Adsorption behavior of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) on boehmite

Understanding the interaction of perfluorochemicals, persistent pollutants with known human health effects, with mineral compounds in surface water and groundwater environments is essential to determining their fate and transport. Kinetic experiments showed that adsorption equilibrium can be achieved within 48 h and the boehmite (AlOOH) surface is receptive to perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorption. The adsorption isotherms estimated the maximum adsorption capacities of PFOS and PFOA on boehmite as 0.877 μg m⁻² and 0.633 μg m⁻², respectively. Compared to the adsorption capacity on γ-alumina, the abundant hydroxyl groups on boehmite surfaces resulted in the 2-3 times higher adsorption of PFOS and PFOA. Increasing solution pH led to a moderate decrease in PFOS and PFOA adsorption, owing to an increase in ligand exchange reactions and the decrease of electrostatic interactions. The presence of NaCl and CaCl₂ in solution demonstrated negative effects for PFOS and PFOA adsorption on boehmite surfaces, with potential mechanisms being electrical double layer compression, competitive adsorption of chloride, and the Ca²⁺ bridging effect between perfluorochemicals.     

Perfluorinated compounds in whole fish homogenates from the Ohio, Missouri, and Upper Mississippi Rivers, USA

A method for the analysis of 10 perfluorinated compounds (PFCs) in whole fish homogenate is presented and applied to 60 fish samples collected from the Ohio, Missouri, and upper Mississippi Rivers in 2005. Method accuracy ranged between 86 and 125% with limits of quantitation between 0.2 and 10 ng/g wet weight. Intra- and inter-batch precision was generally ±20%. Perfluorooctane sulfonate (PFOS) was the predominant compound identified in these samples, contributing over 80% of total PFC composition in the fish from these rivers, with median PFOS concentrations of 24.4, 31.8, and 53.9 ng/g wet wt in the Missouri, Ohio, and Mississippi Rivers, respectively. Median PFOS levels were significantly (p = 0.01) elevated in piscivorous fish (88.0 ng/g) when compared with non-piscivorous fish (15.9 ng/g). The 10 samples with PFOS concentrations above 200 ng/g were broadly scattered across all three rivers, providing evidence of the widespread presence of this compound in these US waterways.     

Partitioning of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS) and perfluorooctane sulfonamide (PFOSA) between water and sediment

Laboratory partitioning experiments were conducted to elucidate the sorption behaviour and partitioning of perfluoroalkyl compounds (PFCs). Three different sediment types were used and separately spiked with perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS) and perfluorooctane sulfonamide (PFOSA) at low environmentally realistic concentrations. PFOA, PFOS and PFOSA were mainly distributed in the dissolved phase at low suspended solid concentrations, indicating their long-range transport potential in the marine environment. In all cases, the equilibrium isotherms were linear and the organic carbon normalised partition coefficients (K_OC) decreased in the following order: PFOSA (log K_OC = 4.1 ± 0.35 cm³ g⁻¹) > PFOS (3.7 ± 0.56 cm³ g⁻¹) > PFOA (2.4 ± 0.12 cm³ g⁻¹). The level of organic content had a significant influence on the partitioning. For the sediment with negligible organic content the density of the sediment became the most important factor influencing the partitioning. Ultimately, data on the partitioning of PFCs between aqueous media and suspended solids are essential for modelling their transport and environmental fate.     

Background levels of Persistent Organic Pollutants in humans from Taiwan: Perfluorooctane sulfonate and perfluorooctanoic acid

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have recently received attention due to their widespread contamination of the environment. PFOS and PFOA are stable in the environment and resistant to metabolism, hydrolysis, photolysis and biodegradation. PFOS and PFOA have been found in human blood and tissue samples from both occupationally exposed workers and the general worldwide population. This study aimed to determine the background levels of PFOS and PFOA in the Taiwanese population, investigate related factors, and compare exposure in Taiwan to that in other countries. The concentration of PFOS in the 59 serum samples collected from the general population in Taiwan ranged from 3.45 to 25.65 ng mL⁻¹ (median: 8.52), and the concentration of PFOA ranged from 1.55 to 7.69 ng mL⁻¹ (median: 3.22). There was a significant positive correlation (r = 0.51; p < 0.0001) between PFOS and PFOA concentrations. Males had higher concentrations of PFOA and PFOS than females. PFOS levels in serum increased with age. This study is the first investigation to reveal the PFOS and PFOA levels of serum samples in the general population of Taiwan. The levels of PFOS and PFOA in Taiwanese serum samples were comparable with those from other countries (PFOS: 5.0–35 ng mL⁻¹, PFOA: 1.5–10 ng mL⁻¹).     

Occurrence and dietary exposure assessment of PFOS and PFOA in cultured Trachinotus ovatus in China

In this study, investigation was conducted into concentrations of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in Chinese farmed Trachinotus ovatus between 2014 and 2015 using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) and ultra fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method. The tissue distribution (muscle, skin, liver, kidney and gill) in Trachinotus ovatus was also assessed. The detection frequencies of PFOS and PFOA in fish were 92% and 3%, respectively, and the mean concentrations were 0.392 and 0.015 μg/kg wet weight. The analysis of PFOS distribution in different tissues in Trachinotus ovatus showed the following trend: skin> gill> kidney> liver> flesh. Results revealeded farmed Trachinotus ovatus in China to generally be contaminated with PFOS. Moreover, the average daily intake for Chinese urban residents calculated on the basis of pollution content was 0.268 ng/kg body weight/d (PFOS) and 0.014 ng/kg body weight /d (PFOA), respectively. Both hazard ratio values were less than 1, indicating that exposure levels of PFOS and PFOA through Trachinotus ovatus consumption may not lead to adverse health effects in the Chinese population.     

Distribution and sources of polyfluoroalkyl substances (PFAS) in the River Rhine watershed

The concentration profile of 40 polyfluoroalkyl substances (PFAS) in surface water along the River Rhine watershed from the Lake Constance to the North Sea was investigated. The aim of the study was to investigate the influence of point as well as diffuse sources, to estimate fluxes of PFAS into the North Sea and to identify replacement compounds of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). In addition, an interlaboratory comparison of the method performance was conducted. The PFAS pattern was dominated by perfluorobutane sulfonate (PFBS) and perfluorobutanoic acid (PFBA) with concentrations up to 181 ng/L and 335 ng/L, respectively, which originated from industrial point sources. Fluxes of ΣPFAS were estimated to be ∼6 tonnes/year which is much higher than previous estimations. Both, the River Rhine and the River Scheldt, seem to act as important sources of PFAS into the North Sea.     

Simultaneous extraction of Cr(VI) and Cu(II) from humic acid with new synthesized EDTA derivatives

Soil washing is one of the few permanent treatment alternatives for removing metal contaminants. Ethylenediaminetetraacetic acid and its salts (EDTA) is very effective at removing cationic metals and has been utilized globally. However it is ineffective for anionic metal contaminants or metals bound to soil organic matter. The simultaneous removal of cationic and anionic metal contaminants by soil washing is difficult due to differences in their properties. The present study evaluated the potential of a washing process using two synthesized EDTA-derivatives, C₆HEDTA (2,2′-((2-((carboxymethyl)(2-(hexanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid) and C₁₂HEDTA (2,2′-((2-((carboxymethyl) (2-(dodecanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid), which consist of a hydrophilic polycarboxylic moiety and a hydrophobic moiety with a monoalkyl ester group. A series of equilibrium batch experiments at room temperature were conducted to investigate the efficacy of C₆HEDTA and C₁₂HEDTA as extractants for both oxyanion Cr(VI) and cationic Cu(II). Results showed that either C₆HEDTA or C₁₂HEDTA can extract both Cr(VI) and Cu(II) from humic acid simultaneously. However, C₆HEDTA was less effective for Cr(VI) probably because it has no surface activities to increase solubility of humic acid, like C₁₂HEDTA. Extraction of Cr(VI) was mainly attributed to the decreased surface tension and enhanced solubility of organic matter. Extraction of Cu(II) was attributed to both the Cu(II) chelation and enhanced solubility of humic acid. It was demonstrated that the hydrophilic polycarboxylic moiety of C₁₂HEDTA chelates cations while the monoalkyl ester group produces surface active properties that enhance the solubility of humic acid.     

Perfluorinated Surfactants in Surface and Drinking Waters (9 pp)

Background, Aim and Scope In this paper recent results are provided of an investigation on the discovery of 12 perfluorinated surfactants (PS) in different surface and drinking waters (Skutlarek et al. 2006 a, Skutlarek et al. 2006 b). In the last years, many studies have reported ubiquitous distribution of this group of perfluorinated chemicals, especially perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in the environment, particularly in wildlife animal and human samples (Giesy and Kannan 2001, Houde et al. 2006, Prevedouros et al. 2006). Perfluorinated surfactants (e.g. PFOS and PFOA) have shown different potentials for reproductory interference and carcinogenity in animal experiments as well as partly long half-lives in humans (Guruge et al. 2006, FSA UK 2006a, FSA UK 2006b, 3M 2005, OECD 2002, Yao and Zhong 2005). They possess compound-dependent extreme recalcitrance against microbiological and chemical degradation and, in addition, they show variable potentials for bioaccumulation in animals and humans (Houde et al. 2006). Materials and Methods: Surface and drinking water samples were collected from different sampling sites: - Surface waters: samples taken from the rivers Rhine, Ruhr, Moehne and some of their tributaries. Further samples were taken from the Rhine-Herne-Canal and the Wesel-Datteln-Canal. - Drinking waters: samples taken in public buildings of the Rhine-Ruhr area. After sample clean-up and concentration by solid-phase extraction, the perfluorinated surfactants were determined using HPLC-MS/MS. Results: All measured concentrations (sum of seven mainly detected components) in the Rhine river and its main tributaries (mouths) were determined below 100 ng/L. The Ruhr river (tributary of the Rhine) showed the highest concentration (94 ng/L), but with a completely different pattern of components (PFOA as major component), as compared with the other tributaries and the Rhine river. Further investigations along the Ruhr river showed remarkably high concentrations of PS in the upper reaches of the Ruhr river and the Moehne river (tributary of the Ruhr) (Ruhr: up to 446 ng/L, Moehne: up to 4385 ng/L). The maximum concentration of all drinking water samples taken in the Rhine-Ruhr area was determined at 598 ng/L with the major component PFOA (519 ng/L). Discussion: The surface water contaminations most likely stem from contaminated inorganic and organic waste materials (so-called 'Abfallgemisch'). This waste material was legally applied to several agricultural areas on the upper reaches of the Moehne. Perfluorinated surfactants could be detected in some suchlike soil samples. They contaminated the river and the reservoir belonging to it, likely by superficial run-off over several months or probably years. Downstream, dilution effects are held responsible for decreasing concentrations of PS in surface waters of the Moehne and the Ruhr river. In analogy to the surface water samples, PS (major component PFOA) can be determined in many drinking water samples of the Rhine-Ruhr area where the water supplies are mainly based on bank filtration and artificial recharge. Conclusions: The concentrations found in drinking waters decreased with the concentrations of the corresponding raw water samples along the flow direction of the Ruhr river (from east to west) and were not significantly different from surface water concentrations. This indicates that perfluorinated surfactants are at present not successfully removed by water treatment steps. Recommendations and Perspectives: Because of their different problematic properties (persistence, mobility, toxicity, bioaccumulation), the concentrations of specific perfluorinated surfactants and their precursors in drinking waters and food have to be minimised. Therefore, it is of utmost importance to take the initiative to establish suitable legal regulations (limitations/ban) concerning the production and use of these surfactants and their precursors. Furthermore, it is indispensable to protect water resources from these compounds. A discussion on appropriate limit values in drinking water and foodstuffs is urgently needed. Concerning the assumed soil contamination, the corresponding regulation (Bioabfall-Verordnung 1998 – Regulation on Organic Waste 1998) should be extended to allow the control of relevant organic pollutants.     

Spatial and Seasonal Variations of Disinfection Byproducts (DBPs) in Drinking Water Distribution Systems of Istanbul City,Turkey

This study presents the seasonal and spatial variations of trihalomethanes (THMs) and haloacetic acids (HAAs) in 30 sampling points within three water distribution systems of Istanbul City, Turkey. The effects of surface water quality, seasonal variation, and species differences were examined. The occurrence of chlorinated THMs and HAAs levels was considerably lower in the system in which raw water is subjected to pre-ozonation versus pre-chlorination. Seasonal analysis of the data indicated that the median concentration of four THMs (THM₄) was higher than nine HAAs (HAA₉) concentrations in all three distribution systems sampling points. For all distribution systems monitored, the highest median THM₄ and HAA₉ concentrations were observed in the spring and summer season, while the lowest concentrations of these disinfection byproduct (DBP) compounds were obtained in the fall and winter period. Due to the higher level of bromide in supplying waters of these two systems, moderate levels of brominated DBP species have been observed in the Kagithane and Buyukcekmece distribution systems districts. In fact, Spearman partial correlations (Spearman rank correlation coefficients [rs]) tend to be higher among analogues in terms of number and types of substituent, especially TCAA with TCM (rs 0.91), and DBAA with DBCM (rs 0.90). In contrast, the hydraulic (residence time and flow rate) and chemical mechanisms (hydrolysis, volatilization, and adsorption) affect the fate and transport of DBPs in distribution systems. Seasonal and spatial variations of DBPs presented in this study have important implications on regulatory issues and from an epidemiological point of view.     

Occurrence, sources, and inventory of hexabromocyclododecanes (HBCDs) in soils from Chongming Island, the Yangtze River Delta (YRD)

Hexabromocyclododecanes (HBCDs) is a concern due to their large usage combining with physico-chemical properties and toxicity to wildlife and human. However, very limited data were reported on HBCDs in soils, especially from rural area. In this study, 22 soil samples were collected from Chongming Island at estuary of the Yangtze River Delta, to investigate the level, diasteroisomer profile, potential sources, and mass inventory of HBCDs. The total concentrations ranged from not detected to 93.8 pg g⁻¹ dry weight (dw) with a mean of 23.3 pg g⁻¹ dw, which was at the low end of the global levels. The wide distribution of HBCDs in soils suggested that the local emissions of HBCD-containing materials and/or the inputs via atmospheric transport from other regions were two possible sources. Variation of HBCDs levels was observed in different types of soils. Woodland, tideland and road soils contained slightly higher HBCDs than those of farmland and grassland. Overall, γ-HBCD was the dominant diasteroisomer in soils, followed by α-HBCD and β-HBCD. Significant but weak correlations were only found between α-HBCD and β-HBCD versus TOC content in soils. Currently, the mass inventory of HBCDs in soils of Chongming Island was 5.3 kg. Based on these data, we gave perspective on human intake of HBCDs via soil ingestion by age. Local resident’s intakes ranged from 15.5 to 97.8 fg kg body weight⁻¹ d⁻¹, in which children are exposed more than adults.     

Determination of C(5)-C(12) perfluoroalkyl carboxylic acids in river water samples in the Czech Republic by GC-MS after SPE preconcentration

A method employing solid phase extraction followed by gas chromatography-mass spectrometry with negative chemical ionization has been developed for determination of ultratrace concentrations of perfluoroalkyl carboxylic acids in river water. The effects of the experimental parameters, such as the pH, additions of NaCl and an ion-pairing agent (tetraethylammonium bromide) and the kind of the elution agent, on the efficiency of the test acid extraction have been studied. The analyte extraction recoveries and the limits of detection and determination have been found. The method developed has been tested on determinations of perfluoroalkyl carboxylic acids in the waters of the two largest Czech rivers, Vltava and Labe (Elbe). The best extraction results have been attained without any alteration of the sample pH, with an addition of tetrabutylammonium bromide (a concentration of 50 μg mL⁻¹ in the sample) and using methanol as the elution agent. Under these conditions, the recoveries of the test acids in the spiked real samples are within ranges from 60% to 104% and 53% to 111% for analyte concentration levels of 1.40 ng mL⁻¹ and 0.14 ng mL⁻¹, respectively, depending on the lengths of the perfluorinated chains of the acids. In general, the recovery decreases with increasing length of this chain. The method developed exhibits very low limits of detection and determination and the results are fully comparable with those obtained when using more expensive HPLC-MS/MS instrumentation. Typical values amount to tenths to tens of pg mL⁻¹ and units to one hundred pg mL⁻¹ for the limits of detection and determination, respectively; the measuring sensitivity increases with increasing length of the analyte chain. The analyzes of real samples from the Vltava and Elbe rivers have demonstrated that the results obtained are similar to the values published for contamination of the Elbe and other rivers in western and central Europe. The concentrations determined are of the order of units to tens of pg mL⁻¹ and the C₈-C₁₀ acids occur most often.     

COD、pH值和运行周期对好氧瞬时补料工艺合成聚羟基脂肪酸酯的影响

聚羟基脂肪酸酯（PHA）是一种可生物降解塑料,具有良好的应用前景。混合菌种生产PHA是目前PHA生产的研究重点。以乙酸钠为碳源用好氧瞬时补料（ADF）工艺驯化出了生产聚羟基脂肪酸酯（PHA）的混合菌种。PHA含量在加入营养液后4和10 h达到最大值。研究了营养液COD、pH值和SBR运行周期对PHA生产的影响。COD=12 000 mg·L-1和运行周期12 h均会引发污泥膨胀;COD=3 000 mg·L-1和运行周期48 h会导致污泥流失。pH=7的中性环境下PHA生产菌不具备竞争优势;pH=10时微生物细胞活性受抑制。最适条件为COD=6 000 mg·L-1,pH=8.5,运行周期=24 h,此时得到PHA含量最大值31.1%。     

Vertical Profile of Acid Volatile Sulfide (AVS) and Risk Assessment of Sediments from Baihua Lake,China

Acid volatile sulfide (AVS), simultaneously extracted metals (SEMs), and total concentrations of trace elements (Cu, Cd, Pb, Zn, Ni, Hg, As, and Cr) were studied in sediment cores from Baihua Lake in southwest China. The molar ratios of SEMs to AVS for all samples were lower than 1.0 except for the 25- to 30-cm layer of the sample collected at location YPZ, indicating that the heavy metals were currently not significantly bioavailable as a whole to benthic organisms. Based on the sediment quality guidelines and the potential ecological risk assessment, Hg presented a high ecological risk for the water body.     

Chemical recycling of poly(ethylene terephthalate) (pet) by hydrolysis and glycolysis

In this paper we review an interesting method of PET recycling, i.e. chemical recycling; it is based on the concept of depolymerizing the condensation polymer through solvolytic chain cleavage into low molecular products which can be purified and reused as raw materials for the production of high-quality chemical products. In this work our attention is confined to the hydrolysis (neutral, acid and alkaline) and glycolysis processes of PET chemical recycling; operating conditions and mechanism of each method are reported and described. The neutral hydrolysis has an auto accelerating character; two kinetic models have been proposed: an half-order and a second order kinetic model. The acid hydrolysis could be explained by a modified shrinking core model under chemical reaction control and the alkaline hydrolysis by a first-order model with respect to hydroxide ion concentration. To describe glycolysis, two different kinetic models have been proposed where EG can act or not as internal catalyst. Further experimental and theoretical investigations are required to shed light on the promising processes of PET chemical recycling reviewed in this work.     

Comparison of the Photodegradation of Imazethapyr in Aqueous Solution,on Epicuticular Waxes,and on Intact Corn (Zea Mays) and Soybean (Glycine Max) Leaves

A direct, controlled comparison of the photodegradation of imazethapyr has been made between imazethapyr in aqueous solutions, imazethapyr on the surface of epicuticular waxes of corn and soybean plants, and imazethapyr on the surface of intact corn and soybean plant leaves. In some experiments, the imazethapyr solutions were allowed to evaporate partially or fully after application to better model environmental conditions. The photodegradation of imazethapyr was fastest in aqueous solutions (k?=?0.16?±?0.02?h^?1) and slowest on the surface of corn and soybean plants (k_corn?=?0.00048?±?0.001?h^?1 and k_soy?=?0.00054?±?0.003?h^?1). Experiments allowing evaporation during irradiation have intermediate rate constants (e.g., k_corn?=?0.082?±?0.005?h^?1). Finally, identification of photoproducts was also examined on epicuticular waxes of corn and soybean plants for the first time.     

Melting and incineration plants of municipal waste. Chemical and biochemical diagnosis of thermal processing samples (emission,residues)

Control of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in emissions and thermal residues from incinerators has been a cause of public concern for more than one decade. Recently, several studies showed that other persistent organic pollutants (POPs) such as coplanar polychlorinated biphenyls (co-PCBs) also have dioxin-like activity and are released from incinerators. Therefore, the present study was aimed at making a risk assessment about dioxin-like activity in extracts of thermal waste residues (e.g. combustion gas; fly ash, slag) from incineration and melting processes in Germany and Japan. For this purpose, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), coplanar polychlorinated biphenyls (co-PCBs), polychlorinated naphthalenes (PCNs) and polyaromatic hydrocarbons (PAHs) were analyzed by chemical analysis. Additionally, 2, 3, 7, 8-TCDD equivalents (EROD-TEQs) were determined by in vitro Micro-EROD bioassay using rat H4IIE hepatoma cells. EROD-TEQs could be correlated to I-TEQ values (from PCDD/Fs/co-PCBs) analyzed by chemical analysis resulting in a maximal sixfold higher estimate. Our study indicates minor influences of co-PCBs, PAHs and PCNs to the sum of dioxin-like toxicity in the extracts of thermal waste residues as determined here. Furthermore, we showed that the levels of dioxins and co-PCBs contained in slag from melting processes and bottom ashes from incineration processes were lower by 1-2 orders of magnitude than that in fly ash.     

The impact of production type and region on polychlorinated biphenyl (PCB), polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) concentrations in Canadian chicken egg yolks

Chicken eggs from five different production types (conventional, omega-3 enriched, free range, organic and free run) were collected, when available, from three regions (west, central and east) of Canada to determine persistent organic pollutant (POP) concentrations. Total polychlorinated biphenyl (PCB) concentrations (∑37 congeners) in yolks from the eggs ranged from 0.162 ng g⁻¹ lipid to 24.8 ng g⁻¹ lipid (median 1.25 ng g⁻¹ lipid) while the concentration of the sum of the 6 indicator PCBs ranged from 0.100 ng g⁻¹ lipid to 9.33 ng g⁻¹ lipid (median 0.495 ng g⁻¹ lipid). Total polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) concentrations ranged from 2.37 pg g⁻¹ lipid to 382 pg g⁻¹ lipid (median 9.53 pg g⁻¹ lipid). The 2005 WHO toxic equivalency (TEQ) ranged from 0.089 pg TEQ_{PCDD/F+dioxin-like[DL]-PCB} g⁻¹ lipid to 12.8 pg TEQ_{PCDD/F+DL-PCB} g⁻¹ lipid (median 0.342 pg TEQ_{PCDD/F+DL-PCB} g⁻¹ lipid). PCB and PCDD/F concentrations were significantly different (p < 0.001) in egg yolks from different regions of collection. In contrast to observations in Europe, PCB and PCDD/F concentrations in Canadian egg yolks were not impacted solely by the production type (e.g., conventional, free range, organic, etc.) used to maintain the laying chickens. Additionally, only one Canadian free range yolk from western Canada (12.8 pg TEQ_{PCDD/F+DL-PCB} g⁻¹ lipid) exceeded the European toxic equivalent concentration limits for eggs (5 pg TEQ_{PCDD/F+DL-PCB} g⁻¹ lipid). This differs from observations in Europe where free range/home produced eggs frequently have higher POP concentrations than eggs from other production types. Median PCB dietary intake estimates based on consumption of eggs were less than 10 ng d⁻¹ while median PCDD/F intakes were less than 45 pg d⁻¹.     

柠檬酸对褐土中DTPA提取态铜、镉含量及对紫花苜蓿吸收铜、镉的影响

为了阐述有机酸对土壤中重金属生物有效性的影响,通过盆栽实验,研究了Cu、Cd复合污染下柠檬酸对褐土中二乙基三胺五乙酸(DTPA)提取态铜和镉含量的影响,并探讨了柠檬酸对植物吸收铜、镉的影响。结果表明,土壤中DT-PA-Cu含量随柠檬酸添加量的增加而减小,添加高浓度铜(Cu 1 000)处理中,DTPA-Cu含量减小更明显。在添加低铜浓度(Cu600)处理下,柠檬酸添加量为2和12 mmol/kg时,土壤DTPA-Cu含量随土壤镉含量的增加而增加,而柠檬酸含量为5mmol/kg时,DTPA-Cu含量在低镉处理(Cd 1)时含量最低。紫花苜蓿中铜含量随柠檬酸添加量的增加明显降低。土壤中DTPA-Cd含量随柠檬酸添加量的增加而减小,且随铜添加量的增加而降低。紫花苜蓿中的镉含量随柠檬酸添加量的增加先增加后减小;在相同柠檬酸添加量处理时,紫花苜蓿中镉的含量随镉含量的增加而增加;在低镉处理下,铜的加入对较低柠檬酸浓度时紫花苜蓿镉含量影响不明显,但柠檬酸浓度为12 mmol/kg时,紫花苜蓿中镉含量随铜添加量的增加而明显增加。     

Quantification of the interactions between Ca,Hg and extracellular polymeric substances (EPS) of sludge

The interactions between metals (Ca²⁺ and Hg²⁺) and extracellular polymeric substances (EPS) extracted from the aerobic and anaerobic sludge in wastewater treatment reactors were investigated using a combination of zeta potential measurement and 3-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analysis. Results show that Ca²⁺ had no substantial effects on the EEM fluorescence spectra of the EPS, but their zeta potentials increased with the increasing Ca²⁺ dosage. However, Hg²⁺ had a significant effect on the EEM fluorescence spectra of the EPS, while their zeta potentials seemed not to be affected by the dose of Hg²⁺. The interactions between Hg²⁺ and EPS were elucidated using the fluorescence quenching with PARAFAC analysis, while the interactions between Ca²⁺ and EPS were evaluated by the zeta potential technique. The binding constants for Hg²⁺ and EPS were two orders of magnitude higher than those for Ca²⁺ and EPS, suggesting that the binding mechanisms between Ca²⁺ and EPS were different from those between Hg²⁺ and EPS. The results might be useful for understanding the roles of EPS in bacterial self-protection against heavy metals and the aggregate formation mechanisms through ionic bridging interactions.     

累托石/腐殖酸微球的制备及其对Cr(Ⅵ)的吸附研究

采用累托石（REC）、腐殖酸（HA）等材料制备微球状吸附剂,考察了累托石、腐殖酸、聚乙烯醇（PVA）、海藻酸钠（SA）、氯化钙等材料的用量对制得的微球吸附性能的影响,通过正交试验确定了微球的最佳制备条件,还考察了微球用量、振荡时间和溶液pH值等因素对微球吸附去除水中Cr(VI)效果的影响。结果表明,采用累托石、腐殖酸、聚乙烯醇等材料可制得高效去除水中六价铬离子的微球状吸附剂,微球的最佳制备条件为：REC 1%,HA 4%,PVA 7%,SA 0.1%,CaCl₂ 0.5%。制得的累托石/腐殖酸微球孔系发达,吸附性能良好。在温度30℃,微球用量0.02 g/mL,振荡时间为2.5 h,pH值为1的条件下,微球对Cr(VI)的吸附效率可达98%以上。