A Scalable Cross-Chain Access Control and Identity Authentication Scheme.

Cross-chain is an emerging blockchain technology which builds the bridge across homogeneous and heterogeneous blockchains. However, due to the differentiation of different blockchains and the lack of access control and identity authentication of cross-chain operation subjects, existing cross-chain technologies are struggling to accomplish the identity transformation of cross-chain subjects between different chains, and also pose great challenges in terms of the traceability and supervision of dangerous transactions. To address the above issues, this paper proposes a scalable cross-chain access control and identity authentication scheme, which can authenticate the legitimacy of blockchains in the cross-chain system and ensure that all cross-chain operations are carried out by verified users. Furthermore, it will record all cross-chain operations with the help of Superchain in order to regulate and trace illegal transactions. Our scheme is scalable and, at the same time, has low invasiveness to blockchains in the cross-chain system. We implement the scheme and accordingly conduct the evaluations, which prove its security, efficiency, and scalability.

Source apportionment and risk assessment for available occurrence forms of heavy metals in Dongdahe Wetland sediments, southwest of China.

Urban wetland ecosystems are easily influenced by heavy metals (HMs) because of their functional properties. In this study, absolute principal component scores-multivariate linear regression (APCS-MLR) and positive matrix factorization (PMF) receptor models were applied for the source apportionment of available occurrence forms of heavy metals (AHMs) of surface sediments in a typical urban wetland of Dianchi Lake, southwest of China. The risk assessment was conducted to evaluate the potential ecological/human health risks of HMs. Results indicated that Zn, Pb, and Cr were the major pollutants affected by anthropogenic activities in sediments and their concentrations were significantly exceeding the background value. Most of the highly AHMs-polluted area was close to the river in wetland, and the concentration distribution of all AHMs were generally low in the southwest and high in the northeast. Both APCS-MLR and PMF models identified three comparable classes of potential sources, namely (1) agricultural fertilizer/insecticide, atmospheric deposition, and traffic emissions; (2) natural transitions; and (3) industrial and sewage wastes. Moreover, the comparison results implied that the PMF model was more feasible for quantifying AHMs sources in wetland sediments since it is capable to analyze one more source, namely plant maintenance and waterfowl feeding, and has higher accuracy in predicting the concentrations of AHMs. In addition, the risk assessment model revealed that all these HMs were within the acceptable ranges of ecological and carcinogenic/non-carcinogenic human health risks. Among these, ingestion was the major exposure pathway of HMs from local areas, followed by dermal exposure and oral or nasal inhalation. However, children were more easily exposed to HMs than adults by ingestion due to their hand-to-mouth behaviors. This study aims to assess the HM pollution status in a plateau urban wetland, and provides a practical case for modeling source apportionment and risk assessment of HMs in wetland sediments.