Biochar application on paddy and purple soils in southern China: soil carbon and biotic activity.

Soil carbon reserves are the largest terrestrial carbon pools. Common agricultural practices, such as high fertilization rates and intensive crop rotation, have led to global-scale environmental changes, including decreased soil organic matter, lower carbon/nitrogen ratios and disruption of soil carbon pools. These changes have resulted in a decrease in soil microbial activity, severe reduction in soil fertility and transformation of soil nutrients, thereby causing soil nutrient imbalance, which seriously affects crop production. In this study, 16S rDNA-based analysis and static chamber-gas chromatography were used to elucidate the effects of continuous application of straw biochar on soil carbon pools and the soil microbial environments of two typical soil types (purple and paddy soils) in southern China. Application of biochar (1) improved the soil carbon pool and its activity, (2) significantly promoted the release of soil CO2 and (3) improved the soil carbon environment. Soil carbon content was closely correlated with the abundance of organisms belonging to two orders, Lactobacillales and Bacteroidales, and, more specifically, to the genus Lactococcus. These results suggest that biochar affects the soil carbon environment and soil microorganism abundance, which in turn may improve the soil carbon pool.

Risk assessment, spatial distribution, and source apportionment of heavy metals in Chinese surface soils from a typically tobacco cultivated area.

The heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in the surface soils of tobacco (Nicotiana tabacum L.) fields in Jiangxi Province were analyzed, and the mean heavy metal concentrations were 3.55, 0.19, 25.89, 14.96, 0.25, 10.89, 27.80, and 44.00 mg/kg, respectively. Spatial distribution analysis showed that the highest concentrations were recorded in the north-western, south-western, and mid-eastern parts of the study area. The index of geo-accumulation and pollution index indicated modest enrichment with Cd and Hg, which were the only two metals posing a potentially high ecological risk to the local agricultural environment. The health risk assessment showed no considerable non-carcinogenic or carcinogenic risks for children and adults from these elements. The principal component analysis (PCA) and cluster analysis (CA) found that the variations in the Cr and Ni concentrations were largely on account of the soil parent rocks, but the As, Cd, Cu, and Hg variations in the soil were largely owing to agricultural practices of years. However, the main factor influencing Pb and Zn was atmospheric deposition.

Determination of nicotine in tobacco products based on mussel-inspired reduced graphene oxide-supported gold nanoparticles.

Polydopamine functionalized reduced graphene oxide-gold nanoparticle (PDA-RGO/Au) nanocomposites were successfully prepared by a simple and mild procedure. The PDA-RGO/Au nanocomposite is successfully formed in an aqueous buffer solution (pH 8.5) without using any reducing agent. FTIR confirmed the successful coating of PDA and informed the reduction of the surface functional groups of GO. The formation of reduced GO and Au NPs was further evidenced by UV-Vis and X-ray diffraction spectroscopy. This method is environmentally friendly and highly beneficial for the mass production of graphene-noble metal based nanocomposite. The as prepared PDA-RGO/Au nanocomposite could greatly enhance the electrochemical oxidation of nicotine. We fabricated an electrochemical nicotine sensor based on the prepared PDA-RGO/Au nanocomposite. The proposed nicotine sensor showed a wide detection range from 0.05 to 500 µM with a low detection limit of 0.015 µM. Moreover, the proposed nicotine sensor was also successfully applied for determination nicotine content in tobacco products.

[Effects of potassium application rate and its supplemental proportion on dry matter accumulation and potassium absorption of flue-cured tobacco].

A field trial with flue-cured tobacco conducted on a red paddy soil showed that the dry matter accumulation in the tobacco reached a peak in 50-60 days after transplanting, but was lower within 30 days or over 80 days after transplanting. The dry matter accumulation was increased with increasing K application rate and its supplemental proportion. The K content in the tobacco got its peak in 30-50 days after transplanting, and then went down, with the K content at maturing stage being as half as that in the peak period. The K content of the tobacco in each growth stage was obviously higher with 315 kg x hm(-2) K application than with 225 kg x hm(-2) K application. At maturing stage, the dry matter and K contents in the tobacco decreased with 225 kg x hm(-2) K application, but increased with 315 kg x hm(-2) K application, and the K content was higher with 70% K supplemental proportion than with 50% and 30% K supplemental proportion.