Langbo Ou

Emission of metals from pelletized and uncompressed biomass fuels combustion in rural household stoves in China.

Effort of reducing CO2 emissions in developing countries may require an increasing utilization of biomass fuels. Biomass pellets seem well-suited for residential biomass markets. However, there is limited quantitative information on pollutant emissions from biomass pellets burning, especially those measured in real applications. In this study, biomass pellets and raw biomass fuels were burned in a pellet burner and a conventional stove respectively, in rural households, and metal emissions were determined. Results showed that the emission factors (EFs) ranged 3.20–5.57 (Pb), 5.20–7.58 (Cu), 0.11–0.23 (Cd), 12.67–39.00 (As), 0.59–1.31 mg/kg (Ni) for pellets, and 0.73–1.34 (Pb), 0.92–4.48 (Cu), 0.08–0.14 (Cd), 7.29–13.22 (As), 0.28–0.62 (Ni) mg/kg for raw biomass. For unit energy delivered to cooking vessels, the EFs ranged 0.42–0.77 (Pb), 0.79–1.16 (Cu), 0.01–0.03 (Cd), 1.93–5.09 (As), 0.08–0.19 mg/MJ (Ni) for pellets, and 0.30–0.56 (Pb), 0.41–1.86 (Cu), 0.04–0.06 (Cd), 3.25–5.49 (As), 0.12–0.26 (Ni) mg/MJ for raw biomass. This study found that moisture, volatile matter and modified combustion efficiency were the important factors affecting metal emissions. Comparisons of the mass-based and task-based EFs found that biomass pellets produced higher metal emissions than the same amount of raw biomass. However, metal emissions from pellets were not higher in terms of unit energy delivered.

Low-level prenatal mercury exposure in north China: an exploratory study of anthropometric effects.

In order to investigate anthropometric effects of mercury (Hg) exposure, we examined the status of human prenatal exposure to Hg species, including total mercury (THg), methylmercury (MeHg) and inorganic mercury (IHg), in North China, as well as their potential effects on fetal and infant growth. Hg concentrations in various bioindicators were measured from 50 Chinese women and newborns in 2011. The participants were followed for 12 months to collect anthropometric information. Linear and two-level regression analyses were performed to determine the associations between Hg levels and body growth. The geometric mean levels of THg in the placenta, cord blood, fetal hair, and maternal blood, hair, and urine were 25.88 μg/kg dry wt, 2.73 μg/L, 572.98 μg/kg, 2.29 μg/L, 576.54 μg/kg, and 0.58 μg/g creatinine, respectively. Nearly 100% of Hg presented as IHg in urine, and the percentage of IHg in other bioindicators was 14.86-48.73%. We observed significantly negative associations between Hg levels in some matrixes and anthropometry of neonates (weight and height) and infants (height) (p < 0.05). THg levels in maternal hair were also negatively associated with infant growth rate of weight during 12 months after delivery (p = 0.017). This study suggests that low-level prenatal Hg exposure could play a role in attenuating fetal and infant growth, and the effects of MeHg and IHg are different.

Mercury Export from Mainland China to Adjacent Seas and Its Influence on the Marine Mercury Balance

Exports from mainland China are a significant source of mercury (Hg) in the adjacent seas (Bohai Sea, Yellow Sea, East China Sea, and South China Sea) near China. A total of 240 ± 23 Mg was contributed in 2012 (30% from natural sources and 70% from anthropogenic sources), including Hg from rivers, industrial wastewater, domestic sewage, groundwater, nonpoint sources, and coastal erosion. Among the various sources, the Hg from rivers amounts to 160 ± 21 Mg and plays a dominant role. The Hg that is exported from mainland China increased from 1984 to 2013; the contributions from rivers, industrial wastewater, domestic sewage and groundwater increased, and the contributions from nonpoint sources and coastal erosion remained stable. A box model is constructed to simulate the mass balance of Hg in these seas and quantify the sources, sinks and Hg biogeochemical cycle in the seas. In total, 160 Mg of Hg was transported to the Pacific Ocean and other oceans from these seas through oceanic currents in 2012, which could have negative impacts on the marine ecosystem. A prediction of the changes in Hg exportation through 2030 shows that the impacts of terrestrial export might worsen without effective pollution reduction measures and that the Hg load in these seas will increase, especially in the seawater of the Bohai Sea, Yellow Sea, and East China Sea and in the sea margin sediments of the Bohai Sea and East China Sea.

Mercury Release to Aquatic Environments from Anthropogenic Sources in China from 2001 to 2012

Based on an analysis of measured data and distribution factors, we developed the China Aquatic Mercury Release (CAMR) model, which we used to calculate an inventory of mercury (Hg) that was released to aquatic environments from primary anthropogenic sources in China. We estimated a total release of 98 tons of Hg in 2012, including coal-fired power plants (17%), nonferrous metal smelting (33%), coal mining and washing (25%), domestic sewage (17%), and other sectors (8.3%). The total primary anthropogenic Hg released to aquatic environments in China decreased at an annual average rate of 1.7% between 2001 and 2012, even though GDP grew at an annual average rate of 10% during this period. In addition to the Hg that was released to aquatic environments in Chinas provinces, we estimated the Hg release amounts and intensities (in g/km(2)·yr) for Chinas 58 secondary river basins. The highest aquatic Hg release intensities in China were associated with industrial wastewater on the North China Plain and domestic sewage in eastern China and southern China. We found that the overall uncertainty of our inventory ranges from -22% to 32%. We suggest that the inventory provided by this study can help establish a more accurate map of regional and global Hg cycling; it also has implications for water quality management in China.

Model description of trophodynamic behavior of methylmercury in a marine aquatic system.

A marine food web in Bohai Bay, China, was selected to study methylmercury (MeHg) bioaccumulation, and an aquivalence-based mass balance model was established to explore the possibility of predicting the MeHg concentrations and quantifying MeHg bioaccumulation in the food web. Results showed that both total mercury (THg) and MeHg were biomagnified in the food web. The calculated MeHg concentrations in the selected species agreed well with the measured values, which shows the model could be a useful tool in MeHg concentration prediction in food web. Model outputs also showed that metabolism and growth dilution could be the dominant mechanisms for the reduction of MeHg levels in aquatic organisms. With the increase of trophic level, the contribution of food as a MeHg source for organism is increasing, and MeHg from prey was the dominant source.

Characteristics and transport of organochlorine pesticides in urban environment: air, dust, rain, canopy throughfall, and runoff

Characteristics and transport of organochlorine pesticides (OCPs) in urban multiple environments, including air, dust, rain, canopy throughfall, and runoff water, are explored in this study. Hexachlorocyclohexanes (HCHs) dominated in both air and rain water, and dichlorodiphenyltrichloroethane (DDT) related substances showed a higher affinity to dust. Relatively high concentrations of DDT and dichlorodiphenyldichloroethylene (DDE) in air, rain and dust imply that technical DDT in the environment has been degrading, and there may be unknown local or regional emission sources that contain DDTs in the study area. Source identification showed that DDTs in Beijing urban environments with a fresh signature may originate from the atmospheric transport from remote areas. The ratio of α-/γ-HCH in dust, rain, canopy throughfall and runoff were close to 1, indicating the possible use of lindane. OCPs in runoff were transported from various sources including rain, dust, and canopy throughfall. In runoff, DDTs and hexachlorobenzene (HCB) were mainly transported from dust, and HCHs were mainly from rain and canopy throughfall.

Associations of methylmercury and inorganic mercury between human cord blood and maternal blood: a meta-analysis and its application.

Considering the different ability of placental transfer, an assessment of the cord:maternal blood ratio for both methylmercury (MeHg) and inorganic mercury (IHg) is needed especially for interpreting the low-level prenatal exposure. In this study, we conducted a Monte Carlo-based meta-analysis to comprehensively estimate that ratio for MeHg (RMeHg) and IHg (RIHg). The obtained values followed log-normal distributions, with a mean (standard deviation) of 1.89 (0.98) and 1.01 (0.55) for RMeHg and RIHg, respectively. We also estimated the percentage of MeHg in the blood by means of THg in cord and maternal blood using the RMeHg and RIHg, and obtained a value very close to the measured one (relative deviation, -0.4%). In conclusion, the fetus is exposed to approximately twice as much MeHg and to the same level of IHg as in maternal blood; the introduced model provides a rough but reasonable estimate of the percentage of MeHg in the blood.

Contribution and loading estimation of organochlorine pesticides from rain and canopy throughfall to runoff in an urban environment

Concentrations of OCPs in rain, canopy throughfall, and runoff water were measured in the Beijing metropolitan area during the rainy seasons from 2006 to 2007. This study was conducted to calculate the fluxes of OCPs in rain and canopy throughfall, as well as their contributions to runoff. At urban sites, the contribution of HCB and ΣHCHs from rainfall accounted for approximately 50% of the mass in runoff. At the site with significant coverage of landscaping trees, the HCB, ΣHCHs, and ΣDDTs from the net canopy throughfall accounted for approximately 10% of the mass in the runoff. Based on the data obtained in this study, loadings of OCPs (in μg) in rain, net canopy throughfall, and runoff water were calculated. The input of OCPs from rain and canopy throughfall water accounted for a significant portion of urban runoff. In cities undergoing rapid urban sprawl, monitoring and control of the transport of OCPs in urban runoff are essential for effective control of environmental hazards in surface water bodies.

Modeling time-dependent toxicity to aquatic organisms from pulsed exposure of PAHs in urban road runoff.

Understanding of the magnitude of urban runoff toxicity to aquatic organisms is important for effective management of runoff quality. In this paper, the aquatic toxicity of polycyclic aromatic hydrocarbons (PAHs) in urban road runoff was evaluated through a damage assessment model. Mortality probability of the organisms representative in aquatic environment was calculated using the monitored PAHs concentration in road runoff. The result showed that the toxicity of runoff in spring was higher than those in summer. Analysis of the time-dependent toxicity of series of runoff water samples illustrated that the toxicity of runoff water in the final phase of a runoff event may be as high as those in the initial phase. Therefore, the storm runoff treatment systems or strategies designed for capture and treatment of the initial portion of runoff may be inappropriate for control of runoff toxicity.

Physiologically based pharmacokinetic (PBPK) modeling of human lactational transfer of methylmercury in China

Methylmercury can readily cross the human placental barrier and the blood-brain barrier and cause damage to the vulnerable developing brains of the fetus and infants. Most of the previous studies on the maternal transfer of methylmercury to the next generation have focused on the prenatal period. In this study, human physiologically based pharmacokinetic (PBPK) models of methylmercury were established for breastfeeding mothers and suckling infants based on the existing model prototypes of previous studies. Relevant parameters of the models were modified, and the validation was conducted based on measured data in North China. The models could effectively describe the human lactational transfer of methylmercury, including the time-dependent methylmercury levels in different tissues and organs of the breastfeeding mothers and suckling infants. The results indicated that 77.2% and 14.9% of methylmercury were excreted via hair and breast milk, respectively, from breastfeeding mothers during the first year after delivery. Meanwhile, 79.2% was excreted from the suckling infants during the first year after delivery via hair. Lactational transfer of methylmercury was considered an important pathway of methylmercury exposure for the breastfeeding infants, which accounted for approximately 80% of the accumulated adverse impacts at the early stages of human development.