Livia Vittori Antisari

Influence of urease and nitrification inhibitors on N losses from soils fertilized with urea

Abstract. The aim of this study was to evaluate how the N losses through volatilization and leaching from soils fertilized with urea can be affected by the application of a urease inhibitor or a urease plus a nitrification inhibitor. The experiment was carried out using lysimeters with 15N-labelled urea and N-(n-butyl) thiophosphoric triamide (NBPT) as urease inhibitor and dicyandiamide (DCD) as nitrification inhibitor, comparing three different treatments: urea alone (U), urea + NBPT (UN) and urea + NBPT + DCD (UND). Both volatilization and leaching were significantly different in the soils used, according to their physico-chemical characteristics. However, the pattern of the loss was similar: the volatilization was significantly reduced by NBPT (UN), but the presence of DCD (UND) significantly increased the loss, with respect to UN. Considering leaching, the highest amount of NO3– was lost with UND, the lowest with U. The greatest amount of N lost by leaching was soil-derived N produced by the N mineralization-immobilization turnover. We suggest that, by maintaining the NH4+ in the soils, the inhibitors, in particular DCD, caused a priming effect with a subsequent increase in the rate of soil organic matter mineralization and an extra release of soil organic N. The priming effect was real in the sandy loam (SL) soil where a net N release was observed, whereas in the clay loam (CL) soil the effect of the inhibitors was less pronounced and an apparent priming effect was observed; however, a real priming effect also cannot be excluded in this soil.

Determination of organic carbon in aqueous extracts of soils and fertilizers

Abstract A simple and accurate method for the routine determination of organic carbon in aqueous extracts of soils and fertilizers is described. Samples are oxidized for exactly 10 minutes with a mixture of 5 mL of 2N potassium dichromate plus 20 mL of concentrated sulphuric acid at 160 ± 2°C, and the excess dichromate is titrated either potentiometrically or manually with iron (II) sulphate. An appropriate correction factor (1.05) is suggested for aqueous extracts from humic acid.

Toxicity and transfer of metal oxide nanoparticles from microalgae to sea urchin larvae

Nanoparticles (NPs) contained in commercial products are released and enter into the aquatic ecosystem, posing serious possible risks to the environment and affecting the food chain. Therefore, investigating the potential toxicity of NPs on aquatic organisms has become an important issue. This study assessed the toxicity and trophic transfer of metal oxide NPs from marine microalgae (Cricosphaera elongata) to the larvae of the sea urchin Paracentrotus lividus. Larvae (24 h old) were fed on 2000 cell mL−1 48 h of microalgae contaminated with 5 mg L−1 of several metal oxide NPs (SiO2, SnO2, CeO2, Fe3O4) for 15 days. Larval viability and development were monitored from the 4-arm stage to the 8-arm pluteus stage. A significant decrease in survival was observed in larvae fed with microalgae exposed to SiO2 and CeO2 NPs. Abnormal development, characterised by skeletal degeneration and altered rudiment growth, was observed in all larvae fed with contaminated NP algae. Our findings revealed that SiO2 and CeO2 NPs exerted a toxic effect in the trophic interaction analysed, by reducing sea urchin larval viability, and all metal oxide NPs induced toxicological effects. In conclusion, metal oxide NPs may enter the food chain and become bioavailable for marine organisms, affecting their development.

Heavy metal risk assessment after oxidation of dredged sediments through speciation and availability studies in the Reno river basin, Northern Italy

PurposeThe distribution of heavy metals was investigated in sediments of both natural and artificial watercourses of the Reno river basin (Northern Italy) with the aim of assessing their pollution risk before and after dredging operations. The different solubility and availability of metals in wet and dry sediments were investigated in order to identify the main critical variables controlling metal adsorption into sediments, their speciation and, therefore, their potential environmental hazard.Materials and methodsTwenty-four sampling stations were selected in the Reno basin network, and sediment sampling was seasonally carried out in 2012–2013. Pseudo-total metal content was determined through acid digestion with aqua regia, and the geoaccumulation index (Igeo) of metals was estimated using regional mean background values. Leaching tests were carried out through partial dissolution techniques (deionized water and diethylenetriaminepentaacetic acid (DTPA) extraction) on wet and dry samples, while the speciation of metals was investigated by a five-step sequential extraction. All analyses were performed by inductively coupled plasma optical emission spectrometry (ICP-OES).Results and discussionArtificial watercourses presented higher contamination levels than natural ones, and a different pollution level was found when Igeo was applied. The sequential extraction showed that metals in river sediments are mostly immobilized in the residual phase (e.g. Cr), while in canals, weak bonds were found (e.g. Cd). The dredging of sediments, and their consequent oxidation, enhances the availability of metals according to their affinity with organic matter (e.g. Cu and Pb) or carbonates (e.g. Zn). The different remobilization rate obtained by changing the oxidation status of sediments highlighted the importance of metal availability studies for assessing and predicting their environmental hazard.ConclusionsThe effect of oxidation processes on the availability of heavy metals depends on the geogenic or anthropogenic nature of the element, on the redox status of the sediment and on the affinity of the metal with the different mineralogical phases of the sediment. In redox changing environments, the prediction of the environmental risk from metals before and after sediment land disposal gives more useful information than the knowledge of total metal concentration. The use of leaching techniques, combined with the calculation of background values, is strongly recommended for the assessment of metal hazard in sediments.

Soil–water interactions in soils of the Padanian Plain (Ferrara, Northern Italy): insights on heavy-metal mobility and phytoavailability

The soils of the Po River plain, developed on the alluvial sediments, are often characterized by high concentration of heavy metals, in particular chromium and nickel. These geochemical anomalies are “geogenic”, i.e. related to the specific nature of the “mother rocks” outcropping in the basin that typically include mafic and ultramafic lithologies. The elevated heavy metal backgrounds of soils potentially represent an effective geochemical risk considering the toxicity of these elements. In order to delineate soil quality thresholds and to provide guidelines for human activities (e.g. agriculture) the current legislation takes into consideration the “pseudototal” metal content obtained with aqua regia extraction tests. However, only a fraction of this chemical budget is available for plant and human uptake. Soil leaching tests with deionized water plausibly provide a better analogue to simulate the natural soil-water interactions, in order to predict the behavior of metals in the environment. In particular, in this paper we investigate with water leaching tests soils sampled in the surrounding of Ferrara (eastern part of the Po plain) that were previously characterized by bulk XRF analyses and aqua regia extractions. The approach gives insights on the element-specific transport parameters, giving clues for a) the possible contamination of the natural water and b) the soil-to-plant uptake processes and phytoavailability. Results, expressed as solid-water partition coefficients, highlight that nickel is significantly more mobile and bioaccessible than chromium and should be monitored in the local agricultural products to avoid its possible transfer and bioaccumulation in the food chain.

Effect of N-(n-butyl)thiophosphoric triamide added to peat and leather in urea-based fertilizers on urea hydrolysis and ammonia volatilization.

Abstract A laboratory experiment evaluated the rate of urea hydrolysis and ammonia volatilization from urea (U) mixed in organo‐mineral (O‐M) fertilizers. These fertilizers were incubated in soil in the presence or absence of N‐(n‐butyl)thiophosphoric triamide (NBPT) as a urease inhibitor. Two organic matrices, leather (L) and peat (P), were used to prepare the O‐M fertilizers. In the absence of NBPT, the highest ammonia losses and the fastest rate of urea hydrolysis were in the soil treated with the fertilizer containing leather (UL50). Significantly lower ammonia losses occurred with peat‐based fertilizers. Although the fertilizer containing peat (UP50) stimulated the rate of urea hydrolysis with respect to the urea alone, no increase in ammonia volatilization was detected. NBPT‐containing fertilizers were stored for different times (0,7, 30, and 60 days) and temperatures (25°C and 40°C), and the NBPT recovery was monitored by extraction and analysis by HPLC. The NBPT recovery decreased by increasing either the storage time or the storage temperature. Differences among the fertilizers occurred after storage at 40°C for 30 or 60 days. With UN, in spite of about 25% extracted amount of NBPT, the ammonia losses did not increase with respect to the non‐stored fertilizer. On the contrary, no inhibitor was recovered from either of the O‐M fertilizers (UNL and UNP). However, in the presence of leather, NBPT reduced the volatilization losses by 35 to 40%, whereas in the presence of peat, a complete loss of NBPT efficiency occurred. In general, either the inhibitor recovery or efficiency were affected by the storage conditions or the type of organic matrix.

Pedo-environmental evolution and agricultural landscape transformation

Landscapes represent the stage setting of the ecosystem, the great theatre where the evolution of the environment, the changing of things and plant and animal life are played out; the diversity of landscapes derives from the combination, over time, of different environmental factors having perceptibly different roles, as in the case of climate, vegetation and human activity. Less perceptible and scarcely known is the role of soil, which has the ability not only to diversify the ecosystem’s landscapes but also to differentiate its level of productivity and liveability. The role of soil as part of the landscape is not always so evident, especially when it is covered by vegetation that precludes observation. At times, however, soils show themselves conspicuously, at least on the surface, when the colours of the epipedons invade the landscape and – in the ploughing season – dominate it. While it may be reassuring to see neatly cultivated fields and crops growing luxuriantly and homogeneously, the increasingly marked and evident signs of soil degradation or erosion are a cause for concern. In the recent past, the relationship between man and soil resources was strongly influenced by natural factors inside and outside the soil itself, socio-economic conditions and above all the labour force, i.e. the people employed in the primary sector; consequently, it was based on such factors that crop-growing choices were adapted to the different ecosystems, resulting in a diversification of rural landscapes. Starting from the second half of the twentieth century, the introduction of chemicals, mechanisation and exploitation of various forms of energy drastically transformed land use in the space of just a few years, with a logic aimed at improving the production capacity of farmland and forest land in both qualitative and quantitative terms. As a consequence, farming choices that were formerly adapted to the natural and socio-economic conditions of different ecosystems are now “imposed” through investments and the use of considerable energy resources, where little account is taken of the actual sustainability of soil use or the progressive loss of natural fertility; moreover, the rural landscape, by virtue of an increasingly intense and localised single-crop specialisation, has become organised into areas displaying a uniform, regular and often monotonous appearance. However, the greatest source of worry lies in the progressive consumption of soil, which particularly affects flatlands and low hills. This phenomenon is tied not only to the relentless expansion of developed areas, but also to an irrational distribution of residential, industrial and commercial property, resulting in the segmentation and fragmentation of farmland. An irreversible trend that risks destroying the already fragile identity of the rural landscape completely.