Assessment of aided phytostabilization of copper-contaminated soil by X-ray absorption spectroscopy and chemical extractions

Field plots were established at a timber treatment site to evaluate remediation of Cu contaminated topsoils with aided phytostabilization. Soil containing 2600 mg kg⁻¹ Cu was amended with a combination of 5 wt% compost and 2 wt% iron grit, and vegetated. Sequential extraction was combined with extended X-ray absorption fine structure (EXAFS) spectroscopy to correlate changes in Cu distribution across five fractions with changes in the predominant Cu compounds two years after treatment in parallel treated and untreated field plots. Exchangeable Cu dominated untreated soil, most likely as Cu(II) species non-specifically bound to natural organic matter. The EXAFS spectroscopic results are consistent with the sequential extraction results, which show a major shift in Cu distribution as a result of soil treatment to the fraction bound to poorly crystalline Fe oxyhydroxides forming binuclear inner-sphere complexes.     

Growth, photosynthesis and antioxidant responses of two microalgal species, Chlorella vulgaris and Selenastrum capricornutum, to nonylphenol stress

The effect of nonylphenol (NP) on growth, photochemistry and biochemistry of two green microalgae, Chlorella vulgaris and Selenanstrum capricornutum, and their ability to degrade NP were compared. The 96 h EC₅₀ of C. vulgaris and S. capricornutum were greater than 4.0 and 1.0 mg L⁻¹ NP, respectively, suggesting that the former species was more tolerant to NP. Both microalgae acclimated to NP stress through down-regulating their photosynthetic activities, including antenna size (chlorophyll a content), maximal photochemistry (Fv/Fm) and the light absorbed by PSII (ABS/CS₀), but the dissipation of energy from reaction centres (DI₀/RC) increased with the increase of NP concentrations. In C. vulgaris, the changes of these parameters were more significant than in S. capricornutum and recovered completely after a 96 h exposure. The antioxidant responses, such as GSH content, CAT and POD activities in C. vulgaris increased with the increase of NP concentrations after a 24 h exposure, but these changes disappeared with exposure time and recovered to the control levels after 96 h. In S. capricornutum, although GSH content, CAT and POD activities also increased when exposed to low- to moderate-NP concentrations, these values were significantly reduced at a high concentration (4 mg L⁻¹) even after a 96 h exposure, indicating its antioxidant responses were significantly delayed. It is clear that the more NP-tolerant species, C. vulgaris, acclimated better with a faster recovery of its photosynthetic activity from the NP-induced damage, and exhibited more efficient and rapid responses to NP-induced oxidative stress. C. vulgaris also had a higher NP degradation ability than S. capricornutum.     

Identification of phase II in vivo metabolites of alkyl-anthracenes in rainbow trout (Oncorhynchus mykiss)

Metabolism of xenobiotics is a two-step process that increases the polarity of compounds to facilitate their excretion. In previous work, the major in vitro phase I metabolites of alkyl-anthracenes by rainbow trout (Oncorhynchus mykiss) CYP enzymes were shown to be predominantly ring hydroxylated metabolites. Here, we present the first report on the identification of in vivo phase II metabolites of alkyl-anthracenes in juvenile rainbow trout. Bile was collected from trout injected with individual alkyl-anthracenes with, in some cases, a co-injection of β-naphthoflavone (BNF). Some samples were digested with the β-glucuronidase enzyme to confirm the presence of glucuronide conjugates. The metabolites were separated using a water-acetonitrile gradient on a HPLC system equipped with a C₁₈ column and a UV-diode array detector. Trout with endogenous and BNF-induced enzymes produced the same metabolites, but higher concentrations of metabolites were detected after enzyme induction. Alkyl-anthracenes were metabolized predominantly on the rings as evidenced by the UV spectral analysis. Likewise, mass spectrometry and UV spectral analysis confirmed a predominance of glucuronide conjugates for all systems investigated.     

Validation of photosynthetic-fluorescence parameters as biomarkers for isoproturon toxic effect on alga Scenedesmus obliquus

Photosynthetic-fluorescence parameters were investigated to be used as valid biomarkers of toxicity when alga Scenedesmus obliquus was exposed to isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] effect. Chlorophyll fluorescence induction of algal cells treated with isoproturon showed inactivation of photosystem II (PSII) reaction centers and strong inhibition of PSII electron transport. A linear correlation was found (R2>or=0.861) between the change of cells density affected by isoproturon and the change of effective PSII quantum yield (PhiM'), photochemical quenching (qP) and relative photochemical quenching (qP(rel)) values. The cells density was also linearly dependent (R2=0.838) on the relative unquenched fluorescence parameter (UQF(rel)). Non-linear correlation was found (R2=0.937) only between cells density and the energy transfer efficiency from absorbed light to PSII reaction center (ABS/RC). The order of sensitivity determined by the EC-50% was: UQF(rel)>PhiM'>qP>qP(rel)>ABS/RC. Correlations between cells density and those photosynthetic-fluorescence parameters provide supporting evidence to use them as biomarkers of toxicity for environmental pollutants.     

Use of diffuse reflectance spectrometry in spot test reactions for quantitative determination of cations in water

Diffuse reflectance spectroscopy can be successfully used for the quantitative determination of small amounts of pollutants like metals. The remission function was found to be linearly proportional to the concentration, when we applied the Kubelka–Munk equation. The color reactions of Cu(II), Co(II), and Ni(II) with dithiooxamide, were realised on filter paper. Reaction between Fe(III) and ammonium thiocyanate was realized on filter paper and gelatine matrix. All measurements were accomplished with a laboratory-constructed reflectometer. We have obtained a calibration curve by plotting the optical density of reflectance A_R vs log of the mol l⁻¹ concentration. Limits of detection at the 10⁻⁴ M level were estimated for all the compounds. Linear dynamic range extend over one order of magnitude and shows the potential of device for the quantitative analysis of environmental pollutants.     

Chemical immobilisation of arsenic in contaminated soils using iron(II)sulphate—advantages and pitfalls

Chemical immobilisation of inorganic contaminants by increasing the sorption capacity of soils and/or promoting the formation of sparingly soluble precipitates may be a cost-effective approach to counteract groundwater pollution. This study focuses on the enhanced retention of arsenic in two contaminated soils by addition of solid iron(II)sulphate. Four lab-scale column experiments were performed under unsaturated conditions with subsoil material sampled at a former timber preservation site and a pigment production plant. Arsenic effluent concentrations indicated 89.9 to 99.8% immobilisation in the treated columns. Sequential extractions showed a shift in contaminant binding forms towards the iron(hydr)oxide and residual fractions. Possible immobilisation mechanisms are the precipitation of FeAs phases, the formation of inner sphere complexes, and/or the occlusion of arsenic in newly formed amorphous/crystalline iron oxides. Bromide breakthrough curves point to the fact that the addition of iron(II)sulphate only moderately affects soil hydraulic properties. In contrast to reduced emissions of arsenic, increased seepage water concentrations were observed for other trace elements (e.g., cobalt, nickel, zinc). Mass balances indicate that this effect is primarily related to the temporary pH-drop caused by the oxidation of ferrous iron. The results show that chemical immobilisation using iron(II)sulphate is a promising way to protect groundwater quality at sites contaminated with timber preservation and pigment production remnants. As a prerequisite, optimum amendment levels need to be established and practical/field tests should be accompanied by a monitoring for a broad range of relevant trace elements.     

Prenatal diagnosis of the Hunter syndrome and the introduction of a new fluorimetric enzyme assay

Prenatal diagnosis of the Hunter syndrome (mucopolysaccharidosis type II; MPS II) is preferably achieved by the assay of iduronate-2-sulphate sulphatase (IDS) in uncultured chorionic villi (CV) as this allows early (12th week), rapid (2–3 days) and reliable results. We summarize the results of 174 prenatal analyses in the past 30 years, using various methods such as radiolabelled sulphate incorporation in amniotic fluid (AF) cells, glycosaminoglycan (GAG)-electrophoresis in AF and IDS assay in CV, CV-cells, AF and AF-cells. Twenty-seven fetuses with MPS II were diagnosed after finding clearly abnormal results in pregnancies with a male fetus; very low IDS activity has also been measured in some pregnancies with a (heterozygous) female fetus, emphasizing the need to combine enzyme assay with fetal sex determination. IDS activity has until recently been assessed by a cumbersome radioactive enzyme assay. Here we describe the use of a novel fluorigenic 4-methylumbelliferyl substrate, which allows a sensitive, rapid and convenient assay of IDS activity and reliable early prenatal diagnosis. This novel IDS assay was validated in retrospective analyses of 14 CV, CV-cell, AF and AF-cell samples from affected pregnancies in addition to prospective prenatal diagnosis in eight pregnancies at risk with one MPS II-affected fetus. Copyright © 2002 John Wiley & Sons, Ltd.     

Evidence for coupled iron and nitrate reduction in the surface waters of Jiaozhou Bay

Iron and nitrate (NO₃^?) are dominant physiologically required nutrients for phytoplankton growth, and iron may also play a key role in the marine nitrogen cycle. In this study, we investigated the temporal and spatial distributions of dissolved iron (DFe) and Fe(II) in the surface waters of Jiaozhou Bay (JZB) from April 2 to July 26, 2017. High concentrations of DFe and Fe(II) predominantly occurred in nearshore and estuarine stations and concentrations were generally higher in April and May. The highest DFe concentration was observed along the coast of Hongdao (51.55 nmol/L) in May, while the lowest concentration was observed in the western coastal region (2.88 nmol/L) in April. The highest and lowest Fe(II) concentrations were observed in the Licun estuary (22.42 nmol/L) and outer bay (0.50 nmol/L) in May, respectively. We calculated the proportions of nitrate, nitrite, and ammonium in dissolved inorganic nitrogen (DIN) as well as the ratio of Fe(II) to DFe in all four months. The mean Fe(II)/DFe ratio was 0.48 in April, 0.43 in May, 0.69 in June, and 0.32 in July. The mean ratio of NO₃^? to DIN was 0.78 in April, 0.54 in May, 0.20 in June, and 0.62 in July. NO₃^?/DIN continuously decreased in the first three months, while Fe(II)/DFe remained high, which suggests that the reduction of iron and nitrate occurred simultaneously in the surface waters of JZB.     

Synthesis of a novel ternary HA/Fe-Mn oxides-loaded biochar composite and its application in cadmium(II) and arsenic(V) adsorption

Cadmium (Cd) and arsenic (As) are two of the most toxic elements. However, the chemical behaviors of these two elements are different, making it challenging to utilize a single adsorbent with high adsorption capacity for both Cd(II) and As(V) removal. To solve this problem, we synthesized HA/Fe-Mn oxides-loaded biochar (HFMB), a novel ternary material, to perform this task, wherein scanning electron microscopy (SEM) combined with EDS (SEM-EDS) was used to characterize its morphological and physicochemical properties. The maximum adsorption capacity of HFMB was 67.11?mg/g for Cd(II) and 35.59?mg/g for As(V), which is much higher compared to pristine biochar (11.06?mg/g, 0?mg/g for Cd(II) and As(V), respectively). The adsorption characteristics were investigated by adsorption kinetics and the effects of the ionic strength and pH of solutions. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR) revealed that chelation and deposition were the adsorption mechanisms that bound Cd(II) to HFMB, while ligand exchange was the adsorption mechanism that bound As(V).