Yu-Tu Wang

Characterization of soil dust aerosol in China and its transport and distribution during 2001 ACE-Asia: 1. Network observations

[1] Mass loading, 20 elemental concentrations, and time series of aerosol particles were investigated over the China Dust Storm Research (ChinaDSR) observational network stations from March to May 2001 during the intensive field campaign period of ACE-Asia. Four extensive and several minor dust storm (DS) events were observed. Mass balance calculations showed that 45 - 82% of the observed aerosol mass was attributable to Asian soil dust particles among the sites, in which Ca and Fe contents are enriched to 12% and 6%, respectively, in the Western High-Dust source regions compared with dust aerosols ejected from the Northern High- Dust source regions. For the latter areas, elemental contents exhibited high Si (30%) and low Fe (4%). For all major source areas and depositional regions, aluminium (Al) comprises 7% of Asian dust. Air mass back-trajectory analysis showed that five major transport pathways of Asian dust storms dominated dust transport in China during spring 2001, all of which passed over Beijing. Measurements also suggest that the sand land in northeastern China is a potential source for Asian dust. The size distribution for estimating vertical dust flux was derived from the observed surface dust size distributions in the desert regions. For particle diameters between 0.25 and 16 mum, a lognormal distribution was obtained from averaging observations at various deserts with a mass mean diameter of 4.5 mum and a standard deviation of 1.5. This range of soil dust constitutes about 69% of the total dust loading. The fractions for particles in the size ranges of 16 mum are around 1.7% and 30%, respectively.

Sources of Asian dust and role of climate change versus desertification in Asian dust emission

For long-term variations and elemental signatures of Asian dust aerosol, changes in mass, twenty elemental concentrations over the period 2001～2003 were assessed from five surface-based stations in western, northern, northeast deserts, the Loess Plateau and the coastal areas in China. Together with the back trajectory analyses and visibility observations, the elemental signatures of soil dust aerosol from different air-mass clusters were characterized for the dust storm (DS) and non-dust storm (N-DS)conditions, respectively.……

Preface to special section on East Asian Studies of Tropospheric Aerosols: An International Regional Experiment (EAST‐AIRE)

daily mean surface solar radiation by � 30–40 W m � 2 , but barely changed solar reflection at the top of the atmosphere. Aerosol loading, particle size and composition vary considerably with location and season. The MODIS AOD data from Collection 5 (C5) agree much better with ground data than earlier releases, but considerable discrepancies still exist because of treatments of aerosol SSA and surface albedo. Four methods are proposed/adopted to derive the SSA by means of remote sensing and in situ observation,

Influence of N deficiency and salinity on metal (Pb, Zn and Cu) accumulation and tolerance by Rhizophora stylosa in relation to root anatomy and permeability

Effects of N deficiency and salinity on root anatomy, permeability and metal (Pb, Zn and Cu) translocation and tolerance were investigated using mangrove seedlings of Rhizophora stylosa. The results showed that salt could directly reduce radial oxygen loss (ROL) by stimulation of lignification within exodermis. N deficiency, oppositely, would reduce lignification. Such an alteration in root permeability may also influence metal tolerance by plants. The data indicated that a moderate salinity could stimulate a lignified exodermis that delayed the entry of metals into the roots and thereby contributed to a higher metal tolerance, while N deficiency would aggravate metal toxicity. The results from sand pot trail further confirmed this issue. This study provides a barrier property of the exodermis in dealing with environments. The plasticity of root anatomy is likely an adaptive strategy to regulate the fluxes of gases, nutrients and toxins at root-soil interface.

Seasonal Variation of Water Quality and Phytoplankton Response Patterns in Daya Bay, China

Data collected from 12 stations in Daya Bay in different seasons in 2002 revealed the relation between water quality and phytoplankton response patterns. The results showed that Daya Bay could be divided into wet and dry seasons by multivariate statistical analysis. Principal component analysis indicated that temperature, chlorophyll a and nutrients were important components during the wet season (summer and autumn). The salinity and dissolved oxygen were the main environmental factors in the dry season (winter and spring). According to non-metric multidimensional scaling, there was a shift from the large diatoms in the dry season to the smaller line-chain taxa in the wet season with the condition of a high dissolved inorganic nitrogen and nitrogen to phosphorous concentration ratio. Nutrient changes can thus alter the phytoplankton community composition and biomass, especially near the aquaculture farm areas. There was no evidence of an effect of thermal water from the nearby nuclear power plants on the observed changes in phytoplankton community and biomass in 2002.

Effects of pyrene on antioxidant systems and lipid peroxidation level in mangrove plants, Bruguiera gymnorrhiza

The effects of polycyclic aromatic hydrocarbon (PAH) (pyrene) on superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase, peroxidase, malondialdehyde (MDA) and proline were studied in leaves, stems and roots of Bruguiera gymnorrhiza. The results showed that the responses of enzymatic and non-enzymatic antioxidants varied significantly among the three tissues studied. The activities of antioxidant enzymes in PAH-treated stems and roots fluctuated in different stress levels compared to the controls, while the antioxidant enzymes such as SOD, APX in leaves increased when stressed by PAH with a significant positive relation between PAH and leaf SOD or APX activity. Low PAH treatments could also stimulate proline in leaves and stems. MDA content was obviously accumulated in stems and roots under PAH stress while decreased in leaves, indicating that the increased antioxidant enzymes in leaves may partly alleviate lipid peroxidation. For pollution monitoring purpose, SOD and APX in leaves may be potential biomarkers of PAH pollution in intertidal estuaries.

Distribution characteristics of transparent exopolymer particles in the Pearl River estuary, China

Distribution of Transparent Exopolymer Particles (TEP) in the Pearl River estuary, China, was investigated during two cruises in August 2009 and January 2010. TEPcolor concentrations were 521.5-1727.4 mg Xeq.L-1 (mu g Gum Xanthan equivalent liter(-1)) in August 2009 and 88.7-1586.9 mu g Xeq.L-1 in January 2010, respectively. The size of TEP generally increased in the seaward along the longitudinal section with the dominant size of 2-40 mu m during the cruises. Experimental work suggested that both concentration and size of TEP increased with Ca2+ concentration (from 0.8 mmol L-1 to 10 mmol L-1). In the field study, Ca2+ concentration had a positive correlation with TEPcolor concentration in the surface layer with salinity <16. Decrease of TEP concentration seaward from intermediary salinity was partly due to dilution of seawater as well as enhanced aggregation and sedimentation of TEP via increasing divalent cation concentration. TEP concentration and turbidity maximum coexisted at the tip of salt wedge in the bottom layer during the wet season, and positive correlation between TEP and turbidity was observed in the winter. Relationships between TEP and turbidity suggested the important contribution of TEP aggregation to flocculation and sedimentation of particles in estuaries. Different pattern of TEP during two cruises can be attributed to physical process (i.e., mixing type) in estuaries. These findings indicated that formation and distribution of TEP were largely influenced by interaction between physical and biogeochemical processes in the Pearl River estuary. A conceptual model for TEP formation and distribution in the Pearl River estuary was developed. Citation: Sun, C.-C., Y.-S. Wang, Q. P. Li, W.-Z. Yue, Y.-T. Wang, F.-L. Sun, and Y.-L. Peng (2012), Distribution characteristics of transparent exopolymer particles in the Pearl River estuary, China, J. Geophys. Res., 117, G00N17, doi: 10.1029/2012JG001951.

Different Bz response regions in the nightside magnetosphere after the arrival of an interplanetary shock: Multipoint observations compared with MHD simulations

We present different magnetic field changes in the nightside magnetosphere in response to the interplanetary (IP) shock on 17 December 2007, using multiple spacecraft observations and global MHD simulations. The coexistence of two distinct B-z response regions in the nightside magnetosphere in a single event has been observationally identified for the first time. From the inner magnetosphere to the tail, they are the positive response (B-z increase) and the negative response (B-z decrease). This scenario reasonably agrees with the MHD model prediction. Moreover, the analysis of the response delay time shows that, for the three satellites which observed the negative responses of B-z, the one closest to Earth was the last to respond. This phenomenon can also be understood based on the model prediction that the negative response region develops toward Earth after its formation. In addition, the temporarily enhanced earthward flows in the negative response region, which were suggested to be responsible for the formation of this region by previous model studies, were also supported by the observation. At last, a global view of the B-z response processes in the nightside magnetosphere is presented based on MHD simulations.

Spatial heterogeneity of bacterial community structure in the sediments of the Pearl River estuary

Denaturing gradient gel electrophoresis (DGGE) and multivariate statistical analytical methods were applied to investigate the spatial variation of bacterial community structure in the Pearl River estuary sediment and to address the relationship between microbial community composition and bottom water chemistry in ten different stations. Preliminary results of sequencing analysis of the excised DGGE bands suggested that α-Proteobacteria, γ-Proteobacteria, Acidobacteria and Actinobacteria were the dominant bacterial groups in the Pearl River estuary sediment. Results of multidimensional scaling analysis of these field data suggested that the composition of bacterial communities varied with sampling sites. Finally, canonical correspondence analysis of the data of environmental variables and bacterial community suggested that bacterial community structure was significantly influenced by the change of environmental variables (total phosphorus, nitrite, ammonium, dissolved oxygen, pH and salinity).

Investigation of Spatial and Temporal Trends in Water Quality in Daya Bay, South China Sea

The objective is to identify the spatial and temporal variability of the hydrochemical quality of the water column in a subtropical coastal system, Daya Bay, China. Water samples were collected in four seasons at 12 monitoring sites. The Southeast Asian monsoons, northeasterly from October to the next April and southwesterly from May to September have also an important influence on water quality in Daya Bay. In the spatial pattern, two groups have been identified, with the help of multidimensional scaling analysis and cluster analysis. Cluster I consisted of the sites S3, S8, S10 and S11 in the west and north coastal parts of Daya Bay. Cluster I is mainly related to anthropogenic activities such as fish-farming. Cluster II consisted of the rest of the stations in the center, east and south parts of Daya Bay. Cluster II is mainly related to seawater exchange from South China Sea.