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Salts are an important factor in the formation and evolution of soils, and their classification. Saline wetlands are permanently or frequently flooded environments, which normally causes the development of halohydromorphic soils and halophytic vegetation. The aim of this work was to study the genesis of halohydromorphic soils in a saline wetland in San Luis (Argentina). The area studied was the depression called "Bajo Las Saladas", located at 33° 37' South latitude and 65° 25' West longitude, with an area of 120.7 ha. The physiognomic types of vegetation in different sub-landscapes were delimited. Descriptions of the soils and depth to the water table were carried out in the monitoring plots located in each physiognomic type. The horizons were sampled, analyzed and the soils were classified. In the flat sector, soils of the halophilic bush were classified as typic Haplustolls. In the saline depression sublandscape, the physiognomic type Halophilic bush (dominated by Atriplex spp.) occupies the less saline soils, with higher pH and deeper water table, and the soils were typic Ustorthents or typic Epiaquents. In the more humid and saline areas there are patches of creeping halophilic bush (dominated by Sarcocornia neei), open meadows of Distichlis spicata, dense meadows of D. spicata and in the areas with greater flooding and anoxia, free of vegetation saline beaches. Those soils were classified as typic Epiaquents showing different distribution of horizons, some with glei horizons. Several factors intervene jointly in the genesis of these soils, such as water table depth, salinity, micro-relief, texture, and degree and duration of flooding. [ABSTRACT FROM AUTHOR]

To mitigate excess of nitrate-N (NO 3 −-N) derived from agricultural activity, constructed wetlands (CWs) are created to simulate natural removal mechanisms. Irrigated agricultural drainage water is commonly characterized by an organic carbon/nitrogen (C/N) imbalance, thus, C limitation constrains heterotrophic denitrification, the main biotic process implicated in NO 3 −-N removal in wetlands. We studied a pilot plant with three series (169 m2) of hybrid CWs over the first two years of functioning to examine: i) the effect of adding different C-rich substrates (natural soil vs. biochar) to gravel on NO 3 −-N removal in a subsurface flow (Phase I), ii) the role of a second phase with a horizontal surface flow (Phase II) as a source of dissolved organic C (DOC), and its effect in a consecutive horizontal subsurface flow (Phase III) on NO 3 −-N removal, and iii) the contribution of each phase to global NO 3 −-N removal. Our results showed that the addition of a C-rich substrate to gravel had a positive effect on NO 3 −-N removal in Phase I, with mean efficiencies of 40% and 17% for soil and biochar addition, respectively, compared to only gravel (0.75%). In Phase II, the algae growth turned into a DOC concentration increase, but it did not enhance NO 3 −-N removal in Phase III. In series with C-rich substrate addition, the largest contribution to NO 3 −-N removal was found in Phase I. However, in series with only gravel, Phase II was the most effective on NO 3 −-N removal. Contribution of Phase III to NO 3 −-N removal was almost negligible. [Display omitted] • Gravel was not a suitable substrate to treat C/N imbalanced agricultural water. • Both soil and biochar addition to gravel increased NO 3 −-N removal from water. • A HSSF CW with a gravel + soil mix was the most effective design for NO 3 −-N removal. • Inclusion of a HSF phase in a hybrid CW increased DOC availability by algae growth. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the response of salt marshes to pulses of PO 4 3- -enriched water, with and without the presence of Phragmites australis . A one-year mesocosms experiment was performed in simulated soil profiles (fine-textured surface layers and sandy subsurface layers) from a coastal salt marsh of the Mar Menor lagoon under alternating flooding-drying conditions with eutrophic water, under low (1.95 mg L −1 P-PO 4 3- ) and high (19.5 mg L −1 P-PO 4 3- ) P load, and with the presence/absence of Phragmites . The PO 4 3- concentrations in soil porewater and drainage water were regularly measured, and P accumulated in soils (including a fractionation procedure) and plants (roots, rhizomes, stems and leaves) were analyzed. The experimental mesocosms were highly effective in the removal of P from the eutrophic flooding water (>90% reduction of the P added to the system both in the soil pore water and drainage water), regardless of the nutrient load, the season of the year and the presence/absence of Phragmites . The soil was the main sink of the P added to the system, while Phragmites had a minor role in P removal. The biomass of Phragmites accumulated ∼27% of the P added with the flooding water in the treatment with water of low P load while ∼12% of P in that of high P load; the rhizomes were the organs that contributed the most (∼67–72% of the total P retained by the plants). Ca/Mg compounds were the main contributors to the retention of P in the soil compartment, especially in the fine-textured surface soil layers (∼34–53% of the total P in the soil was present in this fraction). Phragmites favored the retention of P onto metal oxides (∼12% increase of the P retained in the metal oxides fraction in the treatment with water of high P load). Hence, the use of constructed wetlands to ameliorate the negative impacts of P-enriched waters in the Mar Menor lagoon and similar areas is recommended. We propose the incorporation of fine-textured carbonated materials, with high content of Ca/Mg compounds, and the use of Phragmites to favor the retention of P by these systems. [ABSTRACT FROM AUTHOR]

Urban organic waste materials may find a potential use as amendments in agricultural or environmental fields. However, before being applied in field practices, urban organic wastes must meet some environmental and legal requirements. The objective of this work was to assess the metal (Cd, Cu, Mn, Pb and Zn) extractability in two amended degraded semiarid soils (a former agricultural soil and a mine tailings soil) employing an urban organic waste amendment. A seven-steps sequential extraction procedure was performed in order to determine the changes in metal (Cd, Cu, Mn, Pb and Zn) fractionation, after two weeks and after eight months of soil incubation in pots. The urban organic waste increased organic carbon at both soils but it did not affected pH. At both soils, the addition of the amendment increased the labile fractions of metals, especially Cu (up to 13% of total content). In the amended agricultural soil the incubation favoured the fractions associated to Mn oxides (for Mn and Zn) and organic matter (for Cu), probably due to the higher buffer capacity of the soil (pH ~ 8, high CaCO 3 , loam texture). In the amended mine tailings soil, with lower buffer capacity (pH ~ 7, low CaCO 3 , loamy sand texture), there was a redistribution into more labile fractions associated to carbonates (Mn, Pb and Zn). In low buffer capacity soils, such as the case of the mine tailings soil, the changes generated by the mineralisation of the organic matter may alter heavy metal fractionation promoting the increase of carbonate bound fractions, which could be easily mobilisable. The assessment of the long-term dynamics of organic matter mineralisation and its relation to metal geochemistry is necessary to provide a safe employment of this urban organic waste for restoring degraded soils. [ABSTRACT FROM AUTHOR]

Wetlands are highly effective systems mitigating the negative effects of N excess, but at the same time they contribute to global warming through greenhouse gas emissions. The present study aimed to ascertain the role of Phragmites australis in N transformations in eutrophic semiarid salt marshes, under low (NO 3 − = 20 mg L − 1 ) and high (NO 3 − = 200 mg L − 1 ) nutrient level and alternating flooding-drying phases. Methacrylate mesocosms were filled with a saline soil, with and without the presence of Phragmites stands, and subjected to alternating flooding-drying conditions. For 44 weeks the soil Eh was regularly monitored at two depths and the N-NO 3 − and N-NH 4 + concentration in pore water and drainage and the potential soil N-N 2 O emissions to the atmosphere measured. In the surface soil layers, more than the 80% of N-NO 3 − was removed regardless of the presence of plants, the nutrient level and the season of the year. Denitrification seemed to be the main responsible of this. In the subsurface soil layers N-NO 3 − decreased an average of ~ 83% in presence of Phragmites and ~ 32% without plants during the warmer period (soil temp. ~ 15 to ~ 30 °C), but the effectiveness was reduced to < 10% during the colder period (soil temp. ~ 10 to ~ 15 °C). The N-NH 4 + increased during the flooding phases (reaching 2–6 mg L − 1 ), and the results indicated that it was nitrified during the following drying phases. A tendency to lower potential soil N-N 2 O emissions was observed in treatments with Phragmites during drying phases, pointing that the plants absorbed this newly formed N-NO 3 − . Hence, we propose harvesting Phragmites stands at the beginning of the summer, but after a lag time to permit N-NO 3 − absorption by plants before the complete drying of the watercourses. [ABSTRACT FROM AUTHOR]

Highlights: [•] CaCl2-extractable Cu was correlated with dissolved organic carbon. [•] CaCl2-extractable concentrations did not correlate with metal uptake. [•] Pinus halepensis may be used to phytostabilise metal polluted soils in semiarid areas. [•] Areas surrounding tailings were impacted by high metal(loid) concentrations. [Copyright &y& Elsevier]

Abstract: The aim of this study was to evaluate the effects of liming and vegetation on the dynamic of Fe in eutrophic wetland soils affected by mine wastes, under different flooding regimes. Simulated soil profiles were constructed with two types of wastes (pH∼3.1 and ∼6.4) collected from polluted salt marshes and four treatments were assayed: without liming+without plant, without liming+with plant, with liming+without plant, and with liming+with plant. The plant species was the halophyte Sarcocornia fruticosa. Three horizons were differentiated in the profiles: A horizons (never underwater), C1 (alternating flooding–drying conditions), and C2 (always underwater). The pH, Eh, salinity, and the concentrations of DOC and soluble Fe were measured regularly at each horizon for 18 weeks. Liming decreased Fe solubility, mainly in the acidic waste (maximum average concentrations ∼18mgL−1 without liming and ∼6mgL−1 with liming). However, liming also facilitated a drop in Eh, increasing soluble Fe content. Plant rhizosphere re-distributed this Fe, which was accumulated in the upper horizons of the treatments with liming+with plant, particularly in the acidic waste (average concentrations ∼10mgL−1 in the A horizon and ∼5mgL−1 in the C1 and C2 horizons). Therefore, we conclude that the combined use of liming and vegetation enhance the mobilization of Fe in eutrophic wetland soils polluted by mine wastes under alternating flooding–drying conditions. This should be considered for the environmental management of these sites due to the role of Fe-minerals as sink for potentially-harmful compounds. [Copyright &y& Elsevier]

Spontaneous growth of native vegetation in abandoned metal(loid) mine tailings can be valuable for phytomanagement restoration projects. This study aimed to assess the degree to which spontaneous plant colonization of abandoned metal(loid) mine tailings from Mediterranean semiarid areas led to functional soil improvement, and to identify, if possible, a critical level indicating that this functionality was moving towards that of the vegetated soils from the surroundings. Vegetation ecological indexes, plant life forms and species functional roles, together with physicochemical and functional soils parameters, were studied in metal(loid) mine tailings abandoned ~40 years ago and surrounding forests in SE Spain. Vegetation patches showed only small differences in physicochemical parameters related to soil abiotic stress conditions (pH, salinity and metals), regardless of the vegetation. However, vegetation patches with greater species diversity and richness and presence of plants with contrasted life forms and functional traits that facilitate the growth of less stress-tolerant species showed an increase of the soil microbial functionality (higher microbial biomass C, β-glucosidase activity, bacterial metabolic activity and functional diversity). Moreover, these vegetation patches showed a functional soil status comparable to that of the forests outside the mine tailings. In this sense, the present study showed the value of preserving these vegetation patches since they may act as nucleation spots favoring positive plant-soil feedbacks that may help to accelerate the functional recovery of these degraded areas. Furthermore, strategies to promote the creation of new vegetation patches including a variety of species with contrasted life forms and functional traits should be considered in phytomanagement restoration projects for abandoned metal(loid) mine tailings. [Display omitted] • Soil microbial functionality evaluated by CLPP technique. • Similar soil abiotic stress parameters in tailing vegetation patches. • Higher plant diversity-richness, higher scores of functional-related soil parameters. • More diverse and rich vegetation patches had closer soil functional status to forests. • Spontaneously colonized niches are valuable spots for phytomanagement. [ABSTRACT FROM AUTHOR]

Total and inorganic soil P were extracted from a coastal salt marsh in SE Spain receiving eutrophicated water of urban and agricultural origin. The greatest P contents were obtained within the upper 10 cm of soil of those sectors of the salt marsh most affected by urban waste water effluents. Most of the P was extracted using HCl, indicating that it is mainly bonded to Ca compounds. Only in sites with low CaCO3 content was the quantity of P associated with Fe and Al oxides and hydroxides (extracted with NaOH) noticeable. [Copyright &y& Elsevier]

Phytomanagement is considered a suitable option in line with nature-based solutions to reduce environmental risks associated to metal(loid) mine tailings. We aimed at assessing the effectiveness of biochar from pruning trees combined with compost from urban solid refuse (USR) to ameliorate the conditions of barren acidic (pH ~5.5) metal(loid) mine tailing soils (total concentrations in mg kg−1: As ~220, Cd ~40, Mn ~1800, Pb ~5300 and Zn ~8600) from Mediterranean semiarid areas and promote spontaneous plant colonization. Two months after amendment addition were enough to observe improvements in chemical and physico-chemical tailing soil properties (reduced acidity, salinity and water-soluble metals and increased organic carbon and nutrients content), which resulted in lowered ecotoxicity for the soil invertebrate Enchytraeus crypticus. Recalcitrant organic carbon provided by biochar remained in soil whereas labile organic compounds provided by USR were consumed over time. These improvements were consistent for at least one year and led to lower bulk density, higher water retention capacity and higher scores for microbial/functional-related parameters in the amended tailing soil. Spontaneous growth of native vegetation was favored with amendment addition, but adult plants of remarkable size were only found after three years. This highlights the existence of a time-lag between the positive effects of the amendment on tailing soil properties being observed and these improvements being translated into effective spontaneous plant colonization. [Display omitted] • Combination of biochar and urban solid refuse improved metal(loid) mine tailing soil. • Amendment improvements in tailing physico-chemistry and nutrients sustained over time. • Greater scores for microbial/functional-related parameters in amended tailing soil. • Spontaneous colonization by surrounding native vegetation in amended tailing soil. • Time-lag between evident tailing soil improvements and effective plant colonization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil metal(loid)s did not hinder spontaneous vegetation colonization of mine tailings. • Spontaneously vegetated metal(loid) mine tailings showed improved soil function. • Similar soil biological activity in vegetated mine tailing sites than in forests. • Vegetated metal(loid) mine tailing can be even less toxic than surrounding forests. • Passive restoration is valuable for phytomanagement of mine tailings. This work studies a set of soil indicators (physical, physico-chemical and biological), evaluated under field and laboratory conditions, in different stages of spontaneous vegetation colonization in abandoned metal(loid) mine tailings from Mediterranean semiarid areas. The results provide evidence about the interest of spontaneous colonization by native vegetation for the phytomanagement of abandoned metal(loid) mine tailings in terms of providing ecosystem functions. Bare soils (B), small groups of pine trees (P), scattered pine trees with shrubs and herbs under the canopy (P + S), and dense patches of pine trees with shrubs and herbs under the canopy (DP + S) were studied inside mine tailings abandoned ≈40 years ago. Besides, pine forests next (FN) and away (FA) from the tailings were also studied. Pioneer and nurse plants were mainly found inside the tailings, although ecological indexes in P + S and DP + S were similar to FN and FA. Pedogenesis evidences such as structure development and increase in cation exchange capacity, organic C and N were found in tailing soils from B to DP + S. However, soil metal(loid)s did not follow the same variation pattern. For example (in mg kg−1): P showed the maximum total Cu (≈277) and Zn (≈17,860), while P + S of As (≈1250) and Pb (≈14,570). B had the maximum water extractable Pb (≈4) and Zn (≈207), while FA of As (≈0.192) and Cu (≈0.149). Soil microbial biomass C, enzyme activity, CO 2 emission, organic matter decomposition and feeding activity of soil dwelling organisms indicated similar, or even higher, biological activity in P + S and DP + S than in FN and FA. In fact, FA showed the highest soil ecotoxicity risk (reduced enchytraeid reproduction). Therefore, mine tailing soils can be effectively modified following spontaneous vegetation colonization, achieving conditions with capacity to provide certain ecosystem functions. Hence, phytomanagement of these tailings should be preceded by a detailed knowledge of the existing spontaneously colonized sites, which should be preserved to take advantage of their potentiality. [ABSTRACT FROM AUTHOR]

Leachates from intensive agriculture containing high nitrate have been identified as a major cause of the severe eutrophication crisis that impacts Mar Menor (SE Spain), the largest hypersaline coastal lagoon in the Mediterranean basin. A best management practice for removing NO 3 −-N is denitrifying bioreactors. This is the first study to assess the efficiency of citrus woodchips bioreactors in treating agricultural leachates that flow to the Mar Menor via surface discharges. Denitrification capacity, woodchip degradation (by weight loss), formation of potentially harmful compounds, and greenhouse gas (GHG) emissions were assessed. Three bioreactors (6 m × 0.98 m x 1.2 m) filled with citrus woodchips (3 m3 d−1 per bioreactor) through which the untreated ditch water over 1.5 years. Bioreactors were operated at 8 h, 16 h, and 24 h hydraulic residence time respectively, in each bioreactor. The main characteristics of the ditch water were: pH ≈ 7.5–8.0, electrical conductivity ≈ 5–8 dS m−1, dissolved organic carbon ≈6–10 mg L−1, and NO 3 −-N ≈ 22–45 mg L−1. Bioreactors were highly efficient in reducing NO 3 −-N. The average R NO3 in effluents was for the complete experimental period 8 g N m−3 d−1, 10.9 g N m−3 d−1, and 12.6 g N m−3 d−1 for 8, 16 and 24 h residence time, respectively. Nitrate reduction efficiency was modulated by seasonal changes in temperature, with an increasing efficiency in warmer periods (maximum ≈ 85–90% for all hydraulic residence time) and decreasing in colder ones (minimum ≈ 12%, 23% and 41% for hydraulic residence time 8, 16 and 24 h respectively). Woodchips degradation was greatest during the first six months (average ≈ 29% weight loss) in the material above the water level, attributable to aerobic mineralization of the organic carbon, while weight loss was ≈11% in woodchip media continuously below the water level. Dissolved organic carbon, sulfide, ammonium, and soluble phosphorus concentrations in the effluents were mostly low, although some peaks in concentrations occurred. Design consideration must be taken to avoid environmental impacts due to the occasional presence of harmful compounds in the effluents. [Display omitted] • Citrus woodchip bioreactors denitrified saline leachates with NO 3 −-N = 22–45 mg L−1 • Woodchip aging negatively affected nitrate removal particularly below ≈20 °C. • Sulfide, ammonium, and soluble phosphorus may appear in bioreactor effluents. • Higher CO 2 emissions and woodchips degradation occurred above the water level. • Woodchips continuously flooded had a higher production of N 2 O emissions. [ABSTRACT FROM AUTHOR]

Plant selection is a critical issue for the long-term success of phytomanagement projects. The presence of “microenvironments” related to salinity in mine tailings under semiarid climates make halophytes a suitable alternative for phytostabilisation. The goal of this work was to assess the criteria for plant species selection for the phytostabilisation of mining wastes in semiarid areas, focusing on the suitability of the employment of spontaneous halophyte plant species. For this purpose, a comprehensive soil below-plant and plant survey including spontaneous halophyte and non-halophyte plant species were performed in an extensive area covered by mining wastes in SE Spain. The soil samples collected below halophyte plants showed higher electrical conductivity, organic carbon and water extractable salts concentrations than the non-halophyte ones. Zygophyllum fabago and Limonium cossonianum were the most suitable species to colonize the salty micro niches at the tailings while Tamarix canariensis and Atriplex halimus showed the best soil fertility indicators under moderate electrical conductivity values. In general, the halophyte species showed lower metal(loid) concentrations in leaves or shoots than the non-halophyte ones ( e.g . Cistus monspeliensis , Dittrichia viscosa and Helichrysum decumbens ). Oppositely, the leaves of halophyte plant species, specially A. halimus and Z. fabago , showed higher accumulation of Na and Cl which may be of interest to effect the long term desalination of the tailings. The interest of employing halophytes is not only focused on metal(loid)s tolerance but also in the high potential for soil improvement (organic matter accumulation, desalination). The positive effects of combining halophyte with non-halophyte plant species may enhance the long-term sustainability of the plant community. [ABSTRACT FROM AUTHOR]

Wetlands are highly effective systems in removing large amounts of N from waters, preventing eutrophication processes. However, when wetlands are polluted by metal-mine wastes their capacity to act as green filters may be diminished. The objective of this study was to evaluate the effect of liming and plants (Sarcocornia fruticosa and Phragmites australis) on the removal of NO3 − from eutrophic water in slightly acidic, wetland soils polluted by metal-mine wastes. Simulated soil profiles were constructed and six treatments were assayed: (1) no liming + no plant, (2) no liming + S. fruticosa, (3) no liming + P. australis, (4) liming + no plant, (5) liming + S. fruticosa and (6) liming + P. australis. Three horizons were differentiated: A (never under water), C1 (alternating flooding-drying conditions) and C2 (always under water). The eutrophic water used to flood the soil profiles was enriched in N and organic carbon (pH ∼ 7.5, electrical conductivity ∼ 11 dS m−1, NO3 − ∼ 234 mg L−1 and dissolved organic carbon ∼ 106 mg L−1). The pH, Eh and concentrations of dissolved organic carbon (DOC), N–NO3 − and N–NH4 + were measured regularly for 18 weeks. Liming stimulated the growth of plants, especially for S. fruticosa (20-fold more plant biomass than without liming), increased the soil pH and favoured the decline of the Eh values, enhancing the removal of NO3 − via denitrification. Of all the treatments assayed, liming + S. fruticosa was the only treatment that removed almost completely the high concentration of NO3 − from the eutrophic flooding water, reaching ∼1 mg L−1 N–NO3 − at the end of the experiment, at all depths. The higher content of DOC in the pore water of this treatment could explain this behaviour, since more labile carbon was available to the soil microorganisms in the rhizosphere, favouring NO3 − removal through denitrification processes. However, the treatment liming + P. australis (2-fold more plant biomass that without liming) did not remove completely the high concentrations of NO3 − from the eutrophic water, except in the C2 horizon – which was permanently under water. Hence, our results show that the effectiveness of liming, regarding the removal of NO3 − from eutrophic flooding water in wetland soils polluted by metal-mine wastes, depends on the presence of plants, their growth and the production of organic compounds in the rhizospheric environment. [Copyright &y& Elsevier]

Abstract: The aim of this study was to assess the effectiveness of combining liming and vegetation for the phytomanagement of strongly acidic, saline eutrophic wetlands polluted by mine wastes. Simulated soil profiles were constructed and four treatments were assayed: without liming+without plant, without liming+with plant, with liming+without plant and with liming+with plant. The plant species was the halophyte Sarcocornia fruticosa. Three horizons were differentiated: A (never under water), C1 (alternating flooding–drying conditions) and C2 (always under water). The soluble Cd, Cu, Mn, Pb and Zn concentrations were measured regularly for 18weeks and a sequential extraction procedure was applied at the end of the experiment. Liming was effective (between ∼70% and ∼100%) in reducing the soluble Zn, Cu and Pb. In contrast, soluble Mn and Cd increased with liming, especially in the treatment with liming+with plant, where the concentrations were 2-fold higher than in the non-limed treatments. The amendment increased the contents of Zn, Mn and Cd bound to potentially-mobilisable soil fractions at the expense of the most-environmentally-inert fractions. Hence, the combined use of liming and vegetation may increase the long-term environmental risk of metals solubilisation. [Copyright &y& Elsevier]

Abstract: The aim of this study was to identify the effectiveness of liming in combination with vegetation for the recovery of slightly acidic, saline soils of eutrophic wetlands affected by mine wastes, under fluctuating flooding conditions. Simulated soil profiles were constructed and four treatments were assayed under greenhouse conditions: control, only plant, only liming, and liming and plant. The plant species was the halophyte Sarcocornia fruticosa. Three horizons were differentiated: A (never under water), C1 (alternating flooding-drying conditions), and C2 (always under water). The pH, Eh, salinity, and the concentrations of dissolved organic carbon and soluble metals were measured regularly for 18 weeks. Liming favoured the growth of S. fruticosa, an increase in pH and a fall in Eh. The amendment was effective for reducing Mn, Zn, and Cd in pore water of bare soils, but not Cu and Pb. In the treatment with liming and plant, the growth of S. fruticosa counteracted the effect of the amendment, strongly increasing the concentrations of metals in pore water and distributing them along the soil profile. Hence, the combined use of liming and plants may increase the risk of metals mobilisation. [Copyright &y& Elsevier]

The present work studied the germination recovery of Arthrocnemum macrostachyum, Juncus acutus, and Schoenus nigricans seeds after submersion in hypersaline solution of different salt types. Germination recovery of seed lots incubated in 1, 2, 3, 4, or 5% saline solutions of NaCl, MgCl2, MgSO4, and Na2SO4 for 30 d was studied by transferring ungerminated seeds to distilled water. Seed germination of A. macrostachyum was only inhibited at the highest salinity (4% NaCl, 5% MgCl2) but these ungerminated seeds showed a high germination recovery (81% and 83%, respectively) in distilled water. Seed germination of S. nigricans was totally inhibited by salts and only 26% of them germinated in the control treatment. However, the germination recovery of this species could be stimulated by high salt concentrations (germination of ungerminated seeds incubated at 5% Na2SO4 reached 66% in distilled water). Juncus acutus germinated well without salt (95% in the control treatment) but high salt concentrations inhibited them from germination. However, ungerminated seeds were not damaged by salt, showing a high level of recovery (c. 100% in all salt types and concentrations). The chlorides were more inhibitory to germination than sulphates at equivalent concentrations. The germination-related characteristics of J. acutus and S. nigricans mean that both species may be considered halophytes although neither of them can tolerate such high salinity levels as A. macrostachyum, Juncus acutus, and A. macrostachyum produce nondormant seeds, whereas a high proportion of S. nigricans seeds are dormant. These laboratory results are related to the field ecology of the three species. [ABSTRACT FROM AUTHOR]

Abstract: We studied the germination responses of Arthrocnemum macrostachyum, Juncus acutus and Schoenus nigricans to saline stress caused by different salt types. The germination percentage and mean time to germination data were obtained by incubating seeds for 30d in 1, 2, 3, 4 or 5% saline solutions of NaCl, MgCl2, MgSO4 and Na2SO4 at 30/20°C and with a 12h photoperiod. A. macrostachyum was the most tolerant species to salinity during the germination (65% in 2% NaCl). S. nigricans showed the lowest germination (none germinated in salt and only 26% in distilled water). J. acutus showed intermediate behaviour between the two above species, its germination being inhibited by high salt concentrations. The sulphates had less inhibitory effect than the equivalent chloride concentrations. [Copyright &y& Elsevier]

Abstract The suitable phytomanaging of mine tailings not only requires an improvement of soil fertility but also the assessment of the biotic interactions between the selected plant species. This study aimed to evaluate the effect of an organic amendment on the response of two plant species of contrasting habit, a tree, Pinus halepensis and a grass, Piptatherum miliaceum growing on a metal(loid)-contaminated substrate collected from mine tailings. Pots containing single plant individuals or their combination, with and without organic amendment (at 10% rate), were established and grown in a greenhouse for 13 months. Plant biomass, foliar ionome, leaf δ15N and metal(loid) concentrations were measured at the end of the experiment. The amendment alleviated P deficiency in the substrate and strongly stimulated biomass production by both plant species (10-fold for pine; 90-fold for the grass), leading to more balanced N/P ratios in leaves (especially for the grass). Co-culture with the grass negatively affected pine growth, decreasing total biomass and leaf δ15N values and inducing severe N deficiency (leaf N/P ratio<10). In contrast, co-culture with pine improved the nutrient status and growth of the grass, but only under non-amended conditions. Needle metal(loid) concentrations in P. halepensis were affected by both amendment addition and co-culture with the grass. High biomass growth with low metal(loid) concentrations in P. miliaceum leaves for the amended treatment makes this grass species suitable for the phytomanagement of metal(loid) polluted tailings, since it achieves high biomass production together with low concentrations of metal(loid)s in edible/senescent parts. Highlights • Co-culture modulated plant performance in amended treatments. • Co-culture with the grass P.miliaceum negatively affected pine (P.halepensis) growth. • P.miliaceum showed higher competitive ability when co-cultured with P.halepensis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combination of groundwater abstraction and seawater irrigation. • Irrigation program helped keeping groundwater level near the salt-marsh surface. • Soil salinity decreased in ponds continuously irrigated with seawater. • Irrigation with seawater contributed to increase plant cover in the long term. Groundwater abstraction is among the main anthropogenic causes of wetland desiccation worldwide, and corrective measures must be taken to avoid degradation of this valuable ecosystems. A case study is the Agua Amarga salt marsh (≈180 ha) (SE Spain). Agua Amarga includes a solar saltwork pond network in operation between 1925 and 1975, when it was abandoned, and the ponds were colonized by salt marsh vegetation. In 2008 two desalination plants were operating in the marsh vicinity, which were supplied with groundwater. To mitigate the possible negative impact on the salt marsh ecosystem due to groundwater drawdown, in 2009 a sea water irrigation program was implemented. This paper summarizes the results of a ten-year monitoring program (2010–2020) to evaluate the effects of the irrigation program on groundwater levels and quality, soil salinity and moisture, and vegetation cover. During this period, average groundwater level was 2.5 m below the surface and around 1 m deep near the irrigated ponds. Groundwater salinity was not affected outside the saltmarsh, but inside, where the saltworks caused values to rise above 300 mS/cm, it decreased more than 150 mS/cm in some 20 m deep piezometers. Between 2012 and 2020, vegetation cover increased between ≈10 and ≈25 %, with halophyte species such as Arthrocnemum macrostachyum and Sarcocornia fruticosa being the most favoured. In areas with prolonged flooding, Ruppia maritima , a plant species that lives submerged in saline water, was found. In the irrigated areas, soil electrical conductivity (1:5 soil:water extracts) decreased from ≈7-14 mS cm-1 to ≈2-6 mS cm-1. We present an example of sustainable actions in a coastal wetland, where the exploitation of water resources in semiarid areas is combined with promoting natural habitats. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of different fertilizing strategies applied during three successive cycles on lettuce growth and the nitrate evolution in the soil, leaching water, and the lettuce plant itself. Four fertilization treatments were compared: integrated production fertilization (IP), organic fertilization (ORG), slow-release N fertilizers (SRF), and plant-associative bacteria (PAB). The nitrate content of the pore water and leachate decreased toward harvesting time in each crop cycle. The accumulation of residual nitrates in the soil decreased in each successive cycle in all treatments. The greatest lettuce head weight was achieved by ORG and SRF in the first cycle and by IP in the third cycle; IP and SRF produced the greatest nitrate content in lettuce leaves, especially in the second and third cycles. The nitrate content of leaves fell in the last cycle, as nitrate levels in soil and in leaching fell in all treatments. [ABSTRACT FROM AUTHOR]

Abstract: Salt marshes near urban, industrial and mining areas are often affected both by heavy metals and by eutrophic water. The aim of this study was to assess and evaluate the main processes involved in the decrease of nitrate concentration in pore water of mine wastes flooded with eutrophic water, considering the presence or absence of plant rhizhosphere. Basic (pH∼7.8) carbonated loam mine wastes and free-carbonated acidic (pH∼6.2) sandy-loam mine wastes were collected from polluted coastal salt marshes of SE Spain which regularly receive nutrient-enriched water. The wastes were put in pots and flooded for 15 weeks with eutrophic water (dissolved organic carbon ∼26mgL−1, PO4 3− ∼23mgL−1, NO3 − ∼180mgL−1). Three treatments were assayed for each type of waste: pots with Sarcocornia fruticosa, pots with Phragmites australis and unvegetated pots. Soluble organic carbon, nitrate, soluble Cd, Pb and Zn, pH and Eh were monitored. But the 2nd day of flooding, nitrate concentrations had decreased between 70% and 90% (equivalent to 1.01–1.12gN-NO3 − m−2 day−1) with respect to the content in the water used for flooding, except in unvegetated pots with acidic wastes. Denitrification was the main mechanism associated with the removal of nitrate. The role of vegetation in improving the rhizospheric environment was relevant in the acidic wastes because higher sand content, lower pH and higher soluble metal concentrations might strongly hinder microbial activity Hence, revegetation of salt marshes polluted by acidic sandy mining wastes might improve the capacity of this type of environment to act as a green filter against excessive nitrate contents flowing through them. [Copyright &y& Elsevier]

Abstract: The aim of this study was to evaluate the combined effects of liming and behaviour of Sarcocornia fruticosa as a strategy of phytomanagement of metal polluted salt marsh soils. Soils were taken from two polluted salt marshes (one with fine texture and pH∼6.4 and the other one with sandy texture and pH∼3.1). A lime amendment derived from the marble industry was added to each soil at a rate of 20gkg−1, giving four treatments: neutral soil with/without liming and acidic soil with/without liming. Cuttings of S. fruticosa were planted in pots filled with these substrates and grown for 10 months. The pots were irrigated with eutrophicated water. As expected, lime amendment decreased the soluble metal concentrations. In both soils, liming favoured the growth of S. fruticosa and enhanced the capacity of the plants to phytostabilise metals in roots. [Copyright &y& Elsevier]

Abstract: The occurrence of mining areas in the vicinities of salt marshes may affect their ecological functions and facilitate the transfer of pollutants into the food chain. The mobilisation of metals in salt marsh soils is controlled by abiotic (pH, redox potential) and biotic (influence of rhizosphere) factors. The effect of the rhizosphere of two plant species (Sarcocornia fruticosa and Phragmites australis) and different flooding regimes on potentially harmful metals and As mobilisation from salt marsh soil polluted by mining activities were investigated (total concentrations: 536mgkg−1 As, 37mgkg−1 Cd, 6746mgkg−1 Pb, 15,320mgkg−1 Zn). The results show that the changes in redox conditions (from 300mV to −100mV) and pH after flooding and rewetting periods may mobilise the contaminant elements into soil solution (e.g., 100μgL−1 Cd, 30μgL−1 Pb, 7mgL−1 Zn), where they are available for plants or may be leached from the soil. Drying periods generated peaks of concentrations in the soil solution (up to 120μgL−1 Cd and 50μgL−1 Pb). The risk assessment of As and metal-polluted salt marshes should take into account flood dynamics in order to prevent metal(loid) mobilisation. [ABSTRACT FROM AUTHOR]

Woodchip bioreactors are widely known as a best management practice to reduce excess nitrate loads that are discharged with agricultural leachates. The aim of this study was to evaluate the performance of citrus woodchip bioreactors for denitrification of brine (electrical conductivity ≈ 17 mS cm−1) from groundwater desalination plants with high nitrate content (NO 3 −-N ≈ 48 mg L−1) in the Campo de Cartagena agricultural watershed, one of the main providers of horticultural products in Europe. The performance was evaluated relative to seasonal changes in temperature, dissolved organic carbon (DOC) provided by woodchips, hydraulic residence time (HRT) and woodchip aging. Bioreactors (capacity 1 m3) operated for 2.5 years (121 weeks) in batch mode (24 h HRT) with three batches per week. Denitrification efficiency was modulated by DOC concentration, temperature, hydraulic residence time and the drying-rewetting cycles. High salinity of brine did not prevent nitrate removal from occurring. The high DOC availability (>25 mg C L−1) during the first ≈48 weeks resulted in high nitrate removal rate (>75%) and nitrate removal efficiency (until ≈ 25 g N m−3 d−1) regardless of temperature. Moreover, the high DOC contents in the effluents during this period may present environmental drawbacks. Denitrification was still high after 2.5 years (reaching ≈9.3 g N m−3 d−1 in week 121), but dependence on warm temperature became more apparent with woodchips aging from week ≈49 onwards. Nitrate removal efficiency was highest on the first weekly batch, immediately after woodchips had been unsaturated for four days. It was attributable to a flush of DOC produced by aerobic microbial metabolism during drying that stimulated denitrification following re-saturation. Hence, alternance of drying-rewetting cycles is an operation practice that increase bioreactors nitrate removal performance. [Display omitted] • Citrus woodchips effectively denitrify high-nitrate concentration brine. • Citrus woodchip bioreactors provide enough organic carbon for the denitrification. • Drying-rewetting cycles improve denitrification due to aerobic conditions. • DOC, temperature and HRT had an effect on denitrification efficiency. • Evolution woodchips from a two-year-old denitrifying bioreactor were evaluated. [ABSTRACT FROM AUTHOR]