Quantitative and qualitative characteristics of dissolved organic matter from eight dominant aquatic macrophytes in Lake Dianchi, China

The aim of this research was to determine and compare the quantitative and qualitative characteristics of dissolved organic matters (DOM) from eight aquatic macrophytes in a eutrophic lake. C, H, N, and P in ground dry leaves and C, N, and P in DOM of the species were determined, and C/N, C/P, C/H, DOC/C, TDN/N, TDP/P, DOC/TDN, and DOC/TDP were calculated. Chemical structures of the DOM were characterized by the use of multiple techniques including UV-visible, FT-IR, and ¹³C CP/MAS spectra. The results showed subtle differences in quantity and quality of DOM among species and life-forms. Except oriental pepper which had a C/H of 0.7, C/H of all the other species was 0.6. C/N and C/P of ground leaves was 10.5–17.3 and 79.4–225.3, respectively, which were greater in floating and submerged species than in the others. Parrot feather also had a small C/P (102.8). DOC/C, TDN/N, and TDP/P were 7.6–16.8, 5.5–22.6, and 22.9–45.6 %, respectively. Except C/N in emergent and riparian species, C/N in the other species and C/P in all the species were lower in their DOM than in the ground leaves. DOM of the macrophytes had a SUVA₂₅₄ value of 0.83–1.80. The FT-IR and ¹³C NMR spectra indicated that the DOM mainly contained polysaccharides and/or amino acids/proteins. Percent of carbohydrates in the DOM was 37.3–66.5 % and was highest in parrot feather (66.5 %) and crofton weed (61.5 %). DOM of water hyacinth, water lettuce, and sago pondweed may have the greatest content of proteins. Aromaticity of the DOM was from 6.9 % in water lettuce to 17.8 % in oriental pepper. DOM of the macrophytes was also different in polarity and percent of Ar–OH. Distinguished characteristics in quantity and quality of the macrophyte-derived DOM may induce unique environmental consequences in the lake systems.     

Application of 15N–18O double stable isotope tracer technique in an agricultural nonpoint polluted river of the Yangtze Delta Region

One strategy to combat nitrate (NO₃-N) contamination in rivers is to understand its sources. NO₃-N sources in the East Tiaoxi River of the Yangtze Delta Region were investigated by applying a ¹⁵N–¹⁸O dual isotope approach. Water samples were collected from the main channel and from the tributaries. Results show that high total N and NO₃-N are present in both the main channel and the major tributaries, and NO₃-N was one of the most important N forms in water. Analysis of isotopic compositions (δ ¹⁸O, δD) of water suggests that the river water mainly originated from three tributaries during the sampling period. There was a wide range of δ ¹⁵N-NO₃ (?1.4 to 12.4 ‰) and a narrow range of δ ¹⁸O-NO₃ (3.7 to 9.0 ‰) in the main channel waters. The δ ¹⁵N and δ ¹⁸O-NO₃ values in the upper, middle, and lower channels along the river were shifted as 8.2, 3.5, and 9.5 ‰, and 9.0, 4.2, and 6.0 ‰, respectively. In the tributary South Tiao, the δ ¹⁵N and δ ¹⁸O-NO₃ values were as high as 9.5 and 7.0 ‰, while in the tributaries Mid Tiao and North Tiao, NO₃-N in most of the samples had relatively low δ ¹⁵N and δ ¹⁸O-NO₃ values from 2.3 to 7.5 ‰ and 4.7 to 7.0 ‰, separately. Our results also suggest that the dual isotope approach can help us develop the best management practice for relieving NO₃-N pollution in the rivers at the tributary scale.     

Occurrence, possible sources, and temporal trends of polychlorinated dibenzo-p-dioxins and dibenzofurans in water and sediment from the lower Yangtze River basin, Jiangsu and Shanghai areas of Eastern China

The concentrations, compositional profiles, and possible sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) in water column and surface sediment samples from the lower reaches of the Yangtze River were investigated, and the potential risks posed by these chemicals were evaluated. Concentrations of the 17 2,3,7,8-substituted PCDD/PCDF in the water and sediment samples ranged from 0.45 to 10.0 pg TEQ/L (mean 2.34 pg TEQ/L) and from 0.31 to 51 pg TEQ/g dw (mean 5.25 pg TEQ/g dw), respectively. Water and sediments from the Nanjing–Nantong sections of the Yangtze River were found to have elevated PCDD/PCDF levels, and the PCDD/PCDF TEQ concentrations in 13 sediment samples exceeded the probable effect levels (PEL), above which adverse biological effects are likely. Multivariate statistical analysis indicated that the principal PCDD/PCDF contamination source for the water and sediment was the production and use of pentachlorophenol (PCP) or sodium pentachlorophenate (PCP-Na). PCDD/PCDF concentrations were stable over time near the Yangtze River Estuary but had increased sharply in recent decades in the Nanjing–Nantong section, which will have been related to the growth in industrial activities and other anthropogenic PCDD/PCDF sources. Total organic carbon (TOC) and PCDD/PCDF concentrations correlated significantly (R?=?0.474, P?<?0.01), suggesting that TOC plays an important role in the transport and re-distribution of PCDD/PCDF in the Yangtze River basin.     

Fate of caffeine in mesocosms wetland planted with Scirpus validus

Uptake, accumulation and translocation of caffeine by Scirpus validus grown in hydroponic condition were investigated. The plants were cultivated in Hoagland’s nutrient solution spiked with caffeine at concentrations of 0.5–2.0 mg L^?1. The effect of photodegradation on caffeine elimination was determined in dark controls and proved to be negligible. Removal of caffeine in mesocosms without plants showed however that biodegradation could account for about 15–19% of the caffeine lost from solutions after 3 and 7 d. Plant uptake played a significant role in caffeine elimination. Caffeine was detected in both roots and shoots of S. validus. Root concentrations of caffeine were 0.1–6.1 μg g^?1, while the concentrations for shoots were 6.4–13.7 μg g^?1. A significant (p < 0.05) positive correlation between the concentration in the root and the initial concentrations in the nutrient solution was observed. The bioaccumulation factors (BAFs) of caffeine for roots ranged from 0.2 to 3.1, while BAFs for shoots ranged from 3.2 to 16.9. Translocation from roots to shoots was the major pathway of shoot accumulation. The fraction of caffeine in the roots as a percentage of the total caffeine mass in solution was limited to 0.2–4.4% throughout the whole experiment, while shoot uptake percentage ranged from 12% to 25% for caffeine at the initial concentration of 2.0 mg L^?1 to 50–62% for caffeine at the initial concentration of 0.5 mg L^?1. However, a marked decrease in the concentration of caffeine in the shoots between d-14 and d-21 suggests that caffeine may have been catabolized in the plant tissues subsequent to plant uptake and translocation.     

Effective sorption of perfluorooctane sulfonate (PFOS) on hexadecyltrimethylammonium bromide immobilized mesoporous SiO2 hollow sphere

The hexadecyltrimethylammonium bromide (HDTMAB) immobilized hollow mesoporous silica spheres were prepared for the efficient removal of perfluorooctane sulfonate (PFOS) from aqueous solution. Besides the traditional sorption behavior including sorption kinetics as well as effect of solution pH and temperature, the effect of increasing volume which simulated the natural river where the rate of solute and solvent was relatively constant and solution volume was always changing was investigated. The result indicated that the residual PFOS concentrations in aqueous phase decreased with increasing solution pH and ionic strength, whereas they increased with increasing temperature. The HDTMAB immobilized material still maintained high efficiency after increasing volume, that is, the removal kept more than 99% after the treatment when the initial PFOS concentration was 1 mg L^?1. The uptake behavior and morphology of spheres which was characterized by transmission electron microscopy (TEM) revealed that the additional HDTMAB and mesoporous shell were responsible for the enhanced sorption of PFOS. It was concluded that electrostatic interaction and Ca-bridge role played an important role in the sorption of PFOS on the mesoporous SiO₂ hollow spheres, whereas, hydrophobic interaction contributed to the nice sorption performance of PFOS on the HDTMAB immobilized sorbent.     

氯过氧化物酶对苯酚生物降解的促进作用

氯过氧化物酶是一种底物广泛的手性催化剂,可以催化卤素离子、芳香族化合物和醇类化合物等进行过氧化反应.利用氯过氧化物酶催化氧化苯酚,考察其对苯酚生物降解的促进作用.结果表明,500、1 000 mg/L苯酚在氯过氧化物酶为10 U/mL、pH为6.5、H2 O2投加量为10 mg/L时8h苯酚降解率分别达到86.6％和83.8％,比单纯菌株降解显著提高.说明氯过氧化物酶能快速清除苯酚污染的危害,提高苯酚的生物降解速率.     

天然和CPB改性沸石对Hg^2＋的吸附特征

通过静态实验研究溴代十六烷基吡啶（CPB）改性沸石和天然沸石对废水中Hg^2＋的吸附特性,探讨了吸附动力学、吸附平衡和吸附热力学机制。研究表明：Langmuir方程能较好地描述2种沸石对Hg^2＋的吸附,CPB改性沸石对Hg^2＋的吸附率得到显著提高。实验条件下,改性沸石对Hg^2＋的吸附率从67．5％提高到98．9％,吸附容量从0．521mg／g提高到3．07mg／g。利用准一级动力学方程、假二级动力学方程、颗粒内扩散模型和Elovich方程分别对动力学过程进行拟合,发现2种沸石对Hg^2＋的吸附均满足假二级动力学方程,且离子的颗粒内扩散对整个吸附过程有影响。动力学拟合、D-R方程拟合和热力学研究综合表明：2种沸石对Hg^2＋的吸附既存在化学吸附又存在物理吸附,吸附吉布斯自由能变（△G^0）、焓变（△H^0）、熵变（△S^0）均小于0,反应为自发的放热反应,低温有利于吸附的进行。     

腐熟蓝藻与厌氧污泥混合厌氧发酵特性

采用批次小试实验对不同腐熟程度的蓝藻进行厌氧发酵产沼气实验研究。结果表明,新鲜蓝藻在30-35℃时腐熟7 d后,可在35℃的厌氧温度下获得最高的产气速率和246 mL/g COD的产气量,产气潜力为354 mL/g（VS）。厌氧反应15 d后,累计产气量、COD和VFA浓度趋于稳定。淀粉酶和脱氢酶的活性在厌氧反应初期受到抑制,蛋白酶活性和辅酶F420浓度在厌氧系统中逐渐增加,分别在第6天达到27.66μmol/（g VS·min）和第15天达到0.62μmol/g（VS）。15-18d是腐熟蓝藻适宜的中温厌氧发酵时间,少于以新鲜蓝藻为基质的厌氧消化时间。蓝藻腐熟过程促进了厌氧反应,腐熟7 d的蓝藻厌氧系统具有更高的微生物活性和产甲烷能力。     

多孔硅酸钙滤料吸附床除磷试验研究

以多孔硅酸钙滤料为吸附载体处理含磷的二沉池出水.通过静态吸附试验和动态吸附试验,研究了滤料粒径及投加量、初始pH、反应时间、温度以及滤料填充高度对除磷效果的影响.在静态吸附试验中,取初始磷质量浓度为4.98 mg/L的含磷废水100 mL,当多孔硅酸钙滤料粒径为4～14目,投加量为1.0g,吸附时间为2.5h,温度为25℃,溶液初始pH为7.0～9.0时,磷的去除率可达95％以上,出水磷满足《城镇污水处理厂污染物排放标准》(GB 18918-2002)的一级A标准(≤0.5 mg/L).动态吸附试验表明,在长期运行条件下,多孔硅酸钙滤料吸附床能持续有效地去除污水中的磷,综合考虑吸附率和运行费用,选择水力停留时间为30 min,滤料填充高度为60 cm为宜.