Iron (Fe) is an essential micronutrient for phytoplankton growth, and its availability limits primary production in half of the global ocean. Traditionally, atmospheric input of natural mineral dust has been considered as a main source of Fe in the surface ocean. However, here we show that about 45% of the water-soluble Fe in aerosols collected over the East Sea (Japan Sea) is anthropogenic, which originates mainly from heavy fuel oil combustion, based on the analyses of various chemical tracers (Al, K, V, Ni, Pb, and 210Pb). It is striking that a tiny quantity of oil, less than 1% of the aerosols in mass, can constitute the majority of water-soluble Fe in aerosols due to its high Fe solubility. Furthermore, we show that a quarter of dissolved Fe in the East Sea is anthropogenic using a 210Pb-based scavenging model. Since this sea is almost fully enclosed (200-3000 m) and located at the forefront of the Asian human footprint, our results provide an insight that the marine Fe cycle may be already perturbed by human activities.

The presented study was aimed at assessing the ability to accumulate and retain 210Po and 210Pb in two species of the mosses Sphagnum girgensohnii Russow and Pleurozium schreberi (Willd. ex Brid.) Mitt. Mosses were collected in the zone of influence of the former radium-extracting plants (Komi Republic, Russia). 210Po and 210Pb activity concentrations in S. girgensohnii varied from 131 ± 15.4 to 221 ± 18.3 Bq kg-1, and from 164 ± 18.6 to 309 ± 26.1 Bq kg-1 respectively. In P. schreberi corresponding activity concentrations ranged from 107 ± 18.8 to 328 ± 29.2 Bq kg-1 and from 117 ± 13.2 to 399 ± 31.1 Bq kg-1. Activity concentrations of 210Po and 210Pb in autumn were higher than in summer. In the young parts of the mosses, they were lower than in the old parts. To assess the ability to retain accumulated radionuclides, watersoluble (distilled H2O), exchangeable (1 M CH3COONH4), and acidsoluble (0.1 M H2SO4) fractions of 210Po and 210Pb were isolated from the studied mosses by the method sequential extraction. It was revealed that these fractions in total contained up to 26% of 210Po and 39% of 210Pb. The results showed that the studied moss species are a good biogeochemical barrier and long-term storage for 210Pb and 210Po.

Radioactivity levels of 210Pb and 226Ra were detected in a sediment core obtained using a multi-corer from the polymetallic nodule area inside the Clarion-Clipperton Zone (CCZ), a contract area of the China Ocean Mineral Resources Association (COMR) in the eastern Pacific Ocean. The profile of excess 210Pb (210Pbex) shows that the specific activity of 210Pbex has three parts with different distributions at depths of 0-16 cm (I), 17-36 cm (II), and 37-48 cm (III). When the I section of nonlocal mixing was excluded, using a steady-state diffusion mode, the bioturbation coefficients of the core were estimated to be 24.2 cm2/a at 17-36 cm deep and 5.9 cm2/a at 37-48 cm deep, which were greater compared to previously published results. This is most likely owing to bioturbations caused by various organism species in the two sections.

We investigated the partitioning of 7Be, 10Be, and 210Pb aerosols between operationally dissolved and >0.5 μm particulate fractions in wet and dry atmospheric deposition. Bulk deposition in situ-log(KD) averaged 4.27 ± 0.46 for 7Be and 4.79 ± 0.59 for 210Pb (±SD, n = 163), with corresponding activity-fractions particulate (fP) = 24 and 48%. KD was inversely correlated with particulate mass concentration (pC), a particle concentration effect (p.c.e.) that indicates that dissolved 7Be and 210Pb are bound to submicron colloids. Experimental desorption-KD was higher than in situ by a factor of 20 for 7Be and 4 for 210Pb (n = 27), indicating that FRN sorption to particulates was irreversible. 7Be:10Be ratios confirmed that colloidal and particulate fractions were geochemically distinct, with corresponding ages of 120 ± 30 and 260 ± 45 days, respectively [mean ± SE, n = 9, p = 0.011]. Fractions particulate fBe7, fBe10, and fPb210 each increased with 7Be:10Be bulk age, a particle-age effect (p.a.e). In multiple regression, fBe7 was best predicted by N, Mn, Al, and Ni [R2 = 0.75, p < 0.0001], whereas fPb relied on N, S, Fe, and Mn [R2 = 0.69, p < 0.0001]. Despite differences in magnitude and controls on partitioning, the ratio fBe:fPb converged to 1 with pC in the range of 10-100 mg L-1. Given sufficient solid surfaces, irreversible sorption and p.a.e. form a basis for 7Be:210Pb chronometry of aerosol biogeochemical cycling.

The introduction and establishment of exotic species often result in significant changes in recipient communities and their associated ecosystem services. However, usually the magnitude and direction of the changes are difficult to quantify because there is no pre-introduction data. Specifically, little is known about the effect of marine exotic macrophytes on organic carbon sequestration and storage. Here, we combine dating sediment cores (210 Pb) with sediment eDNA fingerprinting to reconstruct the chronology of pre- and post-arrival of the Red Sea seagrass Halophila stipulacea spreading into the Eastern Mediterranean native seagrass meadows. We then compare sediment organic carbon storage and burial rates before and after the arrival of H. stipulacea and between exotic (H. stipulacea) and native (C. nodosa and P. oceanica) meadows since the time of arrival following a Before-After-Control-Impact (BACI) approach. This analysis revealed that H. stipulacea arrived at the areas of study in Limassol (Cyprus) and West Crete (Greece) in the 1930s and 1970s, respectively. Average sediment organic carbon after the arrival of H. stipulacea to the sites increased in the exotic meadows twofold, from 8.4 ± 2.5 g Corg  m-2  year-1 to 14.7 ± 3.6 g Corg  m-2  year-1 , and, since then, burial rates in the exotic seagrass meadows were higher than in native ones of Cymodocea nodosa and Posidonia oceanica. Carbon isotopic data indicated a 50% increase of the seagrass contribution to the total sediment Corg pool since the arrival of H. stipulacea. Our results demonstrate that the invasion of H. stipulacea may play an important role in maintaining the blue carbon sink capacity in the future warmer Mediterranean Sea, by developing new carbon sinks in bare sediments and colonizing areas previously occupied by the colder thermal affinity P. oceanica.

In this study, the activity concentrations levels of 210Pb and 210Po in the edible portions of eight seafood samples collected from the Fujian coast of China were determined. The activity concentrations ranged from 0.74 ± 0.08 to 12.6 ± 1.0 Bq/kg for 210Po and from the minimum detectable limit (MDL, 0.80 Bq/kg) to 11. 7 ± 1.1 Bq/kg for 210Pb. The 210Po activity concentration in all the fish organs ranged from 0.68 to 204 Bq/kg (w.w.), and the 210Po activity was mainly concentrated in the stomach, spleen, heart, liver, gonad, and intestine samples. The 210Pb activity concentration in all the fish organs ranged from the MDL to 15.2 Bq/kg (w.w.), and the 210Pb activity was concentrated in the head, fish scale, and gill samples. The annual effective ingestion doses ranged from 82.8 to 255 μSv/a for all age groups, and the lifetime risk of cancers were estimated. Both the effective ingestion doses and cancer risk to humans were within the acceptable ranges.

The assessment of environmental radioactivity much relies on radionuclide content in soil. This stems from the significant contribution of soil to both external and internal exposure to ionising radiation via direct emission of gamma radiation and soil-to-plant radionuclide transfer, respectively. This motivated us to carry out a systematic research on the radioactivity of soil in Croatia to obtain relevant data that can be used as a basis for understanding the related effects of geomorphological, biogeographical, and climatological properties of the environment. We collected samples of the surface layer of uncultivated soil (0-10 cm) at 138 sites from all over the country and measured them for radionuclide activity concentrations by means of high-resolution gamma-ray spectrometry. This resulted in radioactivity maps containing data on activity concentrations of representative radionuclides in the environment. In this paper, which is the first in our two-part presentation, we focus on the naturally occurring 232Th and 238U decay chains and their correlations with the diversity of Croatian regions. For both of the chains, activity concentrations were the highest in the Dinaric region, the lowest in the Pannonian region, and intermediate in the Adriatic region. Relatively high concentrations of 226Ra in the soil of the Dinaric region implied a possibility of an enhanced emanation of its progeny 222Rn into the air. Activity concentrations of 210Pb were additionally elevated in areas with dense vegetation, most probably due to an atmospheric deposition of airborne 210Pb onto the surface of plants and their eventual decomposition on the ground.
U radioaktivnosti okoliša velika se pažnja posvećuje radionuklidima u tlu. Taj interes slijedi iz značajnih doprinosa tla i vanjske i unutarnje izloženosti ionizirajućem zračenju izravnom emisijom gama-zračenja i transferom radionuklida iz tla u biljke. To nas je motiviralo da provedemo sustavno istraživanje radioaktivnosti tla u Hrvatskoj kako bismo dobili relevantne podatke kao osnovu za razumijevanje pripadnih učinaka geomorfoloških, biogeografskih i klimatoloških svojstava okoliša. Prikupili smo uzorke površinskoga sloja (0–10 cm) nekultiviranoga tla s 138 lokacija diljem zemlje te smo mjerili koncentracije aktivnosti u njima koristeći se visokorezolucijskom gamaspektrometrijom. To je rezultiralo mapama radioaktivnosti hrvatskoga tla, koje sadržavaju podatke o koncentracijama aktivnosti reprezentativnih radionuklida u okolišu. U ovom radu, koji je prvi u našoj dvodijelnoj prezentaciji, fokusirali smo se na prirodnopojavne 232Th i 238U lance raspada i njihove korelacije s raznolikošću hrvatskih regija. Za oba su lanca koncentracije aktivnosti bile najviše u dinarskom području, najniže u panonskom području i srednje u jadranskom području. Posebice, relativno visoke koncentracije 226Ra u tlu dinarskoga područja impliciraju mogućnost povišene emanacije njegova potomka 222Rn u zrak. Koncentracije aktivnosti 210Pb bile su dodatno povišene u područjima s gustom vegetacijom, vrlo vjerojatno zbog atmosferske depozicije iz zraka na biljke te na njihovu konačnu dekompoziciju na tlu.

Naturally occurring 210Pb and artificial 137Cs fallouts are widely used as radioactive tracers for the determination of water-induced soil erosion for different time scales equal to 50 and 100 years, respectively. There exist several calibration models useful to convert the variation of the inventory of these radiotracers in cultivated soil compared to its value on non-disturbed soil to a soil erosion rate. The most comprehensive calibration models are based on a mass balance approach. In the present work, a new calibration model is proposed. It consists on the generalization of the mass balance approach to a cultivated soil subject to two successive and continuous periods of cultivation. The proposed model combines 210Pb and 137Cs fallouts for the same time scale by relaxing the constraint on 210Pb fallout from being used for 100 years\' time scale. The model was applied successfully to hypothetical cases and can be used to measure soil erosion rates for practical cases. It is important to note that the proposed model has two main advantages. First, the complementarity between 210Pb and 137Cs fallouts is for the same time scale and not for different time scales, as usually considered and believed in this field. Second, 210Pb fallout is used for time scales less than 100 years. This makes the model useful to estimate soil erosion rates for two successive periods of cultivation. To the best knowledge of the authors, the combination of 210Pb and 137Cs fallouts for the determination of soil erosion rate variation due to change in cultivation practices for the same time scale has never been developed or applied in the past.

This is a study of the atmospheric-origin natural radionuclides (7Be and 210Pb) and a wide range of micro- and macro-element accumulation in mosses, lichens, cedar and larch needles in Arctic western Siberia (Yamal-Nenets Autonomous District). Based on the specific activities measurements of atmospheric precipitation markers (7Be and 210Pb), this study found that the concentration of dust particles in the studied objects incrementally increases in the following order, from lowest concentration to highest: cedar needles, larch needles, lichens and mosses. Concentrations of Zr, Hf, Ti, Th, Fe, V, Li, Na, Si, Be, Y, rare earth elements (REE) and Sc in this area also increase in the same ascending sequence. Enrichment factors of these elements (EF) relative to the North American Shale Composite (NASC) are close to unity, which proves their terrigenous origin. Also, the terrigenous origin of the elements in the studied biological objects is confirmed by their high correlation coefficients with Sc. This means that their concentration in the studied biological objects is the result of a background of solid atmospheric precipitation. Enrichment factors of biogenic elements and their analogues (P, Se, Mn, Mg, Ca, K, Zn, Sr, Ba, Rb, Cs) are significantly greater than unity, and this is associated with high concentrations of these elements in the biological part of the samples. A radially symmetric distribution of Pb content in biological objects is observed over the surface of the studied area (with a center located within the city of Novy Urengoy). This leads to the conclusion that there is a point source around which anthropogenic precipitation of Pb takes place. This distribution is most clearly manifested by the example of larch and cedar needles. Anthropogenic deposition of other elements has not been detected in this study area.

The activity concentrations of natural radionuclides (210Po and 210Pb) and residual pesticide levels were determined from the fish (red mullet, common sole, anchovy, horse mackerel, gray mullet, and sardine) and mussel samples collected in İzmir Bay seasonally from October 2012 and July 2013. The 210Po and 210Pb concentrations varied between 5.7 ± 4.0 Bq kg-1 dry weight (dw) to 353.7 ± 45.0 Bq kg-1(dw) and 0.7 ± 0.2 Bq kg-1 (dw) to 4.3 ± 0.8 Bq kg-1 (dw), respectively. From a public health point of view, the fish and mussel collected from the İzmir Bay are not harmful to consumers.