Future algal biofuels: implications of environmental temperature on production strain selection

Current and future economic mass production of microalgae or cyanobacteria will require suitable, preferably relatively high, levels of photosynthetically active radiation (PAR). Most large-scale productions sites, as well as those under development or under consideration, have been located between 40N and 40S raising the possible issue of the algae being periodically, or routinely, subjected to elevated temperatures (>30°C). The effects of environmental temperatures in the range 8–35°C on the marine, oleaginous model alga Nannochloropsis oculata were assessed. Active growth was observed at all temperatures except 35°C, where cells bleached and died. The implications of elevated temperature regimes were assessed for a variety of potential biofuel producing, biotechnologically relevant freshwater, marine and hyper-saline algae and the implications for their biotechnological exploitability discussed.     

Cultivation of zebra mussels (Dreissena polymorpha) within their invaded range to improve water quality in reservoirs

Algal and cyanobacterial blooms in reservoirs are driven by nutrient enrichment and may present economic and conservation challenges for water managers. Current approaches such as suppression of algal growth with barley straw, ferric dosing or manipulation of fish stocks have not yielded long term successes. A possibility that has sparked growing interest is the encouragement and cultivation of natural filter feeders, such as mussels, which remove suspended matter from the water and reduce nutrient levels through biodeposition and assimilation.This review focusses on the zebra mussel (Dreissena polymorpha) as a tool for enhancement of water quality in reservoirs. Native to the Ponto-Caspian region, this species has invaded many lakes and reservoirs across North America and Western Europe, where it occurs in very high densities. While purposeful introduction of a non-native species into new sites is socially unacceptable, we investigate the possible benefits of encouraging increased abundance of zebra mussels in sites where the species is already established.We estimate that the annual nitrogen and phosphorus input into a large UK reservoir (Grafham Water) could be assimilated into zebra mussel biomass by encouraging settlement onto 3075 m and 1400 m of commercial mussel ropes, respectively. While zebra mussel cultivation has an incredible capacity to push eutrophic systems towards a clear water state, there are many risks associated with encouraging an invasive species, even within sites where it has already established. The zebra mussel is a prominent biofouler of native unionid mussels and raw water pipes, it changes the physical characteristics of the places it inhabits, in sites low in phosphorus it can be responsible for toxic cyanobacterial blooms, it alters nutrient cycling and community structure and it can have negative impacts on amenity value. Increased propagule pressure from elevated numbers of veliger larvae in the water column may increase the risk of spread to other locations. This may render some reservoir systems, such as dammed rivers which have outflows to downstream watercourses, unsuitable for cultivation. Such reservoirs are especially common in North America.We consider the practicalities of putting a zebra mussel cultivation system into place and identify gaps in knowledge. We conclude that zebra mussel cultivation offers an attractive tool for managing nutrient-enriched reservoirs, but that the benefits and costs must be balanced on a site-by-site basis.     

DHA藻油对酸奶品质的影响

通过在搅拌型酸奶中加入DHA藻油,对制成的酸奶成品的感官、DHA含量、酸价、过氧化值等指标进行了评价、测定。结果表明,在原味酸奶中添加DHA藻油(DHA净添加量在0.25mg/g原料以内)不会对酸奶的外观、滋气味、口感产生明显影响;DHA净添加量为0.25-2.20 mg/g原料的酸奶样品,在整个生产过程及30 d的保质期内,DHA损失率最高为11.66%,在1 d至30 d的储存过程中,DHA损失率最高为5.46%。DHA净添加量在2.20 mg/g原料的酸奶样品,其酸价和过氧化值在30 d的保质期内没有发生明显变化;此外橙味香精、草莓味香精、芒果香精对添加DHA藻油的酸奶产品风味有较好地修饰作用,其中橙味香精最为明显。     

基于流域富营养化模型的水库水华主要诱发因素及防治对策

将计算流域非点源负荷的SWAT模型与一个垂向二维富营养化水体模型相集成,构成了适用于狭长河流型水库的流域富营养化模型。运用此模型,对富春江水库蓝藻水华主要诱发因素进行了计算分析,结果表明水文因素是导致2004年水库水华的最敏感因子。基于此,提出采用生态调水手段防治富春江水库水华的措施,并对2006年环境条件下,调水方案的可行性进行了计算分析,结果发现,径流量与藻类生物量间存在一个函数关系。且当水库日均径流量维持在600m\+3/s以上时,能有效的防止水库出现水华。此外,为论证模拟成果的合理性,通过设置室内藻类培养实验对不同换水周期与藻类生长状况进行对比研究,结果表明当换水周期小于3d,可以很好的抑制藻类生长,此结论与借助流域富营养化模型计算得结果相近。从而证明依据此模型所得的有关富春江水库水华的研究成果较为可靠,可供水库管理部门参考。     

流速对藻类生长影响的试验研究

水华的发生除与营养盐、光照等条件有关外,还和水体的流速等水文条件有关.以故宫筒子河为例,分析了推流技术对水体水华的抑制效果,证明增加水体流速可以在一定程度上抑制水华.在此基础上介绍了水体流速对藻类生长影响的试验研究,探讨了水体流速与藻类生长的关系.     

长荡湖、滆湖、竺山湾藻类功能群结构组成与环境因子的关系

为研究太湖流域上游长荡湖、滆湖、竺山湾三大典型浅水湖泊藻类功能群结构组成与环境因子的关系,基于2019年2月至2020年10月水文、水质及浮游植物数据,采用Q指数、香农-维纳多样性指数、TLI综合富营养化指数分析了3个湖泊的水质状况,采用非度量多维尺度变换(NMDS)分析了浮游植物群落结构组成特征,采用冗余分析探讨了浮游植物功能群与环境因子的关系。结果表明：长荡湖和滆湖水质整体属于轻度富营养化,竺山湾除冬季外,均属于中度富营养化;长荡湖、滆湖、竺山湾分别有浮游植物7门61属96种、8门75属129种和6门53属124种,分别划分为9、10和11个优势功能群;3个湖泊藻类功能群变化的共同环境因子是水温、高锰酸盐指数和总磷,而总氮和氮磷比对3个湖泊功能群结构变化的作用并不明显。     

Eutrophication model for river-type reservoir tributaries and its applications

With the impoundment of the Three Gorges Reservoir, algal blooms have been found in some tributaries. In this study, according to the theoretical analysis of the eutrophication mechanismin a river-type reservoir tributary, a one-dimensional eutrophication model was developed for the Xiangxi River tributary of the Three Gorges Reservoir, and the influence of hydrodynamic conditions on the primary growth rate of algae was investigated. Furthermore, numericalpredictions of hydraulic variables and eutrophication factors, such as the concentration distribution of TP, TN, and Chl-a in the spatial and temporal domains, were carded out. Comparison of computation results of TP, TN, and Chl-a concentrations along the river in the spring of 2005 with experimental data demonstrates the validity of the model. The agreement between the computation results and the experimental data of TP and TN concentrations is better than the agreement between those of Chl-a concentration. The simulated results also show that the Chl-a concentration downstream is much higher than that in the upstream tributary, which potentially indicates the outbreak of algae in this area. Therefore, this study provides a feasible method of accurately predicting the state of eutrophication in river-type reservoirs and their tributaries.     

49MnVS3非调质钢连铸方坯中心裂纹分析

采用金相、扫描电镜及能谱分析了连铸方坯中心位置的宏观和微观特征.发现偏析是导致中心裂纹产生的主要原因,裂纹发生在柱状晶末端和粗大等轴晶区,沿一次枝晶晶界展开;开裂方式为沿晶开裂,开裂时期处于液相.存在两种晶界偏析,一种为析出的MnS夹杂物,另一种为聚集的浓化钢液.中心位置析出物未达到非调质钢质量要求.     

异养小球藻藻渣产沼气研究

为了充分利用异养小球藻发酵及油脂生产过程中出现的藻渣,本文以p H、NH₄⁺、COD（化学需氧量）、总含碳量、VFA（挥发性脂肪酸）含量、产气量为指标,将异养小球藻发酵及油脂生产过程中产生的藻渣作为研究对象进行沼气发酵。结果表明:使用酸热法提油后藻渣为原料的发酵体系在50℃的发酵温度下,1000 m L发酵液56 d的产气量最高,为7700 m L。在发酵过程中,其pH一直下降,酸化过程良好,NH₄⁺、COD、VFA含量、总碳含量变化幅度不大,说明原料利用率相对较高、发酵过程比较稳定。本研究为异养小球藻提油工艺选择及油脂生产过程中废渣的资源化利用提供了参考。      

Cyanobacterial (Blue-Green Algal) Toxins and their Significance in UK and European Waters

The cyanobacteria (blue-green algae) which commonly produce mass developments in fresh and saline waters are capable of producing toxins. These compounds have been responsible for the deaths of animals, birds and fish in many countries, and have been linked with several forms of human illness through skin contact and ingestion. Evidence has accumulated over the past decade that cyanobacterial toxins occur commonly in European waters which contain cyanobacterial mass growths. This paper summarizes the recent published occurrence and types of cyanobacterial toxins found in European waters with reference to poisoning incidents.
Cyanobacterial blooms were particularly abundant in the warm dry summer of 1989 in the UK. The deaths of sheep and dogs and the cases of human illness that were ascribed to cyanobacterial toxins were followed by a more intensive and wider investigation into the extent of cyanobacterial toxicity in UK waters than had hitherto been undertaken. Of the cyanobacterial blooms sampled from over 90 freshwaters, approximately two-thirds were toxic (lethal) according to mouse bioassay. Short-term and long-term needs for the recognition, quantification and management of problems which can be caused by potentially toxigenic cyanobacteria in water-bodies used for recreation, aquaculture and potable supply are briefly discussed.