Suburban Soils Research Articles

Polycyclic aromatic hydrocarbons in soils from urban to rural areas in Nanjing: Concentration, source, spatial distribution, and potential human health risk

Polycyclic aromatic hydrocarbons (PAHs) have become a major type of pollutant in urban areas and their degree of pollution and characteristics of spatial distribution differ between various regions. We conducted a comprehensive study about the concentration, source, spatial distribution, and health risk of 16 PAHs from urban to rural soils in Nanjing. The mean total concentrations of 16 PAHs (∑16PAHs) were 3330ngg−1 for urban soils, 1680ngg−1 for suburban soils, and 1060ngg−1 for rural soils. Five sources in urban, suburban, and rural areas of Nanjing were identified by positive matrix factorization. Their relative contributions of sources to the total soil PAH burden in descending order was coal combustion, vehicle emissions, biomass burning, coke tar, and oil in urban areas; in suburban areas the main sources of soil PAHs were gasoline engine and diesel engine, whereas in rural areas the main sources were creosote and biomass burning. The spatial distribution of soil PAH concentrations shows that old urban districts and commercial centers were the most contaminated of all areas in Nanjing. The distribution pattern of heavier PAHs was in accordance with ∑16PAHs, whereas lighter PAHs show some special characteristics. Health risk assessment based on toxic equivalency factors of benzo[a]pyrene indicated a low concentration of PAHs in most areas in Nanjing, but some sensitive sites should draw considerable attention. We conclude that urbanization has accelerated the accumulation of soil PAHs and increased the environmental risk for urban residents.

Study of Selected Metals Distribution, Source Apportionment, and Risk Assessment in Suburban Soil, Pakistan

Composite soil samples collected from suburban areas were analyzed for Cd, Co, Cr, Cu, Fe, Mn, Pb, Sr, and Zn by atomic absorption spectrophotometry. Based on pseudototal metal analysis, Fe, Mn, Sr, and Zn were the prevailing metals while Cd, Co, Cr, and Pb were the least participants. However, based on bioavailability, Cd, Co, Pb, and Sr were easily leachable and might pose adverse effects to soil biota. In ecological risk assessment, contamination factor demonstrated moderate contamination by Co, Sr, and Zn and high contamination by Cd, Cu, and Pb; geoaccumulation index indicated heavy to extreme contamination by Cd and heavy contamination by Pb; enrichment factor revealed significant enrichment by Co, Cr, Cu, Mn, Sr, and Zn and extreme enrichment by Cd and Pb. Substantial human inputs for Cd, Co, Cr, Cu, Mn, Pb, Sr, and Zn were also revealed by principal component analysis in the examined soil. Overall the study area was found to be contaminated at considerable/high degree.

Polycyclic aromatic hydrocarbons (PAHs) and their derivatives (alkyl-PAHs, oxygenated-PAHs, nitrated-PAHs and azaarenes) in urban road dusts from Xi’an, Central China

Urban road dusts are carriers of polycyclic aromatic compounds (PACs) and are therefore considered to be a major source of contamination of other environmental compartments and a source of exposure to PACs for urban populations. We determined the occurrence, composition pattern and sources of several PACs (29 alkyl- and parent-PAHs, 15 oxygenated-PAHs (OPAHs), 4 azaarenes (AZAs), and 11 nitrated-PAHs (NPAHs)) in twenty urban road dusts and six suburban surface soils (0–5cm) from Xi’an, central China. The average concentrations of ∑29PAHs, ∑4AZAs, ∑15OPAHs, and ∑11NPAHs were 15767, 673, 4754, and 885ngg−1 in road dusts and 2067, 784, 854, and 118ngg−1 in surface soils, respectively. The concentrations of most individual PACs were higher in street dusts than suburban soils, particularly for PACs with molecular weight>192gmol−1. The enrichment factors of individual PACs were significantly positively correlated with log KOA and log KOW, indicating an increasing deposition and co-sorption of the PACs in urban dusts with decreasing volatility and increasing hydrophobicity. Significant correlations between the concentrations of individual and sum of PACs, carbon fractions (soot and char), and source-characteristic PACs (combustion-derived PAHs and retene, etc.), indicated that PAHs, OPAHs and AZAs were mostly directly emitted from combustion activities and had similar post-emission fates, but NPAHs were possibly more intensely photolyzed after deposition as well as being emitted from vehicle exhaust sources. The incremental lifetime cancer risk (ILCR) resulting from exposure to urban dust bound-PACs was higher than 10−6, indicating a non-negligible cancer risk to residents of Xi’an.

Occurrence, sources and health risk assessment of polycyclic aromatic hydrocarbons in urban (Pudong) and suburban soils from Shanghai in China

A comprehensive investigation was conducted to the urban (Pudong) and suburban soils in Shanghai. A total of 154 soil samples were analyzed for 26 PAHs including highly carcinogenic dibenzopyrenes (DBPs). The total concentrations ranged from 25.8 to 7380μgkg−1 for Σ26PAHs and 18.8 to 6320μgkg−1 for 16 USEPA priority PAHs (Σ16PAHs), respectively. The BaP toxic equivalent (BaPeq) concentrations were between 6.41 and 2880μgkg−1 for Σ24PAHs, 1.11 and 620μgkg−1 for Σ16PAHs and 2.72 and 2250μgkg−1 for Σ4DBPs. The high PAH contamination in green land soils might originate mainly from local road traffic and industrial activities, and sewage sludge application or waste water irrigation for soil. Seven sources of soil PAHs in Shanghai were identified by positive matrix factorization (PMF) model. The mean risk quotient (m-RQ) values indicated that there were medium to high ecological risks in 9.10% of soil samples, pyrene (Pyr), benzo[b]fluoranthene (BbF) and benz[a]anthracene (BaA) were the major ecological risk drivers under agricultural use. The cancer risk (CR) values were within the acceptable range at 35.7%, 35.1% and 31.2% of sampling sites for children, youths and adults, respectively. The total lifetime carcinogenic risk (TLCR) values at 57.8% of sampling sites were within the acceptable range. Overall, cancer risks of soil PAHs in all sampling sites in the studied area were below the highest acceptable risk, suggesting that soil PAHs are unlikely to pose a significant cancer risk for population based on ingestion, dermal contact and inhalation exposure pathways.

Seasonal variability of microbial biomass phosphorus in urban soils

Urban soils have been formed through human activities. Seasonal evaluation with time-control procedure are essential for plant, and activity of microorganisms. Therefore, these processes are crucial in the urban area due to geochemical changes in the past years. The purpose of this study was to investigate the changes of content of microbial biomass phosphorus (P) in the top layer of soils throughout the season. In this research, the concentration of microbial biomass P ranged from 0.01 to 6.29mg·kg−1. We used single-factor repeated-measure analysis of variance to test the effect of season on microbial biomass P content of selected urban soils. We found no statistically significant differences between the concentration of microbial biomass P in the investigated urban and sub-urban soils during the growing season. This analysis explicitly recognised that environmental urban conditions are steady. Specifically, we have studied how vegetation seasonality and ability of microbial biomass P are useful for detecting quality deviations, which affect the equilibrium of urban soil. In conclusion, seasonal variability of the stringency of assurance across the different compounds of soil reveals, as expected, the stable condition of the urban soils. Seasonal responses in microbial biomass P under urban soil use should establish a framework as a reference to the activity of the microorganisms.

Speciation of Cr, Cu, Ni and Zn in soils irrigated with contaminated waters: A case study of agricultural soils from the plain of Saiss (Fez, Morocco)

The excessive input of heavy metals into agricultural soils has become one of the most important concerns in the third world cities all over the world. The contamination of agricultural soils can affect the health of people living in agricultural areas and the surrounding ecosystems. The current study was conducted to assess the quality of urban and suburban soils of the City of Fez (Morocco), which are irrigated by waters enriched by heavy metals. The main objective was to define the distribution and the mobility of heavy metals in different soil compartments using the method of sequential extractions. The samples were also investigated for mineralogy using X-ray diffraction. The identified minerals were mainly composed of quartz, carbonate and clay minerals. Smectite and mixed-layer (chlorite-vermiculite and mica-smectite) are by far the most abundant clay minerals in all soils. The study of the availability and distribution of heavy metals (Cr, Cu, Ni, Pb and Zn) in urban soils, allowed us to observe a total content of Cr in the Oued Fez soils which is lower than the contents in the Oued Sebou soils. The Cu and Zn contents are low in Oued Sebou. Despite the Oued Fez input; the contents of these elements in the confluence do not increase. Sequential extractions completed the study of the potential mobility of heavy metals in different fractions of the soil. Indeed, this has allowed us to show that Cr, Cu, Ni and Pb are mostly related to the residual fraction; they are therefore theoretically little mobile; while Zn is practically related to the metals oxides fraction and exchangeable phase, respectively, in soils (FEZ1, FEZ2, SEBup) and (SEBdown, SEBconf), therefore the Zn is potentially mobile.

Comparison on soil carbon stocks between urban and suburban topsoil in Beijing, China

The urban population and urbanized land in China have both increased markedly since the 1980s. Urban and suburban developments have grown at unprecedented rates with unknown consequences for ecosystem functions. In particular, the effect of rapid urbanization on the storage of soil carbon has not been studied extensively. In this study, we compared the soil carbon stocks of different land use types in Beijing Municipality. We collected 490 top-soil samples (top 20 cm) from urban and suburban sites within the Sixth Ring Road of Beijing, which cover approximately 2400 km2, and the densities of soil organic carbon (SOC), soil inorganic carbon (SIC), and total carbon (TC) were analyzed to determine the spatial distribution of urban and suburban soil carbon characteristics across seven land use types. The results revealed significant differences in soil carbon densities among land use types. Additionally, urban soil had significantly higher SOC and SIC densities than suburban soil did, and suburban shelterbelts and productive plantations had lower SIC densities than the other land use types. The comparison of coefficients of variance (CVs) showed that carbon content of urban topsoil had a lower variability than that of suburban topsoil. Further findings revealed that soil carbon storage increased with built-up age. Urban soil built up for more than 20 years had higher densities of SOC, SIC and TC than both urban soil with less than 10 years and suburban soil. Correlation analyses indicated the existence of a significantly negative correlation between the SOC, SIC, and TC densities of urban soil and the distance to the urban core, and the distance variable alone explained 23.3% of the variation of SIC density and 13.8% of the variation of TC density. These results indicate that SOC and SIC accumulate in the urban topsoil under green space as a result of the conversion of agricultural land to urban land due to the urbanization in Beijing.

北京城市绿地表层土壤碳氮分布特征研究

Urbanized land cover and urban populations in China both have increased markedly since 1980 s. The rapid and massive urbanization has resulted in widespread ecological and environmental consequences from local to regional and national scales. To alleviate the negative impacts of urbanization and make our cities more sustainable,it is important to understand how urbanization affects biogeochemical cycles,particularly C and N dynamics. So far,however,understanding of urban soil biogeochemistry is rather limited,and more research is urgently needed. In this study,we collected 490 topsoil samples( 0—20cm) from different types of green space in urban and suburban area within the sixth-ring road range of Beijing,China. We analyzed concentration and density of soil organic carbon( SOC),inorganic carbon( SIC),total carbon( TC),and total nitrogen( TN),in order to explore the characteristics of the spatial distribution of carbon and nitrogen in the top layer of urban soils. The results showed that urban soils had higher SOC and SIC contents than suburban soils,and soil carbon content varied significantly between different land uses. The roadside tree pit soils had significantly higher SOC,SIC and TC density than other land-use type,and differences in SOC content among other types were not significant. SIC densities of residential,institutional,parks and transportation soil were significantly higher than those of suburban forests,nurseries,and orchards. For urban sites,roadside tree pit had highest SOC,SIC,and TC density,whereas park had lowest SOC,SIC,and TC. The difference in SOC between different land use were not significant. For suburban sites,roadside tree pit also had the highest SOC,SIC,and TC. The differences in SOC and TC among other land cover types were not significant. Shelterbelt and productive plantations had lower SIC densities than other land cover types throughout the entire metropolitan. Comparing similar land cover types between urban and suburban sites,institutional and transportation had significant higher SOC than the same types in the suburban sites. Yet urban parks and roadside tree pits had slightly lower SOC than the similar types in the suburban area. Urban land cover types had higher SIC and TC than the same land cover types of the suburban sites. Significantly negative correlations existed among SOC,SIC and TC,as well as between these variables and distance from the urban core. In other words,SOC,SIC,and TC tended to decrease with increasing distance away from the urban core. This indicates that urbanization in Beijing has augmented the local soil carbon pool to some extent. No significant differences in soil TN were found between land cover types or between urban and suburban sites. But TN and C / N tended to decrease along the urban-rural gradient. Further studies are needed to clarify the effects of urbanization on soil nitrogen in the Beijing region.

Polycyclic Aromatic Hydrocarbons, Heavy Metals, and Genotoxicity of the Suburban Soils from Guangzhou, China

During the past few decades, urban and suburban developments have grown at unprecedented rates and extents with unknown consequences for ecosystem function. The problem of soil pollution as a result of the accelerating development of Guangzhou in China is becoming great concerns. In the present study, gas chromatograph coupled mass spectrometry (GC-MS), inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were employed to determine the 16 US Environmental Protection Agency (EPA) priority polycyclic aromatic hydrocarbons (PAHs) and the heavy metals (As, Cr, Cu, Pb, Cd, Hg, and Se) of soils collected from suburban areas of Guangzhou. The genotoxicity of these soils was screened with micronucleus (MN) assay in Vicia faba root cells. The concentrations of the pollutants in the soils were (dried weight): ΣPAHs (230.6–1263 ng·g−1), As (2282.6–36064 μg·kg−1), Cr (7109–64699 μg·kg−1), Cu (7047–56388 μg·kg−1), Pb (9675.9–93739 μg·kg−1), Cd (68.5–847.3 μg·kg−1), Hg (85.4–549.2 μg·kg−1), and Se (219.2–968 μg·kg−1), which fell in the moderately polluted range. However, six out of nine soil-exposed groups had a significant increases of MN frequencies observed in the V. faba root cells compared with the negative group (P < 0.05, P < 0.01), indicating that they had potential genotoxic risks. Bringing together the chemical analyses with the biological effects observed in this study, the genotoxic response could at a certain degree be explained by both the soil PAHs and heavy metals. Our results suggested that apart from chemical analysis, bioassays like the MN assay of V. faba root cells should also be included in a battery of tests to assess the eco-environmental risks of urban and/or urbanization in the developing areas on the soils.

Draft Genome Sequence of Ralstonia sp. Strain GA3-3, Isolated from Australian Suburban Soil

Ralstonia sp. strain GA3-3 is a hexachlorocyclohexane (HCH)-degrading bacterial strain isolated from suburban soil in Canberra, Australia. The genome of strain GA3-3 was sequenced to investigate its ability to degrade α-HCH. Here, we report the annotated genome sequence of this strain.

Background Soil Mercury: An Unrecognized Source of Blood Mercury in Infants?

Introduction: During the past four decades, mercury (Hg) research focused on fish consumption has explained less than 22% of Hg in human blood. One overlooked exposure pathway for infants and young children is the concentration of Hg in soils. Although 75% of the U.S. population lives in urban areas near industrial facilities, minimal data exist regarding the concentration and speciation of Hg in residential soils. Chronic exposure through ingestion of low concentrations of Hg in soils may explain a portion of the blood Hg levels noted in infants. Methods: Three relatively unexposed residential sites in a suburban community were selected. The primary route of contamination was atmospheric deposition. Soils were digested in a nitric acid-hydrofluoric acid solution and analyzed by cold vapor atomic absorption spectrophotometry. Measured concentrations of total Hg in local suburban soil samples were compared to levels measured in a national study of 27 remote and rural sites. The Al-Shahristani pharmacokinetic model, developed after the 1971 Iraqi Methyl Hg poisoning incident, was used to calculate the blood Hg concentration in a hypothetical year-old infant. Results: Soil samples contained Hg concentrations ranging from 0.01 to 0.24 ppmw. The distribution of Hg in the soil samples was non-linear and non-normal. The mean soil Hg concentrations at the three locations were 0.08, 0.05 and 0.08 ppm. Calculated blood Hg concentrations for a 10 kg, year-old infant due to ingestion of soil (200 mg/day) containing 0.2, 0.4 and 0.8 ppm Hg were 0.08, 0.17 and 0.26 μg/L, respectively. Conclusions: The pilot study data appear to support the hypothesis that chronic, low-level soil ingestion may be a significant source of Hg for infants. Further study is warranted.

Congener specific distribution and health risk assessment of polychlorinated biphenyls in urban soils

Polychlorinated biphenyls (PCBs) were primarily used in transformers and capacitors, lubricants, flame retardants, plasticizers, paint, carbonless papers, etc. These are capable of long-range atmospheric transport and have been designated as persistent organic pollutants by the Stockholm Convention. Due to their characteristic properties, PCBs are found worldwide in all environmental matrices (including human) and biota. Soils are usually considered to be the source as well as sink for environmental pollutants, with cumulative effects of long-range atmospheric transport and local sources. Around the world, comparatively higher concentrations of PCBs have been reported in urban soils than suburban or rural soils. Higher amount of PCBs in urban soils may cause toxicological health risks to urban residents through ingestion, inhalation and skin contact. This paper presents the PCB distribution in soils from Delhi, India, and exposure risk estimates for human health through soil ingestion. The concentration of &amp;Sigma;PCBs ranged between 1.08-100.67 ng g&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; (mean 21.16 ng g&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;&amp;plusmn;5.24 ng g&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;), which was much lower than the Canadian soil quality guideline value of 1.3 mg/kg or 1300 ng g&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;. Human health risk estimates through the soil ingestion pathway were made in terms of lifetime average daily dose (LADD), incremental lifetime cancer risks and non-carcinogenic hazard quotient (HQ). The LADD for Delhi adults and children was 3.02x10&lt;sup&gt;&amp;ndash;8&lt;/sup&gt; mg kg&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; d&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; and 1.57x10&lt;sup&gt;&amp;ndash;7&lt;/sup&gt; mg kg&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; d&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;, respectively, which corresponds to toxic equivalent quotients (TEQ) intake of 0.105 pg TEQ kg&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; d&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; (0.735 pg TEQ kg&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; week&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;) and 0.543 pg TEQ kg&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; d&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; (3.801 pg TEQ kg&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; week&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;), respectively. The estimated LADD for Delhi residents was lower than the acceptable intake values recommended by the World Health Organization (1 pg TEQ kg&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; d&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;), the European Commission (14 pg TEQ kg&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;;1 week&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;) and by the Japanese government (4 pg TEQ kg&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; d&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;). The probability of cancer risk ranges from 6.04x10&lt;sup&gt;&amp;ndash;8&lt;/sup&gt; (&amp;Sigma;PCBs) to 1.57x10&lt;sup&gt;&amp;ndash;5&lt;/sup&gt; (&amp;Sigma;TEQ) and 3.13x10&amp;ndash;7 (&amp;Sigma;PCBs) to 8.15x10&amp;ndash;5 (&amp;Sigma;TEQ) for adults and children, respectively, and was within acceptable ranges of 10&lt;sup&gt;&amp;ndash;6&lt;/sup&gt; to 10&lt;sup&gt;&amp;ndash;4&lt;/sup&gt;. The non-carcinogenic risk in terms of health HQ was 0.105 and 0.330 for adults and children, respectively, which was lower than the acceptable limit of 1. The study found lower concentrations of PCBs than guideline values and low health risk estimates through the soil ingestion pathway within acceptable levels, indicating a minimum risk for Delhi residents.

Spatial distribution and risk assessment of phosphorus loss potential in urban–suburban soil of Lishui, China

Abstract Urban and suburban soil phosphorus (P) pools have a great impact on environmental quality. There is a critical need for a practical indicator of the potential for P movement from urban and suburban soil to surface waters. A total of 126 surface soil samples were collected from urban and suburban areas of a typical developing city (Lishui, China). The different P extraction solutions were used to predict P loss potential from the soil. For total P, over 50% of the samples were higher than the background value (661 mg kg− 1). For Olsen-P, 78.4% samples were above a recommended optimum value for plant growth (20 mg kg− 1). These results indicated an enrichment of P in urban and suburban soil, which could be attributed to anthropogenic sources. A split-line model related environmentally important CaCl2‐extractable P (CaCl2‐P) to Olsen-P, and the Mehlich 3 degree of phosphorus saturation (DPSM3) was used to predict the threshold values for P release. The change points for Olsen-P and DPSM3 are 92 mg kg− 1 and 23.6%, respectively. The area of P loss risk index was mapped using the geographic information system (GIS) based on the risk classification. The spatial distribution map obtained clearly showed that the region of high P loss risk was mainly distributed in the old and central urban region and northeast edge of the studied area. A phosphorus loss indicator combined with GIS would be helpful for the city government to best predict and manage P loss in the course of urban sprawl.

Distribution of major elements and trace metals as indicators of technosolisation of urban and suburban soils

Can geochemical characteristics indicate the human impact on soil formation (technosolisation) for urban and suburban soils? This question is assessed for the city of Marrakech located in one of the main agricultural areas of Morocco and characterized by a very rapid rate of expansion. The aim of this work is to assess geochemical properties of surface horizons of urban and suburban soils and to compare them with land use types. Fifty-eight surface soil samples were collected in different sectors of the city with different land use histories. As land use can be defined as the human use of land, these sampling sites were selected according to the current human activity (e.g., residential districts, agriculture, market-gardening, traditional, or industrial activities) and according to the superposition of the land use over time. All samples were air-dried, disaggregated, homogenized, and then sieved through a 2-mm mesh. Major elements and trace metals were measured in the soil using X-ray fluorescence spectroscopy. For technical limits, Cd was measured using atomic adsorption spectrometry. Urban and suburban soils of Marrakech present generally similar geochemical compositions for many elements. Siliceous (SiO2) compounds related to the parent material are dominant in these soils. However, the significant concentrations of P2O5 and CaO, measured in some of the urban soils studied, can be attributed to anthropogenic inputs of phosphorus (P) and technic materials, mainly building materials composed of cement and gypsum (plaster). Soils collected from agricultural areas irrigated with urban wastewater and soils developed on rubbish dumps are the most contaminated by metals (e.g., Cu, Zn, and Pb). Therefore, the distribution of major and trace elements in soils underlines the considerable impact of urban land uses. Human activities determine the type of land use, impact the urban environment, and cause a wide spatial diversity of soil quality. The urban and suburban soils of Marrakech contain similar major element distributions except for strongly anthropised soils (soils developed on rubbish dumps and agricultural soils irrigated with urban wastewater). Unlike major elements, trace elements present systematically significantly higher concentrations in urban soils than those measured in control soils. In these conditions, the highest concentrations exceed international clean-up standards and are correlated with land use type. Phosphorus, Ca, and several heavy metals are proposed as indicators of human impacts on soil characteristics in urban and suburban environments.

Diversities of phthalate esters in suburban agricultural soils and wasteland soil appeared with urbanization in China

The distribution of six priority phthalic acid esters (PAEs) in suburban farmland, vegetable, orchard and wasteland soils of Tianjin were obtained with gas chromatography-mass spectrometer analysis in 2009. Results showed that total PAEs varied from 0.05 to 10.4 μg g−1, with the median value as 0.32 μg g−1. Di-(2-ethylhexyl) phthalate and di-n-butyl phthalate are most abundant species. PAEs concentrations for the four types of soils exhibited decreasing order as vegetable soil > wasteland soil > farmland soil > orchard soil. PAEs exhibited elevated levels in more developed regions when compared with other studies. The agricultural plastic film could elevate the PAEs contents in soils. Principal component analysis indicated the emission from cosmetics and personal care products and plasticizers were important sources for PAEs in suburban soils in Tianjin. The higher PAEs contents in wasteland soils from suburban area should be paid more attention owing to large amounts of solid wastes appeared with the ongoing urbanization.

Assessment of Pesticide Pollution in Suburban Soil in South Shenyang, China

In this study, 35 representative farmland soil samples from suburban areas in south Shenyang, the capital city in Liaoning province, China, were collected to evaluate the pollution of 114 pesticides. Surface soil samples were air-dried and sieved. Ultrasonic extraction was used for pesticides preparation prior to analysis with gas chromatography-mass spectrometry. The total concentrations of tested pesticides in the area ranged in 0-51.32ng/g and the average of concentrations was 6.86ng/g. Six pesticides, including butachlor(with detect frequency 71.4%), p,p'-DDE (88.6%), p,p'-DDT (77.1%), o,p'-DDD (82.9%), hexachlorobenzene (88.6%) and δ-HCB (77.1%), were detected most frequently. It indicated that DDTs (N.D.-40.25ng/g) and HCHs (N.D.-42.79ng/g) were the predominant pesticide pollutants in soil because of their long term persistence. On the contrary, most of organophosphorus pesticides, pyrethroids and carbamates were not detected. Spatial variation of six pesticides with high detection frequency (>70%) in soil was illustrated. Pollution levels, characteristics and the possible sources were also discussed. The data were helpful to figure out the pollution of the pesticides and could be further used to evaluate the health risk associated with food safety.

Research on the Soil Pollution and Control of Pb, Cd and Cr in Taiyuan Suburb

The rapid population growth in Taiyuan, the ever-increasing industrial production and the never-ending expansion of the city have led to the serious heavy metal pollution of the soil, the deterioration of the soil fertility, the decrease of the grain output and the decline of grain quality and thus severely influencing the environmental quality and obstructing the sustainable economic development. The paper measures the content of such heavy metals as Pb、Cd、and Cr by Tessier's sequential extraction procedure in different depths of Taiyuan suburban soil, then determines the existing forms of these metals in the soil, discusses the factors influencing the forms of the heavy metals and their migration and transformation, probes into the ecological influence of the heavy metal pollution of soil, and finally the writer puts forward some measures to prevent from such pollution.

Contamination and distribution of heavy metals in urban and suburban soils in Zhangzhou City, Fujian, China

The urban environment is of growing concern as its continued population increase in China. Due to the urbanization and industrialization, heavy metals have been continuously discharged into the soil recently, and creating the anthropogenic contamination. This study investigated heavy metals contamination in urban and suburban soils in Zhangzhou City, Fujian, China. Multivariate analysis and geographical information system technology were employed in source identification and contamination assessment of heavy metals in the city soils. The survey results indicated that the urban soils were contaminated by heavy metals, especially by Hg, Cd and Pb. The multivariate analysis demonstrated that the distribution of Cu, Zn, Cr and Ni was controlled by pedogenesis, Cd and Pb had been disturbed by industrialization in some urban locations, and Hg was mainly influenced by the hot-spring in some urban park sites. The distribution of heavy metals and soil pollution index suggested the soils of Zhangzhou City have been affected by human activities.

Spatial distribution, source identification and affecting factors of heavy metals contamination in urban–suburban soils of Lishui city, China

An investigation on spatial distribution, possible pollution sources, and affecting factors of heavy metals in the urban–suburban soils of Lishui city (China) was conducted using geographic information system (GIS) technique and multivariate statistics. The results indicated that the topsoils in urban and suburban areas were enriched with metals, such as Cd, Cu, Pb, and Zn. Spatial distribution maps of heavy metal contents, based on geostatistical analysis and GIS mapping, indicated that Cd, Cr, Cu, Mn, Ni, Pb, and Zn had similar patterns of spatial distribution. Their hot-spot areas were mainly concentrated in the densely populated old urban area of the city. Multivariate statistical analysis (correlation analysis, principal component analysis, and clustering analysis) showed distinctly different associations among the studied metals, suggesting that Cr, Cu, Ni, Pb, Cd, and Zn had anthropogenic sources, whereas Co and V were associated with parent materials and therefore had natural sources. The Cd, Cr, Ni, Pb, and Zn contents were positively correlated with soil organic matter, pH, and sand content (p < 0.01). It is concluded that GIS and multivariate statistical methods can be used to identify hot-spot areas and potential sources of heavy metals, and assess soil environment quality in urban–suburban areas.

A numerical and field investigation of underground temperatures under Urban Heat Island

This paper introduces a simplified model for underground temperature prediction in summer hot weather. The data of 14 observation sites show that the surface temperature curves are close to trapeziums, and surface temperatures are related to air temperatures. Therefore, approximated temperature trapeziums that are determined by high- and lowest air temperatures can be used to simulate the underground temperature variation. Two observation sites respectively in the urban and suburban areas were used as examples. Good agreement was obtained between simulated- and measured temperatures. Measured data indicate the average temperature under urban concrete surface is 3.70 °C greater than that of suburban bare surface. The deviation is due to the heat urban environment effect and different surfaces effect, which are about 1.68 °C and 2.02 °C, respectively. Combined with soil volumetric water content ( w v), ‘Heat’ Islands associates with ‘Dry’ Islands, which means urban soil moisture is lower than suburban soil moisture (13.9%). According to the variation of w v and temperature deviation graphs, Urban Heat Island, ground surface types and rainfall are important factors that influence the underground soil moisture and temperatures.