Effects of pH,initial Pb2+ concentration,and polyculture on lead remediation by three duckweed species

Various geographical duckweed isolates have been developed for phytoremediation of lead. The Pb²⁺ removal efficiency of Lemna aequinoctialis, Landoltia punctata, and Spirodela polyrhiza was investigated in monoculture and polyculture at different levels of pH and initial Pb²⁺ concentrations. L. aequinoctialis was not sensitive to the tested pH but significantly affected by initial Pb²⁺ concentration, whereas synergistic effect of pH and initial Pb²⁺ concentration on removal efficiency of L. punctata and S. polyrhiza was found. Although the majority of polycultures showed median removal efficiency as compared to respective monocultures, some of the polycultures achieved higher Pb²⁺ removal efficiencies and can promote population to remove Pb²⁺. Besides, the three duckweed strains could be potential candidates for Pb²⁺ remediation as compared to previous reports. Conclusively, this study provides useful references for future large-scale duckweed phytoremediation.

     

海南省福报农场旅游资源的开发与规划

海南省福报农场沙河旅游区以河谷山岳型自然风光为主体格架,构成了多姿多态的景观类型。景点集中而丰富,且以其幽、秀、奇、秘、特形成与海南区域整体旅游资源结构的迥异特色,具有较高的美学价值和良好的区位条件。在开发中以“福报芒果”为拳头产品,树立本区的旅游产品形象;以经济开发为导向,采取游览、购物、经贸、度假相协调的综合开发模式,从而获得经济、环境和社会的平衡发展     

河北省大气污染状况分析及对策研究

不利的地理气象条件,产业、能源结构不合理,汽车尾气超标排放,城市扬尘严重,法规不健全及群众环保意识薄弱导致了河北省连续出现大范围、重污染、持续时间长的雾霾天气。为此,河北省采取了削减煤炭消费、产业结构转型升级、控制机动车污染、加强区域联防联控等治理措施。目前河北省治污仍面临着结构调整、经济方式转变历时长,资金和环境科技支撑能力不足,人员安置难等困难,建议通过实施京津冀生态文明建设一体化规划,借鉴欧美发达国家的先进经验,争取更多资源和资金支持来进一步提升治理效果。     

Using Fly Ash as a Marker to Quantify Culturally‐Accelerated Sediment Accumulation in Playa Wetlands

Wetlands in the Rainwater Basin in Nebraska are vulnerable to sediment accumulation from the surrounding watershed. Sediment accumulation has a negative impact on wetland quality by decreasing the depth and volume of water stored, and the plant community species composition and density growing in the wetland. The objective of this study was to determine the amount of sediment that has accumulated in five selected wetlands in the Rainwater Basin in Nebraska. Soil cores were taken at five or six locations along transects across each wetland. This study used the fly ash, which is generated by coal‐burning locomotives that were present generally in the late 1800s and early 1900s, as a marker to quantify the sediment deposition rates. The cores were divided into 5 cm sections and the soils were analyzed using a fly ash extraction and identification technique. Results indicate that the average depth of sediment ranged from 23.00 to 38.00 cm. The annual average depth of sediment accumulation ranged from 0.18 cm/yr to 0.29 cm/yr. The annual sediment accumulation rate from both wind erosion and water erosion in these five sampling wetlands was between 1.946 and 3.225 kg/m²/yr. The results of this research can be used to develop restoration plans for wetlands. The fly ash testing technology can also be applied to other areas with the railroads across the United States.     

二甲基二烯丙基氯化铵－丙烯酰胺的合成及其在含油污水处理中的应用

以二甲胺、氯丙烯等为原料合成二甲基二烯丙基氯化铵（ＤＭＤＡＡＣ），再与丙烯酰胺（ＡＭ）共聚生成共聚物。利用胶体滴定法测定共聚物的阳离子度、一点法测定特性粘数，并利用充气浮选法对阳离子共聚物进行浮选效果评价。结果表明，当产品的阳离子度在３０％～４０％的范围内除油效果最好，其效果明显优于阳离子聚丙烯酰胺（ＣＰＡＭ），与复配的聚合铝加聚丙烯酰胺（ＰＡＣ＋ＰＡＭ）相当。     

ECONOMIC APPRAISAL OF A GROUND WATER DEVELOPMENT PROJECT1

A ground water development project in the northern part of Thailand was appraised by means of benefit-cost analysis. This is the first project in Thailand to develop ground water for irrigation purposes and it is also the first project which made use of an underground PVC pipe water distribution system. Results indicate that the project is economically feasible. In comparing different water distribution systems, it is also found that distribution by means of underground PVC pipes is more economical compared to an open ditch system if the life of the latter is relatively short and the rates of inflation are high.     

AUTOMATED WEB GIS BASED HYDROGRAPH ANALYSIS TOOL,WHAT1

The separation of the base flow component from a varying streamflow hydrograph is called “hydrograph analysis.” In this study, two digital filter based separation modules, the BFLOW and Eckhardt filters, were incorporated into the Web based Hydrograph Analysis Tool (WHAT) system. A statistical component was also developed to provide fundamental information for flow frequency analysis and time series analysis. The Web Geographic Information System (GIS) version of the WHAT system accesses and uses U.S. Geological Survey (USGS) daily streamflow data from the USGS web server. The results from the Eckhardt filter method were compared with the results from the BFLOW filter method that was previously validated, since measured base flow data were not available for this study. Following validation, the two digital filter methods in the WHAT system were run for 50 Indiana gaging stations. The Nash‐Sutcliffe coefficient values comparing the results of the two digital filter methods were over 0.91 for all 50 gaging stations, suggesting the filtered base flow using the Eckhardt filter method will typically match measured base flow. Manual separation of base flow from streamflow can lead to inconsistency in the results, while the WHAT system provides consistent results in less than a minute. Although base flow separation algorithms in the WHAT system cannot consider reservoir release and snowmelt that can affect stream hydrographs, the Web based WHAT system provides an efficient tool for hydrologic model calibration and validation. The base flow information from the WHAT system can also play an important role for sustainable ground water and surface water exploitation, including irrigation and industrial uses, and estimation of pollutant loading from both base flow and direct runoff. Thus, best management practices can be appropriately applied to reduce and intercept pollutant leaching if base flow contributes significant amounts of pollutants to the stream. This Web GIS based system also demonstrates how remote, distributed resources can be shared through the Internet using Web programming.     

Incorporating differences between genetic diversity of trees and herbaceous plants in conservation strategies

Reviews that summarize the genetic diversity of plant species in relation to their life history and ecological traits show that forest trees have more genetic diversity at population and species levels than annuals or herbaceous perennials. In addition, among-population genetic differentiation is significantly lower in trees than in most herbaceous perennials and annuals. Possible reasons for these differences between trees and herbaceous perennials and annuals have not been discussed critically. Several traits, such as high rates of outcrossing, long-distance pollen and seed dispersal, large effective population sizes (N_e), arborescent stature, low population density, longevity, overlapping generations, and occurrence in late successional communities, may make trees less sensitive to genetic bottlenecks and more resistant to habitat fragmentation or climate change. We recommend that guidelines for genetic conservation strategies be designed differently for tree species versus other types of plant species. Because most tree species fit an LH scenario (low [L] genetic differentiation and high [H] genetic diversity), tree seeds could be sourced from a few populations distributed across the species’ range. For the in situ conservation of trees, translocation is a viable option to increase N_e. In contrast, rare herbaceous understory species are frequently HL (high differentiation and low diversity) species. Under the HL scenario, seeds should be taken from many populations with high genetic diversity. In situ conservation efforts for herbaceous plants should focus on protecting habitats because the typically small populations of these species are vulnerable to the loss of genetic diversity. The robust allozyme genetic diversity databases could be used to develop conservation strategies for species lacking genetic information. As a case study of reforestation with several tree species in denuded areas on the Korean Peninsula, we recommend the selection of local genotypes as suitable sources to prevent adverse effects and to insure the successful restoration in the long term.     

Water regime-nitrogen fertilizer incorporation interaction: Field study on methane and nitrous oxide emissions from a rice agroecosystem in Harbin, China

Water regime and nitrogen (N) fertilizer are two important factors impacting greenhouse gases (GHG) emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we conducted a two-year field experiment to study the impacts of water regime and N fertilizer on rice yields and GHG emissions in Harbin, China, a cold region located in high latitudes. Our results showed that intermittent irrigation significantly decreased methane (CH₄) emission compared with continuous flooding, however, the decrement was far lower than the global average level. The N₂O emissions were very small when flooded but peaked at the beginning of the disappearance of floodwater. The N fertilizer treatments increased CH₄ emissions at low level (75kgN/ha). But both CH₄ and N₂O emissions were uninfluenced at the levels of 150kgN/ha and 225kgN/ha. Rice yields increased under intermittent irrigation and were highest at the level of 150kgN/ha. From our results, we recommended that the intermittent irrigation and 150kgN/ha as the ideal water regime-nitrogen fertilizer incorporation for this area to achieve low GHG emissions without impacting rice yields.