Indoor particle dynamics in a school office: determination of particle concentrations,deposition rates and penetration factors under naturally ventilated conditions

Recently, the problem of indoor particulate matter pollution has received much attention. An increasing number of epidemiological studies show that the concentration of atmospheric particulate matter has a significant effect on human health, even at very low concentrations. Most of these investigations have relied upon outdoor particle concentrations as surrogates of human exposures. However, considering that the concentration distribution of the indoor particulate matter is largely dependent on the extent to which these particles penetrate the building and on the degree of suspension in the indoor air, human exposures to particles of outdoor origin may not be equal to outdoor particle concentration levels. Therefore, it is critical to understand the relationship between the particle concentrations found outdoors and those found in indoor micro-environments. In this study, experiments were conducted using a naturally ventilated office located in Qingdao, China. The indoor and outdoor particle concentrations were measured at the same time using an optical counter with four size ranges. The particle size distribution ranged from 0.3 to 2.5 μm, and the experimental period was from April to September, 2016. Based on the experimental data, the dynamic and mass balance model based on time was used to estimate the penetration rate and deposition rate at air exchange rates of 0.03–0.25 h^?1. The values of the penetration rate and deposition velocity of indoor particles were determined to range from 0.45 to 0.82 h^?1 and 1.71 to 2.82 m/h, respectively. In addition, the particulate pollution exposure in the indoor environment was analyzed to estimate the exposure hazard from indoor particulate matter pollution, which is important for human exposure to particles and associated health effects. The conclusions from this study can serve to provide a better understanding the dynamics and behaviors of airborne particle entering into buildings. And they will also highlight effective methods to reduce exposure to particles in office buildings.     

Estimating the removal of atmospheric particulate pollution by the urban tree canopy in Beijing北大核心CSCD

Urban green space, particularly the tree canopy, plays an important role in potential mitigation against atmospheric particulate pollution and protecting human health. In this study, current and future air particulate matter [including total suspended particulate (TSP), particulate matter 10 (PM10), and particulate matter 2.5 (PM2.5)] removal by the urban tree canopy of Beijing was estimated. A modeling approach was used based on the distributed measurement evaluation and a modified version. The urban tree canopy of Beijing, including mostly Platycladus sp., Pinus sp., Quercus sp., Robinia pseudoacacia, and economic forests, currently removes about 8.33 million kg/a air particulates, in which TSP accounted for 4.51 million kg/a, PM10 accounted for 2.74 million kg/a, and PM2.5 accounted for 1.08 million kg/a. The study on the removal of air particulates by different aged tree canopies showed that in coniferous trees, the ability to capture air particulates changed in the order of mature and over-mature > near-mature forest > young forest; in broadleaf forest, the ability changed in the order of near-mature forest > mature and over-mature > young forest. For total particulate matter, the biggest contribution was coarse particulates (60.74%); the contribution rate of fine particulates was different owing to different tree species groups. The results suggested that the ability of different trees to capture particles and age of forests varied widely and that suitable trees should be chosen to enhance pollution mitigation for city greening. © 2018 Science Press. All rights reserved.     

Isolation,identification, and the biodegradation characteristics of a benzoylurea insecticides-degrading strain北大核心CSCD

A chlorbenzuron, diflubenzuron, and hexaflumuron-degrading bacterium strain M6, was isolated from the activated sludge of an insecticide factory. The strain was identified as Achromobacter sp. according to an analysis on the 16S rRNA gene sequences, morphological, and physiological characteristics. Strain M6 could degrade more than 91% of 100 mg/L chlorbenzuron, diflubenzuron, and hexaflumuron within 48 hours, which could act as the sole carbon source. Strain M6 showed more chlorbenzuron degradation at a temperature range between 25 and 40 ℃ and a pH range between 6.0 and 8.0. The optimal temperature and the initial pH of medium for chlorbenzuron degradation by strain M6 were 30 ℃ and 7.0, respectively; the maximum chlorbenzuron tolerated concentration of strain M6 was as high as 400 mg/L. Strain M6 hydrolyzed 4-acetaminophenol into a purple-red product. Moreover, an approximately 1.4 kb DNA fragment, which could be expressed into an amidase to degrade amide pesticides, was amplified from the genomic DNA of strain M6. The results preliminarily proved that 3 benzoylurea insecticides could be degraded because of strain M6 hydrolyzing their amide bonds. This study obtained a highly efficient degrading strain and provided new resources and valuable information on benzoylurea insecticide degradation. © 2018 Science Press. All rights reserved.     

Screening and identification of cellulose degrading bacterium Bacillus siamensis BREC-11 with tolerance to furfural北大核心CSCD

Furfural is a toxic metabolic inhibitor that is created during the conversion of lignocellulose to produce fuel, which can retard fermentation and increase production costs. thus, it is important for lignocellulosic conversion that the ability of the strain to resist furfural stress be improved. A cellulose-degrading bacterium BREC-11 with tolerance to furfural was isolated from the intestinal tract of Omphisa fuscidentalis hampson larvae via the addition of furfural in the medium. Based on analyses of morphological observations, physiological and biochemical characterizations, and 16S rDNA sequences, strain BREC-11 was shown to represent a member of the genus Bacillus and was named B. siamensis BREC-11. to study the tolerance concentration of strain BREC-11, a wide range of furfural formaldehyde concentrations were tested and strain BREC-11 was shown to grow in the mineral medium containing furfural up to 3.5 g/L. Cellulase activity of strain BREC-11 was determined at the tolerable concentration of 3.5 g/L furfural after incubation at 30 ℃ and 150 r/min for 2 days. Results indicated that filter paper enzyme, CMC-Na enzyme, and β-glucosidase activity was 0.1 U/mL, 0.21 U/mL, and 0.07 U/mL, respectively. BREC-11 is a cellulose-degrading bacterium with resistance to furfural, which has potential application in future bio-refinery processes. © 2018 Science Press. All rights reserved.     

Effects of planting density on the microclimate of rice population with different panicle-types and its yield components北大核心CSCD

Split-plot field experiments, with variety as the main plot, were designed to analyze the microclimate and character of R498 (curved panicle) and R499 (erect panicle) varieties of rice during the full heading day and on the 20th day after full heading. The planting densities assigned to the subplots were 0.23 m (line spacing) × 0.12 m (hole spacing), 0.27 m × 0.14 m, 0.33 m × 0.17 m, 0.38 m × 0.20 m, and 0.40 m × 0.21 m. The results showed that for all the planting densities, the maximum temperature of R499 increased by 1.52 ℃ on an average during the full heading stage, but decreased by 0.66 ℃ on the 20th day after full heading, in comparison to those of R498. The mean daily light intensities of R498 and R499 in sparse planting (0.38 m × 0.20 m, 0.40 m × 0.21 m) were higher than those of other planting density treatments during the full heading stage, being 43.56% and 16.22% higher, respectively, than that of the lowest daily light intensity. The daily light intensity of R498 was hindered by close planting (0.23 m × 0.12 m, 0.27 m × 0.14 m) while that of R499 was inhibited by sparse planting on the 20th day after the full heading stage. The rates of decrease of vertical light intensity of R498 and R499 in sparse planting were the highest among all the planting density treatments, their rates of decrease being 97.96% and 92.56%, respectively, during the full heading stage, and 94.81% and 91.10%, respectively, on the 20th day after the full heading stage. When the planting density was decreased, the variability of plant height, tiller number, and panicle curvature were greater for R499 than those of R498. The rates of incidence of sheath blight for R498 and R499 in the planting specification of 0.38 m × 0.20 m were 66.67% and 68.89%, respectively, which was the most serious among all the planting density treatments. On increasing the effective spike number and panicle weight, both R498 and R499 produced the highest yields with the planting specification of 0.27 m × 0.14 m, among all the planting density treatments. Even when the density was excessively reduced, the value of yield components did not increase any further. Thus, it is better to plant rice with curved panicles (R498) in a reasonable planting density (neither too close nor too sparse), and to plant rice with erect panicles in a reasonably close planting density. © 2018 Science Press. All rights reserved.     

Isolation,identification, culture conditions,and laccase production of a wild mushroom 'Huaier'北大核心CSCD

In the present study, fruiting bodies of a wild medicinal mushroom, 'Huaier, ' were collected from Populus canadensis in the Beijing Xiangshan Park. The pure culture strain was obtained from fruiting bodies using the tissue isolation method. It was stored and numbered as XS-01. It was systematically classified using morphological and ITS identification. Further studies were focused on mycelia optimum culture conditions and laccase production by liquid fermentation. A 598-bp partial ITS region sequence (GenBank accession number KY93348) was obtained using PCR method. Phylogenetic tree and genetic distance analysis were performed using the MEGA 6.0 software. The present strain possessed the highest homology (100%) with Perenniporia robiniophila, and the genetic distances were 0.000. Based on the ITS sequencing and morphological characteristics of fruiting bodies and mycelia, XS-01 was identified as P. robiniophila. Based on mycelial growth rate and quality, mycelia optimum culture conditions were revealed to be as follows: the optimum carbon sources were starch and maltose, the optimum nitrogen source was yeast extracts, the optimum C/N ratio range was 30/1 - 60/1, the best growth temperature was 32 °C, the optimum pH was 7, and the optimum growth factor was VB1. Further study of Cu2+ on extracellular laccase production revealed that 1.0 mmol/L Cu2+ could significantly enhance the enzyme production, with the highest activity of 417.5 U/mL when cultured for 96 h and an increase ratio of 93.4% to the control. On the other hand, 2.0 mmol/L Cu2+ can markedly decrease the enzyme production laccase activity at 96 h to 79.0 U/mL, which was 36.6% of that of the control. In conclusion, a pure strain of T. robiniophila with high extracellular laccase activity was obtained, suggesting its potential application for artificial cultivation and laccase production. © 2018 Science Press. All rights reserved.     

Plant biomass allocation strategies of the dominant species in an alpine meadow of northwestern Sichuan,China北大核心CSCD

Plant biomass partitioning is an important driver of whole-plant net carbon gain, as biomass allocation could directly affect plant's future growth and reproduction. Alpine meadow in the northwestern Sichuan was impressed by the abundant community structure and species diversity. This study on biomass allocation pattern of different functional types and lifeforms might help understand plant life-history strategy of alpine meadow plants. We investigated 72 dominant herbaceous species for their compartments, biomass, and morphological traits during 2012-2014. These plants were sampled from natural grassland, disturbed grassland, and wintergreen grassland; they belonged to three functional types (grass, sedge, and forb) and two lifeforms (annual and perennial). The scaling relationships between functional traits of these plants were analyzed using Model type II regression method to estimate the parameters of the allometric equations. (1) Biomass allocation proportion of components significantly differed among grasses, sedges, and forbs owing to phylogeny: grasses had the highest stem biomass percentage, sedges had higher root biomass percentage, and forbs had higher leaf biomass percentage, but the scaling relationships were not significantly different, and isometric scaling was noted between biomass components for the three functional types. (2) Moreover, plant lifeforms affected the biomass allocation proportion of components, owing to the shorter or longer turnover rate and investment strategy between annual and perennial species. Annuals allocated more biomass to the stem and reproduction organs, but perennials invested more biomass to the leaves and roots. (3) In addition, plants from different grassland types differed in both biomass and morphology traits. Moreover, forbs from natural grassland and wintergreen grassland had higher leaf and reproductive biomass, but those from disturbed grasslands had higher stem biomass. Our results suggest that the functional type and lifeform decide the inherent scaling relationships between components of plants, but anthropogenic disturbance significantly impacted the quantity of component biomass. This study has important theoretical and practical significance to understand the response of alpine plants to climate change and anthropogenic disturbance as well as to help in the scientific management of alpine meadow. © 2018 Science Press. All rights reserved.     

Effect of soil acidification on yield and quality of tea tree in tea plantations from Anxi county,Fujian Province北大核心CSCD

In order to investigate the effect of tea tree rhizosphere soil acidification on yield and quality of tea tree, the pH value, yield, and quality index of fresh tea leaves of different ages were analyzed, and the correlation between rhizosphere soil acidification and ages, yield, and quality index were studied from nine tea plantations in Anxi county, Fujian Province. The results showed that 37.67% of the nine soils were acidified, and 10.03% of them were suitable for planting tea tree. Furthermore, the results indicated that the age of tea tree was significantly and negatively correlated with the soil pH value, as shown by a decrease in soil pH values associated with an increase in tree age. In addition, the yield of spring and fall crops of tea from these nine plantations were all significantly and positively correlated with the pH value, with correlation coefficients distribution values of 0.912-0.952 and 0.898-0.973, respectively. In addition, quality indices, including polyphenols, theanine, and caffeine for the nine tea plantations were all significantly and positively correlated with their soil pH values, and their correlation coefficient distribution values were 0.897-0.959, 0.908-0.974, and 0.907-0.975, respectively. Above all, as tea tree ages increased, rhizosphere soil acidity was significantly increased, and yield and quality of tea presented a statistically significantly up/down trend. © 2018 Science Press. All rights reserved.     

Effects of early management of Pinus massoniana plantation target trees on soil physicochemical properties and plant diversity北大核心CSCD

In order to provide a theoretical reference for the early management of target trees in the low mountain region of eastern Sichuan, and a theoretical basis for the sustainable management of masson pine (Pinus massoniana) plantations, we chose three different kinds of densities (100 target trees per hectare, 150 target trees per hectare, and 200 target trees per hectare) in a 33-year-old masson pine plantation in the low mountain region of eastern Sichuan. We investigated the change patterns of soil physicochemical properties and plant diversity during the early stage of the management of the target trees. The results showed that compared to the control (CK), the early stage of management of P. massoniana plantation target trees dramatically improved the soil physical properties, the pH value, contents of organic matter, and total phosphorus (P < 0.05); however, the available phosphorus and the available nitrogen varied slightly (P > 0.05). Compared to the control (CK), significant (P < 0.05) differences in the richness index were observed between shrubs and herbs (P < 0.05), and in the shrub layer, the dominant position was replaced by others. Simpson, Shannon, and Pielou indexes of shrubs showed no significant difference in the study (P > 0.05). On the contrary, Simpson, Shannon, and Pielou i ndexes of herbs were significantly lower than those for CK (P < 0.05). There were significant correlations between plant species diversity and soil physicochemical properties such as soil pH, contents of total phosphorus, and the available nitrogen. The early stage of management of P. massoniana plantation target trees significantly improved the plant diversity and soil physicochemical properties. Among all the three different treatments, the density of 150 target trees per hectare had the best effect on the soil physicochemical properties and plant diversity. © 2018 Science Press. All rights reserved.