Adsorption/desorption of arsenite and arsenate on chitosan and nanochitosan

Equilibrium sorption studies of anionic species of arsenite, As(III) ions and arsenate As(V) ions onto two biosorbents, namely, chitosan and nanochitosan, have been investigated and compared. The results and trends in the sorption behavior are novel, and we have observed during the sorption process of the As(III) and As(V) on chitosan, a slow process of desorption occurred after an initial maximum adsorption capacity was achieved, before reaching a final but lower equilibrium adsorption capacity. The same desorption trend, however, is not observed on nanochitosan. The gradual desorption of As(III) and As(V) in the equilibrium sorption on chitosan is attributed to the different fractions of the dissociated forms of arsenic on the adsorbent surface and in solution and the extent of protonation of chitosan with the changing of solution pH during sorption. The change of solution pH during the sorption of arsenite ions on chitosan was also influenced by the interaction between the buffering effect of the arsenite species in the aqueous medium and the physical properties of chitosan. The final equilibrium adsorption capacity of chitosan for As(III) and As(V) was found to be around 500 and 8000 μg/g, respectively, whereas the capacities on nanochitosan are 6100 and 13,000 μg/g, respectively.

     

亭子口库区水质汞的污染特征及建库后水体中汞的预测

亭子口水利枢纽位于喜陵江平流苍溪县城以上，１５ｋｍ处。本文根据嘉陵江广元段水质监测资料，分析库区地面水体中汞的现状污染特征，并运用沉积物的负指数方程预测库区建坝后水体中汞的浓度。     

Estimation bias under model selection for distance sampling detection functions

Many simulation studies have examined the properties of distance sampling estimators of wildlife population size. When assumptions hold, if distances are generated from a detection model and fitted using the same model, they are known to perform well. However, in practice, the true model is unknown. Therefore, standard practice includes model selection, typically using model comparison tools like Akaike Information Criterion. Here we examine the performance of standard distance sampling estimators under model selection. We compare line and point transect estimators with distances simulated from two detection functions, hazard-rate and exponential power series (EPS), over a range of sample sizes. To mimic the real-world context where the true model may not be part of the candidate set, EPS models were not included as candidates, except for the half-normal parameterization. We found median bias depended on sample size (being asymptotically unbiased) and on the form of the true detection function: negative bias (up to 15% for line transects and 30% for point transects) when the shoulder of maximum detectability was narrow, and positive bias (up to 10% for line transects and 15% for point transects) when it was wide. Generating unbiased simulations requires careful choice of detection function or very large datasets. Practitioners should collect data that result in detection functions with a shoulder similar to a half-normal and use the monotonicity constraint. Narrow-shouldered detection functions can be avoided through good field procedures and those with wide shoulder are unlikely to occur, due to heterogeneity in detectability.     

The Importance of Analysis Method for Breeding Bird Survey Population Trend Estimates

Population trends from the Breeding Bird Survey are widely used to focus conservation efforts on species thought to be in decline and to test preliminary hypotheses regarding the causes of these declines. A number of statistical methods have been used to estimate population trends, but there is no consensus as to which is the most reliable. We quantified differences in trend estimates or different analysis methods applied to the same subset of Breeding Bird Survey data. We estimated trends for 115 species in British Columbia using three analysis methods: U.S. National Biological Service route regression, Canadian Wildlife Service route regression, and nonparametric rank-trends analysis. Overall, the number of species estimated to be declining was similar among the three methods, but the number of statistically significant declines was not similar (15, 8, and 29 respectively). In addition, many differences existed among methods in the trend estimates assigned to individual species. Comparing the two route regression methods, Canadian Wildlife Service estimates had a greater absolute magnitude on average than those of the U.S. National Biological Service method. U.S. National Biological Service estimates were on average more positive than the Canadian Wildlife Service estimates when the respective agency's data selection criteria were applied separately. These results imply that our ability to detect population declines and to prioritize species of conservation concern depend strongly upon the analysis method used. This highlights the need for further research to determine how best to accurately estimate trends from the data. We suggest a method for evaluating the performance of the analysis methods by using simulated Breeding Bird Survey data.     

Adapting to climate change: an integrated biophysical and economic assessment for Mozambique

Mozambique, like many African countries, is already highly susceptible to climate variability and extreme weather events. Climate change threatens to heighten this vulnerability. In order to evaluate potential impacts and adaptation options for Mozambique, we develop an integrated modeling framework that translates atmospheric changes from general circulation model projections into biophysical outcomes via detailed hydrologic, crop, hydropower and infrastructure models. These sector models simulate a historical baseline and four extreme climate change scenarios. Sector results are then passed down to a dynamic computable general equilibrium model, which is used to estimate economy-wide impacts on national welfare, as well as the total cost of damages caused by climate change. Potential damages without changes in policy are significant; our discounted estimates range from US$ 2.3 to US $7.4 billion during 2003?C2050. Our analysis identifies improved road design and agricultural sector investments as key ??no-regret?? adaptation measures, alongside intensified efforts to develop a more flexible and resilient society. Our findings also support the need for cooperative river basin management and the regional coordination of adaptation strategies.     

Conservation Applications of Astronaut Photographs of Earth: Tidal-Flat Loss ( Japan), Elephant Effects on Vegetation (Botswana), and Seagrass and Mangrove Monitoring (Australia)

Abstract: National Aeronautics and Space Administration ( NASA) photographs taken by astronauts from low Earth orbit can provide information relevant to conservation biology. This data source is now more accessible because of improvements in digitizing technology, Internet file transfer, and availability of image processing software. We present three examples of conservation-related projects that benefited from the use of astronaut photographs. First, NASA scientists requested that astronauts photograph the area of the controversial Isahaya Bay reclamation project in Japan. Japanese researchers used photographs from before and after the reclamation as a tool for communication with the public about the effects of tidal-flat loss. The newly acquired images and the availability of high-resolution digital images from NASA archives provided timely public information on the observed changes. Second, we digitally classified and analyzed a Space Shuttle photograph of Chobe National Park in Botswana to identify the locations of woodlands affected by elephants. Field validation later confirmed that areas identified on the image showed evidence of elephant damage. Third, we used a summary map from intensive field surveys of seagrasses in Shoalwater Bay, Australia, as reference data for a supervised classification of a digitized photograph taken from orbit. The classification distinguished seagrasses, sediments, and mangroves with accuracy approximating that in studies using other satellite remote-sensing data. Astronaut photographs are in the public domain, and the database of nearly 400,000 photographs from the late 1960s to the present is available at a single searchable location on the Internet (  http://eol.jsc.nasa.gov/sseop ). These photographs can be used by conservation biologists as a source of general information about the landscape and for quantitative mapping.     

原子吸收法测定重金属的预处理方法讨论

介绍了原子吸收法测定煤灰、煤渣、塑料薄膜、植物、粮食作物、蔬菜、水果、鱼类、矿石和矿渣等各种类型样品中重金属不同的分解方法.