This paper relates to the 1st studies conducted in France on Vertical Flow Constructed Wetlands [VFCWs]. This process was originally designed by Käte Seidel according to her previous research done in Krefeld (Germany) the so-called Max Planck Institute Process [MPIP]. Based on measurements campaigns done successively in Saint Bohaire and Pont-Rémy, it was clearly established that the vertical flow 1st stage filters were significantly more efficient than the horizontal ones. This acknowledgement of success was positively used to design a treatment plant in Gensac la Pallue, still in operation after 23 years, with the special feature that the VFCW are fed with raw sewage. This attribute was then spread to the design of French VFCW systems. The main reasons which explain why representatives of small communities are so enthusiastic about feeding with raw sewage are presented. The state of the art of French VFCWs is detailed and scientific arguments which nowadays lead to new fields of application and a better understanding of small scale processes which occurs in these filters are also suggested.

Coastal wetland soils serve as a great C sink or source, which highly depends on soil carbon flux affected by complex hydrology in relation to salinity. We conducted a field experiment to investigate soil respiration of three coastal wetlands with different land covers (BL: bare land; SS: Suaeda salsa; PL: Phragmites australis) from May to October in 2012 and 2013 under three groundwater tables (deeper, medium, and shallower water tables) in the Yellow River Delta of China, and to characterize the spatial and temporal changes and the primary environmental drivers of soil respiration in coastal wetlands. Our results showed that the elevated groundwater table decreased soil CO₂ emissions, and the soil respiration rates at each groundwater table exhibited seasonal and diurnal dynamics, where significant differences were observed among coastal wetlands with different groundwater tables (p < 0.05), with the average CO₂ emission of 146.52 ± 13.66 μmol m⁻²s⁻¹ for deeper water table wetlands, 105.09 ± 13.48 μmol m⁻²s⁻¹ for medium water table wetlands and 54.32 ± 10.02 μmol m⁻²s⁻¹ for shallower water table wetlands. Compared with bare land and Suaeda salsa wetlands, higher soil respiration was observed in Phragmites australis wetlands. Generally, soil respiration was greatly affected by salinity and soil water content. There were significant correlations between groundwater tables, electrical conductivity and soil respiration (p < 0.05), indicating that soil respiration in coastal wetlands was limited by electrical conductivity and groundwater tables and soil C sink might be improved by regulating water and salt conditions. We have also observed that soil respiration and temperature showed an exponential relationship on a seasonal scale. Taking into consideration the changes in groundwater tables and salinity that might be caused by sea level rise in the context of global warming, we emphasize the importance of groundwater level and salinity in the carbon cycle process of estuarine wetlands in the future.

Sediment serves as a sink for metals, thus it is critical to assess its contamination and associated risk. A typical riparian wetland close to a Zn-smelting operation in karst areas in southwest China was investigated. Sediment and reed plant (Phragmites australis) samples from wet and dry seasons were analyzed for total As, Cu, and Zn concentrations. Metal pollution in the sediment was assessed based on geoaccumulation index (Igₑₒ). Further, metals in the sediment were fractionated into exchangeable, water and acid-soluble, reducible, oxidizable, and residual fractions based on the BCR sequential extraction. The results showed that the As, Cu, and Zn concentrations in the sediment were significantly higher than the background values (740–4081, 96–228, and 869–3331 vs. 10, 22, and 70 mg kg⁻¹). With the Igₑₒ being 10–17, the data indicate that the sediment was highly-polluted. While total As, Cu and Zn in the sediment increased from dry to wet season, their available concentrations decreased except Cu. With 62–94% of As, Cu, and Zn being in the residual fraction, metal availability in the sediment was low based on fractionation data. The data are consistent with low metal uptake by reed as their concentration ratios in plant roots to the sediment were 0.01–0.32. The results suggest that the riparian sediment was highly-polluted with As, Cu and Zn, but showing low metal availability and limited plant uptake.

Clonal plants can share information and resources among connected ramets (asexual individuals). Such clonal integration can promote ramet growth, which may further influence soil microbial communities in the rooting zone. Crude oil contamination can negatively affect plant growth and alter soil microbial community composition. However, we still know little about how clonal integration affects soil microbial communities, especially under crude oil contamination. In a coastal wetland, ramets of the rhizomatous plant Phragmites australis in circular plots (60 cm in diameter) were subjected to 0, 5 and 10 mm depth of crude oil, and the rhizomes at the edge of the plots were either severed (preventing clonal integration) or left intact (allowing clonal integration). After three years of treatment, we analysed in each plot soil physiochemical properties and soil microbial community composition. The alpha-diversity of the soil microbial communities did not differ between intact and severed plots, but was overall lower in 10-mm than in 0-mm and 5-mm oil plots. Considering all three oil treatments together, soil microbial community dissimilarity (beta-diversity) was positively correlated with soil property distance in both severed and intact plots. Considering the three oil treatments separately, this pattern was also observed in 10-mm oil plots, but not in 0-mm or 5-mm oil plots. The soil microbial community composition was more sensitive to the oil addition than to the clonal integration. Moreover, the relative abundance of the nitrogen-cycling bacterial taxa was lower in intact than in severed plots, and that of the oil-degrading bacterial taxa increased with increasing oil-addition levels. Our results indicate that clonal integration and oil contamination can influence soil microbial communities independently through changing the relative abundance of the component bacteria taxa, which has important implications for ecosystem functions of the soil food web mediated by clonal plants.

Dissolved organic carbon (DOC) plays diverse roles in carbon biogeochemical cycles. Here, we explored the link between DOC and pCO2 using high-performance size-exclusion chromatography (HPSEC) with UV254 detection and excitation emission matrix (EEM) fluorescence spectroscopy to determine the molecular weight distribution (MW) and the spectral characteristics of DOC, respectively. The relationship between DOC and pCO2 was investigated in the Poyang Lake wetlands and their adjacent aquatic systems. The results indicated significant spatial variation in the DOC concentrations, MW distributions, and pCO2. The DOC concentration was higher in the wetlands than in the rivers and lakes. pCO2 was high in wetlands in which the dominant vegetation was Phragmites australis, whereas it was low in wetlands in which Carex tristachya was the dominant species. DOC was divided into five fractions according to MW, as follows: super-low MW (SLMW, <1 kDa); low MW (LMW, 1–2.5 kDa); intermediate MW (IMW, 2.5–3.5 kDa); high MW (HMW, 3.5–6 kDa); and super-high MW (SMW, > 40 kDa). Rivers contained high proportions of HMW and extremely low amounts of SLMW, whereas wetlands had relatively high proportions of SLMW. The proportion of SMW (SMWp) was particularly high in wetlands. We found that pCO2 significantly positively correlated with the proportion of IMW, and significantly negatively correlated with SMWp. These data improve our understanding of the MW of bioavailable DOC and its conversion to CO2. The present results demonstrate that both the content and characteristics of DOC significantly affect pCO2. pCO2 and DOC must be studied further to help understanding the role of the wetland on the regional CO2 budget.

Intra-specific variability of root biomass production (RP) of six rooted macrophytes, i.e. Juncus effusus, Phragmites australis, Schoenoplectus lacustris, Typha latifolia, Phalaris arundinacea, and Iris pseudacorus grown from clones, in response to Cu exposure was investigated. Root biomass production varied widely for all these macrophytes in control conditions (0.08 μM) according to the sampling site. Root biomass production of T. latifolia and I. pseudacorus in the 2.5–25 μM Cu range depended on the sampling location but not on the Cu dose in the growth medium. For P. australis, J. effusus, S. lacustris, and P. arundinacea, an intra-specific variability of RP depending on both the sampling location and the Cu-dose was evidenced. This intra-specific variability of RP depending on the sampling location and of Cu-tolerance for these last four species suggests that Cu constitutive tolerance for all rooted macrophytes is not a species-wide trait but it exhibits variability for some species.

Nitrous oxide (N₂O) emissions from Phragmites australis (reed) – dominated zones in Baiyangdian Lake, the largest shallow lake of Northern China, were investigated under different hydrological conditions with mesocosm experiments during the growing season of reeds. The daily and monthly N₂O emissions were positively correlated with air temperature and the variation of aboveground biomass of reeds (p < 0.05), respectively. The N₂O emissions from reeds were about 45.8–52.8% of that from the sediments. In terms of the effect of hydrological conditions, N₂O emissions from the aquatic-terrestrial ecotone were 9.4–26.1% higher than the submerged zone, inferring that the variation of water level would increase N₂O emissions. The annual N₂O emission from Baiyangdian Lake was estimated to be about 114.2 t. This study suggested that N₂O emissions from shallow lakes might be accelerated by the climate change as it has increased air temperature and changed precipitation, causing the variation of water level.

As one of the most cost-effective and sustainable methods for contaminants' removal, sequestration and/or detoxification, phytoremediation has already captured comprehensive attention worldwide. Nevertheless, the accurate effects of various spatial pattern in enhancing phytoremediation efficiency is not yet clear, especially for the polluted mining areas. This study designed nine planting patterns (monocropping, double intercropping and triple intercropping) of three indigenous plant species (Setaria viridis (L.), Echinochloa crus-galli (L.) and Phragmites australis (Cav.) Trin. ex Steud.) to further explore the effects of plants spatial pattern on phytoremediation efficiency. Considering the uncertainties of the residual contaminants' concentration (RCC) caused by soil anisotropy, permeability and land types, the interval transformation was introduced into the plant uptake model to simulate the remediation efficiency. Then multi-criteria decision analysis (MCDA) were applied to optimal the planting patterns, with the help of criteria of (a) the amount of heavy metal absorption; (b) the concentration of residual contaminant in soil; (c) root tolerance of heavy metals; (d) the total investment cost. Results showed that (1) the highest concentrations of Zn, Cd, and Pb of the polluted area were 7320.02, 14.30, 1650.51 mg kg⁻¹ (2) During the 180 days simulation, the highest RMSE of residue trace metals in soil are 3.02(Zn), 2.67(Pb), 2.89(Cd), respectively. (3) The result of IMCDA shows that the planting patterns of Setaria viridis, Echinochloa crus-galli and Phragmites australis in alternative a9 (269 mg kg⁻¹ year⁻¹) had the highest absorption rate of heavy metals compared with a7 (235 mg kg⁻¹ year⁻¹) and a2 (240 mg kg⁻¹ year⁻¹). After 20 years of remediation, the simulated RCC in a9 is far below the national standard, and the root toxicity is 0.12 (EC ≤ EC₂₀). In general, the optimal alternative derived from interval residual contaminant concentration can effectively express the dynamic of contaminant distribution and then can be effectively employed to evaluate the sustainable remediation methods.

Although the Korean tidal flats in the Yellow Sea have been highlighted as a typical macrotidal system, so far, there have been no measurements of the sediment erodibility and critical shear stress for erosion (τce). Using the Gust erosion microcosm system, a series of field experiments has been conducted in the Ganghwa tidal flat to investigate quantitatively the effects of biogenic materials on the erodibility of intertidal cohesive sediments. Four representative sediment cores with different surficial conditions were analyzed to estimate the τce and eroded mass. Results show that τce of the “free” sediment bed not covered by any biogenic material on the Ganghwa tidal flat was in the range of 0.1–0.2 Pa, whereas the sediment bed partially covered by vegetation (Phragmites communis) or fecal pellets had enhanced τce up to 0.45–0.6 Pa. The physical presence of vegetation or fecal pellets contributed to protection of the sediment bed by blocking the turbulent energy. An inverse relationship between the organic matter included in the eroded mass and the applied shear stress was observed. This suggests that the organic matter enriched in a near-bed fluff layer is highly erodible, and the organic matter within the underlying sediment layer becomes depleted and less erodible with depth. Our study underlines the role of biogenic material in stabilizing the benthic sediment bed in the intertidal zone.

Phragmites australis shows potential for the phytoremediation of chlorinated chemicals. Also there has been some attempt to determine the phytotoxic effects of organochlorines (OC). This study reports for lindane (HCH), monochlorobenzene (MCB), 1,4-dichlorobenzene (DCB) and 1,2,4-trichlorobenzene (TCB), a no-observed-effect-concentration (NOEC₇d) that was 1000–300,000 times higher than environmental concentrations. Nevertheless, the combined OC mixture (NOEC₇d level of each congener) induced a synergistic toxic effect, causing a severe drop (70%) in chlorophyll concentration. The mixture 0.2mgL⁻¹ MCB+0.2mgL⁻¹ DCB+2.5mgL⁻¹ TCB+0.175mgL⁻¹ HCH, that was 15 times more concentrated than environmental OC mixture, did not cause phytotoxicity during 21 days. Antioxidant enzymes were affected immediately after the start of exposure (3 days), but the plants showed no signs of stress thereafter. These data suggest that environmental OC mixtures do not pose a significant risk to P. australis.