Effect of air quality improvement by urban parks on mitigating PM2.5 and its associated heavy metals: A mobile-monitoring field study.

Field mobile monitoring of PM2.5, equipped with a highly accurate device, was performed for two types of urban parks in Taiwan. Measurements were taken in the morning and evening rush hours, on certain weekdays and weekends, every month over a year. We designed six calculation schemes of the rate of PM2.5 mitigation by urban parks to comprehensively compare the average and maximum mitigation effects in relation to the vegetation barriers. The mitigation rate, from the lowest (2.51%) to the highest (35.57%) depended on the calculation schemes. The Taipei Botanical Garden (TBG) with a dense, multilevel forest has a stable PM2.5 mitigation effect and strong ability to improve air quality inside the park under severe PM2.5 pollution. In contrast, Zhonghe No.4 Park (ZHP), an open park with mostly a single-storied stand, has variable PM2.5 mitigation effect, leading to either quick dissipation or accumulation of PM2.5 inside the park. Furthermore, the dry deposition of PM and the associated heavy metals were investigated using camphor trees as bioaccumulators. Dry deposition flux of the leaf-deposited PM2.5 exhibited similar results in ZHP; whereas, noticeable higher results were observed inside TBG. In addition, most of the PM2.5 deposition flux from field estimations were similar to those in i-Tree Eco when considering the loss of mass due to the dissolution through water filtration, indicating that i-Tree Eco may be reliable to model the removal of PM2.5 in the parks in Taiwan. Moreover, we examined nine heavy metals' content in the deposited PM, and most of the detectable elements were significantly higher outside both parks, demonstrating the mitigation effects of urban parks in reducing not only the PM2.5 concentration but also the toxicity of the pollutant. This study provides direct evidence of the important ecosystem services, namely air quality improvement and biomonitoring effect, derived from urban parks.

Dry deposition of particulate matter and its associated soluble ions on five broadleaved species in Taichung, central Taiwan.

Many studies have estimated particulate matter (PM) removal by urban trees using dry deposition models; however, few studies have quantified the accuracy of their results. Thus, this study investigated the dry deposition of PM and its associated soluble ions in five broadleaved species in three districts of Taichung, central Taiwan, through field experiments. The total suspended particulate (TSP) dry deposition flux on leaf surfaces varied with sampling time, site, and tree species. By contrast, single-factor effects were observed for PM10 and PM2.5. The average dry deposition velocities of TSPs, PM10, and PM2.5 were 0.63, 0.062, and 0.028 cm s-1, respectively. Moreover, the dry deposition velocities of sulfate and nitrate were estimated to be 0.186 and 0.194 cm s-1, respectively. A significant relationship was observed between the ambient concentration and the dry deposition flux for all size fractions of PM. By contrast, weak and negative correlations were found between particle deposition velocity and wind speed. The measured PM2.5 dry deposition velocity was approximately equal to the dry deposition velocity obtained with the i-Tree model (0.03 cm s-1), which indicated the promising application potential of i-Tree in Taiwan. Compound and rough leaves, such as leaves of the Taiwan golden-rain tree, intercepted a high amount of PM2.5, whereas the pongam tree, which has thin leaves and wax surfaces, exhibited the lowest TSP interception. Species difference mostly occurred in the dry deposition flux of nitrate rather than sulfate; however, the interception of sulfate by trees revealed the possibility of the long-range transport of air pollutants. The results of this study elucidate the dry deposition of PM and its associated soluble ions in real-world situations.

Thinning Effects on Biomass and Carbon Stock for Young Taiwania Plantations.

Forests play an important role as carbon sinks by sequestrating carbon through photosynthesis. Thinning treatments have large impacts on carbon storage, in addition to strengthening quality and quantity of plantations. This study analyzed the effects of different thinning treatments on carbon stocks in both individual trees and stands of Taiwania (Taiwania cryptomerioides) plantations. Repeated field measurements and allometric equations were used to calculate total C storage and sequestration rates of live trees. The results of this study showed that the total carbon stock of stands with thinning treatments was less than that of the non-thinned stands. The non-thinned 23-year old stands had an estimated carbon stock of 96.8 Mg C ha-1, which is higher than the carbon stock found in either medium- (84.1 Mg C ha-1) or heavily-thinned (74.7 Mg C ha-1) treatment plots of the same age. If the objective of Taiwania plantations was to store large amounts of carbon in the young growth stage, without regard to the initial rate of storage, a better option is no-thinning. However, the medium thinned forests seem to be more promising for carbon sequestration than the no-thinned forests if a longer period is considered.

Evaluation of the antibacterial activity of leaf and twig extracts of stout camphor tree, Cinnamomum kanehirae, and the effects on immunity and disease resistance of white shrimp, Litopenaeus vannamei.

Effects of essential oils and hot-water extracts isolated from leaf and twig of stout camphor tree, Cinnamomum kanehirae on antibacterial activity to pathogen of fish, abalone, marine fish and freshwater prawn, and the white shrimp, Litopenaeus vannamei immunity and disease resistance to Vibrio alginolyticus were carried out in this study. A better antibacterial activity against nine selected pathogen bacteria was recorded in twig essential oil, and the selected pathogens of both Gram-positive bacteria and Gram-negative bacteria were sensitive to the leaf and twig essential oils in the present study. No antibacterial activity was recorded in the hot-water extracts of leaf and twig. In challenge trial, a significant decrease of sensitivity to V. alginolyticus (1 x 10(6) cfu shrimp(-1)) was found in that of shrimp received hot-water extract from twig at the levels of 2 microg g shrimp(-1) compared to control. In addition, the how-water extract of twig in vitro showed greater enhanced effects on phenoloxidase activity, respiratory burst and phagocytosis of white shrimp compared to the hot-water extract of leaf. It is considered that the extracts of stout camphor tree could be a candidate to replace the chemo-therapeutants through the inhibitory effects against the growth of pathogens, and enhanced effects on shrimp immunity and disease resistance.