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1.
The sampling and analysis properties of 1-stage and 2-stage filter-pack methods were studied in detail in monitoring of sulphur and nitrogen containing inorganic gases and particles (sulphur dioxide, sulphate, sum of nitric acid and nitrate and total ammonium). The limit of detection and the limit of quantitation for 24-h samples were estimated using the results of a short-term field experiment completed with available data from long-term monitoring and internal quality assurance. Furthermore, the combined expanded measurement uncertainty including sampling and analysis (Utot) was estimated for filter-pack methods in order to give a tool for distinguishing long-term trends in air quality from the measurement variability. Utot was found to be very near the analytical uncertainty when measuring higher air concentration levels, being ± 4.0% for sulphur concentrations?>?1.0 μg m?3, ± 3.0% for sulphate concentrations?>?0.5 μg m?3, ± 3.5% for the sum of nitrate and nitric acid concentrations?>?0.3 μg m?3 and ± 4.5% for total ammonium concentrations?>?0.8 μg m?3. At the lower air concentration range Utot increases significantly due to the field blank values. The precision of the 24-h filter-pack sample results expressed by means of modified median absolute difference (M.MAD) and coefficient of variance (CoV) gave 8.3% for sulphur dioxide and 5.4% for particulate sulphate. For the sum of gaseous nitric acid and particulate nitrate the CoV was 5.5% and for total ammonium 4.3%. In addition the suitability of the 24-h filter-pack methods in weekly sampling was proved.  相似文献   

2.
An inverse relationship has been observed between pH and McHg concentration in freshwater fish. Many hypotheses exist regarding the mechanisms which lead to elevated levels of organic Hg in fish from low pH lakes. To determine if pH has a direct effect on the rate of McHg bioaccumulation in fish, rainbow trout fingerlings (Oncorhynchus mykiss) were exposed to a low concentration of aqueous methylmercuric chloride (1.38 ± 0.49 ng·L?1) at four pH-levels (8.2, 7.0, 6.3, 5.8) for eight weeks. McHg and total Hg were specifically determined on whole fish homogenates and water samples. The pH was found to have a significant: inverse effect on the rate of McHg bioaccumulation in the fish only in the lowest exposure level. Fish held at pH 5.8 had an uptake rate of 1.11 ± 0.07 ng·g?1·d?1, while those at pH ≥ 6.3 had a MeHg tissue uptake rate of ≤ 0.64 ± 0.07 ng·g?1·d?1. Total body burden of MeHg in the fish held at pH 5.8 also showed an elevated level of MeHg when compared with fish held at higher pH-levels, but the difference was less dramatic. These results suggest that a portion of the Hg burden in fish from low pH systems may be due to the direct effects of low pH on bioaccumulation, but that a threshold may exist above which pH does not play a significant role.  相似文献   

3.
为了研究黄淮海平原不同秸秆还田方式和施氮类型对夏玉米农田生态系统土壤呼吸的影响,于2010年6—10月,采用LI-COR-6400-09土壤气室连接红外线气体分析仪(IRGA)对玉米农田行间掩埋秸秆区的土壤呼吸作用进行了连续测定。结果表明,常规施肥下,玉米生育期内秸秆行间掩埋处理(ISFR)的平均土壤呼吸速率显著高于秸秆移除(NSFR)和秸秆覆盖(SFR)处理(P<0.05)。秸秆行间掩埋配合施用化学氮肥处理中,配施50.4 kg(N).hm 2处理(ISF3)的平均土壤呼吸速率为(178.85±46.60)mg(C).m 2.h 1,显著高于配施33.6 kg(N).hm 2处理(ISF2)的(124.11±23.18)mg(C).m 2.h 1(P<0.05)。秸秆行间掩埋配合施用鸡粪处理中,鸡粪施用量为33.6kg(N).hm 2(ISOM2)处理的平均土壤呼吸速率为(208.08±31.54)mg(C).m 2.h 1,施用16.8 kg(N).hm 2(ISOM1)和50.4 kg(N).hm 2(ISOM3)处理的为(135.07±21.97)mg(C).m 2.h 1、(171.43±43.31)mg(C).m 2.h 1,相比ISOM2处理,ISOM1和ISOM3处理的平均土壤呼吸速率降低了35.09%和17.61%。ISOM2处理玉米季CO2排放累积量为499.39 g(C).m 2,显著高于ISF2处理的297.86 g(C).m 2。秸秆行间掩埋配合施用化学氮肥对土壤呼吸速率的影响小于配合施用鸡粪的影响,配合施用16%总氮的鸡粪,即33.6 kg(N).hm 2时C/N比最适宜土壤微生物的代谢活动。  相似文献   

4.
Abstract

To evaluate the hypothesis that plant-mediated oxygen supplies decrease methane (CH4) production and total global warming potential (GWP) in a tropical peatland, the authors compared the fluxes and dissolved concentrations of greenhouse gases [GHGs; CH4, carbon dioxide (CO2) and nitrous oxide (N2O)] and dissolved oxygen (DO) at multiple peatland ecosystems in Central Kalimantan, Indonesia. Study ecosystems included tropical peat swamp forest and degraded peatland areas that were burned and/or drained during the rainy season. CH4 fluxes were significantly influenced by land use and drainage, which were highest in the flooded burnt sites (5.75 ± 6.66 mg C m?2 h?1) followed by the flooded forest sites (1.37 ± 2.03 mg C m?2 h?1), the drained burnt site (0.220 ± 0.143 mg C m?2 h?1), and the drained forest site (0.0084 ± 0.0321 mg C m?2 h?1). Dissolved CH4 concentrations were also significantly affected by land use and drainage, which were highest in the flooded burnt sites (124 ± 84 μmol L?1) followed by the drained burnt site (45.2 ± 29.8 μmol L?1), the flooded forest sites (1.15 ± 1.38 μmol L?1) and the drained forest site (0.860 ± 0.819 μmol L?1). DO concentrations were influenced by land use only, which were significantly higher in the forest sites (6.9 ± 5.6 μmol L?1) compared to the burnt sites (4.0 ± 2.9 μmol L?1). These results suggest that CH4 produced in the peat might be oxidized by plant-mediated oxygen supply in the forest sites. CO2 fluxes were significantly higher in the drained forest site (340 ± 250 mg C m?2 h?1 with a water table level of ?20 to ?60 cm) than in the drained burnt site (108 ± 115 mg C m?2 h?1 with a water table level of ?15 to +10 cm). Dissolved CO2 concentrations were 0.6–3.5 mmol L?1, also highest in the drained forest site. These results suggested enhanced CO2 emission by aerobic peat decomposition and plant respiration in the drained forest site. N2O fluxes ranged from ?2.4 to ?8.7 μg N m?2 h?1 in the flooded sites and from 3.4 to 8.1 μg N m?2 h?1 in the drained sites. The negative N2O fluxes might be caused by N2O consumption by denitrification under flooded conditions. Dissolved N2O concentrations were 0.005–0.22 μmol L?1 but occurred at < 0.01 μmol L?1 in most cases. GWP was mainly determined by CO2 flux, with the highest levels in the drained forest site. Despite having almost the same CO2 flux, GWP in the flooded burnt sites was 20% higher than that in the flooded forest sites due to the large CH4 emission (not significant). N2O fluxes made little contribution to GWP.  相似文献   

5.
Significance of microbial biomass and non-exchangeable ammonium with respect to the nitrogen transformations in loess soils of Niedersachsen during the growing season of winter wheat. I. Change of pool sizes Nitrogen transformations in loess soils have been examined by laboratory and field experiments. After straw application (· 8 t · ha?1), N in microbial biomass (Nmic) increased by about 20 mg · kg?1 soil (· 90 kg N · ha?1 · 30 cm?1) after 9 days of incubation (20 °C). Another laboratory experiment yielded an increase of about 400 mg of NH4+-N · kg?1 fixed by minerals within 1 h after addition of 1 M NH4+-acetate. Defixation of the recently fixed NH4+ after addition of 1 M KCl amounted to only 60 mg · kg?1 within 50 days. In a field experiment with winter wheat 1991, an increase in Nmic of about 80 kg N · ha?1 · 30 cm?1 was observed from March to June. After July, growth of the microbes was limited by decreased soluble carbon concentrations in the rhizosphere. Different levels of mineral N-fertilizer (0, 177 and 213 kg N · ha?1) did not affect significantly the microbial biomass. The same field experiment yielded a decrease of non-exchangeable ammonium on the “zero”-fertilized plot in spring by 200 kg N · ha?1 · 30 cm?1. The pool of fixed ammonium increased significantly after harvest. After conventional mineral N-fertilizer application (213 kg N · ha?1). NH4+-defixation was only about 120 kg N · ha?1 · 30 cm?1 until July.  相似文献   

6.
Particulate matter measurements (PM10, PM2.5) using a beta radiation attenuation monitor were performed at the Akrotiri research station (May 2003–March 2006) on the island of Crete (Greece). The mean PM10 concentration during the measuring period (05/02/03–03/09/04) was equal to 35.0?±?17.7 μg/m3 whereas the mean PM2.5 concentration (03/10/04–04/02/06) was equal to 25.4?±?16.5 μg/m3. The aerosol concentration at the Akrotiri station shows a large variability during the year. Mean concentrations of particulate matter undergo a seasonal change characterised by higher concentrations during summer [PM10, 38.7?±?10.8 μg/m3 (2003); PM2.5, 27.9?±?8.7 μg/m3 (2004) and 27.8?±?9.7 μg/m3 (2005)] and lower concentrations during winter [PM10, 28.7?±?22.5 μg/m3 (2003/2004); PM2.5, 21.0?±?13.0 μg/m3 (2004/2005) and 21.4?±?21.9 μg/m3 (2005/2006)]. Comparative measurements of the PM10 concentration between the beta radiation attenuation monitor, a standardized low volume gravimetric reference sampler and a low volume sequential particulate sampler showed that PM10 concentrations measured by the beta radiation attenuation monitor were higher than values given by the gravimetric samplers (mean ratio 1.17?±?0.11 and 1.21?±?0.08, respectively). Statistical and back trajectory analysis showed that elevated PM concentrations (PM10, 93.8?±?49.1 μg/m3; PM2.5: 102.9?±?59.9 μg/m3) are associated to desert dust events. In addition regional transport contributes significantly to the aerosol concentration levels whereas low aerosol concentrations were observed during storm episodes.  相似文献   

7.
Radon levels in two old mines in San Luis, Argentina, are reported and analyzed. The radiation dose and environmental health risk of 222Rn concentrations to both guides and visitors were estimated. CR-39 nuclear track detectors were used for this purpose. The values for the 222Rn concentration at each monitoring site ranged from 0.43?±?0.04 to 1.48?±?0.12 kBq m?3 in the Los Cóndores wolfram mine and from 1.8?±?0.1 to 6.0?±?0.5 kBq·m?3 in the La Carolina gold mine, indicating that, in this mine, the radon levels exceed up to four times the action level of 1.5 kBq m?3 recommended by the International Commission on Radiological Protection. The patterns of the radon transport process revealed that the La Carolina gold mine can be interpreted as a gas confined into a single tube with constant cross-section and air velocity. Patterns of radon activity, taking into account the chimney-effect winds, were used to detect tributary currents of air from shafts or larger fissures along the main adit of the Los Cóndores mine, showing that radon can be used as an important tracer of tributary air currents stream out from fissures and smaller voids in the rock of the mine.  相似文献   

8.

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   

9.
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   

10.
Phosphorus, manganese, sulfur (S), lead, and strontium of atmospheric total suspended particulate matter, sampled during the rainy season and the dry season 2002 at the Ilha Grande Island (Rio de Janeiro State, Brazil) have been analyzed by XRF techniques. The results showed total mean concentrations of 27?±?16 ng P m-3, 11?±?7 ng Mn m-3, 159?±?126 ng S m-3, 4.3?±?2.6 ng Pb m-3, and 208?±?148 ng Sr m-3. Generally, there is no clear influence of the two different climatic periods on the concentrations of most analyzed trace elements, with exception of sulfur the mean concentration of which, during the dry season, is about 60% higher than during the rainy season. This is probably due to biomass burning, a common practice in the Brazilian Southeast and Amazon region and/or to the presence of marine aerosols. The linear correlation coefficients strongly suggest the same source for P, Pb, and Mn. Some Pb, Mn, and P concentrations are in the range of typical values of urban areas. Potential sources of such elements are the urban and industrial emissions from the States of Rio de Janeiro and/or São Paulo.  相似文献   

11.
A field experiment was carried out to evaluate the effect of two whole-crop rice (Oryza sativa L.) cultivars, TULT and Takanari, on methane (CH4) emission in a paddy field fertilized with biogas slurry (BS) at rates of 0 (NF), 100 (BS100) and 300 (BS300) kg nitrogen (N) ha?1, in comparison with chemical fertilizer CF100 (100 kg N ha?1). Takanari produced significantly higher biomass (P < 0.001) than TULT and showed significantly (P < 0.01) lower CH4 emission than TULT. BS applications caused higher CH4 emission (52 ± 27 and 80 ± 19 g m?2 in BS100 and BS300, respectively) than did CF100 (42 ± 18 g m?2) and NF (28 ± 10 g m?2) in TULT. In contrast, there was no significant difference in CH4 emission in Takanari among the treatments (26 ± 2, 26 ± 2, 32 ± 4, 29 ± 8 g m?2 in NF, CF100, BS100 and BS300, respectively). Methane oxidizing bacteria (MOB) showed significantly (P < 0.05) higher populations in Takanari than in TULT at harvest, which might be due to the higher root biomass (10.3 ± 2.2 g hill?1) in Takanari than in TULT (8.9 ± 1.8 g hill?1). MOB was significantly correlated with tiller number (R2 = 0.176*) and plant biomass (R2 = 0.242*). BS application showed higher copper (Cu) uptake in Takanari while it was not high in TULT. In contrast, it showed no difference in zinc (Zn) uptake in both varieties. Uptake of Cu was not different between the two varieties, while uptake of Zn in the grain was higher in TULT than in Takanari. The present study suggests that CH4 emission deriving from BS application in paddy field can be mitigated by selecting an appropriate cultivar, like Takanari. However, care should be taken for heavy metal uptake in selecting cultivars.  相似文献   

12.
Zhang  H.  Lindberg  S. E.  Marsik  F. J.  Keeler  G. J. 《Water, air, and soil pollution》2001,126(1-2):151-169
Air/surface exchange of mercury was investigated over background soils at five sites in the Tahquamenon River watershed in the Michigan Upper Peninsula in the summer of 1998. Measurements of Hg fluxes were performed during middayperiods using the ORNL Teflon dynamic flux chamber. Mean Hg emission fluxes were 1.4±0.3–2.4±1.0 ng m-2 hr-1 for three shaded forest sites and 7.6±1.7 ng m-2 hr-1 for an open field site. Hg dry deposition was observed at a heavily shaded forest site overwet soils (mean = –0.3±0.2 ng m-2 hr-1). Theoverall mean Hg flux was 1.4±1.4 ng m-2 hr-1for the four shaded forest sites. The Hg fluxes observed at these sites are similar to those found at other northern background sites. Significant, rapid response of Hg emission to solar radiation was observed over these background soils. Artificial irrigation over these soils induced immediate andmeasurable increases in Hg emission. Soil temperature was found to be less influential to Hg air/surface exchange over these heavily shaded forest background soils than we have seen elsewhere.  相似文献   

13.

Purpose

The Todos os Santos Bay is the largest bay in Brazil and receives drainage from various watersheds. For more than 450 years, it was the main destination for the domestic and hospital sewage from the city of Salvador, Bahia. With the growing concern regarding the presence of pharmaceutical and personal care products (PPCPs) in the environment, an investigation was undertaken to determine the presence and levels of some commonly used drugs (i.e., atenolol, caffeine, carbamazepine, diazepam, diclofenac, erythromycin, ibuprofen) and personal care products (i.e., galaxolide, tonalide), using sediments as an indicator of their presence in the water column.

Material and methods

Surficial sediment samples from 17 stations located in the intertidal zone of the Todos os Santos Bay and infralittoral zone along the north coast of Salvador were tested for the presence of some PPCPs using LC-MS/MS (for drugs) and GC-MS/MS (for fragrances).

Results and discussion

The PPCPs examined were present in all sediment samples at levels of parts per billion of dry sediment. The highest concentrations were found for the fragrances galaxolide (52.5 ng g?1) and tonalide (27.9 ng g?1), followed by caffeine (23.4 ng g?1) and pharmaceuticals ibuprofen (14.3 ng g?1), atenolol (9.84 ng g?1), carbamazepine (4.81 ng g?1), erythromycin (2.29 ng g?1), diclofenac (1.06 ng g?1), and diazepam (0.71 ng g?1).

Conclusions

Pharmaceuticals were found to be ubiquitous in the sediments of the study areas. The texture of the sediment was an important factor in PPCPs fixation and deposition. The concentrations of all PPCPs had statistically significant positive correlations with the percentage of clay in the sediments.  相似文献   

14.

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   

15.
Nitrous oxide (N2O) emissions from the soil surface of five different forest types in Thailand were measured using the closed chamber method. Soil samples were also taken to study the N2O production pathways. The monthly average emissions (±SD, n?=?12) of N2O from dry evergreen forest (DEF), hill evergreen forest (HEF), moist evergreen forest (MEF), mixed deciduous forest (MDF) and acacia reforestation (ARF) were 13.0?±?8.2, 5.7?±?7.1, 1.2?±?12.1, 7.3?±?8.5 and 16.7?±?9.2?µg N m?2 h?1, respectively. Large seasonal variations in fluxes were observed. Emission was relatively higher during the wet season than during the dry season, indicating that soil moisture and denitrification were probably the main controlling factors. Net N2O uptake was also observed occasionally. Laboratory studies were conducted to further investigate the influence of moisture and the N2O production pathways. Production rates at 30% water holding capacity (WHC) were 3.9?±?0.2, 0.5?±?0.06 and 0.87?±?0.01?ng N2O-nitrogen (N) g-dw?1day?1 in DEF, HEF and MEF respectively. At 60% WHC, N2O production rates in DEF, HEF and MEF soils increased by factors of 68, 9 and 502, respectively. Denitrification was found to be the main N2O production pathway in these soils except in MEF.  相似文献   

16.
Antibiotics from various sources such as livestock waste are being accumulated in the soil. The excessive uptake of antimicrobial agents by plants has been a major concern as it is currently unknown how plants respond to the presence of antibiotics in agricultural lands. The objectives were to analyze the alteration of trigonelline (TRG) biosynthesized by plants in response to various antibiotic stresses and to evaluate the ability of peanut (Arachis hypogaea L.) plants to resist the deleterious impacts of antibiotic uptake. Three veterinary antibiotics used in this study were tetracycline, streptomycin sulfate, and chloramphenicol in the concentrations of 2.5 and 5 mg L?1. Mean TRG amounts were 53.4 ± 1.6 and 59.9 ± 1.1 μg·g?1 dry weight (DW) in Spanish as treated with growth chloramphenicol and streptomycin at 2.5 mg·L?1, respectively, and were significantly (p ≤ .05) different compared to the control (40.4 ± 1.6 μg·g?1 DW) of Spanish. Spanish genotype treated with chloramphenicol at 5 mg·L?1 had a mean TRG amount of 41.0 ± 1.0 μg·g?1 DW and improved yield, with the average pod number of 29.6 ± 7.6 and pod weight of 20.1 ± 6.1 g. TRG was continuously biosynthesized and increased under antibiotic stress up to 12.7% at full pod (R4 growth stage) and 139.1% at beginning maturity (R7), but declined 20.2% at the harvest stage (R8) in all combined genotypes when compared with TRG amounts (21.7 ± 0.6 μg·g?1 DW) at the flowering R1 stage.  相似文献   

17.
The goal of this project was to develop a method to measure the total gaseous mercury (TGM) concentrations in unsaturated soils. Existing methods did not allow for easy replication, were costly, and were more suited for other gases, such as CO2, that do not react with collection surfaces. To overcome these problems, we developed a method that simultaneously collects up to ten soil pore air samples. We used a single mass flow controller, one pump, and two banks of rotameters to draw soil air out of the ground at 25?smL?min?1 onto gold-coated quartz traps. Analysis of the gold traps was performed with a Tekran 2500 CVAFS mercury detector. The system was field tested at the Piney Reservoir Ambient Air Monitoring Station in western Maryland. Our system was relatively precise and accurate. For example, replicate TGM concentrations differed by less than 25% and recovery of known amounts of mercury were greater than 95%. Field measurements showed that the maximum soil pore air TGM concentrations, between 3 and 4?ng?m?3, occurred at the Oe?CA soil horizon interface. At all other depths, the total mercury concentrations were lower than the ambient air concentrations of 1.8?ng?m?3. We believe our new method can be used to precisely and accurately measure the TGM concentrations in unsaturated soils at multiple locations simultaneously.  相似文献   

18.

Purpose

The main objective of this study was to evaluate the potential of a counter-current leaching process (CCLP) on 14 cycles with leachate treatment at the pilot scale for Pb, Cu, Sb, and Zn removal from the soil of a Canadian small-arms shooting range.

Materials and methods

The metal concentrations in the contaminated soil were 904?±?112 mg Cu kg–1, 8,550?±?940 mg Pb kg–1, 370?±?26 mg Sb kg–1, and 169?±?14 mg Zn kg–1. The CCLP includes three acid leaching steps (0.125 M H2SO4?+?4 M NaCl, pulp density (PD)?=?10 %, t?=?1 h, T?=?20 °C, total volume?=?20 L). The leachate treatment was performed using metal precipitation with a 5-M NaOH solution. The treated effluent was reused for the next metal leaching steps.

Results and discussion

The average metal removal yields were 80.9?±?2.3 % of Cu, 94.5?±?0.7 % of Pb, 51.1?±?4.8 % of Sb, and 43.9?±?3.9 % of Zn. Compared to a conventional leaching process, the CCLP allows a significant economy of water (24,500 L water per ton of soil), sulfuric acid (133 L H2SO4 t–1), NaCl (6,310 kg NaCl t–1), and NaOH (225 kg NaOH t–1). This corresponds to 82 %, 65 %, 90 %, and 75 % of reduction, respectively. The Toxicity Characteristic Leaching Procedure test, which was applied on the remediated soil, demonstrated a large decrease of the lead availability (0.8 mg Pb L–1) in comparison to the untreated soil (142 mg Pb L–1). The estimated total cost of this soil remediation process is 267 US$ t–1.

Conclusions

The CCLP process allows high removal yields for Pb and Cu and a significant reduction in water and chemical consumption. Further work should examine the extraction of Sb from small-arms shooting range.  相似文献   

19.
The Hg concentrations in coal as fired in power plants in the Netherlands are low, 0.2 mg·kg?1 on average. After combustion the Hg is released partly (between 1 and 98%, on average 42%) in a gaseous phase, which is finally emitted into the air. The other part of the Hg, which remains in the ash is separated from the flue gases by electrostatic precipitators. The variation of the vaporisation percentage of Hg is probably caused by the presence of two chemical forms: Hgo and HgCl2. This may be concluded from the observation that relatively high concentrations of HCl in the flue gases (≈150 mg·m?3) give rise to low Hg concentration in the vapor phase. In cases when the concentrations of HCl are relatively low (≈25 mg·m?3) the amount of Hg in the vapor phase is high. The average gas phase concentrations of Hg in the flue gases, based on 33 measurements with no FGD, is 4.1 μg·mfo ?3. In a wet FGD based on the lime/limestone-gypsum process 50 to 70% of the Hg in the flue gases is removed, leaving a residual concentration of 1–2 μg·mfo ?3. The emission factor is then about 0.5 mg·GJ?1 or 5 μg·kWhr?1. In one particular measuring serie the fate of Hg was studied in a FGD-installation with a prescrubber.  相似文献   

20.
In this study, a new Co3O4 nanoparticles (NPs) coated with sodium dodecyl sulphate (SDS) is developed for preconcentration of trace amounts of cadmium ions (Cd 2+) as a prior step to its determination by flame atomic absorption spectrometry (FAAS). The effects of various parameters, including pH of sample solution, amount of sorbent, flow rates of solution and eluent, sample volume, type, and least amount of the eluent for elution of the Cd 2+ from Co3O4 NPs were studied and optimized. Experimental conditions for effective separation of trace levels of the Cd 2+were optimized with respect to different experimental parameters in Column method. Under the best experimental conditions, the calibration curve was linear in the range of 1.0–500.0 ng.mL?1 of cadmium (Cd) with R2 = 0.999. The detection limit was 0.4ng.mL?1 in the original solution (3Sb/m) and the relative standard deviation for eight replicate determination of 0.1µg.mL?1 Cd was ±2.1%. The method was validated by the analysis of a certified reference material with the results being in agreement with those quoted by manufactures. The developed method was successfully applied to the extraction and determination of Cd in water and food samples with satisfactory results.  相似文献   

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