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Purpose: Changes in the magnetic phase, magnetic concentration, and/or magnetic grain-sized of dust-bound iron-bearing minerals depend on both lithogenic components and anthropogenic inputs. Knowledge of the magnetic properties of road dusts in various road ecosystems is of paramount importance to control dust pollution for the benefit of the environment and human health. Methods: The magnetic characteristics of road dusts, collected in the coastal areas of southern Fujian, China, were determined via magnetic measurements, X-ray diffraction analysis, Mössbauer spectroscopy (MS), and scanning electron microscopy with integrated energy-dispersive X-ray spectrometry. Results: Analyses of the temperature dependence of magnetization, backfield demagnetization, and hysteresis loops suggested that the main magnetic carriers in road dusts were low-coercivity minerals with minimal antiferromagnetic phases derived from anthropognic sources. The coefficients of variation for χLF, SIRM, and χARM were 53.46%, 50.98%, and 58.56%, respectively. Samples with high values of χLF had a high ratio of iron ions in the octahedral B and tetrahedral A sites in magnetite. The most common iron oxides in the dust-bound iron-bearing minerals were non-stoichiometric magnetite, hematite, and possibly metallic iron. Elevated concentrations of trace metals (e.g., Cd, Cr, Co, and V) in the dust-bound iron-bearing minerals partially confirmed the coexistence of magnetic minerals and trace metals in the road dusts. Conclusions: Analysis of the spatial characteristics of magnetic concentration–related parameters will be useful in accurately documenting and tracking levels of pollution. [ABSTRACT FROM AUTHOR]

To characterize the magnetic signature of sediment heavy metal contamination and identify sources of heavy metals in mangroves, 83 sediment specimens were collected from three mangroves in Fujian, China; various magnetic parameters and heavy metal concentrations were then determined. Variation in magnetic magnetization among specimens was linked to changes in pseudo-single-domain magnetite. Average values of Co, Cu, Ni, and Zn (but not Cr or Pb) were slightly lower than background levels. Geochemical evidence suggested that Co, Cr, Ni, Ti, and V were associated with lithogenic minerals in the sediment, while Cu, Pb, and Zn were associated with terrigenous minerals. A strong positive correlation was seen between magnetic concentration-dependent parameters and metal concentrations (Cu, Pb, and Zn), suggesting enrichment of metal-containing magnetic minerals with heavy metal pollution. The combined assessment of both sediment magnetic properties and heavy metal concentrations thus provides insight into the pollution status of mangrove sediments under complex conditions. • Top sediments of the mangrove forests contained various kinds of detrital magentic particle. • Sediment Pb, Cu, and Zn were mainly associated with terrigenous inputs. • Correlation analysis of selected heavy metals and magnetic mineral concentration-dependent parameters were determined. [ABSTRACT FROM AUTHOR]

Deciphering the mobility and transfer of heavy metals in transition buffers is vital to understanding their behavior in mangrove forests. As one of the most redox-sensitive metals, the geochemical fractionation of sediment Chromium in mangrove forests and its health risks to the coastal fishermen folk is not clearly understood. This study investigated the current levels, enrichment, geochemical fractionation, and eco-toxicity on organisms of sediment Chromium from three mangrove forests in southeast China. A health risk assessment for different exposure pathways were also determined with Monte Carlo simulations technique. The results revealed that the concentration of sediment Chromium ranged from 30.75 mg kg−1 to 99.28 mg kg−1. The geochemical fractionations of sediment Chromium were mainly associated with amorphous Fe fraction, crystalline Fe fraction and residual fraction. Notably, 83.12% of samples analyzed in the residual phases of Chromium exceeded the background value of 40.7 mg kg−1. Adverse effect index revealed a considerably negative effect on benthos occurrence in the mangroves. Values of non-carcinogenic risks were below unity at all samples, whereas the cancer risks associated with Cr(VI) exposure via fish consumption at median were close to 1.73 × 10 − 5 . A sensitivity analysis indicated that sediment Cr(VI) concentration and exposure frequency were the most relevant variables in the risk model. As the first attempt to provide information on the human health risks of sediment Chromium in mangrove forests in China, findings from this study can help track potential adverse effects and avoid risks from sediment Chromium. • Chromium were mainly associated with residual phases. • Total carcinogenic risk of Cr(VI) followed the order of CR fish > CR oral > CR derm. • Cr(VI) concentration and exposure frequency were the most influential parameter in calculating CR fish. [ABSTRACT FROM AUTHOR]

Understanding bioavailable metal behaviour in situ is critical for pollution evaluation and contaminant management in mangrove wetland. Here, the diffusive gradients in thin films technique (DGT) was used for characterizing the (bio)available portions of Cr, Zn, Pb, Cu, Fe and Mn in two mangrove wetlands affected by industrial waste discharges (Jiulong Estuary) and domestic discharges (Zhangjiang Estuary), in Fujian Province, China. In addition, fluorescence excitation emission matrices-parallel factor analysis (EEM-PARAFAC) was applied for characterizing the occurrence and behaviour of dissolved organic matter (DOM) in soil solution, as well as their feasibility for assessing behaviours of metals. The results demonstrated that the combination of DGT and EEM, which are well suitable for studying DOM impacted metal behaviors in mangrove sediments. Discharge of difference wastewater into the mangrove wetlands of Jiulong and Zhangjiang Estuaries, gave rise to the DGT-labile metal concentration of Zn > Cu > Cr > Pb and Zn > Cr > Pb > Cu, respectively. A variety of humic-like fluorescent components was characterized here, providing valuable insights into the chemical composition of DOM in rhizosphere and bulk sediment. Terrestrial humic-like compounds indicated a different binding affinity for heavy metals in mangrove sediments. These findings are useful for the future understanding of the metal speciation and molecular binding mechanisms in such mangrove wetlands. Image 1 • DGT was combined with EEM-PARAFAC method to study metal behaviour. • Humic-like substances were found higher in rhizosphere for metal binding. • Humic substances played a key role in controlling the binding of metals. • Mobility and speciation of metals were related to DOM composition. [ABSTRACT FROM AUTHOR]