International audience

We investigated the occurrence and removal of four benzotriazoles (BTs) (benzotriazole: BT; 5-methyl-benzotriazole: 5-TTri; 5-chloro-benzotriazole: CBT; 5,6-dimethyl-benzotriazole: XTri) and six UV filters (benzophenone-3: BP-3; 3-(4-methylbenzylidene)camphor: 4-MBC; octyl 4-methoxycinnamate: OMC; 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chloro benzotriazole: UV-326; 2-(2′-Hydroxy-5′-octylphenyl)-benzotriazole: UV-329; octocrylene: OC) in a full scale municipal wastewater treatment in South Australia. BT, 5-TTri and BP-3 were found as the dominant compounds detected in the wastewater samples with average concentrations up to 5706 ± 928 ng/L, 6758 ± 1438 ng/L and 2086 ± 1027 ng/L in influent, and up to 2439 ± 233 ng/L, 610 ± 237 ng/L and 153 ± 121 ng/L in effluent, respectively. In the biosolid, 4-MBC and OC were found with the highest concentrations of 962 ± 135 ng/g and 465 ± 65 ng/g, respectively. Sorption onto sludge played a dominant role in the removal for UV filters, especially for 4-MBC, UV-326 and OC, which accounted for 54%–92% of influent loads, while biological degradation played a significant role for the other compounds.

The rootless duckweed Wolffia globosa can accumulate and tolerate relatively large amounts of arsenic (As); however, the underlying mechanisms were unknown. W. globosa was exposed to different concentrations of arsenate with or without l-buthionine sulphoximine (BSO), a specific inhibitor of γ-glutamylcysteine synthetase. Free thiol compounds and As(III)–thiol complexes were identified and quantified using HPLC – high resolution ICP-MS – accurate mass ESI-MS. Without BSO, 74% of the As accumulated in the duckweed was complexed with phytochelatins (PCs), with As(III)–PC₄ and As(III)–PC₃ being the main species. BSO was taken up by the duckweed and partly deaminated. The BSO treatment completely suppressed the synthesis of PCs and the formation of As(III)–PC complexes, and also inhibited the reduction of arsenate to arsenite. BSO markedly decreased both As accumulation and As tolerance in W. globosa. The results demonstrate an important role of PCs in detoxifying As and enabling As accumulation in W. globosa.

We used XAD-resin based passive air samplers (PAS) to measure atmospheric levels of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) at five ombrotrophic bogs in Eastern Canada. The aims of our study were to investigate the influence of local roads on contaminant levels in the bogs, to derive the regional pattern of atmospheric concentrations, and to assess the uncertainties of the method. Expanded uncertainties based on the duplicate PAS deployed at 24 sites were good for the PAHs, while the deployment period of approx. 100 days was too short to yield acceptable uncertainties for PCBs. The regional PAH distribution was in good agreement with the calculated source proximity of the sampled bogs. We conclude that XAD-resin based PAS deployed for comparatively short periods are well suited for measuring atmospheric concentrations of volatile PAHs, while in remote regions longer deployment is necessary for less volatile PAHs and for PCBs.

We investigated changes of bacterial abundance and biodiversity during bioremediation experiments carried out on oxic and anoxic marine harbor sediments contaminated with hydrocarbons. Oxic sediments, supplied with inorganic nutrients, were incubated in aerobic conditions at 20 °C and 35 °C for 30 days, whereas anoxic sediments, amended with organic substrates, were incubated in anaerobic conditions at the same temperatures for 60 days. Results reported here indicate that temperature exerted the main effect on bacterial abundance, diversity and assemblage composition. At higher temperature bacterial diversity and evenness increased significantly in aerobic conditions, whilst decreased in anaerobic conditions. In both aerobic and anaerobic conditions, biodegradation efficiencies of hydrocarbons were significantly and positively related with bacterial richness and evenness. Overall results presented here suggest that bioremediation strategies, which can sustain high levels of bacterial diversity rather than the selection of specific taxa, may significantly increase the efficiency of hydrocarbon degradation in contaminated marine sediments.

Sediment cores from 12 Chinese lakes were analyzed to investigate the historical inputs of polybrominated diphenyl ethers (PBDEs) and decabromodiphenylethane (DBDPE) during the past few decades. Concentrations of ΣPBDE₁ (sum of tri- to hepta-BDEs), ΣPBDE₂ (sum of nona- to deca-BDEs) and DBDPE in the surface sediments were 0.02–0.29 ng g⁻¹, 0.46–46.6 ng g⁻¹ and 1.02–3.64 ng g⁻¹, respectively. The temporal trends of PBDEs and DBDPE followed a general increase from the bottom to the surface. The calculated fluxes for ΣPBDE₁, ΣPBDE₂ and DBDPE were 0.001–0.09, 0.03–4.24, and 0.05–0.31 ng cm⁻² yr⁻¹, and the inventories were 0.09–7.86, 0.91–461, and 3.83–24.6 ng cm⁻², respectively. The urbanization and industrialization are highly related to the contamination of PBDEs and DBDPE in sediments. The DBDPE input in recent years was still lower than ΣPBDE₂ but the temporal trends indicated that the contamination would increase with the increasing usage of DBDPE in the future.

This study provides a combined dataset on N loss pathways and fluxes from sloping cropland in the purple soil area, southwestern China. A lysimeter experiment was conducted to quantify nitrate leaching (May 2004–May 2010) and N₂O emission (May 2009–May 2010) losses. Nitrate leaching was the dominant N loss pathway and annual leaching fluxes ranged from 19.2 to 53.4 kg N ha⁻¹, with significant differences between individual observation years (P < 0.05). Direct N₂O emissions due to N fertilizer use were 1.72 ± 0.34 kg N ha⁻¹ yr⁻¹, which corresponds to an emission factor of 0.58 ± 0.12%. However, indirect N₂O emissions caused by nitrate leaching and surface runoff N losses, may contribute another 0.15–0.42 kg N ha⁻¹ yr⁻¹. Our study shows that nitrate leaching lowered direct N₂O emissions, highlighting the importance for a better understanding of the tradeoff between direct and indirect N₂O emissions for the development of meaningful N₂O emission strategies.

The Effects of silicon (Si) on the distribution of cadmium (Cd) compartmentation in root tips of Kandelia obovata (S., L.) Yong were investigated by pot experiments. Cd concentrations in the apoplastic saps and symplastic fractions of the root tips of K. obovata seedlings were decreased at both Si-supplied treatments. Si addition reduced the concentrations of BaCl₂₋extractable cell-wall-Cd in root tips, but increased the concentrations of Na₃citrate-extractable cell-wall-Cd and HCl-extractable cell-wall-Cd in root tips. The total root-tip contents of Cd were mainly distributed in the apoplast and most of the Cd in the apoplast was bound to the cell wall. Our experiment found that Si increased the ratio of apoplast Cd (>87.08%) and reduced the ratio of Cd in the symplast (<12.92%). This suggested that Si enhanced binding of Cd to the cell walls and restricted the apoplastic transport of Cd.

Dialysis equilibrium system was applied to investigate the roles of Cu(II) and Mg(II) on DOM-ofloxacin (OFL) interaction. The binding behavior of both cations and OFL were studied. The introduction of Cu(II) increased DOM-OFL interaction, while Mg(II) decreased DOM-OFL binding. Cu(II) binding to DOM was also increased by OFL, while Mg(II) binding was decreased by OFL. The change in OFL binding amount in the absence and presence of cations (ΔCb) was calculated and compared with cation binding (Cb ᵐ). ΔCb/Cb ᵐ was in the range of 1–3 for Cu(II) depending on the applied Cu concentration. Two ternary complexes of DOM-OFL-Cu and DOM-Cu-OFL were proposed. For Mg(II), ΔCb/Cb ᵐ was around −1 at Mg(II) concentrations lower than 1 mM, but decreased up to −5 with increasing Mg(II) concentration. The competitive effect of Mg(II) to OFL was thus proposed. FTIR spectra were collected for mechanistic discussion.

Chlorinated paraffins (CPs) were found in the biodegradable fraction of source separated waste from Uppsala, Sweden. We identified and quantified the CPs by multivariate evaluation of gas chromatography-electron capture detection chromatograms. Using principal component analyses (PCA) we identified different types of CP-formulations and also obtain quantitative data. PCA yielded better identifications of individual CP-formulations than visual comparison of chromatograms. Partial least squares regression gave good calibration curves of the standards, but did not work for the waste samples. No source of CPs could be identified in the waste collection chain, and as the waste samples seemed to contain at least two different CP-formulations the source was probably to be found in the waste material itself. The method was used to determine CPs in additional environmental samples, demonstrating that multivariate methods may be developed into a powerful tool for identification and quantification of complex mixture.