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1.
A theoretical model describing the general interaction between atmospheric trace gases, such as S02, NH3, C02 and 02, chemical reactant gaseous product H2SO4 and hydrometeors containing NaCl is proposed to study a possible mechanism for HCl production in non-precipitating cloud and the determination of the pH value of cloud droplets. Four different cloud droplet distributions have been used to estimate the upper limit of the amount of gaseous HCl released into the atmosphere resulting from the evaporation of cloud droplets. It is shown that the acid production and the amount of HCl released depend on the following factors: (a) the temperature of the cloud; (b) the oxidation rates; (c) the ambient concentration of SO2, NH3, and H2SO4; (d) the life cycle of the cloud; and (e) the liquid content of the cloud. This proposed chemical model also predicts a pH value spectrum depending on the cloud droplet distribution. Field measurements for the dependence of pH value on particle size and spatial distribution of gaseous HCl are recommended.  相似文献   

2.

Purpose

Middle-European floodplain soils are often contaminated with mercury (Hg) and periodically flooded. In this study, the influence of a flooding event and subsequent dewatering on the volatilization of elemental Hg and methylated species was investigated in a laboratory experiment.

Material and methods

Undisturbed soil cores were taken from a topsoil (12.1?±?0.75 mg kg?1 Hg) at the Elbe River in Lower Saxony, Germany. Soil columns were incubated at 20 °C with varying soil moisture (water-saturated for 2 weeks, 95 and 90 % water content for 1 week each), and the redox potential (EH) was recorded. The gaseous Hg that accumulated in the headspace of the flux chamber of the columns was pumped over cooled traps filled with adsorber material and analyzed by gas chromatography/inductively coupled plasma mass spectrometry for the various Hg species.

Results and discussion

The watering of the soil resulted in a rapid decrease in the EH and the achievement of strongly reducing conditions (EH??1 Hg at the beginning to 5.78 μg L?1 Hg at the end of the experiment. Species analyses revealed that exclusively elemental Hg volatilized. The volatilization rate was between 1.73 and 824 ng m?2 h?1 Hg, which is consistent with other studies at the Elbe River.

Conclusions

Even when flooded for a longer period of time, floodplain soils should show neither emission of methylated Hg nor exceptionally high volatilization of elemental Hg.  相似文献   

3.
The determination of low levels of Pb via hydride generation and measure by AAS is studied. It is found that the presence of an acidic medium (HCl 0.12M) and an oxidizing agent (4 mL of 7%) (M/V) H2O2 is necessary to generate PbH4, independently of the oxidation state of Pb, and using as reducing agent a solution of NaBH4 7.5%. The role of the oxidizing agent is discussed. A method is proposed for the determination of Pb present on filters for sampling of the ambient atmosphere. A standard deviation of 0.0195 and RSD 2.45% a level of 1 μg mL?1 of Pb was observed.  相似文献   

4.
Activated C is a useful medium for simultaneous sampling of trace gases. However, preferential canals in the C cartridge and water vapor condensation should be avoided. The most critical component is metallic Hg. Based on the principle of permeation, a Hg calibration gas was prepaired with a concentration range between 4 and 300 μg·m?3. The collection efficiency of Hgo on activated C as a function of temperature and flow was studied. It appeared that the residence time (flow) and temperature should be carefully chosen. The collection efficiency decreases at increasing temperature and increasing flow. Hg adsorption in tubes, plane filters, in-depth filters and thimble filters was also investigated. Based on the results obtained a sampling train is made for sampling flue gases. The same train can also be used for sampling ambient air.  相似文献   

5.
An increased understanding of ion-exchange processes in raw-humus was obtained by simulations using quantitative mathematical models. The work is based on a series of percolation experiments with a water flow of about 1 mm min?1 through raw-humus samples of 4 cm thickness. For the input solutions consisting of 10?3 N H2SO4, HNO3, HCl and NaCl the results indicate that cation-exchange reactions are the most important processes for the chemical composition of the run-off. Since a large part of the water flows quickly through the soil, both the water residence time and the ion-exchange kinetics must be taken into account. As a basis for the chemical model, a hydrologic sub-model reproducing the residence time distribution of the flow in the soil is used. Considering the ions H+, M+ (monovalent metal ions) and M2+ (divalent metal ions), four different chemical models were tried but only one of them gave satisfactory agreement with the experimental results. This model has 5 independent parameters and consists of first and second order chemical processes.  相似文献   

6.
Duplicate, 8-compartment, continuous-flow microcosms were used to study the effects of acid addition on community function, algal community structure, and degradation of a plasticizer, diethyl phthalate. Inputs of HCl decreased the alkalinity (measured as CaC03) from 25 to 8 mg 1?1, creating diurnal H+ activity curves that indicated that the ecosystem was being severely stressed. Removal of excess acid was accompanied by a return to a normal diurnal pH cycle. Nutrient concentrations and O2 production did not give a definite indication of stress resulting from the addition of acid. Algal community structure and total biomass were not affected by acid inputs. Also, degradation rates of diethyl phtalate by the aquatic bacteria were similar for the control and the acid-stressed systems. These studies indicate that acid inputs can significantly disrupt normal ecosystem function, such as diurnal pH cycling, without having a measurable impact on other parameters usually monitored in aquatic ecosystems.  相似文献   

7.
Between December 1986 and June 1987, the mean pH of rainfall downwind of the Kilauea main vent was found to be 4.5 (range 4.0 to 5.6), 1.2 units higher than the year before (1985-86), although 84% of the 12 sequential samples fell below pH 5.0. The SO4 content, however, was 34% higher, averaging 18.5 mg L?1. Upwind, in open forest the mean pH 4.7 was little changed from that measured before. Mean SO4, however, has fallen to a low of 2.5 mg L?1, but, more significantly, in 9 out of 12 sequential samples S04 was not detectable at all (i.e. < 0.5 mg L?1). The calculated pH, assuming 100% H2SO4 would be 5.3 yet 58% of these samples fell below pH 5.0, the lowest being 4.0. Disparities between pH measured and calculated on the basis of SO4 content indicated that other acid species were present in the precipitation. Oxidation of rain samples with H2O2 greatly increased SO4 content and lowered pH downwind, but failed in most samples to alter either parameter in the upwind collections. These observations, together with the elimination of HCl and N03 by others, suggested that SO2 contributes significantly to acidity downwind, but that in most upwind samples a source of H+ other than mineral acids, presumably organic compounds, must be of major importance.  相似文献   

8.

Purpose

In view that soils are bodies and that processes such as storage and release of water, carbon, nutrients and pollutants, and aeration and rooting happen in these bodies, it is of interest to know the density of elements and compounds in soils. On the basis of soil bulk and element density of organic carbon (OC), N, and heavy metals in soils and of horizon thickness, stocks of these elements for garden soils were calculated.

Materials and methods

Fourteen gardens in four allotments of the northwestern part of the Ruhr area, Germany were investigated. The research included 14 vegetable patches, 13 lawns, 2 compost heaps, and 1 meadow. Volume samples were taken. The soil analysis included pH, soil bulk density, and OC, N, Pb, Cd, Zn, Cu, and Ni contents.

Results and discussion

The soils were from sandy loam to loamy sand. The pH was slightly acid and C/N ratio about 20. Soil bulk density was between 0.8 and 1.4 g cm?3 and mean bulk density was 1.1 g cm?3. Mean OC content was for compost 7.4 %, vegetable patches 5.2 % (0–30 cm depth), and lawns and meadow 5.8 and 5.2 % (0–5 cm depth). OC density for compost was 76 mg cm?3, vegetable patches 56 mg cm?3, and lawns 67 mg cm?3 (0–5 cm). Mean OC stock in 0–30 cm soil depth in vegetable patches was 16.4 kg m?2, lawns 15.5 kg m?2, and meadow 11.1 kg m?2. N contents were between 0.06 and 0.46 %. For compost, the mean was 0.39 %, vegetable patches 0.27 % (0–30 cm), lawn 0.28 %, and meadow 0.26 % (0–5 cm). Mean stock of N in 0–30 cm depth for vegetable patches was 0.84 kg m?2, lawn 0.76 kg m?2, and meadow 0.55 kg m?2. For heavy metals in compost, vegetable patches, lawn and meadow, Cd contents were in the range of 1.7 to 3.0 mg kg?1, Pb 49 to 152 mg kg?1, and Zn 52 to 1830 mg kg?1. The amounts stored per square meters in 30 cm depth were for Cd 0.6–1.1 g, Pb 15–52 g, Zn 41–440 g, Cu 4–39 g, and Ni 1–8 g.

Conclusions

Allotment gardens have a high capacity to store CO2 as OC. Roughly, there will be 7–8 million tons of OC stored in the 1.3 million allotment gardens of Germany. The high amount of 8000 kg N ha?1 could damage the groundwater when released by wrong soil management. Cd, Zn, Pb, Cu, and Ni amounts of 7.8, 1000, 300, 135, and 30 kg ha?1, respectively, are a lasting burden.
  相似文献   

9.
When balancing the element mercury (Hg) two coal-fired power plant units — one with slag tap boilers (ST, 2 × 220 MW) and one with a dry bottom boiler (DB, 475 MW) were compared. Both systems are provided with electrostatic precipitators (ESP), nitrogen oxides removal (DeNOx) and flue gas desulfurization (FGD) systems. The Hg in the flue gas is predominantly in gas phase. Only 15 % of the Hg introduced by the coal leaves the unit with the bottom or fly ash. Depending on the operating mode, 30 to 40 % of the Hg is separated in the FGD systems. The overall separation rate for the total system ranges between 45 to 55 %, the residue is emitted in the form of gaseous Hg species. At full load, the Hg concentration in the cleaned gas is less than 6 μg/m3. In the flue gas path of another dry bottom boiler (DB1, 480 MW) the concentrations of the gaseous species of bivalent mercury (Hg2+), elemental mercury (Hg0), and total mercury content (Σ Hg) were determined. The sum of the concentrations of Hg2+ and Hg0 is in agreement with the measurement of Σ Hg. Directly downstream of the boiler Hg2+ dominates with 77 %, while Hg0 amounts to 23 %. In the high-dust DeNOx system Hg0 is oxidized almost completely to Hg2+ (96 %). Air heater and electrostatic precipitator do not influence the Hg species concentrations. The FGD system eliminates approximately 80 % of the Hg2+. At the same time the quantity of Hg0 increases by the factor 10. In the cleaned gas Hg0 dominates with 76 % as compared to Hg2+ with 24 %. At full load the concentration of Σ Hg in the cleaned gas is also below 6 μg/m3.  相似文献   

10.
The contamination of hazardous metal(loid) is one of the serious environmental and human health risks. This study isolated a total of 40 cadmium (Cd)- and arsenic (As)-resistant bacterial isolates from coastal sediments by pour plate technique using tryptic soy agar supplemented with Cd or As (50 mg l?1) for use as metal(loid) bioremediation agents. Out of 40, 4 isolates, RCd3, RCd6, RAs7, and RAs10, showed a relatively higher growth rate in Cd- or As-supplemented culture media which were selected for further study. The selected isolates showed a high minimum inhibitory concentration (60–400 mg l?1 for Cd and 400–2200 mg l?1 for As), which demonstrated their remarkable Cd and As resistance capabilities. The metal(loid) removal efficiencies (0.032–0.268 μg Cd h?1 mg?1 and 0.0003–0.0172 μg As h?1 mg?1 [wet weight cell]) of selected isolates indicated their greater magnitude in absorbing Cd compared to As from water. Phylogenetic analysis of the 16S rDNA sequences revealed that isolates RCd3, RCd6, RAs7, and RAs10 were closely related to Acinetobacter brisouii, Pseudomonas abietaniphila, Exiguobacterium aestuarii, and Planococcus rifietoensis, respectively. Because of high Cd and As resistance and removal efficiency, the selected isolates can survive in a high metal(loid)-contaminated environment and could be a potential tool for bioremediation of high metal(loid)-contaminated effluents to protect the aquatic environment.  相似文献   

11.
Relativistic quantum calculations at the CASSCF- and CCI-levels were performed on the Hg(SH)2, HgSH and HgS molecules. The relativistic effects were taken into account by a relativistic effective core potential method. Dissociation energies and optimal geometries were calculated for these three molecules, which are plausible atmospheric Hg compounds. The Hg(SH)2 and HgSH molecules (in the gaseous phase) have never been studied before, neither experimentally nor theoretically, i.e. the existence of these molecules are uncertain. The theoretical dissociation energies, De's, of Hg(SH)2 and HgSH (at the CCI-level) were 59 kcal·mol?1 and 3 kcal·mol?1, respectively, indicating that Hg(SH)2 could be stable in the atmosphere but probably not HgSH. The theoretical De of HgS differs very much from the experimental one, but the reason for this is not clear. The Hg-S distances for Hg(SH)2, HgSH and HgS were found to be 2.38, 2.63 and 2.30 Å, respectively. The Hg-S-H angle in Hg(SH)2 was optimized to 93°. The excitation energies of Hg(SH)2, Hg(SH)2(H2O)4 and (HSHg)2S were calculated in order to see whether these species can absorb photons with wavelengths longer than 290 nm (the sunlight limit) and subsequently be photolyzed. The Hg(SH)2(H2O)4 complex is intended as a model for Hg(SH)2(aq). Photoreduction of Hg-sulfide species in sea water, yielding Hg0, could be an important source of Hg in the atmosphere. Excitation energies lower than the sunlight limit (4.3 eV≈290 nm) were found for Hg(SH)2 and Hg(SH)2(H2O)4, although the lowest spin and dipole allowed excitations probably lie slightly (0.2 to 0.3 eV) above this limit. Therefore a photodecomposition of Hg(SH)2(g) and Hg(SH)2(aq) by sunlight seems likely to occur.  相似文献   

12.
This paper reports the dissolved and particulate trace metal distributions in Lake Mikri Prespa, wetland of NW Greece. The concentrations of Cu, Pb, Zn, Cd, Al, Fe, Mn, Ni and Cr were determined in surface and hypolimnetic waters as well as in the inputs and the outflow. Trace metals were connected with two major populations of suspended particles, identified by using the recovery ratio for two different leaching reagents, namely 0.5 N HCl and 1:1 hot aqueous HNO3. The first group is land derived entering the lake through runoff and plays a rather restricted role in its geochemistry. The second group which is more important includes authigenic carbonates, Fe and Mn hydroxides and oxides and organic rich particulates.  相似文献   

13.
Ten soils were leached with a dilute solution of AICI3, and FeCl2 adjusted with HCl to pH 3.0. The effluents were analyzed for eight trace metals as well as pH, to determine the maximum contribution of the soils to the trace metal burden of the soil solution. This contribution was correlated with various soil properties to evaluate the controlling factors on the elution of certain metals. Measurable quantities of Mn, Co, Zn, Ni, Cu, and Cr were found in the soil leachates; Cd and Pb were infrequently detected. The important soil properties describing the amounts of the elements leached were the total metal originally present, the total amount of Mn, and the percentage of free iron oxides.  相似文献   

14.
The investigation of SO2, NO2, soot and benzo(a)pyrene (BP) has been performed at the background station on the eastern coast of the Baltic Sea since 1980. A significant decreasing trend has been observed for SO2 and NO2, while soot and BP concentrations were changing insignificantly. The decreasing SO2 and NO2 high concentrations (>10µg·m?3) have been determined in the air masses coming from the Western and Central Europe to Lithuania since 1900. The concentration of SO2 in a range of 0–5µg·m?3 and the concentration of NO2 in a range of 0–10µg·m?3 are characteric of the background atmospheric air.  相似文献   

15.
小麦/玉米/大豆带状套作是四川省丘陵低山区主要旱地作物生产体系,了解该体系磷养分变化对优化磷肥管理和促进可持续生产有重要意义。本研究通过连续3年(2011—2013年)田间定位试验,设置P0、P1、P2、P3和P4共5个磷(P2O5)水平(玉米带分别为0 kg·hm-2、37.5 kg·hm-2、75 kg·hm-2、112.5 kg·hm-2、150 kg·hm-2,小麦-大豆带分别为0 kg·hm-2、45 kg·hm-2、90 kg·hm-2、135 kg·hm-2、180 kg·hm-2),探讨该体系中土壤全磷、速效磷、水溶性磷的变化规律和速效磷的年际变化。结果表明:在麦/玉/豆套作体系中施磷165 kg(P2O5)·hm-2(玉米带75 kg·hm-2,小麦-大豆带90 kg·hm-2),可以满足体系作物对磷的需求,基本达到磷的表观平衡,维持土壤速效磷含量在20 mg·kg-1左右。3年后5个磷水平下体系耕层土壤(0~20 cm)全磷变化量分别为-0.024 g·kg-1·a-1、-0.016 g·kg-1·a-1、0.016 g·kg-1·a-1、0.11 g·kg-1·a-1、0.15 g·kg-1·a-1,速效磷变化量依次为-1.2 mg·kg-1·a-1、-0.9 mg·kg-1·a-1、0.2 mg·kg-1·a-1、2.0 mg·kg-1·a-1和2.7 mg·kg-1·a-1。通过线性平台函数的模拟,该体系中玉米、小麦、大豆产量的土壤速效磷临界值分别为16.5 mg·kg-1、12.6 mg·kg-1和8.8 mg·kg-1。当土壤全磷含量低于0.55 g·kg-1时,土壤全磷每增加0.1 g·kg-1,土壤速效磷增加1.70 mg·kg-1;当土壤全磷大于0.55 g·kg-1,全磷每增加0.1 g·kg-1,土壤速效磷增加6.49 mg·kg-1。当土壤速效磷含量在40 mg·kg-1以下时,速效磷每增加1 mg·kg-1,水溶性磷增加0.017 mg·kg-1。综上,在麦/玉/豆体系磷肥管理中应该维持土壤全磷含量低于0.55 g·kg-1,同时速效磷含量在20 mg·kg-1左右,这样既可以保证作物产量和系统生产力又不会产生较大的环境威胁。  相似文献   

16.
The hydrobiological parameters of the waters in the vicinity of ash slurry and cooling water outfall from Ennore Thermal Power Station located on the shore of Bay of Bengal, Madras were determined. In the outfall site, an increase in mean temperature (35 °C), salinity (3.5%), nitrite ? N (25 μg L?1), ammonia ? N (185 μg L?1), phosphate ? P (1 mg L?1), silicate ? SiO2 (1.65 mg L?1), chlorophyll a (21.1 mg m?3), respiration (76% of gross production), suspended solids (3.84 g L?1), BOD (3.65 mg O2) and decrease in pH (8.1), dissolved oxygen (DO) (5.5 mg L?1), nitrate ? N (15 jig L?1), gross production (16.6 Mg C m?3 hr?1) were recorded. Phaeopigment and respiration were inversely related with chlorophyll a and net productivity, respectively. Microbial biomass varied spatially, but was generally low (114.5 jig L?1), at the outfall site. The hydrobiological characteristics of water with high turbidity indicate that the ash slurry and coolant water play a crucial role in a localized area resulting in environmental disturbance. The effect was profoundly influenced by an initial dilution, dispersion, wave mixing and current direction. The ecological relationships between these parameters and their implications in coastal pollution are discussed.  相似文献   

17.
Laboratory-scale models consisting of a simple upflow anaerobic sludge blanket reactor (UASBR) and an upflow anaerobic filter (UAF) in series were subjected to organic loadings of 0.19 to 0.55 kg COD m?3 d?1 at 20°C. COD and SS removals were 95 to 98% and 98 to 99%, respectively. Biogas produced by the system amounted to 0.31 to 0.32 m3 CH4 kg?1 COD removed. The UASBR was more stable than the UAF in performance. No sign of deterioration in final effluent quality was observed during 420 days of operation under low loading.  相似文献   

18.
The establishment of a complementary grass cover on vineyard soils can promote sustainability of the affected environment. In this work, we used an acid vineyard soil with total Cu concentration 188 mg kg?1 to study the influence of pine bark amendment on Lolium perenne growth and Cu uptake. The results indicate that the pine bark amendment did not cause a significant increase in the mass of the shoots of Lolium perenne, but favored the root biomass: 0.034 g for control and 0.061 g for soil samples amended with 48 g kg?1 of pine bark. Moreover, the pine bark amendment decreased Cu concentration in both, shoots (50 mg kg?1 for control soil and 29 mg kg?1 for soil amended with 48 g kg?1 pine bark) and roots (250 mg kg?1 for control soil and 64 mg kg?1 for soil amended with 48 g kg?1 pine bark). The main factor responsible for these results was a significant decrease of the most mobile fractions of Cu in the soil. Those fractions were extracted using ammonium acetate, ammonium chloride, sodium salt of ethylene-diamine-tetraacetic acid (EDTA-Na), and diethylene-triamine-pentaacetic acid (DTPA).  相似文献   

19.
Litter decomposition was studied at two forested watersheds in east Tennessee which differed primarily in their past history of atmospheric S input. Cross Creek Watershed, located near a large coal-fired power plant, has received greater S inputs than the more remote Camp Branch Watershed. Decomposition was estimated through the measurement of forest floor respiration, litter microflora populations, litter and soil microarthropod populations, and litter nutrient status. Average forest floor respiration rates were very similar, 6.78 g CO2 m?2 day?1 or 2472 g m?2 yr?1 at Camp Branch and 6.86 g CO2 m?2 day?1 or 2505 g M?2 yr?1 at Cross Creek. Fractional loss rates provided estimates of annual decay rates (k) of 0.35 and 0.39 for Camp Branch and Cross Creek, respectively. Litter decomposition was estimated to contribute 23% of the total CO2 output at Camp Branch and 26% at Cross Creek, while root respiration accounts for about 43 to 46%. Bacterial and fungal populations were about equal in size at both watersheds, with bacteria averaging 100 × 106 g?1 of litter and fungi 23 × 106 g?1 of litter. Total numbers of arthropods averaged 34% greater at Camp Branch. Acarina populations averaged 59% higher at Camp Branch, while Collembola numbers were about equal at the two watersheds. Nutrient mobility in the litter and soil was similar at both watersheds. The order of decreasing mobility was K, Mg, Ca, S, N, and P. Litterfall nutrient concentrations were slightly higher for all elements at Cross Creek, resulting in greater litter concentrations of Ca and Mg. Litter concentrations of S and N, however, were significantly greater at Camp Branch, indicating watershed differences in the loss rates and cycling processes of these elements. There were no differences between the loss rates or litter concentrations of P, K, and Na at either site. Overall, decomposition was similar at the two watersheds. Historic S inputs do not appear to have had a major effect on decomposition rate or decomposer organisms with the possible exception of lowered arthropod populations at Cross Creek.  相似文献   

20.
Total Hg and McHg concentrations have been determined in sediments and suspended particulate matter from one of the most Hg-polluted rivers of the world, the Elbe river in Northern Germany. Results of total Hg and McHg are presented. Total Hg concentrations in suspended particulate matter (SPM) are 30 mg kg?1 in the average and up to 150 mg kg?1 as the maximum value. Total Hg-fluxes ?1 calculated from measurements of an automatically operating station upstream Hamburg as about 17 ta?1 in suspended particles. A new McHg determination by HPLC chromatography and photometric detection was developed and verified. Methylmercury concentrations were up to 10% of the total Hg, i. e. 2.7 mg kg?1 (dw).  相似文献   

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