Dynamics of soil organic matter in primary and secondary forest succession on sandy soils in The Netherlands: An application of the ROMUL model

We applied the simulation model ROMUL of soil organic matter dynamics in order to analyse and predict forest soil organic matter (SOM) changes following stand growth and also to identify gaps of data and modelling problems. SOM build-up was analysed (a) from bare sand to forest soil during a primary succession in Scots pine forest and (b) on mature forest soil under Douglas fir plantations as an example of secondary succession in The Netherlands. As some of the experimental data were unreliable we compiled a set of various scenarios with different soil moisture regime, initial SOM pools and amount and quality of above and below ground litter input. This allowed us to find the scenarios that reflect the SOM dynamics more realistically. In the Scots pine forest, total litter input was estimated as 0.50 kg m⁻² year⁻¹. Two scenarios were defined for the test runs: (a) forest floor moisture regimes—‘dry, mesic and hydric’ and (b) augmenting a root litter pool with three ratios of needles and branches to roots: 1:1, 1:1.5 and 1:2.0. The scenario finally compiled had the following characteristics: (a) climate for dry site with summer drought and high winter moisture of forest floor; (b) a litter input of 0.25 kg m⁻² year⁻¹ above ground and 0.50 kg m⁻² year⁻¹ below ground; (c) a low nitrogen and ash content in all litter fall fractions. The test runs for the estimation of the initial SOM pools and the amount and proportion of above and below ground litter fall were also performed in the Douglas fir plantation. The inputs of above ground litter tested in various combinations were 0.30 and 0.60 kg m⁻² year⁻¹, and below ground litter 0.30, 0.60 and 0.90 kg m⁻² year⁻¹. The scenario that fitted the experimental data had an SOM pool of 20–25 kg m⁻², an aboveground litter input of 0.6 kg m⁻² year⁻¹and a below ground litter input of 0.9 kg m⁻² year⁻¹. The long-term simulation corresponded well with the observed patterns of soil organic matter accumulation associated with the forest soil development in primary and secondary succession. During primary succession in Scots pine forest on dry sand there is a consistent accumulation of a raw humus forest floor. The soil dynamics in the Douglas fir plantation also coincide with the observed patterns of SOM changes during the secondary succession, with SOM decreasing significantly under young forest, and SOM being restored in the older stands.     

Chemical dechlorination of polychlorinated biphenyls (PCBs) from dielectric oils

We studied the chemical dechlorination of the polychlorinated biphenyls (PCBs) in some dielectric oils via nucleophilic substitution of the chloro atoms by polyethylene alkoxide. The influence of temperature, ultrasounds, polyethylene glycol (PEG) and base type was investigated. Our findings show that dechlorination of PCBs by chemical treatment is effective at moderate temperature (90–100°C) and is strongly dependent on the nature of matrix oil. Stirring affects the process yield by influencing the homogeneity of the oil/glycol two-phase system. Ultrasounds can improve the process efficiency by making operating conditions less severe. Selected article from the 6th European Meeting on Environmental Chemistry, University of Belgrade, Serbia and Montenegro organized by Prof. Dr. Branimir Jovancicevic ().     

Dichlorvos degradation studied by 31P-NMR

We studied the hydrolysis and TiO₂ photocatalysis of the pesticide dichlorvos at pH 2.6–9 using phosphorus-31 nuclear magnetic resonance (³¹P NMR). We found that the hydrolysis of dichlorvos led to the formation of dimethyl phosphate at pH 5.6–9. On the other hand, TiO₂ photocatalysis decomposed dichlorvos into dimethyl phosphate, which further reacted to form monomethyl phosphate at pH 2.6 and 9. Monomethylphosphate was hydrolysed into phosphate at pH 2.6. ³¹P NMR is therefore a promising tool to study the degradation of organophosphorus pesticides.     

Assessing Land-Use Impacts on Natural Resources

/ Much information is available on changes that occur in natural resources from both spatially-explicit data on environmental conditions and models of the interactions of these conditions and resources with human activities. The strategy for assessing land-use impacts on natural resources developed in this paper provides a framework for using relevant data and models to address questions of how management practices can promote both use and protection of resources. This assessment strategy integrates spatially explicit environmental data using geographic information systems (GIS) with computer models that simulate changes in land cover in response to land-use impacts. The computer models also simulate susceptibility of species to changes in habitat suitability and landscape patterns. The approach is applied to management of limestone barrens on the Oak Ridge Reservation in East Tennessee. Potential limestone barrens habitats are identified by overlaying appropriate soils, geology, slope, and land-use/land-cover conditions. Their validity is tested against known sites containing rare species that occur in these habitats. The location of habitats at risk in the aftermath of human activities is determined by using an available area model that identifies the size and proximity of sites that particular types of species can no longer use as habitat. The resulting risk map can be used in land management planning. The approach uses readily available in situ and remotely sensed data and is applicable to a wide range of locations and land-use scenarios. This approach can be refined based on needs identified by land managers and on the sensitivity of the results to the resolution of available resource information.KEY WORDS: Land management; Assessment; Habitat characterization; Limestone barrens; Ecological modeling; Geographic information systems     

Studies of metal-binding sites in natural organic matter and their role in the generation of disinfection by-products using lanthanide ion probes

In this study, the complexation of Tb3+ with natural organic matter (NOM) was studied by the method of time-resolved fluorescence spectroscopy. In the presence of NOM, the excitation of Tb3+ was observed in a wide range of wavelengths, for which virtually no excitation of free Tb3+ took place. The pseudo-quantum yield spectra (excitation intensity normalized by corresponding light absorbance values) had a maximum at 282 nm. This indicated that the excitation of NOM-bound Tb3+ proceeds through energy transfer from aromatic groups in NOM. The concentration of the metal-binding sites (C(L)) was determined by titration with Tb3+ and was found to range from 0.21% to 0.83% of total moles of organic carbon. The actual number of the carbon atoms that comprise these functionalities was hypothesized to be at least seven times higher. The C(L) values were well correlated with the reactivity of NOM with chlorine quantified by total organic halogen formation potential and with the contribution of polyhydroxyaromatic moieties determined by pyrolysis-GC/MS method. The correlation of C(L) with the contributions of aromatic and carboxylic moieties in NOM determined by 13C NMR was poor. Based on the data, it was concluded that the metal binding functionalities in NOM are closely associated with halogen attack sites.     

Characterization of the organic matter of sludge: determination of lipids, hydrocarbons and PAHs from road retention/infiltration ponds in France

This paper presents the results of the organic matter characterization of sludge from two ponds (retention and infiltration) located in France. Special focus was placed on studying hydrocarbons and PAHs. This investigation is part of a global project on road and urban sludge with the aim of identifying a better means for managing these materials. Gas chromatographic and GC/MS analyses indicate that the main component of the organic fraction stems from petroleum-derived products like diesel fuel and motor oil. This finding was confirmed by the presence of biomarkers from the hopane series, as well as by pyrolytic and alkylated PAHs. Results from this study clearly show that the contaminants are mainly generated from anthropogenic petroleum sources. Due to their levels of hydrocarbon contamination, these sludge deposits must be considered as waste and cannot therefore be disposed anywhere, especially within the current context of sustainable development.