Abstract. In the course of anaerobic sludge treatment (digestion) biogas can be acquired from the sludge, its use for energetic purposes has a determinative significance in a wastewater treatment plant. The biogas, produced in the course of decomposition, covers -among others -a considerable portion of the heat-and electric energy consumption in a wastewater treatment plant, thus an increase of the biogas volume is an outstanding task. It is possible to increase the biogas volume if the anaerobic digestion processes are thoroughly well known. The anaerobic digestion process is determined by temperature, substrate composition, loading, and also by toxic substances that might be present. In our experimental work the thermophilic and mesophilic full scale anaerobic bioreactors of a communal sewage treatment plant were tested by applying usual control parameters and enzyme activity tests.

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Due to their outstanding anthocyanin content, elderberries are mainly used in the food industry to produce pigment concentrations. Thanks to the increase in demand, elderberry is grown on ever greater areas in Hungary and in neighbouring countries. Cultivar use, however, is very one-sided, being practically restricted to ‘Haschberg’. As this cultivar has many negative properties, growers have begun to plant and test new cultivars. When determining the commodity value of cultivars, it is important to examine not only the physical traits of the fruit, but also their main chemical parameters. In the present experiment the chemical properties (soluble solids and titratable acid content, total polyphenol and anthocyanin content, antioxidant capacity) of the fruit of 11 elderberry cultivars (‘Haidegg 13’, ‘Haidegg 17’, ‘Haschberg’, K3, ‘Korsör’, ‘Samdal’, ‘Samidan’, ‘Samocco’, ‘Sampo’, ‘Samyl’, ‘Weihenstephan’) were analysed in three consecutive years. In addition to the comparative evaluation of the cultivars, this work also aimed to discover correlations between the components and to study the effect of the year on the chemical composition of the fruit. Significant differences were found between the cultivars for the soluble solids content (F(10;8.74)=9.71; p=0.001), the titratable acid content (F(10;22)=7.91; p<0.001), the polyphenol content (F(10;22)=9.77; p<0.001), the anthocyanin content (F(10;8.52)=36.18; p<0.001) and the antioxidant capacity (F(10;22)=3.61; p=0.006). A year effect was proved for the water-soluble solids content (F(2;30)=4.02; p=0.028) and the antioxidant capacity (F(2;30)=5.21; p=0.011). Among the chemical properties, a significant positive linear correlation was only detected between the polyphenol and anthocyanin contents (r=0.91; p<0.001). Among the cultivars, ‘Sampo’, ‘Samidan’ and ‘Weihenstephan’ exhibited outstanding polyphenol and anthocyanin contents. The soluble solids content and antioxidant capacity of ‘Haidegg 17’ were also promising.

This work considers dust deposition and the heavy metal (HM) content on leaves of urban trees (Acer platanoides L. ‘Globosum,’ Fraxinus excelsior L. ‘Westhof’s Glorie’ and Tilia tomentosa Moench.) in order to estimate the trees’ capacity to remove dust and HM from the air. Leaves were collected from the Buda Arboretum and from different streets of heavy traffic in Budapest, Hungary, during 2015 and 2016. At each site, five trees were sampled by collecting 6 leaves from each tree from the height of 2–3 m. Dust deposits on the leaves were removed by soaking the fresh foliage in distilled water for 20 h and then washed with ultrasound shaking. Afterward, the leaves were dried to constant weight and then they were digested in nitric acid–hydrogen peroxide treatment, and their Pb, Fe, Ni, Zn and Cu contents were measured using an inductively coupled plasma (ICP AS) spectrometer. The removed dust deposit was dried, and after a similar digestion treatment the Pb, Fe, Ni, Zn and Cu contents were measured using an AURORA AI 1200 AAS appliance. The HM deposit was calculated in mg m–2 leaf surface area. In 2015, the amount of foliar dust deposit from spring to autumn increased from 86.3 to 270.2 mg m–2. The most efficient tree species in trapping dust on their leaves was the silver linden (98.5–123.5 mg m−2), followed by the Norway maple (74.2–84.8 mg m−2) and the common ash (62.8–74.6 mg m−2). The deposit of HM elements showed seasonal differences: the quantity of Fe and Pb deposit on autumnal leaves increased five- to tenfold, while other heavy metals did not show accumulation. Silver linden with its pubescent (hairy) leaf surface proved to be most efficient in entrapping and retaining dust and heavy metals. The 60–100% higher Pb and Fe content of autumnal leaves indicate that over the season leaves may absorb Fe and Pb from the foliar dust. Our results confirmed that the foliar dust is a potential indicator for monitoring the HM content in the air. We also show that foliar dust deposits should be considered when estimating the capacity of urban trees to clean the air.

Soil respiration of grasslands is spatio-temporally variable reflecting the changing biological activities of the soil. in our study we analysed how the long-term soil respiration activities of dry grasslands would perform in terms of resistance and resilience. We also investigated how terrain features are responsible for response stability. We conducted a 7-year-long spatial study in a Hungarian dry grassland, measuring soil respiration (R s), soil temperature (T s) and soil water content (SWC) along 15 measuring campaigns in 80 × 60 m grids and soil organic carbon content in 6 of the occasions. two proxy variables were introduced to grasp the overall R s activity, as well as its temporal stability: average rankR s , the temporal average R s rank of a measuring position from the campaigns revealed the persistent spatial pattern of R s , while rangeR s , the range of ranks of the positions from the campaigns described the amplitude of the R s response in time, referring to the response stability in terms of resistance or resilience. We formulated a hypothetic concept of a two-state equilibrium to describe the performance of the long-term R s activity: R s activity with smaller rangeR s , that is both the lower elevation positions with larger rankR s ("state I") and the higher elevation positions with smaller rankR s ("state II") correspond to an equilibrium state with several terrain attributes being responsible for the equilibrium responses. Majority of the measuring positions was belonging to none of these equilibrium states. these positions showed higher rangeR s for medium rankR s , suggesting resilience (not resistance) as a major strategy for this ecosystem. Grasslands exchange large quantities of greenhouse gases between the soil and the atmosphere. Uncertainties related to greenhouse gas flux estimates originate partly from the fact that these fluxes are spatio-temporally highly variable 1-5. Seasonal and diurnal fluctuations of these fluxes, e.g., soil respiration (R s) and its components are partly temperature (T s) driven 6 but temporal changes in soil moisture (SWC 7), plant biomass, photosynthetic performance 8 and litterfall also play a significant role in modifying the overall picture. Also, R s and its main abiotic drivers, T s and SWC, show substantial horizontal heterogeneity at different spatial scales 4,9-13 , which is made even more complex by the interaction of the explanatory variables (e.g., cooling effect of soil moisture 4,11,14). These point to the relevance of spatial studies with temporal replicates 14. Although the actual value and spatial distribution of the pattern-generating factors are responsible for the observed spatial pattern of R s , the functioning of ecosystems takes place through dynamically changing, forming and transforming spatial patterns 13,15-19 , which are worth further investigations. Furthermore, the stability of ecosystem functions and the existence of persistent patterns are of high significance as these patterns are sustained by long-term climatic, surface rel...