Positive contributions of the stem to the formation of white tea quality-related metabolites during withering.

Most teas, including white tea, are produced from tender shoots containing both leaf and stem. However, the effect of the stem on white tea quality remains unclear, especially during withering, an essential process. Therefore, this study investigated the withering-induced changes in the leaves and stems of Camellia sinensis cv. 'Fudingdabai' by multi-group analysis. During withering, the levels of catechin and theobromine (i.e., major flavor-related compounds) decreased slightly, mainly in the leaves. The abundance of some proteinaceous amino acids related to fresh taste increased in stems due to increased protein hydrolysis. In addition, changes in biosynthetic pathways caused a decrease in theanine (a major non-proteinaceous amino acid) and an increase in gamma-aminobutyric acid in stems. Terpenes, mainly in the stems, were partially affected by withering. Phenylacetaldehyde, a major contributor to white tea aroma, increased mainly in the stems. These findings reflect the positive contribution of the stem to white tea quality.

Distribution, source, and contamination assessment of heavy metals in surface sediments of the Old Yellow River Estuary in China.

To assess the sources and pollution status of heavy metals, surface sediments from the Old Yellow River estuary were systematically sampled and analyzed to determine the concentrations of seven heavy metals. The Pearson's correlation coefficient, enrichment factor, geoaccumulation index, and principal component analysis were used to distinguish the sources and assess the pollution risk of heavy metals. The results showed that the distributions of Al, Fe, Cu, Pb, Zn, Cr, and As were similar and mainly dominated by fine-grained sediments, whereas the distributions of Cd and Hg were irregular. Al was strongly correlated with Fe, Cu, Pb, Zn, As, and Mz, and positively correlated with Cr. Except for Cr, Cd, and Hg, all the other elements were positively correlated with Mz. Multiple indicators indicated that Cu, Pb, Zn, Cr, and As were mainly derived from natural sources, whereas Hg and Cd were derived from anthropogenic sources.

Heavy metal concentration profiles and pollution assessment in the Jiangsu offshore area, China.

The concentration profiles of various major and trace heavy metals (Cu, Pb, Zn, Cr, Cd, As, Hg, Ni, Li, and Co) were investigated along a 40.1-m-long sediment core in the offshore Jiangsu area of China, to assess their depositional trends and contamination levels. All metals, except Cd, exhibited similar profiles with high average concentrations during the Marine Isotope Stage 2-4 period. The sediment trace-metal concentrations were primarily related to grain size and sediment sources, with almost all heavy metals (except Cd) being positively correlated. Enrichment factors, geoaccumulation indices, and principal component analysis indicated no elemental enrichment or contamination. The high EF and Igeo values of As, Hg, and Li may be related to their background values.

Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Coast, China.

The distribution, sources, and ecological risk assessment of 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the Nantong coast in China were investigated. The results indicated that the total concentrations of the 16 PAHs in the surface sediments from the study area ranged from 1.4 to 87.1ngg-1 dw (mean value 19.9ngg-1 dw), which were generally low compared to the adjacent offshore area and other coastal zones around the world. The selected PAH ratios and the principal components analysis for each site showed that petroleum combustion and petrogenic pollution (mainly caused by petroleum spills) were the dominant PAHs sources in the surface sediments of the coast. The ecological risk assessment indicated that most of the individual PAHs had few negative effects in this area.