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Dredging is used worldwide to remove polluted sediments from water bodies. However, the dredging efficacy remains hard to identify. Here, we studied the efficacy of dredging engineering as a means to remove Cu, Cd, and Pb from polluted lake sediments, after six years of completion. Dissolved metals and DGT-labile metals were quantified in the non-dredged and post-dredged sediments by high-resolution dialysis (HR-Peeper) and diffusive gradients (DGT) in thin films techniques. April and July measurements showed that dredging was effectively remediate the polluted sediments. The dissolved Pb, Cd, and Cu contents decreased up to 30%, 44%, and 26%, and the DGT-labile contents decreased up to 51%, 27%, and 33% compared with the contents in the non-dredged zone. Dredging was thus proven efficient in decreasing the labile metal fractions, increasing the capacity of available solids to bind metals, and slowing the leaching of metals from available solids in the post-dredged sediments. In October and January, the dredging efficacy was counteracted by the decomposition of algae, which increased the dissolved and DGT-labile metal concentrations in the post-dredged zone.

Antimony (Sb) mobilization in sediments and its impact on water quality remained to be studied. In this study, high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) technique were used to measure soluble Sb and labile Sb in sediment-overlying water profiles for a full year in a eutrophic region of Lake Taihu. Results showed that the highest mean concentrations of soluble Sb in overlying water (11.27 and 6.99 μg/L) appeared in December 2016 and January 2017, due to oxidation of Sb(III) to Sb(V) by Mn and Fe oxides, all of which exceeded the surface or drinking water limits set by China, United States and European Union. From April to November 2016, the concentrations of soluble Sb remained low with small monthly fluctuations and mean values ranging from 1.79 to 2.93 μg/L. This was attributed to the predominance of insoluble Sb(III) in sediments under anoxic conditions. The concentration of soluble Sb was slightly higher in summer than in autumn, due to the complexation of Sb(III) with DOM, as shown under anaerobic incubation. The mobility of inorganic Sb in sediments was mostly determined by the transition between Sb(III) and Sb(V), with Sb pollution in bottom water during winter being of concern.

In situ sediment remediation using modified clay has become increasingly popular in aquatic ecosystem management. In this study, two modified clays, Phoslock® and modified zeolite, were used together to co-manage nitrogen and phosphorus loading from a polluted river sediment and intermittent aeration was used as an aid for this remediation. After 120 days of core incubation, results indicated that the two clays alone cannot effectively control all the total and soluble nitrogen and phosphorus concentrations in the overlying water all the time. However, the combined use of clays with intermittent aeration can effectively reduce the nutrient concentrations throughout the experiment. Sediment phosphate flux can be largely inhibited solely by clays or when combined with aeration. Meanwhile, the ammonium flux can only be inhibited effectively for 60 days and is not statically different from control after 120 days. Surprisingly, intensive bioturbation can create a vertical movement of the applied clays in sediment with time, which enhances the phosphorus and nitrogen retention capacity of the subsurface sediment. Phosphorus fractionation analysis indicated that around 50% of mobile phosphorus was reduced in a 4–6 cm sediment layer after 120 days. In contrast, the extractable ammonium and nitrate content in treated sediment increased 2–3 times in this layer. The short-term bioturbation experiment confirmed that bioturbation did not have a large effect on P control efficiency of the clay-treated sediment. Conversely, bioturbation can enhance ammonium release from sediment and the following gradual burial effect can have a negative effect on nitrogen removal from overlying water over time. These results indicate that intensive bioturbation should be considered in polluted river sediment remediation.

Rice straw (RS) was utilized to produce biogas, and its biogas residues (BR) were studied on different degradation time. When rice straw was digested, much biogas was produced with average 50% methane. In anaerobic condition, non-fiber contents were mainly digested in the initial 10 days. Meanwhile, the surface of rice straw fibers became rough and its onset decomposition temperature also rose from 170 °C to 210 °C. Cellulose and hemicellulose were digested from 10 days to 30 days, and it determined that the cellulose crystallinity declined from 44.9% to 40.1% and hydroxyl groups was also seen to decrease, which conduces to the reduction of polarity and hydroscopicity. However, lignin was hardly digested in the whole anaerobic process. Inevitably, lignin was accumulated to contribute to the thermal stability and mechanical properties of rice straw fibers. Furthermore, rice straw/low-density polyethylene (RS/LDPE) and biogas residues/low-density polyethylene (BR/LDPE) composites were prepared. Compared with RS/LDPE composites, BR/LDPE composites showed obviously better tensile and flexural properties. Consequently, biogas residues of rice straw have better chemical and physical properties than the undigested rice straw.

Degradation behavior of methyl orange and direct blue 6 azo dyes catalyzed by Fe76Si9B10P5 amorphous powders and graphene oxide (GO) addition composites has been investigated. The results revealed that the Fe76Si9B10P5 amorphous powders are more effective to degrade azo dyes than the commercial Fe powders with the activity energies of 24.2 kJ mol−1 and 20.4 kJ mol−1 for the degradation of methyl orange and direct blue 6 azo dye solutions. The addition of GO into the amorphous powders further improves the degradation activity, accompanied with lower activation energies of 18.3 kJ mol−1 and 16.7 kJ mol−1. High degradation performance of Fe-Si-B-P amorphous powders was attributed to the amorphous structure in metastable state and the existence of metalloids which are beneficial to the formation of a surface layer with high activity. The addition of GO accelerates the degradation process due to its high surface area and the existence of large number of functional groups.

Herein, novel and versatile electrochemical aptasensors were constructed on a self-supported nanoporous gold (np-Au) microelectrode, integrating with an exonuclease III (Exo III) induced signal amplification strategy. Self-supported np-Au microelectrode with 3D bicontinuous nanoporous structures possesses tremendously large specific area, clean surface, high stability and biocompatibility, bringing about significant advantages in both molecular recognition and signal response. As paradigms, two analytes of bisphenol A (BPA) and ochratoxin A (OTA) were selected to demonstrate the superiority and versatility of designed aptasensors. Trace amounts of mDNA (associated with BPA or OTA concentration) hybridized with cDNA strands assembled on np-Au microelectrode, activating the cleavage reaction with Exo III. Thus, cDNA was digested and mDNA was released to undergo a new hybridization and cleavage cycle. Finally, residual cDNA strands were recognized by methylene blue labelled rDNA/AuNPs with the assistance of hDNA to generate the electrochemical signals, which were used to quantitatively monitor targets. Under the optimized conditions, prepared aptasensors exhibited wide linear ranges (25pg/mL to 2ng/mL for BPA, 10pg/mL to 5ng/mL for OTA) with ultralow detection limits (10pg/mL for BPA, 5pg/mL for OTA), excellent selectivity and stability, and reliable detection in real samples. This work opens a new horizon for constructing promising electrochemical aptasensors for environmental monitoring, medical diagnostics and food safety.

Modified clays are being increasingly used as P-inactivation agents for lake eutrophic control. However, the interaction of P with these material amended sediments still remain unclear. This study investigates the P sorption and supply from the thermally treated calcium-rich attapulgite amended eutrophic lake sediments as well as the ecological safety of material addition. The results indicated that P sorption on material amended sediment can be well fitted by a modified Langmuir model. Material addition can greatly enhance the P sorption capacity of lake sediment and lower the zero equilibrium P concentration (EPC0), which can turn lake sediment from a source to a pool. P sorption on raw and material amended sediment generally decreases with an increase of the water pH value. But material amended sediment still can adsorb a large amount of P even in very alkaline conditions resulting from algal blooms. Furthermore, P sorption on amended lake sediment was less influenced by NO3− and HCO3− than by SO42− to a moderate degree and by SiO3− to a much larger degree. The results of diffusive gradients in thin films (DGT) measurement indicated the ability of P supply from lake sediment was largely inhibited by material addition. This was due to sediment mobile P had been transformed into stable Ca-P. A toxicity study indicated that material additions can increase pH value in lake sediment and can cause a toxic effect on benthic organisms when a large addition of material is involved, but this would be greatly attenuated in the field. The results of this study indicated that thermally treated calcium-rich attapulgite has the potential to be used as a P-inactivation agent for lake eutrophication control.

Fruit cracking is a phenomenon involving the splitting of the fruit peel, which causes considerable economic losses. The objective of the present study was to determine whether a nordihydroguaiaretic acid (NDGA) treatment can decrease the incidence of grape berry cracking in the cracking-susceptible Vitis vinifera cultivar ‘Aishen Meigui’. The results indicated that NDGA can significantly decrease the fruit-cracking rate. There may be two reasons for this observation. Firstly, the NDGA treatment decreased the synthesis of endogenous abscisic acid (ABA) as well as the soluble sugar and total soluble solid contents, which ultimately lowered the osmotic pressure, water absorption capacity, and peel turgor pressure. Second, the decrease in the endogenous ABA content also decreased the pectin methylesterase and polygalacturonase activities, delayed the degradation of pectin, increased the peel protopectin content, enhanced the peel mechanical properties, and increased the resistance to fruit cracking.

This study examined lead (Pb) pollution in algae- and macrophytes-dominated sediments, using diffusive gradient in thin films (DGT) and dialysis (HR-Peeper) techniques. Lead pollution varied by season in the two different ecotype sediments. In the algae-dominated zone, the highest concentrations of DGT-labile Pb and dissolved Pb occurred in April and July, respectively. The reductive dissolution of Fe/Mn oxides was identified as an important driver for Pb releases in April and July. This was supported by the decrease of the reducible fraction of Pb in sediments during those sampling periods. Furthermore, dissolved organic matter (DOM) complexation with Pb in sediments also significantly increased the dissolved Pb concentrations in July. The Pb-DOM complexes accounted for 95% of the total chemical species of Pb in pore water, calculated by Visual MINTEQ 3.1 model. Low concentrations of labile and dissolved Pb were observed in October and January; these resulted from the formation of Pb-sulfide precipitates and adsorption by Fe/Mn oxides. It was supported by the high rate of Pb(HS)2 precipitation (saturation index > 0), at 36%, in October samples and the high reducible fraction of Pb in sediments in January samples. In the macrophytes-dominated region, there was a decrease of labile and dissolved Pb concentrations in April and July. It is likely because of the uptake of Pb by submerged macrophyte roots and the Fe/Mn plaques in the root surface. High concentrations of labile and dissolved Pb were observed in October and January, likely resulting from the DOM complexation with Pb in sediments. This was supported by the fact that the Pb-DOM complexes accounted for 90% and 87% of the total chemical species of Pb in October and January, respectively.

The continuous release of nutrients from sediment is a major barrier to the remediation of black odorous rivers. This study used a long-term laboratory incubation experiment to investigate the effectiveness of sediment dredging, intermittent aeration, and in situ inactivation with modified clays to reduce the internal loading of sediment from a seriously polluted river. The results indicated that intermittent aeration and in situ inactivation were effective in reducing the TN and NH4+ concentrations in the water column. However, sediment dredging did not consistently reduce the TN and NH4+ concentrations in the water column. In contrast, the three methods were all effective in controlling the TP and PO43− concentrations in the water column. Except for dredging, >30% of NH4+ and 40% of PO43− fluxes from sediment were reduced when compared with a control sample after 120 days of remediation. Dredging induced a significant release of NH4+ from sediment. Dredging and aeration made nearly no change to the amount of extractable nitrogen in the sediment. However, inactivation may increase sediment-extractable ammonium in deep sediment layers with time due to vertical transportation of clay by intensive bioturbation. Dredging is the most effective way to reduce surface mobile phosphorus over time while the transported clays can reduce a large percentage of the mobile phosphorus in deeper sediment. The relative abundance of Nitrospira in the surface sediment increased significantly with each remediation measure, creating favorable conditions for the reduction of the ammonium released from sediment. Altogether, the results of this study indicated that clay inactivation is the best method for controlling the internal loading of both phosphorus and nitrogen in seriously polluted river sediment.

Rice straw fibers are potential raw materials that can be used to produce biogas and reinforcing fibers for composites. In order to ascertain the effects of anaerobic digestion on the structural properties of the fibers, the structure of fibrous residuals with different digestion time, including 0, 10, 20, and 30 days, were investigated. The normalized biogas production volume was 224 mL/g volatile solid of substrate, of which the methane content was about 50%. Fiber detergent analyses of the straw before and after 10 days digestion indicated that the cellulose levels increased from 34.3% to 41.3%, and cellulose crystallinity index ranged from 44.9% to 49.9%, respectively. After the rice straw had been digested for 30 days, the cellulose and hemicelluloses of the rice straw were partially degraded; the crystallinity index of the cellulose decreased from 44.9% to 40.1% based on XRD analyses, and the amount of hydroxyl groups were observed to decrease based on FT-IR analyses. Consequently, the polarity and hygroscopicity of the rice straw fibers were speculated to be lowered based on these observed changes. Furthermore, the relative amount of lignin in the straw residuals increased as digestion time increased, which increased the thermal stability of the resulting fibers. As a result of anaerobic digestion, the properties of the rice straw fibers for their use in plastic composites were enhanced.

An alternative and efficient approach for the synthesis of N-alkylated amides from nitriles and alcohols was proposed and accomplished. By the combination of [(IPr)Au(NTf2)] (IPr = 1,3-bis(diisopropylphenyl)imidazol-2-ylidene) and [Cp*IrCl2]2 (Cp* = η5-pentamethylcyclopentadienyl), a series of nitriles were first hydrated to give amides, in which the resulting amides were further N-alkylated with a variety of alcohols as alkylating agents to afford N-alkylated amides with good to excellent yields. Compared with previous methods for the synthesis of N-alkylated amides from nitriles and alcohols as starting materials, this protocol could be accomplished with high atom economy under more environmentally benign conditions.

To improve the compatibility between rice straw and reinforcing polymers, rice straw (RS) was pretreated by an anaerobic process, and its biogas residues (BR) were acetylated with acetic anhydride (AA) to prepare acetylated biogas residues (ABR). The optimum conditions of acetylation were determined by orthogonal experiments. When acetylation was performed at 140 °C with 10 mL AA/g BR and 0.08 g catalyst/g BR, the maximum weight gain rate (WGR) obtained was 23.7%. Fourier transform infrared (FTIR) analysis showed that many hydroxyl groups were displaced by acetoxy groups. Scanning electron microscopy (SEM) showed that many defects of BR were filled by the acetylation, and an ester layer was formed over the BR surface. However, the lower crystallinity of ABR than the BR and RS affected the mechanical properties of acetylated biogas residue/low density polyethylene (ABR/LDEP) composite. Interestingly, the BR and ABR showed higher onset decomposition temperature, but they exhibited faster decomposition rates because of the lower crystallinity of BR and ABR. Furthermore, the mechanical properties of the RS/LDEP, BR/LDEP, and ABR/LDEP composites were analyzed. Compared with RS/LDEP composites, the BR/LDEP and ABR/LDEP composites showed obviously better tensile and flexural properties. Consequently, rice straw fibers attained excellent compatibility with non-polar polymers.

The objective of this study was to clarify the effects of calcium treatments on the anthocyanin accumulation of ‘Manicure Finger’ grape berries. Calcium treatments increased the calcium contents and enhanced the calmodulin activities in grapevine leaves and berries, upregulated the expression of the sugar transporter genes SUC12 and SUC27 in leaves, promoted the transport of photosynthetic products to berries, and increased the expression of anthocyanin biosynthesis-related genes in the grape berry skin. These results indicate that the application of exogenous calcium enhances anthocyanin accumulation in ‘Manicure Finger’ grape berries in the following two ways: (1) calcium promotes the transport of photosynthetic products to berries, thereby providing the basic material required for anthocyanin biosynthesis; (2) calcium induces anthocyanin biosynthesis by regulating the expression of relevant structural and regulatory genes. Our results will help researchers characterize the mechanism responsible for the calcium-mediated promotion of anthocyanin biosynthesis in grapevine and related plant species.

In this study, natural calcium-rich attapulgite (NCAP) was used to develop a low-cost adsorbent for removing fluoride (F−) from contaminated water. The results showed that calcination can dramatically increase the F− sorption capacity of NCAP and that the maximum F− sorption capacity occurred at 700 °C. The sorption of F− on NCAP heated at 700 °C (NCAP700) followed pseudo-second-order kinetics and was described by the Langmuir equilibrium model. The estimated F− sorption capacity was approximately 140.0 mg/g at pH 8.0, which was comparable with the sorption capacities of some nanomaterials. The sorption of F− on NCAP700 performed well at pH values of 7 to 10. In addition, anions such as NO3 − and SO4 2− did not affect fluoride removal, but PO4 3− and HCO3 − moderately influenced fluoride removal. A column study conducted using NCAP700 with a particle size of 0.2–0.5 mm indicated that the adsorbent could effectively purify nearly 200 bed volumes (BV) of water containing 3.0 mg F/l at pH 8.5. The removal of F− from water mainly resulted from the formation of calcium fluoride precipitates and the complexation of fluoride with the –OH group of NCAP700, which was further confirmed by scanning electron microscopy–energy dispersive spectrometry (SEM-EDS) and X-ray photoelectron spectroscopy (XPS).

Nanoporous structures were fabricated from Fe76Si9B10P5 amorphous alloy annealed at 773 K by dealloying in 0.05 M H2SO4 solution, as a result of preferential dissolution of α-Fe grains in form of the micro-coupling cells between α-Fe and cathodic residual phases. Nanoporous Fe-Si-B-P powders exhibit much better degradation performance to methyl orange and direct blue azo dyes compared with gas-atomized Fe76Si9B10P5 amorphous powders and commercial Fe powders. The degradation reaction rate constants of nanoporous powders are almost one order higher than those of the amorphous counterpart powders and Fe powders, accompanying with lower activation energies of 19.5 and 26.8 kJ mol−1 for the degradation reactions of methyl orange and direct blue azo dyes, respectively. The large surface area of the nanoporous structure, and the existence of metalloids as well as residual amorphous phase with high catalytic activity are responsible for the enhanced azo-dyes degradation performance of the nanoporous Fe-Si-B-P powders.