Surface chromium on Terracotta Army bronze weapons is neither an ancient anti-rust treatment nor the reason for their good preservation
TL;DR: It is shown that the lacquer used to cover warriors and certain parts of weapons is rich in chromium, and it is demonstrated that chromium on the metals is contamination from nearby lacquer after burial, and the chromium anti-rust treatment theory should be abandoned.
Abstract: For forty years, there has been a widely held belief that over 2,000 years ago the Chinese Qin developed an advanced chromate conversion coating technology (CCC) to prevent metal corrosion. This belief was based on the detection of chromium traces on the surface of bronze weapons buried with the Chinese Terracotta Army, and the same weapons’ very good preservation. We analysed weapons, lacquer and soils from the site, and conducted experimental replications of CCC and accelerated ageing. Our results show that surface chromium presence is correlated with artefact typology and uncorrelated with bronze preservation. Furthermore we show that the lacquer used to cover warriors and certain parts of weapons is rich in chromium, and we demonstrate that chromium on the metals is contamination from nearby lacquer after burial. The chromium anti-rust treatment theory should therefore be abandoned. The good metal preservation probably results from the moderately alkaline pH and very small particle size of the burial soil, in addition to bronze composition.
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TL;DR: In this article, a comprehensive understanding of the fundamentals of the microstructural evolution during FSW/P has been developed, including the mechanisms underlying the development of grain structures and textures, phases, phase transformations and precipitation.
390 citations
TL;DR: It is shown that atmospheric transport is a major pathway for road plastic pollution over remote regions, and it is suggested that the Arctic may be a particularly sensitive receptor region, where the light-absorbing properties of TWPs and BWPs may also cause accelerated warming and melting of the cryosphere.
Abstract: In recent years, marine, freshwater and terrestrial pollution with microplastics has been discussed extensively, whereas atmospheric microplastic transport has been largely overlooked. Here, we present global simulations of atmospheric transport of microplastic particles produced by road traffic (TWPs – tire wear particles and BWPs – brake wear particles), a major source that can be quantified relatively well. We find a high transport efficiencies of these particles to remote regions. About 34% of the emitted coarse TWPs and 30% of the emitted coarse BWPs (100 kt yr−1 and 40 kt yr−1 respectively) were deposited in the World Ocean. These amounts are of similar magnitude as the total estimated direct and riverine transport of TWPs and fibres to the ocean (64 kt yr−1). We suggest that the Arctic may be a particularly sensitive receptor region, where the light-absorbing properties of TWPs and BWPs may also cause accelerated warming and melting of the cryosphere. Plastic pollution is a critical concern across diverse ecosystems, yet most research has focused on terrestrial and aquatic transport, neglecting other mechanisms. Here the authors show that atmospheric transport is a major pathway for road plastic pollution over remote regions.
373 citations
TL;DR: In this paper, a coupled CNN-LSTM model was proposed to predict water quality variables, namely dissolved oxygen (DO; mg/L) and chlorophyll-a (Chl-a; µg/L), in the Small Prespa Lake in Greece.
Abstract: Water quality monitoring is an important component of water resources management. In order to predict two water quality variables, namely dissolved oxygen (DO; mg/L) and chlorophyll-a (Chl-a; µg/L) in the Small Prespa Lake in Greece, two standalone deep learning (DL) models, the long short-term memory (LSTM) and convolutional neural network (CNN) models, along with their hybrid, the CNN–LSTM model, were developed. The main novelty of this study was to build a coupled CNN–LSTM model to predict water quality variables. Two traditional machine learning models, support-vector regression (SVR) and decision tree (DT), were also developed to compare with the DL models. Time series of the physicochemical water quality variables, specifically pH, oxidation–reduction potential (ORP; mV), water temperature (°C), electrical conductivity (EC; µS/cm), DO and Chl-a, were obtained using a sensor at 15-min intervals from June 1, 2012 to May 31, 2013 for model development. Lag times of up to one (t − 1) and two (t − 2) for input variables pH, ORP, water temperature, and EC were used to predict DO and Chl-a concentrations, respectively. Each model’s performance in both training and testing phases was assessed using statistical metrics including the correlation coefficient (r), root mean square error (RMSE), mean absolute error (MAE), their normalized equivalents (RRMSE, RMAE; %), percentage of bias (PBIAS), Nash–Sutcliffe coefficient ($$E_{NS}$$), Willmott’s Index, and graphical plots (Taylor diagram, box plot and spider diagram). Results showed that LSTM outperformed the CNN model for DO prediction, but the standalone DL models yielded similar performances for Chl-a prediction. Generally, the hybrid CNN–LSTM models outperformed the standalone models (LSTM, CNN, SVR and DT models) in predicting both DO and Chl-a. By integrating the LSTM and CNN models, the hybrid model successfully captured both the low and high levels of the water quality variables, particularly for the DO concentrations.
182 citations
TL;DR: The results indicate that the diversity × ecosystem-function relationship can be impaired under non-favorable conditions in soils, and that to understand changes in soil C cycling the authors need to account for the multiple facets of global changes.
Abstract: Empirical evidence for the response of soil carbon cycling to the combined effects of warming, drought and diversity loss is scarce. Microbial carbon use efficiency (CUE) plays a central role in regulating the flow of carbon through soil, yet how biotic and abiotic factors interact to drive it remains unclear. Here, we combine distinct community inocula (a biotic factor) with different temperature and moisture conditions (abiotic factors) to manipulate microbial diversity and community structure within a model soil. While community composition and diversity are the strongest predictors of CUE, abiotic factors modulated the relationship between diversity and CUE, with CUE being positively correlated with bacterial diversity only under high moisture. Altogether these results indicate that the diversity × ecosystem-function relationship can be impaired under non-favorable conditions in soils, and that to understand changes in soil C cycling we need to account for the multiple facets of global changes.
175 citations
TL;DR: In this article, a review of the recent findings in biochar production, factors affecting the biochar properties and biochar engineering is presented, and an insight into the potential of biochar as an immobilization support in terms of its properties, contributing factors and comparison with other support materials.
154 citations
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TL;DR: In this paper, the authors reviewed the emissions, environmental fate and transport, analytical chemistry, uptake and metabolism, toxicology, and human epidemiology of chromium, and found that chromium is unique among regulated toxic elements in the environment in that different species of the chromium are regulated in different ways, in contrast to other toxic elements where the oxidation state is not distinguished.
Abstract: This article reviews the emissions, environmental fate and transport, analytical chemistry, uptake and metabolism, toxicology, and human epidemiology of chromium Chromium is unique among regulated toxic elements in the environment in that different species of chromium, specifically chromium (III) and chromium (VI), are regulated in different ways, in contrast to other toxic elements where the oxidation state is not distinguished In both industrial and environmental situations chromium (III) and chromium (VI) can inter-convert, with reduction of chromium (VI) to chromium (III) generally being favored in most environmental situations Chromium released into the air, water, and soil can be transported among the various environmental media through various intermedia transport processes Once in the environment, chromium can be taken up by human and other ecological receptors Chromium (III) is generally absorbed through cell membranes albeit to a significantly lesser degree than chromium (VI) Because most
754 citations
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01 Feb 2002
TL;DR: A review of the literature on copper and its alloys integrates information on pigments, corrosion products and minerals that are usually considered separately though they are often the same compounds as discussed by the authors.
Abstract: This 190 year review of the literature on copper and its alloys integrates the information on pigments, corrosion products and minerals that are usually considered separately though they are often the same compounds. The various environmental conditions to which copper alloy objects may be exposed including burial, outdoor, and indoor museum environments and the methods used to conserve them are discussed and information is included on ancient and historical technologies, the nature of patina as it pertains to copper and bronze and the use of copper corrosion materials as pigments. Chapters are organized primarly by chemical corrosion products and includetopics such as early technologies, copper chlorides and bronze disease, the chemistry and history of turquoise, Egyptian blue and other synthetic copper silicates, the organics salts of copper in bronze corrosion and bronze patinas. A detailed survey of conservation treatments for bronze objects is also provided. Four appendices cover copper and bronze chemistry, replication experiments for early pigments recipes, a list of copper minerals and corrosion products and X-ray diffraction studies. -- ICCROM
358 citations
TL;DR: In this article, the authors investigated the relationship between soil organic carbon (SOC) stocks and pertinent environmental factors, i.e., precipitation, temperature, elevation, slope gradient, clay plus silt content (<20 mu m) and land use.
229 citations
TL;DR: Leersia hexandra Swartz (Gramineae), which occurs in Southern China, has been found to be a new chromium hyperaccumulator by means of field survey and pot-culture experiment, and has potential for usage in the phytoremediation of Cr-contaminated soil and water.
172 citations
TL;DR: In this article, a chromate conversion coating formed on an article in an acidic chromating bath in reaction with a metal surface on the article, such as cadmium or zinc, is stabilized by subjecting the coating to an alkaline bath having a pH in a range between 11 and 12, immediately upon removing the article from the chromate bath and without first rinsing the article in water.
113 citations