Zheng Zong

Identification and quantification of shipping emissions in Bohai Rim, China

Rapid development of port and shipbuilding industry in China has badly affected the ambient air quality of coastal zone due to shipping emissions. A total of 60 ambient air samples were collected from background site of Tuoji Island in Bohai Sea strait. The air samples were analyzed for PM2.5, organic carbon (OC), element carbon (EC), inorganic elements, and water-soluble ions. The maximum concentration of PM2.5 was observed during spring (73.6 μg·m(-3)) compared to winter (39.0 μg·m(-3)) with mean of 54.6 μg·m(-3). Back trajectory air mass analysis together with temporal distribution of vanadium (V) showed that V could be the typical tracer of shipping emissions at Tuoji Island. Furthermore, the ratios of vanadium to nickel (V/Ni), vanadium to lead (V/Pb) and vanadium to zinc (V/Zn) also suggest shipping emissions at Tuoji Island. The annual average primary PM2.5 estimate of shipping emissions was 0.65 μg·m(-3) at Tuoji Island, accounting for 2.94% of the total primary PM2.5, with a maximum of 3.16% in summer and a minimum of 2.39% in autumn.

Impact of agricultural waste burning in the Shandong Peninsula on carbonaceous aerosols in the Bohai Rim, China.

A total of 11 5PM2.5 samples were collected for analyzing organic carbon (OC) and elemental carbon (EC) at Tuoji Island (TI), China from November 2011 to December 2012. The results showed that annual arithmetical means of OC and EC concentrations were 3.8 ± 2.7 and 2.2 ± 2.2 μg m(-3), which contributed 8% and 4% of PM2.5 mass concentrations, respectively. High EC concentrations occurred in winter, contributed mainly by EC outflow from the northwest source region, while high OC concentrations were found during spring, attributed largely to biofuel burning in the Shandong Peninsula, and short distance and favorable transport from the peninsula to the TI. Agricultural waste open burning in the peninsula caused the largest variability of OC concentration in summer. Eliminating agricultural field burning in the peninsula can reduce at least one-third of concentration levels and half of northward transport fluxes of OC and EC in Bohai Rim in summer.

Radiocarbon-based impact assessment of open biomass burning on regional carbonaceous aerosols in North China

Samples of total suspended particulates (TSPs) and fine particulate matter (PM2.5) were collected from 29th May to 1st July, 2013 at a regional background site in Bohai Rim, North China. Mass concentrations of particulate matter and carbonaceous species showed a total of 50% and 97% of the measured TSP and PM2.5 levels exceeded the first grade national standard of China, respectively. Daily concentrations of organic carbon (OC) and elemental carbon (EC) were detected 7.3 and 2.5 μg m(-3) in TSP and 5.2 and 2.0 μg m(-3) in PM2.5, which accounted 5.8% and 2.0% of TSP while 5.6% and 2.2% for PM2.5, respectively. The concentrations of OC, EC, TSP and PM2.5 were observed higher in the day time than those in the night time. The observations were associated with the emission variations from anthropogenic activities. Two merged samples representing from south and north source areas were selected for radiocarbon analysis. The radiocarbon measurements showed 74% of water-insoluble OC (WINSOC) and 59% of EC in PM2.5 derived from biomass burning and biogenic sources when the air masses were from south region, and 63% and 48% for the air masses from north, respectively. Combined with backward trajectories and daily burned area, open burning of agricultural wastes was found to be predominating, which was confirmed by the potential source contribution function (PSCF).

First Assessment of NOx Sources at a Regional Background Site in North China Using Isotopic Analysis Linked with Modeling

Nitrogen oxides (NOx, including NO and NO2) play an important role in the formation of atmospheric particles. Thus, NOx emission reduction is critical for improving air quality, especially in severely air-polluted regions (e.g., North China). In this study, the source of NOx was investigated by the isotopic composition (δ15N) of particulate nitrate (p-NO3-) at Beihuangcheng Island (BH), a regional background site in North China. It was found that the δ15N-NO3- (n = 120) values varied between -1.7‰ and +24.0‰ and the δ18O-NO3- values ranged from 49.4‰ to 103.9‰. On the basis of the Bayesian mixing model, 27.78 ± 8.89%, 36.53 ± 6.66%, 22.01 ± 6.92%, and 13.68 ± 3.16% of annual NOx could be attributed to biomass burning, coal combustion, mobile sources, and biogenic soil emissions, respectively. Seasonally, the four sources were similar in spring and fall. Biogenic soil emissions were augmented in summer in association with the hot and rainy weather. Coal combustion increased significantly in winter with other sources showing an obvious decline. This study confirmed that isotope-modeling by δ15N-NO3- is a promising tool for partitioning NOx sources and provides guidance to policymakers with regard to options for NOx reduction in North China.

Combining Positive Matrix Factorization and Radiocarbon Measurements for Source Apportionment of PM 2.5 from a National Background Site in North China

To explore the utility of combining positive matrix factorization (PMF) with radiocarbon (14C) measurements for source apportionment, we applied PM2.5 data collected for 14 months at a national background station in North China to PMF models. The solutions were compared to 14C results of four seasonally averaged samples and three outlier samples. Comparing the most readily interpretable PMF solutions and 14C results revealed that PMF modeling was well able to capture the source patterns of PM2.5 with two and three irrelevant source classifications for the seasonal and outlier samples. The contribution of sources that could not be classified as either fossil or non-fossil sources in the PMF solution, and the errors between the modeled and measured concentrations weakened the effectiveness of the comparison. Based on these two factors, we developed an index for selecting the most suitable 14C measurement samples for combining with the PMF model. Then we examined the potential for coupling PMF modeling and 14C data with a constrained PMF run using the 14C data as a priori information. The restricted run could provide a more reliable solution; however, the PMF model must provide a flexible dialog to input the priori restrictions for executing the constraint simulation.

Assessing on toxic potency of PM2.5-bound polycyclic aromatic hydrocarbons at a national atmospheric background site in North China

A total of 76PM2.5 samples collected at Tuoji Island from November 2011 to January 2013 were used to analyze 15 congeners of polycyclic aromatic hydrocarbons (∑15PAHs) and assess their toxic potency. The average ∑15PAHs was 15.34±8.87ngm-3, ranging from 4.24 to 40.62ngm-3 over the sampling period. BkF, BbF, Phe and BaP were dominant PAH congeners, contributing together 60.64% of the ∑15PAH concentration. The highest monthly ∑15PAHs concentration was in January 2012, followed by the next January, which was closely four times greater than the lowest level occurred in July 2012. Wheat straw burning was responsible for the high PAH concentrations in June 2012. The averaged BaP toxicity equivalent (TEQ-BaP) concentration was 2.70±1.88ngm-3 over the sampling period. BaP and DaA were the largest contributors, which contributed 58.5% and 14.7% of totals, respectively. The high TEQ-BaP and TEQ-BaP value per unit of ∑15PAHs concentration (TEQ-BaP(U)) values occurred in the cold season and the low levels presented in the warm period. The heaviest monthly TEQ-BaP was 5.28±2.84ngm-3, which appeared in January 2012; the lowest value was 0.86±0.33ngm-3, which occurred in July 2012. The potential source contribution function (PSCF) showed the occurrence of the high health risk associated with PAHs in the middle of Liaoning and the south of Shandong Peninsula.

Evidence of Rural and Suburban Sources of Urban Haze Formation in China: A Case Study From the Pearl River Delta Region

Although particulate matter (PM)-driven haze is a common phenomenon in many Chinese cities, studies on the sources of its key components, such as organic carbon (OC) and elemental carbon (EC), are poorly constrained. In this study, PM with aerodynamic diameters less than 10 (PM10), 2.5 (PM2.5), and 1 μm (PM1) were collected at an urban site in the core city of the Pearl River Delta region in summer 2013. The average PM10, PM2.5, and PM1 mass concentrations were 109 ± 28.4, 57.7 ± 15.0, and 50.9 ± 13.2 μg/m3, respectively. A PM-driven haze bloom-decay process was observed from 9 to 14 July and studied based on radiocarbon (14C) and stable nitrogen isotope (15N). The 14C results revealed that 87% of EC and 53% of OC in PM2.5 were derived from fossil sources on a typical summer day (9 July), while these values fell to 79% and 40% on 12 July and 76% and 29% on 13 July, respectively, due to the invasion of nonfossil-enriched air masses from rural/suburban areas. In addition, a 15N-derived model showed that nonfossil sources contributed 5% of NH3 on 9 July, which increased to about 80% on 12 and 13 July. However, the 15N-NO3- values were relatively stable, probably because of the large area of overlap in 15N-NOx from biomass burning and traffic exhaust. To our knowledge, this work is the first study to report both daily 14C and 15N signals in China and identify nonfossil sources from rural/suburban areas as triggers of summer haze.

Flux and source-sink relationship of heavy metals and arsenic in the Bohai Sea, China

This study conducted a field campaign to collect atmospheric deposition samples of heavy metals and arsenic, a metalloid element with typical chemical-physical characteristics (HMA), from 12 sampling sites and water samples from 37 rivers across the Bohai Sea (BS) and North Yellow Sea (NYS) in China. The HMA budgets in the BS and NYS were quantified by a budget model, which was developed based on the HMA inputs from atmospheric deposition and riverine discharge, sequestration to sediment, and interexchange among the BSs four subareas and the NYS. Statistical analyses of 76 deposition samples and 109 water concentration samples showed that atmospheric deposition was a main pathway of Pb entering the BS and NYS, whereas riverine discharge dominated the input of Cr, Cu, Zn, Cd, and As into the marine environment. Modeled results showed that the fractions of HMA in the water bodies compared with their total burdens were 86.6 ± 4.55% in the Liaodong Bay, 60.5 ± 10.5% in the Bohai Bay, 20.9 ± 9.05% in the Laizhou Bay, 95.1 ± 2.06% in the Central BS, and 94.3 ± 1.93% in the NYS. The lowest fraction of HMA in the Laizhou Bay was attributed to high sedimentation rates and higher suspended particulate matter concentrations due to inputs from the Yellow River. The modeled 1-, 10- and 100- year mass budgets indicated that the Liaodong Bay in the north of the BS was a sink of HMA, the Bohai Bay and Laizhou Bay in the west and south of the BS acted as sources, and the Central BS and NYS were a transition area for most HMA.