Microplastic pollution of intertidal mangrove ecosystems is receiving growing attention, and scientists suspect that the microplastic pollution of semi-enclosed seas is significantly different from ...that of other coastal types because of their unique geographical features. However, data on the distributions and characteristics of microplastics in the mangrove sediment of semi-enclosed seas are very limited. This study selected the Maowei Sea, a typical semi-enclosed sea, as its representative study site. The analysis revealed that the microplastic abundances in the river estuaries were much lower than those at the oceanic entrance zones, with values ranging from 520 ± 8 to 940 ± 17 items/kg. Polyethylene (PE)/polypropylene (PP)/polystyrene (PS), white/transparent, and <1 mm were the dominant type, colour, and size of the microplastics, respectively, in the observed mangrove sediments. Moreover, some other factors, including the rhizosphere/non-rhizosphere and the proportion of organic matter, codetermined the distribution and characteristics of microplastics. Specifically: (1) the percentage of colorful microplastics were higher in the rhizosphere due to the microbial activities and (2) positive linear relationships were found between the pore volume (PV) values of the free particulate organic matter (FPOM), occluded particulate organic matter (OPOM) (1.6–2.0 g/cm3 and >2.0 g/cm3), and the abundance of very small microplastics (<1 mm).
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•Microplastics were first detected in the mangrove sediment of the semi-enclosed sea.•Factors determining microplastic contents in estuaries and entrances differed.•Pore structure influenced the microplastic content in mangrove sediment.•Microbial activity in rhizosphere accelerated the microplastics' colour changes.
Fishery activities are an important source of microplastic pollution in coastal areas but have received little attention. The Beibu Gulf, a traditional fishing ground of China and the China-Indo ...Peninsula, was selected in this study, and the focus was on the impacts of fishery activities on the horizontal distribution of microplastics in sediment. The results showed that the dominant contaminants (polypropylene fibers and polyethylene fibers) might originate from the abrasion of fishing gear and contributed to 61.6% of the total abundance of microplastics in surface sediment. The abundance of polypropylene fibers and polyethylene fibers exhibited a strong correlation (R 2 = 0.8586, p = 0.015) with values of fishery yields of different districts, which highlighted the effects of different fishery activities on microplastic contamination in marine sediment. Microplastics could be “hidden” in deep sediment to a depth of 60 cm. The estimated storage of microplastics in deep sediment (185 tons) was 5 times that in surface sediment. The assessment of microplastic storage worldwide might be underestimated because most previous studies only examined surface sediment. The abundance distribution and size distribution of microplastics in the sediment core suggested long-term burial of microplastics in deep sediment. Bioturbation might be responsible for the vertical transport of microplastics, leading to “fresh microplastics” preservation in “old sediment”.
The temporal distribution of organochlorine pesticides (OCPs) was examined in the ²¹⁰Pb dated sediment core from the Beibu Gulf, South China Sea. The total OCPs concentrations were in the range of ...0.93–26.6 ng g⁻¹ dry weight. Dichlorodiphenyltrichloroethanes (DDTs) (0.17–24.8 ng g⁻¹), Hexachlorocyclohexanes (HCHs) (0.04–0.51 ng g⁻¹), Chlordane related compounds (CHLs) (0.22–1.72 ng g⁻¹) and endosulfan (n.d.–0.91 ng g⁻¹) were the predominant compounds. Similar to most Chinese coastal areas, the levels of DDTs in the Beibu Gulf became elevated since the early 1990s, especially since 2000 despite the ban in 1983 in China. This suggests that the concentrations of DDTs were controlled by several processes, such as land reclamation and soil runoff. The isomer ratios of (p,p′-DDE + p,p′-DDD)/p,p′-DDT, p,p′-DDT/DDTs along with construction land expansion indicated that economic activities, land reclamation, soil runoff and the use of DDT-containing antifouling paints might be responsible for the input of DDT. The ratios of α-HCH/γ-HCH (and γ-HCH/HCHs) and trans-chlordane/cis-chlordane (TC/CC) indicated fresh inputs of lindane and chlordane, respectively. In addition, CC was found to be degraded faster than TC under anaerobic conditions in sediments from the Beibu Gulf.
Concentrations, distributions and sources of PAHs were investigated in surface sediments from Lijiang River, South China. The total PAHs concentrations ranged from 160 to 602 ng g
−1
dry weight.The ...total PAHs concentrations from different area descended in the order: middle reach > upper reach > down reach. Based on the PAHs indicators and the surrounding along Lijiang River, PAHs were mainly derived from the burning of coal. The ecological risk assessment suggested that the probability of negative toxic effective caused by PAHs in Lijiang River was lower than 25 %.
Organochlorine pesticides (OCPs) including HCH, DDT, chlordane, endosulfan, and endosulfan sulfate were analyzed in surface soil of the Dayan Cave to investigate their source and concentration levels ...in September 2006. Generally, the data showed that outside soil of the cave had much higher concentrations than inside soil for the most detected OCPs in the cave and both inside soil and outside soil showed much lower concentration levels (basically, the levels of OCPs were less than 0.7 ng/g) than those observed in other regions within and outside China other than TC (ranging from 3.22 to 5.00 ng/g) and CC (ranging from 3.89 to 5.08 ng/g) in the soil outside. The ratios of
α
-/
γ
-HCH ranged from 0.88 to 1.20 in the soil of the cave, together with the averaged percentages of
β
-HCH and
δ
-HCH among the total HCH isomers (accounting for 39.0% and 14.2%, respectively), implied that a historical residue of local technical HCH contamination was likely to be dominant in the soil of the cave. Based on (1) the accordance of TC/CC ratios (ranging from 0.83 to 0.98) between the values observed in the outside soil and the potentially available chlordane products in the markets, and (2) the high concentrations of TC and CC observed in the outside soil, it appeared that the illegal usage of technical chlordane was done in Guilin. The low concentrations of TC (0.02 to 0.56 ng/g) and CC (0.10 to 1.71 ng/g) in the inside soil, together with the significant distinctions of TC/CC ratios between the inside soil (ranging from 0.03 to 0.33) and the outside soil, implied that the chlordane in the inside soil of the cave was a historical residue of local technical chlordane contamination. The similar ratios of DDT isomers (
o
,
p
′
-DDT/
p
,
p
′
-DDT and
p
,
p
′
-DDE+DDD/DDT) between the outside soil and the inside soil of the cave suggested that they may have the similar DDT source. The ratios of
p
,
p
′
-DDE+DDD/DDT (ranging from 3 to 8) indicated that DDT was relatively aged. The values of
o
,
p
′
-DDT/
p
,
p
′
-DDT ratios (ranging from 3 to 7.5 with a mean value of 5.45) were found to be much higher than that of technical DDT, and very similar to that of dicofol products, implied that the primary source of DDT in the soil of the cave was most probably from dicofol-type DDT products. The low concentration levels of endosulfan and the higher levels of metabolite endosulfan sulfate indicated that the residue from historical usage of technical endosulfan was likely to be dominant in the soil of the cave.
Six kinds of metals were measured in soils and plant from the Siding Pb–Zn mineland, South China, to investigate the pollution and restoration technique. The mean Pb, Zn, Fe, Mn, Cu and Cr contents ...in soils were 5,215 ± 642, 13,352 ± 1,242, 24,755 ± 2,475, 438 ± 52, 67 ± 38 and 68 ± 31 mg kg
−1
, respectively. The results revealed the mean contents of Pb and Zn exceeded the third level of China standard of soil (GB15618-1995) for 10.4 and 26.7 times, respectively. The soil of Siding Pb–Zn mineland has heavily been subjected to Pb and Zn pollution. 22 plant species from 13 families were found colonizing. There were great variations of metal contents in plant species with Pb 1.58–1496 mg kg
−1
, Zn 7.56–204,256 mg kg
−1
, Cu not detected (ND)–286 mg kg
−1
, Fe 83–25,972 mg kg
−1
, Mn 1.02–160 mg kg
−1
and Cr ND–152 mg kg
−1
. Of the six metals, Fe content was the highest, followed by Pb and Zn, which were similar to the situation of the soil. The local pioneer species,
Pteris vittata,
was observed a higher accumulation and translocation capability for Pb, which could be chosen as pioneer of phytoremediations to restore Pb/Zn mineland.
Hierarchical nanostructures with tailored component and architectures are attractive for energy‐related applications. Here, the delicate design and construction of hierarchical MoS2/MoP (H‐MoS2/MoP) ...nanorods for the hydrogen evolution reaction (HER) are demonstrated. This multiscale design rationally combines the compositional and structural advantages of MoS2/MoP heterojunction into a hierarchical architecture, which can modulate electronic structure of S, remarkably facilitating the electrocatalytic HER. Benefitting from their unique architecture and electronic structure, the H‐MoS2/MoP nanorods exhibit excellent performance for HER with ultralow overpotential of 92 mV at current density of 10 mA cm−2 in 1 m KOH and high stability. This work not only provides an efficient approach to constructing hierarchical heterojunctions, but also a multiscale strategy for all‐round regulation of the electronic structure and hierarchical morphology of nanomaterials for energy‐related applications.
Nanorod‐like hierarchical MoS2/MoP heterojunctions are synthesized via MoO3 nanorods as the starting sacrificial template. The obtained H‐MoS2/MoP has high stability and excellent HER activity, due to optimized electronic structure of S and decreased free energy of H adsorption.
The asymmetric spinning in the middle-tube is a field that has not yet been thoroughly explored. An approach for this process using generic rollers is first proposed that introduces a novel method ...for forming irregularly shaped tubes suitable for industrial production. This paper delves into the precise forming of the novel spinning process under tool-less controlled axial and radial metal flow conditions, and methodically examines its forming mechanism. Asymmetric tubes with various shape factors are spun via derived roller-path equations, where two roller feeding methods are appropriately designed. The effects of three spinning schemes (Scheme A, Scheme B, and the one using the profile roller) with three forming depths on the shape accuracy and wall thickness distribution, are contrastively examined. The obtained results reveal that the shape accuracy based on the generic roller is enhanced by 14.6% compared to the case of utilizing the profile roller. Additionally, the spun wall thickness distribution based on the generic roller is generally more uniform than that of the using-profile-roller. In the generic-roller working conditions, Scheme A presents a more reasonable forming approach and exhibits a more uniform wall thickness distribution. This reveals the forming mechanism of the middle-tube asymmetric spinning using the generic roller.
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•A novel approach to middle-tube asymmetric spinning via generic rollers is developed.•The asymmetric tubes with different shape parameters are spun by using the derived roller-path equations.•Three spinning schemes are adopted to investigate the forming accuracy and wall thickness distribution of the novel approach.•The shape accuracy and wall thickness uniformity is improved significantly by using the generic roller.•The forming mechanism of asymmetric spinning in the middle-tube via a generic roller is revealed.
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