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1.
Experiments were conducted during a 5 mo period (September 1975 to January 1976) to determine the Pb concentrations in Bangkok streets and blood Pb levels of Bangkok's population. A total of 185 air samples and 222 blood samples was collected and analyzed. Street Pb levels are in the range of 6.16 to 22.48 μg m?3 and blood Pb levels are in the range of 1 to 34 μg (100 g)?1 of whole blood, with an average value of 12.3 μg (100 g)P?1. The effects of various parameters on air and blood Pb levels are discussed in this paper. Air Pb levels are found to be closely related to traffic volume and proximity to the roads. Blood Pb levels are found to increase progressively with age, reaching a saturation value at about 40 yr of age. The average time spent daily on roads by the people and the distance of their residence/workplace from the main road are found to be major parameters, affecting the blood Pb levels. There is no evidence to show that blood and air Pb levels are directly related, at the present ambient exposure levels.  相似文献   

2.
Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese used as an additive in unleaded gasoline in Canada since 1977. Moreover, Canada is the only country in the world to have authorized the replacement of lead alkyls by MMT in gasoline. The purpose of the present study is to assess the importance of air contamination by Mn in relation to other air pollutants (gaseous and particulates), meteorological variables and traffic density. The concentration of both the gaseous (O3, CO, NO, NO2, SO2) and the particulate pollutants (Mn, Pb, NO? 3, SO?? 4, TSP) had been measured by the Montreal Urban Community in 1990 at seven sampling stations located in high traffic and low traffic density areas. Data on the meteorological conditions during that same period were also used. Non-parametric correlation, ANOVA and discriminant analyses were used to compare gaseous and particulate pollutants found between both levels of traffic density. In almost 50% of the daily air samples measured in 1990, the Mn concentrations are higher than the urban background level estimated at 0.04 μg m?3 and the variations of Mn concentrations are significantly correlated in time with traffic density. Moreover, Mn and TSP discriminate the best high and low traffic density areas. No significant differences have been observed between Pb, O3 and SO2 concentrations in both areas. These results should not be interpreted in terms of potential health effects since it is presently impossible to determine the fate of the Mn in the environment and its importance in terms of human exposure.  相似文献   

3.
Barley (Hordeum vulgare L.) was grown on a sandy soil given different doses of cadmium carbonate (salt), copper carbonate (malachite), lead carbonate (cerussite), and zinc carbonate (smithsonite) in a pot experiment conducted in a greenhouse. The element compounds were added to the soil in amounts equivalent to the following levels of the metals: Cd 5, 10, 50 μq ?1; Cu and Pb 50, 100, 500 μg g?1; Zn 150, 300, 1500 μg g?1. Sequential extraction was used for partition these metals into five operationally-defined fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. The residue was the most abundant fraction in the untreated soil for all the metals studied (43 to 61% of the total contents). The concentration of exchangeable Cd (0.2 μg g?1), Cu (0.01 μg g?1), Pb (0.1 μg g?1), and Zn (1.4 μg g?1) were relatively low in the untreated soil but increased markedly in the treated soils for Cd (up to 31 μg g?1) and Zn (up to 83 μg g?1), whereas only small changes were observed for Cu and Pb. The pot experiment showed a significant increase in the Cd and Zn contents of barley grown on the treated soils, but only small changes in Cu and Pb concentrations.  相似文献   

4.
In a screen-house study, the effects of artificially contaminating the soil with lead (Pb) at levels ranging from 0 to 1500 mg kg?1 soil on the growth and uptake of Pb and micronutrients by Indian mustard [Brassica juncea (L.) Czern.] grown on a loamy sand soil (Typic Ustorthent) were investigated. The crop was grown for 60 days with adequate basal fertilization of nitrogen, phosphorus, and potassium, and dry matter was recorded. The plants were analyzed for total Pb and micronutrients, and the soil was analyzed for diethylenetriaminepentaacetic acid (DTPA)-extractable Pb. The DTPA-extractable Pb measured before sowing of Indian mustard increased consistently and significantly with increase in rates of Pb application to soil. It increased from 0.65 mg kg?1 in the control to 199.8 mg kg?1 in soil treated with 1500 mg Pb kg?1 soil. Significant reduction in the dry-matter yield of Indian mustard occurred with Pb applications of 500 mg kg?1 soil and greater. The concentration as well as uptake of Pb by Indian mustard increased significantly over control at all rates of its application. It increased from 9.4 μg pot?1 in the control to 220.6 μg pot?1 at Pb application of 1500 mg kg?1 soil. Applications of Pb to the soil decreased the concentration of micronutrients in plants, but a significant reduction occurred only for iron at rates greater than 500 mg Pb kg?1 soil. However, the uptake of iron, manganese, and copper registered a significant decline at Pb application of 500 mg kg?1 and greater and that of zinc at 750 mg kg?1 and greater. In a Typic Ustorthent soil, a DTPA-extractable Pb level of 59.5 mg kg?1 and plant content of 44.2 μg Pb g?1 dry matter was found to be the upper threshold levels of Pb for Indian mustard. This study suggests that once the soil is contaminated by Pb, it remains available in the soil for a long time, and such soils, if ingested with food crops, may be a significant source of Pb toxicity to both humans and grazing animals.  相似文献   

5.
Long term continuous monitoring measurements of urban atmospheric concentrations of O3, NO2, NO, and SO2 were performed for the first time in Ciudad Real, a city in central-southern Spain. The measurements were carried out using the differential optical absorption spectroscopy (DOAS) technique, with a commercial system (OPSIS, Lund-Sweden), covering the summer and winter seasons (from 21st July 2000 to 23rd March 2001). Mean levels of O3, NO2 and SO2 monitored during this period were: 27 μg m?3, 50 μg m?3 and 7 μg m?3 respectively. The highest hourly averaged value of O3 (160 μg m?3) was measured during the summer period, while NO2 was enhanced in wintertime (highest values 90 μg m?3). In the coldest period, when central heating installations were operating, SO2 showed maximum levels of 20 μg m?3. The daily, weekly and seasonal analysis of the data shows that photochemical air pollution dominates in this urban atmosphere and is strongly influenced by levels of motor traffic and domestic heating system emissions. These measurements were compared with other studies in Spain and Europe. Also, the long path averaged DOAS measurements were compared with in situ observations made in Ciudad Real, from 23rd August 2000 to 25th September 2000, using a mobile air pollution control station. All gas concentrations reported in this paper are below the WHO guidelines and the different thresholds introduced by the European Environmental Legislation.  相似文献   

6.
The amount of Cd and Pb in full blood and in the urine of males in Cracow and in a control area were measured and compared to the background of the level of these metals in air, dust fall and drinking water. The investigations were carried out in the years 1984–85. The mean Cd level in body fluids of Cracow's inhabitants was significantly higher than in the control group, and it amounted to: 0.54 μg Cd 100 mL?1 in blood and 2.13 μg Cd L?1 in urine. The Pb content in blood of the Cracow group (15.74 μg 100 mL?1) was also significantly higher than in the control one, while the Pb level in urine was similar in both populations, reaching values below 10 μg L?1. The mean annual Cd concentration in air and the Cd content in the dust fall in Cracow were 3 times higher than in the control area. The mean annual Pb concentration in Cracow's air exceeded the permissible Polish norm. In comparison with the control area, the Pb concentration level in air and its content in the dust fall in Cracow were 5 and 2 times higher, respectively. The level of Cd and Pb concentration in drinking water in Cracow and in the control area were much lower than the permissible values; however, in Cracow they were somewhat higher than in the control area.  相似文献   

7.
Forest floor and mineral soil samples were collected from subalpine spruce-fir forests at 1000 m above mean sea level on 19 mountains in the northeastern United States to assess patterns in trace metal concentrations, acidity, and organic matter content. The regional average concentrations of Pb, Cu, and Zn in the forest floor were 72.3 (2.9 s.e.) μg g?1, 8.5 (0.7) μg g?1, and 46.9 (2.0) μg g?1, respectively. The regional average concentrations of Pb, Cu, and Zn in the mineral soil were 13.4 (0.8) μg g?1, and 18.2 (1.2) μg g?1, respectively. The regional average pH values of the forest floor and mineral soil were 3.99 (0.03), and 4.35 (0.03), respectively. The Green Mountains had the highest concentrations of Pb (105.7 μg g?1), and Cu (22.7 μg g?1), in the forest floor. They also had the highest concentrations of Cu (18.0 μg g?1), in the mineral soil. Site aspect did not significantly influence any of the values. Concentrations of Pb were lower than concentrations reported earlier in this decade at similar sites while concentrations of Cu and Zn remained the same. We believe that these lower Pb concentrations reflect real changes in forest Pb levels that have occurred in recent years.  相似文献   

8.
The effect of added Pb on the respiration and dehydrogenase activity of two sandy soils, a clay soil and a peat soil, (all with different physico-chemical properties), was studied.A concentration of 375 μg Pb· g? inhibited the respiration of the sandy soil by ca. 15%, 1500 μg Pb· g?ca. 50%. In the clay soil 1500 μg Pb· g? caused a 15% reduction in respiration. The inhibition of respiration in the sandy soil was still ca. 30% 40 months after the addition of Pb. Respiration of the peat soil was not affected by even 7500 μg Pb· g?.Dehydrogenase activity was affected by Pb in a similar way to soil respiration. In the sandy soil a considerable reduction occurred, while in the clay and peat soils dehydrogenase activity was not reduced.It was concluded, that a relationship exists between the inhibitory effects of Pb and the buffering capacity of the soil as expressed by its cation-exchange capacity. Because of these different effects of the same Pb concentration on the various soil types, no single value for the permitted concentration of lead pollution in soil could be established.  相似文献   

9.
Ammonification of soil organic N and nitrification of ammonium-N was studied in Tindall clay loam over a range of temperatures from 20–60 C. Nitrification rates at each temperature were constant throughout the 28 day incubation, whereas most of the ammonification occurred in the first 7 days. The optimum for nitrification was close to 35 C. exhibiting a sharp peak at this temperature at which the potential rate was 4.8 μg N/g day?1, compared with 0.5 μg N/g day?1 at 20°C and 0.25 μg N/g day?1 at 60°C. The optimum temperature for ammonification was approximately 50°C at which the rate was 2.8 μg N/g day?1 in the first 7 days but only 0.5 μg N/g day?1 between 14 and 28 days.The temperature responses could be described mathematically with functions of the type logoN = k × 1/T.The results are discussed in relation to daily patterns of N mineralization in the field where temperatures show diurnal fluctuation.  相似文献   

10.
The Pb content in orchard soils at Mission Peninsula, Michigan was determined to assess the impact of historical lead arsenate applications. Soil samples at 72 sites located in five orchards were collected at depths of 2-, 20-, 50-, and 100 cm. Atomic absorption spectroscopy was used to quantify Pb levels (μg g-1). Mean surface Pb levels at individual orchards ranged from< 1–136 μg g-1 and rapidly decreased with depth, to <1–5 μg g-1 at 100 cm. The impact of textural class and slope angle on Pb levels was also analyzed. Correlation coefficients linking Pb levels with textural class were weak, ranging from 0.21 to –0.07. Varying slope steepness and slope position within orchards failed to affect the spatial pattern of soil Pb. Soil Pb levels were also compared at 5 sites along local roads with varying levels of automobile traffic. Samples were collected 1 m from the roadside at the same depth intervals studied in orchards. Average daily traffic along the busiest roadsites ranged from 8200 to 16 000; these sites had Pb levels of 90–210 μg g-1. Such locales had Pb levels similar to the more intensively sprayed orchards.  相似文献   

11.
The effects of four concentrations (0.5, 1, 5 and 10 μg mL?1) of the heavy metals Hg, As, Pb, Cu, Cd, and Cr on some senescence variables of Cuscuta reflexa Roxb. were studied. All of the treatments, except 0.5 μg mL?1, decreased Hill reaction activity, chlorophyll and protein contents and dry matter percentage in biomass and increased tissue permeability over control data. The harmful effects of the metals were best visible at 10 μg mL?1. The general order of sensitivity was As > Cd > Pb > Hg > Cu > Cr (absolute metal concentration). The data suggest that Cuscuta reflexa shows tolerance to the heavy metals tested up to 0.5 μg mL?1.  相似文献   

12.
Ten selected metals (Na, K, Fe, Zn, Pb, Mn, Cr, Co, Ni & Cd) were estimated in total suspended particulate (TSP) samples collected on glass fibre filters in urban Islamabad, Pakistan, from October 2002 to May 2003, using a high volume sampling technique. The wet digestion method (HNO3/HClO4) was used for metal analysis by the flame atomic absorption spectrophotometry (FAAS) method. Maximum mean contribution was noted for Na (1.949 μg m?3), followed by K (0.900 μg m?3), Zn (0.603 μg m?3), Fe (0.584 μg m?3) and Pb (0.214 μg m?3). The particle size determination on % volume basis for four fractions (PM< 2.5, PM2.5–10, PM10–100& PM> 100) was also carried out. PM10–100 were found to be the most abundant in the local atmosphere followed by PM2.5–10, while the respirable fraction (PM< 2.5) and giant fraction (PM> 100) showed comparable and lower levels. The trace metals were found to be mainly associated with PM< 2.5 and PM2.5–10. The influence of climatic variables on toxic trace metals and particle size fractions was also investigated statistically and it was revealed that temperature has a significant correlation with fine particle fractions and airborne trace metal levels. The source identification was carried out by Principal Component Analysis and Cluster Analysis. Four metal sources were identified: industrial (32.6%), soil-derived dust (21.9%), traffic/road dust (19.8%), and metallurgical/garbage incineration (12.4%). The metal levels were also compared with those reported for other parts around the world.  相似文献   

13.
Samples from the surface layer (0–15 cm) of a cultivated Typic Haplaquoll, collected in the fall of 1975 from field plots amended with variable amounts of Pb in the spring of 1969 and with ground corn cobs in 1973 and 1974 (22.4 tons ha?1), were analyzed for organic N, total Pb, exchangeable- and soluble-Pb, specifically-adsorbed Pb, and organically-bound Pb. Highly-significant correlations were obtained between organic N and soil Pb concentrations, from which it was concluded that the applied Pb resulted in small increases in the organic matter content of the soil. The most probable mechanism was believed to be through the formation of biologically-resistant Pb-organic matter complexes. At low amounts of soil Pb (20–30 μg g?1 range), approximately 30% of the soil Pb occurred in organic linkages but the proportion increased steadily up to 400 μg g?1 and gradually leveled off thereafter. The conclusion was reached that progressive contamination of the test soil by exogenous Pb additions, such as from automobile exhaust near traffic highways, would have little effect on plant available forms until soil Pb concentrations reached about 100 μg g?1, following which the concentration in the soil solution would be related to and controlled by the size of the organic pool.  相似文献   

14.
During 1987, seawater, rain, dust and drainage water samples were collected from Abu-kir bay (360 km2) east of Alexandria city to set up and evaluate the relative importance of different sources to the biogeochemical cycle of Pb in the bay. The mean total concentration of Pb in the bay water was 455 ± 180 and 785 ± 287 ng kg?1 during low and high flow periods, respectively. About 75 ±12% are in the particulate form. The bay receives annually about 8.12 ± 2.18 and 6.13 ± 1.06 ± of Pb through agricultural and industrial discharge. In addition, 0.48 ± 0.11 ± yr?1 and 0.23 ± 0.04 t yr?1 of Pb reaches the bay through wet and dry depositions, respectively. The outflowing surface water from the bay carries 15.4 ± 3.6 t Pb yr?1 to the southeastern Mediterranean waters. Data from sedimentation traps indicated that the bulk sedimentation rate in the bay was 95 ± 18 kg yr?1 elevating the concentrations of Pb in sediments to more than 64 μg g?1. The imbalance in the Pb flux (excess + 0.6 ± 0.08 t) indicates Pb accumulation in the water column. The apparent residence time of Pb in the bay is 62 ± 15 d. The assimilative capacity of Pb in the bay expressed in terms of Pb loading / in bay concentration amounted to 25 ± yr?1/ μg L?1. A 10% reduction in the present day load to the bay will yield a Pb concentration of less than 0.1 μg kg?1 after 11 to 12 yr.  相似文献   

15.
Dentrification rates in two soils were assessed separately as a function of NO3? concentration while providing a constant initial glucose concentration, and as a function of glucose concentration while providing a constant initial NO3?-N concentration. Of the soils used, a Hanford sandy loam and a Coachella fine sand, the bacteria in the former produced higher rates of denitrification with a maximum loss of 1500 μg NO3?-N/ml day?1 as compared to a loss of 150 μg NO3?-N/ml day?1 from the latter. Rates of loss closely approximated Michaelis Menten kinetics in the Coachella sand, and Km values for glucose-C and NO3?-N were 500 μg/ml and 170 μg/ml, respectively. Rates of loss of NO3?-N from the Hanford soil did not approximate Michaelis-Menten kinetics, and this was attributed to failure to saturate enzyme systems in the denitrifying bacteria with glucose and nitrogen when each was held constant. C/N ratios around 2 appeared to provide the greatest rates of denitrification. High C/N ratios or high glucose concentrations (1.8 per cent) retarded denitrification, with fungal growth and a subsequent drop in pH occuring. A Pseudomonas was incubated aerobically for 24 h followed by a 72 h anaerobic incubation with nitrate as the sole nitrogen source at 0, 10, 50, 100, 250 and 500mg N/ml concentrations. Assimilatory nitrate reduction never exceeded 75 mg N/ml, and it was concluded that this mode of nitrate reduction is insignificant at higher nitrate concentrations by comparison to dissimilatory nitrate reduction, i.e. denitrification.  相似文献   

16.
The early life stages of smallmouth bass (Micropterus dolomieui) were exposed to Pb in acute (96 hr) and sub-chronic (90 day) bioassays (water hardness = 152 mg L?1 as CaCO3). After 96-hr static exposures at nominal Pb concentrations up to 15.9 mg L?1, eggs and sac fry showed no increased mortality over that in controls. Swim-up fry (96-hr LC50 = 2.8 mg Pb L?1) were more sensitive to Pb exposure than were fingerlings (96-hr LC50 of 29.0 mg Pb L?1 ). The relation between dissolved Pb and mortality was non-significant for either swim-up fry or fingerlings. Fingerlings were exposed to Pb concentrations as high as 405 μg L?1 for 90 day to evaluate effects on substrate selection, locomotor activity, hematology, and weight. Dark or light substrate selection (cover-seeking) and locomotor activity, weight and hemoglobin concentration in the blood were not significantly altered by any treatment. Hematocrit and leucocrit varied significantly but not in relation to Pb levels. Sub-chronic Pb exposure did not appear to represent a threat to smallmouth bass in waters of medium hardness and above-neutral pH (7.1 to 7.9).  相似文献   

17.
A total of 2454 samples were collected to evaluate the degree, extent, and distribution of Pb contaminated soil in Minnesota. Samples were collected primarily at locations where susceptible populations were concentrated. Soil Pb concentrations in chilldren's play areas, urban gardens, and at open sites were generally below 100 μg g ?1 when Pb painted structures were absent. Street side and yard soils typically had Pb concentrations between 10 to 300 μg g?1, with samples collected near major highways or Pb painted structures exhibiting greater values. The most severely contaminated soils were found in localized areas around the foundations of private residences, where concentrations up to 20 136 μg g?1 were detected. Exterior Pb based house paint is the major Pb source in these soils, and its presence greatly influences the distribution of contaminated soil in individual yards. Contamination attributable to autoemissions is less concentrated but more widespread than contamination from paint. A higher proportion of soils exceeding 1000 wg g?1 Pb was found in large cities than elsewhere. However, a sufficient number were detected in small cities and rural areas to confirm that high soil Pb levels are not exclusively an urban phenomenon. By examining the degree, extent, and distribution of Pb contaminated soils in Minnesota, this study provides information useful in guiding response actions to reduce children's exposure to Pb by this pathway.  相似文献   

18.
The atmospheric Pb and Br levels were measured in Downtown Baghdad. The average concentrations of Pb and Br obtained were 2.593 and 1.004 μg m?3, respectively. The mean value of Br/Pb ratio was 0.41 which is close to the ethyl ratio while the correlation coefficient between Br and Pb was 0.91. It is concluded that the major contribution of particulate Pb in the ambient air of Downtown Baghdad is due to emissions from motor vehicles. The seasonal variation of Br/Pb ratio is also presented ranging from 0.36 to 0.48 from summer to winter.  相似文献   

19.
A cloud point extraction (CPE) procedure has been developed for the determination of available cadmium (Cd) and lead (Pb) in soil by flame atomic absorption spectrometry. The proposed method was based on the CPE of a complex from ammonium pyrrolidine dithiocarbamate (APDC) and metal Cd and Pb using emulsifier octyl polyethylene glycol phenol ether (OP) as surfactant. Conditions that would affect the complex formation and separation were researched in detail, including extraction conditions as well as pH, amount of the chelating agent, concentration of the surfactant, equilibration temperature and time, and salt effect. Under the optimized conditions, both of the calibration graphs were linear in range of 0–1.0 μg mL?1 with detection limits of 0.29 ng mL?1 for Cd and 2.10 ng mL?1 for Pb. The relative standard deviation (RSD) for 11 replicate measurements at 0.10 μg mL?1 of Cd and Pb were 2.18% and 4.04%, respectively. The enhancement factors were 48.8 and 61.6 for Cd and Pb, respectively. The recoveries of Cd and Pb at the spiking level of 0.10 μg g?1 in soil samples were from 91.7% to 115% and from 91.0% to 115%, respectively. The proposed method has been applied to the determination of available Cd and Pb in soil.  相似文献   

20.
Gas exchange rates over soils were measured in a closed, flowing-gas system. 14CO was rapidly oxidized to 14CO2 with only a minor loss in atmospheric radioactivity. Incorporation of 14C into the soil was slight and was via 14CO2 rather than 14CO. CO oxidation was a microbial process and no oxidation occurred when soils had been autoclaved. The rate of CO depletion was concentration dependent and followed Michaelis-Menten kinetics. The rate constants Km and Vmax ranged from 18 to 51 μ 1?1 CO and from 0.58 to 4.35 mg C kg?1 dry soil h?1 respectively. The maximum rate of reaction for Hubbard Brook soil was about an order of magnitude greater than any soil previously reported. The oxidation reaction was accompanied initially by a reduction in net soil respiration. This was then followed by a period of high respiration which continued until CO levels were reduced to about 5μll?1. Thereafter respiration fell below the pretreatment rate and only returned to that rate 45 min after CO had been depleted from the atmosphere. The data suggest that at high CO concentrations (40–100 μll?1CO) autotrophic carboxydobacteria comprise the main component of the CO-oxidizing population and, as the concentration declines towards ambient levels they are replaced by heterotrophic microorganisms possessing a cometabolic process.  相似文献   

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