Gas exchange rates across the sediment-water and air-water interfaces in south San Francisco Bay
Gas exchange rates across the sediment-water and air-water interfaces in south San Francisco Bay
复制标题
旧金山湾南部沉积物-水和空气-水界面的气体交换率
DOI：
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发表时间：
1984
期刊：
影响因子：
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通讯作者：
D. Hammond
中科院分区：
文献类型：
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作者：
B. Hartman;D. Hammond
在旧金山湾南部的一段地区测量了水和沉积柱中的氡222浓度以及沉积物-水和空气-水界面的氡交换率。已经使用了两种独立的方法来确定沉积物-水交换率，这些方法的年平均值在确定的不确定度范围内一致，约为20%。浅滩区底栖生物的年平均通量几乎是通道区通量的2倍。来自浅滩和河道的通量分别比简单分子扩散的通量高出4和2倍，显然是由于大型动物灌溉。通过在水柱上建立氡质量平衡和用浮室直接测量，确定了空气-水界面上氡交换的气体传递系数。实验室法所得的结果似乎过高。使用质量平衡方法计算的传递系数范围为0.4 m/天至1.8 m/天，6年平均值为1.0 m/天。在3.2-6.4 m/s风速范围内，气体交换与风速呈线性关系，但与流速无关。根据在湖泊和海洋中观测到的气体交换率和风速之间的经验关系预测的气体传递系数与氡质量平衡确定的系数相差不到30%，而且比理论气体交换模型预测的系数要准确得多。
Radon 222 concentrations in the water and sedimentary columns and radon exchange rates across the sediment-water and air-water interfaces have been measured in a section of south San Francisco Bay. Two independent methods have been used to determine sediment-water exchange rates, and the annual averages of these methods agree within the uncertainty of the determinations, about 20%. The annual average of benthic fluxes from shoal areas is nearly a factor of 2 greater than fluxes from the channel areas. Fluxes from the shoal and channel areas exceed those expected from simple molecular diffusion by factors of 4 and 2, respectively, apparently due to macrofaunal irrigation. Values of the gas transfer coefficient for radon exchange across the air-water interface were determined by constructing a radon mass balance for the water column and by direct measurement using floating chambers. The chamber method appears to yield results which are too high. Transfer coefficients computed using the mass balance method range from 0.4 m/day to 1.8 m/day, with a 6-year average of 1.0 m/day. Gas exchange is linearly dependent upon wind speed over a wind speed range of 3.2–6.4 m/s, but shows no dependence upon current velocity. Gas transfer coefficients predicted from an empirical relationship between gas exchange rates and wind speed observed in lakes and the oceans are within 30% of the coefficients determined from the radon mass balance and are considerably more accurate than coefficients predicted from theoretical gas exchange models.