Pedro Soler-Rovira

Long-term effects of municipal solid waste compost application on soil enzyme activities and microbial biomass

A long-term field experiment utilising barley received four different treatments prior to sowing: municipal solid waste (MSW) compost at either 20 t ha 21 (C20) or 80 t ha 21 (C80); cow manure (MA) at 20 t ha 21 ; mineral fertilizer (MIN) or NPK (400 kg ha 21 ); and NH4NO3 (150 kg ha 21 ). The effects of these applications on soil enzyme activities and microbial biomass at crop harvest were measured after nine years. In comparison with the control (no amendment) MSW addition increased biomass C by 10 and 46% at application rates of 20 and 80 t ha 21 , respectively, while MA treatment increased microbial biomass C by 29%. The ratio of soil microbial C to soil organic C was the lowest at the high rate of MSW application. Oxidoreductase enzymes, such as dehydrogenase and catalase, were higher in the MSW treatments by 730 (C20) and 200% (C80), respectively, and by 993 and 140% in MA treatments than in the unamended soil, indicating an increase in the microbial metabolism in the soil as a result of the mineralization of biodegradable C fractions contained in the amendments. The addition of MSW and MA caused different responses in hydrolase enzymes. Phosphatase activity decreased with MSW (^62% at both rates) and MA (^73%), to less than those in the mineral fertilization and the control treatments. Urease activity decreased by 21% (C20) and 28% (C80), possibly being affected by the heavy metals contained in the MSW. However,b-glucosidase and protease-BAA increased in all the organic treatments, especially with MA (by 214 and 177%, respectively). This is attributed to the microbial stimulation by the organic C and is correlated with the increase in dehydrogenase Or 2 a 0:882U and catalaseOr 2 a 0:654U activities. q 2000 Elsevier Science Ltd. All

In situ remediation of metal-contaminated soils with organic amendments: role of humic acids in copper bioavailability

The purposes of this study were to determine the Cu(II) binding behavior of humic acids (HAs) isolated from biosolid compost (BI), leonardite (LE), a metal-contaminated soil, and the soil remediated with either BI or LE in relation to their structural properties, and to explore the role exerted by the HA fractions in controlling soil Cu(II) bioavailability. Potentiometric titrations at pH 5 and ionic strength 0.1M and the Langmuir model were used to obtain the Cu(II) complexing capacity of the HAs examined and the conditional stability constant of the Cu(II)-HA complexes. The Cu(II) complexing capacity increased as the content of acidic ligands, especially COOH groups, aromaticity, and humification degree increased, following the order BI-HA<BI-amended soil HAs<unamended soil HA<LE-amended soil HAs<LE-HA. In contrast, the conditional stability constant of Cu(II)-HA complexes increased in the opposite order, probably due to an increased chelating effect. Compared to LE, amendment with BI was slightly more effective in decreasing soil CaCl(2)-extractable Cu content. The results obtained suggested that the pH of the soil-amendment system is the most important chemical property governing Cu(II) solubility and bioavailability in metal-contaminated soils remediated with BI and LE, although soil organic matter and the HA fraction may also be important factors. In particular, binding sites formed by N-, S-, and O-containing acidic functional moieties in HAs may play an important role in the Cu(II) behavior.

Short-term effects of organic municipal wastes on wheat yield, microbial biomass, microbial activity, and chemical properties of soil

The objectives of this work were to (a) investigate the short-term effects of applications of mineral fertilizer, municipal solid waste (MSW) compost, and two sewage sludges (SSs) subjected to different treatments (composting and thermal drying) on microbial biomass and activity of soil by measuring microbial biomass C, adenosine 5′-triphosphate content, basal respiration, and dehydrogenase, catalase, urease, phosphatase, β-glucosidase, and N-α-benzoyl-l-argininamide-hydrolyzing activities and (b) explore the relationships between soil microbiological, biochemical, and chemical properties and wheat yields under semiarid field conditions by principal component analysis. The additions of MSW compost, SS compost, and thermally dried SS did not affect significantly soil microbial biomass, as compared to mineral fertilization and no amendment. However, microbial activity increased in organically amended soils, probably due to the stimulating effect of the added decomposing organic matter. Changes in soil microbiological and biochemical properties showed no significant relationships with wheat yields, probably because plant growth was primarily water-limited, as typically occurs in semiarid regions.

Tolerance and accumulation of heavy metals by wild plant species grown in contaminated soils in Apulia region, Southern Italy

Many sites inside a protected area in Apulia region (Italy) have been contaminated with heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) because an inadequate disposal of a variety of wastes with different sources of origin. As first measure in-situ phytoremediation techniques were evaluated using only the natural plants that grew wildly on the contaminated soils, in order to minimize the environmental impact on this fragile ecosystem. Total contents of metals in soils generally exceeded the maximum levels indicated in Italian and European regulations, specially Cr and Zn. Although the extractable fraction was element-dependent, the metal immobilization was enhanced by the components of soils. Maximum mobilizable fractions (%DTPA of total content) were 30% Cd, 0.01% Cr, 11.5% Cu, 4.1% Ni, 13.3% Pb and 13.8% Zn. The general trend of metal accumulation in plants was Zn > Cu > Cr > Pb > Ni > Cd and statically accumulation differences were found to largely depend on plant species. Thus different metal uptake and translocation strategies were suggested in the studied species: exclusion for Stipa austroitalica and Dasypyrum villosum, whereas tolerance mechanisms for Carduus pycnocephalus, Silybum marianum and Sinapis arvensis. The metal contents in above ground parts of these species were within the values of normal in plants and below phytotoxic levels, thus faraway from phytoextraction applicability. These species can be considered as metal excluder or tolerant plants with ability of growing in soils with a wide range of heavy metal concentrations, mainly immobilized by soil conditions. Thus they accomplished the criteria to be considered for phytostabilization technique in these contaminated sites.

Influence of humified organic matter on copper behavior in acid polluted soils

The main purpose of this work was to identify the role of soil humic acids (HAs) in controlling the behavior of Cu(II) in vineyard soils by exploring the relationship between the chemical and binding properties of HA fractions and those of soil as a whole. The study was conducted on soils with a sandy loam texture, pH 4.3-5.0, a carbon content of 12.4-41.0gkg(-1) and Cu concentrations from 11 to 666mgkg(-1). The metal complexing capacity of HA extracts obtained from the soils ranged from 0.69 to 1.02molkg(-1), and the stability constants for the metal ion-HA complexes formed, logK, from 5.07 to 5.36. Organic matter-quality related characteristics had little influence on Cu adsorption in acid soils, especially if compared with pH, the degree of Cu saturation and the amount of soil organic matter.

Composition and structural characteristics of humified fractions during the co-composting process of spent mushroom substrate and wheat straw.

A spent mushroom substrate (SMS) was mixed with wheat straw (WS) in three proportions, C1 (2:1), C2 (4:1), and C3 (6:1), and composted for 90 days in static piles with periodic turning to ensure adequate aeration. Samples from each pile were collected periodically (after 0, 30, 60, and 90 days), and the humic acid-like fractions (HAs) were isolated to determine their elemental composition (C, H, N, S, and O), acidic functional group (carboxylic and phenolic) content, and structural and functional characteristics using spectroscopic methods including ultraviolet-visible, Fourier transform infrared (FTIR), and fluorescence. The results of elemental and functional group analyses show that, with increasing time of composting, the N, O, and acidic functional group contents of HAs increase, whereas their C and H contents and C/N ratio decrease. The analysis of FTIR and fluorescence spectra shows that, with increasing composting time, the presence of aliphatic and polysaccharide-like structures in HAs decreases, whereas oxygenation, polycondensation, and polymerization increase. These results suggest that the chemical and structural characteristics of the HA fractions in the final composts resemble those typical of native soil HAs, which indicate that an adequate degree of maturity and stability is achieved after the end of composting. The results of the present study confirm that composting is an appropriate treatment to transform fresh organic matter (OM) in SMS into humified forms, thus enhancing their quality, agronomic efficiency, and environmental safety as a soil OM resource for application as soil amendment.

Variability in As, Ca, Cr, K, Mn, Sr, and Ti concentrations among humic acids isolated from peat using NaOH, Na4P2O7 and NaOH+Na4P2O7 solutions

Sphagnum peat has been found to efficiently remove heavy metals, oil, detergents, dyes, pesticides and nutrients from contaminated waters since its major constituents, i.e., unesterified polyuronic acids, cellulose, and fulvic and humic acids (HA), show functional groups (e.g., alcohols, aldehydes, carboxylic acids, ketones and phenolic hydroxides) which may adsorb pollutant species. The influence of the extractant on the analytical characteristics of HA is an old but still open topic that should be studied in relation to the nature of the matrix from which they originate. While a number of works have been published on the effects of different reagents on the extraction yields and structural properties of HA from soils, relatively little attention has been devoted to peat HA. In this work, the contents of some major and trace elements (As, Ca, Cr, K, Mn, Sr, and Ti) in five Sphagnum-peat samples and in their corresponding HA fractions isolated using three common extractant solutions, i.e., 0.5M NaOH, 0.1M Na(4)P(2)O(7), and 0.5M NaOH+0.1M Na(4)P(2)O(7), where investigated by X-ray fluorescence spectroscopy. In general, Cr, Mn, and Ti concentrations of bulk peat samples were higher than those of the corresponding HA fractions regardless of the extractant used. Arsenic, Ca, K, and Sr concentrations in the HA fractions were affected by the extraction procedure, although at different extents depending on the extractant utilized. In particular, compared to both NaOH and NaOH+Na(4)P(2)O(7), the Na(4)P(2)O(7) extractant yielded HA generally richer in As, Ca, K, and Sr, and poorer in Ti. These results may be related to both the nature of each HA fraction and the physical and chemical form of each element supplied to the studied bog via atmospheric deposition.

Heavy metals accumulation and distribution in durum wheat and barley grown in contaminated soils under Mediterranean field conditions

Abstract In the framework of a phytoremediation project in the Apulia region (Italy) a field experiment was carried out in multi-metal contaminated soils. The accumulation and distribution of metals in different plant parts of durum wheat and barley were studied. Further, the application of Bacillus licheniformis strain BLMB1 to soil was evaluated as a means to enhance metal accumulation in plants. The translocation and the bioconcentration factors indicated that wheat and barley do not act as metal accumulators in the field conditions tested, thus phytoextraction by these species would not be recommended as a soil remediation alternative. Application of B. licheniformis improved the accumulation of all metals in roots of wheat and barley, and increased Cd, Cr, and Pb contents in the shoots of barley. Low health risk for humans and animals was evaluated to exist if straw and grain from both cereal crops grown in these contaminated sites are consumed.

Respiration parameters determined by the ISO-17155 method as potential indicators of copper pollution in vineyard soils after long-term fungicide treatment

This study seeks to determine the impact of copper-based fungicides on the respiration of vineyard soils. The ISO-17155 is an international standard recommended for monitoring soil quality by the evaluation of the effects of pollutants on soil microbial activity. Respiration curves and derived parameters [i.e., basal respiration (RB), substrate-induced respiration (RS), lag time (tlag), growth rate (μ), time to the peak maximum (tpeakmax), respiratory-activation quotient (QR), and the cumulative O2 consumption (CR)] were determined from 95 vineyard soils that covered a wide range of Cu contents. Statistical analyses showed that most of the variance of the ISO-17155 parameters was due to soil pH and organic C content, but not to the Cu pollution. When the parameters were expressed as a function of soil organic C content, the effect of soil Cu content was found to be significant on RS and tpeakmax but not on RB and CR. The results indicated that threshold values of total (CuT) and exchangeable (CuEX) contents indicative of soil Cu pollution cannot be established. However, adequate management practices resulting in soil organic C contents>2% and pH>5.5 are recommended for preserving vineyard soil quality.