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- FG Geopedologie und Landschaftsentwicklung (31) (remove)
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Die zurückliegenden trocken-heißen Sommer haben im Süden Brandenburgs zu zahlreichen Bränden in den dominierenden Kiefernwäldern geführt, einige davon mit katastrophalen Ausmaßen. Dazu gehören die extremen Brandereignisse 2018 bei Treuenbrietzen sowie 2019 bei Jüterbog und Lieberose, die zusammen weit über 1000 ha Waldfläche zerstört und dabei auch Veränderungen der betroffenen Waldböden verursacht haben.
Das seit Mai 2020 von der FNR geförderte Verbundvorhaben Pyrophob befasst sich mit den Auswirkungen von Waldbränden im Süden Brandenburgs auf die Waldökosysteme und mit waldbaulichen Maßnahmen, die mittelfristig zu einer Verringerung der Brandanfälligkeit der Wälder beitragen sollen. Im Rahmen des auf eine fünfjährige Laufzeit ausgelegten Verbundvorhabens finden bodenkundliche Untersuchungen auf zwölf Versuchsflächen bei Treuenbrietzen und Jüterbog statt. An beiden Standorten werden unverbrannte Referenzflächen mit einbezogen. Ergänzend konnten bei Lieberose bereits 2019 nur kurz nach dem Brandgeschehen erste Bodenuntersuchungen durchgeführt werden. Die untersuchten Brandflächen bei Jüterbog und Lieberose sind als Totalreservate ausgewiesen, auf denen auch nach dem Brand waldbauliche Maßnahmen vollständig unterbleiben. Auf den Flächen bei Treuenbrietzen wurden verschiedene Behandlungsvarianten durchgeführt, zu denen auf einem Teil der Flächen die vollständige Entfernung der abgestorbenen Bäume gehörte, während auf anderen Teilflächen Totholz auf der Fläche verblieb.
Ziel der bodenkundlichen Arbeiten in Pyrophob ist zum einen eine Charakterisierung der direkten Auswirkungen des Brandes auf Humus und Mineralboden hinsichtlich des Stoffbestandes und bodenbiologischer Prozesse. Zum anderen wird der Stoffaustrag aus dem Oberboden erfasst. Der etwaige Einfluss der unterschiedlichen waldbaulichen Vorgehensweise auf die Bodenverhältnisse wird dabei als ein Indikator für die Auswahl geeigneter Maßnahmen berücksichtigt.
In den verschiedenen Untersuchungsvarianten des Vorhabens wurden zu diesem Zweck Humus- und Mineralbodenprofile untersucht. Zudem wurden Mischproben aus dem Ober- und Unterboden entnommen und auf ihren Stoffhaushalt hin analysiert. Auf jeder Untersuchungsfläche wurden je drei frei dränende Kleinlysimeter in 10 cm Bodentiefe installiert, um die zeitlichen Veränderungen der Sickerwasserzusammensetzung und die durch den Brand initiierten Stoffausträge aus dem Oberboden zu quantifizieren. Ergänzend finden Untersuchungen zu möglichen Auswirkungen der Brände auf bodenbiologische Prozesse wie Streuabbau und Stickstoffmineralisation statt.
The occurrence, soil parameters and genesis of rubified soils (‘Fuchserden’) of northeastern Germany
(2019)
This study aims at investigating the iron cyanide (CN) degradation potential of two natural bacterial isolates with the purpose of their application in iron CN phytoremediation. The strains were isolated from contaminated soil and incubated over 4 months with 50mg L⁻¹CN (as ferrocyanide) as the sole iron and nitrogen source. Unlike previous reports, the study provides control for bacterial growth, biotic and abiotic CN losses. Bacterial growth, CN, ammonium, and nitrate concentrations were monitored regularly. Both strains grew less rapid with iron CN compared with the positive control. However, the growth was diauxic. The CN concentration in the media decreased with 20% and 25% respectively, while that in the sterile controls remained stable. Ammonium was detected in the media of both strains implying that a fraction of the initially applied ferrocyanide has been converted. The nitrogen lost from the system evened out with that in the cells at the end of the experiments. These results showed that the investigated strains were undoubtedly able to grow on iron CN as an alternative nitrogen source, but contrary to some previous findings, the iron CN utilization is much slower and takes place only after complete exhaustion of the cellular nitrogen reserves.
The formation of dunes in central Europe reflects ample sediment supply during the last deglacial hemicycle. A Quaternary inland dune complex in southern Brandenburg, Germany, was studied to frame the duration of pedogenesis in two outcrops containing buried paleosols. An integrative approach, which combined geomorphological, sedimentological, pedological and chronological methods was used to identify aeolian deposition events, ensuing pedogenesis and anthropogenic remobilization. At the outcrops, which were situated approximately 2 km apart from each other, a total of twelve samples of the aeolian sands were dated using optically stimulated luminescence (OSL) and a further six samples using 14C dating. Although the dunes have similar morphological features, these forms have a different history of aeolian sand deposition and pedogenesis. At the older dune (Gl 1) the surface soil is a well developed Podzol, whereas soil development of the younger dune (Gl 2) is clearly in an initial state. The studied sites of the dune complex also differ in grain size distribution and in the presence of buried soils, thereby indicating a climatic impact on aeolian remobilization.
Soils and groundwater on sites of the former Manufactured Gas Plants (MGPs) are contaminated with various complex iron-cyanides (Fe-CN). Phytoremediation is a promising tool in stabilization and remediation of Fe-CN affected soils, however, it can be a challenging task due to extreme adverse and toxic conditions. Phytoremediation may be enhanced via rhizosphere microbial activity, which can cooperate on the degradation, transformation and uptake of the contaminants. Recently, increasing number of scientist reports improved plants performance in the removal of toxic compounds with the support of arbuscular mycorrhizae fungi (AMF). Series of batch experiments using potassium hexacyanoferrate (II) solutions, in varying concentrations, were used to study the effect of ryegrass roots (Lolium perenne L.) inoculation with Rhizophagus irregularis and a mixture of Rhizophagus irregularis, Funneliformis mosseae, Rhizophagus aggregatus, and Claroideoglomus etunicatum on Fe-CN sorption. Results indicated significantly higher colonization of R. irregularis than for the mixture of AMF species on ryegrass roots. Sorption experiments revealed significantly higher reduction of total CN and
free CN content in the mycorrhizal roots, indicating greater cyanide decrease in the treatment inoculated with R. irregularis. Our study indicates contribution of AM fungi in phytoremediation of Fe-CN contaminated soil.
Arbuscular mycorrhizal fungi (AMF) are integral functioning parts of plant root systems and are widely recognized for enhancing contaminants uptake and metabolism on severely disturbed sites. However, the patterns of their influence on the phytoremediation of iron–cyanide (Fe–CN) complexes are unknown. Fe–CN complexes are of great common interest, as iron is one of the most abundant element in soil and water. Effect of ryegrass (Lolium perenne L.) roots inoculation, using mycorrhizal fungi (Rhizophagus irregularis and a mixture of R. irregularis, Funneliformis mosseae, Rhizophagus aggregatus, and Claroideoglomus etunicatum), on iron–cyanide sorption was studied. Results indicated significantly higher colonization of R. irregularis than the mixture of AMF species on ryegrass roots. Series of batch experiments using potassium hexacyanoferrate (II) solutions, in varying concentrations revealed significantly higher reduction of total CN and free CN content in the mycorrhizal roots, indicating greater cyanide decrease in the treatment inoculated with R. irregularis. Our study is a first indication of the possible positive contribution of AM fungi on the phytoremediation of iron–cyanide complexes.
The soil in the vicinities of former Manufactured Gas Plant (MGP) sites is commonly contaminated with iron-cyanide complexes (ferric ferrocyanide). The phenomenon of cyanide mobility in soil, according to the literature, is mainly governed by the dissolution and precipitation of ferric ferrocyanide, which is only slightly soluble (<1 mg L¡1) under acidic conditions. In this paper, retention properties of the sandy loam soil and the potential vertical movement of the solid iron-cyanide complexes, co-existing with the dissolution, sorption and precipitation reactions were investigated. Preliminary research conducted on a former MGP site implied colloidal transport of ferric ferricyanide from the initial deposition in the wastes layer towards the sandy loam material (secondary accumulation), which possibly retarded the mobility of cyanide (CN). A series of batch and column experiments were applied in order to investigate the retardation of iron-cyanide complexes by the sandy loam soil. Batch experiments revealed that in circumneutral pH conditions sandy loam material decreases the potassium ferro- and ferricyanide concentration. In column experiments a minor reduction in CN concentration was observed prior to addition of iron sulfide (FeS) layer, which induced the formation of the Prussian blue colloids in circumneutral pH conditions. Precipitated solid iron-cyanide complexes were mechanically filtered by the coherent structure of the investigated soil. Additionally, the reduction of the CN concentration of the percolation solutions by the sandy loam soil was presumably induced due to the formation of potassium manganese iron-cyanide (K2Mn[Fe(CN)6]).
Phytoremediation of sites contaminated with iron cyanides can be performed using poplar and willow trees. Poplar and willow trees were grown in potting substrate spiked with ferrocyanide concentrations of up to 2,000 mg kg-1 for 4 and 8 weeks respectively. Soil solution and leaf tissue of different age were sampled for total cyanide analysis every week. Chlorophyll content in the leaves was determined to quantify cyanide toxicity. Results showed that cyanide in the soil solution of spiked soils differed between treatments and on weekly basis and ranged from 0.5 to 1,200 mg l-1. The maximum cyanide content in willow and poplar leaves was 518 mg kg-1 fresh weight (FW) and 148 mg kg-1 FW respectively. Cyanide accumulated in the leaves increased linearly with increasing cyanide concentration in the soil solution. On the long term, significantly more cyanide was accumulated in old leaf tissue than in young tissue. Chlorophyll content in poplar decreased linearly with increasing cyanide in the soil solution and in leaf tissue, and over time. The inhibitory concentration (IC50) value for poplars after 4 weeks of exposure was 173 mg l-1 and for willow after 8 weeks of exposure—768 mg l-1. Results show that willows tolerate much more cyanide and over a longer period than poplars, making them very appropriate for remediating sites highly contaminated with iron cyanides.