To study the abnormal failure of magnesium anodes for buried pipelines in marine engineering in the unique environment of mudflats, a strain of a sulfate-reducing prokaryote (SRP) was isolated from ...pipe-laying soil, and identified as
sp. HQM3. Weight-loss test, electrochemical measurements, SEM, EDS, XRD, and CLSM techniques were used to study the effect of corrosion on the AZ31B magnesium alloy. Under the influence of SRP, the magnesium alloy corroded severely at rates up to 1.31 mm/year in the mudflat environment. SRP accelerated corrosion by 0.3mm/year. Pitting occurred on the samples in both abiotic and biotic systems. The pitting depth reached 163.47 μm in the biotic system after 14 days. The main composition of a petal-like corrosion product was Mg(OH)
. The results show that a mudflat environment can lead to an accelerated corrosion of magnesium alloys.
In recent years, research on heavy metals has become very popular, because the status of heavy metals can reflect the marine environment of a region. Based on this, this paper carries out the ...evaluation and analysis of heavy metals in marine sediments. Based on the content of the heavy metals in the coastal sediments of Binhai, Jiangsu, from coastal waters in the autumns of 2012, 2015, and 2018, the environmental quality was quantitatively evaluated using the geoaccumulation index and potential ecological risk. The sources of the heavy metals were identified by a multivariate analysis, and the changes over the years and the distribution characteristics were analyzed. Hg and Cr were at a clean grade, while other heavy metals contents indicated mild-to-moderate pollution in the three sets of monitoring data. The comprehensive ecological risk index assessment showed that Hg and Cd were at a moderate ecological risk level in the three sets of monitoring data. Overall, the study area exhibited a mild-to-moderate ecological risk level, with a continuously increasing trend. The overall content of heavy metal in this sea area is greatly affected by human activities, with high values occurring in ports, estuaries, and outer seas.
In this study, the characteristics and spatial distribution of heavy metal pollution in the surface sediments of Haizhou Bay, one of the largest bays in China, were investigated. The potential ...ecological risks posed by seven heavy metals were analyzed by using the Hakanson comprehensive pollution index and geoaccumulation index (Igeo). A correlation matrix map was applied to explore the relationships between the seven heavy metals and environmental elements. The results showed that the contents of heavy metals in the southern area of Haizhou Bay are high, whereas those in the northern area are low. The results of the pollution assessment of heavy metals were largely consistent between the Igeo method and the potential ecological risk index method. The seven heavy metals ranked in descending order of potential ecological risk coefficient as follows: Hg, Cd, As, Pb, Cu, Cr and Zn. The environmental quality assessment showed that Hg is the main heavy metal pollutant in surface sediments in Haizhou Bay, and some stations have reached a high pollution level and should receive more attention.
•Hg is the main heavy metal pollutant in surface sediments in Haizhou Bay.•The southern region of Haizhou Bay is the main area with high ecological risk.•Six heavy metals except Pb probably originated from the same source or similar sources.
Marine protected areas (MPAs) are an important means in protecting marine ecological functions and landscapes. Existing ecological restoration measures are singular and lack pertinence and ...systematicness. Thus, a gap between the expectations and real ecological restoration effects exists. This study was based on Haizhouwan National Marine Park, a national MPA of China. After investigating and evaluating the ecological environment in the Haizhouwan protected area (HPA), ecosystem health assessments to three ecological subsystems (i.e., island terrestrial, intertidal, and neritic ecosystems) and vulnerability assessments to the main protected objects (i.e., landforms) were conducted. This study was integrated with the functional zonation of the HPA, which enabled it to conduct an analytic hierarchy process for the assessment results to obtain ecological restoration zoning. According to the zoning, the HPA can be divided into 12 ecological restoration zones, namely, 2 key restoration zones, 3 general restoration zones, 2 taking-into-account restoration zones, and 5 maintaining-the-status zones. This paper also provides pertinent ecological restoration measures and recommendations to the environmental, ecological, and protected object problems existing in different zones. The study results can provide empirical references for the development of ecological restoration plans and measures for the HPA. The zoning method can also be applied to the ecological protection and restoration research of other MPAs.
•Ecosystem health assessments as well as vulnerability assessments were conducted.•Analytic hierarchy process integrated with functional zonation was used for assessment results.•This paper provided pertinent ecological restoration measures and recommendations.•The zoning method can be applied to ecological protection and restoration of other MPAs.
Abstract
We examine how analysts respond to non‐financial information about environmental, social responsibility, and corporate governance (ESG) performance and find good ESG performance lessens ...analysts' optimistic bias. We verify the mediating role of financial transparency that superior ESG performance decreases the level of information asymmetry between firms and analysts and improves financial transparency, thus weakening optimistic bias. Analysts' optimistic bias rises with increased institutional holdings and diminishes with heightened economic policy uncertainty. Social responsibility makes a larger reducing effect on analyst optimistic bias than corporate governance and environmental protection. Our findings have important implications for encouraging firms to emphasize ESG performance and improving stock market efficiency.
The Jiangsu coastal environment in China is affected by pollution, and the Cu, Pb, Cd, Zn, Cr, As, and Hg concentrations in the surface sediment of Dafeng Port during 2011–2017 were analyzed to ...determine their contamination and ecological risks. The multi-year average of Zn, Cr, Pb, Cu, As, Cd, and Hg concentrations were 50.10, 40.32, 12.41, 11.76, 8.67, 0.08, and 0.04 mg/kg, respectively, which were generally higher than their background values, except for those of Cu and Cr. The spatial distribution of heavy metals were similar, and the highest concentrations were measured near Dafeng Port and coastal river inlets. The geoaccumulation index generally indicated moderate–low ecological risk, except for Cd. Multivariate statistical analyses showed that Pb, Zn, Cr, As, Hg, Cd, and petroleum were strongly influenced by anthropogenic activities, whereas Cu derived from both natural and anthropogenic sources. This study provides important information for the management of heavy metal contamination.
•High heavy metal concentrations occurred near Dafeng Port and coastal river inlets.•Igeo values showed an uncontaminated environment and moderate–low ecological risk.•However, Cd is an important contributor to pollution in and around Dafeng Port.•Pb, Zn, Cr, As, Hg, and Cd had anthropogenic sources, but Cu also had natural sources.•We provide information for the management of heavy metals along the Jiangsu coast.
The composition of organic matter in biogenic calcium carbonate has long been a mystery, and its role has not received sufficient attention. This study is aimed at elucidating the bio-mineralisation ...and stability of amorphous calcium carbonate (ACC) and vaterite containing organic matter, as induced by
Bacillus subtilis
. The results showed that the bacteria could induce various structural forms of CaCO
3
, such as biogenic ACC (BACC) or biogenic vaterite (BV), using the bacterial cells as their template, and the carbonic anhydrase secreted by the bacteria plays an important role in the mineralisation of CaCO
3
. The effects of Ca
2+
concentration on the crystal structure of CaCO
3
were ascertained; when the amount of CaCl
2
increased from 0.1% (m/v) to 0.8% (m/v), the ACC was transformed to polycrystalline vaterite. The XRD results demonstrated that the ACC and vaterite have good stability in air or deionised water for one year, or even when heated to 200 °C or 300 °C for 2 h. Moreover, the FTIR results indicated that the BACC or BV is rich in organic matter, and the contents of organic matter in biogenic ACC and vaterite are 39.67 wt% and 28.47 wt%, respectively. The results of bio-mimetic mineralisation experiments suggest that the protein secreted by bacterial metabolism may be inclined to inhibit the formation of calcite, while polysaccharide may be inclined to promote the formation of vaterite. Our findings advance our knowledge of the CaCO
3
family and are valuable for future research into organic-CaCO
3
complexes.
The amorphous calcium carbonate (ACC) or polycrystalline vaterite, which has long-term water stability and thermal stability, can be induced by bacteria. These biogenic CaCO
3
are organo-mineral complexes.
Purpose We aim to clarify the effect of economic uncertainty on Chinese stock market fluctuations. We extend the understanding of the asymmetric connectedness between economic uncertainty and stock ...market risk and provide different characteristics of spillovers from economic uncertainty to both upside and downside risk. Furthermore, we aim to provide the different impact patterns of stock market volatility following several exogenous shocks. Design/methodology/approach We construct a Chinese economic uncertainty index using a Factor-Augmented Variable Auto-Regressive Stochastic Volatility (FAVAR-SV) model for high-dimensional data. We then examine the asymmetric impact of realized volatility and economic uncertainty on the long-term volatility components of the stock market through the asymmetric Generalized Autoregressive Conditional Heteroskedasticity-Mixed Data Sampling (GARCH-MIDAS) model. Findings Negative news, including negative return-related volatility and higher economic uncertainty, has a greater impact on the long-term volatility components than positive news. During the financial crisis of 2008, economic uncertainty and realized volatility had a significant impact on long-term volatility components but did not constitute long-term volatility components during the 2015 A-share stock market crash and the 2020 COVID-19 pandemic. The two-factor asymmetric GARCH-MIDAS model outperformed the other two models in terms of explanatory power, fitting ability and out-of-sample forecasting ability for the long-term volatility component. Research limitations/implications Many GARCH series models can also combine the GARCH series model with the MIDAS method, including but not limited to Exponential GARCH (EGARCH) and Threshold GARCH (TGARCH). These diverse models may exhibit distinct reactions to economic uncertainty. Consequently, further research should be undertaken to juxtapose alternative models for assessing the stock market response. Practical implications Our conclusions have important implications for stakeholders, including policymakers, market regulators and investors, to promote market stability. Understanding the asymmetric shock arising from economic uncertainty on volatility enables market participants to assess the potential repercussions of negative news, engage in timely and effective volatility prediction, implement risk management strategies and offer a reference for financial regulators to preemptively address and mitigate systemic financial risks. Social implications First, in the face of domestic and international uncertainties and challenges, policymakers must increase communication with the market and improve policy transparency to effectively guide market expectations. Second, stock market authorities should improve the basic regulatory system of the capital market and optimize investor structure. Third, investors should gradually shift to long-term value investment concepts and jointly promote market stability. Originality/value This study offers a novel perspective on incorporating a Chinese economic uncertainty index constructed by a high-dimensional FAVAR-SV model into the asymmetric GARCH-MIDAS model.
Mangroves bear enormous ecosystem value, while the ecosystems are facing increasing environmental pressures. In this study, 73 samples of soil sediments in mangroves, paddy fields, grasslands, ...forests, and shrimp ponds were collected from Shankou Mangrove National Nature Reserve (SKMNNR), Guangxi Zhuang Autonomous Region, China. The pollution status and ecological risks of heavy metal elements of Cr, Ni, Cu, Zn, As, Cd, Pb, V, and Co were determined using the enrichment factor (EF), geoaccumulaton index (Igeo), and potential ecological risk index (PERI). The average concentration is shown to be substantially lower than the background value. In general, the Igeo values indicated that the pollution conditions of different land use types in SKMNNR are relatively minor. Most of the PERI values were at the moderate level. This study demonstrates that the current status of sediment quality in SKMNNR is relatively good, and the pollution level is relatively low. Large-scale coastal aquaculture development and industrial expansion should not no longer be permitted there.
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•Understanding the heavy metal risk plays an important role in mangrove wetlands.•The heavy metal concentration in different land use types varies substantially.•Igeo indices, EF value, and PERI value of heavy metal indicates minor enrichment.•A strong significant correlation suggests the absence of contamination•Conservation plans considering pollution status are needed.
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