Seasonal climatic effects on the hydrology of a rain garden

This paper evaluates the performance and winter hydrology of two small‐scale rain gardens in a cold climate coastal area in Trondheim, Norway. One rain garden received runoff from a small residential watershed over a 20 month study period while the second rain garden with a shorter study period of 7 months was used as a control. The objective of the study was to investigate the extent to which cold climatic conditions would influence the hydrology and performance of the rain gardens. The hydraulic detention, storm lag time and peak flow reduction were measured and compared seasonally. No significant difference between seasonal lag time could be found, but there was a clear decreasing trend in lag time between rain, rain‐on‐snow and snowmelt. The average peak flow reduction for 44 storms in the study period was 42% compared to 27% for the winter seasons, indicating that the performance of the rain garden is reduced in the cold season (below 0 °C). The average hydraulic detention time for the rain garden was 0·84 ( ± 0·73) with runoff inflow and 1·91 ( ± 3·1) with only precipitation. A strong positive correlation was found between the time since the last wetting event and lag time, and between air temperature and hydraulic detention. This indicates that the time between events and seasonal air temperatures are key parameters in the hydraulic performance of cold climate rain gardens. The rain gardens were not used for snow storage areas, and a volume requirement for this was not evaluated in the study. Copyright © 2007 John Wiley & Sons, Ltd.     

Lignin degradation products as palaeoenvironmental proxies in the sediments of small lakes

The quantity and quality of lignin phenols (Σ8, Λ, S/V, C/V and (Ad/Al)_v) in the sediments of three small Lobelia lakes with neither inlets nor outlets were investigated and compared with palynological data and lithology of the profiles. The method of alkaline CuO oxidation was used. Substantial differences with respect to sedimentary lignin concentration and provenance recorded along the profiles and among the sites are in good agreement with pollen data describing the dominant type of vegetation and with indices of soil erosion in the lakes’ catchments. This relation shows that the compositions of lignin degradation products in these lakes are closely related to the local environmental conditions. In all the lakes gymnosperm wood is the main source of lignin products; however, each lake is characterized by different S/V index values. Especially good correlations were obtained between pine pollen proportions in sediments and the S/V index. The correlation between the C/V and (Ad/Al)_v indices indicates a higher degradation of organic matter when non-woody tissue is more abundant. This pilot study illustrates the usefulness and potential for a wider application of lignin oxidation products in palaeoecological reconstructions. This kind of data would be of special importance when investigating local presence/absence of woody plants and the role of angiosperms/gymnosperms in local vegetation. Estimates of lignin biodegradation levels, as well as the data on diagenetic processes, may afford supplementary information on possible disturbances in sedimentation.     

Precipitation trends using in-situ and gridded datasets

Six in situ precipitation time series of varying time periods in the northwestern region and the Global Precipitation Climatology Centre (GPCC) v6 0.5° monthly dataset (1901–2010) were statistically examined for monotonic trends in Trinidad. The Pettit test was used to investigate the abrupt changes in the mean while the Mann–Kendall test was employed to assess the monotonic trends. It was found that three in situ stations and the six grids experienced abrupt changes in the rainfall patterns and that there was an apparent shift in the seasons. In addition, for five out of the six in situ stations no monotonic change was detected in the monthly, seasonal, and annual rainfall patterns. Gradual decreases were detected in the calculated weighted area average for five stations, the GPCCv6 dataset and St. Ann’s time series. The GPCCv6 data indicated that the dry season in the southern Trinidad is becoming drier. Results also suggested that the range between the greatest and lowest recorded rainfall values for some months have increased while others decreased. The gridded dataset appears to give a good representation of the dry season (January to May) rainfall compared with the wet season (June to December) and was found to be negatively biased for the north-western region but may not necessarily be so for the entire island. The results suggested that in the north-western region mirco-climates may exist. It is recommended that further investigations are needed using in situ data.     

横墙对框架结构动力响应的影响分析

填充墙具有显著的刚度和承载力贡献。建筑结构震害调查发现,不开洞横墙的破坏程度远小于开洞纵墙的破坏程度,从宏观现象可判断大部分多层建筑的破坏主要由结构纵向运动造成。为研究横墙在地震作用下的性能及其对结构整体动力响应的影响,以经受2021年5月21日云南漾濞6.4级地震震害的花椒园小学教学楼为研究对象,按当地抗震计算参数进行弹塑性时程分析。采用等效斜压杆模拟横向填充墙,设置无填充墙框架结构、带黏土砖墙的框架结构、带空心砖墙的框架结构和带加气混凝土砌块填充墙的框架结构模型,选取10组地震波横向输入。研究结果表明,4种结构自振周期均处于具有统计学意义的平台段,平均加速度响应较接近,质量和刚度变化不会使结构加速度产生规律的变化;受结构自重影响,无填充墙的框架结构底部剪力小于带填充墙的框架结构,带填充墙的框架结构位移远小于无填充墙的框架结构;带有多道不开洞横墙的多层框架结构的破坏主要是由结构纵向破坏引起的。