD]) > Brown forest soil (60 ± 27) ≥ other soils (20 ± 24). N2O emission rates differed significantly among vegetation types (P < 0.05). The mean N2O emission rates (µg N2O-N m?2 h?1) were as follows: Japanese cedar (4.0 ± 2.3) ≥ Japanese cypress (2.6 ± 3.4) > hardwoods (0.8 ± 2.2) = other conifers (0.7 ± 1.4). The CH4 uptake rates in Japanese temperate forests were relatively higher than those in Europe and the USA (11–43 µg CH4-C m?2 h?1), and the N2O emission rates in Japan were lower than those reported for temperate forests (0.23–252 µg N2O-N m?2 h?1). Using land area data of vegetation cover and soil distribution, the amount of annual CH4 uptake and N2O emission in the Japanese forest land was estimated to be 124 Gg CH4-C year?1 with 39% uncertainty and 3.3 Gg N2O-N year?1 with 76% uncertainty, respectively.  相似文献   

19.
Under conditions of limited nutrient supply, plant nutrient uptake is controlled by the external concentration of the ions. Limited information exists about the whole-plant regulation of nutrient uptake when the supply is adequate. To study the relationship between growth rate and carbon dioxide (CO2) assimilation with nutrient uptake, growth chamber experiments were conducted with temperatures ranging from 10 to 35°C at medium (600 µmol m?2 s?1) and high (1200 µmol m?2 s?1) light intensities. Nutrient solution samples were collected every 24 hours and the concentration of ions was analyzed by Inductively coupled plasma -atomic emission spectroscopy (ICP-AES) and nitrate and ammonium (NO3?/NH4+) conductivity. Leaf photo-synthesis was measured using a closed gas exchange system and the total amount of CO2 assimilated was calculated from dry weight increases. The daily absorption of NO3?, Total nitrogen (N), dihydrogen phosphate (H2PO4?) and potassium (K+) responded linearly to plant growth, while ammonium (NH4+) and sulfate (SO42?) uptake showed a curvilinear response. All the ions studied showed a curvilinear relation with CO2 assimilation.  相似文献   

20.
Atmospheric air pollution levels and long-term effects on the environment caused by simultaneous presence of SO2 and oil shale alkaline fly ash during the last five decades (since 1950) were investigated. The annual critical value of SO2 for forest (20 µg m?3) was surpassed in 1% (～35 km2) of the study area where the load was 30–40 µg m?3. No effect of long-term SO2 concentrations of up to 10–11 µg m?3 (0.5-h max up to 270 µg m?3) and simultaneous fly ash loads of up to 95 µg m?3 (1000 µg m?3) on the growth and needle longevity of Pinus sylvestris was established. The yearly deposition (average load up to 20–100 kg S ha?1) was alkaline rather than acidic due to an elevated base cation deposition in 1960–1989. Since 1990, the proportion of SO2 in the balance of components increased: about 70–85% of the total area was affected while the ratio of annual average concentrations of SO2 to fly ash was over 1. The limit values of fly ash for Sphagnum mosses and conifers in the presence of SO2 are recommended.  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