Sonja Lojen

Total mercury, methylmercury and selenium in mercury polluted areas in the province Guizhou, China

The province of Guizhou in Southwestern China is currently one of the worlds most important mercury production areas. Emissions of mercury from the province to the global atmosphere have been estimated to be approximately 12% of the world total anthropogenic emissions. The main objective of this study was to assess the level of contamination with Hg in two geographical areas of Guizhou province. Mercury pollution in the areas concerned originates from mercury mining and ore processing in the area of Wanshan, while in the area of Quingzhen mercury pollution originates from the chemical industry discharging Hg through wastewaters and emissions to the atmosphere due to coal burning for electricity production. The results of this study confirmed high contamination with Hg in soil, sediments and rice in the Hg mining area in Wanshan. High levels of Hg in soil and rice were also found in the vicinity of the chemical plant in Quingzhen. The concentrations of Hg decreased with distance from the main sources of pollution considerably. The general conclusion is that Hg contamination in Wanshan is geographically more widespread, due to deposition and scavenging of Hg from contaminated air and deposition on land. In Quingzhen Hg contamination of soil is very high close to the chemical plant but the levels reach background concentrations at a distance of several km. Even though the major source of Hg in both areas is inorganic Hg, it was observed that active transformation of inorganic Hg to organic Hg species (MeHg) takes place in water, sediments and soils. The concentration of Hg in rice grains can reach up to 569 microg/kg of total Hg of which 145 microg/kg was in MeHg form. The percentage of Hg as MeHg varied from 5 to 83%. The concentrations of selenium can reach up to 16 mg/kg in soil and up to 1 mg/g in rice. A correlation exists between the concentration of Se in soil and rice, indicating that a portion of Se is bioavailable to plants. No correlation between Hg and Se in rice was found. Exposure of the local population to Hg may occur due to inhalation of Hg present in air (in particular in Hg mining area) and consumption of Hg contaminated food (in particular rice and fish) and water. Comparison of intake through these different routes showed that the values of Hg considerably exceed the USA EPA Reference Concentration (RfC) for chronic Hg exposure (RfC is 0.0004 mg/m(3)) close to the emission sources. Intake of Hg through food consumption, particularly rice and fish, is also an important route of Hg exposure in study area. In general, it can be concluded that the population mostly at risk is located in the vicinity of smelting facilities, mining activities and close to the waste disposal sites in the wider area of Wanshan. In order to assess the real level of contamination in the local population, it is recommended that biomonitoring should be performed, including Hg and MeHg measurements in hair, blood and urine samples.

Effects of fish farm loading on sea grass Posidonia oceanica at Vrgada Island (Central Adriatic): a nitrogen stable isotope study

Analyses of nitrogen stable isotopes in the marine sea grass Posidonia oceanica were used to investigate the influence of fish farming on the coastal ecosystem of Vrgada Island in the Murter Sea, Central Adriatic. The results show a statistically significant 15N enrichment (up to 4.7‰ at p < 0.005) in P. oceanica leaf and shoot tissues from fish cage sites with respect to the unaffected offshore reference site of Lumbarda Reef Flat (Kornati Islands). Heavy nitrogen enrichment was also detected in other benthic organisms analysed during this study and is attributed to the absorption and assimilation of 15N-enriched fish farm derived nitrogen waste.

Can δ15N in lettuce tissues reveal the use of synthetic nitrogen fertiliser in organic production

BACKGROUND The nitrogen isotopic fingerprint (δ(15)N) is reported to be a promising indicator for differentiating between organically and conventionally grown vegetables. However, the effect on plant δ(15)N of split nitrogen fertilisation, which could enable farmers to cover up the use of synthetic fertiliser, is not well studied. In this study the use of δ(15)N in lettuce as a potential marker for identifying the use of synthetic nitrogen fertiliser was tested on pot-grown lettuce (Lactuca sativa L.) treated with synthetic and organic nitrogen fertilisers (single or split application). The effect of combined usage of synthetic and organic fertilisers on δ(15)N was also investigated. RESULTS The δ(15)N values of whole plants treated with different fertilisers differed significantly when the fertiliser was applied in a single treatment. However, additional fertilisation (with isotopically the same or different fertiliser) did not cause a significant alteration of plant δ(15)N. CONCLUSION The findings of the study suggest that the δ(15)N value of lettuce tissues could be used as a rough marker to reveal the history of nitrogen fertilisation, but only in the case of single fertiliser application. However, if the difference in δ(15)N between the applied synthetic and organic nitrogen fertilisers was > 9.1 ‰, the detection of split and combined usage of the fertilisers would have greater discriminatory power.

Decomposition of sedimentary organic matter and methane / formation in the recent sediment of Lake Bled Slovenia

Decomposition of sedimentary organic matter and methane formation in a eutrophic dimictic subalpine lake Lake Bled, . . NW Slovenia were investigated by measurement of in situ concentrations of dissolved inorganic carbon DIC in the pore water and its stable carbon isotopic composition, as well as by incubation experiments. The isotopic composition of carbon in the methane produced during incubation experiments was also studied. The ratio between methane produced by acetate fermentation and CO rH reduction was estimated from d 13 C-DIC vs. DIC concentration profiles in sediment pore water 22 w using a mathematical model developed by LaZerte LaZerte, 1981. The relationship between dissolved carbon dioxide and x its stable isotope ratio in aquatic sediments. Geochim. Cosmochim. Acta 45, 647-656 . It was found that in the spring acetate fermentation is dominant when about 65% of methane is produced by this reaction pathway, whereas in the autumn, over 90% of the methane results from CO reduction. d 13 C of methane released during a 6-week incubation experiment with 2

Nitrogen isotopic signature of vegetables from the Slovenian market and its suitability as an indicator of organic production

The aim of this study was to obtain preliminary data on δ15N values in organically and conventionally grown vegetables available on the Slovenian market to determine whether there are any characteristic differences in δ15N values, which could be used as a marker to differentiate between organically and conventionally grown vegetables, namely vegetables grown with synthetic or organic nitrogen fertilisers. Therefore, 14 different varieties of organically and conventionally grown vegetables were analysed. The results obtained show clear differences in mean δ15N values between organically and conventionally grown vegetables (up to 6.3\permil). However, due to overlapping results, it was not possible to differentiate between organically and conventionally grown counterparts in eight vegetable varieties, despite the differences in mean δ15N values. The results obtained indicate that the method has several limitations. Hence, δ15N could be a reliable indicator for organic production, but nevertheless, the conclusion has to be validated by background information.

Recent Sediments of Makirina Cove (Northern Dalmatia, Croatia): Their Origin Viewed Through a Multidisciplinary Approach

Makirina Cove was formed by the Holocene sea-level rise which caused a marine ingression into the depression formed within Albian– Cenomanian dolomites at approximately 4.5 ka B.P. At present, Makirina Cove represents an restricted, stressed, shallow-marine (<2 m) ecosystem characterized by varying seawater temperatures (0–35°C) as well as fluctuating salinities (up to 41‰) affected by seasonally enhanced evaporation, continuous freshwater supply through on-shore and submarine springs associated with the coastal karst area and surface run-off episodes. These environmental conditions have been conducive to high primary production of organic matter resulting in the formation of organic-rich deposits which contain up to 5 wt.% of organic carbon. Up to the present times, 3.5 m of sediments have been deposited indicating a relatively high sedimentation rate estimated at 0.75 m/1.0 ka in the northern central part of the Cove. The sediments are being deposited mostly as poorly sorted clayey–sandy silts. The distribution and concentration of most of the chemical elements is dependant on the mineralogical composition and granulometric features of the Makirina sediments, which show values more or less similar to those from the Central Adriatic. Accordingly, there is a positive correlation with Al and K concentrations increasing off-shore and with the depth being associated with increasing concentrations of clay minerals within the clay fraction. The same holds true for concentrations of some trace elements, especially Mo and Se which is consistent with the distribution pattern of sulphides. Selenium is preferentially enriched in authigenic pyrite and it is probably the major source of Se in the Makirina Cove sediments. The concentrations of Ca, Mg and Sr decrease off-shore and they are linked to the composition of the surrounding carbonate rocks. The saturation indices show that the water is supersaturated with respect to carbonates enabling the precipitation of authigenic amorphous or crystalline carbonate phases from the pore water in the upper segment of the sediment column. According to the oxygen isotopic (δ18O) composition, molluscs precipitated their carbonate shells mostly during warmer periods (May to November) at or near isotopic equilibrium with their ambient waters. The carbon isotopic δ13C composition of mollusc carbonate shells is environmentally affected due to oxidation and decomposition of organic matter as well as influxes of fresh water into the Cove, indicating their formation out of the predicted isotopic equilibrium with atmospheric CO2. Palynological and organic carbon isotopic (δ13C) composition shows that the sedimentary organic matter (SOM) is 70–90% lipid- and hydrogen-rich and on average 2/3 marine derived (mainly phytoplankton, bacteria and marine macrophytes) and 1/3 terrestrially derived (mainly woody tissue). The variations in composition of SOM have been noted as a function of the distance from the shore. The type and the preservation state of SOM and pyrite as well as the measurements of Eh, pH, total alkalinity, dissolved inorganic carbon (DIC) and the enrichment of redox-sensitive trace elements, indicate oxygen-depleted depositional conditions and that the sediment is highly reductive even in the uppermost segment at the sediment/water interface. According to the results obtained from the applied methods, the features of Makirina sediments strongly reflect the given depositional conditions within this restricted, stressed, shallow- marine environment where these organic-rich sediments originate, and may therefore serve as a calibration standard in further investigations

Stable Isotope Event Markers Near the Permo-Triassic Boundary in the Karavanke Mountains (Slovenia)

Permo-Triassic (P/Tr) boundary events, which took place approximately 250 Ma ago, led to the most extensive mass extinction in the history of life. A number of possible explanations for this profound break in the evolution of life have been proposed, such as volcanic activity, sea-level fluctuation, changes in sea-water chemistry, an extra-terrestrial impact event and various related factors (YOICHI, 1994). The most recently proposed cause of the mass extinction at the end of the Permian is a combination of these more or less co-occurring events operating in three phases (ERVIN, 1996). The first began with the marine regression during the Late Permian and resulted in the destruction of many marine basins, reduction in the habitat area of many organisms and increased climatic instability. The second phase involved the eruption of the Siberian Traps and further environmental degradation. The final phase may have started immediately prior to the boundary when the Late Permian regression ended and the earliest Triassic transgression begun. The global events outlined above coincide with isotope and elemental anomalies recorded in several P/ Tr boundary sections all

Seasonal differences of stable isotope composition and lipid content in four bivalve species from the Adriatic Sea

Abstract The feeding ecology of four bivalve species co-occurring in the Mali Ston Bay, the most important bivalve aquaculture area of the Eastern Adriatic, were investigated by analysing the stable isotope composition and lipid content in two tissue types. Analyses included two cultured species: Mytilus galloprovincialis and Ostrea edulis, and two naturally occurring species: Modiolus barbatus and Arca noae. Total lipid concentrations were higher in the digestive gland than in the adductor muscle in all species studied. The study confirmed seasonal variability of stable isotope signatures. Observed seasonal changes were more pronounced in the digestive gland than in the adductor muscle, suggesting that the former better reflects seasonal trophic patterns. The results obtained indicate isotopic niche overlap in the investigated species with the highest degree of overlap (~60%) among two cultured species during the spring–summer period, and between two naturally occurring species during the autumn–winter period (~60%). A lower degree of overlap between other species might suggest utilization of different additional food sources during certain times of the year. This study contributes to our understanding of trophic interactions between different bivalve species and is important for future modelling of food webs and sustainable management of wild and cultured populations.

Use of Stable Nitrogen Isotope Signatures of Anthropogenic Organic Matter in the Coastal Environment: The Case Study of the Kosirina Bay (Murter Island, Croatia)

In this study stable nitrogen isotope ratios of particulate matter POM, zooplankton and selected biota such as Mytilus galloprovincialis were used to assess the impact of anthropogenically derived organic matter from the untreated domestic sewage, municipal and industrial effluents on the coastal ecosystem of the Kosirina Bay (Murter Island). The differences in δ15N values observed in POM and organisms collected in Kosirina Bay as compared to POM and biota sampled at unaffected sites from the southern part of the Kornati Island and highly impacted Pirovac Bay revealed only a very minor effects of anthropogenic inputs of nutrients and organic matter which is most probably derived from a sewage outfall south of the Tužbina Island.

Use of stable isotope composition variability of particulate organic matter to assess the anthropogenic organic matter in coastal environment (Istra Peninsula, Northern Adriatic)

Nitrogen and carbon stable isotope analysis of particulate organic matter (POM) was used to assess the impact of anthropogenically derived organic matter in coastal parts of the Istra Peninsula (Northern Adriatic). The investigation was conducted in areas potentially impacted and enriched with different amounts of organic matter. Elevated δ15N values in POM reflect enrichment of organic matter near the coast due to inadequate municipal infrastructure in cities and local septic systems as well as inputs from riverine terrestrial material. On the contrary, negative δ15N values reflect the depleting effect of purification plants. Significant differences in nitrogen stable isotope ratios were observed between western and southeastern coasts. The δ13C values show small depletion at sites with potentially greater anthropogenic impact. A weak temporal increase of δ15N from spring to late summer was observed. The results for nitrogen and carbon isotope ratios of POM and their comparisons with other areas suggest diverse amounts and sources of organic matter as well as differences in movement of floating POM within the water column. The δ15N and δ13C values reflect the ratios of marine and terrigenous organic matter, the latter being mainly anthropogenically influenced. The results finally suggest precaution in applicability of POM as tracers for detecting anthropogenic organic matter in marine coastal ecosystem.