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691.
The response of soil respiration to short-term environmental factors changes has been well studied, whereas the influences
of long-term soil microclimate changes on soil respiration are still highly unclear, especially in tropical ecosystems. We
hypothesized that soil carbon accumulation in southern China, especially in mature forest during recent years, partly resulted
from reducing soil respiration rates. To test this hypothesis, we analyzed the temporal trends and variations of air temperature,
soil temperature and soil water content (hereafter referred to as SWC), and then estimated soil respiration rates in the 1980s
and 2000s with soil temperature and SWC by regression model in three subtropical forests which are at early-, mid-, and advanced-successional
stages, respectively, in Dinghushan Nature Reserve (hereafter referred to as DNR) in southern China. The annual mean ambient
air temperature increased by 1.03 ± 0.15°C in the last 50 years (1954–2007) in DNR. Rainfall amount in the corresponding period
did not change significantly, but rainfall pattern changed remarkably in the last three decades (1978–2007). Soil temperature
is correlated with ambient air temperature. The average SWC was 36.8 ± 8.4%, 34.7 ± 8.1% and 29.6 ± 8.1% in the 1980s, and
then dropped sharply to 23.6 ± 2.9%, 20.5 ± 4.2% and 17.6 ± 3.9% in the 2000s, for the advanced, mid- and early-successional
forests, respectively. Concurrent changes of soil temperature and SWC may have a negative effect on soil respiration rates
for all three forests, implicated that soil respiration may have a negative feedback to regional climate change and carbon
could be sequestered in subtropical forests in southern China. 相似文献
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Yang F Shen R Long Y Sun X Tang F Cai Q Yao S 《Journal of environmental monitoring : JEM》2011,13(2):440-445
Magnetic microsphere confined ionic liquid was synthesized by covalently bonding N-methylimidazolium on magnetic microspheres. The functionalized magnetic microspheres were characterized by Fourier transform infrared (FT-IR) spectrometry, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The prepared material was used for the preconcentration of three chlorophenols (CPs) in water combined with high-performance liquid chromatography (HPLC). Several conditions that probably affected the extraction efficiency such as standing time, eluent and its volume, sample pH and volume, were optimized. Under the optimal conditions, good recoveries (70.3-88.8%) were achieved with satisfactory relative standard deviations (RSDs) of less than 6.0%. The limits of detection for the three CPs were 0.20-0.35 μg L(-1). The results indicated that the ionic liquid-functionalized magnetic microspheres show significant promise for the analysis of CPs in environmental samples. 相似文献
694.
Tracing sources of coal combustion using stable sulfur isotope ratios in epilithic mosses and coals from China 总被引:1,自引:0,他引:1
Xiao HY Tang CG Zhu RG Wang YL Xiao HW Liu CQ 《Journal of environmental monitoring : JEM》2011,13(8):2243-2249
In China, coal combustion is the most important source of atmospheric sulfur pollution. Moss sulfur isotopic signatures have been believed to hold source-specific information that can serve as a fingerprint to identify atmospheric sulfur sources. In cities where only local coals were combusted, we observed a good correspondence of average sulfur isotope ratios in urban mosses (Haplocladium microphyllum) to the values of local coals (δ(coals) = 1.455δ(mosses)- 3.945, R(2) = 0.975, p = 0.01). But if different types of coals were combusted, we did not know whether moss sulfur isotope ratios can indicate mixed coals. To confirm this, using a mixing model we estimated the ratios of imported coal to local coals at cities where both coals were used. We found that the estimated ratios at large cities (>1 million people) where both coals were used were similar to the reported ratios in their respective provinces. For small cities (<0.5 million people) in Jiangxi Province and other provinces, the estimated ratios were higher than the reported ratios because the relatively cheaper local coals were less used in all the small cities except in cities where local coal deposits were found nearby. The comparison results showed that moss sulfur isotope is a useful tool for indicating coal-derived sulfur even in cities where mixed coals were combusted. 相似文献
695.
Pan X Tang J Li J Zhong G Chen Y Zhang G 《Journal of environmental monitoring : JEM》2011,13(4):886-893
62 riverine and marine sediments were collected from the Laizhou Bay area, where the largest manufacturing base of brominated flame retardants (BFRs) in Asia is located. Eight polybrominated diphenyl ethers (PBDEs) were analyzed to investigate the impact of rapidly-developed bromine industries on the regional aquatic system. PBDE concentrations varied largely in riverine sediments. Σ(7)PBDEs (including BDE 28, 47, 99, 100, 153, 154 and 183) and BDE 209 ranged from 0.01 to 53 ng g(-1) dw and from 0.74 to 285 ng g(-1) dw with a mean value of 4.5 ng g(-1) dw and 54 ng g(-1) dw, respectively, indicating a strong influence of direct pollution discharges from local factories. In marine sediments, Σ(7)PBDEs and BDE 209 ranged from not detected (nd) to 0.66 ng g(-1) dw and from 0.66 to 12 ng g(-1) dw with a mean value of 0.32 ng g(-1) dw and 5.1 ng g(-1) dw, respectively. PBDE concentrations were mostly <10 ng g(-1) dw for Σ(7)PBDEs and <50 ng g(-1) dw for BDE 209, which are at a relatively low level for monitored riverine and coastal sediments around the world. Even at the most contaminated sites in Laizhou Bay area, PBDE concentrations were not among the highest concentrations reported in the literature. Congener compositions were dominated by BDE 209 (57.2-99.9% of the sum of BDE congeners), with minor contributions from penta- and octa-BDE products. Tri- to octa-BDE congeners were well correlated among each other (r > 0.75) and thus sources from similar mixing of penta- and octa-BDE products were suggested in this area. Compared with riverine sediments, a much better correlation between PBDE concentrations with TOC was observed in marine environment. The congener pattern changed and their correlation coefficients among each other were remarkably reduced. Contributions of BDE 28, 47 and 99 to Σ(7)PBDEs were generally the same in almost all the marine sites, while it was distinctively higher for BDE 153. These are probably attributable to several reasons, such as contributions by atmospheric deposition and/or redistribution between particles of various sizes during and/or after fluvial transportation combined with the difference of physiochemical properties of BDE congeners. 相似文献
696.
Joint effects of Penta-BDE and heavy metals on Daphnia magna survival, its antioxidant enzyme activities and lipid peroxidation 总被引:1,自引:0,他引:1
Baohua Tang Lingyan Zhu Qixing Zhou 《Frontiers of Environmental Science & Engineering》2011,5(1):99-110
The joint toxicity of Penta-BDE (Pe-BDE) and heavy metals including cadmium and copper on Daphnia magna (D. magna) was evaluated on the basis of determining the 48 h survival, antioxidative enzyme responses, and lipid peroxidation. The response was classified as additive, greater than additive, or less than additive by comparing the measured ??toxic units, TU?? with one. Based on the survival of D. magna, less-than-additive interactions were found in most of mixtures treatments. This may be attributed to the different toxicity mechanism between Pe-BDE and metals. Cu and Cd played a greater role in toxicity than what Pe-BDE did. As for the superoxide dismutase (SOD) and catalase (CAT) activity, most response was less than additive. For the glutathione S-transferases (GST) activity, most of the greater-thanadditive responses were found in the Cu plus Pe-BDE treatments, but the additive responses occurred in Cd plus Pe-BDE treatments and binary metal treatments. For lipid peroxide levels, which were measured as malondialdehyde (MDA) levels, less-than-additive response occurred in the 50% Cd plus 50% Cu and ternary mixture treatments. Results suggested that Pe-BDE, Cd, and Cu could induce different patterns of antioxidant enzyme responses, such as antioxidant/prooxidant responses, depending on their capability to produce reactive oxygen species and antioxidant enzymes to detoxify them. 相似文献
697.
Assessment of heavy metals in sediments from a typical catchment of the Yangtze River, China 总被引:2,自引:0,他引:2
Ying Wang Zhifeng Yang Zhenyao Shen Zhenwu Tang Junfeng Niu Fan Gao 《Environmental monitoring and assessment》2011,172(1-4):407-417
An intensive investigation was conducted to study the accumulation, speciation, and distribution of various heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in sediments from the Yangtze River catchment of Wuhan, China. The potential ecological risks posed by these heavy metals also were estimated. The median concentrations of most heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) were higher than the background values of soils in Wuhan and were beyond the threshold effect level (TEL), implying heavy metal contamination of the sediments. Carbonate-bound Cd and exchangeable Cd, both of which had high bioavailability, were 40.2% and 30.5% of the total for Cd, respectively, demonstrating that Cd poses a high ecological risk in the sediments. The coefficients of the relationship among Pb, Hg, and Cu were greater than 0.797 using correlation analysis, indicating the highly positive correlation among these three elements. Besides, total organic carbon content played an important role in determining the behaviors of heavy metals in sediments. Principal component analysis was used to study the distribution and potential origin of heavy metals. The result suggested three principal components controlling their variability in sediments, which accounted for 36.72% (factor 1: Hg, Cu, and Pb), 28.69% (factor 2: Cr, Zn, and Ni), and 19.45% (factor 3: As and Cd) of the total variance. Overall, 75% of the studied sediment samples afforded relatively low potential ecological risk despite the fact that generally higher concentrations of heavy metals relative to TEL were detected in the sediments. 相似文献
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