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The results of investigations on contents of several heavy metals in aquatic environments within the Danube Delta, Romania, are presented. The distribution of these heavy metals in the delta lakes was studied taking into consideration hydrochemical characteristics of the water catchment areas and the potential sources of contamination. The water sampling was done during several field campaigns in 2019, 2020 and 2021. A total of 143 water samples from 25 lakes, were collected for quantification of heavy metals content in water of studied lakes. The total concentration of technophile elements was determined using the ICP-EOS method. The results of analyses showed that the content of Cd, Co, Cr, Cu, Ni, Pb and Zn (µg/L) in the water samples were mainly within the acceptable limits set for Quality Class I (Very Good) and II (Good). Incidentally, the content of Cd (µg/L) reaches or exceeds the limit set for Quality Class III (moderate). In conclusion, the degree of heavy metal contamination in the investigated waters of the Danube Delta lakes is acceptably low and consequently presents a low environmental risk to aquatic life. In addition, the results obtained in three consecutive years showed that the environmental state of lakes is relatively stable. The results obtained concerning the heavy metals content in the water of Danube Delta inter-distributary depressions lakes represent a baseline data set that will be used for planning future delta water quality monitoring., {"references":["Alexe V., Burada A., Teodorof L., Marinov M., Doroșencu A.-C., Bolboacă L.-E., Despina C., Seceleanu D., Peraita M., Tudor M., Kiss J.B., Murariu D. (2021). Accumulation of chromium, cadmium and arsenic in white-tailed sea-eagle feathers (Aves: Haliaetus albicilla) from the Danube Delta Biosphere Reserve and surrounding areas (Romania). Turk. J. 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This study aims to compare the water quality in distinct aquatic systems, situated in different representative areas of the Danube Delta Biosphere Reserve, Romania - a unique natural area of national and international importance. These areas are largely populated by a vast diversity of aquatic organisms, including rare species of plants, animals, aquatic birds and fish, many of them being endangered species. Any imbalances in these ecosystems, owing to natural and human-induced changes in the water quality may affect aquatic life. In this sense, water samples were collected from the surface layer of a freshwater environment (i.e., Babina, Rădăcinoasele and Ciorticuț lakes), as well as from mixed environments (i.e., Musura and Sahalin Bays) during August 2018. The following water quality indicators were considered: temperature, pH, dissolved oxygen, nitrite-nitrogen, nitrate-nitrogen, ammonium-nitrogen, orthophosphates, chlorophyll a, total organic carbon, silica, electrical conductivity, total dissolved solids, sulphates, turbidity, total suspended solids, transparency and oxido-reduction potential. These parameters were analysed and discussed in relation to national and international environmental standards. Maps of spatial distribution of some quality parameters were obtained, showing variation as a result of local specific environmental circumstances, which change in time and space. These results suggest that the environmental indicators measured in drought conditions and low water levels showed generally good to moderate water quality status, in spite of many local triggers associated with natural and anthropogenic causes that can alter or impair the quality of the water. After this investigation performed during August 2018, it can be appreciated that the analysed water samples maintain appropriate levels that are suitable for the ecological status of the investigated aquatic systems, and, as expected, the aquatic habitats are ecologically balanced environments. The paper recommends the routine monitoring and periodical testing of the water quality to create and develop a database to reflect the natural variation and human-related implications for water quality within these areas, and their short, medium and long-term evolution trends. The present work is important for water quality assessment to detect changes in water quality under human pressures and climate change and to protect and conserve these natural water resources., {"references": ["Allan J. D., 1995. Stream Ecology: Structure and Functioning of Funning Waters. 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The aim of this study was to assess the existing benthic organisms of the Musura Bay and Sakhalin area, in order to evaluate the habitat status within these areas. Musura Bay and Sakhalin Area belong to the avandelta, part of the Danube Delta Biosphere Reserve (DDBR). The ecological evolution of the Musura Bay and Sakhalin Area was significantly distressed by the hydro morphological changes developed in the catchment and by the local environmental circumstances. The two investigated areas are exposed to both continental and marine impacts, been marked by rapid changes in local environmental conditions (i.e., salinity levels, water transparency, temperature, pH, dissolved oxygen concentration, wind speed etc.). At present, salinity has become an extensive threat to the structure and ecological functioning of coastal wetlands. For instance, salinity long-term monitoring showed a variation from 12 ‰ (in 1942) to 0.2 ‰ (at present) for Musura Bay, whereas for Sakhalin area the salinity is 6.9 ‰ (at present). In order to evaluate the interactions of benthic organisms and their natural environment, several analyses were performed (i.e., water quality status and the nature of the bed sediments). Results revealed that the surface water quality is generally included in good-moderate category, even if some inadvertences were encountered as a result of local environmental conditions. Based on the obtained results, the nature of the bed sediments from Musura Bay and Sakhalin area, can be included in the terrigenous (siliciclastic) rich-sediment type with values higher than 50% of the total weight of dry residue. The faunistic research highlighted the presence of 17 taxa belonging to 11 major invertebrate taxonomic groups for the Musura Bay and the presence of 46 taxa belonging to 20 groups in the Sakhalin Area. The average general density of the benthic populations in the Musura Bay was 8 times smaller than in the Sakhalin Area. This study indicated that most of the identified species seem to be extremely tolerant to temperature and salinity variations., {"references":["Anderson M.J., Gorley R.N., Clarke K.R. (2008). PERMANOVA+ for PRIMER: Guide to Software and Statistical Methods. PRIMER-E: Plymouth, UK.","ANZECC Guidelines, 2000. Australian and New Zealand Guidelines for Fresh and Marine Water Quality, On line at: http://www.mfe.govt.nz/fresh-water/tools-and-guidelines/anzecc-2000 guidelines","Băcescu M., Gomoiu M-T., Bodeanu N., Petran A., Muller G.I., Chirilă V., (1967). Marine ecology [in Romanian], Vol. II, Ed. Acad. R.S.R., Bucureşti, 7-167.","Băcescu M., Muller G., Gomoiu M-T., 1971. Ecologie Marină, Vol. IV, Ed. Acad. R.S.R., Bucureşti, 1-357.","Catianis I., Pojar I., Scrieciu A., Grosu D., Pav el A.B., (2016). 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Conference: 422-427, Vien.","www.geog.cam.ac.uk/facilities/laboratories/.../loi.doc","www.niwa.co.nz/our science/freshwater/tools/kaitiaki_tools/ impacts/dissolved-oxygen"]}

Magnetic susceptibility (MS) represents a high resolution environmental and lithological (LITHO) proxy tool, which is successfully used for the study of recent sediments in freshwater or marine aquatic environments. The studies that we have achieved in the last 40 years in the Danube – Danube Delta – Black Sea hydrosedimentary system have revealed strong connections between the characteristics of sedimentary environment, sediment quality and their magnetic properties. In the present paper are discussed results concerning several lakes from Gorgova − Uzlina Depression (Danube Delta), which are added to the lately published magneto-lithological data for sedimentary environments of Meşteru − Fortuna and Matiţa − Merhei depressions. This work, which represents the first part of a composite paper, is particularly focused on the sediment cores collected in the lakes Gorgova, Cuibeda, Uzlina and Isacova. Their MS characterization, not neglecting the lithological support, defined by the three main components, namely the SILiciclastic/ minerogenic fraction – SIL, Total Organic Matter – TOM and CARbonates – CAR, is approached. Several lithological units are identified, based upon the macroscopic characteristics, magnetic properties and lithological composition. It is interesting to note that although the study area is included in the fluvial delta plain, the recent lacustrine sediments are very thin in some sectors and the short cores (under 60 cm) stop at a level of marine clays (L. Cuibeda). The second part of this study, regarding the surficial sediments from the above-mentioned lakes, and more other ones is published inside of a similar magneto-lithogenetic context. All these data give new evidences for demonstrating the availabilities of the method used to identify the environmental influences on the magnetic susceptibility of lake sediments, and hence to assess the geoecological state of the deltaic area under attention., {"references":["Catianis, I., Rădan, S., Grosu, D. (2013) − Distribution of lithological components of recent sediments from some lakes in the Danube Delta; environmental significance, Carpath. J. Earth Environ. Sci., 8, 2, 55-68.","Catianis, I., Rădan, S., Grosu, D. (2014) − Loss of ignition as a proxy indicator for assessing the lithological composition of the recent sediments accumulated in some freshwater lakes from the Danube Delta, Romania, Inter. J. Innov. Appl. St., ISSN 2028-9324, 9, 1, 260-278.","Dean, W.E. (1974) − Determination of carbonate and organic matter in calcareous sediments and sedimentary rocks by loss on ignition: comparison with other methods, Journal of Sedimentary Petrology, 44, 242-248.","Egli, R. (2003) − Environmental influences on the magnetic properties of lake sediments, PhD Thesis, Swiss Federal Institute of Technology, Zurich, 328p. (with an Appendix). Rădan, S.-C., Rădan, S. (2007a) − A magnetic susceptibility scale for lake sediments; inferences from the Danube Delta and the Razim - Sinoie lagoonal Complex (Romania), Geo-Eco-Marina, 13, Bucureşti - Constanţa, 61-74.","Rădan, S.-C., Rădan, S. (2007b) − The magnetic signature of present environmental changes in lake sediments induced by hydrotechnical works; a case study from the Danube Delta (Romania), the XXIVth IUGG General Assemby, \"Earth: Our changing planet\", July 2 – 13, 2007, Abstracts, IAGA, Inter-Association Symposia and Workshops, published by Umbria Sci. Meet. Ass. (USMA), Perugia, Italy, December, 2007, Abstract 3104, p. 156. http://www.iugg- 2007perugia.it/iuggProc/A.pdf","Rădan, S.-C., Rădan, S. (2007c) − Modern Sediments as Enviromagnetic Archives. A Case Study: Danube Delta and Northwestern Black Sea, EOS Transactions, American Geophysical Union, 88 (52), Fall Meet. Suppl., 10 - 14 December, 2007, San Francisco, USA, Abstract GP53B-1220.","Rădan, S.-C., Rădan, S. (2010a) – The use of the magnetic susceptibility to study hydrosedimentary environments and processes in Danube Delta, Geo-Eco-Marina, 16, Bucureşti - Constanţa, 37-46.","Rădan, S.-C., Rădan, S. (2010b) – Lake sediments fingerprinting in the Danube Delta, using composite magneto-lithological signatures; an environmental approach, Travaux Géophysiques, XXXIX, Abstracts of the 12th \"Castle Meeting − New Trends in Geomagnetism. Palaeo, Rock and Environmental Magnetism\", Castle of Nové Hrady, Czech Republic, August 29 - September 4, 2010, 68-69.","Rădan, S.-C., Rădan, S. (2011) − Recent sediments as enviromagnetic archives. A brief overview, Geo-Eco-Marina, 17, Bucureşti - Constanţa, 103-122.","Rădan, S.-C., Rădan, S., Catianis, I. (2013) − The use of the magnetic susceptibility record as a proxy signature for the lithological composition of lake sediments: Evidences from Danube Delta short cores in the Meşteru − Fortuna Depression (Danube Delta), Geo- Eco-Marina, 19, Bucureşti - Constanţa, Romania, 77-105.","Rădan, S.-C., Rădan, S., Catianis, I. (2014a) − Relationship between the magnetic susceptibility and lithological composition in sediment cores from lakes of Matiţa − Merhei Depression (Danube Delta, Romania): Towards a proxy method of sedimentological and environmental fingerprinting, Geo-Eco-Marina, 20, Bucureşti - Constanţa, ISSN: 2248–2776 ISSN-L: 1224–6808, 45-86.","Rădan, S.-C., Rădan, S., Catianis, I., Scrieciu, A. (2014b) − Magnetosusceptibility and lithological fingerprints of the marine clays recovered from sediment cores taken in the Danube Delta (Romania), p. 30. In: L Török (Ed.) − \"Deltas and Wetlands\" (Book of abstracts), vol. 2, Conference \"BSB Net-Eco − Deltas and Wetlands.\"Environmental aspects and available scientific tools for Black Sea Basin protection\" (Tulcea, Romania, 15 - 17 September, 2014), Danube Delta Technological Information Center Publishing House, Tulcea, Romania, ISSN 2344-3766; DOI: 10.14592/DDI.D. W.02. 2014, 48p.","Rădan, S.-C., Rădan, S., Catianis, I., Scrieciu, A. (2014c) − Composite enviromagnetic and lithological signatures retrieved from recent sediments in the Danube Delta (Romania), with a special view to the couples of lakes, 14th Castle Meeting \"New Trends on Paleo, Rock and Environmental Magnetism\", 31st August - 6th September 2014, Évora, Portugal. https://www.fc.ul.pt/sites/default/ files/fcul/public/14Castle_meeting/Radan1_Castle%20Meeting_ Portugal_Abstract-Paper%201_Danube-Delta_Radan-etal_ Romania.pdf.","Rădan, S.-C., Rădan, S., Catianis, I., Scrieciu, A. (2014d) − Towards assessing the potential for stratigraphic studies in the Danube Delta geo-environments by using magnetosusceptibility and lithological records retrieved from Recent sediments, 127- 128, 203 (Appendix 10/Fig. A11). In: A.V. Borodin, E.A. Markova, T.V. Strukova (Eds.) − \"The Quaternary of the Urals: Global trends and Pan-European Quaternary records\", International Conference, INQUA- SEQS 2014 (Ekaterinburg, Russia, September 10 - 16, 2014), Ekaterinburg, UrFU, ISBN 978-5-321-02398-3, 228p.","Rădan, S.-C., Rădan, S., Scrieciu, A. (2015)− Environmental influences on the magnetic susceptibility of recent sediments in Danube Delta, in geoecological context: insights from lakes of Gorgova − Uzlina Depression, p. 29, In: Török L. (ed.), \"Deltas and Wetlands\" (Book of abstracts), vol. 3, Danube Delta Technological Information Center Publishing House, Tulcea, Romania, ISSN 2344-3766; DOI: 10.14592/ DDI.D.W.03.2015, 45 p.","Rădan, S.C., Rădan, S., Catianis, I., Grosu, D., Pojar I., Scrieciu, A. (2016) − An environmental magneto-lithogenetic study in the lakes of the Gorgova − Uzlina Depression (Danube Delta, Romania). II. Insights from surficial sediments, Geo-Eco-Marina, 22, Bucureşti - Constanţa (this volume).","Trodahl, M. I. (2010) − Late Holocene Sediment Deposition in Lake Wairarapa, M.Sc. Thesis, submitted to Victoria University of Wellington, New Zealand, 114p."]}

Magnetic susceptibility (MS) represents a high resolution environmental and lithological (LITHO) proxy tool, which is successfully used for the study of recent sediments in freshwater or marine aquatic environments. The studies that we have achieved in the last 40 years in the Danube – Danube Delta – Black Sea hydrosedimentary system have revealed strong connections between the characteristics of sedimentary environment, sediment quality and their magnetic properties. In the present paper are discussed results concerning several lakes from Gorgova − Uzlina Depression (Danube Delta), which are added to the lately published magneto-lithological data for sedimentary environments of Meşteru − Fortuna and Matiţa − Merhei depressions. This work, which represents the first part of a composite paper, is particularly focused on the sediment cores collected in the lakes Gorgova, Cuibeda, Uzlina and Isacova. Their MS characterization, not neglecting the lithological support, defined by the three main components, namely the SILiciclastic/ minerogenic fraction – SIL, Total Organic Matter – TOM and CARbonates – CAR, is approached. Several lithological units are identified, based upon the macroscopic characteristics, magnetic properties and lithological composition. It is interesting to note that although the study area is included in the fluvial delta plain, the recent lacustrine sediments are very thin in some sectors and the short cores (under 60 cm) stop at a level of marine clays (L. Cuibeda). The second part of this study, regarding the surficial sediments from the above-mentioned lakes, and more other ones is published inside of a similar magneto-lithogenetic context. All these data give new evidences for demonstrating the availabilities of the method used to identify the environmental influences on the magnetic susceptibility of lake sediments, and hence to assess the geoecological state of the deltaic area under attention., {"references":["Catianis, I., Rădan, S., Grosu, D. (2014) − Loss of ignition as a proxy indicator for assessing the lithological composition of the recent sediments accumulated in some freshwater lakes from the Danube Delta, Romania, Inter. J. of Innov. and Appl. St., ISSN 2028- 9324, 9, 1, 260-278.","Dean, W.E. (1974) − Determination of carbonate and organic matter in calcareous sediments and sedimentary rocks by loss on ignition: comparison with other methods, Journal of Sedimentary Petrology, 44, 242-248.","Dekkers, M.J. (1997) − Environmental magnetism: an introduction, Geol. Mijn., 76, 163-182.","Evans, M.E., Heller, F. (2003) − Environmental Magnetism. Principles and Applications of Enviromagnetics, Academic Press, Elsevier Science, USA, 299p.","Oldfield, F. (1991) − Environmental magnetism – a personal perspective, Quater. Sci. Rev., 10, 73-85.","Egli, R. (2003) − Environmental influences on the magnetic properties of lake sediments, PhD Thesis, Swiss Federal Institute of Technology, Zurich, 328p. (with an Appendix).","Ishii, Y., Kazuaki Hori, K. (2016) − Formation and infilling of oxbow lakes in the Ishikari lowland, northern Japan, Quaternary International, 397, 136-146.","Rădan, S. (2015) − Field campaign for monitoring, review and completion in the master areas from the Danube Delta, the Razim - Sinoie Lagoon Complex, and the marginal lakes, \"Phase no. 22\" Report (PN 09-41 03 04 Project), 50 p., GeoEcoMar, Bucharest, Romania (unpublished Scientific Report; in Romanian).","Rădan, S.-C. (1981) – Magnetometric and petromagnetic researches in the lacustrine area, Bul. Inf. Ştiinţ. Tehn., I, 1, Inst. Geol. Geofiz., Bucureşti, 9-11 (in Romanian).","Rădan, S.-C. (2008) – The direct problem and the inverse problem in Petromagnetology and Palaeomagnetology; a discussion, with exemplification in Geophysics, Geology and Geoecology, Geo- Eco-Marina, 14, Suppl. no. 1, Bucureşti - Constanţa, 201-215 (with 3 plates) (in Romanian).","Rădan, S.-C. Rădan, S. (2003) – Magneto-susceptibilimetric models drawn up for bottom sediments sampled in different phases from lakes of the Gorgova – Uzlina Depression, in S.C. Rădan and S. Rădan (2003) – The elaboration of an enviromagnetic method to characterize the sedimentary systems in areas covered by water. Experimentation in the Danube Delta and the Razelm (Razim) - Sinoie Lagoon Complex. Phase II (\"CERES\" Project), G.I.R. – GeoEcoMar Archives, Bucharest, Romania (unpublished Scientific Report; in Romanian).","Rădan, S.-C., Rădan, S. (2006a) – 30 years of magnetic susceptibility measurements on the Danube Delta lake sediments (Romania, 1976 - 2006). Sedimentologic applications to Environmental Magnetism, 10th Castle Meeting \"New Trends in Geomagnetism – Palaeo, Rock and Environmental Magnetism\", September 3 – 8, 2006, Castle of Valtice, Czech Republic; Abstract, Travaux Géophysiques, XXXVIII, 2006, ISSN 0231-5548, Geophysical Institute, Academy of Sciences of the Czech Republic, Prague, 94-95.","Rădan, S.-C., Rădan, S. (2006b) – A magnetic susceptibility scale with a lithological support originated in the lake sediments from the Danube Delta and the Razim – Sinoie Lagoonal Complex (Romania). An environmental and geoecological approach, 10th Castle Meeting \"New Trends in Geomagnetism – Palaeo, Rock and Environmental Magnetism\", September 3 – 8, 2006, Castle of Valtice, Czech Republic; Abstract, Travaux Géophysiques, XXXVIII, 2006, ISSN 0231-5548, Geophysical Institute, Academy of Sciences of the Czech Republic, Prague, 96-97.","Rădan, S.-C., Rădan, S. (2007a) – A magnetic susceptibility scale for lake sediments; inferences from the Danube Delta and the Razim – Sinoie Lagoonal Complex (Romania), Geo-Eco-Marina, 13, Bucureşti - Constanţa, 61-74.","Rădan, S.-C., Rădan, S. (2007b) – Modern Sediments as Enviromagnetic Archives. A Case Study: Danube Delta and Northwestern Black Sea, American Geophysical Union Fall Meeting, 10 – 14 December, 2007, San Francisco, USA (Poster Presentation); EOS Transactions, American Geophysical Union, 88 (52), Fall Meet. Suppl., San Francisco, USA, Abstract GP53B-1220.","Rădan, S.-C., Rădan, S. (2009) – Integrated magnetic susceptibility and lithological studies on lacustrine recent sediments from the Danube Delta, Geo-Eco-Marina, 15, Bucureşti - Constanţa, 177-197.","Rădan, S.-C., Rădan, S. (2010a) – The use of the magnetic susceptibility to study hydrosedimentary environments and processes in Danube Delta, Geo-Eco-Marina, 16, Bucureşti - Constanţa, 37-46.","Rădan, S.-C., Rădan, S. (2010b) – Lake sediments fingerprinting in the Danube Delta, using composite magneto-lithological signatures; an environmental approach, Travaux Géophysiques, XXXIX, Abstracts of the \"12th Castle Meeting − New Trends in Geomagnetism. Palaeo, Rock and Environmental Magnetism\", Castle of Nové Hrady, Czech Republic, August 29 - September 4, 2010, 68-69.","Rădan, S.-C., Rădan, S. (2011) – Recent sediments as enviromagnetic archives. A brief overview, Geo-Eco-Marina, 17, Bucureşti-Constanţa, 103-122 (with a double plate).","Rădan, S.-C., Rădan, M., Rădan, S. (1978) – Magnetic susceptibility of bottom sediments. In: N. Mihăilescu et al. (1978) – The geological and geophysical study of the Danube Delta to assess its economical potential (Goloviţa L. – Sinoe L. sector), Archives of Institute of Geology and Geophysics (in present, Geological Institute of Romania), Bucharest, Romania (unpublished Scientific Report; in Romanian).","Rădan, S.C., Rădan, M., Rădan, S. (1980) − Petromagnetic characteristics of the bottom sediments. In: Mihăilescu, N. et al. (1980) – The geological and geophysical study of the Danube Delta in order to evaluate its economical potential (Gorgova – Uzlina – Isacova sector), Archives of Institute of Geology and Geophysics (in present, Geological Institute of Romania), Bucharest, Romania (unpublished Scientific Report; in Romanian).","Rădan, S.-C., Rădan, S., Catianis, I. (2013) − The use of the magnetic susceptibility record as a proxy signature for the lithological composition of lake sediments: Evidences from Danube Delta short cores in the Meşteru − Fortuna Depression (Danube Delta), Geo- Eco-Marina, 19, Bucureşti - Constanţa, Romania, 77-105.","Rădan, S.-C., Rădan, S., Catianis, I. (2014) − Relationship between the magnetic susceptibility and lithological composition in sediment cores from lakes of Matiţa − Merhei Depression (Danube Delta, Romania): Towards a proxy method of sedimentological and environmental fingerprinting, Geo-Eco-Marina, 20, Bucureşti - Constanţa, ISSN: 2248–2776 ISSN-L: 1224–6808, 45-86.","Rădan, S.-C., Rădan, S., Catianis, I., Grosu, D., Scrieciu, A., Pojar, I. (2016) − An environmental magneto-lithogenetic study in the lakes of the Gorgova – Uzlina Depression (Danube Delta, Romania). I. Insights from short sediment cores, Geo-Eco-Marina, 22, Bucureşti - Constanţa, ISSN: 2248–2776 ISSN-L: 1224–6808 (this volume).","Rădan, S.-C., Rădan, S., Scrieciu, A. (2015) − Environmental influences on the magnetic susceptibility of recent sediments in Danube Delta, in geoecological context: insights from lakes of Gorgova − Uzlina Depression, Abstract, p. 29, in L. Török (ed.) − 2015 Deltas and Wetlands (Book of abstracts), vol. 3, 45 p., Danube Delta Technological Information Center Publishing House, Tulcea, Romania, ISSN 2344-3766.DOI:10.14592/DDI.D.W.03.2015","Thompson, R., Battarbee, R.W., O'Sullivan, P.E., Oldfield, F. (1975) − Magnetic susceptibility of lake sediments, Limnol. Oceanogr., 20, 5, 687-698.","Verosub, K.L., Roberts, A.P. (1995) − Environmental magnetism: Past, present, future, J.Geophys. Res., 100, 82, 2175-2192."]}

In the framework of the Danube Delta geosystem spatial evolution study, new results achieved for sediment cores − this time collected from the Matiţa − Merhei Depression lakes − are added up to the data which were previously published with regard to the Meşteru − Fortuna Depression. Actually, it is the second part of the series of papers dedicated to the magneto − lithological investigation of sediment columns, taken out from various aquatic environments, in both the Fluvial and Marine Delta Plains. Vertical profiles of magnetic susceptibility (MS) and contents of siliciclastic/minerogenic/detrital fraction (SIL), total organic matter (TOM) and carbonate (CAR) are carried out for 9 cores (not longer than 55.5 cm), collected from four lakes (Babina, Matiţa, Polideanca and Bogdaproste), a swamp (Polideanca − Lopatna) and a canal (Lopatna − Polideanca). These records are based on MS (k) measurements (with a Kappabridge KLY-2), and respectively, on lithological component contents analyses (by the “Loss on Ignition”/LOI method), performed on sediment samples obtained by core slicing, at 1-3 cm intervals. MS, SIL, TOM and CAR maps are carried out for surficial sediments, as well, in order to describe the magneto-lithological background which characterizes each of the lakes from where the short sediment cores were extracted. The MS calibration of the lake sediments (core and grab samples) is carried out by using a k scale with 5 classes. The correlation coefficient (r) is calculated for all 6 possible pairs of above specified parameters (SIL vs. k, TOM vs. k, CAR vs. k, SIL vs. TOM, SIL vs. CAR and TOM vs. CAR). To evaluate the correlation size, a scale with 6 steps is used. Positive/direct and negative/reversed correlations have always been obtained for SIL vs. k, and TOM vs. k, respectively. Therefore, new proofs are added to assign the magnetic parameter proxy quality as environmental and sedimentological fingerprinting tool. Another important result of the present study is the detection of some marine clays located very close below the water/sediment interface, intercepted, particularly, at the lower/basal part of two cores from the Babina Lake, two from Matiţa Lake, and another one from the Lopatna − Polideanca Canal. These marine deposits (with macroscopically identified specific fauna) are characterized by clearly different magnetic and lithological signatures (high MS values and SIL contents, low TOM contents), as compared with the fingerprints recovered from the overlying muds (sampled at the upper part of the cores). The presence of a marine episode revealed by some of the sediment cores collected from lakes of the Matiţa − Merhei Depression, which is a part of the Fluvial Delta Plain, is very interesting and can represent a contribution to the better knowledge of the deltaic system temporal and spatial evolution.

The paper analyses the enviromagnetic results obtained on short cores collected from Danube Delta lakes and channels. A Hydro-Bios type core sampler was used to investigate sediments up to ca. 60 - 80 cm depth from various sedimentary environments located both in the Fluvial Delta Plain (e.g., Lungu L., Cuteţchi L., Fortuna L., Crânjală Canal, Băclăneşti L., Matiţa L., Babina L., Bogdaproste L., Gorgova L., Uzlina L., Isacova L.) and the Fluvio-Marine Delta Plain (e.g., Puiu L. and Roşu L.). In this article, the results achieved for the sediment cores taken in the Meşteru - Fortuna Depression, during the 2010 - 2013 interval, are presented. The data make possible to compare, in some cases, the magnetic susceptibility (k; MS) characterisation of the bottom sediments (sampled with the grab sampler) with the MS data associated with the first 10-30 cm of sediments collected from the upper half of the cores, taken out from the same places within a lake. More interesting are the variations in the magnetic susceptibility regime along the cores. In many cases, the enviromagnetic parameter “intensity” increased from the upper part towards the core base, but also some well-defined maximum and minimum k anomalies were detected. A clearly higher MS regime was identified along the whole short cores collected from the Crânjală mid-channel. The data demonstrate the capability of the MS parameter as a sedimentogenetic indicator, being possible to correlate the higher k values with the interception of a silted up zone or of two different sediment sequences within a core as a result of the hydrological regime changes occurred during the time. As regards the lower k values measured at the upper part of the cores, they are usually related to the muds rich in fine vegetal (organic) detritus and/or rich in shell fragments. Based on the values of the enviromagnetic parameter (k) and of the contents of the lithological components along the cores, several correlation coefficients (r) were calculated, taking into consideration all the possible pairs of magnetic and/or lithological parameters. The vertical distribution of the magnetic susceptibility associated with the cores clearly illustrates the particular characteristics of the “confined sedimentary environments” versus the “dynamic sedimentary environments”.