关键词：
Africa;Asia;Cd;Cr;Cu;Europe;Fe;Fertilizer and pesticide use;Global pollution;Health risk;Heavy metal regulation;Lake pollution;Mining and manufacturing;Mn;Ni;North America;Pb;Pollution history;Pollution-control measure;River pollution;Rock weathering;Source apportionment;South America;Waste discharge;Zn
摘要：
Heavy metal pollution in surface water is a global environmental problem. This study analyzed the trends, health risks, and sources of eight dissolved heavy metal species in river and lake water across five continents (Africa, Asia, Europe, North America, and South America; Oceania was excluded owing to a lack of data) for the period 1970-2017. We wanted to assess the effects of various implemented countermeasures to pollution and to determine those that could be adopted worldwide. Collectively, the water system showed increasing trends for Cd, Cr, Cu, Ni, Mn, and Fe and decreasing trends for Pb and Zn. The mean dissolved concentrations of most heavy metals were highest in Asia and lowest in Europe. Most heavy metals had low non-carcinogenic risks over this period. The cancer risks associated with Pb were lower than the hazardous level on all five continents over the five decades, whereas the cancer risks related to Cr exceeded the hazardous level in the 1970s, 2000s, and 2010s, and in Africa, Asia, and North America over the entire period. Mining and manufacturing were consistently found to be critical sources of metal pollution from 1970 to 2017. However, the heavy metal sources differed significantly by continent, with waste discharge and rock weathering dominant in Africa; mining and manufacturing, along with rock weathering, are dominant in Asia and South America; fertilizer and pesticide use, along with rock weathering, are dominant in North America; and mining and manufacturing, waste discharge, and rock weathering are dominant in Europe. Global trends in the metal loadings in water and in relevant pollution-control measures suggest that countermeasures in Europe have successfully controlled heavy metal pollution. The successful measures include implementing rigorous standards for metal emissions, limiting the metal concentrations in products, and rigorously treating metal-contaminated waste. Therefore, the measures implemented in Europe should be extended worldwide to treat heavy metal pollution in water.
摘要：
Human activities alter the growth of coastal wetland vegetation. In the present study, we used a spectrometer and hyperspectral data to determine and compare the biomass of Suaeda salsa in a coastal wetland under protective and destructive activities. Using typical discriminants, the hyperspectral data of Suaeda salsa were distinguished under the influence of two kinds of human activity, and the accuracy of the inversion model of biomass was established following improved differentiation of the data under the influence of human activities. The original spectral reflectance and vegetation index were selected, and the biomass-inversion model was established by linear regression and partial least-squares regression. The model established by partial least-squares regression had a good precision (R-2 > 0.85, RMSE% < 5.6%). Hyperspectral technology can accurately show plant biomass and the indirect effects of interference by human activities of different intensity on coastal wetlands. The accuracy of the models can be improved by distinguishing the vegetation patterns under the influence of different types of human activity, and then constructing the biomass models. This study provides technical support for the use of quantitative remote sensing-based methods to monitor the fragile ecology of coastal wetlands under the influence of human activities.
作者机构：
[吴爱平; 邹冬生; 李有志] Hunan Provincial Key Laboratory of Rural Ecosystem Health in Dongting Lake Area, College of Bioscience and Biotechnology, Hunan Agricultural University, Changsha, 410128, China;[郑华] State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China;[张凯] College of Grassland and Environment Sciences, Xinjiang Agricultural University, Urumqi, 830052, China;[向丹] College of Resources and Environment, Qingdao Agricultural University, Qingdao，Shandong266109, China;[陈法霖] Hunan Provincial Key Laboratory of Rural Ecosystem Health in Dongting Lake Area, College of Bioscience and Biotechnology, Hunan Agricultural University, Changsha, 410128, China, State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
通讯机构：
[Zheng, H.] S;State Key Laboratory of Urban and Regional Ecology, China
摘要：
The vegetation of wetlands show strong zonation patterns, but the mechanisms determining these patterns are not fully understood. In the present study, growth and morphological responses to a water level gradient (-20 cm (i.e. water level 20 cm below soil surface), -10 cm, 0 cm, 10 cm, 20 cm) were compared between a higher elevation plant (Imperata cylindrica) and a lower elevation plant (Carex brevicuspis) in the Dongting Lake wetlands of China. For both species, the aboveground, belowground, and total biomass were greater at -10 cm than at any other water level.. However, when the water level increased from -10 cm to 0 cm, there was a greater decrease in the biomass of I. cylindrica than in that of C. brevicuspis. Plant height, tiller number, leaf length, leaf width and leaf area showed greater variation along the water level gradient in I. cylindrica than in C. brevicuspis. Generally, with increasing water level, root length, rhizome number, and adventitious root biomass and number all decreased in I. cylindrica. However, in C. brevicuspis, neither the rhizome number nor the primary adventitious root biomass differed significantly among the five water levels. These results indicate that I. cylindrica have a lower tolerance for flooding and higher water sensitivity than C. brevicuspis and these differences may explain why I. cylindrica is found at relatively higher elevations that are not prone to flooding, while C. brevicuspis is found at comparatively lower elevations in the Dongting Lake wetlands.
摘要：
Bioaccumulation of heavy metals in aquatic plants is significantly affected by hydrological regime and therefore the accumulation and translocation of cadmium in five organs-panicle, leaf, stem, root, and bud-of an emergent plant (Miscanthus sacchariflorus) were compared between the submerged environment and non-submerged environment. In the submerged condition, the cadmium concentration was higher in the panicle and leaf than in the stem, root, and bud. Cadmium concentration in the root exhibited a positive regression with cadmium concentration in the sediment. However, cadmium concentration in the panicle, leaf, stem, and bud exhibited no significant regression with cadmium concentration in the sediment. In the non-submerged environment, the cadmium concentration was higher in the below-ground organs than in the aboveground organs. The mean bioaccumulation coefficient in the 24 investigated plots in the submerged environment was higher than that in the 20 and 40 mg kg(-1) cadmium treatments in the non-submerged environment. The mean translocation factor in the submerged environment was nine times higher than that in non-submerged environment. These results indicate that submergence enhanced cadmium bioaccumulation in the aboveground organs and that this plant can be used to remove heavy metals from polluted rivers and lakes.
摘要：
Abstract The growth, survival, and non-structural carbohydrate metabolism in Salix triandroides cuttings, cultivated under no flooding, incomplete submergence, or complete submergence conditions (0, 25, and 50 cm of water above the soil surface, respectively), were measured after 50, 80, 110, and 140 days. Both submergence conditions decreased the biomass of the leaf, stem, and root, plant height, root length, and root number. As the duration of the treatments increased, these growth parameters gradually increased for the control and incompletely submerged conditions, but remained relatively constant for the completely submerged condition. The survival ratio was 100% across the experimental period for plants under the control and incompletely submerged conditions; however for plants under the completely submerged condition, it was 100% after 50 and 80 days but decreased to 91.7 and 33.3% after 110 and 140 days, respectively. Compared with the plants under control and incomplete submergence conditions, the completely submerged plants had significantly lower concentrations of soluble sugars and starch. As the concentration of soluble sugars in the completely submerged plants fell to 19.2%, and that of starch to 23.5% of that in the control plants, their survival ratio decreased to 33.3%. The results indicated that the survival of the S. triandroides cuttings grown in complete submergence conditions was associated with non-structural carbohydrate metabolism.
摘要：
Coastal wetlands are ecologically important all over the world, and they are relatively unstable with dramatic changes in aboveground vegetation. However, it is still unclear how the aboveground vegetation changes will influence the functioning of coastal wetland ecosystems, especially the decomposition processes. Here, we carried out a cotton strip experiment to examine the effects of Suaeda salsa community on the soil properties and the associated cellulose decomposition rates in the coastal wetlands of Liao River delta (NE China). Our results showed that S. salsa community significantly affected the contents of soil C, N, P, base cations, organic matter and the soil electrical conductivity (EC), and such effects might vary among different types or densities of aboveground vegetation. The soil cellulose decomposition rate (in terms of cotton strip tensile strength loss, CTSL) was slowed down when aboveground S. salsa communities are experiencing degradation or have been totally replaced by Phragmites australis communities. Moreover, there were positive partial correlations between soil N and CTSL, and between soil EC and CTSL, but a negative partial correlation between soil C and CTSL. Our results emphasized the importance of S. salsa community in determining the soil cellulose decomposition rate in this coastal region. The results suggest that vegetation degradation in coastal wetlands might lead to various changes in soil properties and hence affect other aspects of ecosystem functioning and services, especially nutrient cycling.
摘要：
Wetlands play a critical role in mitigating carbon emission. However, little is known about soil carbon emission and their environmental controls from inland floodplain wetlands. This study aimed to determine the effects of hydrologic and edaphic controllers (water table depth [WTD], soil temperature [Ts], and soil water content [SWC]) on soil C emission in Dongting Lake wetland, China. One-year emissions were measured in Carex meadow and mudflat using static chambers during 2013 to 2014, including nonflooded season (NFs) and flooded season (Fs). The results showed that soil C emission in the Carex meadow and mudflat was 307.8 and 264.3 g C·m−2·year−1, respectively, and 50–66% of soil C were emitted during NFs. Compared with NFs, CO2 emission was significantly decreased by 57% but CH4 emission was significantly increased by 38 times during Fs in the Carex meadow. Stepwise regression combined with structural equation model analysis showed that CO2 and CH4 flux were mainly influenced by Ts during NFs, and they were controlled by water temperature (Tw) during Fs. During NFs, CO2 flux increased with increasing Ts and SWC but decreased significantly when SWC was over 66% and 52% in the Carex meadow and mudflat, respectively. CH4 flux showed an emission pulse at SWC and Ts of 65% and 17.2 °C, respectively. These results indicate that flooding significantly inhibited soil CO2 emission but stimulated CH4 emission. The continuous decrease of flooding days caused by anthropogenic disturbances may induce soil C loss in Dongting Lake wetlands.
关键词：
Salix triandroides;Seasonal flooding;Morphological adaptation;Photosynthetic response;Anatomical adjustment;Dongting Lake wetlands
摘要：
A simulated flooding experiment was conducted to evaluate the effects of seasonal flooding on the plant Salix triandroides from the Dongting Lake wetlands in China. The morphology, photosynthetic activity, and anatomy of cuttings in three water conditions (−40 cm, water level 40 cm below soil surface; 0 cm, water level 0 cm at the soil surface; and 40 cm, water level 40 cm above soil surface) and two lights conditions (full sunlight and 10% sunlight) were measured. Plants had a higher survival ratio and biomass accumulation in full sunlight than in 10% sunlight when the water level was −40 and 0 cm, but there was no difference between these parameters in cuttings grown under the two light conditions in the 40 cm water treatment. In full sunlight, a lower survival ratio and reduced biomass were observed with increasing water level. The same trend was also seen for survival ratio in 10% sunlight. However, there was no difference in biomass among the three water levels in 10% sunlight, except for leaf weight. Branch height, leaf number, adventitious root length, and adventitious root number were different in the three water levels and two light conditions. In water levels of −40 and 0 cm, plants had lower chlorophyll contents in full sunlight than in 10% sunlight. In full sunlight, there was no difference in chlorophyll content between the water levels, while in 10% sunlight, lower chlorophyll content was observed in −40 cm than in 0 cm water. Photosynthetic rate, stomatal conductance, and transpiration rate decreased, but water-use efficiency increased in reduced light at all three water levels. Additionally, plants had higher porosity in 40 cm water than in −40 and 0 cm conditions. Based on the reduced plant growth in the 10% sunlight condition and decreased survival in the 40 cm water level, we conclude that low light significantly decreased plant acclimation to incomplete submergence and that high water levels induced dormancy in the cuttings. Therefore, the height of cuttings used for forestation or reforestation is an important consideration for mitigating the negative effects of seasonal flooding on the survival and growth of S. triandroides in Dongting Lake wetlands.
