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1.
Th sorption and export models in the water column: A review 总被引：2，自引：3，他引：2
Nicolas Savoye Claudia Benitez-Nelson Adrian B. Burd J. Kirk Cochran Matthew Charette Ken O. Buesseler George A. Jackson Matthieu Roy-Barman Sabine Schmidt Marc Elskens 《Marine Chemistry》2006,100(3-4):234
Over the past few decades, the radioisotope pair of 238U / 234Th has been widely and increasingly used to describe particle dynamics and particle export fluxes in a variety of aquatic systems. The present paper is one of five review articles dedicated to 234Th. It is focused on the models associated with 234Th whereas the companion papers (same issue) are focused on present and future methodologies and techniques (Rutgers van der Loeff et al.), C / 234Th ratios (Buesseler et al.), 234Th speciation (Santschi et al.) and present and future applications of 234Th [Waples, J.T., Benitez-Nelson, C.R., Savoye, N., Rutgers van der Loeff, M., Baskaran, M., Gustafsson, Ö., this issue. An Introduction to the application and future use of 234Th in aquatic systems. Marine Chemistry, FATE special issue]. In this paper, we review current 234Th scavenging models and discuss the relative importance of the non-steady state and physical terms associated with the most commonly used model to estimate 234Th flux. Based on this discussion we recommend that for future work the use of models should be accompanied by a discussion of the effect that model and data uncertainty have on the model results. We also suggest that future field work incorporate repeat occupations of sample sites on time scales of 1–4 weeks in order to evaluate steady state versus non-steady state estimates of 234Th export, especially during high flux events (> ca. 800 dpm m− 2 d− 1). Finally, knowledge of the physical oceanography of the study area is essential, particularly in ocean margins and in areas of established upwelling (e.g., Equatorial Pacific). These suggestions will greatly enhance the application of 234Th as a tracer of particle dynamics and flux in more complicated regimes. 相似文献
2.
A. Waltrop S. K. Mitra A. I. Flossmann H. R. Pruppacher 《Journal of Atmospheric Chemistry》1991,12(1):1-17
An experimental study involving the Mainz vertical wind tunnel is described where the rate of SO2 removed from the air by freely suspended water drops was measured for SO2 concentrations in the gas phase ranging between 50 and 500 ppb, and for various H2O2 concentrations in the liquid phase. In a first set of experiments, the pH inside the SO2 absorbing drops was monitored by means of colour pH indicators added to the drops. In a second set of experiments, the amount of SO2 scavenged by the drops was determined as sulfate by an ionchromatograph after the drops had been removed from the vertical air stream of the wind tunnel after various times of exposure to SO2. The results of our experimental study were compared with the theoretical gas diffusion model of Walcek and Pruppacher which was reformulated for the case of SO2 concentrations in the ppbv(v) range for which the main resistance to diffusion lies in the gas phase surrounding the drop. Excellent agreement between experiment and theory was obtained. Encouraged by this agreement, the theory was used to investigate the rate of sulfate production inside a drop as a function of pH. The sulfate production rate, which includes transport and oxidation, was compared with the production rate based on bulk equilibrium, as cited in the literature. 相似文献
3.
Pb and Th in settling particles in the western Northwest Pacific Ocean: Particle flux and scavenging
A mooring of three conical time-series sediment traps was deployed at two sites in the western Northwest Pacific Ocean for 9 months. Total mass fluxes and activities of 210Pb and 230Th were determined for the settling particles to elucidate their scavenging and transport processes. Sediment samples also were analyzed for 210Pb activities. Total mass fluxes, 210Pb fluxes and 230Th fluxes showed large seasonal variations and their weighted mean fluxes tended to increase with depth, with an especially large increase near-bottom. The ratios of the observed 210Pb fluxes to the 210Pb deficiency fluxes in the upper traps at the two sites were only 0.02 and 0.12, and were attributable to advective export of 210Pb from the surface waters. Those ratios in the near-bottom traps ranged between 1.22 and 2.63. This suggests that these high ratios are due to effective particle scavenging, large lateral 210Pb import and input of resuspended particles that have not become incorporated into the sediments. The mean total 230Th fluxes at the near-bottom traps were 4.2–6.7 times higher than that expected from production in the overlying water column. The 210Pb activities in the surficial sediments were much lower than those in the near-bottom traps. The 210Pb accumulation rates estimated from the excess 210Pb inventory in the sediment column were 40–70% higher than the mean 210Pb fluxes at the near-bottom traps. The ratios of the 210Pb accumulation rates to the 210Pb deficiency fluxes at the near-bottom traps ranged between 2.0 and 3.7. The high fluxes of particulate 210Pb and 230Th at the near-bottom traps reflected a combination of enhanced scavenging of dissolved nuclides and the lateral redistribution of particulate matter by downslope and alongshore transports. However, it was not possible to discriminate among the various processes contributing to high nuclide fluxes. 相似文献
4.
探讨了太阳能、振动能和气流能等3种潜在的环境能量及其利用方法。这些方法可有效解决传感器网络节点需要足够持续的能量而传统的电池供能方式不能满足的实际问题。 相似文献
5.
J. J. Martin P. K. Wang H. R. Pruppacher A. E. Hamielec 《Pure and Applied Geophysics》1980,118(2):1109-1129
A theoretical model is presented which allows computing the efficiency with which aerosol particles of radius 0.1r10 m are collected by simple ice crystal plates of radius 50a
c
640 m in air of various relative humidities, temperatures and pressures. Particle capture due to thermophoresis, diffusiophoresis and inertial impaction are considered. It is shown that the capture efficiency of an ice crystal in considerably affected by phoretic effects in the range 0.1r1 m. For aerosol particles ofr>1 m the efficiency is strongly controlled by the flow field around the crystal and the density of the aerosol material. Trajectory analysis also predicts that aerosol particles are preferentially captured by the ice crystal rim. Our theoretica results are found to agree satisfactorily with the laboratory studies presently available. Comparison shows that for the same pressure, temperature and relative humidity of the ambient air ice crystal plates are better aerosol particle scavengers than water drops. 相似文献
6.
Dissolved and particulate Mn and Fe in the nearshore waters were determined at 27 stations along the west coast of Taiwan during 19-23 November 2004. The latitudinal distributions of Mn and Fe were very similar; however, the concentration in the dissolved phase was lower, whereas that in the particulate phase was higher in the northern regime. The higher percentage of Fe than Mn that was associated with particles resulted in a two-order of magnitude higher particle-water partition coefficient for Fe, Kd(Fe), than that for Mn, Kd(Mn). The removal fluxes of Mn and Fe could be estimated by multiplying the particulate 234Th removal flux with the Mn/234Th and Fe/234Th ratios in suspended particles, which ranged from 0.1 to 3.8 mmol m−2 d−1 for Mn, and from 3.4 to 194.5 mmol m−2 d−1 for Fe. Residence times ranged from 1 to 20 days for Mn and Fe were estimated in the nearshore. 相似文献
7.
利用2016—2018年常州市区环境空气细颗粒物数据,结合同期地面气象资料,分析了常州市区PM2.5以及气象因素的变化特征,并统计分析气象因素对PM2.5浓度的影响。结果表明：常州市区PM2.5、降水量、相对湿度和气温等具有明显季节性,呈夏季较高冬季较低,而气压夏季较低冬季较高的特征。相对湿度与PM2.5呈正相关,即随着相对湿度的增加PM2.5超标率和平均浓度均增加;降水对PM2.5具有一定的清除作用,清除率与降水前PM2.5浓度、降水量、降水强度有关,降水量、降水强度越大,则降水清除效果越好,而降水前PM2.5浓度较小,则清除率不明显;常州市区偏西风时PM2.5的超标率和平均浓度较其他风向较高;风速对常州市区PM2.5的影响呈负相关,即风速越大PM2.5超标率和平均浓度均减小;常州市区地面天气形势可以分为两种类型,第一种类型表现为气压较低气温较高,PM2.5超标率以及平均浓度相对较低,而第二种类型表现为气压较高气温较低,PM2.5超标率以及平均浓度相对较高。 相似文献
8.
Scavengers perform an important role in deep-sea ecosystems, recycling carrion. However, scavenged material can be difficult to discern from predation. The synaphobranchid eel Diastobranchus capensis Barnard, 1923, is common bycatch in deep-water fisheries for orange roughy (Hoplostethus atlanticus Collett, 1889) in New Zealand waters. Despite anecdotal reports of scavenging in D. capensis, their ecology and feeding are little known. Scavenged material was estimated to be approximately 39 per cent (by weight) of the diet of D. capensis from northeastern Chatham Rise, New Zealand, from water depths of 1062–1196 m. Scavenged material was defined as fragmentary food items from animals and plants either not normally available to the eel, or from animals larger than the eel consuming them (e.g., fish heads and tails, spent squid spermatophores, beaks and tentacle crowns, and seaweed). D. capensis were primarily piscivorous, with the diet supplemented by squid, natant decapods and mysids. The weight or number of food items did not increase with the size of the eel, nor was there any major ontogenetic shift in the composition of the diet. D. capensis probably plays an important role in mid-slope communities, recycling carrion. 相似文献
9.
Both aerosol and rainwater samples were collected and analyzed for ionic species at a coastal site in Southeast Asia over
a period of 9 months (January–September 2006) covering different monsoons. In general, the occurrence and distribution of
ionic species showed a distinct seasonal variation in response to changes in air mass origins. Real-time physical characterization
of aerosol particles during rain events showed changes in particle number distributions which were used to assess particle
removal processes associated with precipitation, or scavenging. The mean scavenging coefficients for particles in the range
10–500 nm and 500–10 μm were 7.0 × 10−5 ± 2.8 × 10−5 s−1 and 1.9 × 10−4 ± 1.6 × 10−5 s−1, respectively. A critical analysis of the scavenging coefficients obtained from this study suggested that the wet removal
of aerosol particles was greatly influenced by rain intensity, and was particle size-dependent as well. The scavenging ratios,
another parameter used to characterize particle removal processes by precipitation, for NH4
+, Cl−, SO4
2−, and NO3
− were found to be higher than those of Na+, K+, and Ca2+ of oceanic and crustal origins. This enrichment implied that gaseous species NH3, HCl, and HNO3 could also be washed out readily. These additional sources of ions in precipitation presumably counter-balanced the dilution
effect caused by high total precipitation volume in the marine and tropical area. 相似文献
10.