Effects of combined soil amendments on Cd accumulation, translocation and food safety in rice: a field study in southern China.

Excessive Cd content and high Cd/Zn ratio in rice grains threaten human health. To study the reduction effects of combined soil amendments on Cd content and Cd/Zn ratio in rice planting in soils with different Cd contamination levels, we conducted field trials in three regions of Hunan province, China. Six field treatments were designed in each study area, including control (CK), lime alone (L), lime combined with sepiolite (LS), phosphate fertilizer (LP), organic fertilizer (LO) and phosphate fertilizer + organic fertilizer (LPO). The application of the combined amendments reduced the Cd content in rice grains to less than the Food Health Standard of China (0.2 mg/kg) and the Cd/Zn ratio to less than the safety threshold of 0.015. The average reduction rates of grain Cd content under the combined treatments among the three regions increased with the increase in Cd content in the soil. Meanwhile, the amendments also decreased the soil available Cd and Zn concentration significantly. The LO had the highest efficiency on decreasing Cd content in rice grains among these amendments, which is ranged from 44.6% to 52.8% in the three regions compared with CK. Similarly, high reduction rates of Cd/Zn ratio were found in the LO treatment, with an average value of 57.3% among the three regions. The grain Cd contents and Cd/Zn ratios were significantly correlated with the soil available Cd concentrations, plant uptake factor and the straw to rice grain translocation factor (TFgs) (P < 0.05). The results indicated that the combined soil amendments, especially lime combined with organic fertilizer, would be an effective way to control Cd content in rice.

Metagenomic analysis revealed the succession of microbiota and metabolic function in corncob composting for preparation of cultivation medium for Pleurotus ostreatus.

Metagenomic sequencing was used to reveal the dynamic changes in microbiota and the metabolic functions in corncob composting for preparing cultivation medium of Pleurotus ostreatus. Results showed that the changes of physicochemical properties lead to different dominant phylum at different stages of composting. Firmicutes replaced Proteobacteria as the dominant phylum at thermophilic stage. Correlation analysis indicated that the succession of microbiota was significantly affected by the C/N ratio, pH, temperature and organic matters in compost. The changes in community inevitably lead to the differences of metabolic functions. Metabolism analysis indicated that carbohydrate, lipid and amino acid metabolism were relatively higher in thermophilic stage. Conversely, the metabolism of starch, sucrose, galactose, ascorbate was mainly detected in the late stage. The metabolisms of different stages were driven by different microorganisms. Overall, these findings deepened our understanding of metabolic functions, and it is of great value to the metabolomics research of composting system.

Facile in situ formation of a ternary 3D ZnIn2S4-MoS2 microsphere/1D CdS nanorod heterostructure for high-efficiency visible-light photocatalytic H2 production.

To achieve high photocatalytic efficiency, developing heterostructure photocatalysts by integrating two or more semiconductor materials into a well-oriented nanostructure is an effective strategy. Therefore, under visible light irradiation, a novel ternary 3D ZnIn2S4-MoS2 microsphere/1D CdS nanorod (ZIS/MoS2/CdS) photocatalyst with excellent H2 evolution ability was prepared. For this purpose, using the solvothermal method, interfacial contact ZIS/MoS2 microspheres were prepared, and 1D CdS nanorods were closely inserted into the interspace of flower-shaped ZIS/MoS2 microspheres, to generate close contact between ZnIn2S4, MoS2, and CdS. To expedite the production, separation, and transfer of photoinduced electron-hole pairs, this unique ternary heterostructure demonstrated excellent energy level distribution and a dimensional structure. Under the same conditions, the H2 production rate of the component proportion of the 150%-ZIS/10%-MoS2/CdS (150 wt% ZIS and 10 wt% MoS2) photocatalyst reached 7570.4 µmol g-1 h-1, which was ∼39.8 and 69.0 times higher than that achieved using bare ZnIn2S4 and CdS, respectively. Furthermore, the apparent quantum efficiency (AQE) reached 30.38% at 420 nm within 6 h; thus, for designing photocatalysts with a diversiform structure and spatial charge separation, this study provides new tactics.

The isotopomer ratios of N2O in the Shaying River, the upper Huai River network, Eastern China: The significances of mechanisms and productions of N2O in the heavy ammonia polluted rivers.

In order to figure out the effects of nitrogen pollution and dams on N2O production paths in the river systems, the isotopomer ratios in N2O, NH4+ and NO3-, as well as N2 concentrations and physico-chemical characteristics of water and sediments from the Shaying River system, which is the biggest tributary and major NH4+ contributor of the Huai River, were analyzed in the years 2015 and 2016. The results showed that the net productions of N2O (△N2O) in the river were pretty high, ranging from 12.9 to 440 nmol/L. N2O exhibited a narrow range in δ15Nbulk (-0.04 to 13.51‰), nevertheless a wide range in δ18O (22.54 to 59.90‰). Isotopocule diagram and Pearson correlation analysis indicated that isotopomer ratios of N2O were significantly affected by the mixing of N2O from difference production paths, not by N2O reduction. Relative contributions of nitrification and denitrification to N2O in the Shaying river system were deduced from the two end-members model. The contribution of nitrification to gross N2O was 58.5% on average, almost equal to the contribution of denitrification in summer, although denitrification was the dominant N2O source with average contribution of 75.6% in winter. No significant relationship was found either between △N2O and NH4+ or between △N2O and NO3- in the Shaying River. Heavy NO3- and COD loading reduced nitrification and increased the relative contribution of denitrification to N2O in winter. Heavy ammonia pollution caused pH values to decrease apparently, from 7.5 ±â€¯0.3 in July to 6.3 ±â€¯0.1 in December, resulting in denitrification being the dominant source to N2O in winter. Assimilation enhanced by the construction of dams had weakened the contribution of nitrification to N2O in summer in the Shaying River.

Sources and transformations of anthropogenic nitrogen in the highly disturbed Huai River Basin, Eastern China.

Due to serious nitrogen pollution in the Huai River, Eastern China, nitrogenous concentrations and dual stable isotopes (δ15N and δ18O) were measured to ascertain the sources and transformation of nitrogen in the Shaying River, the largest and most polluted tributary of the Huai River during the summer and winter seasons. Total nitrogen (TN), NO3-, and NH4+ were significantly higher in winter, with values of 7.84 ± 3.44 mg L-1, 2.31 ± 0.81 mg L-1, and 3.00 ± 2.24 mg L-1, respectively, while the highest nitrogen compounds occurred in the Jialu River, one of the tributaries of the Shaying River, in both summer and winter. Isotope characteristics of nitrate reveal that manure and sewage were the principal nitrate sources in both summer (62.44 ± 19.66%) and winter (67.33 ± 15.45%), followed by soil organic nitrogen, with 24.94 ± 15.52% in summer and 26.33 ± 9.45% in winter. Values of δ15N-suspended particulate nitrogen (SPN) ranged from 0.78 to 13.51%, revealing that point source from industrial and domestic sewage accounted for the largest input to SPN at most sites, whereas soil organic nitrogen and agricultural fertilizers were found in the Jialu River in both sampling periods. Point sources from septic/manure and household waste were the main contributors to ammonium in most river water samples in both summer and winter; most wastewater discharged into the river was untreated, which was one of the main reasons for the high level of ammonium in winter. Nitrogen pollution and the dams had an effect on N transformation in the river. Significant assimilation of NH4+ and aerobic denitrification competed for NH4+, resulting in the weakness of nitrification in the summer. Denitrification was also an important process of nitrate removal during the summer, whereas nitrification was a key N transformation process in the river in the winter time. To reduce nitrogen pollution and improve water quality, greater effort should be focused on the management of sources from urban input as well as on the improvement in sewage treatment.