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Huang X.,Sun Yat Sen University | Huang X.,Guangdong Provincial Key Laboratory for Environmental Pollution Control and Remediation Technology | Qiu R.,Sun Yat Sen University | Qiu R.,Guangdong Provincial Key Laboratory for Environmental Pollution Control and Remediation Technology | And 2 more authors.
Atmospheric Research | Year: 2011

In this study, 24-h PM2.5 samples were collected using Harvard Honeycomb denuder/filter-pack system during different seasons in 2006 and 2007 at an urban site in Guangzhou, China. The particles collected in this study were generally acidic (average strong acidity ([H+]) ̃70nmol m-3). Interestingly, aerosol sulfate was not fully neutralized in the ammonia-rich atmosphere (NH3̃30ppb) and even when NH4 +]/[SO4 2-] was larger than 2. Consequently, strong acidity ([H+]) as high as 170nmol m-3 was observed in these samples. The kinetic rate of neutralization of acidity (acidic sulfate) by ambient ammonia was significantly higher than the rate of formation of ammonium nitrate involving HNO3 and NH3 for [NH4 +]/[SO4 2-]≤1.5 and much lower for NH4 +]/[SO4 2-]>1.5. Therefore, higher nitrate principally formed via homogeneous gas phase reactions involving ammonia and nitric acid were observed for [NH4 +]/[SO4 2-]>1.5. However, little nitrate, probably formed via heterogeneous processes e.g. reaction of HNO3 with sea salt or crustal species, was observed for [NH4 +]/[SO4 2-]≤1.5. These demonstrate a clear transition in the pathways of ambient ammonia to form aerosol ammonium at [NH4 +]/[SO4 2-]=1.5 and evidently explain the observed high acidity due to the unneutralized sulfate in the ammonium-rich aerosol (NH4 +]/[SO4 2-]>1.5). In fact, the measured acidity was almost similar to the excess acid defined as the acid that remains at [NH4 +]/[SO4 2-]=1.5 due to the un-neutralized fraction of sulfate ([H+]=0.5[SO4 2-]). The presence of high excess acid and ammonium nitrate significantly lowered the deliquescence relative humidity of ammonium sulfate (from 80% to 40%) in the ammonium-rich samples. © 2010 Elsevier B.V.

Zhou X.,Sun Yat Sen University | Qiu R.,Sun Yat Sen University | Qiu R.,Guangdong Provincial Key Laboratory for Environmental Pollution Control and Remediation Technology | Li Q.,Sun Yat Sen University | And 4 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2010

Concentrations of heavy metals and caloric values as well as their correlation relationship in two populations of Zn hyperaccumulator Potentilla griffithii var. velutina grown in two different sites, Beichang and Paomaping which located in Jinding Pb/Zn mining area, Yunnan Province, were analyzed. The results showed that in Beichang population, Zn concentration (mg kg-1 of dry weight) reached 6217.05 in leaves, 7679. 86 in leafstalks and 4455.44 in roots and it was 3.2, 2.4 and 2.2 times of Paomaping population, respectively; Similarly, Cd concentration in Beichang population was 170.17, 242.51 and 244.45 mg kg" in leaves, leafstalks and roots, respectively, which was 3.0, 2.2 and 1.9 folds as much as those in Paomaping population, respectively. However, Pb concentration ( mg kg-1, DW) in Paomaping population which got 1042. 49 in leaves, 829. 27 in leafstalks and 2621. 39 in roots were a little higher than those in Beichang population. Data showed that the concentration of Zn, Pb and Cd in both Beichang and Paomaping population was related to the concentration of heavy metals in soil. There was no significant difference in capacity of heavy metal translocation and bioaccumulation between these two populations. Both of them showed the same heavy metals translocation capacities which followed by the order of Zn > Cd > Pb. These two populations had no significant difference in ash content and ash-free caloric values in plant tissues. Ash content in roots accounted for smallest part in whole plant, which was less than 6%. Whereas leaves showed the highest caloric values in whole plant, which ash-free caloric value was up to 19.03 and 19.57 kj g-1 in Beichang and Paomaping population, respectively. In addition, energy storage of P. griffithii var. velutina was facilitated by iron and manganese.

Yu F.,Sun Yat Sen University | Yu F.,Guangxi Normal University | Tang Y.,Sun Yat Sen University | Tang Y.,Guangdong Provincial Key Laboratory for Environmental Pollution Control and Remediation Technology | And 6 more authors.
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2010

The effects of cadmium (Cd) on various enzymatic antioxidants and non-enzymatic antioxidants in Arabis paniculata Franch were studied. A. paniculata, a newly identified multi-metal hyperaccumulator, was grown in soils with various Cd concentrations (0, 10, 20, 40, 80, 160 and 240 mg · kg-1) for 135 days. Plant leaves were analyzed for contents of glutathione (GSH), phytochelatins (PCs) and total acid soluble SH, chlorophyll, malondialdehyde (MDA), cysteine, proline and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). The results showed that the plant biomass, Cd content, bioaccumulation factor and translocation factor increased, while the chlorophyll content and SOD activities decreased as the soil Cd concentrations rose. The activities of enzymatic antioxidants (POD, CAT and APX) and the contents of MDA increased at soil Cd concentration below 40 mg · kg-1 and then decreased after this. The contents of GSH, PCs and SH rose with Cd concentration.compared to the control, the contents of GSH, PCs and SH increased by 92.7%, 70.2% and 143.4% respectively at a soil Cd concentration of 240 mg · kg-1. The results indicated that both enzymatic and non-enzymatic antioxidants play significant roles in Cd detoxification in this plant.

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