Procena trofičkog statusa akumulacije očaga (Lazarevac, Srbija) posredstvom Carlsonovog indeksa

Trofički status se može definisati kao ukupna težina živog biološkog materijala (biomase) u nekom vodenom telu na određenom lokalitetu i u određeno vreme. Trofički status nekog vodenog tela može se proceniti na osnovu merenja specifičnih parametara i predstavlja biološki odgovor na spoljašnje faktore, kao što su količina nutrijenata, sezonske promene, ispaša, mešanje vode itd. Procena trofičkog statusa jezera ili akumulacije je od velikog značaja. Postoje različiti kriterijumi za procenu trofičkog stanja jezera, kao što su: koncentracija nutrijenata, produktivnost, kvantitativni i kvalitativni sastav flore i faune, dostupnost kiseonika i morfometrija jezera. Međutim, imajući u vidu da je multiparametarski indeks nepraktičan, Carlson je predložio indekse trofičkog stanja (TSIs) koji su znatno jednostavniji za upotrebu od multiparametarskog indeksa. Ovi indeksi kao bazu za klasifikaciju trofičkih stanja koriste algalnu biomasu. U tom smislu koriste se tri parametra za izračunavanje ovih indeksa: koncentracija hlorofila a, ukupni fosfor i providnost izmerena Secchi diskom. Svaka od ove tri promenljive se može koristiti za klasifikaciju statusa vodenog tela, ali je hlorofila a najznačajniji parametar s obzirom da je direktni pokazatelj algalne biomase. Opseg Carlson-ovog trofičnog indeksa obuhvata vrednosti od 0 do 100. Vrednosti ispod 40 odgovaraju oligotrofnim, od 40 do 50 mezotrofnim, od 50 do 70 eutrofnim, a preko 70 hipereutrofnim jezerima i akumulacijama. Glavna prednost ovog indeksa je što odnos između tri parametra može ukazati na određene uslove koji vladaju u datom jezeru ili akumulaciji, a tiču se faktora koji limitiraju algalnu biomasu ili utiču na izmerene parametre. Iako određivanje trofičkog statusa vode nekog vodenog tela ne treba poistovećivati sa samim kvalitetom vode, ono, svakako, predstavlja značajan aspekt istog. Cilj ovog istraživanja bio je određivanje trofičkog statusa jezera Očaga na osnovu Carlson-ovog trofičnog indeksa i ispitivanje veze između izračunatih indeksa za hlorofil a (TSI(CHL)), ukupni fosfor (TSI(TP)) i providnost merenu Secchi diskom (TSI(SD)). Veštačko jezero Očaga nalazi se u blizini Lazarevca i isključivo se koristi za rekreaciju. Ispitivanje vode rađeno je jednom nedeljno tokom jula i avgusta, od 2012. do 2014. godine. Sve analize urađene su u Zavodu za javno zdravlje iz Beograda. Vrednosti dobijenih indeksa (TSIs) varirale su od 41 do 86.25, u ispitanom periodu, a jezero je menjalo status od mezotrofnog, preko eutrofnog do hipereutrofnog, pri čemu su eutrofni uslovi preovladavali. Hipereutrofija je zabeležena tokom avgusta 2013. Godine, kada su bile izmerene i najveće vrednosti sva tri parametra, što je, verovatno, rezultat organskog opterećenja vodenog ekosistema i vremenskih uslova. Prema podacima RHMZ-a, 2013. godina je bila jedna od najtoplijih i najsušnijih godina još od 1951. godine. Nasuprot tome, u avgustu 2014. godine izmerene su najmanje vrednosti svih parametara, što ukazuje na mezotrofne uslove u jezeru te godine. Mezotrofni status jezera je, verovatno, posledica velike količine padavina u prvoj polovini te godine, ali i pražnjenja i ponovnog punjenja jezera nakon majskih poplava

Radioactivity and Measurements of Sediment Deposition Rate of the Drenova Reservoir (B and H)

This work presents the first estimate of the radioactivity and sediment deposition rate of the Drenova reservoir. The radioactivity and sedimentation rate were computed applying the Pb-210 and Cs-137 methods. Samples of Pb-210 and Cs-137 were taken from four boreholes drilled in the Drenova reservoir in June 2010. Vertical distribution of the natural and artificial radionuclides in four boreholes was examined using a gamma spectrometry measurement with HpGe detectors, Gamma X type (10 keV-3 MeV). Activities ranging from 122-8 Bq/kg were found for Pb-210, and from 140-0.8 Bq/kg for Cs-137. The sedimentation rate in the Drenova reservoir varied from 1.96 to 2.90 cm per year for unsupported Pb-210 and 0.47 to 5.33 cm per year for Cs-137

The effect of meteorological and chemical parameters on summer phytoplankton assemblages in an urban recreational lake

The summer phytoplankton community was studied across both vertical and temporal scales in relation to environmental factors in the shallowrecreational Sava Lake. The sampling was conducted weekly at four depths from mid-July until mid-September 2014, in order to detect short-term changes within the assemblages. Besides physical and chemical parameters, meteorological data was also included in the investigation, as that year was characterized with extreme rainfall, which caused serious flooding in the region. The community succession was characterized by a reverse in the cyanobacteria (Codon M) and chlorococcal green algae (Coda F and J). Statistical analyses (RDA) indicated that changes in the community composition and successional pattern could have been due to the mixing regime variations in the reservoir, most likely induced by weather disturbances, especially high precipitation and wind events. These events did not permit massive cyanobacterial development, although they most likely caused resuspension of dissolved phosphorus from the sediment. When observing functional groups, three groups could be distinguished by their response to the above-mentioned parameters: the first prefers high temperature and insolation(Lm, Y, Lo, Xph, W2andM), the second is correlated with precipitation and wind (Td, C, K, MP and X2), while the third group tolerates cloudiness (H1, F, N, X1, D, J and P)

Fertility trends in Serbia during the 1990s

The 1990s represent an exceptionally complex period for the population of Serbia. In addition to the impact of long-term factors, various tumultuous events affected its demographic development, such as breaking apart of former Yugoslavia, armed conflicts in the neighboring countries, sanctions imposed by the international community, social changes (transition transformation or regression), deep economic crisis, collapse of social stratification political problems, institutional crisis, and NATO military intervention. Maladjustment to the changed system of values and norms, lower level of personal attainment, feeling of insecurity, and living under permanent stress are the main features of life at an individual psychological level. Deprivation or living at the subsistence level are the main elements of the economic cost sustained by the majority of the population. How have these changes affected an individual's decision to have children? The analysis of futility indicators points to an obvious decline in the number of births across low fertility regions of Serbia. Also, the analysis has raised the question why the decline in population fertility in the low fertility regions was not even higher, bearing in mind the experiences undergone by the countries with economy in transition as well as the depth of the crisis in society. In that sense several factors come to mind. The most important are the universality of marriage socio-psychological investigations confirmed domination of the traditional character or mentality in Serbia during the 1990s, and the government’s approach to the issue of fertility improved during this time. Besides demographic needs were carefully taken into account in all amendments to the old and formulation of the new measures in the area of social policy. Mention should be made of measures ensuring employment rights of women and their entitlement to maternity leave, maternity pay, and provision of institutionalized care for the children. On the other hand under-reporting of live births, lack of knowledge on the size and characteristics of emigration flows limited the analysis of population fertility in Kosovo and Metohia. But, registered data as well as survey results show to the perseverance of the fertility model of transitional type displaying obvious traditional elements

Test Anxiety in Pre-Exam Period and Success of Nursing Students

The aim of this study was to examine the presence of preexam anxiety in nursing students and establish relationship of pre-exam anxiety intensity in relation to the category variables (gender, age, place of birth, current place of residence, with whom they live, whether they are employed, the average family income, year of study), objective success (i.e., pass rate at exams, the average score at the end of year, possible renewal of the year of study) and the subjective perception of academic success (i.e., self-satisfaction as a student as well as the importance of ratings obtained at the exam). The sample was random and consisted of the students of High Medical College of Professional Studies in Belgrade at the Department of vocational nurse. 209 students were tested, evenly distributed on the second and third year of study. Pre-examination anxiety among students was examined using a questionnaire The Test Anxiety Inventory – TAI (Test Anxiety Inventory), which includes subscales: Test Anxiety Inventory-Total (TAI-T), Test Anxiety Inventory-Worry (TAI-W) and Test Anxiety Inventory-Emotionality (TAI-E). From the obtained results we can conclude that nursing students showed a statistically significant pre-exam anxiety on all subscales. Preexam anxiety symptoms compared to candidates’ sex showed statistically significant differences in all scores, and average values are always higher in female students compared to male. There is also a statistically significant difference between students of the second year in relation to the third year students. It can be concluded that there is a significant number of nursing students with the pre-exam anxiety problems that need professional help and support in the form of expanding and strengthening personal competencies