分形理论及其在混凝研究中的应用

随着人们对分形理论研究的深入,其在混凝研究中的应用日趋广泛.分形理论的出现使人们更清楚地认识了混凝过程中出现的复杂现象及无规则形态,从而为今后对混凝过程的进一步研究提供了有力工具.该文不仅对分形理论的基本知识进行了简单地介绍,并且还对其在絮体形态学和混凝动力学方面的研究应用进行了阐述,同时列举了分形维数在混凝工艺中的具体应用实例,最后提出了目前存在的问题及自己的见解.图1,参21.     

聚合铝的形态稳定性及其动电特性的研究

本文采用改进的Ａｌ－Ｆｅｒｒｏｎ快速测定法研究了混凝过程中铝盐与聚合铝水解形态的转化规律及稳定性，并对混凝反应过程中铝与聚合铝溶解－沉淀形态分布与理论溶解度进行了对比，同时采用流动电流技术直接测定了铝盐与聚合铝絮凝剂的荷电状况，最后对发生在混凝过程中铝与聚合铝最佳凝聚形态进行了讨论。     

铝盐最佳混凝形态及最佳pH范围研究

本文从理论上分析了铝盐的水解聚合过程,预测了铝盐混凝过程进行时的最佳混凝形态及最佳ｐＨ范围,并且通过实验手段分析说明了铝盐的最佳混凝形态,混凝特征及最佳ｐＨ范围,得到了较为一致的结果。     

强化混凝去除微污染原水胶体颗粒的研究

对珠江水系统进行了强化混凝处理,燕利用准弹性激光散射技术（PCS）对常规混凝和强化混凝前后水中胶体颗粒（小于0.45um)的大小与分布进行了测定,探讨了搅拌条件对混凝效果的影响。     

高浓度PASC复合混凝剂的混凝动力学研究

以铝酸钠为碱化剂,合成了具有不同 Si/Al摩尔比的聚硅氯化铝复合混凝剂(PASC),采用透光率脉动检测技术并结合混凝效能和Zeta电位的测定结果,对PASC以及聚合氯化铝(PAC)、参比PACref在混凝过程中絮集物形成和增长的变化差异作了对比研究.结果表明,混凝过程中,Zeta电位、剩余浊度以及混凝指数密切相关.采用铝酸钠为碱化剂合成并引入硅酸钠的混凝剂,有利于提高凝聚速度和絮集物颗粒大小.在Si/Al摩尔比为0.10时处理效果达到最佳.     

铁炭-生化法处理高含盐染料废水的研究

通过对实际染料废水的处理研究，采用聚铁混凝 铁炭还原-中和混凝的预处理，可去除近50%的有机物，而且提高了废水的BOD/COD比，同时对高含盐染料废水的生化处理进行了系统研究。     

Al(Ⅲ)与Fe(Ⅲ)溶液共聚合研究

以AlCl_3·6H_2O和FeCl_3·6H_2O混合溶液通过滴加NaOH溶液的方法制备了不同Al/Fe(摩尔比,下同)和不同[OH]_b/[Al+Fe]值的共聚物.测定了聚合过程和熟化过程中的pH值变化,并对不同碱化度和熟化时间下的聚合物进行了混凝效能实验.结果表明,在共聚过程中,Fe(Ⅲ)与 OH~-的络合速度比Ai(Ⅲ)快,即 Fe(Ⅲ)具有较强的共聚合活性.Al/Fe,[OH」_b/[Al+Fe]值对铝铁共聚物形态分布有明显影响.不同条件下共聚物混凝对比实验表明,在Al/Fe为5:5,[OH]_b/[Al+Fe]为 1.6,熟化时间为24h时,显示出了较优异的混凝效能.     

工业聚合氯化铝的形态分布及混凝效果

对铝浓度为2.50mol·l-1的聚合氯化铝.采用Al-Ferron络合比色法和烧杯混凝实验对样品的形态分布和混凝性能进行了研究.结果表明:三个工业系列样品中Al的形态分布规律基本一致,Ala随盐基度的升高而逐渐降低;Alc随盐基度的升高而升高;Alb则先随盐基度的升高而升高,达到最大值后,再随盐基度的升高而降低.同一系列样品在相同加药条件下,盐基度愈高,混凝效果愈好,Alb含量愈高,混凝效果并不一定愈好.因此,提高Alb不一定能提高混凝效果,工业产品的质量控制以及追求目标应当是尽量提高盐基度,而不是Alb的含量.     

Al13去除水中腐殖酸的混凝作用机理

研究对比了Al13、不同碱化度的聚合氯化铝(PACl)及工业聚合氯化铝等去除水中腐殖酸的絮凝特征,从Zeta电位、RT(余浊)、UV254等角度分别考察了pH值和投药量的影响,对不同形态组成絮凝剂的混凝效能有了进一步明确的认识,并且对Al13的絮凝机理进行了有益的探索．结果表明,Al13是混凝过程中的优势形态,决定着混凝剂的电中和能力．     

高浓度HPAM油田污水模拟水样混凝处理方法的试验研究

本文针对聚合物采油污水的特点，通过对模拟水样的混凝试验研究，研制出一种高效的混凝药剂ＣＧＡ，并对其作用的优化条件和主要影响因素进行了研究。试验结果表明：混凝药剂ＣＧＡ在处理效果和药耗等方面均优于目前通常使用的混凝剂。     

Rapid,recurring, structured survey versus bioblitz for generating biodiversity data and analysis with a multispecies abundance model

A bioblitz inexpensively and quickly generates biodiversity data, but bioblitzes are often conducted with haphazard, unreplicated sampling. Results tend to be taxonomically, geographically, or temporally biased, lack metadata, and consist of lists of observed taxa that do not enable further analyses or correction for imperfect detection. A rapid, recurring, structured survey (RRSS) uses a structured sampling design and temporal and spatial replication to survey randomly selected sites on a conservation property. We participated in a loosely structured bioblitz and a subsequent RRSS at Big Canoe Creek Nature Preserve in Springville (St. Clair County), Alabama (USA) to compare observed richness derived from the 2 survey approaches. The RRSS data structure enabled us to fit models that accounted for imperfect detection to estimate abundances, occupancy probabilities, and habitat associations. The loosely structured bioblitz data could not be used in such models. We present a new integrated multispecies abundance model that we applied to avian RRSS data. Our model extension enables estimation for the community, employs data augmentation to estimate the number of undetected species, and incorporates covariates. The RRSS generated a more comprehensive and less biased list of observed taxonomic richness than the loosely structured bioblitz (e.g., 73 vs. 45 bird species and 104 vs. 63 insect families from the RRSS vs. loosely structured bioblitz, respectively). Models fit to the RRSS data identified seasonal patterns in avian community composition and allowed for estimation of habitat–occupancy relationships for insect taxa. The RRSS protocol has potential for broad transferability as a standardized, quick, and inexpensive way to inventory biodiversity and estimate ecological parameters while providing an outreach opportunity.     

Compliance with and ecosystem function of biodiversity offsets in North American and European freshwaters

Land-use change via human development is a major driver of biodiversity loss. To reduce these impacts, billions of dollars are spent on biodiversity offsets. However, studies evaluating offset project effectiveness that examine components such as the overall compliance and function of projects remain rare. We reviewed 577 offsetting projects in freshwater ecosystems that included the metrics project size, type of aquatic system (e.g., wetland and creek), offsetting measure (e.g., enhancement, restoration, and creation), and an assessment of the projects’ compliance and functional success. Project information was obtained from scientific and government databases and gray literature. Despite considerable investment in offsetting projects, crucial problems persisted. Although compliance and function were related to each other, a high level of compliance did not guarantee a high degree of function. However, large projects relative to area had better function than small projects. Function improved when projects targeted productivity or specific ecosystem features and when multiple complementary management targets were in place. Restorative measures were more likely to achieve targets than creating entirely new ecosystems. Altogether the relationships we found highlight specific ecological processes that may help improve offsetting outcomes.     

A palaeo-hydrogeological model for arsenic contamination in southern and south-east Asia

An argument is presented in which areas of natural arsenic contamination of modern groundwaters throughout Asia have a common origin. Arsenic originally accumulated in oceanic ferro-manganoan sediments of the eastern Palaeo-Tethys. This was further concentrated through oceanic crustal extinction in what later became the south-east Chinese accreted mineralised terrain. Proto-Himalayan uplift of this area created the palaeo-drainage systems of the Ganges – Brahmaputra, Irrawaddy, Mekong, and Red Rivers, with consequent headwater erosion of arsenic-rich sediments. Their downstream deposition as immature and easily redistributed Neogene sandstones, silts, and iron-rich clays has created secondary and tertiary reservoirs of adsorbed and authigenic arsenic, from which the current arsenic-rich groundwaters have evolved. Considering river basins within the above palaeo-hydrogeological framework provides a basis for assessing the risk of arsenic in groundwater basins of south and south-eastern Asia.     

Cost‐effective conservation of an endangered frog under uncertainty

How should managers choose among conservation options when resources are scarce and there is uncertainty regarding the effectiveness of actions? Well‐developed tools exist for prioritizing areas for one‐time and binary actions (e.g., protect vs. not protect), but methods for prioritizing incremental or ongoing actions (such as habitat creation and maintenance) remain uncommon. We devised an approach that combines metapopulation viability and cost‐effectiveness analyses to select among alternative conservation actions while accounting for uncertainty. In our study, cost‐effectiveness is the ratio between the benefit of an action and its economic cost, where benefit is the change in metapopulation viability. We applied the approach to the case of the endangered growling grass frog (Litoria raniformis), which is threatened by urban development. We extended a Bayesian model to predict metapopulation viability under 9 urbanization and management scenarios and incorporated the full probability distribution of possible outcomes for each scenario into the cost‐effectiveness analysis. This allowed us to discern between cost‐effective alternatives that were robust to uncertainty and those with a relatively high risk of failure. We found a relatively high risk of extinction following urbanization if the only action was reservation of core habitat; habitat creation actions performed better than enhancement actions; and cost‐effectiveness ranking changed depending on the consideration of uncertainty. Our results suggest that creation and maintenance of wetlands dedicated to L. raniformis is the only cost‐effective action likely to result in a sufficiently low risk of extinction. To our knowledge we are the first study to use Bayesian metapopulation viability analysis to explicitly incorporate parametric and demographic uncertainty into a cost‐effective evaluation of conservation actions. The approach offers guidance to decision makers aiming to achieve cost‐effective conservation under uncertainty.     

Parasitic wasps orient to green leaf volatiles

Summary Undamaged plants emit low levels of green leaf volatiles (GLVs), while caterpillar-damaged and artificially damaged plants emit relatively higher levels of certain GLVs. Female braconid parasitoids,Microplitis croceipes, oriented to both damaged plants and to individual GLVs in no-choice tests in a wind tunnel, but seldom oriented to undamaged plants. Female ichneumonid parasitoids,Netelia heroica, also oriented to individual GLVs in a wind tunnel. Males of both wasp species failed to orient to the GLVs. These data show that leaf-feeding caterpillars can cause the release of GLVs, and that parasitic wasps can respond to these odors by flying upwind (chemoanemotactic response), which brings the wasps to their caterpillar hosts. This supports the hypothesis that plants communicate with members of the third trophic level,i.e., plants under herbivore attack emit chemical signals that guide natural enemies of herbivores to sites of plant damage. In this interaction, the GLVs serve as tritrophic plant-to-parasitoid synomones. That parasitoids from two different wasp families oriented to GLVs suggests that the response may be widespread among the Hymenoptera.Mention of a commercial or proprietary product does not constitute an endorsement by the U.S. Department of Agriculture     

Potential for Electropositive Metal to Reduce the Interactions of Atlantic Sturgeon with Fishing Gear

Atlantic sturgeon (Acipenser oxyrhynchus) populations have been declared either endangered or threatened under the U.S. Endangered Species Act. Effective measures to repel sturgeon from fishing gear would be beneficial to both fish and fishers because they could reduce both fishery‐associated mortality and the need for seasonal and area closures of specific fisheries. Some chondrostean fishes (e.g., sturgeons and paddlefishes) can detect weak electric field gradients (possibly as low as 5 Μv/cm) due to arrays of electroreceptors (ampullae of Lorenzini) on their snout and gill covers. Weak electric fields, such as those produced by electropositive metals (typically mixtures of the lanthanide elements), could therefore potentially be used as a deterrent. To test this idea, we recorded the behavioral responses of juvenile Atlantic sturgeon (31–43 cm fork length) to electropositive metal (primarily a mixture of the lanthanide elements neodymium and praseodymium) both in the presence and absence of food stimuli. Trials were conducted in an approximately 2.5 m diameter × 0.3 m deep tank, and fish behaviors were recorded with an overhead digital video camera. Video records were subsequently digitized (x, y coordinate system), the distance between the fish and the electropositive metal calculated, and data summarized by compiling frequency distributions with 5‐cm bins. Juvenile sturgeon showed clear avoidance of electropositive metal but only when food was present. On the basis of our results, we conclude that the electropositive metals, or other sources of weak electric fields, may eventually be used to reduce the interactions of Atlantic sturgeon with fishing gear, but further investigation is needed. El Potencial del Metal Electropositivo para Reducir las Interacciones del Esturión Atlántico con Instrumentos de Pesca Bouyoucos, Bushnell & Brill 13–003     

The role of time and species identities in spatial patterns of species richness and conservation

Many conservation actions are justified on the basis of managing biodiversity. Biodiversity, in terms of species richness, is largely the product of rare species. This is problematic because the intensity of sampling needed to characterize communities and patterns of rarity or to justify the use of surrogates has biased sampling in favor of space over time. However, environmental fluctuations interacting with community dynamics lead to temporal variations in where and when species occur, potentially affecting conservation planning by generating uncertainty about results of species distribution modeling (including range determinations), selection of surrogates for biodiversity, and the proportion of biodiversity composed of rare species. To have confidence in the evidence base for conservation actions, one must consider whether temporal replication is necessary to produce broad inferences. Using approximately 20 years of macrofaunal data from tidal flats in 2 harbors, we explored variation in the identity of rare, common, restricted range, and widespread species over time and space. Over time, rare taxa were more likely to increase in abundance or occurrence than to remain rare or disappear and to exhibit temporal patterns in their occurrence. Space–time congruency in ranges (i.e., spatially widespread taxa were also temporally widespread) was observed only where samples were collected across an environmental gradient. Fifteen percent of the taxa in both harbors changed over time from having spatially restricted ranges to having widespread ranges. Our findings suggest that rare species can provide stability against environmental change, because the majority of species were not random transients, but that selection of biodiversity surrogates requires temporal validation. Rarity needs to be considered both spatially and temporally, as species that occur randomly over time are likely to play a different role in ecosystem functioning than those exhibiting temporal structure (e.g., seasonality). Moreover, temporal structure offers the opportunity to place management and conservation activities within windows of maximum opportunity.     

Main nutrient compounds in food bodies of Mexican <Emphasis Type="Italic">Acacia</Emphasis> ant-plants

Summary. Myrmecophytic plants use obligate ant mutualists as a constitutive indirect defence mechanism. These plants often produce cellular food bodies (FBs) to nourish their resident ants. Lipids, proteins, and even highly specialised compounds such as glycogen have been reported from FBs, but detailed chemical analyses of FB composition have so far been presented only for Southeast Asian Macaranga and Central American Piper myrmecophytes. Here we report the chemical composition of FBs of five myrmecophytic Acacia (Fabaceae) species from Mexico using HPLC (carbohydrates and proteins) and GC-MS (lipids). Feeding experiments revealed no hints on any use of external food sources by the inhabiting Pseudomyrmex ants. These ants obviously rely completely on FBs and extrafloral nectar provided by their hosts. The total content of nutrients in Acacia FBs was 15-25% of FB dry mass, being much lower than in Macaranga or Piper FBs. Proteins were dominating (8-14 % dm) in Acacia FBs and thus were present in higher amounts than in Macaranga FBs, yet in lower amounts than in Piper. Lipids contributed 1-9 % of dry mass, showing a lower proportion than in FBs of Macaranga or Piper. Carbohydrates made up 3-11 % dm, reaching in most Acacia species the same range as observed in Macaranga and in Piper FBs. Water content was 18-24 % of FB fresh mass, and structural tissue obviously made up a much higher proportion in Acacia FBs than in Macaranga or Piper FBs. Both characters might represent an adaptation to producing FBs unprotected at the leaf tips under dry conditions. Acacia FBs contain all amino acids and all fatty acids that are considered essential for insects, and their contents of lipids and proteins are higher than in the leaves from which they are ontogenetically derived. This indicates a putatively adaptive enrichment of nutritionally valuable compounds in structures functioning as ant-food.     

Examining the uncertain origin and management role of martens on Prince of Wales Island,Alaska

Conservation biologists are generally united in efforts to curtail the spread of non‐native species globally. However, the colonization history of a species is not always certain, and whether a species is considered non‐native or native depends on the conservation benchmark. Such ambiguities have led to inconsistent management. Within the Tongass National Forest of Alaska, the status of American marten (Martes americana) on the largest, most biologically diverse and deforested island, Prince of Wales (POW), is unclear. Ten martens were released to POW in the early 1930s, and it was generally believed to be the founding event, although this has been questioned. The uncertainty surrounding when and how martens colonized POW complicates management, especially because martens were selected as a design species for the Tongass. To explore the history of martens of POW we reviewed other plausible routes of colonization; genetically and isotopically analyzed putative marten fossils deposited in the late Pleistocene and early Holocene to verify marten occupancy of POW; and used contemporary genetic data from martens on POW and the mainland in coalescent simulations to identify the probable source of the present‐day marten population on POW. We found evidence for multiple routes of colonization by forest‐associated mammals beginning in the Holocene, which were likely used by American martens to naturally colonize POW. Although we cannot rule out human‐assisted movement of martens by Alaskan Natives or fur trappers, we suggest that martens be managed for persistence on POW. More generally, our findings illustrate the difficulty of labeling species as non‐native or native, even when genetic and paleo‐ecological data are available, and support the notion that community resilience or species invasiveness should be prioritized when making management decisions rather than more subjective and less certain conservation benchmarks.