Organic-inorganic composite modifiers enhance restoration potential of Nerium oleander L. to lead-zinc tailing: application of phytoremediation.

Lead-zinc tailings are complex heavy metal solid wastes produced in the mining process. In this study, two kinds of organic-inorganic mixed improvers mushroom residue + calcium carbonate (M + C) and peat soil + calcium carbonate (N + C) were selected. Then, the effect of two improvers and a woody plant, Nerium oleander L., on the combined remediation of lead-zinc tailings was compared, respectively. The results showed that two combined improvers can slightly improve the pH of tailing, significantly increase the activity of phosphatase and catalase, effectively reduce the contents of DTPA-extractable Pb and Zn, and significantly improve the structure of tailing. However, the improvement effect of M + C was better than that of N + C on tailings' physical and chemical properties. Two improvers can reduce the enrichment and the stress degree of Pb and Zn on the N. oleander and increase the accumulation of Pb and Zn while promoting the growth of the N. oleander. The content of Pb and Zn showed the trend of root > stem > leaf under the two improvers, and the content of Zn was basically higher than that of Pb. To sum up, the combination of two modifiers and N. oleander has a good effect on the remediation of lead-zinc tailings, and the remediation effect of M + C was better than N + C.

[Mechanism of Lead-zinc Enrichment and Resistance of Spent Mushroom Compost to Lead-Zinc Slag in Koelreuteria paniculata].

Phytoremediation is an ecological technique for tailing area restoration; adding substrate modifiers can reduce the stress of heavy metals on plants and enhance the restoration efficiency. The woody plant Koelreuteria paniculata was used as a test plant and potted in 100% tailings (S), 90% tailings+5% mushroom residue (SMC)+5% CaCO3 (MS), and natural red soil (RS). The effects of physiological responses and tolerance enrichment effects on Pb and Zn tolerance in K. paniculata under different treatments were investigated to compare the growth morphology, microscopic morphological changes, and microbial diversity changes in each substrate of K. paniculata seedlings. The results showed that compared with the control group S, the MS treatment group could significantly improve the structure and fertility of the tailing substrates; significantly enhance the relevant physiological indicators such as biomass, plant height, and chlorophyll content of K. paniculate; and increase the accumulated heavy metal content in K. paniculata. In the treatment group, the overall physiological indexes of MS compared to RS biomass and plant height were promoted, and the total root length increased up to 69.3%, whereas the average root diameter of RS in the treatment group decreased 118.7% compared to that in the control group S. The MS treatment group showed a 266.67% increase in Pb and Zn residue state, a significant decrease in the weak acid extractable state and oxide-bound state compared to that in the control group S. The heavy metals were less active for plant migration. Furthermore, most of the heavy metals were trapped in the roots of K. paniculata, and the changes in its root conformation indicated its strong adaptability in the face of high Pb stress. Transmission electron microscopy (TEM) analysis showed that the higher concentration of heavy metals in the S control damaged the cell wall structure and caused toxic effects on plant cells. The addition of the modifier effectively alleviated the effects of heavy metal stress on various tissues of K. paniculata, affected the structure of microbial communities, significantly increased microbial richness and diversity, and enhanced the adaptability of K. paniculata to heavy metals and phytoremediation ability.

Lead Responses and Tolerance Mechanisms of Koelreuteria paniculata: A Newly Potential Plant for Sustainable Phytoremediation of Pb-Contaminated Soil.

Phytoremediation could be an alternative strategy for lead (Pb) contamination. K. paniculata has been reported as a newly potential plant for sustainable phytoremediation of Pb-contaminated soil. Physiological indexes, enrichment accumulation characteristics, Pb subcellular distribution and microstructure of K. paniculata were carefully studied at different levels of Pb stress (0-1200 mg/L). The results showed that plant growth increased up to 123.8% and 112.7%, relative to the control group when Pb stress was 200 mg/L and 400 mg/L, respectively. However, the average height and biomass of K. paniculata decrease when the Pb stress continues to increase. In all treatment groups, the accumulation of Pb in plant organs showed a trend of root > stem > leaf, and Pb accumulation reached 81.31%~86.69% in the root. Chlorophyll content and chlorophyll a/b showed a rising trend and then fell with increasing Pb stress. Catalase (CAT) and peroxidase (POD) activity showed a positive trend followed by a negative decline, while superoxide dismutase (SOD) activity significantly increased with increasing levels of Pb exposure stress. Transmission electron microscopy (TEM) showed that Pb accumulates in the inactive metabolic regions (cell walls and vesicles) in roots and stems, which may be the main mechanism for plants to reduce Pb biotoxicity. Fourier transform infrared spectroscopy (FTIR) showed that Pb stress increased the content of intracellular -OH and -COOH functional groups. Through organic acids, polysaccharides, proteins and other compounds bound to Pb, the adaptation and tolerance of K. paniculata to Pb were enhanced. K. paniculata showed good phytoremediation potential and has broad application prospects for heavy metal-contaminated soil.

Degradation of trimethoprim by sulfate radical-based advanced oxidation processes: kinetics, mechanisms, and effects of natural water matrices.

In this study, we investigated the removal efficiency of a broad-spectrum antimicrobial agent trimethoprim (TMP) in a UV-activated persulfate system (UV/PS). The pseudo-first-order reaction kinetic model based on the steady-state hypothesis was used to explain TMP degradation behavior in UV-activated persulfate system. Due to the low quantum yield and molar absorptivity of TMP at 254 nm, the direct photolysis of TMP was slower. Since the free radicals generated by adding H2O2 or PS to the system can react with TMP, the degradation rate was significantly accelerated, and[Formula: see text] played a dominant role in the UV/PS system. [Formula: see text] and [Formula: see text] were determined by the pseudo-first-order reaction kinetic model to be 6.02×109 and 3.88×109 M-1s-1, respectively. The values were consistent with competitive kinetic measurements. The pseudo-first-order reaction kinetics model can predict and explain the effect of PS concentration, natural organic matter, and chloride ion on the TMP degradation in the UV/PS system. The observed pseudo first-order rate constants for TMP degradation (kobs) increased with the persulfate concentration, but it significantly decreased in the presence of NOM and chloride. [Formula: see text] has no effect on the degradation of TMP, while [Formula: see text] promotes the degradation and [Formula: see text] inhibits the degradation. The common transition metal ion (such as Cu2+, Zn2+, and Co2+) in industrial wastewater has a synergistic effect on the TMP degradation in the UV/PS system, but excessive metal ions will lead to a decrease of the degradation rate.

Synthesis and characterization of camphorsulfonyl acetate of cellulose.

Novel cellulose derivatives were prepared from reacting (1R)-(+)-camphor-10-sulfonic chloride (CSC) with cellulose acetate (CA) in acetone and triethylamine. The reaction conditions, including reaction time and reactant molar ratios, were optimized. The structure of the products was confirmed by means of 1H NMR, 13C NMR, FT-IR and elementary analysis. The techniques were also used to determine the degree of the substitution of camphorsulfonyl groups (DSCS). The data calculated from 1H NMR, 13C NMR, percent grafting (G %) and elementary analysis coincided with those from chemical analysis. Compared to cellulose acetate, the cellulose derivatives exhibited decreased thermal stability, improved solubility in organic solvents and enhanced enantioselectivity towards tyrosine isomers. The solubility and enantioselectivity increased with increasing degrees of camphorsulfonyl substitution.