Pilot-scale study of removal effect on Chironomid larvae with chlorine dioxide

Chironomid larvae propagated excessively in eutrophic water body and could not be effectively inactivated by the conventional disinfection process like chlorination due to its stronger resistance to oxidation. In this paper, a pilot-scale study of chlorine dioxide preoxidation cooperating with routine clarification process for Chironomid larvae removal was conducted in Shenzhen Waterworks in Guangdong Province, China. The experimental results were compared with that of the existing prechlorination process in several aspects, including the Chironomid larvae removal efficiencies of water samples taken from the outlets of sedimentation tank, sand filter, the security of drinking water and so on. The results showed that chlorine dioxide might be more effective to inactivate Chironomid larvae than chlorine and Chironomid larvae could be thoroughly removed from water by pre-dosing chlorine dioxide process. The GC-MS examination and Ames test further showed that the sort and amount of organic substance in the treated water by chlorine dioxide preoxidation were evidently less than that ofprechlorination and the mutagenicity of drinking water treated by pre-dosing chlorine dioxide was substantially reduced compared with prechlorination.

Assessment of pesticide contaminated sediment using biological response of tropical chironomid,Chironomus javanus Kiffer as biomarker

Objective: To investigate the use of a biomarker for assessment of the effects on the tropical chironomid, Chironomus javanus(C. javanus), Kiffer of sediment contaminated with an insecticide(chlorpyrifos).Methods: A wide range of biological responses to the tropical chironomid exposed were measured, including survival, growth rate and Acetylcholinesterase(AChE) activity.Results: The measured median lethal concentration(96 h LC_(50)) of chlorpyrifos to C. javanus was 0.056(95% CI 0.024-0.124)μg/kg. For sub-chronic levels of chlorpyrifos between 0.001 and 0.25μg/kg administered for 10 days, the effects on the growth of C. javanus were reduced(larva size, head structure width and dry weight) at the significance level(P<0.01) and the effects were concentration dependent. Following exposure to chlorpyrifos at the level of 0.001μg/kg for 48 and 96 h, the AChE activity in C. javanus was inhibited compared with control samples(P<0.05).Conclusions: This study demonstrated that C. javanus was sensitive when exposed to chlorpyrifos. This species could serve as a potential biomarker for assessing pesticide contamination at low environmental persistence and provides limited effects data on the sensitivity of tropical biota to contaminants for ecological risk assessment of organophosphate pesticides in the tropical aquatic ecosystem.

Inactivation of Chironomid Larvae with Chlorine Dioxide and Chlorine

Chironomid larvae propagate prolifically in eutrophic water body and they cannot be exterminated by conventional disinfection process.The inactivation effects of chlorine and chlorine dioxide on Chironomid larvae were investigated and some boundary values in practice were determined under conditions of various oxidant dosage,organic precursor concentration and pH value.In addition,removal effect of different pre-oxidation combined with coagulation process on Chironomid larvae in raw water was evaluated.It was found that chlorine dioxide possessed better inactivation effect than chlorine.Complete inactivation of Chironomid larvae in raw water was resulted by 1.5 mg/L of chlorine dioxide with 30 min of contact time.Additionally,the organic precursor concentration,pH value had little influence on the inactivation effect.The coagulation jar test showed that Chironomid larvae in the raw water could be completely removed by chlorine dioxide pre-oxidation in combination with the coagulation process at chlorine dioxide dosage of 0.8 mg/L.

Starvation metabolism of two common species of chironomids in Biandantang Lake

Starvation metabolism is one of the important parts of respiration for normal activities of chironomids. During April 1996 to March 1997, the relationships of starvation metabolism and tempera-ture, body weight of two common chironomids in Biandantang Lake were carefully investigated. The re-sults showed relationship between starvation metabolism (R, mgO2/ind.d) and body weight (Ww, mg wet wt) was: Chironomus plumosus, lgR=-2.573+1.021lgWw (5℃), lgR=-2.710+1.354lgWw (10℃), lgR= -1.824+0.823lgWw (15℃), lgR=-1.364+0.442lgWw (20℃), lgR=-2.763+1.517lgWw (25℃); and Tokuna-gayusurika akamusi, lgR=-2.390+0.752lgWw (5 ℃ ), lgR=-1.978+0.710lgWw (10 ℃ ), lgR=-1.676+ 0.648lgWw (15℃), lgR=-1.517+0.650lgWw (20℃), lgR=-2.434+1.290lgWw (25℃). Relationship of starvation metabolism and temperature (T, ℃) was: C. plumosus, R = -0.051 + 0.021T -0.0006T2 ; T. akamusi, R= -0.051 + 0.021T -0.0006T2. The complex relationship of the three parameters was: C. plu-mosus, R=0.0098Ww0.3882e0.1068T; T. akamusi, R=0.0012Ww1.1936e0.0711T. With the above regressions, the estimated annual starvation metabolisms of the two chironomid species in Biandantang Lake were: C. plumosus, 24.2791 kJ/m2.a; T. akamusi, 8.7864 kJ/m2.a, respectively. This provides a firm foundation for the comparative study of bioenergetics of the chironomids.

Influence of Chironomid Larvae on oxygen and nitrogen fluxes across the sediment-water interface(Lake Taihu,China)

The microscale distribution of oxygen,the nitrogen flux and the denitrification rates in sediment inhabited by chironomid larvae（Tanypus chinensis） were measured in eutrophic Lake Taihu,China.The presence of the chironomids in the sediment increased the oxygen diffusional flux from 10.4 ± 1.4 to 12.7 ± 2.5 mmol O 2 /（m 2 ·day）.The burrows of the larvae represented ＂hot spots＂ and strongly influenced the nitrogen cycles and diagenetic activity in the sediment.The results indicate that the bioturbation effects of Tanypus chinensis chironomid larvae increased the capacity of the sediment as a sink for nitrate and a source for ammonium.Nitrate influx and ammonium outflux were increased 8.8 and 1.7 times,respectively.Under bioturbation,the amount of nitrate consumed was greater than the amount of ammonium released.The total denitrification rate was also enhanced from 0.76 ± 0.34 to 5.50 ± 1.30 mmol N/（m 2 ·day）.The net effect was that the bioturbated sediments acted as a net sink for inorganic nitrogen under direct and indirect bioturbation effects compared to the control.

神农架大九湖湿地摇蚊群落组成及其环境指示意义

泥炭地是一种水-陆过渡型的湿地生态系统。水体沼泽化过程中,植被等生物群落也随之改变,进而影响泥炭地碳埋藏和发育过程。作为泥炭地生态系统重要的次级生产者,摇蚊群落结构变迁可以为追溯泥炭地环境演变和发育历史提供关键线索。泥炭地在发育过程中将经历各种不同阶段,然而,现有的泥炭地摇蚊群落调查仅限于泥炭生境或泥炭地中开阔水域,较短的生境梯度不足以提供更为全面的摇蚊群落变化信息。神农架大九湖湿地包含泥炭地、湖泊、临时性水体等多种生境,本研究选择该湿地公园作为研究区域,通过采集不同生境的表层沉积物及水体样品,提取底泥亚化石摇蚊头壳,分析大九湖湿地中不同生境下的摇蚊群落结构差异,并对其与环境因子间的关系进行探讨。结果表明:1)大九湖湿地不同生境中摇蚊优势种迥异,泥炭藓藓丘生境中Limnophyes、Psilometriocnemus、Pseudosmittia等半陆生种类为主要优势种,湖泊生境中则以典型静水种Polypedilum nubeculosum-type为主要优势种,而过渡性水域(泥炭地洼地、沟渠及水洼生境)中,静水种与半陆生种共存;2)烧失量、水位埋深和p H是塑造不同生境类型下摇蚊群落结构的显著环境因子,水文条件主要通过改变碳积累过程等其他环境条件间接影响生物群落组成;3)沿水生-半陆生生境梯度,有机质含量和类型均发生显著变化,而摇蚊群落也由静水种、静水/半陆生共存转变为以半陆生种为主,摇蚊群落对生境变化表现出良好的响应过程。本研究揭示了不同生境条件下摇蚊群落的结构差异及影响摇蚊群落结构的潜在因子,为未来基于摇蚊的长时间尺度上泥炭地发育过程分析提供参考依据。

A 1000-year chironomid-based salinity reconstruction from varved sediments of Sugan Lake,Qaidam Basin,arid Northwest China,and its palaeoclimatic significance

A 1000-year high-resolution(～10 years) chironomid record from varved sediments of Sugan Lake,Qaidam Basin on the northern Tibetan Plateau,is presented.The chironomid assemblages are mainly composed of the relatively high-saline-water taxa Psectrocladius barbimanus-type and Orthocladius/Cricotopus,and the relatively low-saline-water taxa Procladius and Psectrocladius sordidellus-type.Variations in the chironomid fauna and inferred salinities suggest that over the last millennium,the Sugan Lake catchment has alternated between contrasting climatic conditions,having a dry climate during the period 990―1550 AD,a relatively humid climate during the Little Ice Age(LIA)(1550―1840 AD),and a dry climate again from 1840 AD onwards.At the decadal to centennial scale,a wet event around 1200―1230 AD,interrupting the generally arid period(990―1550 AD),and a dry event around 1590―1700 AD,punctuating the generally humid period(1550―1840 AD),are clearly documented.Trends in the chironomid-based salinity time series indicate a highly unstable climate during the LIA when salinity fluctuations were of greater magnitude and higher frequency.The effective moisture evolution in the Sugan Lake catchment during the last millennium reconstructed by chironomid analysis is in broad agreement with previous palaeo-moisture data derived from other sites in arid Northwest China(ANC).The LIA,characterized by generally humid conditions over the west-erly-dominated ANC was distinctly different from that in monsoonal China,implying an "out-of-phase" relationship between moisture evolution in these two regions during the past 1000 years.

A subfossil chironomid-total phosphorus inference model for lakes in the middle and lower reaches of the Yangtze River

The results of an investigation into the relationship between surface sediment subfossil chi- ronomid distribution and water quality are presented. Data from 30 lakes in the middle and lower reaches of the Yangtze River indicate that the nutrient gradi- ent was the major factor affecting the distribution of chironomids across these sites. Canonical corre- spondence analysis (CCA) revealed that of 12 sum- mer water environmental variables, total Phosphorus was most important, accounting for 20.1% of the variance in the chironomid data. This was significant enough to allow the development of quantitative in- ference models. A TP inference model was devel- oped using weighted averaging (WA), partial least squares (PLS) and weighted averaging partial least squares (WA-PLS). An optimal two-component WA-PLS model provided a high jack-knifed coeffi- cient of prediction for conductivity r 2jack = 0.76, with a low root mean squared error of prediction (RMSEPjack = 0.13). Using this model it is possible to produce long-term quantitative records of past water quality for lacustrine sites across the middle and lower reaches of the Yangtze River, which has important implications for future lake management and eco- logical restoration.

城市供水系统摇蚊污染发生与防治研究

近年来 ,国内已有 1 0余个省区城市供水系统中先后发生了摇蚊幼虫 (红虫 )污染事件。文章介绍了国内外供水系统摇蚊发生概况 ;分析了供水系统中摇蚊发生的 3个主要原因 :原水环境污染 ,水处理过程摇蚊污染和二次供水污染。简要回顾了国外供水系统摇蚊污染防除的历史和进展 ;重点介绍了目前国内供水行业所采用物理、化学以及生物的方法在水厂净水处理及二次供水过程防除摇蚊污染的研究 ;同时指出了当前有关研究和实践中存在的主要问题是对摇蚊生物学和生态学等知识的缺乏。

近150年来湖北太白湖摇蚊记录与湖泊营养演化

通过太白湖北部湖区沉积岩芯中摇蚊亚化石分析,结合^(210)Pb和^(137)Cs年代测定和降趋势对应分析(DCA),研究了太白湖近150年来摇蚊种属组合变化和湖泊营养演化过程。结果表明:20世纪中期(1950年左右),摇蚊种群中与大型水生植物关系密切的Paratanytarsus,Paratanytarsus penicillatus-type,Polypedilum nubeculosum-type和Dicrotendipes nervosus-type等属种迅速减少或消失,而耐营养的属种Chironomus plumosus-type,Microchironomustabarui,Procladius,Propsilocerus akamusi和Tanypus增多,表明大型水生植物减少,湖泊富营养化开始。20世纪90年代以来,Chironomus plumosus-type和Microchironomus tabarui等富营养种的比例增加反映了营养水平的进一步提高,并呈现加重趋势。摇蚊组合变化反映的太白湖营养水平的增加与流域人类活动影响密切相关,早期湖泊富营养化响应流域土壤侵蚀及湖泊水产养殖,而1990年以来湖泊富营养化的加重则与化肥的大量使用、人类活动的进一步加强及流域内工业废水污染物的开始排放有关。

摇蚊幼虫生物扰动对富营养化湖泊内源磷释放的影响

利用高分辨率的薄膜扩散梯度技术(Diffusive Gradients in Thin Films,DGT)和微电极技术,从微界面的角度研究了摇蚊扰动对沉积物中溶解氧(DO)、活性磷(Labile P)、活性铁(Labile Fe)及Labile P扩散通量的影响。研究发现摇蚊幼虫扰动增加了沉积物中溶解氧的渗透深度,降低了Labile P和Labile Fe的浓度,同时抑制了Labile P向上覆水中的释放。由于Labile P与Labile Fe显著相关(对照组R=0.672,P<0.001;摇蚊组R=0.810,P<0.001),可知Labile P的变化受DO和Labile Fe控制,即Labile Fe被氧化生成三价Fe(OOH),同时吸附Labile P,使得Labile P和Labile Fe同时降低。

几种常见氧化剂对水中摇蚊幼虫氧化杀灭效能的试验研究

进行了几种水处理氧化剂———氯气、二氧化氯、臭氧对水体中摇蚊幼虫灭活效果的试验研究,并对原水中摇蚊幼虫经二氧化氯预氧化、混凝沉淀后的灭活效果进行了考察.结果表明,二氧化氯对摇蚊幼虫的灭活效果受水体pH值、有机物含量和藻类含量影响较小,与其它2种氧化剂相比,二氧化氯对原水中摇蚊幼虫具有更好的灭活作用;混凝烧杯实验证实,原水中的摇蚊幼虫经混凝沉淀后,与矾花沉降,不会对沉后的水产生影响;并且二氧化氯投加量1.0mg·L-1时,摇蚊幼虫在24h内死亡,投加量2.0mg·L-1时,死亡时间为6h;采用预投二氧化氯的水处理工艺可以起到控制摇蚊幼虫在沉淀池中孳生的作用.

云南抚仙湖摇蚊幼虫的空间分布及其环境分析

2005年6—7月在抚仙湖共采集到摇蚊科幼虫5属6种,其中花纹前突摇蚊和羽摇蚊为优势种,两者的相对密度之和达94.9%,相对生物量之和达97.5%,其现存量基本代表了抚仙湖中摇蚊幼虫的现存量.全湖摇蚊幼虫平均密度为(275±333)ind.m-2,平均生物量为(0.642±0.763)g.m-2.花纹前突摇蚊为全湖性分布,羽摇蚊主要分布在明星鱼洞以南湖区,其他种类为局部性分布.小突摇蚊为典型的深水贫营养型种类,其分布的平均水深达107.2m.抚仙湖摇蚊幼虫密度分布与水深呈极显著正相关(P<0.001),与底质和水草的关系为沙砾石底<沙泥底<细泥底;水草区<非水草区.与1980年前后的调查资料相比,摇蚊幼虫的出现率和现存量显著增加,并出现了典型富营养型的指示种羽摇蚊,表明抚仙湖水体的营养水平在提高.

桂林会仙湿地沉积物摇蚊种群特征与环境变化

桂林会仙湿地湖泊沉积物中摇蚊种群组合特征的分析显示:2004年之前,会仙湿地经历了自贫营养水平变化到富营养水平的过程,但是湿地的富营养水平相对较低,水生态系统相对稳定,水生植物比较繁茂,水质较好,并未达到水质明显恶化的阈值。1970年是会仙湿地营养水平发生变化的重要转折点。2004年左右,会仙湿地水生态系统发生了明显的改变。

3种农药对红裸须摇蚊体内蛋白质质量分数和AChE活性的影响

为评价农药对水生生物的毒理效应,测定了氧化乐果、毒死蜱和三氟氯氰菊酯对红裸须摇蚊(Propsi-locerus akamusi)4龄幼虫的毒力、蛋白质质量分数和AChE活性的影响。结果表明,氧化乐果、毒死蜱和三氟氯氰菊酯24 h LC50分别为9.055、1.087、0.040μg.L-1,表现出高杀虫活性。这3种药剂的高质量浓度(2、4μg.L-1)处理3 h组,红裸须摇蚊体内蛋白质质量分数均低于对照,而0.125μg.L-1处理24、48 h其体内蛋白质质量分数均高于对照。红裸须摇蚊幼虫体内AChE对3种农药处理表现不同的时间—剂量效应。氧化乐果处理随着质量浓度和时间的增加,红裸须摇蚊幼虫体内的AChE活性抑制逐渐减少;而0.125μg.L-1毒死蜱对其体内AChE活性表现为诱导增加,其余处理随着时间的增加对AChE活性抑制逐渐减少;三氟氯氰菊酯处理3 h,其体内AChE活性随着处理质量浓度的增加而增大,但24、48 h处理组AChE均表现为抑制减少。因此,红裸须摇蚊AChE可作为监测有机磷和菊酯类农药污染的生物指示物。

叹气沟河优势摇蚊种群动态、周年生产量及营养基础

2006年4月—2007年3月对清江流域二级河流叹气沟河大型底栖动物群落中摇蚊优势种进行了为期1周年的调查。结果表明:主要优势摇蚊斑特突摇蚊(Thienemanimyia lentiginosa)、波特真开氏摇蚊(Eukiefferiella potthasti)和拟长跗摇蚊(Paratanytarsus parthenogeneticu)的生活史均为1年2代;拟长跗摇蚊、斑特突摇蚊的种群密度6月、9月和翌年月出现峰值,波特真开氏摇蚊则在5月和翌年1月出现峰值;采用龄期频率法(instar-frequency method)测算的周年生产量(湿质量)和生产量(P)/生物量(B)分别为斑特突摇蚊17.44g·m-2、3.4,波特真开氏摇蚊1.66g·m-2、2.3,拟长跗摇蚊3.3g·m-2、6.4;3种摇蚊的生产量在时间动态上重叠程度较大,主要发生在春季;通过对3种摇蚊的前肠内含物分析,测算了各类食物的比例及其对生产量的贡献率,结果表明,无形态碎屑为主要食物类型,占前肠内含物的73.27%～86.89%,而斑特突摇蚊生产量则主要来源于动物性食物的贡献率(51.64%)。

摇蚊幼虫对底泥中氮、磷释放作用的研究

本文研究了摇蚊幼虫对底泥中氮、磷释放的影响，初步探讨了摇蚊在湖泊富营养化过程中的生态作用。结果表明，摇蚊幼虫能明显促进底泥中氮、磷的释放，而释放到水层中的氮、磷又容易被藻类吸收利用，从而促进藻类生长。这种生态效应与水体营养循环和富营养化的发生及发展过程间存在着重要的关系。

臭氧对水中摇蚊幼虫氧化灭活效能试验

为确定臭氧对原水中摇蚊幼虫的灭活性能,进行臭氧和液氯灭活蒸馏水中第1龄期摇蚊幼虫的对比试验,在此基础上,考察人工配水和天然原水中臭氧的灭活特征,探讨原水温度和pH对臭氧灭活摇蚊幼虫的影响.结果表明:与液氯相比臭氧对蒸馏水中摇蚊幼虫具有更好的灭活作用,投加量为1.0 mg/L,接触30 min可以达到100%的灭活率;pH在5.5～7.0范围内变化对臭氧的灭活效果不会产生影响;在15～30℃范围内温度升高能够提高臭氧的灭活效果,当原水温度从30℃降低到15℃时摇蚊幼虫的灭活率下降为77.8%.

二氧化氯灭活供水系统中摇蚊幼虫的实验研究

摇蚊幼虫经常污染城市的供水系统,成为饮用水安全面临的新问题.在实验室条件下,使用二氧化氯对其进行灭活试验,得出不同浓度、pH值和接触时间下的灭活效果,并针对源水进行了灭活.对二氧化氯灭活机理及动力学进行了初步探讨.研究表明,二氧化氯在蒸馏水中投量为9 m g.L-1时,接触30 m in后可达到100%的灭活;二氧化氯灭活效果受接触时间影响较大,受pH值影响较小;摇蚊幼虫被100%灭活时,最佳CT(化学药剂浓度C与接触时间T的乘积)值为400—600 m g.m in.L-1,此时二氧化氯最低投量为5 m g.L-1.

生物杀生剂灭杀四龄红虫的试验研究

在我国许多地区的二次供水水箱和管网中均发现了摇蚊幼虫,对供水水质造成了污染。采用5种以维生素K3为主要成分的新型生物杀生剂(MPB、MTB、ME、MSB、MQ)对四龄红虫进行杀灭试验,结果表明,各杀生剂灭杀红虫的(分别为24 h和48 h)半致死浓度分别为:126.67、1.77、200、30.59、0.77 mg/L和6.11、1.04、15、5、0.64 mg/L。从时效、经济以及操作等因素考虑,MQ最经济有效,MTB次之。