Search

Surface dust samples were collected from university campuses in Xi'an, and X-ray fluorescent spectrometry was used to determine the contents of nine heavy metals (Mn, As, Pb, Cr, Co, Ni, Cu, V, and Zn). Enrichment factors were subsequently used to determine the enrichment degree of each element and the preliminary determination of the pollution sources. The R programming language and SPSS were used for cluster analysis and principal components analysis to identify the pollution sources. The results showed that the average concentrations of all nine heavy metal elements were higher than their surface soil background values in Shaanxi Province; however, Mn, Co, As, V, and Ni exhibited relatively little enrichment and were less affected by human interference. Cr and Cu were moderately enriched, whereas Zn and Pb were significantly enriched, and human activities played a major role in the enrichment of these four elements. The main sources of Mn, Co, As, V, and Ni in surface dust samples from the university campuses were natural sources, whereas the accumulation of Zn, Cr, and Pb were mainly due to traffic sources, and Cu originated both from the auto repair industry and from paint coatings.

Fifty dust samples were collected from Xingtai City to study the source characteristics of heavy metals in suspended particles of urban road dust from industrial enterprise transformation cities. The contents of Cr, Mn, Co, Ni, Cu, Zn, As, and Pb in particles of urban road dust smaller than 100 μm were determined by X-ray fluorescence spectrometry, and their pollution levels were assessed by enrichment factor. The possible sources of heavy metals measured in the dust were identified by multivariate statistical analysis methods including correlation analysis, principal component analysis, and cluster analysis. The results indicated that in comparison to the element background values of local soil, the particles of urban road dust smaller than 100 μm from Xingtai City had higher Cr, Mn, Co, Cu, Zn, and Pb concentrations. The accumulation level of Co was the highest, followed by Zn, and Pb and Cu, whereas the other trace metals were deficient or showed minimal enrichment in the suspended road dust. The multivariate statistical analysis results showed that Cr, Mn, and Ni had significant positive correlation. These metals belong to both a principal component and a cluster, whereas Cu, Zn, and Pb belong to just a principal component. Considering the content characteristics and the results of multivariate statistical analysis of various heavy metal elements in the suspended samples, these results illustrated that the Cr, Mn, and Ni in the suspended particles of urban dust from Xingtai City roads mainly come from natural and industrial sources, whereas the Zn, Pb, and Cu originate from transportation and coal sources; As comes from natural sources, and Co is mainly affected by industrial activities.

Road dust samples were collected from four different functional areas in Xi'an City, i.e., an educational area, a residential area, a park area, and a traffic area, to study the influence of intensive human activities on local urban environmental quality. The contents of Cu, Pb, Zn, Cr, Co, V, Mn, and Ni in the smaller than 63 μm road dust particles were determined by X-ray fluorescence spectrometry, and the pollution levels of these metals were assessed by a geoaccumulation index and a pollution loading index. The possible sources of heavy metals measured in the dusts were identified by multivariate statistical analysis methods, including correlation analysis, principal component analysis, and cluster analysis, and the contributions of each source to heavy metals in the dusts were apportioned by a principal component analysis-multiple linear regression receptor model. The results showed that the contents of Cu, Pb, Zn, Cr, Co, V, Mn, and Ni in the smaller than 63 μm road dust particles of urban road dust from Xi'an ranged 14.2-96.9, 23.5-206.1, 20.0-899.4, 122.7-262.8, 7.9-14.2, 48.7-71.5, 274.0-448.9, and 22.4-62.5 mg·kg -1 , respectively, with averages of 46.6, 97.4, 169.2, 177.5, 9.8, 57.1, 337.6, and 29.3 mg·kg -1 . Compared to the element background values of Shaanxi soil, the finer particles of road dust from Xi'an had elevated contents of Cu, Pb, Zn, and Cr. The finer particles of road dust from Xi'an were unpolluted by Co, V, Mn, and Ni; unpolluted to moderately polluted by Cr, Cu, and Zn; and moderately polluted by Pb. The assessment results of comprehensive pollution indicated that the pollution levels of the heavy metals in the dusts were mainly unpolluted to moderately polluted. The multivariate statistical analysis results displayed that Cr, Cu, Pb, and Zn had significant positive correlation. These metals belong to a principal component and a cluster, whereas Mn, Ni, V, and Co belong to another principal component and cluster and have significant positive correlation. Considering the content characteristics of heavy metals in the dusts, these results illustrated that two kinds of sources for the heavy metals studied existed for the finer particles of road dust from Xi'an, i.e., Cu, Pb, Zn, and Cr mainly originated from traffic sources, whereas V, Co, Mn, and Ni were mainly from natural sources. The contributions of traffic sources and natural sources to the heavy metals in the finer particles of the road dust from Xi'an were respectively 56.7% and 43.3%.

A total of seventeen surface soil samples were collected from urban parks in Xi'an city. The concentration of sixteen priority polycyclic aromatic hydrocarbons (PAHs) were analyzed by high performance liquid chromatography (HPLC). In addition, the composition, source, pollution level and a risk assessment of PAHs in surface soil of park were evaluated. The results showed that the total concentrations of sixteen PAHs ranged from 0.362 to 1.336 μg·g -1 , with a mean value of 0.591 μg·g -1 . The concentration of seven carcinogenic PAHs (Σ 7 CPAHs) ranged from 0.051 to 0.528 μg·g -1 , with a mean value of 0.181 μg·g -1 . Compared to the Σ PAHs levels of other cities of China, the Σ PAHs in park surface soils in Xi'an are relatively low. PAHs in the soil samples were dominated by low molecular weight PAHs with 2 and 3 rings. The results of source analysis showed that the PAHs in park surface soil mainly originated from the combustion of fossil fuels, however, the source of PAHs in some samples is complex and from mixed sources, such as oil spills, oil burning, and incomplete combustion of coal and biomass. The ecological risks of PAHs in the surface soil were evaluated according to the soil quality guidelines to be ERL (effects range low) and ERM (effects range median), and these results showed that all samples, in general, were polluted. However, the potential ecological risks of PAHs were at a low level. The incremental life cancer risk (ILCR) assessment indicated that health risks for children and adults were both in a permissible range, however, the risks for children exposed to the soil were considerably higher than for adults. Dermal contact was the main exposure pathway that resulted in the relatively higher risk, followed by ingestion.

The soils from residential areas of Xi'an city were selected as a case area. The absolute principal component scores-multivariate linear regression (APCS-MLR) model and the ordinary kriging interpolation were combined to identify and apportion the pollution sources of soil heavy metals (As, Ba, Co, Cu, Mn, Ni, Pb, Sr, Zn,V), the percentage of contribution of every source for every element, and the spatial distribution characteristics of contribution rates. Compared with the background values of cinnamon, which is the main soil type in Xi 'an, the accumulation levels of Pb, Cu, Sr, Co, Zn, Ba, Ni, As, Mn, V in soil of urban residential areas in Xi'an city decreased in turn. The standard-exceeding ratios of Ba, Co, Cu, Pb, Sr, Zn were higher than those of other studied elements. Three main pollution sources of soil heavy metals in residential areas were natural source, traffic sources, and fossil fuel combustion source, respectively. Natural source was the main source of As, Mn, Ni, V in studied residential areas. The average contribution rate of natural source for As, Mn, Ni, V was 69.63%, 74.28%, 68.65%, 77.09%, respectively. The fossil fuel combustion was the second largest contributor for their accumulation in these studied residential areas. Its contribution rate for As, Mn, Ni was 23.07%, 19.09%, 23.13%, respectively. The contribution of traffic emissions was lower. Their spatial distribution characteristics tended to be lower in west and higher in east. The average contribution rates of fossil fuel combustion source for Co, Pb, Sr, Zn were 59.84%, 42.22%, 44.50%, 44.44%, respectively. The performance of spatial distribution was increased gradually from the city center to the outside. The sources of Ba were given priority to natural source and fossil fuel combustion source, and the average contribution rates were 41.67% and 48.27%, respectively. The contribution rate of fossil fuel combustion source for Ba gradually decreased from the center of the city. The contribution rates of natural source, traffic source, and fossil fuel combustion source for Cu were 37.00%, 20.47% and 26.50%, respectively.

A total of 58 surface dust samples were collected in urban area of Xi'an City. High Performance Liquid Chromatography (HPLC) was used to analyze the concentrations of six phthalic acid esters (PAEs) listed as priority pollutants by United States Environmental Protection Agency (U.S. EPA). Composition, distribution, environmental sources and exposure characteristics of PAEs in the surface dust were further studied. All analyzed PAEs were detected in the surface dust. The concentration of individual PAE compounds varied from not detectable to 183.19 mg·kg -1 and their mean concentrations decreased in the order of DEHP>DnBP >>DEP >DMP >BBP >DnOP. The total concentration of six PAEs (∑6PAEs) ranged from 0.87 to 250.30 mg·kg -1 with an average of 40.48 mg·kg -1 , and followed the order of parks >traffic area >mixed business and traffic area >residential area >educational area >industrial area. The ∑6PAEs presented the decreasing trend along the main urban area - the second ring road - the third ring road. The results of correlation analysis, principal component analysis and cluster analysis showed that PAEs in surface dust of Xi'an City were related to the application of plasticizers, the emission of cosmetics and personal care products along with building materials and home decoration materials. The dose order of human exposure to PAEs in surface dust was the direct ingestion by hand and mouth >>dermal adsorption >inhalation via mouth and nose. Meanwhile, the intake dose of children was higher than that of adults. However, the intake dose of DnBP, DEHP, DBP and BBP was lower than the tolerable daily intake (TDI) suggested by European Union Scientific Committee for Toxicity, Ecotoxicity and the Environment (EU CSTEE) and the reference doses (RfD) proposed by U.S. EPA.

A total of 58 surface dust samples were collected from Xi'an city. The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were analyzed by gas chromatography with a flame ionization detector (GC-FID). At the same time, the distribution and sources of PAHs in surface dust were studied. The results showed that the concentrations of individual PAH ranged from 14.69 to 6370. 48 microg x kg(-1), and the total concentrations of 16 PAHs (∑16 PAHs) ranged from 5039.67 to 47,738.50 microg x kg(-1), with a mean of 13,845.82 microg x kg(-1). Compared to the Y PAHs levels of other cities, the ∑16 PAHs in surface dust of Xi'an belonged to a relatively higher level. PAHs in surface dust were mainly dominated by high molecular weight PAHs with 4-6 rings and the concentration of 7 carcinogenic PAHs (1 CPAHs) accounted for 46.08% of 3 16PAHs. The mean of ∑16 PAHs in surface dust had the highest concentration at industrial area; followed by the educational area, traffic area, business and traffic area; residential area and parks showed relatively lower concentration. The average content of ∑16 PAHs in surface dust presented an increasing trend along the main urban area--the second ring road--the third ring road. ∑16 PAHs in surface dust had higher concentrations at the industrial areas of the east and west suburbs of Xi'an, the south suburb and the north section of the second ring road; ∑16 PAHs concentrations in the main urban area, north suburb and southeast part of Xi'an were relatively lower. The results of ratio, cluster analysis and principal component analysis showed that PAHs in surface dust were mainly originated from the combustion of fossil fuels and coal combustion. Among them, diesel combustion reached 36.07%, gasoline combustion accounted for 32.31%, and coal combustion was resposbe for 23.40%

The magnetic susceptibility and the concentrations of Co, Cr, Cu, Pb, Sn, Sr and Ba in topsoil samples from Xi'an City were measured to study their spatial distribution and their correlation in this study. The results show that the concentrations of all measured heavy metals are higher than their background values in Cinnamon topsoil, which is the main soil type of Xi'an City. The heavy metals concentrations and the magnetic susceptibility of the studied samples display moderate variance. Co, Cr, Cu, Pb, Sn, Sr and Ba are significantly positively correlated with low-frequency magnetic susceptibility, while are significantly negatively correlated with frequency susceptibility. The spatial distribution of low-frequency magnetic susceptibility is identical with the concentrations of Pb and Cu. However, the spatial variation of frequency magnetic susceptibility is different from the concentrations of Co, Cr and Ba. The pollution assessment results show that the heavy metal pollution in topsoil of Xi'an City is moderate. The spatial contribution of the pollution load index was significantly correlated with the magnetic susceptibility of topsoil in Xi'an City. Therefore, soil magnetic susceptibility can be used as an effective monitoring means for heavy metal pollution in urban soil.

Heavy metal concentrations in street dust of Baoji City were investigated by using X-Ray fluorescence spectrometry (XRF) and atomic adsorption spectrometry (AAS). The results show that the mean concentrations of Cu, Pb, Zn, Mn, Co, Ni, Cr and Cd are 123.2, 408.4, 715.1, 804.2, 15.9, 48.8, 126.7 and 5.5 microg x g(-1), respectively, which are higher than those of the element background values of International, Chinese, and Shaanxi Soil, especially for Cu, Pb, Zn and Cd. The source of heavy metal elements in street dust of Baoji City was identifed by multivariate statistics analysis (correlation analysis, principal component analysis and cluster analysis), and the results show that Ni and Cr mainly originate from natural source (local soil); Cu, Pb, Mn and Co have mixed sources of human activities (industry and traffic) and nature (local soil); Zn and Cd represent traffic and industry sources. At the same time, the speciation characteristics of heavy metals in street dust of Baoji City were investigated by using the modified BCR sequential extraction procedure and ICP-MS. The results show that Mn, Co, Ni and Cr are dominated by residue (over 48.52%), Zn and Cd mainly exist in acetic acid extractable part (44.43% and 44.08%), Cu is rich in oxidizable (48.22%) and residual (37.65%) parts, Pb is mainly in reducible part (45.42%). The order of mobility of heavy metal elements is Cd (90.11%) > Pb (82.33%) > Zn (79.32%) > Cu (62.35%) > Mn (51.48%) > Co (29.02%) > Ni (23.62%) > Cr (18.68%), in which of them, Cd, Pb, Zn, Cu and Mn have stronger transformation (over 50%) and higher potential harm.

An experimental model was made on the improvement of sources water quality in the Huangpu River through the construction of a special aquatic ecosystem using ecological embankments. A 6 d retention time (RT) gave the highest removal rate capacity and benefit of micro-organic pollutants. Under these conditions, the removal rates were 70.5% atrazine, 57.7% dimethyl phthalate, 72.4% phthalic acid bis (2-ethylhexyl) ester, 62.4% diethyl phthalate, and 45.1% dibutyl phthalate. The varieties of micro-organic pollutants reduced from 51 to 28. In contrast, in the control pool with hard embankment, the removal rates only reached 40.2% atrazine, 42.9% dimethyl phthalate, 54.8% phthalic acid bis (2-ethylhexyl) ester, 52.0% diethyl phthalate, and 16.2% dibutyl phthalate. Through coordination of all constituent elements of special aquatic ecosystem, significant amounts of micro-organic pollutants were removed.

The potential of nitrification and denitrification of sediment and the density of ammonium-oxidizing bacteria and nitrite-oxidizing bacteria in sediment in water quality purifying system with hydroponic bio-filter method (HBFM) were measured. The variation of nitrification and denitrification potential of the sediment along the stream way was quantitatively studied. The results show that among the sediments from front, middle and retral part of the stream way, the sediment from middle part reached a maximum nitrification potential . nitrification potential of 4.76 x 10(-6) g/(g x h), while the sediment from front part reached a maximum denitrification potential of 8 .1 x 10(-7) g/(g x h). The distribution of nitrification potential accords with the ammonium-oxidizing bacteria density. The key for improving nitrogen removal efficiency of HBFM system consists in changing nitrification & denitrification region distributing and accordingly enhances denitrification process.