壳聚糖-沸石复合体对铜绿微囊藻的去除效果

研究壳聚糖、沸石单独絮凝除藻以及壳聚糖沸石复合体对铜绿微囊藻去除效果。结果表明：单独使用壳聚糖,质量浓度在0.6～1.1 mg/L时,对铜绿微囊藻的去除率超过90％;单独使用沸石,沸石质量浓度小于500 mg/L时,对铜绿微囊藻的去除率低于40％。经壳聚糖包覆改性后,壳聚糖沸石复合体对铜绿微囊藻絮凝去除能力大幅提高。当壳聚糖质量浓度为0.5 mg/L,沸石质量浓度为6～14 mg/L时,壳聚糖沸石复合体对铜绿微囊藻的去除率达90％以上。壳聚糖沸石复合体适用的pH值范围在5～7之间。     

再生水回用中氮磷对两种典型水华藻类生长影响研究

根据相关标准,试验选取了不同的氮磷浓度值,对蓝藻水华常见的铜绿微囊藻和绿藻水华常见的小球藻分别进行了单独培养以及两者的竞争试验.结果表明,铜绿微囊藻生长的最适氮磷浓度分别为15 mg/L、0.3～0.5 mg/L,小球藻生长的最适氮磷浓度分别为15 mg/L、0.1～0.5 mg/L;在氮磷比为15、30、50、150的试验条件下,竞争试验中的优势藻均为小球藻.建议以再生水为补水水源的景观水体中,再生水的氮磷浓度分别控制为:总氮≥15 mg/L、磷≤0.1 mg/L、氮磷比为150以上,能有效地抑制铜绿微囊藻生长.     

铜绿微囊藻的混凝特性与影响因素研究

以实验室纯培养的铜绿微囊藻为试验材料,用烧杯试验调查铜绿微囊藻的混凝特性。结果显示聚氯化铝(PAC)混凝铜绿微囊藻的效果较好。PAC对水样中铜绿微囊藻的混凝效果与藻的生长期、藻细胞胞外分泌物、温度、pH等有密切关系:铜绿微囊藻处于稳定期以及中性到弱碱性的pH范围有利于PAC混凝;温度对PAC混凝的影响与生长期有关,24-26℃对稳定期藻类的混凝沉淀最有利,对数期和衰亡期藻类需要较高的混凝温度(28-30℃);各个生长期铜绿微囊藻的胞外分泌物均有助于PAC的混凝沉降。天然水体中这些因素的耦合作用使得混凝工艺单元有效控制藻类变得困难。控制某一个或几个因素可以改善铜绿微囊藻混凝效果,其中以调节进水pH最为方便。     

Prevalence and distribution of Renibacterium salmoninarum in non-salmonid fishes from Laurentian Great Lakes and inland habitats

Renibacterium salmoninarum (RS), the causative agent of bacterial kidney disease, has been a serious threat to salmonid health in the Laurentian Great Lakes. Despite its wide spread presence in the Great Lakes basin, little is known about RS ecology and the potential role of non-salmonid species as one of the pathogen’s reservoirs. This information is of paramount importance to fishery managers in order to better understand RS distribution in the different biotic components of the Great Lakes watershed. In this study, non-salmonid species from lakes Michigan and Huron, and from 13 inland waters of the Great Lakes watershed were collected from 1999 to 2008. Out of 380 fish sampled from lakes Michigan and Huron, 42 (11.05%) tested positive for RS as determined by the nested polymerase chain reaction. Prevalence was lower in Lake Huron (5.71%) compared to Michigan (20.74%), but the difference was not statistically significant. Prevalence of RS was not found to be significantly different between species or sites; however, when species were grouped into demersal vs. pelagic categories, significant differences (P < 0.01) in prevalence were observed. Out of 607 fish sampled from inland waters, 111 (18.28%) tested positive for RS as determined by the sandwich enzyme-linked immunosorbent assay. Infection prevalence was highly variable across species and among localities. Our results indicate that many non-salmonid species can harbor this bacterium without progression to disease and may become a reservoir for infection.     

Spatial variation in RNA:DNA ratios of Diporeia spp. in the Great Lakes region

Over the past two decades, Diporeia in all of the Laurentian Great Lakes, except Superior, have declined dramatically. These declines have seemingly coincided with expansion of invasive Dreissena polymorpha and D. bugensis, however the exact mechanisms underlying decreasing Diporeia densities are obscure. We explored the use of RNA:DNA (R/D) ratios as a conditional index for Diporeia by experimentally demonstrating that Diporeia R/D responds to periods of starvation. Moreover, during 2008–2009 we collected Diporeia from throughout the Great Lakes and Cayuga Lake (New York, USA), and used R/D ratios to index condition of these in situ collected animals. We evaluated spatial and temporal variation of nucleic acid indices using classification and regression tree (CART) analysis with a suite of environmental variables included as potential predictors. Diporeia R/D of in situ collected specimens exhibited pronounced spatial and temporal variation, but multiple CART models described only a small amount of this variation. While we observed some variation in Diporeia R/D among lakes, nucleic acid ratios appeared to respond weakly to Diporeia population characteristics and local environmental conditions. Specifically, CART analyses revealed that Diporeia R/D was particularly low at extreme depths, and interestingly, Diporeia nucleic acids were not strongly associated with the presence of dreissenids. In summary, while a limited amount of variation in Diporeia R/D was attributable to environmental conditions, the majority of Diporeia R/D variation was unaccounted for. Hence, the causative factors underlying spatio-temporal variation of Diporeia R/D and the mechanistic reasons for Diporeia declines in the Great Lakes remain largely unknown.     

An integrated assessment of polycyclic aromatic hydrocarbons (PAHs) and benthic macroinvertebrate communities in Isle Royale National Park

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants that are known carcinogens and mutagens. This research used the sediment quality triad, an integrated weight-of-evidence approach, to evaluate sediment PAH concentrations, sediment toxicity, and benthic community structure at marina and reference sites in Isle Royale National Park, USA. The highest PAH concentrations were measured at marina locations and exceeded threshold effect concentrations (161 μg PAH/g TOC) at one site. Marina locations were dominated by pyrogenic PAHs, indicating anthropogenic sources of these compounds. Survival of the amphipod Hyalella azteca was significantly reduced (p = 0.0320) when exposed to sediments from marinas. Although macroinvertebrate abundance and species richness were similar at marina and reference sites, results of multivariate analyses showed that composition of benthic communities varied among sites. In particular, abundance of the PAH-sensitive amphipod, Diporeia spp. was significantly lower at marina sites compared to reference sites. In contrast to patterns observed for organochlorines (e.g., PCBS, dioxins), biota-sediment accumulation factors for PAHs measured in the burrowing mayfly Hexagenia limbata decreased with increasing K_ow values, suggesting that the more lipophilic compounds were being metabolized. Increased PAH concentrations, shifts in community composition, low survival of H. azteca, and reduced abundances of Diporeia spp. at marina sites were consistent with the hypothesis that PAHs impacted these areas; however, across all sites these effects were relatively subtle. These results emphasize the need to use a weight-of-evidence approach when investigating effects of environmental contaminants that occur at relatively low concentrations.     

Risk‐based approach for assessing the effectiveness of flow management in controlling cyanobacterial blooms in rivers

Cyanobacterial blooms present significant water quality problems worldwide. Flow management is considered to be one of the most promising approaches for combating the cyanobacterial bloom problem in rivers. In this paper, a new method for evaluating the effectiveness of flow management strategies in reducing the risk of cyanobacterial blooms is developed and applied to the River Murray at Morgan, South Australia. As stratification has been shown to be a necessary condition for significant growth of certain cyanobacteria species, the method uses estimates of the probability that stratification events of various durations will occur in conjunction with estimates of population growth during stratified conditions to determine the probability that blooms of various magnitudes will occur. The results of the case study indicate that the probability that blooms of the cyanobacterium Anabaena circinalis exceeding 15 000 cells/ml will occur in any given year under summer entitlement flow conditions is 11.7%, which is in excellent agreement with results obtained using a Poisson–Bayesian approach applied to 17 years of historical data of cell densities of Anabaena circinalis at the study site. The results obtained also indicate that increasing inflows into South Australia by 10 000 Ml/day, which is the maximum achievable increase given current operational constraints, would not have a significant impact on the occurrence of blooms exceeding 15 000 cells/ml. An additional flow of 19 900 Ml/day into South Australia would be required to reduce the probability of occurrence of blooms exceeding 15 000 cells/ml to 0.01%. Copyright © 2004 John Wiley & Sons, Ltd.     

粤东温室蝴蝶兰有害生物调查及发生规律分析

通过对温室蝴蝶兰有害生物的调查,发现危害蝴蝶兰的斜纹夜蛾、介壳虫、螨类、粉虱、蓟马、蜗牛以及病毒等是出口值得关注的有害生物,同时发现鳞长跳虫对蝴蝶兰根部的危害和太平洋细须螨的传入扩散;蝴蝶兰的细菌性褐斑病和眼蕈蚊在粤东危害较为严重,尤其要重点预防。由于温室栽培过程高温高湿,有害生物常年发生,其中虫害发生不规则,细菌性和真菌性病害多以夏季及初秋发生较为严重,而病毒应以防止感染传播为主。     

Cryptosporidium spp. and Giardia spp. removal by bank filtration at Beberibe River,Brazil

In bank filtration (BF) technology, a production well is pumped near surface water and induces water flow from the river through a porous medium to the well by percolation into the soil. Several physical, chemical, and biological processes occur, providing a natural water treatment along the river banks. An experimental area was installed on the Beberibe River with 2 production wells and 7 monitoring wells. The BF potential in removing pathogenic intestinal parasites and analysis of physical–chemical and bacteriological parameters was evaluated, according to Standard Methods. River–aquifer interaction was characterized by piezometric levels of production wells. Monitoring of the wells was correlated with the water depth of the river and precipitation. Parasite analysis was performed using Hoffman, Pons, and Janer's methods of spontaneous sedimentation, followed by centrifugation and preparation of slides stained with acetic Lugol. Protozoa oocysts were isolated by a modified Ziehl‐Neelsen method, preceded by sedimentation and centrifugation. The pathogenic protozoa found in samples from Beberibe River were Cryptosporidium spp., Giardia spp., Entamoeba histolytica/dispar complex, and Isospora belli. Pathogenic helminths were also detected: Ascaris lumbricoides, Strongyloides stercoralis, and hookworm eggs and larvae, Hymenolepis nana. In water samples from the production wells, no waterborne pathogens were found. The BF pilot project was effective in reducing levels of turbidity and color. Total coliforms and Escherichia coli were absent in the production wells. Piezometric levels of production wells and monitoring wells correlated with water depth of Beberibe River show hydraulic connection between the production wells and river, thus featuring a river–aquifer interaction. The BF pilot system showed potential for reduction or elimination of pathogenic intestinal parasites.     

Detection and variation of microcystin contents of Microcystis blooms in eutrophic Lalla Takerkoust Lake, Morocco

Hepatotoxic microcystins produced by cyanobacteria represent a significant health hazard. In Morocco, although blooms of cyanobacteria are known to occur frequently in some water‐bodies, studies on toxicology and toxinology of these potentially harmful algae have been scarcely developed. This paper presents results of the detection of Microcystin‐LR (Mcyst‐LR) and other microcystin variants and their content variations from Microcystis natural blooms and from the isolated strain culture. During the cyanobacteria dynamic study, 11 bloom samples were collected between 1994 and 2000 and were assessed for toxicity and quantification of microcystins, respectively, by mice bioassay and the enzyme‐linked immunosorbent assay. The bloom samples exhibit a high toxicity with mice intraperitoneal injection (i.p.) LD₅₀ < 100 mg/kg and the total microcystin contents were 496–8800 μg/g dry weight with a coefficient of variation of less than 11%. However, the Microcystis isolated strain cultured on Z8 medium under controlled laboratory conditions produced an amount of 707 μg/g dry weight, its toxicity level corresponds to a LD₅₀ i.p mice of 31 mg/kg. The detection of microcystin variants and the identification of Mcyst‐LR from some natural bloom samples collected in 1994, 1996 and 1999 have been carried out by high performance liquid chromatography with a photodiode array detector, which confirmed the identification from each bloom sample of at least four microcystin variants, among which the Mcyst‐LR one represents a relative proportion of 30% to 62% of total microcystin contents. Only one variant of microcystin that was not a Mcyst‐LR has been detected from a Microcystis isolated strain. The toxicity level of the material depended either on the amount of microcystins or the number of these variants and their proportion. According to these results, the survey of cyanobacteria and cyanotoxins monitoring in water used for human consumption is needed to avoid any sanitary risk.