Niemistö Juha P, Horppila Jukka
Department of Biological and Environmental Sciences/Limnology, P.O. Box 65 (Viikinkaari 1), FIN 00014, University of Helsinki, Finland.
J Environ Qual. 2007 Jul 17;36(5):1318-23. doi: 10.2134/jeq2006.0487. Print 2007 Sep-Oct.
The effect of ice cover on sediment resuspension and internal total P (Tot-P) loading was studied in the northern temperate Kirkkojärvi basin in Finland. The gross sedimentation and resuspension rates were estimated with sediment traps during ice-cover and ice-free periods. After ice break, the average gross sedimentation rate increased from 1.4 to 30.0 g dw m(-2) d(-1). Resuspension calculations showed clearly higher values after ice break as well. Under ice cover, resuspension ranged from 50 to 78% of the gross sedimentation while during the ice-free period it constituted from 87 to 97% of the gross sedimentation. Consequently, the average resuspension rate increased from 1.0 g dw m(-2) d(-1) under ice-cover to 27.0 g dw m(-2) d(-1) after thaw, indicating the strong effect of ice cover on sediment resuspension. To estimate the potential effect of climate change on internal P loading caused by resuspension we compared the Tot-P loading calculations between the present climate and the climate with doubled atmospheric CO2 concentration relative to the present day values (ice cover reduced from current 165 to 105 d). The annual load increased from 7.4 to 9.4 g m(-2). In conclusion, the annual internal Tot-P loading caused by resuspension will increase by 28% in the Kirkkojärvi basin if the 2xCO2 climate scenario comes true.
在芬兰北部温带的基尔科耶尔维盆地，研究了冰盖对沉积物再悬浮和内部总磷（Tot-P）负荷的影响。在冰封期和无冰期，使用沉积物捕获器估算了沉积物的总沉降和再悬浮速率。冰融化后，平均总沉降速率从1.4克干重每平方米每天增加到30.0克干重每平方米每天（dw表示干重）。再悬浮计算结果也清楚地表明，冰融化后的数值更高。在冰盖下，再悬浮量占总沉降量的50%至78%，而在无冰期，这一比例为总沉降量的87%至97%。因此，平均再悬浮速率从冰盖下的1.0克干重每平方米每天增加到解冻后的27.0克干重每平方米每天，这表明冰盖对沉积物再悬浮有强烈影响。为了估算气候变化对再悬浮引起的内部磷负荷的潜在影响，我们比较了当前气候条件下以及大气二氧化碳浓度相对于当前值翻倍（冰盖天数从目前的165天减少到105天）的气候条件下的总磷负荷计算结果。年负荷从7.4克每平方米增加到9.4克每平方米。总之，如果二氧化碳浓度翻倍的气候情景成为现实，则基尔科耶尔维盆地因再悬浮导致的每年内部总磷负荷将增加28%。
