[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED [Axe_IRSTEA]TED-EPURE | International audience | We develop an original solid respirometric method to measure the biodegradation rates of COD and ammonium at different depths of a Vertical Flow Constructed Wetland (VFCW). The method is developed for a matrix operated under unsaturated conditions. The oxygen demand is measured versus time in a gas passing through a reactor containing a mixture of an organic matrix mixed with a bulking agent (wood). For the measurement of the nitrification rate, a solution of ammonia and hydrogenocarbonates is spread on the sample. We ran 15 experiments on different matrices with variable organic matter contents (sludge, VFCW gravels and sand). Within this paper we present the overall methodology, the factors that allow improving the accuracy (number of duplicates, blank, sample volume, bulking agent volume, gas flow, etc.) and the nitrification rates that were obtained.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED [Axe_IRSTEA]TED-EPURE | International audience | Thus, choosing to plant local macrophytes species in CWs can be considered as an asset for the development of CWs, since it can be a part of global development projects which integrate cultural, social and economic characteristics. But, because of the ability of some macrophytes to accumulate toxic elements, human utilisation of CWs macrophytes has to be managed considering health damage potentiality. Spontaneous macrophytes diversity has to be appreciated for its key-role in the development of CWs in developing countries, not only from an ecological point of view, but also from cultural, social, sanitary and economic views.

The nature of soil organic matter (SOM) functional groups associated with sorption processes was determined by correlating partitioning coefficients with solid-state 13C nuclear magnetic resonance (NMR) and diffuse reflectance mid-infrared (DRIFT) spectral features using partial least squares (PLS) regression analysis. Partitioning sorption coefficients for n-pentadecane (n-C15) were determined for three alternative models: the Langmuir model, the dual distributed reactive domain model (DRDM) and the Freundlich model, where the latter was found to be the most appropriate. NMR-derived constitutional descriptors did not correlate with Freundlich model parameters. By contrast, PLS analysis revealed the most likely nature of the functional groups in SOM associated with n-C15 sorption coefficients (KF) to be aromatic, possibly porous soil char, rather than aliphatic organic components for the presently investigated soils. High PLS cross-validation correlation suggested that the model was robust for the purpose of characterising the functional group chemistry important for n-C15 sorption. NMR/IR spectroscopy and chemometrics reveal the aromatic fraction of soil organic matter being responsible for alkane sorption.

In an extensive environmental study, field samples, including soil, water, rice, vegetable, fish, human hair and urine, were collected at an abandoned tungsten mine in Shantou City, southern China. Results showed that arsenic (As) concentration in agricultural soils ranged from 3.5 to 935 mg kg−1 with the mean value of 129 mg kg−1. In addition, As concentration reached up to 325 μg L−1 in the groundwater, and the maximum As concentration in local food were 1.09, 2.38 and 0.60 mg kg−1 for brown rice, vegetable and fish samples, respectively, suggesting the local water resource and food have been severely contaminated with As. Health impact monitoring data revealed that As concentrations in hair and urine samples were up to 2.92 mg kg−1 and 164 μg L−1, respectively, indicating a potential health risk among the local residents. Effective measurements should be implemented to protect the local community from the As contamination in the environment. It is the first report on arsenic contamination and potential health risk implications at abandoned Lianhuashan tungsten mine.

Perfluorinated compounds (PFCs) were detected in sediment core samples collected in Tokyo Bay to reveal their time trends. The core sample deposited during 1950s–2004 was divided into two- to three-year intervals and the concentrations of 24 types of PFCs were determined. Perfluorooctane sulfonate (PFOS) decreased gradually from the early 1990s and its precursor decreased rapidly in the late 1990s, whereas perfluorooctanoic acid (PFOA) increased rapidly. The observed trends were regarded as a reflection of the shift from perfluorooctyl sulfonyl fluoride (PFOSF)-based products to telomer-based products after the phaseout of PFOSF-based products in 2001. The branched isomers of perfluoroundecanoic acid (PFUnDA) and perfluorotridecanoic acid (PFTrDA) were detected in the sample with its ratio of linear-isomer/branched-isomer concentrations decreasing. In this study, we revealed that the sediment core can serve as a tool for reconstructing the past pollution trend of PFCs and can provide interesting evidence concerning their environmental dynamics and time trend. This study reports the time trends of the concentrations of 24 species of PFCs, including FTCA, FTUCA and FOSAA, in a sediment core of Tokyo Bay, Japan. Keywords: Perfluorinated compounds

Numerous experiments have demonstrated reductions in the yields of cereal crops due to tropospheric O3, with losses of up to 25%. However, the only British econometric study on O3 impacts on winter wheat yields, found that a 10% increase in AOT40 would decrease yields by only 0.23%. An attempt is made here to reconcile these observations by developing AOT40 maps for Great Britain and matching levels with a large number of standardised trial plot wheat yields from many sites over a 13-year period. Panel estimates (repeated measures on the same plots with time) show a 0.54% decrease in yields and it is hypothesised that plant breeders may have inadvertently selected for O3 tolerance in wheat. Some support for this is provided by fumigations of cultivars of differing introduction dates. A case is made for the use of econometric as well as experimental studies in prediction of air pollution induced crop loss.

The metabolite 2,6-dichlorobenzamide (BAM) is a frequent groundwater pollutant produced during degradation of the herbicide 2,6-dichlorobenzonitrile (dichlobenile). Spatial variability of BAM mineralisation is uncharacterized in surface soil, however, and factors controlling the heterogeneity remain unknown. We addressed these issues by sample-to-sample comparisons of BAM mineralisation rates and a range of soil characteristics at spatial scales ranging from meters to centimetres. For mineralisation assays nano-molar concentrations of labelled BAM were added to determine mineralisation rates under realistic conditions. We found a significant variability of BAM mineralisation which increased with decreasing spatial scale. BAM mineralisation rates were correlated to the density of BAM-degrading bacteria but not to water content, TOC, NH4+, NO3−, or pH. The genus Aminobacter, which contains the only BAM degraders known, was detected in MPN samples of BAM degraders by a specific PCR assay targeting the 16S rRNA gene, confirming a role of Aminobacter in BAM mineralisation. Density of degrader bacteria is the main factor in BAM mineralisation when considering realistic low concentrations in soil.