Accumulation rate and sources of plastic marine litter at nesting grounds of green turtles on the North Island of Qilianyu, Xisha Islands, South China Sea

In this study, the accumulation rate of plastic litter was investigated by sampling quadrats placed on the North Island of Qilianyu, and the composition was analyzed and identified to determine its source. The results showed that the annual average accumulation rate of plastic litter on North Island was 0.64 ± 0.32 pieces·m-2·month-1, with a mass accumulation rate of 11.30 ± 7.73 g·m-2·month-1. The accumulation rate of plastic litter was mainly influenced by wind speed and direction, with higher accumulation rates occurring during the southwest monsoon season and tropical cyclones. ATR-FTIR analysis indicated that polyethylene (44 %) and polypropylene (41 %) were the most abundant types of polymers. This study reveals the current status of plastic litter pollution in green turtle nesting grounds on North Island in Qilianyu, which can be used as a reference for management strategies that mitigate plastic litter pollution.

Representation of investigation results of microplastics on sandy beaches-accumulation rate and abundance in the entire study site

Long-term microplastics (MPs) environmental pollution trends cannot be understood only by investigating their presence on beaches. Without estimating MPs for the entire beach, comparisons between multiple beaches cannot be made. In this study, Nagasaki Prefecture was selected as the study site, we measured MPs accumulation rate to express the MPs pollution trend and weighted the measurement results to enable comparison of MPs content among multiple sandy beaches. The MPs accumulation rate in the study site was measured by periodic investigation at fixed spots. The average in the supratidal zone was 1.5 ± 0.9 mg-MPs/(m2-sand⋅ d) (n = 15). The weighting of the MPs content in hot spots and non-hot spots by their respective areas enabled us to obtain the representative value and the dispersion of the MPs content in the entire study site. The MPs contents in the three beaches were 298 ± 144, 1,115 ± 518, and 4,084 ± 2,243 mg-MPs/(m2-sand), respectively. Using these values, it is possible to compare the MPs contents of multiple beaches.

Spatial distribution, source identification and flux estimation of polycyclic aromatic hydrocarbons and organochlorine pesticides in basins of the Eastern Indian Ocean

Although polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) have been recorded worldwide, information on their presence in the Eastern Indian Ocean (EIO), especially south of 10°S, remains limited. We investigated the distribution and depositional fluxes of PAHs and OCPs, and the major sources and ecological risks of PAHs in EIO surface sediments from the Central Indian Ocean (CIOB) and Wharton Basin (WB). The concentration of Σ18 PAHs and ∑10 OCPs had an average value (± SD) of 138.4 ± 52.34 and 0.8 ± 0.20 ng g-1, respectively. PAHs may mainly affected by traffic emission and biomass and wood combustion. Persistent organic pollutant accumulation rate (PAR) and depositional flux (DF) values showed that abundant PAHs might lost during top-down transport. The low trans- chordane (CHL)/cis-CHL ratio and PAR of OCPs may indicated few OCPs were inputted into the EIO recently. The results of binary isotope mixing modeling indicate the predominance of marine organic matter (MOM) in total organic carbon (TOC) of sediments. Fluoranthene (Flour) and pyrene (Py) might have potential biological effects in the EIO. The study provided background values for PAHs and OCPs in the Indian Ocean, and preliminarily revealed the fate of POPs in the open oceans.

Effects of environmental factors on selenite volatilization by freshwater microalgae

The accumulation and volatilization of Se by algae in surface water are important parts of the biogeochemical cycle of selenium but are also variable and complex. Experiments with 5-8 day of exposure under various temperatures, solution pH values, lighting regimes, and different initial Se concentrations were carried out to study the change in Se accumulation and volatilization behavior of algae. The study showed that algae accumulated and volatilized more Se under harsher environments, such as a lower pH, a shorter lighting time, and a higher Se load. The maximum average daily volatilization rate of Se was 234 ± 23 μg Se (g algae·d)-1, much greater than the values of previous studies. Therefore, in some Se-polluted water environments, when the pH of lakes is acidic, Se emissions to the atmosphere are much higher than currently estimated. Both the accumulation rate (Raccu) and volatilization rate (Rvol) of Se by algae were significantly negatively correlated with final pH, final OD, and residual Se in solution (Cres). Moreover, multiple linear regression equations were used to estimate the rates of Se accumulation and volatilization. This study provides theoretical basis data to quantify the contribution of selenium metabolism by algae to selenium biogeochemistry and a technical reference for the treatment of Se-containing wastewater.

Deposition rates and residence time of litter varies among beaches in the Lofoten archipelago, Norway

A considerable portion of marine litter pollutes the world's coastlines. Its accumulation on beaches represents the product of deposition and retention, processes which are not well understood. A mark-recapture study was performed with a two-week sampling interval at three sites in Lofoten, Norway. Deposition and retention vary over relatively small spatial scales (approx. 13 km radius). No correlation was found among sites in the timing of high and low deposition events, suggesting these are governed by local factors. Contrastingly, the correlation in the timing of high and low retention events was generally stronger among sites, suggesting these may be affected by regional factors. The results underline the importance of customising cleanup frequency for different beaches as spatiotemporal variation in the relative importance of deposition and retention dictate the optimal frequency for maximal removal of litter from circulation in the local marine environment, which cannot be discerned from accumulation (i.e., standing stock) alone.

Atmospheric fallout of radionuclides in peat bogs in the Western Segment of the Russian Arctic

This article presents the results of studies of the activity of radionuclides in peat-bog profiles of the European subarctic of Russia. Two peat profiles were collected in different areas of the Arkhangelsk region. The peat cores were used to determine ²¹⁰Pb, ¹³⁷Cs, ²⁴¹Am, ²³⁹Pu, ²⁴⁰Pu, ²³⁸U, and ²³⁴U content. To estimate the relationship between radionuclide activity and physicochemical parameters of peat, the content of organic matter, water-soluble salts, carbonates and ash, and the pH of aqueous and salt extracts were studied. Radionuclide activity concentrations in peat samples were measured using inductively coupled plasma mass spectrometry (ICP-MS), low-background semiconductor gamma spectrometry with a high-purity germanium (HPGe) detector, and alpha spectrometry. The ²¹⁰Pb chronology of peat cores was studied using a constant flow model based on the Monte Carlo simulation method. Comparison of ²¹⁰Pb dating data showed that the position of the maximum activity peaks of anthropogenic radionuclides shifted along the peat profile. This is probably due to the relative mobility of different radionuclides in the peat massif. Measurement of the atomic ratio ²⁴⁰Pu/²³⁹Pu showed that the main sources of pollution in the peatlands of the European subarctic of Russia are global fallout from atmospheric tests from the 1950s through 1980 and fallout from the Chernobyl nuclear accident in 1986. This study shows that a complex of radioactive isotopes in peat deposits can provide valuable information on the environmental pollution loads of subarctic territories.

Sediment trapping - An attempt to monitor temporal variation of microplastic flux rates in aquatic systems

Sediment trapping as a tool to monitor microplastic influx was tested in an urban boreal lake basin. The one-year-long trap monitoring consisted of 5-month and 7-month periods representing growing season and winter season (including the spring flood event), respectively. Sediment accumulation rate (SAR), and organic content were determined, highest SAR - 14.5 g/m²/d - was measured during the winter period. Microplastics were extracted from the sediment applying heavy-liquid density separation method and collected under a microscope for further identification with FTIR spectroscopy. PE was identified as the most abundant synthetic polymer type, while PP and PET are also present. The annual microplastic flux rate is 32 400 pieces/m²/year, and highest accumulation does not coincide with the highest SAR, but occurs during the growing season. Changes in the microplastic accumulation rates are related to seasonal conditions. Highest microplastic concentration with respect to dry sediment weight (10 200 pieces/kg) was observed in a growing season sample, while highest concentration with respect to sediment volume (1800 pieces/l) was observed during winter. This finding underlines the problems related to reporting microplastic concentrations in various units. The results highlight that sediment trap monitoring is an efficient tool for monitoring microplastic accumulation rate in aquatic environments and provides an opportunity to better understand and define processes controlling microplastic accumulation.

Marine macro-litter composition and distribution along the Kenyan Coast: The first-ever documented study

Macro-litter accumulation surveys were carried out in six beaches in Kilifi, Mombasa and Kwale Counties. Macro litter were collected, quantified and characterized to determine their composition, distribution and accumulation rates. The results showed that the accumulation rates ranged between 1.53 ± 1.23 and 11.46 ± 7.72 (for dry zones) and 2.69 ± 2.13 and 8.93 ± 7.87 items m^-1 day^-1 (for wet zones). Plastics and foam were the most abundant litter categories. Local products constituted about 88% of all the collected litter. Food packaging products constituted about 91.3% of all branded litter types. Marine litter pollution particularly by plastics was widespread in all studied coastal counties. However, a significant amount of litter encountered in the beaches was of local origin, thus a local solution to waste management (that will eliminate leakage into marine environments) will considerably reduce marine litter pollution in Kenya.

Concentrations and accumulation rates of polychlorinated biphenyls in soil along an urban-rural gradient in Shanghai

This study proposed an in situ soil experimental system to quantify concentration and accumulation rates of polychlorinated biphenyl (PCB) congeners in the soil in a rural-urban fringe and correlated them with multiple variables in the area. Variables, including road density, normalized difference vegetation index (NDVI), distance to the nearest highway and industrial area from the soil experimental sites, land-use impact index, population density, population change index (PCI), total population, and percentage of water area, were used to explain the concentration of different PCB congeners in soil during the experimental period. A proportion of 40.1%, 22.6%, 56.9%, and 34.3% accumulation rates of PCB8, PCB18, PCB28, and PCB118, respectively was explained by industrial developments, using stepwise linear regression analysis. NDVI was used to explain 33.6%, 61.5%, 49.1%, and 53.2% accumulation rates of PCB44, PCB101, PCB187, and PCB180, respectively. Filtering and transferring of airborne organic pollutants from atmosphere to soil by forests or tree stands and farmlands were all NDVI-related factors that affected the concentrations and accumulation rates of PCB congeners in soil. The traffic-related particle deposition might be the reason why the concentrations and accumulation rates of PCB congeners in soil were affected by road density. The findings can help quantitatively understand urbanization and the associated environmental effects. Graphic abstract.

Investigating Evolutionary Rate Variation in Bacteria

Rates of molecular evolution are known to vary between species and across all kingdoms of life. Here, we explore variation in the rate at which bacteria accumulate mutations (accumulation rates) in their natural environments over short periods of time. We have compiled estimates of the accumulation rate for over 34 species of bacteria, the majority of which are pathogens evolving either within an individual host or during outbreaks. Across species, we find that accumulation rates vary by over 3700-fold. We investigate whether accumulation rates are associated to a number potential correlates including genome size, GC content, measures of the natural selection and the time frame over which the accumulation rates were estimated. After controlling for phylogenetic non-independence, we find that the accumulation rate is not significantly correlated to any factor. Furthermore, contrary to previous results, we find that it is not impacted by the time frame of which the estimate was made. However, our study, with only 34 species, is likely to lack power to detect anything but large effects. We suggest that much of the rate variation may be explained by differences between species in the generation time in the wild.

Methods to reliably estimate faecal sludge quantities and qualities for the design of treatment technologies and management solutions

Sanitation access in urban areas of low-income countries is provided through unstandardized onsite technologies containing accumulated faecal sludge. The demand for infrastructure to manage faecal sludge is increasing, however, no reliable method exists to estimate total accumulated quantities and qualities (Q&Q) This proposed approach averages out complexities to estimate conditions at a centralized to semi-centralized scale required for management and treatment technology solutions, as opposed to previous approaches evaluating what happens in individual containments. Empirical data, demographic data, and questionnaires were used in Kampala, Uganda to estimate total faecal sludge accumulation in the city, resulting in 270 L/cap∙year for pit latrines and 280 L/cap∙year for septic tanks. Septic tank sludge was more dilute than pit latrine sludge, however, public toilet was not a distinguishing factor. Non-household sources of sludge represent a significant fraction of the total and have different characteristics than household-level sludge. Income level, water connection, black water only, solid waste, number of users, containment volume, emptying frequency, and truck size were predictors of sludge quality. Empirical relationships such as a COD:TS of 1.09 ± 0.56 could be used for more resource efficient sampling campaigns. Based on this approach, spatially available demographic, technical and environmental (SPA-DET) data and statistical relationships between parameters could be used to predict Q&Q of faecal sludge.

Kinetics of 210Po accumulation in moss body profiles

Radionuclide concentration analysis of total moss bodies often gave relatively different results than a separate analysis of each different morphological part of the same sample. The dynamics of the transfer of metals by dust uplifted from the soil and another approach, based on the diffusion of the two radionuclides to the moss, have been analyzed. In the proposed model, short- and long-term approaches have been applied. Each part of a moss's profile can show different radionuclides accumulation ability, including both ²¹⁰Pb and ²¹⁰Po isotopes. A first-order kinetic model has been used for ²¹⁰Po and ²¹⁰Pb transport between three body components of mosses. This mathematical approach has been applied for ²¹⁰Po activity concentration in the air estimation. For relatively clean deep forest region, calculated concentrations were from 17.2 to 43.8 μBqm^-3, while for urban air concentrations were higher from 49.1 to 104.9 μBqm^-3.

Atmospheric fallout radionuclides in peatland from Southern Poland

Two peat profiles were collected in a peat bog located in Southern Poland and their geochronology were determined using ²¹⁰Pb, ^238,239+240Pu and ¹³⁷Cs radiometric techniques. The ²¹⁰Pb chronologies were established using the constant rate of supply model (CRS) and are in good agreement with the Pu isotopes and ¹³⁷Cs time markers. Maximum activities of Pu isotopes were found at a depth corresponding to the early 1960s, which is the period characterized by the maximum nuclear weapon tests. The results showed that the ²¹⁰Pb method is the most accurate technique for the determination age and accumulation rate of a peat. The next part of this study calculated linear accumulation rates by analyzing ^238,239+240Pu and ¹³⁷Cs vertical distributions in the profiles. Activities of fallout isotopes were also measured in plants covering the peatland. The highest activities of ¹³⁷Cs and ²¹⁰Pb were found in Calluna vulgaris samples, and ^239+240Pu were found only in two samples (C. vulgaris and leaves of Oxycoccus quadripelatus).

Accumulation and sub-cellular partitioning of metals and As in the clam Venerupis corrugata: Different strategies towards different elements

The main goal of the present study was to assess accumulation, tolerance and sub-cellular partitioning of As, Hg, Cd and Pb in Venerupis corrugata. Results showed an increase of elements accumulation in V. corrugata with the increase of exposure. However, organisms presented higher capacity to accumulate Hg, Cd and Pb (BCF ≥ 12.8) than As (BCF ≤ 2.1) and higher accumulation rate for Cd and Pb than for Hg and As. With the increase of Hg exposure concentrations clams tended to increase the amount of metal bound to metal-sensitive fractions, which may explain the mortality recorded at the highest exposure concentration. Cd sub-cellular partitioning showed that with the increase of exposure concentrations V. corrugata increased the amount of metal in the cellular debris fraction, probably bound to the cellular membranes which explain the mortality recorded at the highest concentration. Results on As partitioning demonstrated that most of the metalloid was associated with fractions in the biologically detoxified metal compartment (BDM). Since high mortality was observed in clams exposed to As our results may indicate that this strategy was not enough to prevent clams from toxic effects and mortality occurred. When exposed to Pb most of the metal was in the BDM compartment, but in this case the metal was mostly in the metal-rich granules fraction which seemed to be efficient in preventing clams from toxicity, and no mortality was recorded. Our study further revealed that As and Hg were the most available elements to be biomagnified through the food chain.

Spatial and temporal variability of snow chemical composition and accumulation rate at Talos Dome site (East Antarctica)

Five snow pits and five firn cores were sampled during the 2003-2004 Italian Antarctic Campaign at Talos Dome (East Antarctica), where a deep ice core (TALDICE, TALos Dome Ice CorE, 1650m depth) was drilled in 2005-2008 and analyzed for ionic content. Particular attention is spent in applying decontamination procedures to the firn cores, as core sections were stored for approximately 10years before analysis. By considering the snow pit samples to be unperturbed, the comparison with firn core samples from the same location shows that ammonium, nitrate and MSA are affected by storage post-depositional losses. All the other measured ions are confirmed to be irreversibly deposited in the snow layer. The removal of the most external layers (few centimeters) from the firn core sections is proved to be an effective decontamination procedure. High-resolution profiles of seasonal markers (nitrate, sulfate and MSA) allow a reliable stratigraphic dating and a seasonal characterization of the samples. The calculated mean accumulation-rate values range from 70 to 85mmw.e.year(-1), in the period 2003-1973 with small differences between two sectors: 70-74mmw.e.year(-1) in the NNE sector (spanning 2003-1996years) and 81-92mmw.e.year(-1) in the SSW sector (spanning 2003-1980years). This evidence is interpreted as a coupled effect of wind-driven redistribution processes in accumulation/ablation areas. Statistical treatment applied to the concentration values of the snow pits and firn cores samples collected in different points reveals a larger temporal variability than spatial one both in terms of concentration of chemical markers and annual accumulation. The low spatial variability of the accumulation rate and chemical composition measured in the five sites demonstrates that the TALDICE ice core paleo-environmental and paleo-climatic stratigraphies can be considered as reliably representative for the Talos Dome area.