Yufen Zhang

Use of a nonnegative constrained principal component regression chemical mass balance model to study the contributions of nearly collinear sources.

In this study, a nonnegative constrained principal component regression chemical mass balance (NCPCRCMB) model was used to solve the near collinearity problem among source profiles for source apportionment. The NCPCRCMB model added the principle component regression route into the CMB model iteration. The model was tested with the synthetic data sets, which involved contributions from eleven actual sources, with a serious near collinearity problem among them. The actual source profiles were randomly perturbed and then applied to create the synthetic receptor. The resulting synthetic receptor concentrations were also randomly perturbed to simulate measurement errors. The synthetic receptors were separately apportioned by CMB and NCPCRCMB model. The result showed that source contributions estimated by the NCPCRCMB model were much closer to the true values than those estimated by the CMB model. Next, five real ambient data sets from five cities in China were analyzed using the NCPCRCMB model to test the model practicability. Reasonable results were obtained in all cases. It is shown that the NCPCRCMB model has an advantage over the traditional CMB model when dealing with near collinearity problems in source apportionment studies.

Vertical characteristics of levels and potential sources of water-soluble ions in PM10 in a Chinese megacity

To investigate the vertical characteristics of ions in PM10 as well as the contributions and possible locations of their sources, eight water-soluble ions were measured at four heights simultaneously along a meteorological tower in Tianjin, China. The total ion concentrations showed a general decreasing trend with increasing height, ranging from 64.94μgm(-3) at 10m to 44.56μgm(-3) at 220m. NH4(+), SO4(2-) and NO3(-) showed higher height-to-height correlations. In addition, relationships between ions are discussed using Pearson correlation coefficients and hierarchical clustering analysis (HCA), which implied that, for each height, the correlations among NH4(+), SO4(2-) and NO3(-) were higher. Finally, sources were identified qualitatively by the ratio of certain ions and quantitatively by principal component analysis/multiple linear regression (PCA/MLR) and positive matrix factorisation (PMF). Secondary sources played a dominant role for PM10 and water-soluble ions at four heights and became more important at greater heights (the percentage contributions were 43.04-66.41% for four heights by PCA/MLR and 46.93-67.62% by PMF). Then, the redistributed concentration field (RCF) combined with PCA/MLR and PMF was applied, which indicated the high potential source regions. The vertical characteristics of the levels, relationships, source contributions and locations would support the effective management of the water-soluble ions in particulate matter.

Long-term variation of the levels, compositions and sources of size-resolved particulate matter in a megacity in China.

To investigate the long-term trends and variations of the levels, compositions, size distribution and sources of particulate matter (PM), long-term monitoring campaigns of PM10 and PM2.5 were performed in a megacity in China (Chengdu) during the period from 2009 to 2011. The average concentration of PM10 was 172.01±89.80 μg/m(3) and that of PM2.5 was 103.15±59.83 μg/m(3), with an average PM2.5/PM10 of 0.60. Enrichments of the important species indicated that the fractions of crustal elements were higher in PM10 than those in PM2.5, while the abundance of organic carbon (OC) and secondary ions was enriched in the fine PM. Quantitative source apportionments of both PM10 and PM2.5 were performed by PMF. PM10 and PM2.5 in Chengdu were influenced by similar source categories, and their percentage contributions were in the same order: crustal dust was the highest contributor, followed by vehicular exhaust, secondary sulfate, secondary nitrate and cement dust. Crustal dust and cement dust contributed a higher percentage to PM10 than to PM2.5, while vehicular exhaust and secondary particles provided higher percentage contributions to PM2.5. In addition, PMF-HCA was performed to investigate the characteristics of the sources of the clustered samples, identifying three periods: crustal dust dominant-period, secondary sulfate dominant-period and comprehensive source influenced-period. Planting, reduction of precursors, and banning high-emission vehicles should be implemented to control crustal dust, secondary particles and vehicular exhaust in Chengdu. Furthermore, the size-resolved and the period-resolved control would be more effective.

Heavy metals in urban ambient PM10 and soil background in eight cities around China

The ambient PM10 and background soil samples were collected and analyzed with ICP-AES in eight cities around China to investigate the levels of ten heavy metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb). The mean concentrations of ten heavy metals in PM10 of the eight cities of China followed the order of Zn > Pb > Mn > Cu > Ni > Cr > Co > V. The metals in the ambient PM10 and soil were compared in each city to evaluate the heavy metal mass fraction from anthropogenic sources in ambient air. The CD values in these cities were all above 0.2, indicating that the ingredients spectrums of PM10 and soil vary markedly. Most heavy metals were enriched in PM10, except Fe and Ti. The results showed that almost all the cities suffer important heavy metal pollution from anthropogenic sources. The eight cities were also grouped according to their similarity in heavy metals of ambient PM10 by cluster analysis to investigate the relationship between the heavy metals and the pollution sources of each city. The conclusion was that the eight cities were divided into three clusters which had similar industrial type and economy scale: the first cluster consisted of Shenzhen, Wuxi, and Guiyang; followed by Jinan and Zhengzhou as the second grouping; and the third group had Taiyuan, Urumqi, and Luoyang.

Vertical characteristics of PM2.5 during the heating season in Tianjin, China

In this study, PM2.5 samples were collected at four heights (10m, 40m, 120m and 220m) at a meteorological tower in the daytime and nighttime during the heating season in Tianjin, China. The vertical variation and diurnal variability of the concentrations of PM2.5 and main chemical compositions were analyzed in clear days and heavy pollution days. Generally, mass concentrations of PM2.5 and the chemical compositions showed a decreasing trend with increasing height, while mass percentages of SO4(2-), NO3(-) and OC showed an increasing trend with increasing height. Concentrations of ion species and carbon compound in PM2.5 samples in the daytime were higher than those collected at night, which was due to intense human activities and suitable meteorological condition in the daytime. The ratios of NO3(-)/SO4(2-) and OC/EC were also considered, and we have observed that their levels on heavy pollution days were higher than those on clear days. In addition, source apportionments were identified quantitatively using the CMB-iteration model. The results indicated that contributions of secondary ion species increased with increasing height, while contributions of other pollutant sources decreased, and contributions of vehicle exhaust were relatively high on clear days.

Source apportionment and a novel approach of estimating regional contributions to ambient PM2.5 in Haikou, China ☆

A novel approach was developed to estimate regional contributions to ambient PM2.5 in Haikou, China. In this paper, the investigation was divided into two main steps. The first step: analysing the characteristics of the chemical compositions of ambient PM2.5, as well as the source profiles, and then conducting source apportionments by using the CMB and CMB-Iteration models. The second step: the development of estimation approaches for regional contributions in terms of local features of Haikou and the results of source apportionment, and estimating regional contributions to ambient PM2.5 in Haikou by this new approach. The results indicate that secondary sulphate, resuspended dust and vehicle exhaust were the major sources of ambient PM2.5 in Haikou, contributing 9.9-21.4%, 10.1-19.0% and 10.5-20.2%, respectively. Regional contributions to ambient PM2.5 in Haikou in spring, autumn and winter were 22.5%, 11.6% and 32.5%, respectively. The regional contribution in summer was assumed to be zero according to the better atmospheric quality and assumptions of this new estimation approach. The higher regional contribution in winter might be mainly attributable to the transport of polluted air originating in mainland China, especially from the north, where coal is burned for heating in winter.

Vertical characteristics and source identification of FM10 in Tianjin

Ambient PM10 (particulate matter with a diameter less than 10 microm) concentrations were measured on a 255 meter tower in Tianjin, China. The samples were collected at four vertical levels (10, 40, 120 and 220 m). Vertical characteristics for PM10 samples were studied. The results showed that the concentrations of PM10 and constituent species had a negative correlation with the sampling height. The highest concentrations of PM10 and species were obtained at the 10 m level, and the lowest concentrations were measured at the 220 m level. For the fractions of species to total mass, SO4(2-) and NO3- had higher values (fraction) at greater height; while Ca had a higher fraction at lower height. Possible source categories for the PM10 ambient dataset were identified by the principal component analysis method. The possible source categories included crustal dust, vehicles, cement dust, and incineration as well as secondary sulfate and nitrate sources. Analysis of meteorological factors on PM10 concentrations indicated that wind speed and inversion may be the main factors contributing to different concentrations of PM10 at different heights.

Atmospheric metallic and arsenic pollution at an offshore drilling platform in the Bo Sea: A health risk assessment for the workers.

To investigate the ambient metal pollution at the offshore drilling platform in the Bo Sea, which few studies have focused on, PM2.5 samples were collected and ten heavy metals, as well as As, were analyzed. High concentration levels of metals were observed, and the heavy metal pollution was quite serious compared to air quality standards and other marine areas. Back trajectories and wind dependent and PCA analyses showed that the marine sources included ship traffic emissions and corrosive stainless steels from the equipment at the platform as well as industrial emissions from stainless steel production and coal combustion sources, which were transported from the surrounding mainland. Both contributed greatly to the ambient metallic particles at the offshore platform. The Hazard Index values of the metals, which were much less than 1, the Carcinogenic Risk data, which were lower than the EPAs acceptable range, and the fact that the metal concentrations did not the exceed the permissible exposure limits of OSHA, indicated that the health risks from the ambient metallic particles for the oil-drilling workers were not significant.

Freshwater toxic cyanobacteria induced DNA damage in apple (Malus pumila), rape (Brassica napus) and rice (Oryza sativa)

Cyanobacteria in freshwater ecosystems can present a harmful effect on growth and development of plants through irrigation with contaminated water. In this study, the effects of microcystins (MCs)-containing cyanobacteria extract (CE) on DNA damage of apple, rape and rice were investigated to explore the phytotoxic mechanism of MCs through DNA fragmentation and RAPD analysis. Determination of DNA fragmentation by fluorescent dye DAPI showed that significant DNA damage was observed in rice seedlings after exposure to CE while DNA fragmentation in rape seedlings and apple cultures did not differ significantly between treatment and control groups. Qualitative characterization of genomic DNA fragmentation by agarose gel electrophoresis supported the quantitative determination using DAPI. The main changes in RAPD profiles of rape seedlings following exposure of lower doses of CE were variation in band intensity for the primers F03 and S01, while higher doses of CE caused loss of normal bands and appearance of new bands except band intensity changes. The data presented here demonstrate that DNA damage in plants occurs following exposure of microcystins, and the polymorphic RAPDs may be used as an investigation tool for environmental toxicology and as a useful biomarker for the detection of genotoxic effects of microcystins on plants.

Construction of poplar (Populus tremula) chromosome 1-specific DNA library by using a microdissection technique

A method for single-chromosome microdissection and microcloning was established in forest plants using poplar (Populus tremula) as a model. By use of meristematic cell division in root tip and the wall degradation hypotonic method, well-spread poplar metaphase chromosome spreads showing low contamination were quickly prepared and fitted for chromosome microdissection. An individual chromosome 1 was microdissected from the metaphase spreads of poplar root-tip cells with a fine glass needle controlled by a micromanipulator. The dissected chromosome was amplified in vitro by theSau3A linker adaptor-mediated PCR technique, by which 200- to 3000-bp smear DNA fragments were obtained. Southern hybridization results showed that the PCR products from the single poplar chromosome were homogeneous with poplar genomic DNA, indicating that DNA from the single chromosome has been successfully amplified. Next, the second-round PCR products from the single chromosome 1 were cloned into T-easy vectors to generate a DNA library of the chromosome 1. About 3×105 recombinant clones were obtained. Evaluation based on 160 randomly selected clones showed that the sizes of the cloned inserts varied from 230–2200 bp, with an average of 800 bp. Therefore, this research suggests that microdissection and microcloning of single small chromosomes in forest plants is feasible.