[Distribution, Sources, and Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Tributary Waters of the Lower Reaches of the Yangtze River, China].

The lower reaches of the Yangtze River are a typical gathering place of chemical industrial parks in China. Polycyclic aromatic hydrocarbons (PAHs) emitted in the production process of chemical enterprises enter the tributary water body through atmospheric deposition and surface runoff, and finally merge into the Yangtze River. In this study, the distribution characteristics, source analysis, and ecological risk assessment of PAHs in a series of typical water samples collected in the tributary waters of the Yangtze River were studied. PAH monomers in the samples were mainly low-ring. The total concentration of PAHs was in the range of 37.27 to 285.88 ng·L-1 with a mean value of 78.31 ng·L-1, while the monomer concentration of PAHs ranged from 0 to 61.35 ng·L-1. The lowest detection rate was benzo[k] fluoranthene and benzo[a] pyrene at 75%. As a toxic PAH monomer, the concentration of benzo[a] pyrene ranged from 0 to 11.08 ng·L-1. According to "Water Quality Standards for Drinking Water Sources (CJ 3020-1993)" of China, the concentration of benzo[a] pyrene in a water sample (S12) located near Wuxi City exceeded the limit of drinking water standards (10 ng·L-1). Compared with the total concentration of PAHs in rivers in some typical regions of the world, the concentration of PAHs in this study was generally at low to moderate levels. According to the source analysis results of the ratio method and principal component analysis, the concentration of PAHs in water was mainly affected by fossil combustion, automobile exhaust, and chemical emissions. To assess the potential ecosystem risk of PAHs in the investigated area, the risk quotient (RQ) was used. In addition to the DBA monomer, the relative quantities (RQs) (replication) of the remaining monomers were greater than 1, and the RQ (MPCs) values in all the monomers were less than 1, indicating that the ecological risk of water samples was at a medium level. From the perspective of long-term environmental exposure, appropriate control measures should be considered to prevent further pollution. The results can provide reference for PAH risk assessment and pollution control of chemical industrial parks in the lower reaches of the Yangtze River.

Ligno(hemi)cellulolytic Enzyme Profiles during the Developmental Cycle of the Royal Oyster Medicinal Mushroom Pleurotus eryngii (Agaricomycetes) Grown on Supplemented Agri-Wastes.

We have determined the production profiles of major ligno(hemi)cellulolytic enzymes at different stages of the mushroom development cycle during industrial scale cultivation of Pleurotus eryngii on supplemented agri-wastes. Endo-1,4-ß-glucanase, cellobiohydrolase and endoxylanase levels remained relatively low during substrate colonization, increased sharply when small fruit bodies appeared, and peaked at maturation. ß-Glucosidase and ß-xylosidase levels decreased when substrate colonization was complete, increased with the appearance of small fruit bodies and primordia, respectively, and reached maxima at maturation. Laccase peaked along with substrate colonization but, after falling sharply in the upper substrate layers, remained relatively low until postinduction. Levels increased slightly when primordia appeared, fell to minimal values during the small and mature fruit body stages, and increased again postharvest. Manganese peroxidase (Mn-P) exhibited a similar pattern initially but high enzyme levels also coincided with primordia formation. Laccase and Mn-P activity patterns were compatible with a lignin-degradation function associated with substrate colonization and, in the former case, a putative role in fruit body morphogenesis. Based on the relatively low levels of polysaccharidases recorded during the initial stages of substrate colonization, we conclude that reducing sugar levels in noncolonized substrate were adequate for sustainable vegetative growth at that stage. We further conclude that the increase in enzyme production later in the developmental cycle was consistent with the replenishment of depleted reducing sugar from cellulose in the growth substrate to levels required for fruit body formation. These data provide new information describing combined temporal and spatial enzyme production profiles throughout the mushroom development cycle under a set of conditions used in industrial scale production.