Bioavailability-based risk assessment of various heavy metals via multi-exposure routes for children and teenagers in Beijing, China.

Assessing the health risks of sensitive population, such as children and teenagers, through multiple exposure routes (MERs) such as ingestion, inhalation, and dermal contact is critical for policy creation that protects or reduces exposure to pollutants for all populations. Heavy metal (HM) contents in food and environmental media in Beijing, capital of China, were collected. Furthermore, on the basis of considering the bioavailability of HMs, we evaluated the multiple environmental routes and health risks to HMs in children and teenagers of eight age groups (2-<3, 3-<4, 4-<5, 5-<6, 6-<9, 9-<12, 12-<15, and 15-<18) in Beijing, China by Monte Carlo simulation approach. The main findings are as follows: lead exposure in children aged 2-<3 years exceeds the exposure dose (0.3 µg·kg-1·d-1) of 0.5 point reduction in intelligence quotient. Moreover, children aged 2-<3 and 6-<9 years have relatively high non-carcinogenic risk (NCR) of 1.32 and 1.30, respectively. The carcinogenic risk (CR) for children aged 6-<9 and 9-<12 years is 2.73×10-6 and 2.39×10-6, respectively. Specifically, the contributions of oral ingestion, dermal contact, and inhalation to the NCR were 69.5%, 18.9%, and 11.6%, respectively. Moreover, the combined NCR contributions of copper, cadmium, mercury, and arsenic (As) were about 69.4%. The contributions of the above three routes to the CR were 93.4%, 4.1%, and 2.5%, in that order, with the largest CR contribution of As being about 92.0%. This study can provide new ideas for accurately assessing the exposure and health risks of HMs in the population, and we believe that it is necessary to update the national standards for food and soil based on the bioavailability of HMs.

Occurrence and transport of N-nitrosamines in the urban water systems of the Pearl River Delta, southern China.

The discharge of substantial amounts of N-nitrosamines-contained wastewater into receiving rivers can significantly deteriorate water quality, as these carcinogenic compounds can be easily transported into groundwater and drinking water systems. This study investigated the distribution of eight species of N-nitrosamines in river water, groundwater, and tap water located in the center of the Pearl River Delta (PRD), China. The results showed that three major N-nitrosamines, including N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), and N-nitrosodibutylamine (NDBA), with concentrations of up to 64 ng/L, were observed in river water, groundwater, and tap water, whereas the other compounds occurred sporadically. In river water and groundwater, high concentrations of NDMA, NDEA, N-nitrosomorpholine (NMOR), and NDBA were found in industrial and residential lands as compared to agricultural lands owing to the influence of various human activities. The primary sources of N-nitrosamines in river water were industrial and domestic wastewater, and the infiltration of river water was responsible for the high levels of N-nitrosamines in groundwater. Among the target N-nitrosamines, NDEA and NMOR with long biodegradation half-lives (>4 days) and low LogKow values (<1) displayed the highest potential for groundwater. N-nitrosamines in groundwater and tap water pose significant potential cancer risks to residents, especially children, and juveniles, with lifetime cancer risks of over 10-4, necessitating advanced water treatments for drinking water and critical controls on primary industrial discharge in urban areas.

Hydrogeochemical characterization and water quality assessment in Altay, Xinjiang, northwest China.

The safety of drinking and irrigation water is an issue of great concern worldwide. The rational development and utilization of water resources are vital for the economic and societal stability of Altay, an extremely arid area. In this study, three types of water samples (25 river waters, 10 groundwaters, 6 lake waters) were collected from main rivers and lakes in Altay and analyzed for electrical conductivity, total dissolved solids, pH, major ions (i.e., K+, Na+, Ca2+, Mg2+, HCO3-, Cl-, SO42-, NO3-, NO2-, F-), and trace elements (i.e., Al, Li, B, Sc, Ti, Mn, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Mo, I, Ba, U). The water quality index (WQI), hazard quotient, carcinogenic risk, Na percentage, and Na adsorption ratio were then calculated to evaluate the water quality for drinking and irrigation. The results showed that the main hydrochemical type of river waters and groundwaters was Ca-HCO3, whereas that of lake water was mainly Na-SO4. The WQIs (9.39-170.69) indicated that the water quality in Altay ranged from poor to excellent. The concentrations of As, Ni, and U need to be carefully monitored since their average carcinogenic risks (for all waters collected, for adults) reached 0.05686, 0.06801, and 0.14527 and exceeded the safety risk levels (10-4-10-6) by at least 568 times, 680 times, and 1452 times, respectively. The result of Na% and SAR indicated that lake waters (with Na% of 62.92 and SAR of 41.63) and groundwaters (with Na% of 37.88 and SAR of 5.58) in Altay were unsuitable for irrigation, while river water (with Na% of 29.24 and SAR of 3.33) could meet the irrigation quality requirements. The results of this study could help promote reasonable water resource use among three types of waters and population protection in Altay.

Effects of lithium resource exploitation on surface water at Jiajika mine, China.

Heavy metal and metalloid (HMM) contamination of the water environment caused by mining activities is a great challenge to the global mining industry. HMMs released by various mines could easily enter the surrounding environment and pose serious threats to human health. Although the HMM pollution of surface water in various mines has been widely researched, relevant studies on the effects of mining activities on the surface water of hard-rock-type Li mines are scarce. Herein, a total of 81 water samples were collected from Jiajika mine for the first time, the largest hard-rock-type Li mine in Asia. The physical parameters and concentrations of HMMs and major ions of the samples were analyzed to evaluate the water quality and HMM level of surface water. Results showed that (1) most of the parameters analyzed adhered to the strictest guidelines of Chinese surface waters and the drinking water guidelines of WHO, except Mn, Pb, and As of a few samples from tailings-affected areas and Li-bearing areas; (2) mineral tailings obviously increased the pH and decreased the dissolved oxygen (DO) of the surrounding surface waters; (3) the highest concentrations of As (5.58 µg/L), Zn (81.8 µg/L), Ba (5.26 µg/L), and Co (0.33 µg/L) were observed around the tailings reservoir, whereas the highest concentrations of Cr (1.5 µg/L), Mn (380 µg/L), Pb (28.4 µg/L), and V (3.16 µg/L) were observed in Li-bearing areas; and (4) according to the statistical results, the concentrations of As, Cr, Ni, and V in surface water were mainly affected by mining activities, whereas those of Cu, Zn, Ba, Co, and Pb were dominantly affected by natural processes. These results provide useful information about water quality in relation to Li mining and can help the government make reasonable decisions regarding hard-rock-type Li resource exploitation activities.

Source apportionment of fine organic carbon (OC) using receptor modelling at a rural site of Beijing: Insight into seasonal and diurnal variation of source contributions.

This study was designed to investigate the seasonal characteristics and apportion the sources of organic carbon during non-haze days (<75 µg m-3) and haze (≥75 µg m-3) events at Pinggu, a rural Beijing site. Time-resolved concentrations of carbonaceous aerosols and organic molecular tracers were measured during the winter of 2016 and summer 2017, and a Chemical Mass Balance (CMB) model was applied to estimate the average source contributions. The concentration of OC in winter is comparable with previous studies, but relatively low during the summer. The CMB model apportioned seven separate primary sources, which explained on average 73.8% on haze days and 81.2% on non-haze days of the organic carbon in winter, including vegetative detritus, biomass burning, gasoline vehicles, diesel vehicles, industrial coal combustion, residential coal combustion and cooking. A slightly lower percentage of OC was apportioned in the summer campaign with 64.5% and 78.7% accounted for. The other unapportioned OC is considered to consist of secondary organic carbon (SOC). During haze episodes in winter, coal combustion and SOC were the dominant sources of organic carbon with 23.3% and 26.2%, respectively, followed by biomass burning emissions (20%), whereas in summer, industrial coal combustion and SOC were important contributors. Diurnal contribution cycles for coal combustion and biomass burning OC showed a peak at 6-9 pm, suggesting domestic heating and cooking were the main sources of organic aerosols in this rural area. Backward trajectory analysis showed that high OC concentrations were measured when the air mass was from the south, suggesting that the organic aerosols in Pinggu were affected by both local emissions and regional transport from central Beijing and Hebei province during haze episodes. The source apportionment by CMB is compared with the results of a Positive Matrix Factorization (PMF) analysis of ACSM data for non-refractory PM1, showing generally good agreement.

In situ stabilization of heavy metals in a tailing pond with a new method for the addition of mineral stabilizers-high-pressure rotary jet technology.

As the demand for metal minerals grows, the number of mine tailings increases dramatically worldwide. Toxic heavy metals (HMs) in tailings tend to migrate into the environment and cause serious damage to the surroundings. Possible eco-friendly solutions for the in situ stabilization of HMs in tailing ponds are required to reduce their mobility. Leaching tests were performed with attapulgite, zeolite, and bentonite to determine which stabilizer is more efficient. As a result, attapulgite has more significant effect with certain dose on metal mine tailings than zeolite or bentonite, especially in a strongly acidic environment. In addition, an in situ stabilization experiment was performed by adding a stabilizer to a lead-zinc mine tailing pond with high-pressure rotary jet technology. The field experiment indicated that the concentrations of HMs in the leachate substantially decreased (30.5% for Cr, 43.1% for Cu, 87.8% for Zn, 82.9% for Cd, and 42.4% for Pb) after the HMs were stabilized by high-pressure rotary jet technology. A set of parameters for the rotary jet process was obtained when the in situ stabilization experiment was carried out.

Content and dietary exposure of cadmium among residents in Northeast China: a case study based on the 5th China Total Diet Study.

Cadmium (Cd), one of the harmful heavy metals, and its accumulation or pollution might cause itai-itai disease. In this study, we investigated the dietary exposure of Cd among residents in Northeast China (including Heilongjiang, Jilin, and Liaoning provinces) and also compared the health risks in adult males in terms of dietary intake. Cd contents in 12 categories of foods were derived from original data from the 5th China Total Diet Study (TDS). The following results were obtained in this study: (i) dietary exposure levels of Cd at the margin of safety (MOS) were 4.55, 1.82, and 2.85 in Heilongjiang, Jilin, and Liaoning provinces, respectively; (ii) the primary dietary sources of Cd included cereals, legumes, potatoes, meat, aquatic products, and vegetables; (iii) Cd contents in the same food category from different regions were not significantly different from the limit of China's National Standards (LCNSs); (iv) dietary exposure of Cd would not have a detrimental effect on the health of residents in Northeast China; (v) we recommend the government to take precedence of the supervision and spot-checking of cereals, legume-nuts, potatoes, meat, aquatic products, vegetables, and alcoholic beverages because of the higher dietary consumption than others; (vi) 99.99% of the Cd content in cereals, legumes, vegetables, meat, and aquatic products sold in Northeast China was less than the LCNSs at the present situation; and (vii) the harmful effects of Cd to human beings are associated with the Cd content in foods and the consumption of such foods.

Assessment of human health risk based on characteristics of potential toxic elements (PTEs) contents in foods sold in Beijing, China.

Metals are generally classified into essential metals groups. Essential metals include copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn), and nonessential metals include cadmium (Cd) and lead (Pb) etc. However, excessive intake of metals even essential metals would have detrimental effect on the body. In this study, seven potential toxic elements (PTEs) (i.e., Cd, Cr, Cu, Fe, Mn, Pb and Zn) and their distribution characteristics in the foods were analyzed as well as the combination of correlation analysis, factor analysis and cluster analysis were constructed. Meanwhile, combined with the dietary consumption data from the Fifth China Total Diet Study (FCTDS), the dietary exposure of PTEs were analyzed and a consequent safety risk assessment was conducted. The main results are as follows: (1) PTE contents in simply-processed samples were found to be lower than those in the highly-processed samples. (2) The average daily intake of the PTEs were about 12.26 (Cd), 153.17 (Cr), 25.16 (Pb) µg/d, 1.90 (Cu), 20.19 (Fe), 7.12 (Mn) and 12.69 (Zn) mg/d, respectively. (3) The total target hazard quotient (TTHQ) was 2.88, which was lower than 10. Therefore, the long-term consumption of these foods combined with the current dietary structure would not have a detrimental effect on the health of residents in Beijing.

Levels of eight heavy metals and health risk assessment considering food consumption by China's residents based on the 5th China total diet study.

The total diet study (TDS) is a significant part of food consumption-based health risk assessment. Since 1990, China has conducted five TDSs based on its unique food culture. In the present study, the health risks of residents from 20 regions of China are assessed by comparing the estimated daily intake (EDI) with adequate intake (AI) for Cr, and the estimated dietary exposure (EDE) with the reference dose (RfD) for seven toxic heavy metals (THMs), which are Al, As, inorganic arsenic (iAs), Cd, Hg, methyl mercury (MeHg), and Pb. The original data were sourced from the 5th China TDS. The data indicated the following: (1) Cereals and vegetables were the main dietary exposure sources of Al, As, iAs, Cd, and Cr; aquatic foods were the important dietary exposure source for As, Hg, and MeHg, especially for the residents from coastal regions. (2) Compared to other elements, Pb had more dietary exposure sources, which included cereals, vegetables, meats, and beverages and water. (3) Potatoes, beverages and water, and meats were the important sources of Al, iAs, and Cr. The results showed that the average level of the dietary intake of Cr was 11 times higher than the AI, as determined from the ratio of EDI to Al. Moreover, the hazard quotients (HQs) of Al, iAs, Cd, Hg, MeHg, and Pb were <1, while that of As (6.49) was >1; therefore, the EDIs of As and Cr by the residents of China are worthy of attention. Additionally, the discrepancies in the dietary exposures of HMs by the residents were due to the different HM contents among different types of foods, and the different dietary structures.

China's carbon dioxide emissions from cement production toward 2030 and multivariate statistical analysis of cement consumption and peaking time at provincial levels.

China, the largest developing country, is the world largest cement producer and the largest cement-consuming nation. Although China's cement output reached its peak in 2014, regions, i.e., Fujian and Yunnan provinces, were no peaking until 2016. At the same time, rare studies referred to China's cement consumption and CO2 emissions from the perspective of cement consumption at the provincial level. We developed the S-Logistic, polynomial model, and ARIMA model to study the peaking time of cement consumption at the provincial level, and we also projected China's cement consumption and CO2 emissions toward 2030. Meanwhile, the discrepancies of peaking time and cumulative cement consumption per capita (CCCPC) among provinces were also studied based on GDP per capita and urbanization rate (UR). The results are that the CCCPC respectively in the range of 22-34 ton, 18-25 ton, and 17-27 ton in the eastern, intermediate, and western zone when cement consumption reached its peak. We draw the following conclusions that the CCCPC in 2030 could reach ~ 43 ton and the projected cement consumption is ~ 1252.72 Mt, which accounts for 50% of that in 2017, and cement CO2 emissions are at the range of 488.19-510.90 MtCO2 in 2030. Furthermore, capacity replacement, controlling new capacity and eliminating backward capacity are significant of greenhouse gas emission reduction not only for China, but also for the global cement industry.

Simultaneous adsorption and immobilization of As and Cd by birnessite-loaded biochar in water and soil.

A novel biochar was prepared by loading birnessite to improve its capability to simultaneously adsorb As(III), As(V), and Cd(II) in water and soil. Layer sheet-structured birnessite was successfully loaded onto the biochar surface with increased functional groups. SEM, XRD, and FTIR combining with XPS analysis were utilized to characterize birnessite-loaded biochar and its adsorption mechanisms for As and Cd(II). The saturated adsorption capabilities of the birnessite-loaded biochar (BRB) for As(III), As(V), and Cd(II) were as large as 3543, 2412, and 9068 mg/kg (calculated by Langmuir isotherm model), much higher than for the corresponding non-loaded biochar (no adsorption of As, 4335 mg/kg for Cd). Adsorption of Cd and As onto BRB was controlled by multi mechanisms; Cd(II) appeared to coordinate to vacant sites of birnessite, while As formed surface complex with functional groups. Furthermore, BRB showed higher abilities for co-adsorption of As(III) and Cd or As(V) and Cd, which may be due to the formation of Cd3(AsO4)2 surface precipitate as well as synergistic reaction between anions and cations. After conditioning to soil, BRB showed potential for Cd and As remediation under both flooded and unflooded conditions. These results suggested that BRB can be used as an effective sorbent for simultaneous immobilization of heavy metals, especially As and Cd, in environmental and agricultural systems.

China's cement demand and CO2 emissions toward 2030: from the perspective of socioeconomic, technology and population.

China is the largest cement producer and carbon dioxide (CO2) emitter in the world. The country has attracted too much attention in calculating and comparing its CO2 emissions. However, as the second largest CO2 emitter after the fire power industry, China's long-term cement demand and cement-related CO2 emission projections were not fully studied. The Chinese government, however, committed that by 2020 and 2030, China's per capita GDP of CO2 emissions would be lower than that in 2005 by 40-45% and 60-65%, respectively. In this paper, China's cement demand in 2030 was projected based on the population size, urbanization rate, fixed assets investment, and per capita GDP. Furthermore, decoupling study in China's cement industry was also involved based on the GDP and CO2 emissions during 2001-2015. We also used the diffusion rate of 12 types of CO2 reduction measures and two changed scenarios of clinker-to-cement ratio, to project the cement CO2 emission factors toward 2030 after determining the accounting scope. Meanwhile, the CO2 emissions of China's cement industry through 2030 were projected naturally. The results showed that China's cement output in 2030 will be approximately 2000, 1650, and 937 Mt. based on the fixed assets investment, urbanization rate, and per capita GDP respectively. The projected two scenarios cement CO2 emission factors were resp. 407.83 and 390.02 kg CO2/t of cement which were 42.6 and 45.1% lower than that in 2005. The cement CO2 emissions were projected to be in the range of 366 to 818 Mt. in 2030. Additionally, China's total cement output value has been decoupling from cement CO2 emissions from 2012, which is mainly attributed to eliminating backward capacity, reducing excess capacity or the declining cement output. And decoupling economic from China's cement CO2 emissions may change to be strong or weak decoupling in the near future. As cement production is one of the factors effecting cement CO2 emissions, the most important measure for controlling cement CO2 emissions is a reasonable capacity utilization rate. It is therefore important to control the growth of cement CO2 emissions by regulating the capacity utilization rate within a reasonable range. Eliminating backward capacity, removing excess capacity, controlling new capacity, staggered production, and the "going global" of cement equipment can have great impacts in controlling the total amount of cement output and CO2 emissions.

Empirical assessing cement CO2 emissions based on China's economic and social development during 2001-2030.

Cement industry is a large emitter of carbon dioxide (CO2), taking up 5-8% of anthropogenic CO2 emissions. China is the largest developing country in the world. With the fast urbanization rate, economic growth and rapid development of industry, China's cement production is soaring year by year. Also, cement CO2 emissions increased year by year and aroused the rising attention. However, the historical province- and nation-level cement production situations, driving forces of cement output and/or demand based on rapid economic growth and urbanization rate, the peak of cement consumption and China's cement demand projection and CO2 emissions through 2030 when China should fulfill the international commitments were not clear. The present study summarized the characteristics of China's cement production and CO2 emissions during 2001-2015, projected cement CO2 emission scenarios based on diffusion of alternative materials and technical innovation toward 2030. The following results were summarized, clinker- and cement- CO2 emission factors (EFs) were declining year by year with the technical innovation. CO2 emissions increased with the increase of cement output year by year. The discrepancies of CO2 emissions from different researches were becoming large year by year, and the biggest difference of CO2 emissions reached 49% in 2015. Accordingly, we recommended active EFs for the calculation of cement CO2 emissions. Cement production situation varies greatly with province, as manifested in unbalanced NSP technology and clinker-to-cement ratio, and energy consumption, which was primarily attributed to the unbalanced resource reserves and economic development. There is still sufficient room for CO2 reduction in China's cement industry, and the use of alternative material was better than technical innovation in such reduction. The optimal emissions in 2030 will be 1490 Mt CO2. And China's cement consumption will be stable in 2030, cumulative cement consumption per capita will be peaked at 23394 kg, and UR will reach 70.1%.

[Effects of Straw Incorporation on Cadmium Accumulation and Subcellular Distribution in Rice].

Cadmium (Cd) is classified as a Group-1 human carcinogen and rice consumption constitutes a major source of dietary intake of Cd for populations whose staple food is rice. Straw incorporation is widely performed in Cd-contaminated paddy fields, which may significantly affect the bioavailability of Cd in soil and the distribution of Cd in rice plants, consequently altering Cd accumulation in rice grains. In this study, both pot and field trials were conducted to investigate the effects of different amounts of straw incorporation (0.0%, 1.0%, 2.5%, and 5.0%) on Cd sub-cellular distribution in rice plants and Cd accumulation in rice grains. The results showed that Cd was mainly sequestered in cell wall, accounting for 86%-95% and 30%-51% of total cadmium in root and shoot cells, respectively. In shoot cells, about 35%-61% of Cd was distributed in cellular soluble fractions. When rice straw was incorporated at 1.0% and 2.5% levels, Cd sequestration in the cell wall significantly increased and Cd translocation from roots to shoots significantly decreased. However, when rice straw was incorporated at the 5% level, Cd sequestration in root cell walls significantly decreased and Cd translocation from roots to shoots significantly increased at the tillering stage. At the filling stage, 5% rice straw incorporation still significantly increased Cd sequestration in root cell walls and Cd translocation from roots to shoots did not significantly change. The rice straw and rape straw used for the field trail contained high concentrations of Cd (0.49 and 0.67 mg·kg-1, respectively). Rape straw incorporation alone or together with lime did not significantly affect Cd accumulation in brown rice or rice straw. Rice straw incorporation alone did not significantly affect Cd accumulation in brown rice or rice straw, while incorporation with lime significantly decreased Cd accumulation in both brown rice and rice straw. Biochar application can also significantly reduce Cd accumulation in rice and when biochar was added together with lime, the reduction in Cd accumulation in rice was more significant. Therefore, at Cd-contaminated paddy fields, rice straw or rape straw is not suggested to be returned directly; incorporation with lime would be better for reducing Cd accumulation in rice grains. The results of this study will provide theoretical and practical guidance for the safe production of rice and for straw recycling at Cd-polluted paddy fields.

Comparison of gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry with electron ionization for determination of N-nitrosamines in environmental water.

N-nitrosamines are trace organic contaminants of environmental concern when present in groundwater and river water due to their potent carcinogenicity. Therefore, N-nitrosamine analysis is increasingly in demand. Gas chromatography-mass spectrometry (GC-MS) and GC-tandem mass spectrometry (GC-MS/MS), both with electron ionization (EI), were compared for analysis of nine N-nitrosamines extracted from environmental water matrices. A total of 20 fishpond water, river water, and groundwater samples from Sihui and Shunde, China were collected for a survey of N-nitrosamine concentrations in real water samples. Various solid-phase extraction (SPE) conditions and GC conditions were first examined for the pre-concentration and separation steps. The analysis of N-nitrosamines in environmental waters demonstrated that their quantification with GC-MS poses a challenge due to the occurrence of co-eluting interferences. Conversely, the use of GC-MS/MS increased selectivity because of the fragmentation generated from precursor ions in the 'multiple reaction monitoring' (MRM) mode, which is expected to extract target analytes from the environmental water matrix. Thus, the high performance of GC-MS/MS with EI was used to quantify nine N-nitrosamines in environmental waters with detection limits of 1.1-3.1 ng L-1. N-nitrosodimethylamine (NDMA) concentrations were in the range of N.D. to 258 ng L-1. Furthermore, other N-nitrosamines, except N-nitrosomethylethylamine (NMEA), N-nitroso-di-n-propylamine (NDPA) and N-nitrosopiperidine (NPIP), were also detected. Our findings suggest that GC-MS/MS with EI would be widely applicable in identifying N-nitrosamines in environmental waters and can be used for routine monitoring of these chemicals.

Evaluation of impact factors on PM2.5 based on long-term chemical components analyses in the megacity Beijing, China.

Nine years of sampling and analyses of fine particles (PM2.5) were performed in Beijing from 2005 to 2013. Twenty-seven chemical elements and black carbon (BC) in PM2.5 were analyzed in order to study chemical characteristics and temporal distribution of Beijing aerosols. Principle component analysis defined different types of elemental sources, based on which, the influences of a variety of anthropogenic activities including governmental intervention measures and natural sources on air quality were evaluated. For the first time, Ga is used as a tracer element for heating activities mainly using coal in Beijing, due to its correlation with BC and coal combustion, as well as its concentration variation between the heating- and non-heating periods. The traffic restrictions effectively reduced emissions of relevant heavy metals such as As, Cd, Sn and Sb. The expected long-term effectiveness of the steel smelters relocation was not observed due to the nearby relocation with increased capacity. Firework display during every Chinese spring festival season and special events such as the Olympic Games resulted in several times higher concentrations of K, Sr and Ba than other days and thus they were proposed as tracers for firework display. The impacts of all these factors were quantified and evaluated. Sand dust or dust storms induced higher concentrations of geogenic elements in PM2.5 compared to non-dust days. Sustainable mitigation measures, such as traffic restrictions, are necessary to be continued and improved to obtain more "blue sky" days in the future.

Long-term variation of black carbon and PM2.5 in Beijing, China with respect to meteorological conditions and governmental measures.

Black carbon (BC) and PM2.5 were studied for nine years from 2005 to 2013 in the Beijing urban area. The overall weekly average mass concentrations of BC and PM2.5 were 4.3 and 66.8 µg/m³. PM2.5 annual means of the nine years are around 2 times of the standard (GB3095-2012) in China, and are 5-7 times higher than the WHO standard. The Beijing Olympic Games in 2008 was a milestone to mitigate aerosol pollution. Temporal distribution of BC shows a distinct declining trend, and annual mean mass concentrations of PM2.5 after 2008 were lower than those before 2008 but increased from 2011 to 2013. Wind rose plots show that high BC concentrations are usually associated with low wind speed of northeastern or southwestern winds, generally causing poor visibility. Governmental mitigation measures such as traffic restriction despite increased motor vehicle numbers and gasoline consumption and industry relocation with declining consumption of coal and coke were successful in reducing BC emissions. Annual mean of BC was reduced by 38% in 2013 compared to 2005. However, BC contamination in Beijing is still severe when compared to other urban areas around the world.

Mitigation of cadmium and arsenic in rice grain by applying different silicon fertilizers in contaminated fields.

A field experiment was established to support the hypothesis that application of different silicon (Si) fertilizers can simultaneously reduce cadmium (Cd) and arsenic (As) concentration in rice grain. The "semi-finished product of Si-potash fertilizer" treatment at the high application of 9000 kg/ha (NP+S-KSi9000) significantly reduced the As concentration in rice grain by up to 20.1%, compared with the control. Si fertilization reduces the Cd concentration in rice considerably more than the As concentration. All Si fertilizers apart from sodium metasilicate (Na2SiO3) exhibited a high ability to reduce Cd concentration in rice grain. The Si-calcium (CaSi) fertilizer is the most effective in the mitigation of Cd concentration in rice grain. The CaSi fertilizer applied at 9000 kg/ha (NPK+CaSi9000) and 900 kg/ha (NPK+CaSi900) reduced the Cd concentration in rice grain about 71.5 and 48.0%, respectively, while the Si-potash fertilizer at 900 kg/ha (NP+KSi900), the semi-finished product of Si-potash fertilizer at both 900 kg/ha (NP+S-KSi900) and 9000 kg/ha (NP+S-KSi9000), and the rice straw (NPK+RS) treatments reduced the Cd concentration in rice grain about 42, 26.5, 40.7, and 23.1%, respectively. The results of this investigation demonstrated the potential effects of Si fertilizers in reducing Cd and As concentrations in rice grain.

Spatio-temporal variations of black carbon concentrations in the Megacity Beijing.

The spatial and temporal distribution and the flux of black carbon (BC) concentration in Beijing were continuously investigated over a two-year period at five sites to highlight the relative influence of contributing sources. The results demonstrate firstly that there is significant spatio-temporal variability of BC in Beijing. Highest concentrations occurred during winter primarily due to stagnant meteorological conditions, and seasonal BC sources, such as coal combustion for heating purposes. Biomass burning was identified as a minor seasonal source during the summer months. BC also varied spatially with higher concentrations in the SE of Beijing and lower concentrations in the NW, due to the differing emission intensity of various local BC sources such as traffic and industry. Frequently, overnight BC concentrations were higher due to specific meteorological conditions, such as the lower urban mixing layer height and various anthropogenic activities, such as exclusive night-time heavy duty vehicle traffic in the inner-city.

The effect of mitigation measures on size distributed mass concentrations of atmospheric particles and black carbon concentrations during the Olympic Summer Games 2008 in Beijing.

The period of the 2008 Olympic Summer Games in Beijing can be considered as a unique opportunity to study the influences of emission reduction measures on air quality improvement. Within this study atmospheric particles of different size classes (2.5 to 80 µm) were investigated before, during, and after the Olympic Games period in order to observe and assess the success of short-term measures to mitigate extreme urban aerosol pollution and also to investigate, which particle size classes were reduced most effectively. Furthermore, black carbon (BC) concentrations in fine particles (PM(2.5)) during the source control period were compared to those of the previous years in order to investigate the decrease of combustion-derived aerosols. It is shown that besides the implemented mitigation measures precipitation decisively contributed to a considerable decrease of particulate air pollution in Beijing compared to the respective concentrations during the time directly before and after the Olympic Games, and also compared to average August concentrations during the previous years and the following year 2009. Particles of the fine fraction of the coarse mode (2.5 to 5 µm), which have a residence time in the order of several days and which, therefore, are typically transported over long distances from outside of Beijing, were less efficiently reduced than coarser particles. This indicates that long-range transport of atmospheric particles is difficult to control and that presumably the established mitigation area was not large enough to also reduce the fine fraction of the coarse mode more efficiently. Furthermore, the study showed that coarse geogenic particles, which originated to a high percentage from construction sites and resuspension processes due to traffic seemed to be reduced most efficiently during the Olympic Games period.