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Microbial communities are a central component of trophic dynamics and biogeochemical processes on coastal systems, since most of the processes in sediments are mediated by microorganisms and carried out by enzymes. Microorganisms play a key role in decomposition processes in salt marsh sediments, although the significance of microbial dynamics is largely unexplored. A culture-dependent (Ecoplate) and a culture-independent (extracellular enzyme activity [EEA]) approaches were evaluated in their ability to distinguish the catabolic potential among sediments from Tagus estuary salt marshes with different proximities to anthropogenic sources. Ecoplate was used to analyse the salt marsh community-level physiological profiles (CLPPs). Results were expressed as the net area under the curve for each of the 31 response wells over a 3-day incubation period in two sediment horizons. The catabolic profiles for salt marsh samples were analysed by Principal Component Analysis (PCA) and hierarchic clustering methods. EEA was analysed by fluorescein diacetate (FDA) hydrolysis in two sediment horizons. The FDA is catalysed by extracellular enzymes, i.e. esterases, lipases and partially by proteases. Results were expressed as μg g−1d wt h−1. In this study the CLPP and EEA data were not generally correlated. In Corroios salt marsh only in surface sediments higher net areas corresponded to higher extracellular enzymatic activity, and in Alcochete deep sediments lower net areas corresponded to lower enzymatic activity. Although EEA profiles more directly reflect the inherent activity of resident community in each salt marsh sample, the CLPP profiles provide better assessments of diversity.

Soil heavy metal pollution poses a serious threat to ecological environment safety and human health through the food chain. Using efficient and safe measures to clean up heavy metals in soils is a necessary and urgent task. Phytoremediation is known as a relatively safe method, which also has the defect of slow repair efficiency. We explored the effects of alternating current (AC) electric field (0 and 0.5 V cm−1) and fertilization (no fertilization, inorganic fertilizer, organic fertilizer, and organic–inorganic combination) on phytoremediation efficiency to heavy metal cadmium (Cd) contaminated soil in an interplanting system of willow (Salix SPP) and Sedum (Sedum Alfredii Hance). The results showed that the most substantial promotion effect was observed under AC electric field applied with organic fertilizer. The plant shoot Cd accumulation was increased by 98.99% compared to the control (no AC electric field and no fertilization). The promotion effect was weaker when applied the electric field, compound fertilizer + organic fertilizer, and organic fertilizer, which increased by 44.98%, 43.30%, and 36.97%, respectively, compare to the control. The single application of fertilizer or electric field had a significant effect on the phytoremediation efficiency. There was a significant interaction between AC electric field and fertilizer application. The strongest improvement in plant Cd uptake was observed when the AC electric field was combined with Chinese milk vetch organic fertilizer. These results will provide a very important reference for the application of willow and S. Alfredii in soil Cd remediation.

Agricultural soil contamination by heavy metals is a serious environmental problem, and developing feasible and effective soil remediation technologies is a top priority. In this study, a microbial consortium dominated by sulfur-oxidizing bacteria was constructed to enhance Cd and Zn removal from contaminated soil. During treatments, changes in pH and Eh and the removal efficiencies of Cd and Zn were investigated. Fractionation of Cd and Zn, soil fertility indexes, and the microbial community were also analyzed before and after bioleaching. The results show that under the same conditions, the best removal efficiencies for Cd and Zn were observed in the bioleaching group compared to other treatments (acid leaching and sulfur treatment). When the sulfur concentration was 15 g/kg, 79.3% of Cd and 45.2% of Zn were removed, while undissolved Cd and Zn mainly remained in the residual fraction, accounting for 93.1% and 84.0% of their remaining totals, respectively. After remediation, the bioleaching group showed a reduction of the total phosphorus and available potassium, with a decrease of 53.7% and 41.2%, respectively. Furthermore, the exogenous microbes in the inoculum had a competitive advantage and became the dominant population at the end of the run. The consortium obtained in this study can effectively improve remediation processing and be used to remediate heavy metal-contaminated soil.

Engineering and dredging strategies to manage sediment, along with river-scouring, can reveal older sediments. These present a unique opportunity to assess past sources of phosphorus (P) inputs into river sediments. We used the sediment concentrations of P, lead (Pb) and 206/207Pb isotopes to produce ‘first-order’ estimates of the source (diffuse agricultural or sewage treatment) of phosphorus. Sediment cores (n = 30) were collected from the length of the non-tidal River Nene, a lowland river in eastern England. Cores were analysed for sediment elemental concentrations and Pb isotopes. Principal component analysis and linear regression modelling were used to assess the relationships between P, Pb and Pb isotopes. Monte-Carlo simulations and boot-strapping were undertaken to estimate, with 95% confidence intervals, the source of P in these sediments. Analysis of the relationships between PTotal, PbTotal and 206/207Pb isotope ratios suggested that sediments were deposited largely prior to the phasing out of tetra-ethyl Pb (PbBHT) from petrol. Regression models showed positive correlations between PTotal and PbTotal (R2 = 0.85). Principal component analysis suggested a strong sewage treatment signal for Pb and P enrichment. In the rural upper three water bodies, little sewage treatment work (STW)-derived P was found in the sediment, a consequence of limited STW input and greater sediment transport. In the more urbanised water bodies 4–6, ‘first-order estimates’ of STW P suggest that median concentrations were 30–40% of PTotal. The strong relationships between Pb and P concentrations in river water provided the opportunity to use 206/207Pb isotope ratios to calculate ‘first-order’ estimates of the proportion of P released from STWs in the historical sediment. Understanding the sources of historical sediment P can be used to assess the success of current sediment management strategies and to base further mitigation measures. Results suggest that whilst much recent sediment P is removed, the legacy sediment remains to contribute P to the water body. Thus, options regarding the practical removal of these sediments and the extent to which this would improve water P status need to be assessed and balanced against options such as further decreasing soil P or STW P stripping.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in soils pose a severe threat to the soil ecosystem and human health. Soil aggregates play a critical role in the migration and transformation of pollutants. In this study, soil with different properties (Fluvisol and Planosol) spiked with PFOA/PFOS were incubated for 90 days, and then divided into five particle size fractions by wet sieving with low loss. The concentrations of PFOA and PFOS in soils and fractions were extracted using ultrasound-assisted extraction method with methanol as an extractant. The PFOA and PFOS were analyzed using high-performance liquid chromatography-tandem mass spectrometry (HPLC–MS/MS). The results showed that the ability of the soil aggregates to carry PFOA and PFOS initially decreased and then increased with decreasing particle sizes. Moreover, organic matter was the main factor influencing the PFOA and PFOS distribution in the soil aggregates, whereas soil types did not affect the accumulation capacity of PFOA and PFOS on soil particles. The macroaggregates (2000–250 µm) showed the highest accumulation capacity of PFOA and PFOS, suggesting high load of PFOA and PFOS. Additionally, the microaggregates (< 15 µm) played a dominant role in the PFOA and PFOS distribution due to the high proportion of this fraction in soil samples (51.73 ~ 62.47%). Significantly bipolar immigrations of PFOA and PFOS into macroaggregates and microaggregates in soils were observed. This phenomenon can be explained by the fact that the particulate organic carbon (POM) can sorb the PFOA and PFOS in the macroaggregates, while the presence of SOC (highly humified) may increase the PFOA and PFOS contents in the microaggregates.

The effects of check dams used in restoration projects have been discussed in a number of papers in recent years. This paper studies the effectiveness of retaining sediments from check dams constructed in the badlands restoration site of Tórtoles, located in the Corneja River basin (Spain), using a new topographical method. In order to assess the sediment-retaining capacity of the check dams, we measured the volume of sediment trapped by 15 of the 123 check dams built in 1965. We carried out a detailed topographical survey using a Total Station, with an accuracy of ±1 cm, to measure cross sections of the sediment trapped by each check dam. The results were then compared with those of two simplified methods which consider the volume of retained sediment as a simple geometric figure. According to our results, 258 m3 of sediment has been retained by the check dams. These results show a significant discrepancy between the topographical method and the two other methods, whose values are consistently lower (14 to 20 %). According to our survey, the mean value for the volume of sediment retained by each check dam is 17.23 m3, versus 13.86 and 14.74 m3 when applying the other methods. Although there is a strong correlation between the volume of retained sediment computed by the topographical method and the other two methods (r 2 from 0.96 to 0.94), the differences between them increase with the increasing size of the check dams. Therefore, total differences are expected to be more significant with larger check dams. The erosion rates, calculated on the basis of the retained sediment in the Tórtoles check dams, are 16–21 % lower when using the simpler methods. The bed slopes of the streams were reduced 12.44 % because of the presence of the check dams. After having completed a more detailed topographical survey of the sediment trapped in the check dams, our results are more likely to estimate erosion rates and sediment yield correctly, thus leading to a better understanding of the effects of check dams on badlands restoration.

The possibility of using higher plants to extract mercury from contaminated sites is dependent on both the concentration of Hg and its bioavailability. To increase the solubility of Hg in soil, some chemical compounds can be used. The aim of this study was to evaluate the effectiveness of Hg soil cleaning with the use of Lepidium sativum L. and sodium thiosulphate, as well as the leach ability of Hg from soil after phytoextraction. The experiment was conducted on soil artificially polluted by Hg, wherein sodium thiosulphate was tested as a phytoextraction promoter. The L. sativum L. plants were used for phytoextraction. The leaching of Hg was assessed by determination of Hg concentration in water extracts. All determinations of Hg in soil, plant and water extracts were analysed by CV-AAS method after acid mineralization. The result of the study showed that L. sativum L. accumulated Hg from contaminated soil mostly in belowground tissues. Even less than 8 % of Hg was translocated to the shoots of L. sativum L. Application of thiosulphate increased the total Hg accumulation over 238–272 %, depending on both the Hg and thiosulphate concentrations in soil. After thiosulphate treatment, translocation of Hg to shoots of L. sativum L. increased even 10 times relative to unassisted process. Thiosulphate did not negatively affect plant biomass; however, the increased leaching of Hg after thiosulphate treatment was observed. Lepidium sativum L. showed the potential of a non-hyperaccumulating plant that can be used during phytoextraction of Hg-contaminated soils in controlled conditions. Thiosulphate promoted the phytoextraction process by increasing the total Hg accumulation by whole plant and translocation of Hg to shoots of L. sativum L. Thiosulphate-mobilized Hg in soil, which increased the Hg leaching. This constitutes the limitation of applying the technique in the field due to risk of Hg transferring to deeper layers of soil or water. Applying the technique in the field should be preceded by further investigations.