We evaluated the ecophysiological responses of two semiarid coniferous tree species, Pinus halepensis and Tetraclinis articulata, growing on a nutrient-poor metalliferous mine tailings substrate to ...organic amendments (biochar and/or organic municipal waste). The trees were grown in mesocosms under irrigated conditions for 20 months. Then, a comprehensive characterization of soil and plant parameters (including stable isotopes) was carried out. Treatments containing municipal waste showed better soil fertility indicators (approximately 2-fold higher organic carbon and total nitrogen concentrations) and higher plant biomass (up to 5-fold higher) than unamended and only biochar treatments. Trees in most of the treatments exhibited leaf N/P ratios <14 indicating severe N limitation of plant growth. Metal uptake was below phytotoxic levels across all the treatments. Leaf δ13C values correlated positively with δ18O across treatments for both species indicating increasing water use efficiency with tighter stomatal regulation of water flux, and with T. articulata exhibiting tighter stomatal control (higher δ18O values) than P. halepensis. Trees in treatments containing only biochar did not differ in ecophysiological performance from those in the unamended treatments. In contrast, leaf stable isotopes revealed sharply increased of time-integrated photosynthetic activity (favoured by higher leaf N concentrations) combined with lower time-integrated stomatal conductance in the treatments containing municipal waste, indicating greatly enhanced water use efficiency in better nourished plants. Trade-offs between water use efficiency and nutrient (N and P) use efficiency were evident across treatments, with higher leaf nutrient concentrations associated with higher water use efficiency, at the cost of a lower nutrient use efficiency. These trade-offs were not impaired by the high metal concentrations of the tailings substrate, indicating that ecophysiological adjustments in response to changes in plant nutrient status promoted by the addition of organic amendments are critical for the adaptability of native tree species employed in the phytostabilisation of mine tailings.
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•Organic amendments improve tree drought resistance and growth performance.•Better nourished plants were able to improve water use efficiency.•Metal uptake issues are not enough to fully explain tree adaptation to mine tailings.•A strong trade-off between water and nutrient use efficiency occurred in both trees.
The phytostabilization of mine tailings requires a previous assessment of the effects of soil amendments on metal mobility. The goal of this work was to evaluate the response of metal availability ...(both labile and potentially available pools) to the addition of two organic amendments (a municipal waste biosolid and a tree biochar), separately and in combination, in a mine tailings substrate. For this purpose, a comprehensive comparison among several single extraction procedures and a sequential extraction procedure was performed. The effects on metals phytotoxicity were assessed through a germination test using seeds of
Zygophyllum fabago
. When evaluating the effect of the amendments in the labile metal pool, the biochar resulted effective in decreasing metal-extractable concentrations, especially for Cd, Mn and Zn. The treatment with biochar also showed better germination parameters (percentage of germinated seeds and sooner germination) than the rest of the unamended and amended treatments. The use of the municipal organic biosolid increased labile metal concentrations and potentially available metal pools assessed with EDTA and did not contribute to achieve better results of seed germination. Compared to the single biosolid treatment, the combination of biochar/biosolid modulated some labile metal concentrations and showed similar germination parameters to those obtained for the treatment amended only with biochar. This positive effect of biochar in modulating the soluble metal concentrations associated with certain urban/agricultural organic materials supported the suitability of using these combinations in field applications, although a higher rate of biochar application would be recommended to obtain a more beneficial effect.
The suitable application of phytomanagement by phytostabilisation using plant tree species in metal-polluted soils requires an assessment of the fate of metals in biological tree compartments. The ...goal of this work was to evaluate the effect of an urban compost amendment on metal allocation in two evergreen tree species (
Pinus halepensis
and
Tetraclinis articulata
) growing in a metal-enriched polluted substrate. A comprehensive characterisation of edaphic parameters and metal speciation was carried out. Plant analyses included metal concentrations in different tree compartments: roots, stems, branches and leaves. The amendment caused a significant increase in plant biomass for both trees, although
T. articulata
produced 2.5 times more biomass than
P. halepensis
. The amendment alleviated P deficiency in
P. halepensis
. This did not occur for the N deficiency detected in
T. articulata
. The latter showed no effect of the amendment in the allocation of metals, being most of them restricted at the root compartment (> 50%). For
P. halepensis,
similar behaviour occurred for Cu, Pb and Zn. However, for Cd, the amendment caused its redistribution into pine shoots, probably due to its transport associated with the increased transpiration. Results indicated that
T. articulata
may be a promising tree species to be used in phytomanagement programs under semiarid climates due to its low metal translocation into shoots and remarkable biomass production under amendment conditions.
Environmental contamination by hazardous heavy metals/metalloids (metal(loid)s) is growing worldwide. To restrict the migration of toxic contaminants, the establishment of a self-sustainable plant ...cover is required. Plant growth in multi-polluted soils is a challenging issue not only by metal(loid) toxicities, but also by the co-occurrence of other stressors. Dittrichia viscosa is a pioneer Mediterranean species able to thrive in metal(loid)-enriched tailings in semi-arid areas. The aim of the present work was to examine the metabolic adjustments involved in the acclimation responses of this plant to conditions prevailing in mine-tailings during Mediterranean spring and summer. For this purpose, fully-expanded leaves, and rhizosphere soil of both mining and non-mining populations of D. viscosa grown spontaneously in south-eastern Spain were sampled in two consecutive years. Quantitative analysis of >50 biochemical, physiological and edaphic parameters were performed, including nutrient status, metal(loid) contents, leaf redox components, primary and secondary metabolites, salicylic acid levels, and soil physicochemical properties. Results showed that mining plants exhibited high foliar Zn/Pb co-accumulation capacity, without substantially affecting their photosynthetic metabolism or nutritional status even in the driest summer period. The comparison of the antioxidative/oxidative profile between mining and non-mining D. viscosa populations revealed no major seasonal changes in the content of primary antioxidants (ascorbate and GSH), or in the levels of ROS. Multivariate analysis showed that phenylalanine ammonia-lyase (PAL) and peroxidase (PRX) activities and soluble and cell wall-bound phenols were potential biomarkers for discriminating between both populations. During the dry season, a marked enhancement in the activity of both PAL and soluble PRX resulted in both a drop in the accumulation of soluble phenols and an increase of the strong metal chelator caffeic acid in the cell-wall fraction, supporting the view that the plasticity of phenylpropanoid metabolism provide an effective way to counteract the effects of stress combinations.
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•No major seasonal changes in AA, GSH and ROS were observed in D. viscosa populations.•Phenolics seem to play a key role in D. viscosa acclimation to metal-polluted soils.•PAL, PRX, soluble and cell-wall phenolics help to discriminate D. viscosa populations.•High accumulation of Pb and Zn in leaves did not affect physiology of D. viscosa.•High levels of caffeic acid are present in cell walls of mining D. viscosa population.
This study aimed to assess the effectiveness of biochar from sewage sludge -BSS- and from pruning trees -BPT- (addition dose of 6% d.w.) to immobilise metals in acidic (pH ∼ 4.7) and basic (pH ∼ 7.4) ...mine soils under variable flooding conditions, and to determine biochar influence on plant (Sarcocornia fruticosa -Sf-) growth and metal uptake. BSS had lower pH (∼8.2 vs. ∼ 9.8), CaCO3 (∼71 vs. ∼ 85 g kg−1), total organic carbon (∼354 vs. ∼ 656 g kg−1) and higher water soluble organic carbon (WSOC ∼ 0.15 vs ∼ 0.06 mg kg−1) than BPT. PVC columns (15 × 30 cm) were prepared with the following treatments (n = 4): 1) no Biochar-no Sf; 2) no Biochar-Sf; 3) BSS-no Sf; 4) BSS-Sf; 5) BPT-no Sf; 6) BPT-Sf. Changes in water table level (WL) were simulated for 303 days with tap water (upper 0–15 cm alternating flooding-drying conditions, lower 15–30 cm always underwater). The pH, redox potential (Eh), temperature and porewater WSOC, Zn, Cd and Pb concentrations were regularly measured, and plants were removed at the end and length, fresh weight and metal concentrations in tissues measured. In the basic soil, there were no consistent evidences that BSS and BPT were effective decreasing porewater metal concentrations and reducing metal uptake in plants. Sf contributed to mobilise Zn, and in less extent Cd, in the upper soil layer, regardless of the type of biochar, and this effect increased with aging. In the acidic soil, BSS and BPT were effective increasing the pH and decreasing porewater metals. BSS increased its efficiency with aging, which can be mainly attributable to the more reduced conditions that induced (lower Eh values) due to its higher WSOC content. Biochar was effective hindering metal mobilisation by Sf and reducing plant's metal uptake (e.g. reduction in roots: ∼7 fold for Zn, ∼19-fold for Cd and ∼ 2-fold for Pb). BSS was more effective promoting Sf growth (fresh weight) than BPT. Therefore, in relation with the use of biochar from sewage sludge and from pruning trees as soil amendments under flooding-non flooding conditions, we can conclude that it can be a useful option in acidic mine soils for decreasing water soluble metals and improving plant growth. However, in basic mine soils, we have no evidences to support the advantages of using these two types of biochar as amendments. Hence, the use of biochar in metal-polluted wetlands has environmental implications that must be planned for each specific case in order to optimize the positive aspects (wetland as sinks of pollutants) and reduce the drawbacks (wetland as source of pollutants).
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•Hydric mine soils were amended with biochar from sewage sludge and pruning trees.•Biochar did not modify the pH and porewater metals in hydric basic mine soils.•Biochar increased the pH and decreased porewater metals in hydric acidic mine soils.•Flooding regime, temperature and plants modulated biochar effectiveness.•Biochar reduced plant's metal uptake in acidic but not in basic hydric mine soils.
The study of the rhizospheric microbiome in native plants should be a prerequisite before carrying out the phytomanagement of mine tailings. The goal of this work was to evaluate the rhizospheric ...microbiome of
Piptatherum miliaceum
in semiarid mine tailings. A comprehensive edaphic characterization was performed including the description of soil microbial composition in the rhizosphere of
P. miliaceum
growing at a mine tailings pile and at a control site. Plant nutritional and isotopic compositions were also determined. Neutral pH of the tailings (7.3) determined low metal extractability in 0.01 M CaCl
2
(e.g. < 1 mg/kg for Zn). In spite of the contrasting edaphic fertility conditions of both sites, N (~ 15 g kg
−1
) and P (~ 400 mg kg
−1
) leaf concentrations were similar. The lower δ
15
N at the tailings plants (− 4.50‰) compared to the control (6.42‰) indicated greater efficiency of
P. miliaceum
for uptaking N under the low fertility conditions of the tailings (0.1% total soil nitrogen). The presence at the tailings of bacterial orders related to the cycling of N, such as
Rhizobiales,
could have contributed to enhance N acquisition. The lower leaf δ
13
C values at the tailings (− 30.22‰) compared to the control (− 28.47‰) indicated lower water use efficiency of the tailing plants. Some organotrophic bacterial and fungal groups in the tailings’ rhizospheres were also found in the control site (e.g.
Cytophagales
,
Sphingobacteriales
for bacteria;
Hypocreales
,
Pleosporales
for fungi). This may indicate that
P. miliaceum
is able to shape its own specific microbiome at the tailings independently from the initial microbial composition of the tailings.
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.
•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.
This study aimed to evaluate the response of salt marshes to pulses of PO43--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-PO43-) and high (19.5 mg L−1 P-PO43-) P load, and with the presence/absence of Phragmites. The PO43- 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.
•No effect of nutrient load, seasonality and plant presence on P removal efficiency.•P removal from pore water unaffected by flooding-drying cycles.•Soil Ca/Mg compounds were the main P sink.•Phragmites rhizomes were the organs that more contributed to accumulate P.•Wetlands are efficient to depurate intermittent nutrient-enriched water pulses.
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 CaCO3, loam texture). In the amended mine tailings soil, with lower buffer capacity (pH~7, low CaCO3, 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.
•Soil incubation may change metal availability.•Low soil buffer capacity promotes labile metal fractions.•Organic matter decomposition favours metal release.
IntroductionChronic malnutrition is a serious problem in southern Angola with a prevalence of 49.9% and 37.2% in the provinces of Huila and Cunene, respectively. The MuCCUA (Mother and Child Chronic ...Undernutrition in Angola) trial is a community-based randomised controlled trial (c-RCT) which aims to evaluate the effectiveness of a nutrition supplementation plus standard of care intervention and a cash transfer plus standard of care intervention in preventing stunting, and to compare them with a standard of care alone intervention in southern Angola. This protocol describes the planned economic evaluation associated with the c-RCT.Methods and analysisWe will conduct a cost-efficiency and cost-effectiveness analysis nested within the MuCCUA trial with a societal perspective, measuring programme, provider, participant and household costs. We will collect programme costs prospectively using a combined calculation method including quantitative and qualitative data. Financial costs will be estimated by applying activity-based costing methods to accounting records using time allocation sheets. We will estimate costs not included in accounting records by the ingredients approach, and indirect costs incurred by beneficiaries through interviews, household surveys and focus group discussions. Cost-efficiency will be estimated as cost per output achieved by combining activity-specific cost data with routine data on programme outputs. Cost-effectiveness will be assessed as cost per stunting case prevented. We will calculate incremental cost-effectiveness ratios comparing the additional cost per improved outcome of the different intervention arms and the standard of care. We will perform sensitivity analyses to assess robustness of results.Ethics and disseminationThis economic evaluation will provide useful information to the Angolan Government and other policymakers on the most cost-effective intervention to prevent stunting in this and other comparable contexts. The protocol was approved by the República de Angola Ministério da Saúde Comité de Ética (27C.E/MINSA.INIS/2022). The findings of this study will be disseminated within academia and the wider policy sphere.Trial registration numberClinicalTrials.gov Registry (NCT05571280).
