Alberto Masaguer

Chemical characterization and evaluation of composts as organic amendments for immobilizing cadmium.

The ability of three composted materials to immobilize cadmium (Cd) was examined in order to assess their potential for recovering soils contaminated with this metal. Composted pine bark (PB) pH 5.6, spent mushroom compost (SM) pH 8.0, and composted pruning waste+biosolids (BS) pH 6.9 (containing 81%, 75% and 47% total organic matter, respectively) were characterized. FT-IR and CP-MAS (13)C NMR spectroscopy indicated the BS and SM to have a higher percentage of aliphatic and carboxyl groups than PB. The composts were artificially contaminated with Cd (80 and 200 mg kg(-1)) and, after 4 weeks incubation, subjected to sequential extraction. In column leaching experiments, the total Cd leached from the composts exposed to both Cd treatments was similar, but much less leached from the BS (0.2%) than the PB (4.0%) or SM (0.7%). The greater capacity of BS to immobilize Cd was attributed to the greater humification of its organic matter and higher content of inorganic components, particularly Fe.

Soluble organic carbon and pH of organic amendments affect metal mobility and chemical speciation in mine soils

We evaluated the effects of pH and soluble organic carbon affected by organic amendments on metal mobility to find out the optimal conditions for their application in the stabilization of metals in mine soils. Soil samples (pH 5.5-6.2) were mixed with 0, 30 and 60 th a(-1) of sheep-horse manure (pH 9.4) and pine bark compost (pH 5.7). A single-step extraction procedure was performed using 0.005 M CaCl2 adjusted to pH 4.0-7.0 and metal speciation in soil solution was simulated using NICA-Donnan model. Sheep-horse manure reduced exchangeable metal concentrations (up to 71% Cu, 75% Zn) due to its high pH and degree of maturity, whereas pine bark increased them (32% Cu, 33% Zn). However, at increasing dose and hence pH, sheep-horse manure increased soluble Cu because of higher soluble organic carbon, whereas soluble Cu and organic carbon increased at increasing dose and correspondingly decreasing pH in pine bark and non-amended treatments. Near the native pH of these soils (at pH 5.8-6.3), with small doses of amendments, there was minimum soluble Cu and organic carbon. Pine bark also increased Zn solubility, whereas sheep-horse manure reduced it as soluble Zn always decreased with increasing pH. Sheep-horse manure also reduced the proportion of free metals in soil solution (from 41% to 4% Cu, from 97% to 94% Zn), which are considered to be more bioavailable than organic species. Sheep-horse manure amendment could be efficiently used for the stabilization of metals with low risk of leaching to groundwater at low doses and at relatively low pH, such as the native pH of mine soils.

Chemical speciation and mobilization of copper and zinc in naturally contaminated mine soils with citric and tartaric acids.

A one-step extraction procedure and a leaching column experiment were performed to assess the effects of citric and tartaric acids on Cu and Zn mobilization in naturally contaminated mine soils to facilitate assisted phytoextraction. A speciation modeling of the soil solution and the metal fractionation of soils were performed to elucidate the chemical processes that affected metal desorption by organic acids. Different extracting solutions were prepared, all of which contained 0.01 M KNO(3) and different concentrations of organic acids: control without organic acids, 0.5 mM citric, 0.5 mM tartaric, 10 mM citric, 10 mM tartaric, and 5 mM citric +5 mM tartaric. The results of the extraction procedure showed that higher concentrations of organic acids increased metal desorption, and citric acid was more effective at facilitating metal desorption than tartaric acid. Metal desorption was mainly influenced by the decreasing pH and the dissolution of Fe and Mn oxides, not by the formation of soluble metal-organic complexes as was predicted by the speciation modeling. The results of the column study reported that low concentrations of organic acids did not significantly increase metal mobilization and that higher doses were also not able to mobilize Zn. However, 5-10 mM citric acid significantly promoted Cu mobilization (from 1 mg kg(-1) in the control to 42 mg kg(-1) with 10 mM citric acid) and reduced the exchangeable (from 21 to 3 mg kg(-1)) and the Fe and Mn oxides (from 443 to 277 mg kg(-1)) fractions. Citric acid could efficiently facilitate assisted phytoextraction techniques.

Dynamics of pruning waste and spent horse litter co-composting as determined by chemical parameters

Co-composting of pruning waste and horse manure was monitored by different parameters. A windrow composting pile, having the dimensions 2.5m (height) x 30m (length) was established. The maturation of pruning waste and horse manure compost was accompanied by a decline in NH(4)(+)-N concentration, water soluble C and an increase in NO(3)(-)-N content. Organic matter (OM) content during composting followed a first-order kinetic equation. This result was in agreement with the microbiological activity measured by the CO(2) respiration during the process. The correlation at a high level of probability found between the OM loss and CO(2) evolution showed that both parameters could be used to indicate the degree of OM degradation that is the maturity and stability phases of the compost studied. Humification parameters data from the organic matter fractionation did not show a clear tendency during the composting time, suggesting that these parameters are not suitable for evaluating the dynamics of the process.

Phytoextraction of Cadmium by Four Mediterranean Shrub Species

The possibility of remediating contaminated soils though the use of high biomass-generating, native plant species capable of removing heavy metals is receiving increased attention. The cadmium (Cd) accumulation capacities of the native Mediterranean, perennial shrubs Atriplex halimus, Phyllirea angustifolia, Rhamnus alaternus and Rosmarinus officinalis were tested by growing transplanted specimens in a pine bark compost substrate (pH 5.6) contaminated with 100 mg Cd kg−1. After 70 days, only R. alaternus showed reduced growth. The increase in biomass seen in all the test species enhanced the phytoextraction of Cd. However, the species behaved as metal excluders, except for the halophyte A. halimus, which behaved as an indicator plant. In this species the leaf Cd concentration reached 35 mg Cd kg−1, with the shoot responsible for some 86% of total Cd accumulation. Atriplex halimus showed the highest bioconcentration factor (BCF) (0.36) and leaf Cd transport index (1.68); consequently, this species showed the highest Cd phytoextraction capacity.

Carbon Mineralization of Pruning Wastes Compost At Different Stages of Composting

To study the carbon mineralization of pruning waste compost, four samples originated from pruning waste, leaves and grass clippings were collected each from a different pilot pile at different stage of the composting process: initial nondecomposed material (C1); two-months old at the end of the biooxidative stage (C2); seven months old during the curing phase (C3) and 12 months old at the end of the curing phase (C4). The CO2-C evolution was measured during 56 days of aerobic incubation. The proportion mineralized from the different composts (% of compost TOC) during the incubation period were: 4.54, 2.43, 1.71 and 1.60 for C1, C2, C3 y C4, respectively. Regardless of compost age, C mineralization occurred in two phases: a first rapid phase (corresponding to the decomposition of the most labile products by microorganisms) and a second, slower phase, during which the most resistant organic products mineralized. During the first stage, the model was fitted to a first-order equation, whereas in the second phase the model was a zero-order equation. Because of the similar results obtained for samples C3 and C4, we can conclude that organic matter had similar microbial stability at both stages and the composting process could be shortened by five months.

Comparison of a gas detection tubes test with the traditional alkaline trap method to evaluate compost stability

Compost stability is an important parameter of compost quality. Among tests proposed to evaluate compost stability, microbial respiration is one of the better accepted tests. Variations in rates of CO2 evolution during composting were studied in two pilot pruning waste piles using a windrow composting system. To measure the CO2 production rate, two methods were compared: the alkaline trap test and gas detection tubes. Both respiration tests indicated increasing compost stability with processing time, but CO2 evolution rates from the alkaline trap method were higher than values from the gas detection tube method. A first-order kinetic equation was used to describe CO2 evolution over time. A linear relationship (r=0.81, p<0.01) was found between the two methods. Although both methods could distinguish unstable compost from stable compost, CO2 detection tubes were easier to use and gave results in a shorter period of time.

Study of conifer nitrogen nutrition using hydroponic cultures: Application to fertigation systems

Abstract Nitrogen (N) optimization of a nutrient solution for ornamental conifers was obtained with two different experiments in hydroponic cultures: First, by using three different NO3 ‐/NH4 + ratios (60/40, 55/45, and 40/60 in percentages of the total N supplied); and, secondly by testing three total N levels (3.7; 4.7 and 5.5 mmol L‐1). Best growth was obtained with a NO3 ‐/NH4 + ratio of 55/ 45 and a total N level of 3.7 mmol L‐1. With these experiments, reference levels of foliar concentrations of the macronutrients N, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and the biochemical indices, such as chlorophyll and starch levels, were obtained with the treatments corresponding to the plants with the higher growth. In the course of a growth cycle, a substrate assay with two different pot mixes (moss peat plus perlite and black peat plus sepiolite 60/40 ‐% v/v‐) was carried out by using the best N ratios and doses in nutrient solutions as obtained in hydroponics. The results indicated that the same N fertilization in fertigation systems changes depending on the different physicochemical properties of the substrates used; in this case, depending on the different physical properties of the two substrates. By applying DRIS to perform nutritional diagnosis, it is possible to find nutritional limitations to plant growth, but not additional factors, such as water‐air relationships in the growth media.

Urban Lawn Monitoring in Smart City Environments

The control of water usage for irrigation purposes is a key factor in order to achieve the sustainability in the agriculture. The irrigation of urban lawns supposes a high percentage in the urban water usage. The use of Information and Communication Technology (ICT) offers the possibility of monitoring the grass state in order to adjust the irrigation regime. In this paper, we propose an Arduino-based system with a camera set on a drone. The drone flies along the garden taking pictures of the grass. Those pictures are processed with a rule-based algorithm that classifies them according to the grass quality. Three different categories can be tagged to the picture, high coverage, low coverage or very low coverage. After designing our algorithm, twelve pictures are used to verify its correct operation. The results show a 100% hit rate. To analyse the suitability of using drones to perform this task, we carry out a comparative study for gardens with different size where the drone and other similar system mounted on a small autonomous vehicle have been used. The results show that, for gardens higher than 1,000 m2 the use of drone is needed due to the time consumed by the vehicle to cover the entire surface. Finally, the study concludes with a comparative regarding to the amount of information sent through the network.

Phytoremediation of Degraded Mine Soils Using Organic Amendments and Metal-Tolerant Plants

Mine soils usually contain high levels of metal contamination and poor fertility conditions which limit their restoration and the establishment of vegetation. In this work, we reported our previous results of the use of organic amendments (horse and sheep manure compost and pine bark compost) and metal-tolerant plants (Atriplex halimus, Brassica juncea, and Thlaspi arvense) for the phytoremediation of mine soils. Greenhouse and laboratory experiments were performed with soil samples collected from two abandoned mine sites of Central Spain mixed with 0, 30, and 60 t ha−1 of the organic amendments to evaluate the growth, tolerance, metal accumulation, and translocation of these plants in relation to metal bioavailability and soil conditions affected by the organic amendments. Our results showed that manure reduced metal availability and improved soil fertility due to its high pH, organic matter nature, and nutrient contents, stabilizing metals in soil and allowing a higher plant growth and even a greater amount of metals removed from soils and accumulated in plant tissues, which enhance the phytoremediation capacity of these plants. A. halimus and B. juncea achieved high biomass production and metal accumulation without being severely affected by metal toxicity, but their capacity was insufficient for the phytoextraction of metals in the short to medium term in these soils. However, the use of both species could be a useful and cost-effective practice for the phytostabilization of mine soils in combination with manure amendments.