One of the major reasons for the increase in global air temperature since the early 20th century is considered to be the increase in the atmospheric CO2 concentration. Karst relief is considered an ...important carbon sink, but it can also be a natural source of carbon and CO2 emission. Aquatic systems in karst areas facilitate carbon exchange between the karst and the atmosphere, often through groundwater geochemical carbonate rock dissolution (carbon sink) and in the form of secondary calcium carbonate precipitation (possible carbon source).
The protected area of Plitvice Lakes National Park, located in the karst region of Croatia, was chosen as a case study on karst geochemical processes. The lakes are also specific for their authigenic calcite precipitation in the form of tufa barriers and lake sediment. Physical and chemical data (temperature, pH, Ca2+, HCO3−, Mg2+ and CO2 concentrations, calcite saturation index (SIcalc), calcite dissolution ionic ratio (IRcalc), and Mg/Ca ratio) from water samples collected at 8 locations (2 springs, 2 rivers, and 4 lakes) from 1981 to 2014 were studied.
The data were not collected systematically, so long-term changes have been mostly assessed through comparison between parameters from two selected periods (1981–1986 and 2010–2014) and through temporal correlations for each observed parameter in each calendar month.
For the 33 years studied, an increase in air and water temperature, Ca2+ and HCO3− concentrations, calcite saturation index (SIcalc), calcite dissolution ionic ratio (IRcalc), and a decrease in the Mg/Ca ratio were observed. No statistically significant change was observed for pH or CO2 and Mg2+ concentrations. Average discharge rates did not display any significant change over the past three decades, however there was a change in their seasonal distribution.
The significant increase in Ca2+ and HCO3− concentrations at lake locations were primarily caused by an increase in Ca2+ and HCO3− values in the water of the springs. Simultaneously, Mg2+ concentrations remained constant, which indicates higher levels of limestone (calcite) dissolution than dolomite dissolution. One of the reasons for this could be higher air/soil temperatures, resulting in higher soil CO2 production, which appears to result in the higher dissolution of calcite exclusively. An increase in HCO3− concentrations at the springs implies that karst groundwater is a carbon sink. Furthermore, the fact that the spatial decrease in HCO3− concentration in downstream waters was the same during the 1981–1986 and 2010–2014 periods implies that the entire observed karst lake system itself is a carbon sink.
Temporal and spatial changes in SIcalc and IRcalc values in surface waters were mainly attributed to an increase in the intensity of bioactivity, which is in turn connected with an increase in water temperature.
•Physicochemical parameters of karst lakes from 1981 to 2014 were studied.•Air and water temperature, c(Ca2+), c(HCO3−) and SIcalc increased.•Increase assigned to higher limestone dissolution and primary productivity.•Karst ground and surface waters can be regarded as a carbon sink.•Since c(Mg2+) was constant Mg/Ca cannot be used as a temperature indicator.
We investigated the influence of local meteorological conditions and number of visitors on ambient particulate matter (PM) mass concentrations and particle fraction ratios at the Plitvice Lakes ...National Park between July and October 2018. Outdoor mass concentrations of particles with aerodynamic diameters of less than 1, 2.5, and 10 μm (PM
, PM
, and PM
, respectively) and indoor PM
were measured with two light-scattering laser photometers set up near the largest and most visited Kozjak Lake. Our findings suggest that the particles mainly originated from background sources, although some came from local anthropogenic activities. More specifically, increases in both indoor and outdoor mass concentrations coincided with the increase in the number of visitors. Indoor PM
concentrations also increased with increase in outdoor air temperature, while outdoor PMs exhibited U-shaped dependence (i.e., concentrations increased only at higher outdoor air temperatures). This behaviour and the decrease in the PM
/PM
ratio with higher temperatures suggests that the production and growth of particles is influenced by photochemical reactions. The obtained spectra also pointed to a daily but not to weekly periodicity of PM levels.
The Plitvice Lakes National Park is inscribed on UNESCO’s World Heritage List. The lake system is composed of 16 cascading lakes of different sizes separated by tufa barriers, which are the park’s ...key phenomenon. The lakes are characterized by highly diverse trends of the characteristic hydrological indicators—mean annual water levels, discharges, and tufa barrier growth. The analyses carried out in this paper identified that in the period before the early 1990s, Kozjak Lake had a trend of decreasing discharges, together with a trend of increasing water levels and growing tufa barriers. In contrast to this, in the period after 2001, a trend of increasing discharges was recorded, as well as a trend of decreasing water levels and decreasing tufa barriers. A potential cause of the barriers decreasing in size were the extremely high discharges during the last decade, which resulted in increased erosion of the tufa barriers. Losses of water due to the sinking from the lake system as well as the upper Korana course were confirmed, and it was identified that during the analyzed period the losses had not changed significantly. It was determined that the losses of water from Kozjak Lake occurred during low-water periods; however, they depended not only on the quantity of water flowing through the lakes but also on the hydrological conditions underground. The analyses carried out and the methodological procedures used in the analyzed area of the Plitvice Lakes are useful examples for the performance of analyses at similar lakes in karst formed by tufa deposition processes.
An evaluation of the quality status of the pristine karst, tufa depositing aquatic environment of the Plitvice Lakes National Park based on the analysis of heavy (ecotoxic) metals was examined for ...the first time. Analyses of trace metals in water, sediment and fish (Salmo trutta, Oncorhynchus mykiss, Squalius cephalus) samples were conducted either by stripping voltammetry (Zn, Cd, Pb and Cu) or cold vapour atomic absorption spectrometry (Hg). The concentration of dissolved trace metals in water was very low revealing a pristine aquatic environment (averages were, in ng/L: 258 (Zn), 10.9 (Cd), 11.7 (Pb), 115 (Cu) and 1.22 (Hg)). Slightly enhanced concentrations of Cd (up to 50 ng/L) and Zn (up to 900 ng/L) were found in two main water springs and are considered as of natural origin. Observed downstream decrease in concentration of Cd, Zn and Cu in both water and sediments is a consequence of the self-purification process governed by the formation and settling of authigenic calcite. Anthropogenic pressure was spotted only in the Kozjak Lake: Hg concentrations in sediments were found to be up to four times higher than the baseline value, while at two locations, Pb concentrations exceeded even a probable effect concentration. The increase of Hg and Pb was not reflected on their levels in the fish tissues; however, significant correlations were found between Cd level in fish tissues (liver and muscle) and in the water/sediment compartments, while only partial correlations were estimated for Zn and Cu. A high discrepancy between values of potentially bioavailable metal fraction estimated by different modelling programs/models raised the question about the usefulness of these data as a parameter in understanding/relating the metal uptake and their levels in aquatic organism. The aquatic environment of the Plitvice Lakes National Park is characterized, in general, as a clean ecosystem.
Radiocarbon activity (a
14
C) and
13
C composition (δ
13
C) were measured in hygrophyte and mesophyte (land) mosses collected in the natural habitat of the Plitvice Lakes and along the Zrmanja and ...Krupa Rivers (typical continental and Mediterranean climates, respectively), Croatia. a
14
C and δ
13
C values of mosses, of atmospheric CO
2
and dissolved inorganic carbon (DIC) were compared with contemporary data and with data from 30 years ago at the Plitvice Lakes when
14
C activity of atmospheric CO
2
was ∼30% higher. A positive correlation between a
14
C
moss
and δ
13
C
moss
was observed for all data reflecting the change of carbon isotopic composition in DIC along the water flows and in atmospheric CO
2
regardless of the climatic regions and historic period. Fraction of the atmospheric carbon in moss
and carbon fractionation factor from aquatic CO
2
(DIC) to moss tissue
were calculated for each individual moss. Three species of mosses had ω
atm.C
∼ 0 % implying that they turn to anabiosis during dry periods. The relation
differentiates true aquatic and amphiphyte mosses. The first had a statistically significant negative correlation between
and
. The amphiphyte mosses had lower
with higher water flow rates.
Fecal indicator bacteria (FIB) have widespread use as indicators of water quality and health hazards. The purpose of this study was to determine distributional patterns of FIB and to assess their ...origin on several sites in spring area and in vertical profile of Proscansko Lake in Plitvice Lakes National Park. The study was conducted from March to January 2013 on 9 sampling sites. Standard microbiological methods were used to determine densities of total coliforms (TC), fecal coliforms (FC), fecal streptococcus (FS), Pseudomonas aeruginosa (PS) and Clostridium perfringens in water samples. Source area sustained higher densities of FIB compared to Proscansko Lake, throughout the study period. Sampling site White River below the village had highest values of certain FIB, indicating Plitvicki Ljeskovac as main fecal pollution source. There were seasonal differences in TC and FC with July and October displaying increased densities, the latter probably due to heavy rainfall. The ratio FC/FS in July indicated contamination of mainly animal origin. At the sampling site of Matica River estuary in Proscansko Lake, an increased densities of TC and FC bacteria were observed compared to other sites and depths, possibly due to source streams influence and stratification conditions. This study showed that the indicator bacteria of fecal contamination in the spring area of the Plitvice Lakes National Park are present and their quantity and distribution patterns depend on season, weather conditions and different effects in water column of the lake.
Plitvice Lakes National Park (PLNP) is the oldest protected area in Croatia (since 1949) and was placed on the UNESCO World Heritage List in1979. It is an area of outstanding universal value ...consisting of a freshwater ecosystem of 16 lakes divided by tufa barriers. Recently, this area has experienced pressure from visitors and significant infrastructural development. When the previous Management Plan expired in 2017, the PLNP initiated and adopted a new Management Plan. This involved the zonation of management in order to better conserve and use this protected area. Management zonation was based on spatial and other data on the distributions of the species and habitats (Natura 2000 and others); cultural values and geo-localities; visitor experiences; existing and planned infrastructure and settlements. Visitor classes and zones were determined using the Recreation Opportunity Spectrum (ROS) methodology. The new management zonation resulted in an increase of 13.9% in the area of the Park included in the Strict Conservation Zone, while succession and habitat degradation resulted in a decrease in the area of the Park in the Active Management Zone, especially in terms of grassland. Six ROS classes were defined. The established ROS classes and the new management zonation were interconnected, each reflecting the need to manage the protected area in terms of conserving its specific biodiversity and geodiversity, while offering visitors various experience opportunities and meeting the needs of the local community.
Biological denitrification Grgas, Dijana; Landeka Dragičević, Tibela; Štrkalj, Anita ...
Hrvatski časopis za prehrambenu tehnologiju, biotehnologiju i nutricionizam,
06/2021, Letnik:
16, Številka:
1-2
Journal Article
Ubrzani napredak industrije, poljoprivrede i domaćinstva su pogodovali povišenim koncentracijama dušika u vodenom ekosustavu, što uzrokuje
eutrofikaciju. Dušik se iz otpadne vode uklanja procesom ...biološke denitrifikacije. U ovom preglednom radu dan je osvrt na denitrifikaciju, s aspekta
mikroorganizama, koncentracije otopljenog kisika, donora i akceptora elektrona.
The accelerated progress of industry, agriculture and households favoured the elevated nitrogen concentrations in the aquatic ecosystem, which
cause eutrophication. Nitrogen is removed from wastewater by biological denitrification. This review deals with denitrification, from the aspect of
microorganisms, dissolved oxygen concentration, electron donors and acceptors.
Biološka denitrifikacija Grgas, Dijana; Štefanac, Tea; Galant, Mirjana ...
Hrvatski časopis za prehrambenu tehnologiju, biotehnologiju i nutricionizam,
06/2021, Letnik:
16, Številka:
1/2
Journal Article
Odprti dostop
The accelerated progress of industry, agriculture and households favoured the elevated nitrogen concentrations in the aquatic ecosystem, which cause eutrophication. Nitrogen is removed from ...wastewater by biological denitrification. This review deals with denitrification, from the aspect of microorganisms, dissolved oxygen concentration, electron donors and acceptors.
Aerobni granulirani mulj u obradi otpadnih voda Landeka Dragičević, Tibela; Štrkalj, Anita; Brozinčević, Andrijana ...
Hrvatski časopis za prehrambenu tehnologiju, biotehnologiju i nutricionizam,
06/2021, Letnik:
16, Številka:
1-2
Journal Article
Odprti dostop
Aerobni granulirani mulj (AGS, engl. Aerobic Granular Sludge) predstavlja obećavajuću tehnologiju u obradi otpadnih voda kućanstva i industrije.
Aerobne granule su samoimobilizirane mikrobne ...nakupine, bez nosača, a karakterizira ih kompaktna gusta struktura, visoko zadržavanje biomase,
visoka učinkovitost uklanjanja onečišćenja i svojstvo brzog taloženja. Na formiranje i stabilnost aerobnog granuliranog mulja utječu brojni
čimbenici, poput koncentracija otopljenog kisika, vrijeme prozračivanja, vrsta izvora ugljika, sile smicanja, period gladovanja, vrijeme taloženja.
Zbog slojevite strukture granule, sa vanjskim aerobnim slojem i anoksičnim i anaerobnim zonama prema središtu granule, moguće je istovremeno
uklanjanje C, N i P. AGS tehnologija ima potencijal smanjenja infrastrukture i operativnih troškova pročišćavanja otpadnih voda. Ovaj rad daje
pregled najnovijih spoznaja iz literature o mehanizmu granulacije i svojstvima aerobnih granula.
Aerobic granular sludge (AGS) is a promising technology in domestic and industrial wastewater treatment. Aerobic granules are self-immobilized
microbial aggregates, without carriers, characterized by compact dense structure, high retention of biomass, high efficiency for pollution removal,
and good settling ability. The formation and stability of aerobic granular sludge are influenced by a number of factors, such as dissolved oxygen
concentrations, aeration time, type of carbon source, shear forces, starvation period, settling time. Due to the layered structure of the granule, with
an outer aerobic layer and anoxic and anaerobic zones towards the center of the granule a simultaneous removal of C, N and P is possible. AGS
technology has the potential to reduce infrastructure and operating costs of wastewater treatment. This work presents an up-to-date review of the
literature focusing on AG granulated mechanism and properties of aerobic granules.
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