人工湿地挺水植物脱氮效果研究

为了比较不同季节人工湿地挺水植物的脱氮效果,以菖蒲(Acorus calamus)、香蒲(Typha angustifolia)和芦苇(Phragmites australis)3种挺水植物为材料构建潜流型人工湿地,在春夏、夏秋两季间歇式均匀布水条件下,通过测定污水中pH及溶解氧(DO)、氨氮、硝态氮、总氮浓度,分析不同季节挺水植物的脱氮效果。结果表明:出水DO浓度在春夏季表现为对照(CK)湿地菖蒲湿地香蒲湿地芦苇湿地,在夏秋季表现为CK湿地菖蒲湿地芦苇湿地香蒲湿地;人工湿地出水pH均呈弱碱性,种有挺水植物的人工湿地在春夏季和夏秋季的pH分别为7.33~8.09、6.81~7.59;在春夏季,芦苇湿地的总氮去除率最高;在夏秋季,香蒲湿地的总氮去除率最高。     

阶段曝气和植物对人工湿地处理城镇污水厂尾水的影响

采用人工配水模拟城镇污水处理厂尾水水质,利用3套阶段曝气垂直潜流人工湿地(VSFCW)对其进行处理。结果表明:当水力负荷分别为30、90和180 cm·d-1时,3套人工湿地对COD具有较好的去除效果,其去除率都大于66.7%;在处理总磷(TP)和总氮(TN)方面,VSFCW-1(无植物-曝气垂直潜流人工湿地)去除效果远远低于VSFCW-2(芦苇-曝气垂直潜流人工湿地)和VSFCW-3(芦苇-不曝气垂直潜流人工湿地),VSFCW-2(芦苇-曝气垂直潜流人工湿地)和VSFCW-3(芦苇-不曝气垂直潜流人工湿地)对TP和TN的去除率分别在80.0%和75.0%以上且具有较强的抗水力负荷冲击能力。VSFCW-2(芦苇-曝气垂直潜流人工湿地)和VSFCW-3(芦苇-不曝气垂直潜流人工湿地)对COD、TP的去除主要是集中在沿程的前1/4段(0~24 cm),后3/4段(24~115 cm)保证了出水水质的稳定。     

植物碳源调控对人工湿地脱氮效果的影响

针对人工湿地中有机碳源不足造成的脱氮效率不高的问题,向人工湿地中投加植物碳源用以改善人工湿地内部碳氮比低的状况。通过比较芦苇秸秆、梧桐树皮、梧桐树叶、玉米芯4种植物碳源分解时有机物、氮元素的释放规律,从而确定玉米芯为最佳植物碳源,并采用水平潜流人工湿地系统模型研究了投加玉米芯对人工湿地系统脱氮效果的影响。试验发现,空白湿地系统COD的平均去除率为38.71%,总氮的平均去除率为34.24%,玉米芯湿地系统则在保证COD平均去除率38.52%的同时,提高总氮平均去除率到70.55%,证明了植物碳源调控提高人工湿地脱氮效果的可行性与高效性。     

表流-水平流复合人工湿地对高污染河水的净化

为了研究表流-水平流复合人工湿地对高污染河水的净化效果及植物对复合湿地中二级潜流湿地的影响作用,实验构建了表流+芦苇水平潜流和表流+无植物水平潜流复合人工湿地。在相同的水力负荷下连续运行一年的结果表明,复合人工湿地对高污染河水中TN、NH3-N、TP、COD、BOD5和SS的去除率分别为57.3%~63.1%、65.7%~68.1%、69.4%~82.7%、85.3%~86.3%、96.7%~96.9%和97.9%~98.2%,种有植物的二级潜流湿地具有更好的脱氮和除磷效果;表流湿地作为复合湿地的第一级能够有效去除大部分的有机污染物和悬浮物,进而避免二级潜流湿地的堵塞,并利于二级潜流湿地的脱氮除磷的进行;复合湿地对有机物和悬浮物的去除不受季节性波动的影响,但是其脱氮效果受季节波动的影响较大。     

自由表面人工湿地脱氮效果中试研究

对自由表面人工湿地去除农业面源污水中氮的效果及途径进行了研究 ,结果表明 ,脱氮效率随水力停留时间(HRT)延长而增加 ,HRT为 0 5、1、2和 3d时 ,系统总氮去除率分别为 18 3 %、3 8 9%、84 9%和 85 6%。HRT <2d ,出水水质波动较大 ,2d以上 ,系统即可高效稳定运行。硝化 /反硝化是湿地脱氮的主要途径 ,挥发和填料吸附脱氮量可以忽略 ,依靠植物吸收可以去除一部分氮 ,茭草 (Zizaniacaduciflora)和芦苇 (Phragmitascommunis)的氮吸收量每年分别为 44 0和70 0kgN/hm2 。     

组合人工湿地工艺微生物群落结构及脱氮效果研究

将复合垂直流、表面流、潜流3种不同类型的人工湿地串联起来,研究每种人工湿地的脱氮微生物及其脱氮效果.结果表明,各种人工湿地池填料表面微生物数量丰富,组合人工湿地系统形成两个串联的A/O单元,脱氮效果良好,其中总氮去除率达82.61%.     

自由表面人工湿地脱氮效果中试研究

对自由表面人工湿地去除农业面源污水中氮的效果及途径进行了研究，结果表明，脱氮效率随水力停留时间（HRT）延长而增加，HRT为0.5、1、2和3d时，系统总氮去除率分别为18.3%、38.9%、84.9%和85.6%。HRT＜2d，出水水质波动较大，2d以上，系统即可高效稳定运行。硝化／反硝化是温地脱氮的主要途径，挥发和填料吸附脱氮量可以忽略，依靠植物吸收可以去除一部分氮，茭草（Zizania caduciflora）和芦苇（Phragmitas communis）的氮吸附量每年分别为440和700kg N/hm^2。     

陈垃圾反应床＋芦苇人工湿地处理垃圾渗滤液

研究了陈垃圾反应床与芦苇人工湿地串联对垃圾渗滤液中污染物的去除效果, 并探讨了湿地中芦苇生长和对渗滤液中总氮的吸收能力。结果表明： 在进水负荷为0.1 m³/（m²·d）的条件下,经过3个月的运行,陈垃圾反应床与芦苇人工湿地对陈年渗滤液中COD、氨氮、总氮及总磷的最大去除率分别达到90.3%、95.0%、79.3%和99.8%。通过对人工湿地中芦苇的分析表明,芦苇在6—8月份生长迅速,地上部分生物量与其氮含量增加较快,最大值均出现在8月底,植株总含氮量可以达到28.5 g/m²。此时收割芦苇可从湿地中最大限度除氮。如能增加芦苇种植密度,陈垃圾床与芦苇湿地串联处理渗滤液污染物以及深度去氮是可行的。     

COD/N对潜流人工湿地脱氮效能及N_2O排放的影响

人工湿地因其低能耗、易管理的优点被广泛应用于水处理和生态修复,尤其在发展中国家有其适用性。为探讨COD/N对潜流人工湿地脱氮效能及氧化亚氮(N2O)的排放影响,分别构建5组微型人工湿地CW1~CK,进水化学需氧量/总氮(COD/N)分别为20∶1、10∶1、7∶1、4∶1和0∶1。结果表明,湿地出水DO浓度均低于0.5 mg·L~(-1),不同的COD/N下无显著差异,但pH表现为随COD/N的升高而降低。进水COD/N为10、7和4的湿地中COD去除率在80%以上,而进水COD/N=20的湿地中COD去除率不足70%。5组COD/N湿地中氨氮(NH+4-N)的平均去除率依次为(61±16.6)%、(23±14.1)%、(30±12.5)%、(28±14.5)%和(74±7.0)%,在碳源充足或无碳源的条件下有利于NH+4-N的去除。除COD/N=0外,其余湿地中出水未检测到硝态氮(NO_3~--N)。湿地中总氮(TN)的去除变化与NH+4-N相似。5组湿地系统中,N2O的平均释放通量和累积排放量,分别在0.83~11.84 mg·(m2·h)~(-1)和30.65~490.80 mg·m~(-2)之间。COD/N=4的人工湿地系统中,N2O的平均释放通量和累计排放量显著高于其他处理(p0.05),且在其中以N2O形态去除的氮占系统去除TN的百分比为4.87%。COD/N对潜流人工湿地的脱氮和N2O减量具有调控作用。     

模拟垂直潜流人工湿地中植物种类和植物多样性对脱氮效果的影响

在模拟垂直潜流人工湿地中选种了水烛和菩提子两种常见湿地植物,以氨氮为湿地唯一氮源,通过植物单种和混种研究了植物种类和植物多样性对湿地脱氮效果的影响。结果表明,菩提子单种时,出水氮浓度均明显低于水烛单种。菩提子单种时,出水硝态氮、氨氮、总无机氮(TIN)质量浓度分别为72.34、13.80、86.14mg/L;水烛单种时,出水硝态氮、氨氮、TIN质量浓度分别为235.41、32.12、267.53mg/L。水烛与菩提子混种时,出水比菩提子或水烛单种具有更低的硝态氮和TIN,硝态氮和TIN质量浓度分别为55.60、80.50mg/L。因此,相比水烛,菩提子更有利于湿地脱氮;加强植物多样性可提高湿地的脱氮效果。湿地的脱氮效果与植物生物量具有显著相关性。     

Chloroaromatic pollutants in mussels incubated in two finnish watercourses polluted by industry

Concentrations of different chlorinated compounds were measured in mussels incubated in two polluted watercourses, a river (the River Kymijoki) and a lake (Lake Vanaja) for four weeks in summer 1995. The sum concentrations of polychlorinated phenols (PCP) and biphenyls (PCB) were both about 1 μg/g lipid weight (lw) in Lake Vanaja mussels, while in the River Kymijoki mussels PCPs were non-detectable and PCBs were measured 120 ng/g lIw. The concentrations of toxic polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners ranged between <17 and 370 pg/g Iw in Lake Vanaja mussels and between <38 and 11,000 pg/g lw in the River Kymijoki mussels. Polychlorinated diphenyl ethers (PCDE) were detected in the mussels incubated in the River Kymijoki (0.4–1.1 ng/g Iw), but not in those incubated in Lake Vanaja. Polychlorinated phenoxyanisoles (PCPA) were measured 33 ng/g lw and polychlorinated phenoxyphenols (PCPP) 300 ng/g lw in the mussels incubated in the River Kymijoki. PCPAs were also detected in reference samples, which were sediment and pike from the River Kymijoki and Baltic salmon, seal and white-tailed sea eagle.     

Book review

The Pesticide Manual ‐ A World Compendium, 8th Edition, C.R. Worthing, Editor and S.B. Walker, Assistant Editor, British Crop Protection Council, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, England. 1987, 1100 pp., UK £50; Overseas £56. ISBN 0–948404–01–9.     

Organochlorine compounds in a three-step terrestrial food chain

The concentrations of 15 organochlorine chemicals (PCBs and pesticides) were studied in a Central European oak wood food chain system: Great tit (Parus major), caterpillars (Tortrix viridana, Operophtera brumata, Erannis defoliaria), and oak-leaves (Quercus robur). Juvenile tits receive organochlorines from the mother via egg transfer and, eventually to a greater extent, from the caterpillar food source during nestling period. The concentrations of PCB 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl, the most abundant in this study) was found in leaf material at ca. 1 ng/g, in caterpillars 10 ng/g, and in bird eggs 170 ng/g on an average and on a dry mass basis.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.     

Observations on the influence of water and soil pH on the persistence of insecticides

Abstract

The pH‐disappearance rate profiles were determined at ca. 25°C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water‐ethanol (99: 1 v/v). Half‐lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (>1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1–2 days for trichlorfon and oxamyl to >1 year for fensulfothion and cyper‐methrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.     

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.     

Radionuclides in pinon pine (Pinus edulis) nuts from los alamos national laboratory lands and the dose from consumption

Abstract

One of the dominant tree species growing within and around the eastern portion of Los Alamos National Laboratory (LANL), Los Alamos, NM, lands is the pinon pine (Pinus edulis). Pinon pine is used for firewood, fence posts, and building materials and is a source of nuts for food—the seeds are consumed by a wide variety of animals and are also gathered by people in the area and eaten raw or roasted. This study investigated the (1) concentration of ³H, ¹³⁷Cs, ⁹⁰Sr, ^totU, ²³⁸Pu, ^{239, 240}Pu, and²⁴¹ Am in soils (0‐ to 12‐in. [31 cm] depth underneath the tree), pinon pine shoots (PPS), and pinon pine nuts (PPN) collected from LANL lands and regional background (BG) locations, (2) committed effective dose equivalent (CEDE) from the ingestion of nuts, and (3) soil to PPS to PPN concentration ratios (CRs). Most radionuclides, with the exception of ³H in soils, were not significantly higher (p < 0.10) in soils, PPS, and PPN collected from LANL as compared to BG locations, and concentrations of most radionuclides in PPN from LANL have decreased over time. The maximum net CEDE (the CEDE plus two sigma minus BG) at the most conservative ingestion rate (10 lb [4.5 kg]) was 0.0018 mrem (0.018 μSv); this is far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem (1000 μSv). Soil‐to‐nut CRs for most radionuclides were within the range of default values in the literature for common fruits and vegetables.     

Degradation and sorption of imidacloprid in dissimilar surface and subsurface soils

Degradation and sorption/desorption are important processes affecting the leaching of pesticides through soil. This research characterized the degradation and sorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine) in Drummer (silty clay loam) and Exeter (sandy loam) surface soils and their corresponding subsurface soils using sequential extraction methods over 400 days. By the end of the incubation, approximately 55% of imidacloprid applied at a rate of 1.0 mg kg^?1 degraded in the Exeter sandy loam surface and subsurface soils, compared to 40% of applied imidacloprid within 300 days in Drummer surface and subsurface soils. At the 0.1 mg kg^?1 application rate, dissipation was slower for all four soils. Water-extractable imidacloprid in Exeter surface soil decreased from 98% of applied at day 1 to > 70% of the imidacloprid remaining after 400 d, as compared to 55% in the Drummer surface soil at day 1 and 12% at day 400. These data suggest that imidacloprid was bioavailable to degrading soil microorganisms and sorption/desorption was not the limiting factor for biodegradation. In subsurface soils > 40% of ¹⁴C-benzoic acid was mineralized over 21 days, demonstrating an active microbial community. In contrast, cumulative ¹⁴CO₂ was less than 1.5% of applied ¹⁴C-imidacloprid in all soils over 400 d. Qualitative differences in the microbial communities appear to limit the degradation of imidacloprid in the subsurface soils.     

Biochemical interaction of six op delayed neurotoxicants with several neurotargets

Abstract

Five organophosphorous insecticides: Leptophos, EPN, Cyano‐fenphos, trichloronate and salithion proved to cause irreversible ataxia not only to chicken but also to mice and sheep. TOCP was included as a reference. Cyanofenphos blocked the catecholamine B‐receptor binding activity with ³H‐norepinephrine at a level similar to that of the specific inhibitor propranolol in the mouse heart preparation. In the lamb heart preparation, the B‐receptor was more sensitive to Leptophos, salithion and TOCP than to propranolol. The six compounds and their oxons were screened for their in‐vitro inhibition to monamine oxidase (MAO), acetyl cholinesterase (AChE) and neurotoxic esterase (NTE) in the brain of either mouse, lamb or chicken. It is believed that their AChE inhibition stands for their acute toxicity, while NTE inhibition is responsible for their paralytic ataxia.     

Phytoextraction of lead-contaminated soil using vetivergrass (<Emphasis Type="Italic">Vetiveria zizanioides</Emphasis> L.), cogongrass (<Emphasis Type="Italic">Imperata cylindrica</Emphasis> L.) and carabaograss (<Emphasis Type="Italic">Paspalum conjugatum</Emphasis> L.)

Background, Aims and Scope The global problem concerning contamination of the environment as a consequence of human activities is increasing. Most of the environmental contaminants are chemical by-products and heavy metals such as lead (Pb). Lead released into the environment makes its way into the air, soil and water. Lead contributes to a variety of health effects such as decline in mental, cognitive and physical health of the individual. An alternative way of reducing Pb concentration from the soil is through phytoremediation. Phytoremediation is an alternative method that uses plants to clean up a contaminated area. The objectives of this study were: (1) to determine the survival rate and vegetative characteristics of three grass species such as vetivergrass, cogongrass and carabaograss grown in soils with different Pb levels; and (2) to determine and compare the ability of the three grass species as potential phytoremediators in terms of Pb accumulation by plants. Methods The three test plants: vetivergrass (Vetiveria zizanioides L.); cogongrass (Imperata cylindrica L.); and carabaograss (Paspalum conjugatum L.) were grown in individual plastic bags containing soils with 75 mg kg⁻¹ (37.5 kg ha⁻¹) and 150 mg kg⁻¹ (75 kg ha⁻¹) of Pb, respectively. The Pb contents of the test plants and the soil were analyzed before and after experimental treatments using an atomic absorption spectrophotometer. This study was laid out following a 3 × 2 factorial experiment in a completely randomized design. Results On the vegetative characteristics of the test plants, vetivergrass registered the highest whole plant dry matter weight (33.85–39.39 Mg ha⁻¹). Carabaograss had the lowest herbage mass production of 4.12 Mg ha⁻¹ and 5.72 Mg ha⁻¹ from soils added with 75 and 150 mg Pb kg⁻¹, respectively. Vetivergrass also had the highest percent plant survival which meant it best tolerated the Pb contamination in soils. Vetivergrass registered the highest rate of Pb absorption (10.16 ± 2.81 mg kg⁻¹). This was followed by cogongrass (2.34 ± 0.52 mg kg⁻¹) and carabaograss with a mean Pb level of 0.49 ± 0.56 mg kg⁻¹. Levels of Pb among the three grasses (shoots + roots) did not vary significantly with the amount of Pb added (75 and 150 mg kg⁻¹) to the soil. Discussion Vetivergrass yielded the highest biomass; it also has the greatest amount of Pb absorbed (roots + shoots). This can be attributed to the highly extensive root system of vetivergrass with the presence of an enormous amount of root hairs. Extensive root system denotes more contact to nutrients in soils, therefore more likelihood of nutrient absorption and Pb uptake. The efficiency of plants as phytoremediators could be correlated with the plants’ total biomass. This implies that the higher the biomass, the greater the Pb uptake. Plants characteristically exhibit remarkable capacity to absorb what they need and exclude what they do not need. Some plants utilize exclusion mechanisms, where there is a reduced uptake by the roots or a restricted transport of the metals from root to shoots. Combination of high metal accumulation and high biomass production results in the most metal removal from the soil. Conclusions The present study indicated that vetivergrass possessed many beneficial characteristics to uptake Pb from contaminated soil. It was the most tolerant and could grow in soil contaminated with high Pb concentration. Cogongrass and carabaograss are also potential phytoremediators since they can absorb small amount of Pb in soils, although cogongrass is more tolerant to Pb-contaminated soil compared with carabaograss. The important implication of our findings is that vetivergrass can be used for phytoextraction on sites contaminated with high levels of heavy metals; particularly Pb. Recommendations and Perspectives High levels of Pb in localized areas are still a concern especially in urban areas with high levels of traffic, near Pb smelters, battery plants, or industrial facilities that burn fuel ending up in water and soils. The grasses used in the study, and particularly vetivergrass, can be used to phytoremediate urban soil with various contaminations by planting these grasses in lawns and public parks. ESS-Submission Editor: Dr. Willie Peijnenburg (wjgm.peijnenburg@rivm.nl)