No abstract

Pipeline spills and pollution of the environment by crude oil pose a threat to natural resources, especially soil and water. One such incident occurred on 25 September 2018 in the area of Budrovac (Croatia; 46°00′14.6″ N 17°04′16.8″ E) on agricultural land as a pipeline spill. Bioremediation of the contaminated soil was carried out with organic pollutants using an environmentally safe absorbent Spill-Sorb (Canadian Sphagnum Peat Moss) and a mineral fertilizer—nitrogen. The experiment was conducted in the greenhouse of the Faculty of Agriculture, Croatia, during a six-month (October 2018–April 2019) study. Samples of agricultural soils contaminated with total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) were taken after the rupture of the local gas condensate pipeline. The experiment was conducted in five treatments in triplicate: I-control (clean soil); II-100% contaminated soil + organic absorbent + nitrogen; III-100% contaminated soil + organic absorbent; IV-50% clean soil + 50% contaminated soil + organic absorbent + nitrogen; and V-50% clean soil + 50% contaminated soil + organic absorbent. The soil properties studied were pH, organic matter content, carbon and nitrogen content and ratio, and changes in the concentration of potential organic contaminants—TPHs and individual PAHs. The results demonstrated that the mixture of organic absorbent and nitrogen efficiently removed organic pollutants from the contaminated soil within six months. However, the application of Spill-Sorb alone was more effective for the degradation of hydrocarbons. The effectiveness of the absorbent studied was dependent on the concentration of organic pollutants and nitrogen application.

Natural landscapes in the Mediterranean ecosystem have experienced extensive changes over the last two centuries due to wildfire activity. Resulting interactions between climatic warming, vegetation species, soil natural, and meteorological condition before and after a wildfire create substantial abrupt landscape alterations. This study investigates the evolution (2 days, 3, 6, 9, and 12 months after a fire) of topsoil (0–5 cm) chemical properties in burned Cambisols (Zadar County, Croatia) with respect to different wildfire severities (HS—high severity, MS—medium severity, C—unburned) and vegetation species (Quercus pubescens Willd. and Juniperus communis L.). Soil pH, electrical conductivity (EC), calcium carbonates (CaCO3), total organic carbon (TOC), total nitrogen (TN), total sulphur (TS), copper (Cu) and zinc (Zn) were significantly higher in HS than in MS and C. Total soil potassium (TK), Fe and Ni were significantly higher in C than in HS. The increase of TOC and TN was more pronounced in Quercus p. than Juniperus c., especially in the first three months. Soil pH, EC, CaCO3, TOC, TN, and TS were most affected by wildfire severity. The distinction between C, MS and HS categories was less visible 9 and 12 months post-fire, indicating the start of the recovery of the soil system. Post-fire management and temporal recovery of the soil system should consider the obvious difference in soil disturbance under HS and MS between vegetation species.

There is a lack of information in the rural Mediterranean area about agricultural pile burning impacts on soil nitrogen (N) dynamic and the N loss. Therefore, this research aims to study the impacts of moderate (MS), and high (HS) severity burn on N transformation and N losses, compared to an unburned (C) during the first year. The experimental plots (10 m2) were established in Croatia (43°58′ N 15°31′ E), in a slope ~18°, with a southwest exposition. Five days after the burn, C treatment had a significantly higher total N (TN) than MS and HS. Generally, the runoff was significantly different between burned and C treatments. Sediment yield, concentrations, and TN loss were significantly higher in MS than in C treatment. The concentrations of ammonium (NH4-N) and nitrate (NO3-N) in the runoff, and their losses were higher in burn treatments than in C treatment. These values were high in the first three months after burn, although the peaks in later periods correspond to extreme rainfall events. Principal component analysis showed that sediment yield was associated with sediment concentration, runoff, and TN loss (Factor 1). In addition, rainfall amount and intensity were inversely related to NH4-N concentration and losses (Factor 2). The NO3-N concentration was positively related to NO3-N losses. Overall, MS treatment had severe effects on N loss and, sediment yield can be used as an indicator of soil degradation after pile burns.

<p><strong>The effects of mulch (<em>Olea europea</em> and <em>Pinus halepensis</em>) on burned soils: A preliminary study in Adriatic coast (Croatia)</strong></p><p>Delac, Domina<sup>1*</sup>; Pereira, Paulo<sup>2*</sup>; Kisic, Ivica<sup>1</sup></p><p><sup>1</sup>University of Zagreb, Faculty of Agriculture, Department of General Agronomy, Svetosimunska cesta 25, 10000 Zagreb, Croatia. (*ddelac@agr.hr)</p><p><sup>2</sup>Mykolas Romeris University, Environmental Management Laboratory, Ateitis street 20, LT-08303, Vilnius, Lithuania (*pereiraub@gmail.com)</p><p> </p><p>In the recent decades the frequency and intensity of summer drought periods is increasing in Adriatic coast. These changes in climate increase the vulnerability to wildfires. Wildfires can change soil physical and chemical properties. However, these effects can be mitigated by mulching. The aim of this work is to study the effects of mulch (<em>Olea europea</em> and <em>Pinus halepensis</em>) on fire affected soils. The wildfire occurred on 28 July 2019 and affected an area of about 900 ha in Dalmatia, near Adriatic Coast (43°45'06.0"N 15°56'02.9"E with an elevation of 105 m a.s.l.).  The mean annual temperature is 15.8 °C, and the annual precipitation is 800 mm. It was affected agricultural land with dominant culture <em>Olea europea</em> and abandoned grassing where dominates <em>Pinus halepensis</em>. Soils are classified as <em>calcocambisols</em>. Twenty-five days after the fire, two plots (5 treatments per plot) were established and covered with <em>Olea europea</em> and <em>Pinus halepensis</em> mulch. A control plot was established as well. Soil were sampled (0 – 5 cm), twenty- days after fire (August, 2019), before mulch application, and then 3 months after fire (November, 2019). A total of 15 samples were collected per treatment (45 each sampling date). The soil properties analysed were soil pH, soil organic matter (SOM), mean weight diameter (MWD) to express aggregate stability, and soil water repellency (SWR) measured with water drop penetration time method (WDPT) in different fractions (2 – 1 mm; 1 – 0.5 mm, 0.5 – 0.25 mm, and <0.25 mm). Soil pH was not significantly different among sampling dates and treatments. SOM was significantly different among sampling dates for <em>Olea europeae</em> treatment and control. <em>Olea europeae</em> treatment had a significantly higher SOM then <em>Pinus halepensis</em> and control treatment. MWD was significantly higher within <em>Olea europeae</em> treatment. Within <em>Pinus halepensis</em> and control treatment no significant difference was observed. The soil was classified as slightly water repellent (5 – 60 seconds) in <em>Olea europeae</em> soil finer fraction (0.5 – 0.25 mm and <0.25) in both sampling dates. In <em>Pinus halepensis</em> treatments and control, soil was wettable (<5 seconds), and no significant difference was observed among sampling date. Future sampling and analysis will be conducted during one year to estimate the effect of <em>Olea europeae</em> and <em>Pinus halepensis</em> mulch on soil properties.</p><p><strong>Keywords: </strong>Wildfire, <em>Olea europeae</em><strong>, </strong><em>Pinus halepensis</em>, mulch.</p><p> </p><p><strong>Acknowledgments</strong></p><p>This work was supported by Croatian Science Foundation through the project "Influence of Summer Fire on Soil and Water Quality” (IP-01-2018-1645).</p>

<p>In the Mediterranean part of Croatia, wildfires have increased in recent decades raising concerns about soil degradation. Post-wildfire stabilization treatments are used in fire affected areas due to their easy application and possible beneficial effects on soil quality. On 28 July 2019, a moderate to high severity wildfire affected about 900 ha in the central part of Mediterranean, Croatia (43°45'N 15°56'E; 105 m a.s.l.). Wildfire mostly affected abandoned grassing with a dominant culture Aleppo pine (<em>Pinus halepensis</em>), and olive groves (<em>Olea europaea</em>). The effects of wildfire (control (C); uncovered burned soil), and two post-wildfire stabilization treatments (mulches); pine needles (PM) and olive leaves (OM) were evaluated on soil samples (0–5 cm depth) taken during 5 sampling campaigns; 25 days after fire (DAF), 3 months after fire (MAF), 6 MAF, 9 MAF, and 12 MAF. One treatment covered 10 m<sup>2</sup>, and mulches were applied in 0.5 kg m<sup>-2</sup>. The non-destructive analytic method, X-ray fluorescence (pXRF), was used to determine the behavior of total concentrations of nutrients and pollutants in all soil samples. The results showed that Al and P were significantly lowest at PM 12 MAF compared to other dates. The P was also significantly lowest at C 3 MAF than other dates. The Ti was significantly lowest at PM 12 MAF then C treatment, while the Zn was significantly different between PM and OM treatments 12 MAF, with highest values at PM. The Si didn’t vary significantly under mulch treatments, but in C was significantly highest 12 MAF in regard to 25 DAF. The K was significantly highest at both mulch treatments 3 MAF, regard to other dates and C treatment. The Pb showed significant changes only in PM between 3 and 12 MAF, with highest concentrations 12 MAF. The S showed significant difference in C between 25 DAF and 12 MAF with the highest 25 DAF. The effects of fire and mulches during the first post-fire year didn’t show significant change of Ca, V, Cr, Mn, Fe, Co, Ni, Cu, As, Rb, Sr, Y, Zr, Nb, and Th concentrations. These results show that PM had a more notable impact on the concentrations of major and minor topsoil elements in comparison to OM. However, it is concluded that more time is required to complete mulch decomposition and possible increment in soil quality.</p><p><strong>Acknowledgments:</strong> The work was supported by Croatian science foundation under the project “Influence of Summer Fire on Soil and Water Quality” (IP-2018-01-1645).</p>

No abstract

Little is known about the bonfire impact on microbial properties in soil. This work aimed to study moderate- to high-severity experimental burning (250 °C) compared to unburned Cambisol in a natural Mediterranean environment (Croatia) on selected soil properties. The soil was sampled immediately and 1, 2, 4, and 6 months after the fire. The fire increased the mean weight diameter, water stable aggregates, and water repellence in different soil fractions, and the observed effect was the strongest immediately after the fire. It also altered soil pH, electrical conductivity, total nitrogen carbon, and sulphur content, and completely destroyed carbapenem-resistant bacteria, but did not significantly affect the soil’s mineralogical properties. Six months after the fire, most microbial properties (save for pH) returned to near control values. Heterotrophic, sporogenic, and phosphate-solubilising bacteria started to recover after a month, whereas the population of carbapenem-resistant bacteria was destroyed initially, but recovered by the fourth month after the fire. Dehydrogenase activity was not significantly affected, but proper recovery started four months after the fire. Even though Cambisol showed some resilience to fire and its properties mostly returned to normal by the sixth month, and a full recovery is expected to occur later, as vegetation returns.