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The mapping of soil total nitrogen (STN) in estuarine areas is important for agricultural management and ecological conservation, but it is complicated due to high landscape fragmentation and complex influencing factors. In this study, a multiple-scale approach was proposed by adopting various predictors covering different aspects of spectral values, ecological indices, geographical position, land cover composition, and landscape fragmentation that represent comprehensive land surface characteristics. The former three aspects were independent of scales, whereas the latter two aspects were scale-dependent predictors. Multiple scales of 100 m, 200 m, 400 m, and 800 m were adopted for STN mapping using different algorithms to achieve the best simulation effect and search for the most suitable scale. Chongming Island, a typical and important estuarine area in China, was selected to demonstrate the approach. A partial least square regression method using a leave-one-out cross validation approach achieved the best simulation effect among all the algorithms. The results at the 100 m scale possessed the highest accuracy with a root mean squared error and a mean absolute error of 0.2541 and 0.2119 g/kg, respectively. In contrast, the results at the 200 m scale had the second highest accuracy and the lowest uncertainty. The STN possessed a mean value of 1.22 g/kg for the entirety of Chongming Island and it exhibited distinct spatial heterogeneity that was driven by complex influencing factors. Among all of the predictors, the vegetation condition and soil salinity contributed the most to the STN spatial variance. Human activity was the fundamental driving factor of the STN change, and it generally increased the STN because of long-term and island-wide agricultural development. Our approach is highly applicable in estuarine areas, and the scales of 100 m and 200 m can both meet the spatial heterogeneity demand, and thus, these scales are suitable for STN mapping.

The accurate quantification and spatial evaluation of human activity intensity is highly significant for determining the resource and environment carrying capacities of coastal areas. A human interference index (HII) was established in our study based on the minimum and maximum influences of exploitation types, the different ecological conditions within the same exploitation type and the buffer effect of exploitation on adjacent areas. It was characterized by the comprehensive consideration of the ecological features and their spatial heterogeneity. To validate the accuracy and applicability of HII, the Yellow River Delta was selected as the study area, with the years of 1987, 1995, 2005 and 2016 as the temporal scope. Then, to clarify the ecological significance of HII, the relationships of landscape pattern, vegetation net primary productivity (NPP) and soil property with HII were analyzed. The HII of the study area exhibited a continuous increase and spatial heterogeneities from 1987 to 2016. The proportion of the little interference zone kept on decreasing, the proportions of the intermediate, severe and very severe interference zones continued increasing, and the proportion of the mild interference zone initially increased and then slightly decreased. Human interference spread continuously and has been the main driving factor of ecosystem change. The HII is significantly positively correlated with patch density, edge density, and soil salinity, and negatively correlated with NPP and soil moisture content. The HII was proven to possess high accuracy, good applicability and considerable ecological significance. Therefore, it can be widely used in the evaluation of human activity intensity in coastal areas.

Soil microbial biomass (SMB) rapidly responds to the environment and can function as an important indicator for monitoring archipelago ecological vulnerability. An archipelago is featured by distinct and unique gradients between and within islands. The multiple gradient effects on the island ecosystem are worth exploring. We established a multiple gradient system comprising natural, human, and ecological gradients in island and site scales. The natural gradients consist of island area, shape, and distance to mainland in island scale, and terrain and distance to shoreline in site scale; the human gradients include population and exploitation in island scale, and distance to hardened ground in site scale; and the ecological gradients are composed of community type, biomass, biodiversity, and soil physical-chemical properties in site scale. SMB, including SMB carbon (SMBC), SMB nitrogen (SMBN), and SMB phosphorus (SMBP), was used to verify the multiple gradient effects on the island ecosystem, and the northern Miaodao Archipelago in North China was selected as the study area. Results revealed that SMB exhibited distinct spatial heterogeneities. SMBC was sensitive to the natural and human gradients in both scales; SMBN was influenced by parts of natural, human, and ecological gradients in both scales; and SMBP did not show regular changes along the gradients in island scale, yet responded sensitively to the ecological gradients in site scale. The multiple gradient system is unique and fundamental in the spatial heterogeneities of the island ecosystem, and fully revealing the multiple gradient effects is essential for reasonable island conservation and exploitation.

Mesoporous magnetic AMP polyhedric composites mag-AMP (AMP/Fe3O4) with highly efficient Cs+ adsorption capacity has been successfully explored by means of a simple interface-induced co-assembly method at room temperature for the first time. Taking advantage of the mesoporous material and magnetic composite, mag-AMP composites show efficient Cs+ adsorption capability (maximum adsorption capacity, 83.33 mg/g) and reach an equilibrium state within only 5 min. The Langmuir isotherm model fitted better with the adsorption data than Freundlich isotherm model. The fast adsorption process follows pseudo-second-order kinetics. The obtained adsorbent also shows high Cs+-sieving selectivity and could be applied in kinds of solutions even in the strong acidic medium. It could also be used effectively to separate Cs+ from wastewater even with trace (µg/L) concentrations. The removal mechanism of Cs+ for mag-AMP may be the joint action of both chemisorption (NH4+-exchange) and physisorption due to the weak van der waals forces. The adsorbent was inlaid with Fe3O4 NPs which make it easily recovered from polluted solution with magnetic separation. More importantly, the synthesis of mag-AMP is simple and low-cost with environmental friendly raw. Thus, the adsorbent of mag-AMP has extensive applicability for the removal of Cs+ from nuclear wastewater.

The increased production and environmental release of graphene nanoparticles has raised concerns about its environmental impact, but the effects of graphene on living organisms at the metabolic level remain unknown. In this study, we used matrix assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI)-based untargeted metabolomics to investigate the metabolic response of juvenile earthworms (Eisenia fetida) to graphene exposure in soil tests for the first time. Our results reveal that graphene-exposure significantly disturbs earthworm metabolome, and graphene toxicity on earthworm shows non-concentration-dependent effect. Alanine, phenylalanine, proline, glutamate, arginine, histidine, maltose, glucose, malate, succinate, myo-inositol, and spermidine were successfully screened as significantly change compounds in earthworms for the exposure of graphene. The heterogeneous distributions of these metabolites in earthworm were also clearly imaged by MALDI-MSI. Our MSI results fully showed that the metabolite expression levels in juvenile earthworms significantly changed (up-/down-regulation) after exposure to graphene nanoparticles. This work improves our understanding of graphene nanoparticle toxicity to juvenile earthworms and also enables the continued progression of MALDI-MSI-based metabolomics as an emerging, reliable, and rapid ecotoxicological tool for assessing contaminant toxicity.

Land surface temperature (LST) is an important indicator of resource and environment changes in coastal wetlands and exhibits considerable spatiotemporal variations under multiple influences of intensive land–sea interaction and various human activities. Revealing the multi-temporal characteristics of LST and its relationships with normalized difference vegetation index (NDVI) and soil moisture content (MC) in coastal wetlands is important for identifying the LST variations under complex factors, the heat effects of different human exploitations, and the corresponding changes in vegetation and soil water conditions. The Yellow River Delta, a typical and important coastal wetland in China, was selected to demonstrate the study. Remote sensing and field investigation served as the data source, and the LST spatiotemporal patterns and their intrinsic correlations with NDVI and MC in the last 30 years and across different seasons were analyzed. Results indicated that LST spatial distributions varied in different years and seasons. In 1987, LST was low along the Yellow River and high in alongshore areas; in 2016, LST was distinctly low in most of the alongshore areas and high in urban and industrial areas. Across seasons, LST differences between alongshore and inner areas were more distinct in spring that in the other seasons, and LST in urban and industrial areas was especially higher than that in other areas in summer. Among different land covers, salt pond generated cool island effect, whereas urban and industrial areas generated heat island effect. Significant correlations were observed between LST and NDVI at regional scale and among LST, NDVI, and MC at site scale, and their relationships varied in different land cover types across different times. The changes in shorelines, land covers, and vegetation and soil conditions jointly determined the LST spatiotemporal patterns, and human activity has been the main driving factor.

Uninhabited islands serve as a natural and unique laboratory for the study of soil fertility under varying natural conditions and potential anthropogenic influences, and how the soil fertility spatially varies and which factor determines the spatial variance remain to be studied. In this study, a total of 15 uninhabited islands in Miaodao Archipelago, a typical archipelago in northern China, were selected to demonstrate the study. The soil fertility was represented by seven soil factors and a composite index, namely, soil fertility indicator (SFI). Different environmental factors that covered natural and anthropogenic aspects were identified at island and local scales, and the spatial pattern of soil fertility responding to the environmental factors was analyzed. Then, the influences of different environmental factors on the spatial variances of soil fertility at the dual scales were quantified. Results revealed that the soils in the study area had considerably higher values of total carbon, total nitrogen, organic matter, available phosphorus, and available potassium compared with the soils on other China’s islands, the recognized standards, and the national and regional mean values, indicating the extremely high fertility. Great spatial differences in the soil fertility were observed among different islands and sampling sites. At island scale, the island isolation, which was represented by the distance to the inhabited islands and the mainland (DTI), determined the spatial variance of soil fertility. The SFI distinctly increased with the increase in DTI, which could be explained partly by the isolation from human activities and the vegetation condition at island scale, and partly by the cross-scale influence from altitude (Al). At local scale, Shannon-Wiener index (H’), Al, slope (Sl), and distance to the shoreline (DTS) showed clear positive correlations with SFI. The Al and DTS determined the spatial variance of soil fertility under the cross-scale influences from island area and DTI, while H’ and Sl didn’t involve cross-scale influences.

Biodegradation, a widely used treatment for petroleum-pollution seawater, except for its effective degradation, the degradation performance and restoration advantages are also worth studying. In this paper, petroleum-degrading bacteria (P1) with biosurfactant-producing bacteria (B2) were used to perform bioaugmentation. The degradation performance and restoration advantages during bioaugmentation were analyzed by UV spectrophotometry and high-throughput sequencing. The results indicated the degradation rate of diesel by bioaugmentation was 71.86 % in 45 days which exceed 38 % to that without bioaugmentation. In addition, the bacterial community of seawater altered after diesel exposure, especially the species of Pseudoalteromonas and Candidatus palagibacter. During bioaugmentation, Shannon index increased from 1.91 to 2.74, and bacterial community diversity of seawater recovered after a period of time.

Immobilized bioremediation technology is widely used in treating oil-contaminated seas, but changes of bacterial community during treatment were rarely known. In this study, two diesel-degrading strains were embedded in straw-alginate beads to form immobilized cells. Diesel degradation properties and morphological characteristics of the immobilized cells were obtained by gas chromatography–mass spectrometry (GC–MS) and scanning electron microscope (SEM). Bacterial community structure was observed by high-throughput sequencing. The results indicated that C11~C17 was more degraded by immobilized cells, and straw-alginate beads had appropriate pore structure. Higher bacterial diversity was observed in the bioremediated seawater. Pseudoalteromonas (26.41%), became the most dominant species after oil spills, and Thalassospira was enriched to 25.89% after bioremediation. Concentration of oil degradation related genes was predicted to be higher in the bioremediated seawater. Hence, immobilized cells in straw-alginate beads were suitable for degradation diesel. This study was expected to improve the actual repair effect of oil spills.

Mapping soil salinity in coastal wetlands is important for revealing the spatiotemporal characteristics of soil salinization but has proved difficult due to complex influencing factors. An improved comprehensive land surface factor system (ICLSFS) was established based on remote sensing for mapping soil salinity in coastal wetlands. The ICLSFS comprised six classes of predictors, namely, spectral value, salinity index, vegetation index, heat and moisture index, spatial location, and land cover. The Yellow River Delta, a typical coastal wetland in North China, served as the study area to demonstrate the ICLSFS in different seasons. Results revealed the high accuracy and low uncertainty of the ICLSFS methods, and partial least squares regression achieved the highest accuracy. The root mean squared error was lowest in winter of all seasons when the soils were bare in North China. The easily-accessed data provided by remote sensing and the repeatability of simulation process render ICLSFS highly applicable in soil salinity mapping in different coastal wetlands. The mean values of soil salinity in the study area were 8.00, 7.53, 7.83, and 6.90 g/kg in spring, summer, autumn, and winter, respectively. Soil salinity exhibited distinct spatial heterogeneity and was high in shoreline areas, and low in the central part of the study area along the Yellow River. In different land cover types, salterns possessed the highest soil salinity, whereas wetland vegetation and farmland had low soil salinities. The ICLSFS was proven to possess high accuracy, low uncertainty, and good applicability, and the accuracy differed across seasons and was the highest in winter. The spatiotemporal characteristics of soil salinity were influenced by natural and anthropogenic factors. Human activities generally aggravated the soil salinization by saltern constructions, saline water irrigation, and groundwater use, while countermeasures to mitigate the soil salinization have achieved good effects in recent years.

Five types of biochars prepared from four crop straws and one wood shaving at 600 °C were characterized, and their sorption to Cd(II) were determined to investigate the differences in capacity to function as sorbents to heavy metals. Surface areas and pore volumes of the biochars were inversely correlated to the lignin content of raw biomass. The biochars derived from crop straws displayed more developed pore structure than wood char due to the higher lignin content of wood. Sorption capacity of the biochars to Cd(II) followed the order of corn straw>cotton straw>wheat straw>rice straw>poplar shaving, which was not strictly consistent with the surface area of the chars. The surface characteristics of chars before and after Cd(II) sorption were investigated with scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy, which suggested that the higher sorption of Cd(II) on corn straw chars was mainly attributed to cation exchange, surface precipitation of carbonate, and surface complexation with oxygen-containing groups. This study indicated that crop straw biochars exhibit distinct sorption capacities to heavy metals due to various surface characteristics, and thus the sorption efficiency should be carefully evaluated specific to target contaminant.

Information on the effects of continual burial by sediment on seedling survival and morphological growth in coastal marsh remains scarce. A greenhouse experiment was conducted to determine the effects of continual burial on seedling mortality, growth and dry mass allocation of Suaeda salsa in the coastal marsh of the Yellow River estuary. The seeds were planted at 0.5 cm depth in plastic pots filled with unsterilized sediment on May 5, 2012. A depth of 8 cm was chosen as the maximum of continual burial according to the sedimentary rate (6-7 cm) in the coastal marsh at seedling stage. Two weeks after emergence, seedlings were artificially buried to depths of 0 (DO, no burial), 33% (D33, burial of 1 mm d(-1)), 67% (067, burial of 2 mm d(-1)), 100% (D100, burial of 3 mm d(-1)) and 133% (D133, burial of 4 mm d(-1)) of their mean height, with 20 days in total. Results showed that seedling height, stem and taproot diameter, number of branch, hypocotyl and taproot length, and dry mass were significantly affected by burial depth (p < 0.05). No seedlings died in the four burial treatments. Seedling heights in the D33 and 067 treatments were higher than those of the other treatments, indicating that shallow and moderate burials exhibited greater stimulation to seedling growth. Although stem diameter, number and length of branch, and dry mass of seedlings were stimulated in the four burials, the greatest stimulatory effect on stem diameter was observed in the D100 treatment while that on number and length of branch and dry mass occurred in the D67 treatment. With increasing burial depth (D67, D100 and 0133), seedling taproot diameter and length decreased while hypocotyl length increased, reflecting that hypocotyl elongation might occur at the expense of development of the root system. The responses of morphological traits and dry mass allocation of S. salsa seedlings to the burial treatments indicated that they might have a special strategy to tolerate the continual burial in the coastal marsh of the Yellow River estuary. The use of thin-layer burial (2 mm d(-1)) to promote seedling vigor in degraded S. salsa marsh was feasible, and our study provided valuable information for the restoration of S. salsa marsh during seedling growth. (C) 2014 Elsevier B.V. All rights reserved.