The change in dissolved inorganic δ13C in the ocean resulting from the change in δ13C in atmospheric CO2 owing to anthropogenic activities (the Suess effect) is well known. The need to correct for the Suess effect when applying δ13C in organic matter in lacustrine sediment deposited during the anthropocene as a productivity proxy, is widely although not universally acknowledged. This paper reviews conceptions about the Suess effect in lacustrine δ13Corg and methods to adjust for the Suess effect when δ13Corg is used to infer recent changes in aquatic productivity. Lake Tanganyika is used as an example to illustrate the necessity of the correction. When the Suess effect is not considered, interpretations of sediment core data can result that are opposite to those achieved with the correction applied, as is here shown in Lake Tanganyika and in other lakes. A new method to correct for the Suess effect is provided which has the advantage of being applicable to data for a larger period (1700–2000) than methods currently available. In addition, Lake Tanganyika is shown to be a net sink for CO2.

The need to correct for the Suess effect in the application of δ13C in sediment of autotrophic Lake Tanganyika, as a productivity proxy in the Anthropocene

A global synthesis of stable nitrogen isotopic values in lacustrine sediments indicates a period of declining enrichment from 15,000 to 7,000 years before present, probably in response to terrestrial carbon sequestration. Reactive nitrogen supply has increased significantly since the industrial revolution. It remains unclear, however, whether nitrogen availability — the supply of nitrogen relative to the demand from plants and microbes — has increased on a global scale. This study explores patterns of nitrogen cycling during the past 15,000 years with the help of previously published nitrogen isotope data from lake sediments around the world. Kendra McLauchlan et al. find that between 15,000 and 7,000 years ago, global terrestrial ecosystems experienced a prolonged decline in nitrogen availability, and propose that this might be the consequence of global changes in carbon dynamics. Surprisingly, there was no coherent trend in nitrogen cycling during the past 500 years, suggesting that modern increases in atmospheric carbon dioxide and net carbon sequestration in the biosphere may have compensated for increased supplies of reactive nitrogen in some ecosystems. Human activities have doubled the pre-industrial supply of reactive nitrogen on Earth, and future rates of increase are expected to accelerate1. Yet little is known about the capacity of the biosphere to buffer increased nitrogen influx. Past changes in global ecosystems following deglaciation at the end of the Pleistocene epoch provide an opportunity to understand better how nitrogen cycling in the terrestrial biosphere responded to changes in carbon cycling. We analysed published records of stable nitrogen isotopic values (δ15N) in sediments from 86 lakes on six continents. Here we show that the value of sedimentary δ15N declined from 15,000 years before present to 7,056 ± 597 years before present, a period of increasing atmospheric carbon dioxide concentrations and terrestrial carbon accumulation2. Comparison of the nitrogen isotope record with concomitant carbon accumulation on land and nitrous oxide in the atmosphere suggests millennia of declining nitrogen availability in terrestrial ecosystems during the Pleistocene–Holocene transition around 11,000 years before present. In contrast, we do not observe a consistent change in global sedimentary δ15N values during the past 500 years, despite the potential effects of changing temperature and nitrogen influx from anthropogenic sources. We propose that the lack of a single response may indicate that modern increases in atmospheric carbon dioxide and net carbon sequestration in the biosphere have the potential to offset recent increased supplies of reactive nitrogen in some ecosystems.

Changes in global nitrogen cycling during the Holocene epoch

Historical changes in polycyclic aromatic hydrocarbons (PAHs) input in Lake Baiyangdian related to regional socio-economic development.

Zero-valent iron/iron oxide-oxyhydroxide/graphene as a magnetic sorbent for the enrichment of polychlorinated biphenyls, polyaromatic hydrocarbons and phthalates prior to gas chromatography-mass spectrometry.

Re-investigating fish consumption in Greek antiquity: results from δ13C and δ15N analysis from fish bone collagen

We measured accumulation rates of organic carbon (OC) and total nitrogen (TN) and stable carbon (d 13 Corg) and nitrogen isotopes (d 15 N) in the sediments of two mountain lakes (Lake Ledvica and Lake Planina, northwest Slovenia). Marked variations of these parameters were observed in both sediments. OC accumulation rates ranged from 4t o 23 gm 22 yr 21 in Lake Ledvica, whereas in Lake Planina they were one order of magnitude higher and increased substantially in the upper sediments. d 13 Corg and d 15 N decreased upward in Lake Ledvica, from 225.5‰ to 228.4‰, and from 12.1‰ to 23.4‰, respectively. In contrast, substantial variations in the d 13 Corg profile, ranging from 230.9‰ to 237.4‰, but a quite uniform d 15 N profile of approximately 11.8‰, was observed in Lake Planina. Elemental and isotopic changes of bulk sedimentary organic matter in the lakes were related to changes in the past trophic state of the lakes and their watersheds, inferred by natural development of the lake ecosystems, anthropogenic activities, as well as earthquakes and forest fires. Observed changes and differences in the d 13 Corg and d 15 N records could be attributed to global changes in isotopic composition of atmospheric CO2 and nitrate in atmospheric deposition, as well as to differences in organic matter, dissolved inorganic carbon, and dissolved inorganic nitrogen sources at various altitudes. Although Lakes Ledvica and Planina are remote mountain lakes, the sediment records showed severe eutrophication in Lake Planina, whereas in Lake Ledvica eutrophication is still moderate, thus reflecting a high sensitivity of these ecosystems to any external inputs. The organic matter accumulated in lake sediments constitutes an important fraction that provides crucial information in studies of the lacustrine paleoenvironment, the history of climate change, and the effects of man on local and regional ecosystems. It is introduced to lakes by multiple pathways (Meyers and Ishiwatari 1995; Herczeg et al. 2001). Terrigenous (allochthonous) organic matter, originating mostly from the catchment area via tributaries, consists mainly of degraded remains of leaves and grass and soil organic matter, as well as material that falls directly into the lake from the riparian zones. Additional contributions from more distant sources are delivered by precipitation and wind. On the other hand, biota (animals, plants, and bacteria) within the water column and the sediments contribute aquatic (autochthonous) organic matter. The different types of biota populating a lake and its watershed produce organic matter having a distinctive biochemical composition. Changes in the community structure of these biota create variations in the amounts and types of organic matter deposited at different times in the history of a lake (Meyers and Ishiwatari 1995). 1

Changes in accumulation of organic matter and stable carbon and nitrogen isotopes in sediments of two Slovenian mountain lakes (Lake Ledvica and Lake Planina), induced by eutrophication changes

Sediment organic matter (OM) and its stable carbon and nitrogen isotopes were studied in 12 Slovenian mountain lakes in the Julian Alps. The lakes have different catchment areas and display a range of trophic states. Surface sediment atomic C/N ratios ranged from 8.4 to 13.2. Based on these C/N ratios, we concluded that autochthonous OM dominates in these lakes and constitutes approximately 65–92% of the total OM. Higher contributions of autochthonous OM sources were observed in lakes above the tree line. Relatively constant C/N ratios in the deeper sediments suggest that degradation processes are most intense in the upper few centimetres of the sediments and/or that remaining OM is relatively resistant to further degradation. Surface sediment δ13C and δ15N values ranged from −36.1 to −14.1‰ and from −5.2 to +1.1‰, respectively. In sediment cores from seven lakes, higher δ13C and lower δ15N values characterize oligotrophic lakes situated above the tree line, whereas the reverse is true for eutrophic lakes below the tree line that are also exposed to more anthropogenic impact. Carbon and nitrogen biogeochemical cycling differs considerably among the lakes. Stratigraphic shifts in carbon, total nitrogen, C/N ratios and stable C and N isotopes in cores record changes in inputs, and hence water column processes, as well as alterations in loading to the lakes. The stratigraphic variations are also the result of post-depositional diagenetic changes in the upper few centimetres of sediment. All the lakes show impacts from recent increases in atmospheric deposition of dissolved inorganic nitrogen. Application of sediment OM analysis thus proved to be useful to reconstruct paleoecological changes in sensitive mountain lake ecosystems that are either natural and/or anthropogenically derived.

Sediment organic matter in mountain lakes of north-western Slovenia and its stable isotopic signatures: records of natural and anthropogenic impacts

Lake Pamvotis is a shallow Mediterranean lake located in northwestern Greece that has been recognized as an internationally important conservation site. Here, an unprecedented investigation was undertaken to obtain and evaluate data related to sedimentary organic matter, hydrocarbon content, and stable isotopes of Lake Pamvotis sediments, thus tracking the origin of organic inputs and providing a record of environmental status. The study revealed a distinct spatial distribution of polycyclic aromatic hydrocarbons (PAHs) with values between 34.7 and 1600 μg/kg and a rather uniform pattern for n-alkanes with concentrations falling below 41.4 μg/g. A significant contribution of an unresolved complex mixture indicated anthropogenic petroleum contamination. Further study of relevant indexes and geochemical biomarkers supported a mixed-source input of aliphatic hydrocarbons. With regard to PAHs, there was strong evidence that their dominant origin is pyrogenic. Finally, considerable excursion in δ13Corg was attributed to changes in dissolved inorganic carbon accompanied by increased input of effluents and recycling of organic carbon within the lake, whereas the rise in isotopic composition of nitrogen was associated with agricultural runoff and sewage input from the town of Ioannina.

Recent Environmental Changes in the Shallow Lake Pamvotis (NW Greece): Evidence from Sedimentary Organic Matter, Hydrocarbons, and Stable Isotopes

http://www.geologija-revija.si/dokument.aspx?id=1012

C and N elemental and stable isotopic signatures in sedimentary organic matter from Lake Pamvotis (Greece)

In the present study we explore the applicability of carbon and nitrogen stable isotope signatures in sedimentary organic matter to trace changes in lake trophic state in four highmountain lakes in Triglav National Park (NW Slovenia). Results show higher dCorg values associated with lower d15N values that are characteristic of oligotrophic lakes, while lower dCorg values are associated with higher d15N values that are characteristic of eutrophic lakes. limniju nastala organska snov tone in se razgrajuje s pomo~jo akceptorjev elektronov (O2, NO3, MnO2, Fe2O3, SO4, CO2 in organske molekule z majhnimi molekulskimi masami) v spodnjem delu vodnega stolpca (hipolimniju). Oksidacija s kisikom je najbolj energetska reakcija in do nje pride najprej. Ko se kisik porabi, pride do denitrifikacije, nato do redukcije manganovih oksidov, nitrata in ‘elezovih oksidov, sulfatne redukcije ter nastanka metana. Napredovanje k manj energetskim reakcijam ka‘e tudi na splo{no ni‘anje Eh v sedimentu in s tem bolj redukdoi:10.5474/geologija.2002.073 608 Polona Vre~a & Gregor Muri cijske pogoje ( F r o e l i c h et al., 1979, C a n f i e l d , 1993, A p p e l o & P o s t m a , 1994). Pri razgradnji organske snovi nastajajo reducirane kemijske zvrsti (N2, Mn2+, NH4, Fe2+, H2S in CH4), kar privede do pojava hipoksi~nih ali celo anoksi~nih razmer v hipolimniju ( F r o e l i c h et al., 1979, F u r r e r & W e h r l i , 1996). Slednje je zna~ilno za visoko produktivna jezera, kjer je preskrba akceptorjev elektronov znatno omejena. Tudi v prisotnosti kisika lahko v teh okoljih prevladujejo anaerobni procesi, saj porabljajo kisik mikroorganizmi za oksidacijo CH4, H2S in NH4, nastalih med razgradnjo organske snovi ( S w e e r t s et al., 1991, Sinke et al., 1992). Pomankanje kisika v hipolimniju tudi upo~asni razgradnjo organske snovi, zato se na jezerskem dnu in v sedimentu le ta kopi~i. S procesom evtrofikacije je tako povezano spreminjanje fizikalno-kemijskih lastnosti vodnega stolpca, ki dolo~ajo trofi~no stanje jezera in na osnovi katerih lo~imo ultera-oligotrofna, oligotrofna, mezotrofna, evtrofna in hiperevtrofna jezera ( O E C D , 1982). Zaporedje navedenih trofi~nih stopenj predstavlja ontogenetski razvoj posamezne-

Gregor Muri

Papers

Changes in accumulation of organic matter and stable carbon and nitrogen isotopes in sediments of two Slovenian mountain lakes (Lake Ledvica and Lake Planina), induced by eutrophication changes

Sediment organic matter in mountain lakes of north-western Slovenia and its stable isotopic signatures: records of natural and anthropogenic impacts

Recent Environmental Changes in the Shallow Lake Pamvotis (NW Greece): Evidence from Sedimentary Organic Matter, Hydrocarbons, and Stable Isotopes

C and N elemental and stable isotopic signatures in sedimentary organic matter from Lake Pamvotis (Greece)

Stable isotopic composition of sedimentary organic carbon and nitrogen as indicator of trophic state changes in high-mountain lakes in the Julian Alps