水生植物对水体水质的净化作用分析

随着中国工业化进程的推进,近年来,水生植物对水体水质的净化作用的研究需求越来越急切。水生植物对水体水质起主要净化作用,本文主要通过对水生植物的概念,水生植物对水体水质净化作用的应用,以及水生植物对水体水质的净化原理三个方面的阐述,从而对水生植物对水体水质的净化作用进行分析。     

利用水生植物原位修复污染水体

在实验围隔系统中,夏季利用凤眼莲、冬季利用耐寒型沉水植物伊乐藻等恢复水生生态系统,研究水生植物对水体氮、磷营养盐、透明度等理化性质的影响.结果表明：水生植物处理围区营养盐水平均显著低于围区对照和大湖水体.最初15 d,凤眼莲生长速度快,覆盖面积从100 m²增加到470 m²;44 d后,覆盖面积达到65％,处理围区的水质最佳,总氮(TN)、铵态氮(NH₄⁺ -N)、亚硝态氮(NO₂^- -N)、高锰酸钾盐指数(COD_Mn)和叶绿素a浓度最低,透明度达到1.7～1.8 m(水底).10月份后,处理围区水体总磷(TP)维持在0.1 mg·L^-1左右.处理围区透明度提高后,伊乐藻逐渐成为优势种(覆盖面积达到总水域的1/3),在净化水质、维持水质理化性质稳定和提高透明度方面作用显著.表明水生植被恢复可以有效降低水体营养盐,控制浮游植物增长,是改善富营养湖泊水质的重要措施.     

三种水生植物对苯的净化作用及条件优化

为了探讨水生植物对含苯污染水体的修复效果,采用L₂₇(3¹³)正交设计法,研究了3种水生植物普生轮藻（Chara vulgaris L.）、豆瓣菜（Nasturtium officinale R.Br.）和菹草（Potamogeton crispus L.）对水体中苯的净化作用。结果表明,在实验条件下,3种植物对苯的最大去除率分别达到35.26%、69.71%和55.45%。温度、作用时间、生物量及温度与时间、温度与生物量的交互作用对普生轮藻去除苯的作用影响显著。温度和生物量对豆瓣菜去除苯的作用影响显著。作用时间对菹草去除苯的作用影响显著。3种植物均可作为良好的水质净化材料。普生轮藻和豆瓣菜适合在夏秋季选用,而菹草则适合冬春季选用。     

红枫湖富营养化水体生态修复中水生植物化学成分

高原山区深水型湖泊水深大、水位变化剧烈,不利于水生植物生长,通常的浅水湖泊生态修复技术难以应用.本文选取贵州红枫湖这一典型的高原深水湖泊作为试验点,在右二湖湾以浮岛为载体引种多种水生植物,并对植物根茎叶中的氮、磷及重金属成分进行了分析.结果表明:各水生植物氮含量为菹草＞鲁梅克斯＞聚合草,磷含量为菹草＞伊乐藻＞鲁梅克斯,氮、磷元素去除效果较好的植物为菹草、伊乐藻、鲁梅克斯;试验植物对重金属Cu、Cd、Pb、Zn和Hg均具有一定的耐受性,植物内不同重金属的累积浓度为Zn＞Pb＞Cu＞＞Cd＞Hg,重金属富集系数根＞叶＞茎,Zn/Cd比值为叶＞茎＞根;总体上,黑麦草、鲁梅克斯和菹草重金属的富集系数较高;植物中总氮(TN)与总磷(TP)含量呈显著正相关,重金属与营养元素之间不存在明显的相关性.试验表明,陆生植物依靠浮岛载体能在水面较好地生长,可应用于深水型湖泊污染水体生态修复.在实际应用时,需结合水体污染特点和植物吸收特性选择最佳植物组合类型.     

利用植物多级净化广州污染河涌水体及景观修复设想

对广州市水系污染状况及其综合治污的重要性和必要性进行了分析,对以往靠比较单一的污水处理厂处理污水效果较差的原因从多个角度进行了探究.对于采取建立利用植物多级处理、净化水污染物的立体处理系统的原理、必要性及可行性进行了分析;针对广州市土地紧张,在水厂内难以建立大型植物氧化塘的特点,提出了在各个河涌建立各级以高等植物为主的植物净化系统等措施,对主要技术措施进行了论述,并对其所能达到的改善水生态系统、实现良好的景观效益和生态效益方面进行了深入的探讨.     

淡水水生植物化感作用研究进展

水生植物的化感作用对淡水生态系统中水草的可持续管理和湖泊富营养化的生态控制具有非常重要的意义。本文综述了淡水水生植物化感作用的发展历史和研究现状,讨论了水生植物化感作用研究过程中所涉及的实验方法、生物测试方法、化感物质分离方法以及影响水生植物化感研究的环境因素。抑藻圈试验、藻类生长试验和浮萍生长试验是常用的生物测试方法;采用共生培养或单独培养的方法,从种植水中分离、鉴定化感物质,对证实复杂水环境中水生植物化感作用的存在,研究它们化感物质的释放途径和作用机理都具有十分重要的作用。     

水生植物修复铁污染水体的效果及作用机制

为解决铁离子污染导致水体发黄问题,采用水培试验,分析了水禾、粉绿狐尾藻、圆币草、黄花水龙、大薸和圆叶节节菜等6种水生植物对铁离子污染水体的修复能力,研究了铁离子浓度、pH和植物生物量对水禾修复效果的影响,并探讨了曝气对水禾除铁的强化作用。结果表明: 6种水生植物均不同程度地促进了水中二价铁和全铁的去除,不同植物对铁的去除效果差异显著;试验24 h,水禾和圆币草处理二价铁浓度分别由5.0 mg·L^-1降至0.23和0.26 mg·L^-1,满足《地表水环境质量标准》(GB 3838—2002)限值要求(二价铁浓度≤0.3 mg·L^-1),全铁浓度降至0.84和1.21 mg·L^-1,去除率达83.2%和75.8%。pH在5、6、7、8时,各pH处理组二价铁和全铁浓度无显著差异,二价铁和全铁去除率分别为95.4%～98.4%和92.2%～94.6%。二价铁初始浓度≤5.0 mg·L^-1时,二价铁和全铁去除率随二价铁浓度增加而增大;高浓度二价铁(10.0 mg·L^-1)对水禾生长有一定的抑制作用,试验期间全铁去除不稳定,试验结束时全铁去除率较对照仅提高7.0%,远低于其他浓度处理。生物量≥300 g时,处理24 h,二价铁浓度从5.0 mg·L^-1降至0.3 mg·L^-1以下,且各生物量处理去除效果差异不显著。间歇曝气和连续曝气均强化水禾对铁的去除,连续曝气更利于稳定去除全铁。     

利用水生植物清除水体中放射性物质的研究：（Ⅲ）水生植物对Sr^90、Y^91、Cs^137、Ce^144的积累、释放及Ca对Sr^90吸收的影响

5种水生植物对所用4种放射性同位素都有一定的清除能力，其清除能力的大小不仅取决于生物的种类，而且还取决于生物本身代谢率的高低。试验结果：去污率高的可达80％，积累系数最高可达1，500；水体中含Ca量的多少对生物吸收积累放射性物质的多少有一定的影响；生物在积累放射性物质之后，转移到无放射性物质的水体中将释放出原积累的一部分放射性物质。     

4种水生植物对富营养化水体氮磷去除效果的研究

以灯心草、水田芥、菹草和轮藻为试验对象,研究了其在两种不同程度富营养化水体中的生长状况及对水体中总氮(TN)、总磷(TP)、氨氮(NH4+-N)和化学耗氧量(COD)的净化效果。结果表明,在轻度富营养化水体中水田芥效果最好,培养20 d后的水田芥对总氮、总磷、氨氮和化学耗氧量的吸收率分别为75.28%、93.00%、76.35%和83.74%,其它3种水生植物对水体也都有较好的净化效果;在重度富营养化水体中灯心草效果最好,培养20天后的灯心草对总氮、总磷、氨氮和化学耗氧量的吸收率分别为89.30%、83.11%、83.41%和78.56%,但水田芥和轮藻的净化效果相对较差。     

乡土水生植物对富营养化水体的净化效果研究

为了解乡土水生植物净化富营养化水体的效果,研究了广东地区5种乡土水生植物对2种富营养化水体总氮(TN)、总磷(TP)的净化效果和植物的生长状况。结果表明,与无植物空白相比,5种乡土植物使低、高浓度水体的TN去除率分别提高了3.8%～13.3%和13.2%～17.1%,TP去除率分别提高了15.2%～22.1%和11.3%～57.6%,其中野荸荠(Eleocharis plantagineiformis)适用于净化低氮水体;酸模叶蓼(Polygonumlapathifolium)适用于高氮水体;三白草(Saururuschinensis)适用于低磷水体;菱角(Trapa komarovii)适用于低氮或高磷水体;水龙(Ludwigia adscendens)对2种水体均有较好的净化效果,对高磷水体效果极佳。5种乡土植物在低、高浓度水体中均旺盛生长,水龙的生物量净增长率分别达375.5%和539.8%,表现最优,其次为菱角;水葫芦(Eichhorniacrassipes)则在高浓度水体中腐烂死亡,加重了水体污染。水龙、菱角对污染物的吸收作用较强,对P的吸收能力显著优于其他植物(P0.05)。因此,5种乡土植物均可作为广东地区富营养化水体修复的备选植物,其中水龙和菱角的开发潜力最大。     

水生植物在瘦西湖公园中的应用

介绍了瘦西湖公园的概况和目前水生植物在公园中的应用情况,指出了目前园林中应用水生植物时存在的不足,提出了令后的改进措施和努力方向。     

Comparative Characterization of the Pigment Complex in Emergent, Floating, and Submerged Leaves of Hydrophytes

The content of chlorophylls (Chls) and carotenoids was studied in the leaves of 42 species of boreal aquatic plants with different degree of submergence (emergent, floating, and submerged) and isopalisade, dorsoventral, and homogenous types of mesophyll structure. Hydrophytes were shown to have a low Chl content (1–2 mg/g fr wt) and low Chls/carotenoids ratio (2.3–3.5) as compared to terrestrial plants. The pigment content per dry wt unit and unit leaf area was dependent on the type of mesophyll structure. It was a consequence of the changes in the parameters of leaf mesophyll structure characterizing the density of photosynthetic elements. In a sequence emergent floating submerged forms, the content of Chls and carotenoids decreased, and the photosynthetic capacity decreased due to a reduction in the chloroplast number per unit leaf area. Adaptation of submerged leaves to low illumination and slow CO₂ diffusion changed the functional properties of chloroplasts. An increase in the pigment content in the chloroplasts of submerged leaves (7 × 10^–9 mg Chl, 2 × 10^–9 mg carotenoids) as compared to emergent and floating leaves was accompanied by a decline in the photosynthetic capacity per Chl comprising 1.6 mg CO₂/(mg Chl h) versus 3.9 and 3.8 mg CO₂/(mg Chl h) in emergent and floating leaves, respectively.     

Occurrence of Arbuscular Mycorrhizas and Dark Septate Endophytes in Hydrophytes from Lakes and Streams in Southwest China

In this study, the colonization of arbuscular mycorrhizas (AM) and dark septate endophytes (DSE) in 140 specimens of 32 hydrophytes collected from four lakes and four streams in southwest China were investigated. The arbuscular mycorrhizal fungi (AMF) and DSE colonization in these hydrophytes were rare. Typical AM structures were observed in one of the 25 hydrophytic species collected in lakes and six of the 17 species collected in streams. Spores of 10 identified AMF species and an unidentified Acaulospora sp. were isolated from the sediments. The identified AMF came from the four genera, Acaulospora, Gigaspora, Glomus and Scutellospora . Glomus and G. mosseae were the dominant genus and species respectively in these aquatic environments. The presence of DSE in hydrophytes was recorded for the first time. DSE occurred in one of the 25 hydrophyte species collected in lakes and three of the 17 species collected in streams. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

菲污染土壤的微生物修复机制

菲(Phenanthrene)是存在于煤焦油中,含三个苯环的稠环芳烃。除了具有"三致"作用外,菲稳定的化学结构和高辛醇-水分配系数等特性,使其具备较强的抗降解能力,易在环境中富集,破坏土壤微生态结构,降低农作物品质,威胁人类健康。而且随着化石燃料的长期大量使用,受菲污染的土地面积也急速增加,给人类的健康及生产活动带来极大的威胁。因此,有效清除土壤中菲及其他多环芳烃污染物,净化环境,具有重要的现实意义。微生物降解作为治理菲污染的方法之一,具有高效、低成本、环境友好的特点,受到研究者的高度重视。本文从菲降解菌的种类、降解机理、分子机制、影响修复等因素及微生物与植物联合修复五个方面进行综述,为进一步利用环境微生物,开发高效菲降解菌,治理菲污染提供参考。     

Structure of the Photosynthetic Apparatus in Leaves of Freshwater Hydrophytes: 1. General Characteristics of the Leaf Mesophyll and a Comparison with Terrestrial Plants

The structure of photosynthetic elements was investigated in leaves of 42 boreal plant species featuring different degrees of submergence (helophytes, neustophytes, and hydatophytes). The mesophyll structure types were identified for all these species. Chlorenchyma tissues and phototrophic cells were quantitatively described by such characteristics as the sizes of cells and chloroplasts in the mesophyll and epidermis, the abundance of cells and chloroplasts in these tissues, the total surface area of cells and chloroplasts per unit leaf area, the number of plastids per cell, etc. The hydrophytes typically had thick leaves (200–350 m) with a well-developed aerenchyma; their specific density per unit area (100–200 mg/dm²) was lower than in terrestrial plants. Mesophyll cells in aquatic plants occupied a larger volume (5–20 × 10³m³) than epidermal cells (1–15 × 10³m³). The number of mesophyll cells per unit leaf area was nearly 1.5 times higher than that of epidermal cells. Chloroplasts were present in the epidermis of almost all species, including emergent leaves, but the ratio of the chloroplast total number to the number of all plastids varied depending on the degree of leaf submergence. The total number of plastids per unit leaf area (2–6 × 10⁶/cm²) and the surface of chloroplasts per unit leaf area (2–6 cm²/cm²) were lower in hydrophytes than in terrestrial plants from climatically similar habitats. The functional relations between mesophyll parameters were similar for hydrophytes and terrestrial plants (a positive correlation between the leaf weight per unit area, leaf thickness, and the number of mesophyll cells per unit leaf area), although no correlation was found in hydrophytes between the volume of mesophyll cells and the leaf thickness. Phototrophic tissues in aquatic plants contributed a larger fraction to the leaf weight than in terrestrial plants, because the mechanical tissues were less developed in hydrophytes. The CO₂assimilation rates by leaves were lower in hydrophytes than in terrestrial plants, because the total surface area of chloroplasts per unit leaf area is comparatively small in hydrophytes, which reduces the conductivity for carbon dioxide diffusion towards the carboxylation sites.     

First Description of Various Bacteria Resistant to Heavy Metals and Antibiotics Isolated from Polluted Sites in Tunisia

Environmental bacteria belonging to various families were isolated from polluted water collected from ten different sites in Tunisia. Sites were chosen near industrial and urban areas known for their high degree of pollution. The aim of this study was to investigate cross-resistance between heavy metals (HM), i.e., silver, mercury and copper (Ag, Hg, and Cu), and antibiotics. In an initial screening, 80 isolates were selected on ampicillin, and 39 isolates, retained for further analysis, could grow on a Tris-buffered mineral medium with gluconate as carbon source. Isolates were identified based on their 16S rRNA gene sequence. Results showed the prevalence of antibiotic resistance genes, especially all isolates harbored the bla_TEM gene. Some of them (15.38%) harbored bla_SHV. Moreover, several were even ESBLs and MBLs-producers, which can threaten the human health. On the other hand, 92.30%, 56.41%, and 51.28% of the isolates harbored the heavy metals resistance genes silE, cusA, and merA, respectively. These genes confer resistance to silver, copper, and mercury. A cross-resistance between antibiotics and heavy metals was detected in 97.43% of our isolates.     

Structure of the Photosynthetic Apparatus in Leaves of Freshwater Hydrophytes: 2. Quantitative Characterization of Leaf Mesophyll and the Functional Activity of Leaves with Different Degrees of Submersion

The structure of leaf photosynthetic elements was investigated on 42 boreal plant species characterized by different degrees of submergence (helophytes, neustophytes, and hydatophytes). Six main types of mesophyll structures were identified. Quantitative characteristics for the mesostructure of the photosynthetic apparatus in these groups were determined, such as the size and abundance of cells and chloroplasts in the mesophyll and epidermis, the number of plastids per cell in each tissue, the total surface area of the mesophyll cells, epidermal cells, and chloroplasts per unit leaf area. Analysis showed that quantitative characteristics of the photosynthetic apparatus in hydrophytes are determined by two factors: (a) the degree of leaf submergence and (b) the type of mesophyll structure. With an increasing degree of immersion in water, the mesophyll types change in a sequence isopalisade dorsoventral homogeneous. The leaves become thinner, their weight per unit area diminishes, cells and chloroplasts become less numerous (on a per unit leaf area basis), but their dimensions become larger. Adaptation to aquatic medium is also manifested in the increasing contribution of the epidermal tissue to the overall photosynthesis: in submerged leaves, the epidermis accounts for more than 50% of the photosynthetic activity. The occurrence of six structural types of leaves contrasting in their characteristics was confirmed by discriminatory analysis according to the qualitative parameters of mesophyll.     

In vitro Toxic Effects of Certain Antibiotics on the Fibroblasts of Two Children with I-Cell Disease

Six antibiotics, pefloxacin (Peflacine), fosfomycin (Fosfocine), teicoplanin (Targocid), vancomycin (Vancocine), ceftazidime (Fortum), piperacillin (Piperilline), that may be used as a systematic coverage during bone marrow transplantation have been tested on dermal fibroblasts of one control subject and two I-cell disease patients, along with five subcultures, corresponding to 5 weeks of culture. The possible toxicity of these molecules was assessed. The evaluation of lysosomal enzyme sphingomyelinase activity, detection of free intracellular cholesterol and the light- and electron-microscopic examination of treated cells were used as measures of metabolic interference and cytotoxicity. Our study shows that despite a lack of any metabolic sign of interference (no modification in enzyme activity, no increase in free intracellular cholesterol), all the antibiotics tested induced a cytotoxic effect which was notably amplified in the I-cell populations. This may be due to the lysosomal lipid storage of these cells which modifies the relationship between the antibiotic and the cell by inducing a different kind of lipid–antibiotic interference.     

Enhanced Soil Washing for the Remediation of a Brownfield Polluted by Pyrite Ash

Soil from an abandoned/disused fertilizer plant polluted with pyrite ash containing heavy metal(loid)s (As, Cu, Pb, and Zn) was treated by means of physical and chemical washing. We first performed an exhaustive characterization of the soil-pollutant interaction, which allowed us to determine the chemical nature (complex oxyhydroxides), potential mobility and bioavailability of the pollutants (very low), as well as the grain size fractions of preferential accumulation (silt-clay fraction comprises more than 60% of the material and revealed contents well above 2.000 ppm of Cu, Zn and Pb). Soil/ash samples were subjected to a number of chemical washing trials, including leaching with 2 M HCl, 2 M NaOH and acidic process water (pH around 0). The fraction below 63 µm was mechanically separated and exposed to additional leaching tests e.g. chloridizing roasting with NaCl plus water leaching. Of all the tested procedures, the latter proved the most effective, particularly with regard to Cu and Zn recovery (recoveries up to 40% and 34%, respectively). The information gathered offers an insight into the modes and rates at which metals can be leached from pyrite ashes after chloridizing roasting as a prelude to more extensive soil washing feasibility studies focused on potential metal recovery.