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

Pyridazines. LXXVIII. Use of N,N-Dimethylaminomethylene Derivatives of Some Amino and Hydrazino Heterocycles in Organic Synthesis

The formation of N,N-dimethylaminomethylenehydrazino derivatives of pyridazine and azolopyridaz~nes is described and th.e synthetic utility of these compounds is explored. An unusual transformation could be observed with a aminomethyleinehydrazino derivative where upon .nitrosation the side chain is trainsformed into an azido group. From the corresponding N,N-dimethylaminomethyleneamino derivatives two new tricyclic azolotriazolopyridazmes could be prepared

Pyridazines. LXXVIII. Use of N,N-Dimethylaminomethylene Derivatives of Some Amino and Hydrazino Heterocycles in Organic Synthesis

The formation of N,N-dimethylaminomethylenehydrazino derivatives of pyridazine and azolopyridaz~nes is described and th.e synthetic utility of these compounds is explored. An unusual transformation could be observed with a aminomethyleinehydrazino derivative where upon .nitrosation the side chain is trainsformed into an azido group. From the corresponding N,N-dimethylaminomethyleneamino derivatives two new tricyclic azolotriazolopyridazmes could be prepared

Klorirani ugljikovodici (pesticidi i poliklorobifenili - PCB) u atmosferi grada Ljubljane

Airborne particulate matter was continuously sampled from the atmosphere of the residential town area of Ljubljana for 45 days and trapped on a filter. Some chlorinated hydrocarbons (pesticides and PCBs) were determined by GLC after solvent extraction followed by concentration and clean-up of the oily residue. The PCB concentration in the particulate matter in the atmosphere was 1.3 ng/m3 and the concentration levels of the total DDT. dieldrin, alpha-, gamma-, delta-HCH and heptachlor epoxide were 0.86, 0.03, 0.08, 0.05, 0.03 and 0.01 ng/m3 respectively. Such a level of chlorinated hydrocarbons in the atmosphere is considered of little or no consequence to public health.U soliteru »Iskra« u Ljubljani neprekidno smo 45 dana usisavali vanjski zrak kroz filter. Filter je zadržao čestice aerosola. U tom smo aerosolu tehnikom plinske kromatografije identificirali neke stabilne organskofosforne spojeve (pesticide i poliklorirane bifenile). Našli smo da je koncentracija PCB 1,3 ng/m3, a ukupnog DDT (p,p\u27-DDE, p,p\u27-DDE, p,p\u27-DDD i o,p\u27-DDT), dieldrina, alfa-, gama-, delta-HCH i heptaklor epoksida 0,86; 0,03; 0,05; 0,03; 0,01 ng/m3. Količina organoklornih spojeva u zraku ne prelazi količinu koja bi znatno utjecala na ukupni dnevni unos u čovjeka

Major, Minor and Trace Elements in Surficial Sediments from the Open Adriatic Sea: A Regional Geochemical Study

The concentrations and distributions of major (Al, Ca, Fe, K, Mg), minor (Mn, P, Ti), and trace elements (Ag, As, Ba, Be, Co, Cr, Cu, Ag, La, Ni, Pb, Sc, Sr, Th, U, V, Zn, Zr), in the surficial sea bottom sediments were studied in an attempt to establish their distribution in the Adriatic Sea. Results indicate that major, minor and several trace elements are strongly related to the catchment geology, their distribution being essentially controlled by the type of sediments. However, the majority of trace elements are believed to have been introduced into the Adriatic from the riverine inflows that are also affected by the impact of industrial, mining and urban wastes. Other sources of these elements are located along the coast. The highest concentrations for several trace elements were thus recorded from the coastal ecosystems and from the most polluted Albanian and Italian rivers. The concentrations of trace elements generally decrease with distance from the coast. The regional distribution patterns are influenced by the counter-clockwise system of the Adriatic Sea currents which carry these elements away from the riverine inflows. Correlation analysis indicates that the trace elements are largely associated with the clay minerals, Fe and P contents rather than with the Mn concentrations. Magnesian minerals are suggested as the carrier for some trace elements (As, Co, Cr, Ni, Se and V) only in the southern Adriatic, which reflects their ophiolitic origin in the Albanian hinterland. Organic matter concentrations does not considerably influence the abundance and distribution of trace metals