Semi-annual carbon and nitrogen isotope variations in the water column of Lake Bled, NW Slovenia

The variability in the stable isotope signature of carbon and nitrogen in particulate organic matter and dissolved species in the water column of the mesotrophic subalpine Lake Bled in NW Slovenia has been determined. After the algae bloom from August to December in 2008, samples were taken from the deepest part of the lake which develops an anoxic hypolimnion for most of the year. C/N molar ratios and δ¹³C_POC and δ¹⁵N_PN values suggest an autochthonous source for particulate organic matter (POM). According to the isotope model, autochthonous carbon accounted for a major part of the particulate organic carbon (POC), ranging from 86% to 96% in September and October, while in December the proportion of allochthonous carbon was more pronounced, ranging from 57% to 59%. Low δ¹³C_POC and δ¹⁵N_PN values (from −36 to −33‰ and from 0.8 to 1.8‰), observed below 24 m in August and September, indicate the bacterial origin of POM, mainly from methanotrophic bacteria. δ¹⁵N_NO₃ and δ¹⁵N_PN values decreased with depth. The relations between δ¹⁵N_PN and NO₃^- and NH₄⁺ concentrations suggest that NH₄⁺ is the main assimilation species for nitrogen in POM. Nitrification was active between 12 and 18 m deep in September and October, indicated by increased NO₃^- concentrations and decreased δ¹⁵N_NO₃ values. The correlation between nitrate concentrations and δ¹⁵N_NO₃ values suggests active water column denitrification in October 2008. The decrease in δ¹⁵N_NO₃ values observed in December could be explained by degradation of organic matter, followed by nitrification of the degradation products. During our sampling period, there was no evident influence of sewage, agriculture, or atmospheric deposition on the nitrogen balance in the lake

Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

Mercury (Hg) natural biogeochemical cycle is complex and a significant portion of biological and chemical transformation occurs in the marine environment. To better understand the presence and abundance of Hg species in the remote ocean regions, waters of South Atlantic Ocean along 40°S parallel were investigated during UK-GEOTRACES cruise GA10. Total mercury (THg), methylated mercury (MeHg), and dissolved gaseous mercury (DGM) concentrations were determined. The concentrations were very low in the range of pg/L (femtomolar). All Hg species had higher concentration in western than in eastern basin. THg did not appear to be a useful geotracer. Elevated methylated Hg species were commonly associated with low-oxygen water masses and occasionally with peaks of chlorophyll a, both involved with carbon (re)cycling. The overall highest MeHg concentrations were observed in themixed layer (500m) and in the vicinity of the Gough Island. Conversely, DGM concentrations showed distinct layering and differed between the water masses in a nutrient-like manner. DGM was lowest at surface, indicating degassing to the atmosphere, and was highest in the Upper Circumpolar Deep Water, where the oxygen concentration was lowest. DGM increased also in Antarctic Bottom Water. At one station, dimethylmercury was determined and showed increase in region with lowest oxygen saturation. Altogether, our data indicate that the South Atlantic Ocean could be a source of Hg to the atmosphere and that its biogeochemical transformations depend primarily upon carbon cycling and are thereby additionally prone to global ocean change

Nutritional properties of beer

Namen diplomskega dela je bil predstaviti prehranske lastnosti piva. Pivo je alkoholna pijača, ki vsebuje pomembne prehranske snovi kot so vitamini (predvsem vitamini B kompleksa), minerali (magnezij, kalij in fosfor), nekaj topne prehranske vlaknine in antioksidante. Najpomembnejši antioksidanti v pivu so fenolne spojine, kjer jih 70 % izvira iz ječmenovega slada in 30 % iz hmelja. Sestava antioksidantov v različnih vrstah piva je odvisna predvsem od sestave osnovnih surovin in tehnološkega procesa. Pivo vsebuje tudi pomembne spojine iz hmelja: izohumolone, ki naj bi imeli pozitivno vlogo pri preprečevanju srčno žilnih bolezni, ksantohumol, ki kaže protirakavo delovanje in 8-prenilnaringenin, ki ima najmočnejšo estrogeno aktivnost med fitoestrogeni, kar naj bi vplivalo na zmanjševanje intenzitete simptomov menopavze. V drugem delu naloge smo pregledali literaturo povezano z različnimi učinki alkohola na zdravje ljudi. Nekatere študije kažejo, da ima lahko zmerno uživanje alkohola ugoden vpliv na zdravje ljudi, predvsem pri zaščiti pred srčno žilnimi boleznimi. Zloraba alkohola lahko negativno vpliva na človeško zdravje. Posledice prekomernega uživanja alkohola se manifestirajo kot povečano tveganje za razvoj različnih vrst raka, ciroze jeter, možganske kapi in zasvojenosti z alkoholom.The aim of the graduation thesis was to present the nutritional properties of beer. Beer is an alcoholic beverage that contains important nutrients such as vitamins (above all B complex vitamins), minerals (magnesium, potassium in phosphorus), some soluble dietary fiber and antioxidant. The most important antioxidants in beer are the phenolic compounds, where 70 % comes from barley malt and 30 % from hops. The composition of antioxidants in different types of beer depends on composition of raw materials and technological process. Beer also contains important hops compounds: isohumolones, which should perform a positive role in preventing cardiovascular disease, xanthohumol with anti-cancer activity, and 8-prenylnaringenin with the strongest estrogenic activity among phytoestrogens, which is expected to reduce the intensity of menopausal symptoms. In the second part of the thesis we reviewed the literature related to different effects of alcohol on human health. Some studies report that moderate alcohol consumption can have a beneficial effect on human health especially in regard with cardiovascular disease protection. Alcohol abuse can have a negative impact. The consequences of excessive alcohol consumption are increased risk of various cancers, cirrhosis, stroke and alcohol addictio

Gap dynamics in beech polewood stands after thinning with CTL technoloy

Leta 2010 je bil oddelek 13 v gozdnogospodarski enoti Trnovo redčen s sistemom strojne sečnje. Po desetih letih smo ocenjevali, kakšne so značilnosti vrzeli v strehi sestojev, ki so nastale po redčenju v bukovih drogovnjakih. Izmerili smo širine krošenj dreves ob robovih vrzeli, nastalih po redčenju in analizirali vrzeli na podlagi podatkov laserskega skeniranja iz leta 2015 in ortofoto posnetkov iz leta 2020. Na podlagi ortofoto posnetkov ni bilo mogoče zanesljivo določiti zapiranja vrzeli. Iz terenskih meritev velikosti krošenj sklepamo, da drevesa ob robovih vrzeli razvijajo neenakomerno obliko krošnje. Kar 53 % dreves v vzorcu je imelo asimetrično krošnjo, v povprečju za 56 % širšo v smeri proti vrzeli. To lahko privede do večje ogroženosti za porušitev dreves, nastanek napak kot so kriva in ovalna debla, večvrhatost in ekscentričnost srca.In 2010, section 13 in the Trnovo forestry unit was thinned with a machine logging technology. After ten years, we assessed the characteristics of the gaps in the stand canopy that formed after thinning in beech pole stand. We measured tree canopy widths at the edges of the gaps created after thinning and analyzed the gaps based on laser scanning data from 2015 and orthophotos from 2020. Based on orthophotos, it was not possible to reliably determine the gap closure. From field measurements of canopy size, we conclude that trees develop an uneven canopy shape at the edges of the gap. As many as 53% of the trees in the sample had an asymmetrical canopy, averaging 56% wider toward the gap. This can lead to a greater risk of tree damage and formation of defects such as curved and oval trunks, multi-peakedness and eccentricity in the heart of tree

Obogatitev jogurta s plodovi rastline Hottentot-fig (Carpobrotus edulis L.)

Food additives are crucial in the food industry to ensure a longer shelf-life of food products, enable its mass production, widespread distribution, and expansion to new markets. But the intake of synthetic food additives is linked with a higher incidence of several health problems, including allergies and cancer. Additionally, consumers are determined in pursuing healthier habits by the use of foods promoting positive effects on health in addition to their basic nutritional purposes, i.e., functional foods. Salt-tolerant plants, i.e., halophytes, such as Carpobrotus edulis have evolved several adaptations in response to different stresses, such as high salinity levels, including the synthesis of highly bioactive compounds, such as phenolics. This is the first study done on the addition Hottentot-fig extract as an additive into yogurts, and it shows promising results. The incorporation of Hottentot-fig extract into dairy matrix showed a significantly higher antioxidant activity than the control sample at all storage times and can be considered as a source of phenolics. Moreover, the extracts showed to be nontoxic. Overall, the addition of extracts also did not negatively affect quality parameters such as syneresis and water holding capacity and possibly even improve the quality of yogurt, with phenolics interacting with yogurt proteins and stabilizing the gel matrix. In terms of physiochemical properties (pH and color) were not affected by the addition of the Hottentot-fig extracts. While the addition of the Hottentot-fig extracts caused a slight change in nutritional properties, such as increased ash content.Aditivi za živila so v živilski industriji ključnega pomena za zagotavljanje daljšega roka trajanja živil, s čimer omogočajo njihovo masovno proizvodnje ter širjenje na nove trge. Toda vnos sintetičnih aditivov v živila je povezan z večjo pojavnostjo zdravstvenih težav, vključno s pojavom alergij in rakavih obolenj. Potrošniki postajajo dandanes vse bolj ozaveščeni o zdravih prehranskih navadah. To se kaže v povečani uporabi t. i. funkcionalnih živil, ki poleg svojih osnovnih prehranskih funkcij izkazujejo dodatne, zdravju pozitivne učinke. Eno takih, potencialno funkcionalnih živil, smo raziskovali v naši nalogi, kjer smo kot osnovno živilo uporabili jogurt in ga obogatili z izvlečki rastline Carpobrotus edulis. Slednja je slanuša ali halofit, ki je razvila različne prilagoditve na okoljske obremenitve, kot so visoke ravni slanosti. To je prva študija o dodatku izvlečka olupkov Hottentot-fig v jogurte in kaže obetavne rezultate. V času shranjevanja so jogurti z dodatkom izvlečka izkazovali znatno večjo antioksidativno aktivnost kot kontrolni vzorci brez izvlečkov. Dodatek izvlečkov Hottentot-fig v jogurte bi tako lahko predstavljal prehranski vir bioaktivnih fenolnih spojin. Izkazalo se je tudi, da so izvlečki nestrupeni in niso negativno vplivali na kakovostne parametre, kot sta sinereza in sposobnost zadrževanja vode, temveč so jih morda celo izboljšali. Interakcije polifenolov z beljakovinami jogurta bi namreč lahko stabilizirale matriks jogurta. Dodatek izvlečkov ni vplival na fizikalno-kemijske lastnosti (pH in barvo) jogurtov, povzročil pa je rahlo spremembo hranilne sestave, med drugim povečanje vsebnosti pepela v obogatenih jogurtih

Determination of Iron in Environmental Water Samples by FIA-TLS

The determination of low concentration of iron in natural waters can be difficult due to the complexity of natural water, but primarily because it requires preconcentration of the sample with solvent extraction. In this work we report on results of thermal lens spectrometry (TLS) coupled to flow injection analysis (FIA) as a highly sensitive FIA-TLS method of iron detection. The concentration of iron redox species was determined using 1,10-phenanthroline (PHN), that forms stable complexes with Fe(II) ions which are characterized by an absorption maximum at 508 nm. The TLS system using a 633 nm probe laser and 530 nm pump laser beam was exploited for on-line detection in flow injection analysis, where a PHN solution was used as the carrier solution for FIA. The concentration of the complexing agent affects the quality of the TLS signal, and the optimal concentration was found at 1 mM PHN. The achieved limits of detection (LODs) for Fe(II) and total iron were 33 nM for Fe(II) and 21 nM for total iron concentration. The method was further validated by determining the linear concentration range, specificity in terms of analytical yield and by determining concentration of iron in a water sample from a local water stream