Human body may be directly exposed to heavy metals in urban soils through oral ingestion, dermal contact, and inhalation of soil particles. A total of 170 topsoil samples were collected from the ...urbanized area of Dongguan, China. Concentrations of As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V, and Zn in soils were measured to calculate enrichment factors (EFs), pollution indexes (PIs), carcinogenic risks (CRs), and hazard indexes (HIs) of these elements. The mean concentrations of every element in urban soils of Dongguan are lower than both the soil environmental quality standards of China and the Canadian soil quality guidelines. However, concentrations of Cd, Cu, Ni, and Zn have increased slightly in the past 20years. Slight contamination was observed in some samples for all heavy metals according to the Chinese soil quality standards, and the element of As may be the most important contaminant. Furthermore, the element of As may pose both carcinogenic and non-carcinogenic risks to human health. Oral ingestion and inhalation of soil particles are the main exposure pathways of As to the human body. This study may provide a scientific basis for strategies to protect human health in urban areas.
•Cd, Cu, Ni and Zn increased in the soils over the past 20years.•Despite slight contamination of those metals, urban soils were relatively clean.•Arsenic in urban soils is the most harmful contaminant to human health.•Oral ingestion and inhalation are the main exposure pathways of arsenic for humans.
One hundred and four surface samples and 40 profiles samples in agricultural soils collected from Huizhou in south-east China were monitored for total contents of 8 heavy metals, and analyzed by ...multivariate statistical techniques and enrichment factor (EF), in order to investigate their origins. The results indicate that the concentrations of Cu, Zn, Ni, Cr, Pb, Cd, As and Hg in soils are 16.74, 57.21, 14.89, 27.61, 44.66, 0.10, 10.19 and 0.22mg/kg, respectively. Compared to the soil background contents in Guangdong Province, the mean concentrations of Hg, Cd, Zn, Pb and As in soil of Huizhou are higher, especially Hg and Cd, which are 2.82 and 1.79 times the background values, respectively. Cr, Ni, Cu, partially, Zn and Pb mainly originate from a natural source. Cd, As, partially, Zn mainly come from agricultural practices. However, Hg, partially, Pb originate mainly from industry and traffic sources.
► The concentrations of Hg and Cd are high in agricultural soil of Huizhou. ► Cr, Ni, Cu, partially, Zn and Pb mainly originate from a natural source. ► Cd, As, partially, Zn mainly come from agricultural practices. ► Hg, partially, Pb originate mainly from industry and traffic sources.
To investigate the effects of substituent groups on the reductive degradation of azo dyes by zerovalent iron, Orange I, Orange II and Methyl Orange were selected as the model azo dyes with different ...substituent groups. The results showed that Orange I, Orange II and Methyl Orange could be effectively reduced by Fe
0, and the degradation of Orange I and Orange II could be described by the first-order kinetic model, while the degradation of Methyl Orange could be described by the zeroth-order kinetic model. The initial degradation rate followed the order as Orange I
>
Orange II
>
Methyl Orange under the same experimental conditions owing to the substituent effects. The degradation kinetic constants of Orange I and Orange II increased with the increase in the Fe
0 dosage, and with the decrease in the initial pH value and their initial concentration, while that of Methyl Orange increased with the decrease in the initial pH value, and with the increase in the Fe
0 dosage and their initial concentration. The results of high-performance liquid chromatography (HPLC)–mass spectra (MS) showed that sulfanilic acid was the same intermediate, while the second intermediate was 1-amino-4-naphthol for Orange I, 1-amino-2-naphthol for Orange II, and
p-dimethylaminoaniline for Methyl Orange. It was suggested that the larger conjugated π system of naphthalene rings of Orange I and Orange II for the delocalization of the nonbonding electron pairs of substituents and nitrogen in the azo bond might be favorable for the degradation of Orange I and Orange II, compared with the structure of Methyl Orange. The higher degradation rate of Orange I might be ascribed to its effective electron delocalization and favorable position effects, compared with Orange II. It should be concluded that the reductive degradation of azo dyes by zerovalent iron strongly depends on the effect of substituent groups.
Aims The overall goal of this study was to examine the spatial and temporal patterns of C storage from 1992 to 2002 in forest ecosystems in Guangdong, China. Methods We used 2237, 2103, and 1978 plot ...data from three continuous forest inventory in 1992, 1997, and 2002, respectively, four TM images and one soil survey data in Guangdong to examine the spatial and temporal patterns of C storage in forest ecosystems during 1992-2002. The uncertainty analysis of forest C storage in Guangdong in 1992 and 2002 was also conducted to provide the range of estimations. Results The forest coverage percent in Guangdong increased from 37.1 % in 1992 to 57.2 % in 2002 while the total forest C storage in Guangdong increased from 144.73 ±6.20 Tg in 1992 to 215.03 ± 8.48 Tg in 2002. The order of average forest biomass C storage increase during 1992-2002 among the four regions is Western Guangdong (GW)>Eastern Guangdong (GE)>the Pearl River Delta (PRE)>Northern Guangdong (GN). The factors including tree species and altitude and slope aspect can explain 58-67 % variation of Veg C storage multiple regression model in Guangdong. However, the multiple regression model for SOC storage can only explain about 18-39 % variation of SOC storage in Guangdong. Total ecosystem C is mainly determined by SOC storage. Conclusions The total forest C storage in Guangdong increased about 49 % from 1992 to 2002 partially due to the increasing forest coverage percent over the period. The spatial distribution of forest C storage in Guangdong was uneven and this pattern reflects differences in forest management and economic and social development. Future forest management should focus on the selection of tree species, management of forest stand structures and implementation of sustainable practices so that Veg C sequestration potentials can be maximized.
The adsorption behavior of 2-mercaptobenzothiazole onto organo-bentonite was investigated. Natural bentonite from Gaozhou in Guangdong Province, China was collected. Organo-bentonite was prepared by ...intercalation of cetyltrimethyl ammonium bromide into the natural bentonite. The physicochemical properties of the prepared organo-bentonite were characterized by X-ray diffraction, N2 adsorption-desorption isotherm and Fourier transform infrared spectroscopy. The results showed that montmorillonite is the main component of the natural bentonite. The basal spacing of the natural bentonite is 1.47 nm, which increased to 1.98 nm on intercalation with cetyltrimethyl ammonium bromide. Moreover, both the surface area and pore volume increased with intercalation. Clear CH2 stretching （3000-2800 cm-1） and scissoring （1480-1450 cm-1） modes of the intercalated surfactants were observed for organo- bentonite. Compared with the pseudo first-order kinetic model, the pseudo second-order kinetic model is more suitable to describe the adsorption kinetics of 2-mercaptobenzothiazole onto organo-bentonite. The adsorption capacity of 2-mercaptobenzothiazole onto organo-bentonite increased with increasing initial concentration of 2-mercaptobenzothiazole, but decreased with increasing adsorbent dosage. The adsorption isotherm of 2-mercaptobenzothiazole onto organo-bentonite fits well with the Langmuir model. The maximum adsorption capacity of organo-bentonite for 2-mercaptobenzothiazole was 33.61 mg/g, indicating that organo-bentonite is a promising adsorbent for 2-mercaptobenzothiazole.
Environmental magnetism has been widely applied to soil science due to its speediness, non-destructiveness and cost-effectiveness. However, the magnetic investigation of agricultural soil, so closely ...related to human activity, is limited, most probably because of its complexity. Here we present a magnetic investigation of 301 agricultural soil samples collected from the Pearl River Delta (PRD, 112°E–115°E and 22°N–24°N), China. The results showed that both low and high coercivity magnetic minerals coexist in agricultural soil. The values of concentration-dependent parameters, low-field susceptibility (χlf), anhysteretic remanence magnetization susceptibility (χARM), and saturation isothermal remanence magnetization (SIRM) were much higher in the PRD plain than in the surrounding areas. The S-ratio (S−300) showed a similar spatial pattern to the aforementioned parameters. By contrast, frequency-dependent susceptibility (χfd%) and χARM/SIRM were higher in the surrounding hilly and mountainous areas than in the PRD plain. Natural and anthropogenic factors such as parent material, soil type and cultivation methods play important roles in determining agricultural soil magnetic properties. Magnetic minerals were coarser grained and overall indicated higher concentrations in soils from river alluvium and deposited materials. Soils which had suffered long-term water submergence have the lowest magnetic mineral concentration, a result consistent with previous studies. The magnetic properties of agricultural soils are strongly influenced by cultivation methods. Other human activities, such as industrial development and concomitant emitted pollutants, might have had an additional impact on the magnetic properties of agricultural soil.
•Agricultural soil contains distinct coercivity phases of magnetic minerals.•Spatial distribution of magnetic parameters is of significant feature.•Magnetic properties are influenced by various natural and anthropogenic factors.•Industrial emission could have a potential effect on magnetic properties in soil.
There were several first-order kinetic equations used and cited by previous publications （Do,an et al., 2007; Eftekhari et al., 2010; Lagergren, 1898; Kannan and Sundaram, 2001;Ozcan et al., 2006）：
This study addresses several basic questions relating to the roles of badges and displays in establishing social structure in male Phrynocephalus vlangalii. Significant differences in body mass and ...condition were found between resident and floater males of P. vlangalii, and resident males engaged in tail curling and agonistic interactions more frequently than floater males. Frequency of tail curling was correlated negatively with body mass in floater males, but was not correlated with body mass and condition in resident males. Relative tail-tip badge size, relative belly patch size and relative tail length could significantly predict an individual's body mass, and body condition was positively correlated with relative tail length, suggesting that resident males may establish their social dominance by communicating their body mass and condition through frequent tail curling.
Polychlorinated biphenyls (PCBs) contamination in tropical and sub-tropical areas and the associated risks have attracted great concern. A total of 69 samples representing five distinct land types ...were collected to assess PCB concentrations in the Pearl River Delta (PRD), South China, including spatial distributions in soils of the area, the probable anthropogenic sources, and related potential risks. PCBs concentrations in soils of the PRD ranged from 0.3 to 202 ng g
−1
. More severe PCBs contamination was presented in the western part than in the eastern part of the PRD region. The PCBs were dominated by low-chlorinated biphenyls; however, the proportion of higher-chlorinated biphenyls was elevated with the influence of industrial activities. Principal component analysis indicated that PCBs contamination in soils of the PRD region was mainly associated with 1#PCBs, while 2#PCB and e-waste emission in South China also accounted for it partly, especially to the industrial activity severely impacted areas. Toxic equivalent (TEQ) of the dioxin-like PCBs in the soils indicated that higher risk of PCB contamination was presented in the Dongjiang River Valley (55 ng TEQ kg
−1
, on average) than in the Xijiang River Valley, and were mostly contributed by the congener of PCB126.
Many ecological hypotheses have been widely used to explain species richness variation across the globe. We investigated lizard species richness patterns in China, and identified areas of high ...species richness. Furthermore, we tested hypotheses concerning the relationships between lizard richness and environmental variables. A large data including 30,902 records of point locality data for 151 lizard species occurring in China were retrieved from Herpetology museums of CIB/CAS and other museums through HerpNET, and published sources, and then predicted distributions maps were generated using ecological niche modeling. We overlaid all species prediction maps into a composite map to describe species richness patterns. A multiple regression analysis using eigenvector-based spatial filtering (SEVM) was performed to examine the best environmental predictors of species richness. Richness peaked mainly in southern China located in the Oriental realm. Our best multiple regression models explained a total of 80.1% variance of lizard richness (r
2
= 0.801; F = 203.47;
P
< 0.001). Among related factors in shaping species richness distribution, the best environmental predictors of species richness were: frost-day frequency, elevation, vegetation, and wet-day frequency. Based on models selection, our results revealed that underlying mechanisms related to different ecological hypotheses might work together and best explain lizard richness in China. We are in an initial step to develop a large data set on species richness, and provide the necessary conservation implications from habitat loss. Additional studies that test species richness at different geographical scale are required to better understand the factors that may influence the species richness distribution in East Asia.
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