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1.
The 19th Common Wealth Games was organized at Delhi, India, during October 3 to 14, 2010, where more than 8,000 athletes from 71 Commonwealth Nations have participated. In order to give them better environment information for proper preparedness, mass concentrations of particulate matters below 10 microns (PM10) and 2.5 microns (PM2.5), black carbon (BC) particles and gaseous pollutants such as carbon monoxide (CO) and nitrogen oxide (NO) were monitored and displayed online for ten different locations around Delhi, including inside and outside the stadiums. This extensive information system for air quality has been set up for the period from September 24 to October 21, 2010, and data have been archived at 5-min interval for further research. During the study period, average concentration of PM10 and PM2.5 was observed to be 229.7 ± 85.5 and 112.1 ± 56.0 μg m?3, respectively, which is far in excess of the corresponding annual averages, stipulated by the national ambient air quality standards. Significant large and positive correlation (r = 0.93) between PM10 and PM2.5 implies that variations in PM10 mass are governed by the variations in PM2.5 mass. The mass concentrations of PM2.5 inside the stadium were found to be ~18 % lower than those outside; however, no large variations were observed in PM10. Mean concentrations of BC, CO and NO for the observation period were 10.9 μg m?3 (Min, 02 μg m?3; Max, 31 μg m?3), 1.83 ± 0.89 ppm (Min, 0.48 ppm; Max, 4.55 ppm) and 37.82 ppb (Min, 2.4 ppb; Max, 206.05 ppb), respectively. BC showed positive correlation (r = 0.73) with CO suggests unified source for both of them, mainly from combustion emissions. All the measured parameters, however, show a significant diurnal variation with enhanced peaks in the morning and late night hours and lower values during daytime.  相似文献   

2.
Size distribution of PM10 mass aerosols and its ionic characteristics were studied for 2 years from January 2006 to December 2007 at central Delhi by employing an 8-stage Andersen Cascade Impactor sampler. The mass of fine (PM2.5) and coarse (PM10?2.5) mode particles were integrated from particle mass determined in different stages. Average concentrations of mass PM10 and PM2.5 were observed to be 306 ± 182 and 136 ± 84 μg m?3, respectively, which are far in excess of annual averages stipulated by the Indian National Ambient Air Quality Standards (PM10: 60 μg m?3 and PM2.5: 40 μg m?3). The highest concentrations of PM10?2.5 (coarse) and PM2.5 (fine) were observed 505 ± 44 and 368 ± 61 μg m?3, respectively, during summer (June 2006) period, whereas the lower concentrations of PM10?2.5 (35 ± 9 μg m?3) and PM2.5 (29 ± 13 μg m?3) were observed during monsoon (September 2007). In summer, because of frequent dust storms, coarse particles are more dominant than fine particles during study period. However, during winter, the PM2.5 contribution became more pronounced as compared to summer probably due to enhanced emissions from anthropogenic activities, burning of biofuels/biomass and other human activities. A high ratio (0.58) of PM2.5/PM10 was observed during winter and low (0.24) during monsoon. A strong correlation between PM10 and PM2.5 (r 2 = 0.93) was observed, indicating that variation in PM10 mass is governed by the variation in PM2.5. Major cations (NH4 +, Na+, K+, Ca2+ and Mg2+) and anions (F?, Cl?, SO4 2? and NO3 ?) were analyzed along with pH. Average concentrations of SO4 2? and NO3 ? were observed to be 12.93 ± 0.98 and 10.33 ± 1.10 μg m?3, respectively. Significant correlation between SO4 2? and NO3 ? in PM1.0 was observed indicating the major sources of secondary aerosol which may be from thermal power plants located in the southeast and incomplete combustion by vehicular exhaust. A good correlation among secondary species (NH+, NO3 ? and SO4 2?) suggests that most of NH4 + is in the form of ammonium sulfate and ammonium nitrate in the atmosphere. During winter, the concentration of Ca2+ was also higher; it may be due to entrainment of roadside dust particles, traffic activities and low temperature. The molar ratio (1.39) between Cl? and Na+ was observed to be close to that of seawater (1.16). The presence of higher Cl? during winter is due to western disturbances and probably local emission of Cl? due to fabric bleaching activity in a number of export garment factories in the proximity of the sampling site.  相似文献   

3.
The objective of the study is to investigate spatio-temporal variations of PM10, PM2.5, and PM1 concentrations at seven residential sites, located in the vicinity of opencast coal projects, Basundhara Garjanbahal Area (BGA), India. Meteorological parameters such as wind speed, wind direction, relative humidity, and temperature were collected simultaneously with PM concentrations. Mean concentrations of PM10 in the range 215 ± 169–526 ± 412 μg m?3, PM2.5 in the range of 91 ± 79–297 ± 107 μg m?3, PM1 in the range of 68 ± 60–247 ± 84 μg m?3 were obtained. Coarse fractions (PM2.5–10) varied from 27 to 58% whereas fine fractions (PM1–2.5 and PM1) varied in the range of 51–73%. PM2.5 concentration was 41–74% of PM10 concentration, PM1 concentration was 31–62% of PM10 concentration, and PM1 concentration was 73–83% of PM2.5 concentration. Role of meteorology on PM concentrations was assessed using correlation analysis. Linear relationships were established among PM concentrations using least square regression analysis. With the aid of principal component analysis, two components were drawn out of eight variables, which represent more than 75% of variance. The results indicated that major sources of air pollutants (PM10, PM2.5, PM1, CO, CO2) at the residential sites are road dust raised by vehicular movement, spillage of coal generated during transportation, spontaneous combustion of coal, and biomass burning in village area.  相似文献   

4.
The increasing emission of primary and gaseous precursors of secondarily formed atmospheric particulate matter due to continuing industrial development and urbanization are leading to an increased public awareness of environmental issues and human health risks in China. As part of a pilot study, 12-h integrated fine fraction particulate matter (PM2.5) filter samples were collected to chemically characterize and investigate the sources of ambient particulate matter in Guiyang City, Guizhou Province, southwestern China. Results showed that the 12-h integrated PM2.5 concentrations exhibited a daytime average of 51 ± 22 µg m?3 (mean ± standard deviation) with a range of 17–128 µg m?3 and a nighttime average of 55 ± 32 µg m?3 with a range of 4–186 µg m?3. The 24-h integrated PM2.5 concentrations varied from 15 to 157 µg m?3, with a mean value of 53 ± 25 µg m?3, which exceeded the 24-h PM2.5 standard of 35 µg m?3 set by USEPA, but was below the standard of 75 µg m?3, set by China Ministry of Environmental Protection. Energy-dispersive X-ray fluorescence spectrometry (XRF) was applied to determine PM2.5 chemical element concentrations. The order of concentrations of heavy metals in PM2.5 were iron (Fe) > zinc (Zn) > manganese (Mn) > lead (Pb) > arsenic (As) > chromium (Cr). The total concentration of 18 chemical elements was 13 ± 2 µg m?3, accounting for 25% in PM2.5, which is comparable to other major cities in China, but much higher than cities outside of China.  相似文献   

5.
Atmospheric dust is considered to be the major cause of poor air quality due to its contribution to high particulate levels, but their interaction with the acidic gases helps in controlling the level of SO2 and NO2 through ambient neutralization reactions. In the present study, the interaction of acidic gases such as SO2 and NO2 with alkaline dust was investigated during October, 2013–July, 2014 at a site named as Babarpur located at the Trans-Yamuna region of Delhi. The concentration of SO2 ranged from 10 to 170 μg/m3 with an average of 36 μg/m3 while that of NO2 ranged from 15 to 54 μg/m3 with an average of 26?±?8 μg/m3. The results were observed to be well within the National Ambient Air Quality Standard (NAAQS) limits prescribed by the Central Pollution Control Board (CPCB). The average concentrations of SO2 during day and night time were recorded as 31?±?18 and 43?±?53 μg/m3 respectively while the mean concentrations of NO2 during day and night time were recorded as 26?±?7 and 27?±?12 μg/m3 respectively. A positive correlation between SO42? and NO3? was also observed indicating their secondary aerosol formation. In aerosol phase, average concentrations of SO42? during day and night time were 3.9?±?0.3 and 6.5?±?2.3 μg/m3 respectively while that of NO3? were 9.5?±?1.5 and 7.3?±?0.5 μg/m3 respectively. Molar ratios of Ca2+/SO42?, NH4+/SO42?, and NH4+/NO3? were observed as 8, 5, and 1.7 during daytime and 1.5, 0.4, and 0.8 during nighttime respectively. Such molar ratios confirmed high concentrations of sulphate (SO4)2? and low concentrations of nitrate (NO3?) during night time, thereby indicating different pathway of aerosol formation during day and night time. Surface morphology and elemental composition of aerosol samples showed various oval, globular, and platy shapes where the diameter varied from few nm to ~5 μm depending on their precursors. There were certain shapes like grossularite, irregular aggregate, grape-like, triangular, and flattened which indicate the crustal origin of aerosols and their possible role in SO2 and NO2 adsorption.  相似文献   

6.
Ambient air and coarse, fine and particulate-bound mercury (Hg(p)) pollutants were collected and analyzed from March 17 to May 22 and September 3, 2009 to March 5, 2010 at a highway traffic site located in Sha-Lu, central Taiwan. This study has the following objectives: (1) to measure the coarse and fine particulates concentrations and the particulate-bound mercury Hg(p) which was attached to these particulate; (2) to determine the average Hg(p) compositions in coarse and fine particulates and (3) to compare the Hg(p) concentrations and compositions particulate in this study to the those obtained in other studies. The results obtained in this study indicated that the average ambient air PM2.5, PM2.5–10 and PM10 were 18.79 ± 6.71, 11.22 ± 4.93 and 30.01 ± 10.27 μg/m3, respectively. The ranges of concentrations for Hg(p) in PM2.5 were from 0.0016 to 0.0557 ng/m3, from 0.0006 to 0.0364 ng/m3 in PM2.5–10 and from 0.0022 to 0.0862 ng/m3 in PM10. In addition, the highest particle-bound mercury compositions in PM2.5 were 16.85 ng/g and the lowest particle-bound mercury concentrations were 0.55 ng/g. The highest particle-bound mercury compositions in PM2.5–10 were 13.88 ng/g and the lowest particle-bound mercury in PM2.5–10 were 0.22 ng/g.  相似文献   

7.
The present work is an attempt to investigate pollution effect on an ornamental tree species Thevetia peruviana (Pers.) K. Schum. The study was conducted in various green spaces of institutional, industrial, residential and near traffic site representing as different status of air pollution concentration depending on land-use type. The resistance index calculated for selected species had mean value of 14.57 ± 0.41 observed at study sites. The dust deposition was found in range of 5.14–7.74 mg cm?2 on foliar surface of 12 cm2. The examination of leaf structure with scanning electron microscope showed presence of airborne dust particles in coarse and fine sizes with higher deposition found in industrial and residential sites. The epicuticular wax layer on upper surface of foliar was found eroded at industrial and traffic regions. The equivalent diameter of particles was observed to range from 0.45 to 12.71 µm in Poisson distributional pattern. The density of number concentration of dust particles was observed 1411 and 3703 in institutional and industrial area deposited on 0.22 mm2 of foliar surface. The elemental distribution on leaves of Thevetia peruviana has revealed a mixture of carbonaceous and soil matrix elements such as C, O, Al, Na, Si, K and Mg observed in proportion of X-rays counts per second. The whole experiment gave a positive indication for plant species as a tolerant bio-indicator of air pollutants in Delhi. The diverse flora present in city provides an opportunity for reducing harmful concentration of PM10 and PM2.5 and improving quality of air for human health.  相似文献   

8.
The Indo-Gangetic Plain (IGP) is a major regional and global emitter of atmospheric pollutants, which adversely affect surrounding areas such as the Himalayas. We present a comprehensive dataset on carbonaceous aerosol (CA) composition, radiocarbon (Δ14C) -based source apportionment, and light absorption of total suspended particle (TSP) samples collected over a 3-year period from high-altitude Jomsom in the central Himalayas. The 3-year mean TSP, organic carbon (OC), and elemental carbon (EC) concentrations were 92.0 ± 28.6, 9.74 ± 6.31, and 2.02 ± 1.35 μg m?3, respectively, with the highest concentrations observed during the pre-monsoon season, followed by the post-monsoon, winter, and monsoon seasons. The Δ14C analysis revealed that the contribution of fossil fuel combustion (ffossil) to EC was 47.9% ± 11.5%, which is consistent with observations in urban and remote regions in South Asia and attests that EC likely arrives in Jomsom from upwind IGP sources via long-range transport. In addition, the lowest ffossil (38.7% ± 13.3%) was observed in winter, indicating large contributions in this season from local biomass burning. The mass absorption cross-section of EC (MACEC: 8.27 ± 1.76 m2/g) and water-soluble organic carbon (MACWSOC: 0.98 ± 0.45 m2/g) were slightly higher and lower than those reported in urban regions, respectively, indicating that CA undergo an aging process. Organic aerosol coating during transport and variation of biomass burning probably led to the seasonal variation in MAC of two components. Overall, WSOC contributed considerably to the light absorption (11.1% ± 4.23%) of EC. The findings suggest that to protect glaciers of the Himalayas from pollution-related melting, it is essential to mitigate emissions from the IGP.  相似文献   

9.
Soil salinity and sodicity are escalating problems worldwide, especially in arid and semiarid regions. A laboratory experiment was conducted using soil column to investigate leaching of soluble cations during reclamation process of a calcareous saline–sodic soil (CaCO3?=?20.7%, electrical conductivity (EC)?=?19.8 dS m?1, sodium absorption ratio (SAR)?=?32.2[meq L?1]0.5). The amendments consisted of control, cattle manure (50 g kg?1), pistachio residue (50 g kg?1), gypsum (5.2 g kg?1; equivalent of gypsum requirement), manure + gypsum and pistachio residue + gypsum, in three replicates which were mixed thoroughly with the soil, while sulfuric acid as an amendment was added to irrigation water. To reflect natural conditions, after incubation period, an intermittent irrigation method was employed every 30 days. The results showed that EC, SAR, and soluble cations of leachate for the first irrigation step were significantly higher than those of the subsequent leaching runs. Moreover, the concentration of removed soluble cations was lower for the control and gypsum-treated soils. It was found that among applied amendments, treatments containing cattle manure showed higher concentrations of sodium, calcium, and magnesium in the leachate, while due to pistachio residue application, further amount of potassium was removed out of soil column. The addition of pistachio residue resulted in the highest reduction in soil salinity and sodicity since the final EC and exchangeable sodium percentage dropped to 18.0% and 11.6% of their respective initial values, respectively. In the calcareous soil, solubility of gypsum found to be limited, in contrast, when it was added in conjunction with organic amendments, greater amounts of sodium were leached.  相似文献   

10.
Changes in water chemistry along the High Arctic fluvial–lacustrine system located in Wedel Jarlsberg Land in the SW Spitsbergen (Svalbard) were investigated during the summer season of 2010 and 2011. The newly formed river–lake system consists of three lakes connected with the Brattegg River. The first bathymetric measurements of these lakes were made by the authors in 2010. The Brattegg River catchment represents a partly glaciered Arctic water system. The studied lakes are characterized by low mineralization and temperature of water. The value of the electrolytic conductivity (EC) ranges from 30.2 to 50.5 μS cm?1 and the temperature of surface water from 1.5 to 7.8 °C. The temperature increase takes place downstream starting from Upper Lake to the outflow from Myrktjørna Lake. The waters of lakes have higher temperatures than the stream. The predominant ions are HCO3 ? (up to 16.5 mg L?1), Cl? (6.66–8.53 mg L?1), Ca2+ (2.40–4.45 mg L?1) and Na+ (2.65–3.36 mg L?1). The highest values of ammonium and DOC found in the lowest Myrktjørna Lake seem to be related to the presence of aquatic organisms and also birds. From the group of 10 analyzed microelements, increased concentrations of aluminum, up to almost 500 μg L?1, are present in the lakes’ water. Water isotopic composition ranges for δ18O and δ2H, from ?10.6 to ?10.9‰ and from ?70.8 to ?72.3‰, respectively. The vertical zonality of lake waters is manifested in a decrease in the temperature and increase in EC and chemical elements concentrations.  相似文献   

11.
The adsorption properties of eggshell membranes (ESM), eggshells (ES) and orange peels (OP) were studied for the removal of arsenic (total As) and selenium (total Se). The effect of chemical treatment of these adsorbents by HNO3 and NaOH was also investigated using Fourier transform infrared spectroscopy (FT-IR). Analysis of the FT-IR spectra showed that treatment with NaOH and HNO3 had an effect on the functional groups present in the materials and also on the adsorption by extension. Thermal analysis showed that ES were more thermally stable than the others with no water molecules in their matrix, which could have caused a substantial weight loss at around 70 °C. In terms of adsorption capacities, chemical treatment increased the adsorption capacities of ESM and OP achieving up to 170 μg g?1 (As) and 160 μg g?1 (Se), and 120 μg g?1 (As) and 70 μg g?1 (Se), respectively, with not much activity for ES in terms of adsorption. The two adsorbents (NaOH-treated OP and ESM) were then tested in environmental water samples and the results showed that 68.9 % of As and 74.8 % of Se, and 54.1 % of As and 47.3 % of Se were removed from domestic wastewater samples investigated using OP and ESM, respectively. Moreover, better selectivities towards the compounds of interest were achieved.  相似文献   

12.
Characterisation of mass transfer during subduction is fundamental to understand the origin of compositional heterogeneities in the upper mantle. Fe isotopes were measured in high-pressure/low-temperature metabasites (blueschists, eclogites and retrograde greenschists) from the Ile de Groix (France), a Variscan high-pressure terrane, to determine if the subducted oceanic crust contributes to mantle Fe isotope heterogeneities. The metabasites have δ56Fe values of +0.16 to +0.33‰, which are heavier than typical values of MORB and OIB, indicating that their basaltic protolith derives from a heavy-Fe mantle source. The δ56Fe correlates well with Y/Nb and (La/Sm)PM ratios, which commonly fractionate during magmatic processes, highlighting variations in the magmatic protolith composition. In addition, the shift of δ56Fe by +0.06 to 0.10‰ compared to basalts may reflect hydrothermal alteration prior to subduction. The δ56Fe decrease from blueschists (+0.19 ± 0.03 to +0.33 ± 0.01‰) to eclogites (+0.16 ± 0.02 to +0.18 ± 0.03‰) reflects small variations in the protolith composition, rather than Fe fractionation during metamorphism: newly-formed Fe-rich minerals allowed preserving bulk rock Fe compositions during metamorphic reactions and hampered any Fe isotope fractionation. Greenschists have δ56Fe values (+0.17 ± 0.01 to +0.27 ± 0.02‰) similar to high-pressure rocks. Hence, metasomatism related to fluids derived from the subducted hydrothermally altered metabasites might only have a limited effect on mantle Fe isotope composition under subsolidus conditions, owing to the large stability of Fe-rich minerals and low mobility of Fe. Subsequent melting of the heavy-Fe metabasites at deeper levels is expected to generate mantle Fe isotope heterogeneities.  相似文献   

13.
Temporal variation of PM10 using 2-year data (January, 2007–December, 2008) of Delhi is presented. PM10 varied from 42 to 200 μg m−3 over January to December, with an average 114.1 ± 81.1 μg m−3. They are comparable with the data collected by Central Pollution Control Board (National Agency which monitors data over the entire country in India) and are lower than National Ambient Air Quality (NAAQ) standard during monsoon, close to NAAQ during summer but higher in winter. Among CO, NO2, SO2, rainfall, temperature, and wind speed, PM10 shows good correlation with CO. Also, PM10, PM2.5, and PM1 levels on Deepawali days when fireworks were displayed are presented. In these festive days, PM10, PM2.5, and PM1 levels were 723, 588, and 536 μg m−3 in 2007 and 501, 389, and 346 μg m−3 in 2008. PM10, PM2.5, and PM1 levels in 2008 were 1.5 times lower than those in 2007 probably due to higher mixing height (446 m), temperature (23.8°C), and winds (0.36 ms−1).  相似文献   

14.
During the formation and development of glacial meltwater runoff, hydrochemical erosion is abundant, especially the hydrolysis of K/Na feldspar and carbonates, which can consume H+ in the water, promote the formation of bicarbonate by dissolving atmospheric CO2, and affect the regional carbon cycle. From July 21, 2015, to July 18, 2017, the CO2 concentration and flux were observed by the eddy covariance (EC) method in the relatively flat and open moraine cover area of Koxkar Glacier in western Mt. Tianshan, China. We found that: (1) atmospheric CO2 fluxes ranged from ??408.95 to 81.58 mmol m?2 day?1 (average ? 58.68 mmol m?2 day?1), suggesting that the study area is a significant carbon sink, (2) the CO2 flux footprint contribution areas were primarily within 150 m of the EC station, averaging total contribution rates of 93.30%, 91.39%, and 90.17% of the CO2 flux in the snow accumulation, snow melting, and glacial melting periods, respectively. Therefore, the contribution areas with significant influences on CO2 flux observed at EC stations were concentrated, demonstrating that grassland CO2 flux around the glaciers had little effect at the EC stations, (3) in the predominant wind direction, under stable daytime atmospheric stratification, the measurement of CO2 flux, as interpreted by the Agroscope Reckenholz Tanikon footprint tool, was 79.09% ± 1.84% in the contribution area. This was slightly more than seen at night, but significantly lower than the average under unstable atmospheric stratification across the three periods of interest (89%). The average distance of the farthest point of the flux footprint under steady state atmospheric conditions was 202.61?±?69.33 m, markedly greater than that under non-steady state conditions (68.55?±?10.34 m). This also indicates that the CO2 flux observed using EC was affected primarily by hydrochemical erosion reactions in the glacier area, (4) a good negative correlation was found between net glacier exchange (NGE) of CO2 and air temperature on precipitation-free days. Strong ice and snow ablation could promote hydrochemical reactions of soluble substances in the debris area and accelerated sinking of atmospheric CO2. Precipitation events might reduce snow and ice melting, driven by reduced regional temperatures. However, a connection between NGE and precipitation, when less than 8.8 mm per day, was not obvious. When precipitation was greater than 8.8 mm per day, NGE decreased with increasing precipitation, (5) graphically, the slope of NGE, related to daily runoff, followed a trend: snow melting period?>?snow accumulation period?>?early glacial ablation period?>?late glacier ablation period?>?dramatic glacier ablation period. The slope was relatively large during snow melting, likely because of CO2 sinking caused by water–rock interactions. The chemical reaction during elution in the snow layer might also promote atmospheric CO2 drawdown. At the same time, the damping effect of snow cover and the almost-closed glacier hydrographic channel inhibited the formation of regional runoff, possibly providing sufficient time for the chemical reaction, thus promoting further CO2 drawdown.  相似文献   

15.
Tibetan Plateau (TP) is the highest and most extensive plateau in the world and has been known as the roof of the world, and it is sensitive to climate change. The researches of CO2 fluxes (F C) in the TP region play a significant role in understanding regional and global carbon balance and climate change. Eddy covariance flux measurements were conducted at three sites of south-eastern TP comprising Dali (DL, cropland ecosystem), LinZhi (LZ, alpine meadow ecosystem) and Wenjiang (WJ, cropland ecosystem); amongst those DL and LZ are located in plateau region, while WJ is in plain region. Dynamics of F C and influences of vegetation, meteorological (air temperature, photosynthetically active radiation, soil temperature and soil water content) and terrain factors (altitude) were analysed on the basis of data taken during 2008. The results showed that, in the cool sub-season (March, April, October and December), carbon sink appeared even in December with fluxes of (?0.021 to ?0.05) mg CO2 m?2 s?1 and carbon source only in October (0.03 ± 0.0048) mg CO2 m?2 s?1 in DL and WJ site. In LZ site, carbon sink was observed in April: (?0.036 ± 0.0023) mg CO2 m?2 s?1 and carbon sources in December and March (0.008–0.010 mg CO2 m?2 s?1). In the hot sub-season (May–August), carbon source was observed only in May with (0.011 ± 0.0022), (0.104 ± 0.0029) and (0.036 ± 0.0017) fluxes in LZ, DL and WJ site, respectively, while carbon sinks with (?0.021 ± 0.0041), (?0.213 ± 0.0007) and (?0.110 ± 0.0015) mg CO2 m?2 s?1 fluxes in LZ, DL, and WJ, respectively. Comparing with plain region (WJ), carbon sinks in plateau region (DL and LZ) lasted for a longer time, and the absorption sum was large and up to (–357.718 ± 0.0054) and (?371.111 ± 0.0039) g C m?2 year?1, respectively. The LZ site had the weakest carbon sink with (?178.547 ± 0.0070) g C m?2 year?1. Multivariate analysis of covariance showed that altitude (AL) as an independent factor explained 39.5 % of F C (P < 0.026). F C had a quadratic relationship with Normalized difference vegetation index (NDVI) (R 2 ranges from 0.485 to 0.640 for three sites), an exponential relationship with soil temperature at 5-cm depth (ST 5) at night time and a quadratic relationship with air temperature (T a) at day time. Path analysis indicated that photosynthetically active radiation (PAR), sensible heat fluxes (H) and other factors all had direct or indirect effects on F C in all of the three tested sites around the south-eastern TP.  相似文献   

16.
Aeolian (wind) erosion is most common in arid regions. The resulted emission of PM10 (particulate matter that is smaller than 10 μm in diameter) from the soil has many environmental and socioeconomic consequences such as soil degradation and air pollution. Topsoil resistance to aeolian transport highly depends on the surface composition. The study aim was to examine variations in PM10 fluxes in a desert-dust source due to surface composition and topsoil disturbance. Aeolian field experiments using a boundary layer wind tunnel alongside soil composition analysis were integrated in this study. The results show variations in PM10 fluxes (ranging from 9.5 to 524.6 mg m?2 min?1) in the studied area. Higher wind velocity increased significantly the PM10 fluxes in all surface compositions. A short-term natural disturbance caused changes in the aggregate soil distribution (ASD) and increased significantly PM10 emissions. Considering that PM10 contains clays, organic matter, and absorbed elements, the recorded PM10 fluxes are indicative of the potential soil loss and degradation by wind erosion in such resource-limited ecosystems. The findings have implications in modeling dust emission from a source area with complex surfaces.  相似文献   

17.
Community Oxygen and Nutrient Fluxes in Seagrass Beds of Florida Bay, USA   总被引：1，自引：0，他引：1  
We used clear, acrylic chambers to measure in situ community oxygen and nutrient fluxes under day and night conditions in seagrass beds at five sites across Florida Bay five times between September 1997 and March 1999. Underlying sediments are biogenic carbonate with porosities of 0.7–0.9 and with low organic content (<1.6%). The seagrass communities always removed oxygen from the water column during the night and produced oxygen during daylight, and sampling date and site significantly affected both night and daytime oxygen fluxes. Net daily average fluxes of oxygen (?4.9 to 49 mmol m?2 day?1) ranged from net autotrophy to heterotrophy across the bay and during the 18-month sampling period. However, the Rabbit Key Basin site, located in the west-central bay and covered with a dense Thalassia testudinum bed, was always autotrophic with net average oxygen production ranging from 4.8 to 49 mmol m?2 day?1. In November 1998, three of the five sites were strongly heterotrophic and oxygen production was least at Rabbit, suggesting the possibility of hypoxic conditions in fall. Average ammonium (NH4) concentrations in the water column varied widely across the bay, ranging from a mean of 6.9 μmol l?1 at Calusa in the eastern bay to a mean of 0.6 μmol l?1 at Rabbit Key for the period of study. However, average NH4 fluxes by site and date (?240 to 110 μmol m?2 h?1) were not correlated with water column concentrations and did not vary in a consistent diel, seasonal, or spatial pattern. Concentrations of dissolved organic nitrogen (DON) in the water column, averaged by site (15–25 μmol l?1), were greater than mean NH4 concentrations, and the range of day and night DON fluxes (?920 to 1,300 μmol m?2 h?1), averaged by site and date, was greater than the range of mean NH4 fluxes. Average DON fluxes did not vary consistently from day to night, seasonally or spatially. Mean silicate fluxes ranged from ?590 to 860 μmol m?2 h?1 across all sites and dates, but mean net daily fluxes were less variable and most of the time contributed small amounts of silicate to the water column. Mean concentrations of filterable reactive phosphorus (FRP) in the water column across the bay were very low (0.021–0.075 μmol l?1); but site average concentrations of dissolved organic phosphorus (DOP) were higher (0.04–0.15 μmol l?1) and showed a gradient of increasing concentration from east to west in the bay. A pronounced gradient in average surficial sediment total phosphorus (1.1–12 μmol g DW?1) along an east-to-west gradient was not reflected in fluxes of phosphorus. FRP fluxes, averaged by site and date, were low (?5.2 to 52 μmol m?2 h?1), highly variable, and did not vary consistently from day to night or across season or location. Mean DOP fluxes varied over a smaller range (?8.7 to 7.4 μmol m?2 h?1), but also showed no consistent spatial or temporal patterns. These small DOP fluxes were in sharp contrast to the predominately organic phosphorus pool in surficial sediments (site means?=?0.66–7.4 μmol g DW?1). Significant correlations of nutrient fluxes with parameters related to seagrass abundance suggest that the seagrass community may play a major role in nutrient recycling. Integrated means of net daily fluxes over the area of Florida Bay, though highly variable, suggest that seagrass communities might be a source of DOP and NH4 to Florida Bay and might remove small amounts of FRP and potentially large amounts of DON from the waters of the bay.  相似文献   

18.
Perchlorate and iodide concentrations were determined in brown (Undaria pinnatifida and Laminaria japonica) and red (Porphyra sp.) edible seaweeds, which are commonly consumed by Korean people, with the use of ion chromatography, coupled with a tandem mass spectrometer. Seaweeds (i.e., good sources of iodine) are among the most important plant life in the ocean and commonly consumed as food and nutritional supplement in South Korea. All seaweed samples were purchased from different regions in South Korea. The detected concentrations of perchlorate were as follows: 19.7–620.7 μg kg?1 dry weight (n = 11, mean concentration = 149.2 μg kg?1 dry weight) for L. japonica and 7.3–21.7 μg kg?1 dry weight (mean concentration = 10.6 μg kg?1 dry weight) for U. pinnatifida. Of the 11 samples of Porphyra sp., only 1 sample showed 6.7 μg kg?1 dry weight perchlorate. The concentrations of iodide in all seaweed samples varied from 0.44 to 6,800 mg kg?1 dry weight. L. japonica samples (n = 11) had significantly higher iodide concentrations, with a mean of 5,261 mg kg?1 dry weight. The bioconcentration factor values for perchlorate and iodide in the three different seaweeds varied widely and showed similar variation trends. The trend for perchlorate and iodide was Porphyra sp. < U. pinnatifida < L. japonica. The results have provided growing evidence that perchlorate frequently occurs in food products.  相似文献   

19.
Assessing nitrogen dynamics in the estuarine landscape is challenging given the unique effects of individual habitats on nitrogen dynamics. We measured net N2 fluxes, sediment oxygen demand, and fluxes of ammonium and nitrate seasonally from five major estuarine habitats: salt marshes, seagrass beds (SAV), oyster reefs, and intertidal and subtidal flats. Net N2 fluxes ranged from 332?±?116 μmol?N-N2?m?2?h?1 from oyster reef sediments in the summer to ?67?±?4 μmol?N-N2?m?2?h?1 from SAV in the winter. Oyster reef sediments had the highest rate of N2 production of all habitats. Dissimilatory nitrate reduction to ammonium (DNRA) was measured during the summer and winter. DNRA was low during the winter and ranged from 4.5?±?3.0 in subtidal flats to 104?±?34 μmol?15NH 4 + ?m?2?h?1 in oyster reefs during the summer. Annual denitrification, accounting for seasonal differences in inundation and light, ranged from 161.1?±?19.2 mmol?N-N2?m?2?year?1 for marsh sediments to 509.9?±?122.7 mmol?N-N2?m?2?year?1 for SAV sediments. Given the current habitat distribution in our study system, an estimated 28.3?×?106?mol of N are removed per year or 76 % of estimated watershed nitrogen load. These results indicate that changes in the area and distribution of habitats in the estuarine landscape will impact ecosystem function and services.  相似文献   

20.
Carbendazim and Chlorpyrifos are some of the most widespread environmental contaminants of major concern to human and animal reproductive health. Acute toxicity test results for pesticides were evaluated by the Probit analysis method and 96 h LC50 values for C. chanos exposed to chlorpyrifos was 3.73 and 11.5 μg l?1 for carbendazim. Chlorpyrifos and carbendazim significantly decreased total protein, catalase, glutathione S-transferase and acetyl choline esterase and induced lipid peroxidation. Maximum effects of protein, catalase, lipid peroxidation, acetyl choline esterase and glutathione s-transferase were obtained in response to 23.68 μg l?1 of chlorpyrifos and 43.68 μg l?1 of carbendazim. Micronuclei assay results have shown increased abnormality with increasing doses of chlorpyrifos and carbendazim. Maximum increasing in micronuclei was observed in chlorpyrifos exposed C. chanos. This study showed that chlorpyrifos and carbendazim induced alterations in the activity of antioxidant enzymes and could induce clastogenicity.  相似文献   

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