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Otto Klemm Holger Lange 《Environmental science and pollution research international》1999,6(4):193-199
We analyzed 13 years of hourly measurements of SO2, NOx, and O3, at forest ecosystem research sites in SE Germany. A quasi-continuous data record was obtained by combining data sets from
two locations. Before interpreting trends in the combined data set, we analyzed if the change of location introduced a systematic
bias. We employed autocorrelation functions, Hurst statistics, complexity analysis, and recurrence quantification and found
that the partial data sets exhibited no indication of the presence of any bias. For SO2, we also compared the data from the forest sites with data obtained in nearby cities and also found no indications for any
systematic effects. Applying nonparametric trend statistics we found a significant decrease of the SO2. Most of the observed decrease is due to the reductions of SO2 emissions in eastern Germany, but reductions in western Germany and the Czech Republic also played important roles. For O3, we observed a significant increase, the causes of which are unclear from our data alone. No trend was identified for NOx. 相似文献
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Effect of a full-grown vegetative filter strip on herbicide runoff: maintaining of filter capacity over time 总被引:2,自引:0,他引:2
Narrow vegetative filter strips (VFS) proved to effectively reduce herbicide runoff from cultivated fields mainly due to the ability of vegetation to delay surface runoff, promote infiltration and adsorb herbicides. Since VFS are dynamic systems, their performance would not remain constant over the years indicating the need to define suitable buffer management. In order to evaluate the performance of different five and six year-old VFS, the runoff of the herbicides metolachlor and terbuthylazine was monitored in 2002 and 2003 in an experimental site in northern Italy. The structure of the herbaceous cover in the buffers changes over time. When rows of trees are present, the grass cover is decreased by the shading action of the trees, but the leaf litter gains importance. In VFS with grass cover only, the cover composition changes because of the substitution of grass by broadleaf species. Six metres wide VFS are very effective in reducing runoff volume and concentration during both wet and dry years. Classification analysis showed that runoff concentration and volume are linked to the characteristics of the rainfall event, buffer, source of herbicides and time after application. Regression analysis showed that the significant predictors for runoff volume are rainfall amount and intensity, total vegetal cover in the VFS, crop leaf area index and time after treatment; for concentration they are rainfall intensity, crop leaf area index and total vegetal cover in the VFS. The role of VFS is complex, so appropriate management is required to maintain its increasing filtering capacity over time. 相似文献
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