Toxic interaction mechanism of two fluoroquinolones with serum albumin by spectroscopic and computational methods

To evaluate the toxicity of two fluoroquinolones (FQs), ciprofloxacin (CPFX), and enrofloxacin (ENFX), at the protein level, their binding modes with bovine serum albumin (BSA) were characterized by multiple spectroscopic and molecular docking methods under simulated physiological conditions. On the basis of fluorescence spectra, we concluded that both FQs greatly quenched the fluorescence intensity of BSA, which was attributed to the formation of a moderately strong complex mainly through electrostatic interactions. Besides, CPFX posed more of an affinity threat than ENFX. The molecular docking methods further illustrated that both CPFX and ENFX could bind into the subdomain IIIA of BSA and interact with Arg 508 and Lys 437, the positively charged residues in protein. Furthermore, as shown by the synchronous fluorescence, UV-Visible absorption and circular dichroism data, both CPFX and ENFX could lead to the conformational and microenvironmental changes of BSA, which may affect its physiological function.     

Investigation on the interaction between triclosan and bovine serum albumin by spectroscopic methods

Abstract

Multi-spectroscopic and molecular docking methods were used to study the interaction between triclosan (TCS) and bovine serum albumin (BSA). The results indicated that the fluorescence quenching of BSA by TCS was due to the formation of TCS–BSA complex through static quenching. This result was also demonstrated by time-resolved fluorescence experiment. The binding constants and number of binding sites between TCS and BSA were 1.30?×?10⁵ M^?1 and 1.17 at 298?K, respectively. The thermodynamic parameters were studied in detail which suggested that hydrophobic forces and hydrogen bond played major roles in the TCS–BSA interaction. Moreover, the site marker competitive experiments and docking studies revealed that TCS could bind BSA into site I in subdomain IIA. All the results of UV–vis spectrophotometry, circular dichroism spectroscopy and synchronous fluorescence spectroscopy showed that interaction between TCS and BSA induced conformation changes of BSA.     

Sunlight-induced degradation of soil-adsorbed veterinary antimicrobials Marbofloxacin and Enrofloxacin

Marbofloxacin (MAR) and Enrofloxacin (ENR), two largely employed veterinary Fluoroquinolones (FQs), were found to be present at the micrograms per kilogram level in agricultural soils of South Lombardy (Italy) several months after manuring. Distribution coefficients (K_d) from sorption experiments indicated a strong binding to the soil. Soil samples fortified with environmentally significant FQs amounts (0.5 mg kg⁻¹) were exposed to solar light that promoted extensive degradation (80%) of both drugs in 60-150 h. Thus, photochemistry could be considered a significant depollution path in the soil, although it was two orders of magnitudes slower than in aqueous solution and a fraction of the drug (ca. 20%) remained unaffected. For MAR the photoprocess was the same as in solution, and involved cleavage of the tetrahydrooxadiazine ring. On the contrary, with ENR only some of the photoproducts determined in water (those arising from a stepwise oxidation of the piperazine side chain) were observed. Substitution of the 6-fluoro by a hydroxyl group and reduction did not occur in the soil, supporting the previous contention that such processes required polar solvation of FQs. Consistently with this rationalization, the irradiation of thin layers of solid drugs led to essentially the same products distribution as in the soil. From the environmental point of view it is important to notice that photodegradation mainly affects the side-chains, while the fluoroquinolone ring, to which the biological effect is associated, is conserved up to the later stages of the degradation.     

Pesticide binding and urea-induced controlled release applications with calixarene naphthalimide molecules by host–guest complexation

ABSTRACT

Three novel calix[4]arene molecule-based 1,8 naphthalimide fluoroionophore for the selective determination of kesoxim-methyl were synthesized and used in pesticide binding studies. The possible interaction between pesticides and fluorescent calix[4]arene molecules was monitored by UV/Vis absorption and fluorescence spectroscopy. When compared the studied pesticides, kesoxim-methyl was strongly quenched the fluorescence intensity of upper rim-modified calix[4]arene. UV and fluorescence titration experiments were also studied to determine both the quenching mechanism and stoichiometric ratio consisted in complex formation. Furthermore, pesticide release experiments were also performed with a fertilizing agent as urea by using fluorescence spectroscopy technique.     

Isolation and characterization of dissolved organic matter fractions from antialgal products of Microcystis aeruginosa

An antialgal bacterium, Streptomyces sp. HJC-D1, was applied for the biodegradation of cyanobacterium Microcystis aeruginosa, and the isolation and characterization of dissolved organic matter (DOM) fractions in antialgal products were studied. Results showed the the growth of M. aeruginosa was significantly inhibited by the cell-free filtrate of Streptomyces sp. HJC-D1 with the growth inhibition of 86?±?7 %. The antialgal products were divided using resin adsorbents into the hydrophilic fraction (HPI), hydrophobic acid (HPO-A), transphilic acid (TPI-A), hydrophobic neutral and transphilic neutral, and then the five fractions were analyzed by the 3-D fluorescence spectroscopy, gel permeation chromatography, and Fourier transform infrared spectroscopy. The results indicated that the HPI component was the most abundant DOM fraction in the antialgal products, and its concentration was increased with the increase of cell-free filtrate concentration. The fluorescence peak location and intensity analysis showed that the protein-, fulvic-, and humic-like substances were dominant in the HPI, HPO-A, and TPI-A fractions, and intensities of the relevant fluorescence peaks were stronger in the experimental groups than those of the control groups. It was also found that the number-average molecular weight of DOM fractions ranged from 245 to 1,452 g mol^?1, and thereinto organic acids such as HPO-A and TPI-A exhibited lower molecular weights.     

Carbon dioxide adsorption on amine-impregnated mesoporous materials prepared from spent quartz sand

Mesoporous MCM-41 was synthesized using cetyltrimethyl ammonium bromide (CTAB) as a cationic surfactant and spent quartz sand as the silica source. Modification of the mesoporous structure to create an absorbent was then completed using 3-aminopropyltrimethoxysilane. Amine-Quartz-MCM (The A-Q-MCM) adsorbents were then characterized by N₂ adsorption/desorption, elemental analysis (EA), X-ray fluorescence (XRF), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), as well as the carbon dioxide (CO₂) adsorption/desorption performance. In this study, spent quartz sand was utilized to synthesize Quartz-MCM (Q-MCM) and the amine functionalized material, A-Q-MCM, which exhibited a higher uptake of CO₂ at room temperature compared with the nongrafted material. The results showed that Q-MCM is similar to MCM-41 synthesized using commercial methods. The surface area, pore volume, and pore diameter were found to be as high as 1028 m²/g, 0.907 cm³/g, and 3.04 nm, respectively. Under the condition of CO₂ concentration of 5000 ppm, retention time of 50 cc/min, and the dosage of 1 g/cm³, the mean adsorption capacity of CO₂ onto A-Q-MCM was about 89 mg/g, and the nitrogen content of A-Q-MCM was 2.74%. The adsorption equilibrium was modeled well using a Freundlich isotherm.

Implications:In this study, spent quartz sand was utilized to synthesize Q-MCM. The amine functionalized material exhibited a higher uptake of CO₂ at room temperature compared with the nongrafted material. The results showed that Q-MCM is similar to MCM-41 synthesized using commercial methods. The adsorption equilibrium was modeled well using a Freundlich isotherm.     

The complexation of Cu(II) by anthropogenic fulvic acids extracted from composted urban and livestock wastes

Abstract

The fulvic acid (fua) fractions of two samples of composted solid wastes [urban (urfua) and livestock (lsfua) wastes], commercialized to be used in agriculture as organic correctives or fertilizers, were analyzed for their affinity towards Cu(II) at pH=6. Molecular fluorescence spectroscopy (synchronous mode) was used to monitor the quenching caused by the complexation upon addition of Cu(II) to fua. Spectral data were preprocessed by a chemometric self‐modeling mixture analysis method (SIMPLISMA) to detect the number of different types of fluorescent binding sites that exist in each fua, their spectra and the corresponding quenching profiles [fluorescence intensity as function of the total Cu(II) concentration]. From the analysis of the quenching profiles, the amount of binding sites (Cl) and the corresponding conditional stability constants (K') were calculated. Both fua samples have approximately Cl = 0.21 mmol/g and the logarithms of K’ are 4.21(3) and 4.51(8), respectively for urfua and lsfua. The differences detected between these fua samples and those extracted from natural soils can be attributed mainly to the relatively small humification extent of the present anthropogenic fua samples.     

Study on the mechanism of action between dimethyl phthalate and herring sperm DNA at molecular level

Dimethyl phthalate (DMP), a typical phthalic acid ester, is widespread in the environment and causes extensive concern due to its adverse effects on human health. To understand the genotoxicity of DMP at molecular level, the toxic interaction of DMP with herring sperm (hs) deoxyribonucleic acid (DNA; hs-DNA) was investigated in vitro under simulated physiological conditions using multi-spectroscopic techniques and a molecular modeling method. The results of Ultraviolet-Visible absorption spectroscopy, fluorescence emission spectroscopy, and circular dichroism spectra indicated that DMP interacts with hs-DNA in a groove-binding mode that changes the double helical structure of DNA. The binding constant and the number of binding sites calculated from the fluorescence quenching data were 565.718 L mol^?1 and 0.7872, respectively. A molecular modeling study revealed that DMP tends to bind with DNA in the A-T-rich regions of minor groove and that hydrogen bonding and van der Waals forces play main roles in the interaction. This research can help to elucidate the mechanism of DMP toxicity in vivo.     

Environmental metabolites of fluoroquinolones: synthesis, fractionation and toxicological assessment of some biologically active metabolites of ciprofloxacin

Background, aim, and scope

Biowastes produced by humans and animals are routinely disposed of on land, and concern is now growing that such practices provide a pathway for fluoroquinolone (FQs) antibacterial agents and their environmental metabolites (FQEMs) to contaminate the terrestrial environment. The focus of concern is that FQs and FQEMs may accumulate in amended soils to then adversely impact on the terrestrial environment. One postulated impact is the development of a selective environment in which FQ-resistant bacteria may grow. To find evidence in support of an accumulation of antibacterial-like activity, it was first necessary to establish whether any biologically active FQEMs could be synthesized by physicochemical factors that are normally present in the environment. However, many FQEMs are not commercially available to be used as standards in such studies. FQEMs were therefore synthesized using well-defined processes. They were subsequently analyzed using spectroscopy (UV-vis) and high performance liquid chromatography with mass spectral detection. The antibacterial-like activities of fractionated FQEMs were then assessed in novel bacterial growth inhibition bioassays, and results were compared to those obtained from instrumental analyses.

Materials and Methods

Parent FQs were either exposed to sunlight or were synthesized using defined aerobic microbial (Mycobacterium gilvum or a mixed culture derived from an agricultural soil) fermentation processes. Mixtures of FQEMs derived from photo- and (intracellular) microbial processes were isolated by preparative chromatography and centrifugation techniques, respectively. Mixtures were subsequently fractionated using analytical high-performance thin layer chromatography (HPTLC), and excised analytes were tested in bioautography assays for their antibacterial-like activities. Two bacteria, Escherichia coli (E. coli) and Azospirillum brasilense (A. brasilense) were used as reporter organisms in testing FQ standards and any subtle differences between biologically active FQEMs of ciprofloxacin (CF).

Results and discussion

FQEMs produced in the photo-synthetic process had UV-vis profiles that were indistinguishable from the parent FQs, and yet mass spectral data revealed the presence of N-formylciprofloxacin (FCF). In contrast, the UV-vis profiles of FQEMs synthesized by M. gilvum and a mixed culture of microorganisms had UV-vis profiles that were similar to one another and markedly different to the parent fluoroquinolones. Mass spectral studies confirmed the presence of FCF and N-acetylciprofloxacin in both microbial ferments. In addition, a photo-FQEM (Cp 6), three M. gilvum FQEMs (Cm 5, Cm 8, and Cm 10) and a mixed culture FQEM (Cs 6) of CF and many other FQEMs of CF, norfloxacin (NF), and enrofloxacin (EF) were fractionated using HPTLC, although their identities have yet to be confirmed. Differences between bioautography results were obtained when E. coli or A. brasilense were used as reporter organisms. Parent FQs (CF and EF) and the FQEMs of CF (Cp 6, Cm 8, and Cs 6) displayed antibacterial-like activity when using E. coli as the reporter organism. In contrast, A. brasilense was insensitive to parent CF and sensitive to EF and all tested FQEMs of CF. Results are consistent with photo- and microbial processes modifying CF in different ways, with the latter changing the UV-vis chromophores. It can be inferred that a lack of detection of analytes (especially photo-FQEMs) when using UV-vis does not necessarily indicate an absence of analyte. Additionally, similarities between the UV-vis profiles of FQEMs extracted from the (monoculture) M. gilvum and the mixed culture microbial aerobic ferments are consistent with similar processes operating in both ferments. Results of HPTLC and bioautography studies revealed that mixtures of (photo- and microbial) FQEMs could be fractionated into individual components.

Conclusions

Bioactive FQEMs of ciprofloxacin, as a representative FQ, can be synthesized by photo- and microbial processes, and their detection required the use of both instrumental and bioautography analytical techniques. It is likely that such FQEMs will also be present on agricultural land that has been repeatedly amended with FQ-contaminated biosolids.

Recommendations and perspectives

The use of instrumental analytical techniques alone and especially photometric detection techniques will underestimate antibacterial-like activities of FQEMs. Moreover, the extraction technique(s) and the selected toxicological endpoint(s) require careful consideration when assessing bioactivity. It is therefore recommended that instrumental analytical techniques and several bioautography assays be performed concurrently, and bioautography assays should use a variety of reporter organisms. Two types of bacterial growth bioassays are recommended in any assessment of antibacterial-like activity derived from CF (and possibly from other FQs). A standardized E. coli bioassay should be used as a general screening procedure to facilitate intra- and inter-laboratory exchange of data. Additionally, soil-specific (region-specific) growth inhibition bioassays should be undertaken using several species of endemic soil bacteria. It is likely that the two sets of data will be useful in future risk assessment processes.     

Detection of antibacterial-like activity on a silica surface: fluoroquinolones and their environmental metabolites

Background, scope, and aims

Antibacterial fluoroquinolones (FQs) are third-generation antibiotics that are commonly used as therapeutic treatments of respiratory and urinary tract infections. They are used far less in intensively farmed animal production systems, though their use may be permitted in the veterinary treatments of flocks or in medicated feeds. When used, only a fraction of ingested parent FQ actually reaches the in vivo target site of infection, while the remainder is excreted as the parent FQ and its metabolized products. In many species?? metabolism, enrofloxacin (EF) is converted into ciprofloxacin (CF) while both FQs are classified as parent FQs in human treatments. It is therefore likely that both FQs and their metabolic products will contribute to a common pool of metabolites in biological wastes. Wastes from intensive farming practices are either directly applied to agricultural land without treatment or may be temporarily stored prior to disposal. However, human waste is treated in sewage treatment plants (STPs) where it is converted into biosolids. In the storage or treatment process of STPs, FQs and their in vivo metabolites are further converted into other environmental metabolites (FQEMs) by ex vivo physicochemical processes that act and interact to produce complex mixtures of FQEMs, some of which have antibacterial-like activities. Biosolids are then often applied to agricultural land as a fertilizer amendment where FQs and FQEMs can be further converted into additional FQEMs by soil processes. It is therefore likely that FQ-contaminated biowaste-treated soils will contain complex mixtures of FQEMs, some of which may have antibacterial-like activities that may be expressed on bacteria endemic to the receiving agricultural soil environment. Concern has arisen in the scientific and in the general community that repeated use of FQ-contaminated biowaste as fertilizer amendments of nutrient-impoverished agricultural land may create a selective environment in which FQ-resistant bacteria might grow. The likelihood of this happening will depend, to some extent, on whether bioactive FQEMs are first synthesized from the parent FQs by the action and interaction of in vivo and ex vivo processes producing bioactive FQEMs in biowastes and biosolids. The postulated creation of a selective environment will also depend, in part, on whether such bioactive FQEMs are biologically available to bacteria, which may, in turn, be influenced by soil type, amendment regime, and the persistence of the bioactive FQEMs. Additionally, soil bacteria and soil processes may be affected in different ways or extents by bioactive FQEMs that could possibly act additively or synergistically at ecological targets in these non-target bacteria. This is an important consideration, since, while parent FQs have well-defined ecological targets (DNA gyrase and topoisomerase IV) and modes of bactericidal action, the FQEMs and their possible modes of action on the many different species of soil bacteria is less well studied. It is therefore understandable that there is a lack of conclusive evidence directly attributing biosolid usage to any increase in FQ-resistant bacteria detected in biowaste-amended agricultural soil. However, a lack of evidence may simply imply that a causal relationship between biosolid usage programs and any detection of low levels of FQ-resistant bacteria in soils has yet to be established, rather than an assumption of no relationship whatsoever. Based on results presented in this paper, the precautionary principle should be applied in the usage of FQ-contaminated biosolids as fertilizer amendments of agricultural land. The aim of this research was to test whether any bioactive FQEMs of EF could be synthesized by aerobic fermentation processes using Mycobacterium gilvum (American Tissue Culture Collection) and a mixed culture of microorganisms derived from an agricultural soil. High-performance thin-layer chromatography (HPTLC) and bioautography were tested as screening techniques in the detection and analysis of bioactive FQEMs.

Materials and methods

FQEMs derived from M. gilvum and mixed (soil) culture aerobic ferments were fractionated using preparative HPTLC. A standard strain of Escherichia coli was then used as the reporter organism in a bioautography assay in the detection of bioactive-FQEMs on a mid-section of the HPTLC plate. Plate sections were reassembled, and a photograph was taken under low-intensity ultraviolet (UV) light to reveal regions that contained analytes that had UV chromophores and antibacterial-like activities.

Results and discussion

Many fractionated FQEMs displayed antibacterial-like activity while bound to silica gel HPTLC plates. These results also provide evidence that sufficient quantities of biologically active FQEMs were biologically available from a silica gel surface to prevent the adherent growth of E. coli. Six to seven FQEMs derived from EF using aerobic fermentation processes had antibacterial-like activities, while two FQEMs were also detectable using UV light. Furthermore, similar banding patterns of antibacterial-like activity were observed in both the monoculture (M. gilvum) and mixed culture bioautography assays, indicating that similar processes operated in both aerobic fermentations, either producing similar biologically active FQEMs or biologically active FQEMs that had similar physicochemical properties in both ferments. The simplest explanation for these findings is that the tested agricultural soil also contained mycobacteria that metabolized EF in a similar way to the purchased standard monoculture M. gilvum. Additionally, the marked contrast between the bioautography results and the UV results indicated that the presence of UV chromophores is not a prerequisite for the detection of antibacterial-like activity.

Conclusions

A reliance on spectrophotometric techniques in the detection of bioactive FQEMs in the environment may underestimate component antibacterial-like activity and, possibly, total antibacterial-like activity expressed by EF and its FQEMs. The described bioautography method provides a screening technique with which antibacterial-like activities derived from EF and possibly other FQs can be detected directly on silica gel HPTLC plates.

Recommendations

It is recommended that both bioassay and instrumental analytical techniques be used in any measurement of hazard and risk relating to antibacterial-like activities in the environment that are derived from fluoroquinolone antibiotics and their environmental metabolites.     

Trypsin inhibitor,antioxidant and antimicrobial activities as well as chemical composition of potato sprouts originating from yellow- and colored-fleshed varieties

Abstract

Potato sprouts could be a valuable resource of phytochemicals such as secondary plant metabolites, potential antioxidants and nutritive compounds. In this work, potato sprout extracts of five varieties were examined; they differed in major glycoalkaloid content, trypsin inhibitor activity, total polyphenol content and antioxidant activity, as well as in antimicrobial activity against Gram?+?and G???bacteria, and yeast. Sprouts of colored-fleshed tubers were characterized by higher trypsin inhibitor activity than sprouts of yellow potatoes. The strongest microorganism growth inhibition effect was observed for macerate with sprouts from the purple-fleshed Blaue Annelise variety against B. subtilis, whereas C. albicans yeasts were sensitive to macerates with sprouts from purple-fleshed Blue Congo and yellow-fleshed Vineta potato varieties.     

Laboratory Evaluation of an Aldehyde Scrubber System Specifically for the Detection of Acrolein

Abstract

We demonstrate the use of an aldehyde scrubber system to resolve isobaric aldehyde/alkene interferences in a proton transfer reaction mass spectrometer (PTR-MS) by selectively removing the aldehydes from the gas mixture without loss of quantitative information for the alkene components. The aldehyde scrubber system uses a bisulfite solution, which scrubs carbonyl compounds from the gas stream by forming water-soluble carbonyl bisulfite addition products, and has been evaluated using a synthetic mixture of acrolein and isoprene. Trapping efficiencies of acrolein exceeded 97%, whereas the transmission efficiency of isoprene was better than 92%. Quantification of the PTR-MS response to acrolein was validated through an intercomparison study that included two derivatization methods, dinitrophenylhydrazine (DNPH) and O-(4-cyano-2-ethoxybenzyl)hydroxylamine (CNET), and a spectroscopic method using a quantum cascade laser infrared absorption spectroscopy (QCL) instrument. Finally, using cigarette smoke as a complex matrix, the acrolein content was assessed using the scrubber and compared with direct QCL-based detection.     

Informative Report

Abstract

Chemical composition and particle size data for particulate emissions from stationary sources are required for environmental health effect assessments, air chemistry studies and for air quality modeling investigations such as source apportionment. The Information presented In this paper is directed to those individuals concerned with these environmental Investigations. In this study, particulate emissions from a group of non-ferrous smelters have been physically and chemically characterized. Emission samples were collected at the baghouse outlets from smelter furnaces and at smelter acid plant stacks at three locations; a zinc, a lead, and a copper smelter.

Mass emission rate determinations were made by EPA reference methods. Cascade impactors were used to collect in-stack samples for particle size distribution measurements. Particulate samples for chemical characterization were collected on membrane filters for analysis by X-ray fluorescence spectroscopy. Development of measurement techniques required to determine the elemental composition of the total mass and sized fractions of the emission are discussed. Results of the tests at the three smelters include total mass and elemental emission rates, particle size distribution, and the elemental composition of the total particulate mass and of sized fractions from both the smelter furnaces and acid plants. The results obtained at the copper smelter may not be representative of the emissions at the many copper smelters where reverbatory furnaces have been replaced.     

Residues of pharmaceutical products in recycled organic manure produced from sewage sludge and solid waste from livestock and relationship to their fermentation level

In recent years, sludge generated in sewage treatment plants (STPs) and solid waste from livestock being utilized is useful for circulation of nourishment in farmlands as recycled organic manure (ROM). In this study, we determined the residue levels and patterns of 12 pharmaceutical products generated by human activity in the ROMs produced from human waste sludge (HWS), sewage sludge (SS), cattle manure (CM), poultry manure (PM), swine manure (SM) and horse manure (HM).The kind and number of pharmaceutical products detected in ROMs were different. Fluoroquinolones (FQs) were detected at high levels in HWS and SS samples. In addition, the detection frequency and concentration levels of sulfonamides (SAs) in PM and SM were high. Moreover, high concentrations of chlortetracycline (CTC) were found in only SM. These differences reflect specific adherence adsorption of the pharmaceutical products to different livestock and humans. Moreover, it was found that the concentrations of pharmaceutical products and fermentation levels of ROMs had significant positive correlation (r = 0.41, p = 0.024).When the fermentation test of ROM was conducted in a rotary fermentor in a lab scale test, the residue levels of pharmaceutical products decreased effectively except carbamazepine (CBZ). The rates of decrease were in the case of tetracyclines (TCs): 85-92%, FQs: 81-100%, erythromycine: 67%, SAs: 79-95%, trimethoprim: 86% and CBZ: 37% by 30 d. Pharmaceutical products that can be decomposed by fermentation process at the lowest impact of residual antibiotic activities may therefore be considered as environmentally friendly medicines.     

Ozone Measurements in South Carolina Using Passive Samplers

Abstract

Passive samplers with two different collection substrates were used to obtain an average ozone concentration for 1 month during the summer of 2002 for each South Carolina county. One sampler contained a filter coated with indigo carmine, whose color fades when exposed to ozone. The fading was measured by reflectance spectroscopy. The other sampler contained filters that were coated with nitrite, which is oxidized to nitrate when exposed to ozone. The nitrate was measured by ion chromatography.

Calibration curves were developed for the two methods by comparing color fading from indigo carmine and nitrate ion concentration from the nitrite filter with ambient ozone concentration measured by a co-located reference continuous UV ozone analyzer. These curves were used to calculate integrated ozone concentrations for samplers distributed across South Carolina.

Using the indigo carmine method, the average ozone concentrations ranged from 21 to 64 ppb (average = 46 ± 7.9 ppb, n = 58) across the 46 counties in the state during one summer month of 2002. Concentrations for the same time period from the nitrite-coated filters ranged from 23 to 62 ppb (average = 41 ± 8.1 ppb, n = 58). Also for the same time period, the 23 continuous UV photometric ozone monitors operated by the South Carolina Department of Health and Environmental Control at sites within 10 miles of some of the passive monitors showed ozone concentrations ranging from 28 to 50 ppb (average = 39 ± 6.3 ppb, n = 22).     

Chemical characteristics of chromophoric dissolved organic matter in rainwater

Proton nuclear magnetic resonance (¹H-NMR), UV absorbance and excitation-emission matrix (EEM) fluorescence spectroscopy were used to define the chemical characteristics of chromophoric dissolved organic matter (CDOM) in whole and C₁₈ extracted rainwater. The average total recovery of fluorescence determined from the sum of extract and filtrate fractions relative to the whole was 86% suggesting that 14% of fluorescent CDOM in rainwater is comprised of very hydrophobic material that cannot be eluted from the column. Half the fluorescence of rainwater was recovered in the filtrate fraction which is important because it suggests that 50% of the chromophoric material present in precipitation is relatively hydrophilic. The average spectral slope coefficient was smaller in extracted samples (16.3 ± 9.0 μm^?1) relative to whole samples (18.9 ± 2.8 μm^?1) suggesting that the extracted material contains larger molecular weight material. Approximately one-third of the total dissolved organic carbon (DOC) in rainwater exists in the extract fraction suggesting that a large percentage of the uncharacterized DOC in rainwater can be accounted for by these hydrophobic macromolecular species. The fluorescence of extracted samples is strongly correlated with total NMR integration and is most sensitive to aromatic protons suggesting that molecules in this region are the most important in controlling the optical properties of rainwater. The lower removal efficiency of CDOM in rainwater relative to surface waters or the water-soluble fraction of aerosols during solid phase extraction (SPE) suggests that rainwater contains significantly more hydrophilic chromophoric compounds which are compositionally different than found in these other aquatic matrices.     

不同密度沉水植物腐解过程中水体DOM变化特征

选取白洋淀淀区的泥、水以及晒干的优势沉水植物金鱼藻、轮藻为研究对象,设置6个密度梯度模拟实验,分别于实验进行的50 d和100 d采集水样,运用紫外和荧光光谱技术研究沉水植物腐解阶段水体中溶解性有机质(DOM)的变化。结果显示,同步荧光光谱中,类蛋白峰荧光强度的变化不具规律性,类腐殖质峰荧光强度随密度的增加呈上升趋势,I2/I1的值随着密度的增加或时间的推移均逐渐增大;三维荧光光谱中,随着密度的增加,类富里酸荧光峰A和C的强度逐渐增加,而类色氨酸荧光峰T1的强度变化不大,腐解植物的密度大于3 kg/m3时各组均产生了类海洋腐殖质荧光峰B且强度随密度的增加逐渐增强,C峰的强度与水样中的COD和TP呈显著正相关;紫外光谱测定中,A253/A203的值随着密度的增加或时间的推移而逐渐增大,水体中的芳香族化合物也增多。     

Detectability of phenoxy herbicides by chlorophyll fluorescence

Abstract

Trace amounts of 2,4‐D ‐ which does not cause visible damage in plant ‐ are detectable in plant leaves by chlorophyll fluorescence regeneration in two ways. (I) In illuminated leaves the level of first and second fluorescence peak differ in treated and untreated leaves. (2) By taking buffer solution (pH=8.6) in dark‐adapted leaves under vacuum, the first, second and the other fluorescence decrease levels differ in untreated and 2,4‐D or MCPA treated leaves.     

Investigation of metal ions binding of humic substances using fluorescence emission and synchronous‐scan spectroscopy

Abstract

The binding site interactions of IHSS humic substances, Suwannee River Humic Acid, Suwannee River Fulvic Acid, Nordic Fulvic Acid, and Aldrich Humic Acid with various metals ions and a herbicide, methyl viologen were investigated using fluorescence emission and synchronous‐scan spectroscopy. The metal ions used were, Fe(III), Cr(III), Cr(VI), Pb(II), Cu(II) and Ni(II). Stern‐Volmer constants, K_SV for these quenchers were determined at pH 4 and 8 using an ionic strength of 0.1M. For all four humic substances, and at both pH studied, Fe(III) was found to be the most efficient quencher. Quenching efficiency was found to be 3–10 times higher at pH 8. The bimolecular quenching rate constants were found to exceed the maximum considered for diffusion controlled interactions, and indicate that the fluorophore and quencher are in close physical association. Synchronous‐scan spectra were found to change with pH and provided useful information on binding site interactions between humic substances and these quenchers.     

Coarse Particulate Matter Apportionment around a Steel Smelter Plant

Abstract

The results from a study carried out in the urban area of Genoa, Italy, where a large steel smelter recently shut down are presented. We had the opportunity to sample particulate matter (PM) before and after plant closure and, therefore, to measure the changes in concentration and composition of PM₁₀ (atmospheric PM with aerodynamic diameter <10 µm). Elemental concentrations of Na to Pb were obtained through energy dispersive X-ray fluorescence (ED-XRF), and the contributions of specific sources of PM₁₀ were calculated by positive matrix factorization (PMF). The PM₁₀ average concentration turned out to be surprisingly similar before and after closing of the smelter. Nevertheless, the comparison among data collected in the two periods (plant operating and closed), even with the limited information provided by ED-XRF, allowed us to single out two sources of PM related to the smelter activities, to extract their emission profile, and to quantify the impact of the plant on PM₁₀ levels.