Salt marsh plants are colonising wastes from a steel plant deposited on the Coina River Banks posing a potential contamination risk to the Tagus estuary ecosystem. The objectives of this study were to assess the uptake, accumulation and translocation of hazardous elements/nutrients in three spontaneous halophytic species, to evaluate the capacity of Tamarix africana to stabilise a contaminated salt marsh soil, and to evaluate the ecotoxicity of the pore water and elutriates from phytostabilised soils.
Materials and methodsThe work comprises the following: fieldwork collection of soil samples from Coina River (an affluent of Tagus River) bank landfill, estuarine water and spontaneous plants (Aster tripolium, Halimione portulacoides and Sarcocornia sp.), and greenhouse studies (microcosm assay) with T. africana growing in one landfill salt marsh soil, for 97 days, and watered with estuarine water. Soils were analysed for pH, EC, Corganic, NPK, iron and manganese oxides. Soils total (acid digestion) elemental concentrations were determined by ICP/INAA. Estuarine waters, plants roots and shoots (acid digestion), soils available fraction (diluted organic acids extraction-RHIZO or pore water), and salts collected from the T. africana leaves surface were analysed for metals/metalloids (ICP-MS). Ecotoxicity assays were performed in T. africana soil elutriates and pore waters using Artemia franciscana and Brachionus plicatillis.
Results and discussionSoils were contaminated, containing high total concentrations of arsenic, cadmium, chromium, copper, lead and zinc. However, their concentrations in the available fraction were <4 % of the total. The estuarine waters were contaminated with cadmium, but negligible ecotoxicological effect was observed. The spontaneous plants had significant uptake of the above elements, being mostly stored in the roots. Elemental concentrations in the shoots were within the normal range for plants. These species are not hazardous elements accumulators. Tamarix africana was well adapted to the contaminated saline soils, stored the contaminants in the roots, and had small concentrations of hazardous elements in the shoots. Excretion of hazardous elements by the salt glands was also observed. Elutriates from soils with and without plant did not show ecotoxicity.
ConclusionsThe salt marsh species play an important role in the stabilisation of the soils in natural conditions. Tamarix africana showed potential for phytostabilisation of saline-contaminated soils. The low translocation of the elements from roots to shoots and/or active excretion of the elements by the salt glands was a tolerance mechanism in T. africana.
相似文献Natural sepiolite (SP) has proven effective on the in-situ immobilization remediation of Cd-contaminated soils. But the practical remediation effect may largely influenced by water management and the application of organic manure. The effects of chicken manure (CM) on SP-amended soils were investigated under normal and saturated water conditions using a pot experiment with Brassica campestris L.
Materials and methodsCd-contaminated paddy soils were amended with CM, SP, and CM?+?SP with no amendment as control. The amount of sepiolite was 0.5% (w/w, the same below) either in SP or CM?+?SP amended soils, while the amount of CM was 0.5, 1.0, and 2.0% in CM and CM?+?SP-amended soils. The plant metal contents, fresh weight, and soluble sugar content of plant edible parts were measured on harvest. Soil Cd was extracted by diethylenetriaminepentaacetic acid (DTPA) and HCl to estimate the mobility of heavy metal. Soil pH and dissolved organic matter (DOM) of rhizosphere soil were determined. The electronegative charges of soils were also measured using the zeta potential.
Results and discussionThe application of CM and increasing soil moisture on SP-amended soil increased plant growth to a greater extent than the application of SP alone. The application of CM along with the increase of soil moisture decreased Cd uptake and translocation in plants grown on SP-amended soil compared to the application of SP alone. Cd content of edible plant parts reached a minimum of 0.24 mg kg?1 with the application of 2.0% CM on SP-amended soils under water-saturated conditions, which was approximately 50% lower than the Cd concentration found when applying SP alone.
ConclusionsThe results of this study suggest that the application of sepiolite on Cd contaminated soil can effectively reduce Cd uptake by B. campestris L., and the addition of CM combined with effective water management also appears to further reduce Cd absorption and accumulation.
相似文献Chelate-assisted phytoremediation with biodegradable chelates has been considered to be a promising technique to enhance phytoremediation efficiency, while little information is available on phytostabilization. This study aims to assess NTA-assisted phytostabilization of Pb-contaminated soils by Athyrium wardii (Hook.).
Materials and methodsA pot experiment was carried out to investigate the effects of different application days (1, 3, 5, 7, 10, 14, 21) of nitrilotriacetic acid (NTA) on plant growth, Pb accumulation, and Pb availability in rhizosphere soils of A. wardii grown in soils contaminated with low (200 mg kg?1) and high (800 mg kg?1) concentrations of Pb.
Results and discussionWith the application of NTA, better growth for A. wardii was observed when treated with NTA for 5–14 days for both low and high Pb soils, suggesting potential harvest time. Pb concentrations and Pb accumulation in underground parts of A. wardii grown in low and high Pb soils increased with increasing application time of NTA generally. Similar changes were also found for bioaccumulation coefficients (BCFs) of A. wardii. The greatest remediation factors (RFs) for underground parts and whole plant of A. wardii were observed for NTA application time of 7 and 5 days for low and high Pb soils, suggesting the greatest remediation efficiency. Furthermore, plant growth, BCF, and RF of A. wardii grown in low Pb-contaminated soils were greater than those grown in high Pb-contaminated soils. Pb availability in rhizosphere soils of A. wardii grown in low Pb soils was lower than those in high Pb-contaminated soils.
ConclusionsIt seems to be the optimum for A. wardii to phytostabilize slightly Pb-contaminated soils with the application of NTA for 7 days as taking plant growth, Pb remediation efficiency, and environmental risk into consideration.
相似文献As natural zeolites have been widely used as cost-effective adsorbents for plant nutrients and heavy metals in sediments, it is worthwhile to verify the potential of natural zeolites for mixed-contaminant stabilization including hydrophobic organic contaminants (HOCs). The effectiveness of natural zeolite amendment in sediment on reducing the bioaccumulation of sediment-associated HOCs in V. philippinaram (Cb) was assessed. Then, the role of sediment pore water freely dissolved HOCs (Cfree) in Cb prediction was further identified and modeled.
Materials and methodsIn this study, a bioavailability-based assessment of the HOC-stabilization efficacy of natural zeolites in maricultural sediments was performed using equilibrium passive sampling. V. philippinaram was adopted as a biological indicator for HOC bioaccumulation. Polydimethylsiloxane (PDMS) was used as a passive sampler for monitoring the concentration of the Cfree. The assumption that Cfree is a central mediator driving the bioaccumulation process of HOCs from the bulk sediment to the exposed organisms was validated by correlating the reductions in Cb and Cfree of the sediments amended with natural zeolites. Subsequently, a model based on this assumption was built and verified for the bioavailability-based assessment of the stabilization efficacy of natural zeolite amendment on sediment-associated HOCs.
Results and discussionThe results showed the bioaccumulations of four kinds of HOCs (including polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers, pyrethroids, and organochlorine pesticides) in V. philippinaram were reduced by 7.3–38% after the natural zeolite amendment (10% dry weight in sediments), and the Cfree values measured with PDMS were reduced proportionally. It supported the assumption that Cfree is a central mediator driving the bioaccumulation process of HOCs. Kow of HOCs and two properties of sediment were found to be significantly correlated with the reductions of the Cfree values. Based on these findings, a model to predict the Cb values of PAHs and PBDEs in V. philippinaram was built. The model was then verified by a significant correlation between the predicted and measured values of Cb.
ConclusionsThe potential of natural zeolites for the stabilization of mixed-contaminants in sediments, including HOCs, was proved as notable reductions of Cb and Cfree of HOCs in the sediments amended by natural zeolite were observed. The results also suggested PDMS is a promising tool for predicting the bioaccumulation of sediment-associated HOCs in V. philippinaram and further for assessing the stabilization efficacy of natural zeolites in maricultural sediments. Modifying natural zeolites to further improve the effectiveness of HOC stabilization is warranted.
相似文献The mobility of arsenic (As) in soils is fundamentally affected by the clay mineral fraction and its composition. Diphenylarsinic acid (DPAA) is an organoarsenic contaminant derived from chemical warfare agents. Understanding how DPAA interacts with soil clay mineral fractions will enhance understanding of the mobility and transformation of DPAA in the soil-water environment. The objective of this study was to investigate the speciation and sorption structure of DPAA in the clay mineral fractions.
Materials and methodsTwelve soils were collected from nine Chinese cities which known as chemical weapons burial sites and artificially contaminated with DPAA. A sequential extraction procedure (SEP) was employed to elucidate the speciation of DPAA in the clay mineral fractions of soils. Pearson’s correlation analysis was used to derive the relationship between DPAA sorption and the selected physicochemical properties of the clay mineral fractions. Extended X-ray absorption fine structure (EXAFS) LIII-edge As was measured using the beamline BL14W1 at Shanghai Synchrotron Radiation Facility (SSRF) to identify the coordination environment of DPAA in clay mineral fractions.
Results and discussionThe SEP results showed that DPAA predominantly existed as specifically fraction (18.3–52.8%). A considerable amount of DPAA was also released from non-specifically fraction (8.2–46.7%) and the dissolution of amorphous, poorly crystalline, and well-crystallized Fe/Al (hydr)oxides (20.1–46.2%). A combination of Pearson’s correlation analysis and SEP study demonstrated that amorphous and poorly crystalline Fe (hydr)oxides contributed most to DPAA sorption in the clay mineral fractions of soils. The EXAFS results further demonstrated that DPAA formed inner-sphere complexes on Fe (hydr)oxides, with As-Fe distances of 3.18–3.25 Å. It is likely that the steric hindrance caused by phenyl substitution and hence the instability of DPAA/Fe complexes explain why a substantial amount of DPAA presented as weakly bound forms.
ConclusionsDPAA in clay mineral fractions predominantly existed as specifically, amorphous, poorly crystalline, and crystallized Fe/Al (hydr)oxides associated fractions. Amorphous/poorly crystalline Fe rather than total Fe contributed more to DPAA sorption and DPAA formed inner-sphere complexes on Fe (hydr)oxides.
相似文献Potentially toxic element (PTE) concentrations in mine-degraded soil and their bioaccumulation in food crops is a public health concern worldwide. The current study investigates the influence of organic geo-sorbents including biochar (B), farmyard manure (FYM), and peat moss (PTM) on PTE in chromite mine-degraded soil and their subsequent effects on spinach biomass, PTE uptake, average dietary intake (ADI), and health risk (HRI) associated with PTE via spinach consumption.
Materials and methodsChromite mine-degraded soil samples were collected from different mining sites in Kohistan region. Pot experiments were carried out in the greenhouse environment. The selected geo-sorbents (B, FYM and PTM) were mixed at application rates of 1%, 2%, and 5%. Contaminated soil without geo-sorbents (control treatment) was also included in each batch of the experiments. Local FYM and PTM were used in this experiment, while B was provided by the Institute of Urban Environment (CAS) Xiamen, China. The total carbon (C), total nitrogen (N), and total sulfur (S) contents in mine-degraded soil and organic geo-sorbents were measured using a macro-elementor (VarioMax CNS, Germany). Total (acid digestion) and bioavailable PTE (As, Cd, Cr, Ni, Zn, and Pb) concentrations in mine-degraded soil and spinach were determined using inductive coupled plasma mass spectrophotometer (ICP-MS 7500 CX, Agilent Technologies, USA).
Results and discussionThe addition of organic geo-sorbents effectively immobilized the PTE concentrations in mine-degraded soil, and increased the major nutrient contents and thereby reduced the bioaccumulation of PTE (Cr, As, Ni, Cd, Zn, and Pb) in spinach. Consequently, B2, B5, FYM2, FYM5, PTM2, and PTM5 amendments significantly (p?<?0.001) increased the biomass, whereas the B1, FYM1, and PTM1 addition showed no significant increase in spinach biomass as compared to the control treatment. The results showed that all the organic geo-sorbents had significantly (p?<?0.001) reduced the As uptake in spinach, while B2, B5, FYM2, FYM5, and PTM5 significantly (p?<?0.001) decreased PTE bioaccumulation as compared to the control treatment.
ConclusionsThe highest application rate (5%) showed the best result in increasing the spinach growth and biomass as well as reducing the PTE mobility in soil, and their bioaccumulation in spinach, as compared to 1% and 2% application rates and also with the control treatment. Furthermore, the average dietary intake (ADI) of PTE and health risk indices (HRIs) reduced via spinach consumption for both the children and adults, due to the addition of selected organic geo-sorbents used for soil amendments.
相似文献In contaminated streams, understanding the role of streambank and streambed source contributions is essential to developing robust remedial solutions. However, identifying relationships can be difficult because of the lack of identifying signatures in source and receptor pools. East Fork Poplar Creek (EFPC) in Oak Ridge, TN, USA received historical industrial releases of mercury that contaminated streambank soils and sediments. Here, we determined relationships between the contaminated streambank soils and sand-sized streambed sediments.
Materials and methodsField surveys revealed the spatial trends of the concentrations of inorganic total mercury (Hg) and methyl mercury (MeHg), Hg lability as inferred by sequential extraction, particle size distribution, and total organic carbon. Statistical tests were applied to determine relationships between streambank soil and streambed sediment properties.
Results and discussionConcentrations of Hg in streambank soils in the upper reaches averaged 206 mg kg?1 (all as dry weight) (n?=?457), and 13 mg kg?1 in lower reaches (n?=?321), while sand-sized streambed sediments were approximately 16 mg kg?1 (n?=?57). Two areas of much higher Hg and MeHg concentrations in streambank soils were identified and related to localized higher Hg concentrations in the streambed sediments; however, most of the streambank soils have similar Hg concentrations to the streambed sediments. The molar ratio of Hg to organic carbon, correlation between MeHg and Hg, and particle size distributions suggested similarity between the streambank soils and the fine sand-sized fraction (125–250 μm) collected from the streambed sediments. Mercury in the fine sand-sized streambed sediments, however, was more labile than Hg in the streambank soils, suggesting an in-stream environment that altered the geochemistry of sediment-bound Hg.
ConclusionsThis study revealed major source areas of Hg in streambank soils, identified possible depositional locations in streambed sediments, and highlighted potential differences in the stability of Hg bound to streambank soils and sediments. This work will guide future remedial decision making in EFPC and will aid other researchers in identifying source–sink linkages in contaminated fluvial systems.
相似文献Characterization of tannery sludge (TS) for its plausible use in amelioration and phytoremediation of heavy metal rich TS treated soil by growing economically important plants (Ricinus communis, Brassica juncea and Nerium oleander).
Materials and methodsTreatments were prepared by amalgamation of TS (0, 5, 10, 20, 30, 50, 75, 100 %) with garden soil (GS). All treatments were analysed for chemical properties, total and DTPA (Diethylene triamine pentaacetic acid) extractable heavy metals (Cr, Pb, Cu, and Mn). Seed germination experiment was conducted; unvarying saplings were selected and planted in concerned pots and allowed to grow for 90 days in green house. At harvest, plant samples were washed with distilled water and used for determination of growth parameters (biomass of root, shoot and total biomass on dry weight basis) and metal accumulation in different parts of the plant. Translocation factor (TF) and bioconcentration factor (BCF) have been calculated to check the phytostabilization capability of studied plants.
Results and discussionApplication of TS in fixed quantity as an amendment resulted in significant improvements of GS characteristics (alkaline pH with high electrical conductivity, organic carbon, available NPK and heavy metals) and in treatments. DTPA extractable heavy metal concentrations were found very low and total heavy metal concentrations were also found under allowable range in control and treated soil (T-I to T-VI). The maximum seed germination percentage, plant growth, biomass production for all plant species were observed in T-III treatment (20 % TS + 80 % GS) with majority of the metal accumulation in underground part (BCF >1) and meagre translocation in aerial part (TF <1). From T-IV to T-VII treatment, accumulation of heavy metals in plant parts has generally increased; however, biomass has been tremendously decreased.
ConclusionsTS was found rich in NPK content with significant concentration of heavy metals. Pot growth experiment suggested amelioration of GS with specific quantity of 20 % TS can tremendously enhance the plant growth, help in the utilization of TS and can act as a substitute of synthetic fertilizer. Majority of the metals was accumulated in root part (BCF >1) and meagre translocation (TF <1) in aerial part, concludes R. communis and B. juncea could be suitable plant species to be grown in heavy metal rich TS treated soil, vis-à-vis for phytostabilization of heavy metals. In addition, these oil yielding and medicinal plants can also be used for phytoremediation of moderately contaminated tannery soils.
相似文献Fine sediment accumulates upstream of hydroelectric dams. To ensure that dams can operate properly, part of the sediment has to be dredged and land managed. In parallel, using topsoil from agricultural parcels for urban greening or land restoration is currently controversial because arable surface areas are decreasing. An alternative idea for protecting these natural resources consists in reusing fine dredged sediment to construct multifunctional soils. This agronomic use is only possible if sediment can provide acceptable physical and chemical properties for plant growth.
Materials and methodsFour dredged sediments with contrasted initial agronomic properties and one control soil were mixed or not with green waste compost (40% v/v) and used to construct triplicate 30-cm depth soils in lysimetric containers (1.11?×?0.71 m). The 30 constructed soils were exposed to the in situ conditions and sown with ryegrass (Lolium perenne). The evolution of soil chemical and physical properties and plant development were studied every 6 months for 18 months.
Results and discussionAbove- and below-ground biomass production of the constructed soils contrasted according to the sediment properties and to compost addition. A statistical approach identified eight soil parameters linked to biomass production. Among these parameters, soil structure, quantified from aggregate stability, played a fundamental role. A focus on physical properties confirmed that some sediments were only partially adapted to ryegrass support. Compost addition improved sediment physical properties over time, but caused temporary N deficiency during the first months after installation which limited shoot biomass production. Exogenous plant species developed on the constructed Technosols, especially on the soils where the lack of structure and N deficiency had the strongest effect.
ConclusionsAll sediments were suitable for plant growth over the 18 months of the study. A few soil properties emerged as markers of the fertility of sediment-made Technosols. Among them, the soil structure was one of the most determining parameters. It can be assessed by measuring aggregate stability, macroporosity, the crustability index, and bulk density, while available nutrients (N, P, K) and pH seem sufficient to assess chemical fertility. The balance between the properties of the sediment-made Technosols and the needs of the plants seems to be an essential lever for the establishment of functional soil-plant systems for urban greening or for ecological restoration.
相似文献Phosphorus (P) and potassium (K) are two important essential nutrient elements for plant growth and development but their availability is often limited in calcareous soils. The objective of this study was to determine the effects of applying microbial inoculants (MI, containing effective strains of Bacillus megaterium and Bacillus mucilaginous) on the availability of P and K, plant growth, and the bacterial community in calcareous soil.
Materials and methodsA greenhouse experiment was conducted to explore the effects of the addition of MI (control: without MI addition; treatment: with MI addition at the rate of 60 L ha?1) on the concentrations of P and K in soil and plant, soil bacterial community diversity and composition, and chili pepper (Capsicum annuum L.) growth.
Results and discussionThe results showed that MI inoculation significantly increased the fruit yields by 28.5% (p?<?0.01), available P and K in the rhizosphere soil by 32.1% and 28.1% (p?<?0.05), and P and K accumulation in the whole plants by 40.9% and 40.2%, respectively (p?<?0.05). Moreover, high-throughput sequencing revealed that Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, and Gemmatimonadetes were the dominant phyla of soil bacteria. MI application did not significantly impact the diversity and composition of soil bacterial communities, but increased relative abundances of bacterial genera Flavobacterium responsible for promoting root development across growing stages (p?<?0.05), and changed the soil bacterial community structure associated closely with soil properties of available P, K, and pH in soil.
ConclusionsThe application of MI improved the bioavailability of P and K and plant growth due to its impact on the soil bacterial community structure.
相似文献Plant growth-promoting rhizobacteria (PGPRs) synthesizes and exports phytohormones which are called plant growth regulators (PGRs). These PGRs may play a regulatory role in plant growth and development. PGRs are organic substances that influence physiological processes of plants at extremely low concentrations. The objective of this study was to find out whether three PGRs, cytokinins, ethephon, and chlorocholine, have a stimulatory or inhibitory effect on the activity of native proteases in soil.
Materials and methodsA revised methodology was used to determine soil protease activity, where TRIS-HCl buffer was replaced with demineralized water. This is described as native protease activity as its activity is not affected by chemicals. The aim was to approximate the protease response to cytokinins in the native soil environment. The native soil proteolytic activity was determined spectrophotometrically.
Results and discussionThe present paper shows that cytokinin, ethephon, and chlorocholine chloride negatively affect the native proteolytic activity of forest soils with the exceptions of the organic and organomineral horizons of European beech (Fagus sylvatica L.) on a rendzic Leptosol. In addition, 6-benzylaminopurine stimulates the native proteolytic activity of the organic horizon of pedunculate oak (Quercus robur L.). A negative effect of cytokinins on the soil proteolytic activity can decrease the rate of organic matter decomposition. The results provide soil biochemists with an insight into the roles of rhizospheric substances on soil microbial activity.
ConclusionsThis work has shown that cytokinins and PGRs inhibit the activity of native soil proteases in most of the studied forest sites. Results describe the effect of rhizospheric compounds on the activity of soil microorganisms, with potentially significant implications for the nitrogen cycle in forest soils.
相似文献We studied the profitable phytoremediation method with commercial chrysanthemum (Chrysanthemum indicum L.) in order to remediate the soils contaminated with heavy metals and generate economy income from the contaminated sites.
Materials and methodsA field experiment was carried out to remediate the contaminated soil through growing the commercial chrysanthemum plants in a farmland polluted with heavy metals of Cd and Zn due to application of creek sediments in the western suburb of Shanghai, Southeast China, since June 2013.
Results and discussionAfter the consecutive 3 years of phytoremediation, Cd and Zn contents in the soil were reduced by 78.1% and 28.4%, respectively. We also found that the rice grain growing on the 3-year phytoremediated soil met the requirements of dietary safety, so did the vegetable growing on the 5-year phytoremediated soil.
ConclusionsGrowing chrysanthemum plants as a method of phytoremediation can not only remove a large amount of toxic heavy metals from the contaminated soil but also be highly profitable from the sales of chrysanthemum flowers.
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