DSpace 7
DSpace is the world leading open source repository platform that enables organisations to:
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Recent Submissions
Taxonomic Composition and Environmental Drivers of Phytoplankton in Earthen Fish Ponds (Bulgaria)
(Plovdiv University Press "Paisii Hilendarski", 2025-06-29) Dochin, Kostadin; Ivanova, Angelina; Ilieva, Lena; Iliev, Ivan
This study presents a comparative analysis of phytoplankton taxonomic structure and its relationship with environmental factors in earthen aquaculture ponds located in Plovdiv and Trivoditsi, Bulgaria, during the period May–September 2024. A total of 114 phytoplankton taxa were identified across six phyla, with Chlorophyta and Cyanoprokaryota dominating the bio-mass. The results showed a pronounced shift towards higher phytoplankton biomass (PhB up to 60.3 mg L⁻¹) and chlorophyll-a concentrations (up to 133 μg L⁻¹) in the Trivoditsi ponds, associated with blooms of green algae and cyanobacteria. For the first time, the invasive and potentially toxic species Raphidiopsis raciborskii was recorded in Bulgarian aquaculture ponds, contributing up to 15.5% of the phytoplankton biomass during bloom periods. Environmental parameters such as elevated ammonium, phosphate, and COD were positively correlated with increased PhB, chlorophyll-a, and total viable counts (TVC) of heterotrophic bacteria. Redundancy analysis (RDA) highlighted the influence of nutrient enrichment and organic load on the biological variables. The observed co-variation between PhB and TVC suggests the presence of a dynamic microbial loop, where intensive primary production supports hetero-trophic bacterial growth. These findings confirm the role of eutrophic conditions and nutrient availability in shaping phytoplankton and microbial communities in earthen ponds used for aquaculture. This study provides new insights into the ecological interactions in such systems, contributing to future strategies for water quality management and sustainable aquaculture practices.
Seasonal characteristics of precipitation in the region of NAO Rozhen, Bulgaria, for the period 2023—2025
(Plovdiv University Press "Paisii Hilendarski", 2025-06-29) Paskaleva, Vesselina; Terziyski, Atanas; Kochev, Nikolay; Tenev, Stoyan; Petrov, Nikola
The article presents high-resolution observations of winter precipitation in the region surrounding the National Astronomical Observatory (NAO) Rozhen, Bulgaria, at an altitude of 1,730 meters above sea level, during the 2023–2025 period. Utilizing an array of advanced meteorological instruments, including the OTT Pluvio²L, Parsivel² disdrometer, WS100 radar sensor, and SHM31 snow depth sensor, we captured detailed in-situ data on precipitation type, intensity, and duration. The integrated sensor system enabled the classification and quantification of various precipitation events such as snow, rain, drizzle, and hail with minute-level resolution. The study features multiple precipitation-related variables, including total amount, intensity, and precipitation type. Seasonal and daily variations in precipitation behavior were documented, with snow dominating the winter period but often accompanied by mixed-phase events. The dataset supports enhanced understanding of precipitation dynamics in mountainous terrain and offers potential for model calibration, climate profiling, and natural air purification assessments. All data is provided in FAIR-compliant formats to support further research and environmental monitoring efforts.
Tracking Volcanic Atmospheric Waves: Insights from the 2022 Hunga Tonga Eruption observed with an Open Sensor Network in Bulgaria
(Plovdiv University Press "Paisii Hilendarski", 2025-06-29) Terziyski, Atanas; Tancheva, Gergana; Jeliazkov, Vedrin; Kochev, Nikolay; Paskaleva, Vesselina
The January 2022 eruption of Hunga Tonga was one of the most powerful volcanic events of the modern era, generating a vertical plume that reached over 50 kilometres above Earth’s surface. The initial explosion, followed by a high-speed atmospheric jet, triggered waves that circled the globe multiple times. The effects of the eruption on Bulgarian territory were detected and analysed using data from the METER.AC network, which includes a wide array of custom-designed and assembled ground monitoring stations, enhanced by a set of certified professional weather stations. These stations utilise the Internet of Things (IoT) paradigm to
collect data from a variety of sensors and provide open access to the recorded measurements. We have developed a suite of algorithms to process the collected data through several methods, including semi-automated detection of wave minima and maxima, Fourier spectral analysis, and the integration of data from nearby instruments. This approach enabled us to identify and analyse the first two atmospheric waves that reached Bulgaria and to calculate their average propagation speeds—301 m/s and 315 m/s, respectively. This research highlights the significance and capability of the citizen science network, METER.AC, in providing valuable data for understanding global phenomena, particularly large-scale volcanic events. It also highlights the potential of IoT-based systems and data processing algorithms in advancing atmospheric research and environmental monitoring.
Polyphenol-containing water-soluble bio-composite films as alternative food packaging materials
(Plovdiv University Press "Paisii Hilendarski", 2025-06-29) Grigorov, Aleksandar; Viraneva, Asya
Historically, the development of better food preservation techniques has been one of the main factors in the prosperity and health of any human population, and with the exponential rise in food demand leads science in search of eco-friendlier solutions. One such path is the development of water-soluble biodegradable coatings based on easily accessible and abundant natural polymer materials. As a common byproduct of the food industry, corn zein is one of the most promising biopolymers for food packaging, offering excellent barrier properties. Its main drawback – poor mechanical strength – can be mitigated with the addition of other biodegradable polymers that would result in the creation of bio-composite materials with controllable properties. Further improvements of such biopolymer coatings can be achieved with the addition of other materials, such as different polyphenols, that may improve their antioxidant properties. The presented paper investigates water-soluble bio-composite films, created by
dissolving equal parts zein and hydroxypropyl methylcellulose in ethanol solution (70:30 ethanol to water ratio). Polyethylene glycol was used as plasticiser in all samples. Two different polyphenols (quercetin and curcumin) were incorporated in the bio-composites at a concentration of 2 mg/cm2. The mechanical properties of the created films were studied with a use of Universal Testing Machine (Lloyd Instrument). The surface morphology was investigated with scanning electron microscopy and the surface free energy was determined with the use of the sessile drop method. The dependence of the normalized surface potentials on the storage time
of the charged substrates was studied. Parameters, important for food preservation, such as water vapor permeability, were investigated.
Air quality control in Plovdiv, Bulgaria: the citizens' awareness. Results from a pilot quantitative study
(Plovdiv University Press "Paisii Hilendarski", 2025-06-29) Mitev, Tihomir; Tchalakov, Ivan; Keskinova, Donka; Parapanov, Petar
Air pollution is a leading risk factor for individual and public health. It is a major environmental stressor responsible for hundreds of thousands of premature deaths in Europe every year. Monitoring and controlling air quality is about the importance of managing public health, as is ensuring people are aware of the dangers of polluted air and getting them involved in the issue. The article presents a summary of the results and data analysis from a pilot study conducted in May-June 2025 on the awareness, interest, personal engagement, and assessment of citizens in Plovdiv (Bulgaria) – one of the most polluted cities in Europe – regarding the control of air quality in the city.