Research on community characteristics of riparian herbs is an important scientific basis of riparian vegetation rehabilitation. This study aimed to investigate the species diversity and quantitative characteristics of riparian herbs in Liaohe River Conservation Area and its tributaries. Herbaceous communities were investigated by sample line method. Group average clustering analysis and detrended correspondence analysis (DCA) were used to find the major environmental factors affecting the distribution pattern of riparian herbaceous communities. The result showed altogether 154 herbaceous species, belonging to 40 families and 96 genera. The riparian herbaceous species diversity was found to be correlated to river slope, sinuosity and stream order, being lower in rivers of mountain area than in rivers of plain area, and higher in tributaries than in Liaohe River Conservation Area. Clustering analysis classified the herbaceous communities into 23 types, being dominated by hygrophytes including communities of Echinochloa crusgalli, Oenanthe javanica, Polygonum hydropiper, Murdannia keisak, Artemisia selengensis, Scirpus triqueter, Heleocharis soloniensis, Pycreus sanguinolentus, Cyperus fuscus, Phragmites australis, Polygonum amphibium, Carex diandra + Artemisia selengensis and Carex diandra + Rorippa islandica. Correlation analysis between DCA ordination axes and environmental factors showed that the altitude, river slope, sinuosity and stream level were the major environmental factors affecting the distribution pattern of herbaceous communities in the riparian zone of Liaohe River Conservation Area and its tributaries. The results of CCA showed that the contribution ratio of stream level was the highest, followed by altitude and slope, with sinuosity the last. The results suggested that riparian herbaceous characteristics are affected by the comprehensive force of altitude, river slope, sinuosity and stream order, and that Calamagrostis epigeios, Triarrhena sacchariflora and Phragmites australis are suitable species for riparian vegetation rehabilitation. 相似文献
Previous studies demonstrated that short-term exposure to gaseous pollutants (nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3)) had a greater adverse effect on cardiovascular disease. However, little evidence exists regarding the synergy between gaseous pollutants and cardiovascular disease (CVD). Therefore, we aimed to estimate the effect of individual gaseous pollutants on hospital admissions for CVD and to explore the possible synergistic effects between gaseous pollutants. Daily hospitalization counts for CVD were collected from January 1, 2014, to December 31, 2015. We also collected daily time series on gaseous pollutants from the Environment of the People’s Republic of China, including NO2, SO2, and O3. We used distributed lag nonlinear models (DLNMs) to assess the association of individual gaseous pollutants on CVD hospitalization, after controlling for seasonality, day of the week, public holidays, and weather variables. Then, we explored the variability across age and sex groups. In addition, we analyzed the synergistic effects between gaseous pollutants on CVD. Extremely low NO2 and SO2 increase the risk of CVD in all subgroup at lag 7 days. The greatest effect of high concentration of SO2 was observed in male and the elderly (≥ 65 years) at lag 3 days. Greater effects of high concentration of O3 were more pronounced in the young (< 65 years) and female at lag 3 days, while the effect of low concentration of O3 was greater in male and the young (< 65 years) at lag 0 day. We found a synergistic effect between NO2 and SO2 for CVD, as well as between SO2 and O3. The synergistic effects of NO2 and SO2 on CVD were stronger in the elderly (≥ 65) and female. The female was sensitive to synergistic effects of SO2-O3 and NO2-O3. Interestingly, we found that there was a risk of CVD in the susceptible population even for gaseous pollutant concentrations below the National Environmental Quality Standard. The synergy between NO2 and SO2 was significantly associated with cardiovascular disease hospitalization in the elderly (≥ 65). This study provides evidence for the synergistic effect of gaseous pollutants on hospital admissions for cardiovascular disease.
Global climate change (GCC) is expected to influence the fate, exposure and risks of organic pollutants to wildlife and humans. Multimedia chemical fate models have been previously applied to estimate how GCC affects pollutant concentrations in the environment and biota, but previous studies have not addressed how uncertainty and variability of model inputs affect model predictions. Here, we assess the influence of climate variability and chemical property uncertainty on future projections of environmental fate of six polychlorinated biphenyl congeners under different GCC scenarios using a spreadsheet version of the ChemCAN model and the Crystal Ball® software. Regardless of emission mode, results demonstrate: (i) uncertainty in degradation half-lives dominates the variance of modelled absolute levels of PCB congeners under GCC scenarios; (ii) when the ratios of predictions under GCC to predictions under present day climate are modelled, climate variability dominates the variance of modelled ratios; and (iii) the ratios also indicate a maximum of about a factor of 2 change in the long-term average environmental concentrations due to GCC that is forecasted between present conditions and the period between 2080 and 2099. We conclude that chemical property uncertainty does not preclude assessing relative changes in a GCC scenario compared to a present-day scenario if variance in model outputs due to chemical properties and degradation half-lives can be assumed to cancel out in the two scenarios. 相似文献
