Contaminated sediments and bioassay responses of three macroinvertebrates, the midge larva Chironomus riparius, the water louse Asellus aquaticus and the mayfly nymph Ephoron virgo

Bioassays are widely used to estimate ecological risks of contaminated sediments. We compared the results of three whole sediment bioassays, using the midge larva Chironomus riparius, the water louse Asellus aquaticus, and the mayfly nymph Ephoron virgo. We used sediments from sixteen locations in the Dutch Rhine-Meuse Delta that differed in level of contamination. Previously developed protocols for each bioassay were followed, which differed in sediment pretreatment, replication, and food availability. The Chironomus bioassay was conducted in situ, whereas the other two were conducted in the laboratory. The measured endpoints, survival and growth, were related to contaminant levels in the sediment and to food quantity in water and sediment.

Only the response of A. aquaticus in the bioassay was correlated with sediment contamination. Food availability in overlying water was much more important for C. riparius and E. virgo, thereby masking potential sediment contaminant effects. We conclude that growth of A. aquaticus was depressed by sediment contamination, whereas growth of E. virgo and C. riparius was stimulated by seston food quantity. We discuss that the trophic state of the ecosystem largely affects the ecological risks of contaminated sediments.     

Endocrine disruption of water and sediment extracts in a non-radioactive dot blot/RNAse protection-assay using isolated hepatocytes of rainbow trout

Goal, Scope and Background In order to evaluate the estrogenic activity of sediments and XAD water extracts of selected sites of the catchment area of the River Neckar, a river system in Southern Germany, an integrative assessment approach was used to assess the ecological hazard potential of endocrine-disrupting compounds in sediment and water. Methods The approach is based on estrogen receptor-mediated vitellogenin synthesis induced in isolated hepatocytes of rainbow trout and quantified in a non-radioactive dot blot/RNAse protection-assay in parallel to comprehensive chemical analyses of estrogenic substances. Results and Discussion Numerous investigated extracts revealed an estrogen activity comparable to that of the positive control (1 nM 17?-estradiol corresponding to 270 ng/L in the test medium). Based on a concentration factor of 30 in the extracts and a recovery of XAD resins of approximately 80 %, 17?-estradiol equivalent concentrations between 20 and 26.7 ng/L could be calculated downstream of a sewage treatment plant (< 0.1 ng/L for a reference site). A comparison of the bioassay-derived Bio-TEQs (toxicity equivalents) and the Chem-TEQs revealed a high correlation with a Pearson coefficient of 0.85, indicating that the same ranking of the samples could be obtained with respect to the endocrine disrupting potential with both chemical and bioanalytical analysis. However, the TEQ concentrations computed from chemical analyses were significantly lower than the bioassay-derived TEQ concentrations. In fact, in none of the samples, more than 14 % of the vitellogenin-inducing potency could be attributed to the substances (steroids, alkylphenols, bisphenol A, diethylstilbestrol) analyzed. A comparison of the endocrine disrupting potential of sediments extracted by the solvents acetone and methanol revealed lower biological effects for acetone-extracted samples. Possible reasons may be a masking of endocrine effects in acetone extracts by cytotoxicity, a low extraction efficiency of the solvent acetone, or anti-estrogen potencies of some extracted sediment compounds. Using a mass balance approach, the contribution of the compounds analyzed chemically (Chem-TEQs) to the total endocrine activity (Bio-TEQs) was calculated. Based on the very low detection limits, particularly of the steroids with their high TEF factors, results revealed that a calculation of the Chem-TEQs is associated with considerable scale inaccuracy: Whereas only 7-15 % of the biological effectiveness (Bio-TEQs) could be explained by endocrine substances identified above the detection limits, the assumption of concentrations slightly below the given detection limits would result in a significant over estimation (137-197 %) of the Bio-TEQs. Even the interassay variation of the dot blot assay with different fish donors for primary hepatocyte (factor 2 - 2.5) is relatively low, when compared to the large range of the Chem-TEQ concentrations (factor 20) obtained when applying different modes of calculation. Conclusions and Outlook Overall, only a minor portion of the endocrine activity detected by bioassays could be linked to compounds identified by chemical analysis. In vitro assays for assessment of endocrine activities are useful as sensitive integrating methods that provide quantitative estimates of the total activity of particular receptor-mediated responses. Although discrepancies may also result from different bioanalytical approaches, it is overall likely that bioanalytical and not chemical analytical approaches give the correct estimate of endocrine disrupting potencies in environmental samples. As a conclusion, assessment of endocrine disruption based on chemical analysis alone does not appear sufficient and further research into the spectrum of substances with potential endocrine activity as well as into additive or even synergistic effects in complex environmental samples is urgently needed.     

The SeKT joint research project: definition of reference conditions, control sediments and toxicity thresholds for limnic sediment contact tests

- In current biotest approaches, intact organisms or in vitro systems are exposed to sediments using different exposure scenarios. The most important issue in sediment toxicity testing protocols is the question which test phase (solid or liquid) should be used. Whole-sediment exposure protocols represent the most realistic scenario to simulate in situ exposure conditions in the laboratory. However, until now there is no agreement in how to acquire and to evaluate the data of the various available sediment contact assays. The SeKT joint research project was initiated with the aim to compare recently developed sediment contact assays by addressing reference conditions, control sediments and toxicity thresholds for limnic sediment contact tests.     

Dechlorination of 1,2,4-trichlorobenzene in the sediment of Ise Bay

The relation between dechlorination activities of 1,2,4-trichlorobenzene and anaerobic microbial activity were studied in the sediment collected at three sites in Ise Bay in Japan. The degradation rate of spiked 1,2,4-trichlorobenzene (3nmol ml⁻¹) ranged from 15 to 35 pmol day⁻¹ ml⁻¹ wet sediment and about 1/3 to 1/2 of degraded the trichlorobenzene was recovered as dechlorinated products. Among the dichlorobenzenes, the 1,2-isomer had the highest and 1,3-isomer had the lowest production rate. Comparing the three sampling sites, the trichlorobenzene degradation and dichlorobenzenes production rates were related to the sulfate reducing activity for the unit number of sulfate reducing bacteria. Production rates of dichlorobenzenes were completely inhibited by adding molybdate (20 mM), nitrate (60 mM), and formaldehyde solution (4 %). These results indicated that dechlorination activity in the Ise Bay sediment was supported by sulfate reduction activity in the sediment, and not supported by any other anaerobic microbial activity.     

连云港海州湾海域表层水体和沉积物中微塑料的分布特征

近年来,微塑料成为国内外广泛关注的新型海洋污染物,海湾作为人类在海岸环境中的主要活动地区,一直是海洋污染物聚集地,但我国对近岸大部分中小型海湾环境中微塑料的分布状况仍鲜见报道.为了解我国近岸中小型海湾的微塑料污染特征,本研究以江苏省海州湾海域表层海水和沉积物中采集的微塑料为样本,通过定性和定量方法研究了表层水和沉积物中微塑料主要类型和丰度及空间分布特征.结果表明,海州湾表层水体和沉积物中的微塑料丰度分别为(2.60±1.40)个·m~(-3)和(0.33±0.26)个·g~(-1),在国内近岸环境(表层水0.33～545.00个·m~(-3),沉积物0.07～2.58个·g~(-1))中,海州湾表层水中的微塑料丰度处于较低水平,但沉积物中的微塑料处于较高水平.塑料污染物的粒径大小在水体中分布范围为0.08～13.48 mm,其中,微塑料(粒径5 mm)占91.8%,塑料污染物在沉积物中粒径的分布范围为0.04～14.74 mm,微塑料占91.4%,水体和沉积物中60%以上的微塑料粒径小于2.00 mm.海州湾海域微塑料的形态以纤维状为主,占92%;颜色以蓝色和黑色为主,占70%;材质以人造纤维和PET为主,占79.4%.表层水中微塑料的分布与悬浮物浓度分布具有显著的相关性(P0.05),沉积物中微塑料的分布受多方面因素影响,其分布规律与表层水中微塑料的分布以及沉积物中粒径的分布都具有较大差异性.通过对微塑料的形态特征以及成分组成的分析表明,海州湾的微塑料主要来源于海水养殖和沿岸陆源输入.     

淡水沉积物中重金属生物有效性的研究进展

淡水重金属污染已成为全球关注的热点环境问题之一。沉积物作为重金属的重要储库与污染内源,可对水环境质量及水生态系统产生严重危害。生物有效性是评价重金属生物可利用性及其毒性效应的关键指标,研究淡水沉积物中重金属的生物有效性与调控机制,有助于阐明重金属的污染机理及其生态环境效应,可为重金属的污染防治提供科技支撑。本文回溯了沉积物重金属生物有效性的定义内涵、发展历史,重点介绍了重金属生物有效性评价的主要方法、适用性及其优缺点,归纳了影响重金属生物有效性的主要因素与内在机制,概述了目前国内外典型河流、湖泊和水库等淡水水体沉积物中相关研究的最新进展。本文进一步指出,在今后研究中亟需整合现有分析方法,形成统一的沉积物重金属生物有效性评价指标与方法体系,并开展权威实验室比对研究。同时,应考虑不同淡水生态系统的区域差异性,采用生物监测方法与原位被动采样技术相结合,将生物配位体模型纳入重金属的生态毒理效应研究中。最终,依据不同淡水环境的特性,尽快建立相应的沉积物重金属质量基准,加强重金属环境污染的科学管理。     

黄河兰州段沉积物对水体中萘的吸附行为及影响

为研究典型有机污染物在黄河兰州段沉积物的吸附规律及影响,以黄河兰州段的沉积物为供试样品,选择萘（naphthalene）为代表性有机污染物,采用批量试验法研究了污染物萘在黄河沉积物上的吸附动力学、吸附热力学、初始质量浓度、pH、离子强度、粒径等影响因素以及解吸动力学.结果表明:黄河沉积物对萘的吸附动力学更符合准二级动力学模型,且吸附过程主要分为快吸附（0~4 h）和慢吸附（4~8 h）两个阶段,在8 h左右达到平衡;Freundlich模型能较好地拟合热力学吸附特征.在25~45℃的温度范围内,E（吸附平均自由能）为0.288~0.316 kJ/mol（< 8 kJ/mol）,吸附过程中,ΔGθ（吉布斯自由能）小于0,ΔSθ（熵变）与ΔHθ（焓变）均大于0,说明萘在黄河沉积物上的吸附是一个自发的混乱度增大的吸热过程,且以物理吸附为主.影响因素分析结果显示,随着沉积物粒径的增大,萘在其上的吸附量逐渐减小;增大吸附体系中的离子强度时,萘在沉积物上的吸附过程受到抑制;当萘初始浓度增大时,吸附量增加;酸性条件抑制吸附过程,碱性环境促进吸附过程;黄河沉积物对萘的解吸量远小于吸附量,存在解吸滞后现象.研究显示,萘在黄河沉积物中的吸附速率受内部扩散、表面吸附和液膜扩散的共同影响,并且吸附过程同时受到沉积物粒径和溶液的pH和离子强度的影响.      

浑河流域底质类型对硅藻群落分布特征的影响

河流底质可以为硅藻提供附着的基质,不同的底质类型对硅藻群落结构有一定的影响.本研究对浑河流域上23个采样点位进行调查研究,并运用多响应置换过程、典范对应性分析、线性回归分析等,分析河流底质类型对硅藻群落的影响.多响应置换过程结果显示,苏子河、红河和英额河、浑河中游及浑河下游水系之间硅藻群落空间差异显著;香农多样性指数、均匀度指数与物种丰富度的平均值分别为2.57、0.69和15;典范对应性分析结果显示,IOS指数、电导率、总氮和总磷是显著影响硅藻群落结构的环境因子;相关分析结果显示,香农多样性指数、均匀度指数和物种丰富度与IOS指数呈正相关.本研究中,河流底质类型为大石块、鹅卵石等类型时,硅藻多样性较高;而底质类型为淤泥和细沙时,硅藻多样性较低.     

咖啡因在河流沉积物中吸附的影响因素及模拟研究

咖啡因是一种在环境中广泛存在的药物,其在水系环境的迁移和分布主要受到吸附行为的影响.在实验室条件下,近似模拟自然河流水/泥界面,应用中心复合实验设计,考察了温度、pH、有机质含量和转速等对咖啡因吸附的影响;利用实验所得数据,分别拟合和验证了基于线性方程和神经网络的咖啡因吸附模型,通过对比拟合和验证结果得到适用于自然河流的咖啡因吸附模型.实验结果表明,咖啡因在沉积物中的吸附呈现先快速后缓慢的过程,30 h内吸附比例超过90%;咖啡因的吸附是放热反应,低温有利于咖啡因的吸附;而转速增大能促进咖啡因的吸附反应;pH和有机质含量的影响较小.模型模拟结果表明,两种模型均能较好地拟合吸附实验结果,但神经网络模型的拟合程度和精度均优于线性方程模型;且交叉验证结果表明,利用不同组数据进行训练,神经网络模型均取得了优于线性方程的拟合结果.因此,在所考察的因素和浓度范围内,神经网络模型较好地预测了自然河流沉积物中咖啡因的吸附行为.     

改性膨润土和沉水植物联合作用处理沉积物磷

首次将改性膨润土（modified bentonite,MB）作为原位吸附材料与沉水植物苦草（Vallisneria spiralis,V.spiralis）联合处理沉积物磷.研究结果表明,MB可以促进沉水植物V.spiralis的生长, V.spiralis可能通过根系分泌作用促进溶磷或是通过促进根际微生物群落的P代谢活性增加沉积物中的生物可利用性P含量.MB与沉水植物V.spiralis对沉积物P的联合作用效果优于MB和沉水植物V.spiralis单独作用之和.厚度5cm MB和V.spiralis联合作用对沉积物TP,IP,OP,Fe/Al-P和Ca-P的去除率可达59.8%,57.1%,67.8%,66.7%和44.7%.微生物试验结果表明,厚壁菌门Erysipelotrichaceae科的菌属PSB-M-3是联合组相比单一V.spiralis组或单一MB组微生物群落P代谢功能增强的主要贡献者.本研究还首次发现了Erysipelotrichaceae科微生物可作为沉积物中潜在的除磷菌.研究结果表明MB和沉水植物联合控制沉积物磷技术可进一步应用到富营养化湖泊沉积物控制工程.