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11.
David Haynes Peter Ralph Joelle Prange Bill Dennison 《Marine pollution bulletin》2000,41(7-12):288-293
The impact and recovery from exposure to the herbicide diuron [DCMU; 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea] was assessed for three tropical seagrasses, maintained in outdoor aquaria over a 10-day period. Photosynthetic stress was detected using chlorophyll a fluorescence, measured with a Diving-PAM (pulse amplitude modulated fluorometer). Exposure to 10 and 100 μg l−1 diuron resulted in a decline in effective quantum yield (ΔF/Fm′) within 2 h of herbicide exposure in Cymodocea serrulata, Halophila ovalis and Zostera capricorni. Effective quantum yield also declined over the first 24 h of exposure in H. ovalis at even lower diuron concentrations (0.1 and 1.0 μg l−1). Effective quantum yield in H. ovalis and Z. capricorni was significantly depressed at all diuron concentrations (0.1–100 μg l−1) after 5 days exposure, whereas effective quantum yield in C. serrulata was only significantly lower in plants exposed to highest diuron concentrations (10 and 100 μg l−1). Effective quantum yield depression was present 5 days after plants exposed to 10 and 100 μg l−1 diuron were returned to fresh seawater. These results indicate that exposure to herbicide concentrations present in nearshore Queensland sediments present a potential risk to seagrass functioning. 相似文献
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Jochen F. Müller Caroline Gaus Joelle A. Prange Olaf Ppke Ka Fai Poon M. H. W. Lam Paul K. S. Lam 《Marine pollution bulletin》2002,45(1-12)
Concentrations of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were determined in 14 sediment samples collected from four sites in the Mai Po Marshes Nature Reserve (within a RAMSAR Site) and from another six sites in Victoria Harbour and along the Hong Kong coastline. Elevated levels of PCDDs, and particularly OCDD, were detectable in all samples collected from the Mai Po Marshes and five of the six sites. In contrast to PCDDs, PCDFs were mainly found in sediment samples collected from industrial areas (Kwun Tong and To Kwa Wan) in Victoria Harbour. PCDD/F levels and congener profiles in the samples from the Mai Po Marshes Nature Reserve in particular show strong similarities to those reported in studies which have attributed similar elevated PCDD concentrations to nonanthropogenic PCDD sources. 相似文献
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Particulate organic and black carbon concentrations in rain were determined in various source or remote regions, in order to gain information on the incorporation of atmospheric carbonaceous particles in hydrometeors. The analyses of rainwaters indicate that all the samples contained particles derived from combustion. Data obtained on a sample basis, show an important areal and temporal variability of the composition of rain carbonaceous particles, a variability which is reported to that of the black carbon to total carbon ratio, Cb/Ct, ranging from 10 to 72%. In addition to the fluctuations of the aerosol atmospheric burden, these variations may be related to alterations of the organic fraction of the particles or their involvement in in-cloud nucleation processes during atmospheric transport. Also, a comparison of the mean relative abundance of black carbon in aerosols and in rainwaters, gives evidence of a partial disappearance of the organic particles, a phenomenon which could be due to their dissolution when incorporated in the hydrometeors. Precipitation scavenging ratio values of black carbon particles, which range from 100 to 370, are similar to those found for sulphate anthropogenic aerosols. Due to their hygroscopic properties and mean size, black carbon aerosols could possibly trace the physico-chemical processes involved in the incorporation of fine combustion particles into hydrometeors. It is also suggested that smoke particles may act as cloud condensation nuclei (CCN). Consequently, emissions of particulates derived from combustion in some tropical or industrial regions could result locally in alteration of cloud albedo and precipitation regimes. 相似文献
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Georges Durry Alain Hauchecorne Joelle Ovarlez Henri Ovarlez Ivan Pouchet Virginie Zeninari Bertrand Parvitte 《Journal of Atmospheric Chemistry》2002,43(3):175-194
Telecommunication laser diodes emitting near 1.39 m and 1.65 m in combination with direct-differential absorption spectroscopy are efficient tools to monitor in situ stratospheric H2O andCH4 with a good precision error (a few percents), a high temporal resolution (ranging from 10 ms to 1 s), a large dynamic range in the concentration measurements (four orders of magnitude) and a high selectivity in the analyte species. To illustrate the capability of laser probing technique, we report balloonborne H2Oand CH4 simultaneous measurements obtained on October 2001 atmidlatitudes (43° N). The H2O vertical profile achieved with the lasersensor in the lower stratosphere is compared with the H2O data yielded by a balloonborne frost-point hygrometer. The total hydrogen mixing ratio in the lower stratosphere, 2[CH4] + [H2O], appears to beconstant at 7.5 ± 0.1 ppmv. Nevertheless, an unexpected largedehydration of 0.5 ppmv was detected by both the laser sensor and thehygrometer between 16 km and 23 km. We suspect the occurrence of a tropicalair intrusion into mid-latitudes. We support this interpretation using a high-resolution advection model for potential vorticity. 相似文献