Temperature sensitivity of the turnover times of soil organic matter in forests.

Soils represent the largest carbon pool in the terrestrial biosphere, and climate change might affect the main carbon fluxes associated with this pool. These fluxes are the production of aboveground litter and root litter, and decomposition of the soil organic matter (SOM) pool by soil microorganisms. Knowledge about the temperature sensitivity of the decomposition of different SOM fractions is crucial in order to understand how climate change might affect carbon storage in soils. In this study, the temperature sensitivity of the turnover times of three different SOM fractions (labile, intermediate, and stabilized) was investigated for 11 forest sites along a temperature gradient. Carbon-14 isotope analyses of the SOM fractions combined with a model provided estimates of their turnover times. The turnover times of the labile SOM fraction were not correlated with mean annual soil temperature. Therefore it was not possible to estimate temperature sensitivity for the labile SOM fraction. Given considerable evidence elsewhere for significant temperature sensitivities of labile SOM, lack of temperature sensitivity here most likely indicates limitations of the applied methodology for the labile SOM fraction. The turnover times of the intermediate and the stabilized SOM fractions were both correlated with mean annual soil temperatures. The temperature sensitivity of the stabilized SOM fraction was at least equal to that of the intermediate SOM fraction and possibly more than twice as high. A correction for confounding effects of soil acidity and clay content on the temperature sensitivities of the intermediate and stabilized SOM fractions was included in the analysis. The results as observed here for the three SOM fractions may have been influenced by (1) modeling assumptions for the estimation of SOM turnover times of leaf and needle longevities, constant annual carbon inputs, and steady-state SOM pools, (2) the occurrence of summer drought at some sites, (3) differences between sites in quality of the SOM fractions, or (4) the relatively small temperature range. Our results suggested that a 1 degree C increase in temperature could lead to decreases in turnover times of 4-11% and 8-16%, for the intermediate and stabilized SOM fractions, respectively.     

A numerical (LES) investigation of a shallow-water, mid-latitude, tidally-driven boundary layer

We investigate turbulent mixing in a tidally driven, mid-latitude, shallow-water basin. The study is carried out numerically at a laboratory-scale, using large-eddy simulation. We compared the results of the simulation with those of a correspondent purely oscillatory flow (Stokes boundary layer). The effect of rotation on the flow dynamics is twofold. First, rotation gives rise to a mean spanwise flow that concurs to redistribute the turbulent energy among the Reynolds stresses, in particular between the horizontal directions, thus increasing the mixing across the water column and thickening the layer where developed turbulence is observable. Second, the presence of the horizontal component of the background vorticity (latitude effect) breaks the symmetry between the two semi-cycles of the oscillation, since turbulence results suppressed/enhanced during the first/second semi-cycle. These two effects significantly modify the turbulent characteristics with respect to the purely oscillating flow, although the mechanisms that generates turbulence present similar features. The qualitative agreement between our results and some measurements carried out in two sites with characteristics similar to the case analyzed suggests that the outcomes here provided may be of general use for the analysis of mid-latitude, neutrally stratified, shallow-water basins mainly driven by semi-diurnal tidal currents.     

Particulate matter characterization at a coastal site in south-eastern Italy

Several samples of airborne particulate matter (PM), collected from 6th November to 6th December 2003 at a coastal site in the south-east of Italy, have been analyzed by different techniques to characterize elemental composition and morphological properties of the inorganic PM fraction and obtain preliminary results on anthropogenic contributions. Al, Cr, Cu, Fe, Mn, V, Pb, Ti, Ca and Zn mass concentrations, evaluated by an inductively coupled plasma atomic emission spectrometer, account for up to l% of the bulk PM mass in the investigated samples. According to geochemical calculations, Ca, Al, Fe and Mn are predominantly of crustal origin, while Cr, Cu, Pb, V, Ti and Zn heavy metals are of anthropogenic origin. Ion chromatography analyses have identified sulfate (SO(4)(2-)) nitrate (NO(3)(-)), sodium (Na(+)), and ammonium (NH(4)(+)) as the main ionic components accounting for up to 38% of the total PM mass and up to 90% of the total ionic mass. Besides ion chromatography, X-ray energy dispersive (EDX) microanalyses have revealed the high variability of Cl: its weight concentration varies from about 24% to below the detection limit (>or=0.5%) in the investigated samples. The marked anti-correlation between the excess of S and the Cl/Na ratio has allowed inferring that reactions between sea salt particles and acidic sulfates, which liberate HCl gas to the atmosphere leaving particles enriched in non-sea-salt sulfates, have significantly contributed to chloride depletion. Morphological analyses by scanning electron microscopy have shown that about 90% of the total sampled particles have a diameter 相似文献   

Oceanographic and biogeochemical drivers cause divergent trends in the nitrogen isoscape in a changing Arctic Ocean

Nitrogen stable isotopes (δ¹⁵N) are used to study food web and foraging dynamics due to the step-wise enrichment of tissues with increasing trophic level, but they rely on the isoscape baseline that varies markedly in the Arctic due to the interplay between Atlantic- and Pacific-origin waters. Using a hierarchy of simulations with a state-of-the-art ocean-biogeochemical model, we demonstrate that the canonical isotopic gradient of 2–3‰ between the Pacific and Atlantic sectors of the Arctic Ocean has grown to 3–4‰ and will continue to expand under a high emissions climate change scenario by the end of the twenty-first century. δ¹⁵N increases in the Pacific-influenced high Arctic due to increased primary production, while Atlantic sector decreases result from the integrated effects of Atlantic inflow and anthropogenic inputs. While these trends will complicate longitudinal food web studies using δ¹⁵N, they may aid those focussed on movement as the Arctic isoscape becomes more regionally distinct.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01635-6.     

Maltooligosaccharides in the northwestern Adriatic Sea

The aim of this study was to monitor for the first time the oligosaccharide pattern in the northwestern Adriatic Sea. Oligosaccharides are components of the low-molecular-weight fraction of dissolved organic matter (DOM). They perform an important ecological function in the microbial loop prompting substrates for bacterial degradation. In particular, our investigation focused on maltooligosaccharides (glucose α 1–4 linked). The analyses were carried out using a dialysis-charcoal column sorption pre-concentration method, followed by liquid chromatography-tandem mass spectrometry analyses with a triple quadrupole mass spectrometer operating in multiple reaction monitoring mode. During the study period, the concentration of maltooligosaccharides with a low degree of polymerisation (ranging from maltose to maltotetraose) was higher than other maltooligosaccharides (maltopentaose and maltoeptaose) and all together they reached their highest concentration in June. This concentration was temporally shifted from a long period of diatom bloom (from January to April). Furthermore, the annual maltooligosaccharide trend was monitored together with several chemical, physical and biological parameters to investigate their potential role on the maltooligosaccharide accumulation. Our results suggested that the maltooligosaccharide accumulation could be related to the water column stratification.     

Co-polymerization of penta-halogenated phenols in humic substances by catalytic oxidation using biomimetic catalysis

Introduction

A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride, Fe-(TDCPPS)Cl, was employed to catalyze the oxidative co-polymerization of penta-halogenated phenols in two humic materials of different origin.

Materials and methods

Co-polymerization of pentachlorophenol (PCP) was followed by high-performance size-exclusion chromatography (HPSEC), the unbound PCP recovered from reacting humic solutions was evaluated by gas-chromatography/electron capture detector, and the oxidative catalyzed coupling of pentafluorophenol (PFP) into humic matter was assessed by liquid-state ¹⁹F-NMR spectroscopy. HPSEC showed that the catalyzed oxidative coupling between PCP and humic molecules increased the apparent weight-average molecular weight (M _w) values in both humic substances.

Results and discussion

HPSEC further indicated that the co-polymerization reaction turned the loosely bound humic supramolecular structures into more stable conformations, which could no longer be disrupted by the disaggregating effect of acetic acid. The occurrence of covalent linkages established between PCP and humic molecules was also suggested by the very little amount of PCP found free in solution after the catalyzed co-polymerization. ¹⁹F-NMR spectroscopy suggested that also PFP could be oxidatively coupled to humic materials. PFP-humic co-polymerization reaction produced ¹⁹F-spectra with many more ¹⁹F signals and wider chemical shifts spread than for PFP alone or PFP subjected to catalyzed coupling without humic matter.

Conclusions

These findings show that biomimetic iron-porphyrin is an efficient catalyst for the covalent binding of polyhalogenated phenols to humic molecules, thereby suggesting that the co-polymerization reaction may become a useful technology to remediate soils and waters contaminated by polyhalogenated phenols and their analogues.     

End-of-Life Vehicles management: Italian material and energy recovery efficiency

Each European Member State must comply with Directive 2000/53/EC recycling and recovery targets by 2015, set to 85% and 95%, respectively. This paper reports a shredder campaign trial developed and performed in Italy at the beginning of 2008. It turns out to be the first assessment about the critical aspects belonging to the Italian End-of-Life Vehicles (ELVs) reverse supply chain involving 18 dismantling plants, a shredder plant and 630 ELV representatives of different categories of vehicles treated in Italy during 2006. This trial aims at improving the experimental knowledge related to ELVs added waste, pre-treatment, part reuse, recycling and final metal separation and car fluff disposal. Finally, the study also focuses on the calculation of the effective Italian ELV recycling rate, which results equal to 80.8%, and auto shredder residue (ASR) characterization. According to the results obtained in this work, ASR still contains up to 8% of metals and 40% of polymers that could be recovered. Moreover, physical-chemical analysis showed a Lower Heat Value of almost 20,000 kJ/kg and revealed the presence of pollutants such as heavy metals, mineral oils, PCBs and hydrocarbons.     

Material and energy recovery in integrated waste management systems: a life-cycle costing approach

A critical assumption of studies assessing comparatively waste management options concerns the constant average cost for selective collection regardless the source separation level (SSL) reached, and the neglect of the mass constraint. The present study compares alternative waste management scenarios through the development of a desktop model that tries to remove the above assumption. Several alternative scenarios based on different combinations of energy and materials recovery are applied to two imaginary areas modelled in order to represent a typical Northern Italian setting. External costs and benefits implied by scenarios are also considered. Scenarios are compared on the base of the full cost for treating the total waste generated in the area. The model investigates the factors that influence the relative convenience of alternative scenarios.     

Ecological footprint analysis applied to a sub-national area: the case of the Province of Siena (Italy)

This work is part of a larger project, which aims at investigating the environmental sustainability of the Province of Siena and of its communes, by means of different indicators and methods of analysis. The research presented in this article uses ecological footprint and biocapacity as indicators to monitor the environmental conditions of the area of Siena, thus complementing previous studies carried out using Emergy, greenhouse gases balance and other methods. The calculations have been performed in such a way as to enable a disaggregation of the final results according to the classical categories of ecologically productive land and of consumption, but also according to citizen's and public administration's areas of influence. This information allows us to investigate in detail the socio-economic aspects of environmental resource use. Among the notable results, the Siena territory is characterized by a nearly breakeven total ecological balance, a result contrasting with the national average and most of the other Italian provinces. Furthermore, the analysis has been carried out at different spatial scales (province, districts and communes), highlighting an inhomogeneous territorial structure consisting of subareas in ecological deficit compensated by zones in ecological surplus.