Large variation in periphyton δ13C and δ15N values in the upper Great Lakes: Correlates and implications

Stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) are frequently used to examine food web structure. Despite periphyton's importance to lake food webs, little is known about spatial variation of periphyton δ¹³C and δ¹⁵N values in the Great Lakes. We present periphyton δ¹³C and δ¹⁵N values from 28 sites the upper Great Lakes, including Lake Superior, the north shore of Lake Michigan, and Green Bay. We also examined variation in periphyton isotope values relative to several water quality parameters (TP, TN, TKN, NO₃⁻, K_d) as well as periphyton C:N. There was a large range in both periphyton δ¹³C (range = 13.5‰) and δ¹⁵N (range = 10.2‰) among sites. Periphyton in more eutrophic sites had more depleted δ¹³C and more enriched δ¹⁵N compared to more oligotrophic sites. Our finding of high variability in periphyton isotope values in the Upper Great Lakes has implications for stable isotope-based reconstructions of food web structure.     

TrajStat: GIS-based software that uses various trajectory statistical analysis methods to identify potential sources from long-term air pollution measurement data

Statistical analysis of air mass back trajectories combined with long-term ambient air pollution measurements are useful tools for source identification. Using these methods, the geographic information system (GIS) based software, TrajStat, was developed to view, query, and cluster the trajectories and compute the potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analyses when measurement data are included.     

Improved GDP spatialization approach by combining land-use data and night-time light data: a case study in China’s continental coastal area

Gross domestic product (GDP) reflects a nation or region’s economic growth as a whole, and is the sum of product in the primary, secondary, and tertiary sectors of the economy in the area. However, statistical GDP data is problematic in integrated application with geographical data. The GDP spatialization data, which shows the GDP in grid cells and often is obtained by operating a spatialization model, is more useful than its officially published statistical data recorded by administrative units in both spatial representation and application. Thus, there is a need to improve the GDP spatialization models, and to present these models in a way as clear and transparent as possible. In this article, by taking China’s continental coastal area as a case study area, we combined economic census data, land-use data, and night-time light data together, and developed a technique that we call the ‘dynamic regionalization’ method to improve the GDP spatialization products. We then created GDP spatialization models for three sectors of the economy (i.e. the primary, the secondary, and the tertiary sector) in 2000, 2005, and 2010, respectively. We find the following. (1) Because the ‘overglow’ effect of night-time light data has a bad influence on spatialization models, we used land-use data to distinguish the distribution plots of the tertiary sector on night-time light images. Compared with setting a threshold merely, land-use data can more effectively remove the ‘overglow’ effect. (2) Owing to the prominent spatial heterogeneity of GDP distribution in China’s continental coastal area, building one spatialization model for the whole area would probably produce the estimated products with poor accuracy, so the ‘dynamic regionalization’ method was adopted to dynamically divide the whole study area into several subregions, and build separate spatialization models for each subregion. The accuracy assessment showed that the new method improved the accuracy of GDP spatialization data, especially in the area with high spatial heterogeneity.     

Effect of concentration,pH and ionic strength on the kinetic self-assembly of acid-soluble collagen from walleye pollock (Theragra chalcogramma) skin

The effects of concentration, pH value and ionic strength on the kinetic self-assembly of acid-soluble collagen from walleye pollock (Theragra chalcogramma) skin were investigated. A two-phase kinetic process was provided which included the formation of nucleus center and nucleus growth, the first phase being the controlled step for collagen self-assembly. Collagen showed marked assembly behavior when concentration reaching and above 0.6 mg/mL, and higher concentration could accelerate collagen self-assembly. Rate constants of the first and second assembly phase both increased with pH to a maximum around pH 7.2 and then decreased, indicating that pH 7.2 was the optimum pH value for collagen self-assembly. The kinetics of collagen self-assembly could be modulated by NaCl concentration. The concentration of NaCl from 30 to 60 mM was more suitable to self-assemble for pollock skin collagen.     

Heavy metal pollution status in surface sediments of the coastal Bohai Bay

Bohai Bay, the second largest bay of Bohai Sea, largely due to the huge amount of pollutants discharged into it annually and its geohydrologic condition, is considered to be one of the most polluted marine areas in China. To slow down, halt and finally reverse the environmental deterioration of Bohai Sea, some researchers have proposed to connect it with Jiaozhou Bay in the western coast of Southern Yellow Sea by digging an interbasin canal through Shandong Peninsula. In order to assess the heavy metal pollution and provide background information for such a large geoengineering scheme, surface sediments from 42 stations covering both riverine and marine regions of the northwestern coast of Bohai Bay were analyzed for heavy metal content and fractionation (Cd, Cr, Cu, Ni, Pb and Zn). Three empirically derived sediment quality guidelines were used to assess the pollution extent of these metals. The studied metals had low mobility except for Cd at all stations and Zn at some riverine stations. Although a high mobility of Cd was observed, it could hardly cause a bad effect on the environment owing to its low total concentrations. Anthropogenic influence on the accumulation of studied heavy metals in sediments of Bohai Bay was obvious, but their contents were relatively lower to date comparing with some other marine coastal areas that receive important anthropogenic inputs. Taking as a whole, surface sediments of northwestern Bohai Bay had a 21% probability of toxicity based on the mean effects range-median quotient.     

Reconstruction of satellite chlorophyll-a data using a modified DINEOF method: a case study in the Bohai and Yellow seas,China

A data-interpolating empirical orthogonal function (DINEOF) method was applied to 8 day composited satellite-derived chlorophyll-a (chl-a) images to produce a long-term, cloud-free chl-a data set over the Bohai Sea and Yellow Sea from 1997 to 2010. In this study, two additional procedures, a depth subdivision scheme and a new process of outlier detection and removal, improved the overall performance of this interpolating technique. The whole chl-a data set was divided into three subsets according to 20 and 50 m isobaths and the DINEOF reconstruction was performed on each subset. This subdivision scheme can significantly improve the accuracy of reconstruction, but is achieved with loss of computational efficiency due to the increased number of iterations required for reconstruction of the three subsets. A simple and new outlier detection method based on standardized residuals theory was developed to eliminate the spurious values (outliers) from the chl-a data set. The accuracy of the DINEOF reconstruction was significantly improved by the application of the outlier detection and removal process.     

The effect of triethylamine on the hydrodechlorination of chlorophenols on Pd/C at low temperature

The hydrodechlorination (HDC) of chlorophenols on 5 wt.% Pd/C catalyst was investigated at low temperature under ordinary pressure by using triethylamine (Et₃N) as a base additive. The inhibition effect of Et₃N on the HDC existed obviously and can be efficiently reduced by stepwise addition of Et₃N. For the first time, the high activity of Pd/C for HDC of chlorophenols was observed at 258 K.     

Templated electrodeposition of Ag7NO11 nanowires with very high oxidation states of silver

The templated electrodeposition of 200 nm diameter nanowires of the argentic oxynitrate Ag(Ag₃O₄)₂NO₃ phase is reported. Their high surface-to-volume ratio and the high average oxidation state of Ag make these wires promising candidates for nanoscale redox processes in which both a high volumetric charge density and a high discharge rate are required. The antibiotic activity of these nanowires was demonstrated by inhibiting the growth of Bacillus cereus bacteria.     

The effect of micro-grinding and micro-graphite flotation to upgrade the quality of calcite concentrate,with reference to Kurikka calcite marble deposit,Finland

High purity of calcium carbonate deposits are rare. Even the purest calcite marbles contain accessory minerals, which may degrade the deposit in terms of its suitability for paper pigment application. Most of these impurities could be removed by traditional calcite–silicate flotation to produce quality ground calcium carbonate. However, micro-graphite enclosed by calcite remains un-liberated with the traditional flotation particle size distribution. Further grinding alone simply exposes such graphite on the surface of calcite and reduces the brightness of the concentrate.In Kurikka calcite marble, micro-graphite particles of varying morphology occur along calcite grain boundaries and other crystallographic discontinuities. Due to such submicroscopic graphite particles, the calcite concentrate produced from the Kurikka calcite marble by calcite–silicate flotation gives an average ISO brightness value of 83.7.This study shows the application of micro-grinding followed by micro-graphite flotation to remove such fine-grained graphite. As a result, the quality of the calcite concentrate was upgraded to an average brightness value of 92.3.     

Microplastics in soils: a review of possible sources,analytical methods and ecological impacts

Microplastics are emerging persistent pollutants that have been extensively detected in aqueous environments. Yet, scientists have little knowledge of microplastic pollution in soils. This study reviewed over 60 articles, with the following objectives: (i) to discuss sources and the global distribution of microplastics in soils; (ii) to evaluate current extraction techniques and analytical methods for microplastics in soils; and (iii) to comprehensively assess their adverse impacts on soils and soil organisms. Moreover, this review highlights the lack of research into microplastic contamination in soils as a significant knowledge gap. Research into the fate, sources and analytical techniques of soil microplastics and the interactions between soil organisms, soils and microplastics is essential in order to underpin management decisions aimed at safeguarding the ecological integrity of our soils. © 2020 Society of Chemical Industry