[Distribution Characteristics and Risk Assessment of Phthalic Acid Esters in Agricultural Products Around the Pearl River Delta. South China].

In order to investigate and assess the distribution of pathalic acid easters (PAEs) in agricultural products from typical areas of the Pearl River Delta, South China, 131 agricultural products were sampled for determination of 6 PAEs priority pollutants classified by the U. S. EPA by GC-FID. The results showed that the total contents of the PAEs (sigma PAEs) in agricultural products samples ranged from nd to 79.86 mg x kg(-1) and the mean value was 2.84 mg x kg(-1), with the detected ratio of 98.5%. The average concentrations of sigma PAEs in different types of agricultural products were ordered by vegetables (3.03 mg x kg(-1)) > rice (2.52 mg x kg(-1)) > fruits (1.26 mg x kg(-1)). The mean concentration of PAEs distributed in the four typical cities of the Pearl River Delta, and decreased in the sequence of Zhuhai (6.53 mg x kg(-1)) > Dongguan (2.59 mg x kg(-1)) > Huizhou (1.53 mg x kg(-1)) > Zhongshan (1.12 mg x kg(-1)). Di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DnOP) contributed more than 90. 8% of the total PAEs in samples, and were the main components of PAEs in agricultural products from the Pearl River Delta, with higher percentage contents and detected ratio. Meanwhile, the average concentrations of sigma PAEs in cabbage mustard, lettuce occurred in Zhuhai and Dongguan cities, followed by lettuce and leaf lettuce in the corresponding DEHP from Zhuhai city, both exceeded the suggested standards in U.S.A. and Europe and were of high health risk. There were significant differences among 14 various vegetables in the contents of the 6 PAEs compounds, and the sigma PAEs contents in cabbage mustard and lettuce as part of leafy vegetables were higher than those in other vegetables, while the lowest were detected in flowering cabbage and edible amaranth. Therefore, the type of vegetables and its growing environment exposed to the atmosphere and soil were the main factors that significantly affected their accumulation of PAEs concentrations.

Assessment of organochlorine pesticide contamination in relation to soil properties in the Pearl River Delta, China.

High levels of organochlorine pesticides (OCPs) such as hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) have been found in soil of the Pearl River Delta (PRD), attributable to high pesticide application in this area. Consequently, the occurrence and environmental effect of HCHs and DDTs in the PRD have attracted considerable attention. However, study focusing on the influence of potential factors such as soil property on the environmental fate of HCHs and DDTs in the PRD has been rare. The present study aimed to investigate the impact of soil physiochemical properties on the distribution patterns and fate of soil HCHs and DDTs on a large spatial scale. Levels of HCHs (sum of α-, ß-, γ- and δ-HCH) and DDTs (sum of 1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane (p,p'-DDT), 1,1-dichloro-2,2-bis-(p-chlorophenyl)ethane (p,p'-DDD), and 1,1-dichloro-2,2-bis-(p-chlorophenyl)ethylene (p,p'-DDE)) in 151 soil samples covering all areas of the PRD and physiochemical parameters related to soil properties including pH, total organic carbon (TOC), total Fe (TFe), DCB-Fe (DFe), amorphous-Fe (AFe), complexed-Fe (CFe), total Mn (TMn), DCB-Mn (DMn), amorphous-Mn (AMn), complexed-Mn (CMn) and cation exchange capacity (CEC) were determined. The residual levels of HCHs and DDTs in soils of the present study, which are mainly controlled by soil TOC and CFe content and varying spatially with land use types, may potentially pose ecological risk to plants and animals. On the other hand, transformation of soil HCHs may be affected by pH and DDT transformation correlated significantly with AFe and CFe. Currently, soil has become an important secondary source of OCPs and the re-emission potential of OCPs in soil was mainly affected by soil OCP concentrations and land use types.

The concentrations, distribution and sources of PAHs in agricultural soils and vegetables from Shunde, Guangdong, China.

The concentrations, distribution and sources of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in 30 agricultural soil and 16 vegetable samples collected from subtropical Shunde area, an important manufacturing center in China. The total PAHs ranged from 33.7 to 350 microg/kg in soils, and 82 to 1,258 microg/kg in vegetables. The most abundant individual PAHs are phenanthrene, fluoranthene, chrysene, pyrene and benzo(b)fluoranthene for soil samples, and anthracene, naphthalene, phenanthrene, pyrene and chrysene for vegetable samples. Average vegetable-soil ratios of total PAHs were 2.20 for leafy vegetables and 1.27 for fruity vegetables. Total PAHs in vegetable samples are not significantly correlated to those in corresponding soil samples. Principal component analyses were conducted to distinguish samples on basis of their distribution in each town, soil type and vegetable specie. Relatively abundant soil PAHs were found in town Jun'an, Beijiao, Chencun, Lecong and Ronggui, while abundant vegetable PAHs were observed in town Jun'an, Lecong, Xingtan, Daliang and Chenchun. The highest level of total PAHs were found in vegetable soil, followed by pond sediment and "stacked soil" on pond banks. The PAHs contents in leafy vegetables are higher than those in fruity vegetables. Some PAH compound ratios suggest the PAHs derived from incomplete combustion of petroleum, coal and refuse from power generation and ceramic manufacturing, and paint spraying on furniture, as well as sewage irrigation from textile industries. Soil PAHs contents have significant logarithmic correlation with total organic carbon, which demonstrates the importance of soil organic matter as sorbent to prevent losses of PAHs.

[Distribution of phthalic acid esters in agricultural soils in typical regions of Guangdong Province].

To understand the distribution characteristics of phthalic acid esters (PAEs) in agricultural soils in typical regions of Guangdong Province, surface soil (0-20 cm) samples were collected, and the concentrations of 6 PAEs were determined by gas chromatography. The results showed that the total concentration of the PAEs (sigma PAEs) ranged from not detected to 25.99 mg x kg(-1), and was < or = 1.00 mg x kg(-1) in 92.8% of the samples. The sigma PAEs differed with land use types and regions, and decreased in the sequences of paddy soil > banana soil > vegetable soil > sugarcane soil > orchard soil, and Dongguan > Shantou > Shunde > Zhanjiang > Zhongshan > Zhuhai > Huizhou. Among the test PAEs, DEHP had the highest detection rate (85.1%), DnBP had the highest concentration (not detected to 17.51 mg x kg(-1)). Comparing with the corresponding control limits of soil PAEs in USA, all test PAEs except DnOP were exceeded the limits to some extent, and DnBP, DMP and DEP exceeded seriously, indicating that the agricultural soils in the typical regions of Guangdong Province were contaminated by PAEs.

[Source and distribution characteristics of polycyclic aromatic hydrocarbons in agricultural soils in the Pearl River Delta].

260 samples of surface agricultural soils (0-20 cm depth) were collected in the typical areas of Pearl River Delta from October 2002 to November 2005. The concentrations of polycyclic aromatic hydrocarbons (16 US EPA priority PAHs) in the collected soil samples were determined by gas chromatography equipped with a mass spectrometry detector (GC-MS). The results showed that the concentrations of Sigma PAHs in the collected soil samples ranged from 3.3 to 4,079.0 ng x g(-1) with the average concentration of 224.2 ng x g(-1). PAHs in the collected samples were dominated by its 3-ring and 4-ring members. There were the higher concentrations of Sigma PAHs in the collected samples of urban sites than those of remote sites. The concentrations of PAHs in the collected samples related to different land use types the order: vegetable soils > paddy soils > banana soils > orchard soils > sugarcane soils. According to the distributions of fluoranthene/pyrene, 2 + 3 ring and 4 ring PAHs in these regions, it is supposed that the major contribution to the pollution of PAHs in these typical areas might be the incomplete combustion of fossil fuel. Compared with those in other national or international regions, the concentrations of Sigma PAHs in these typical regions were moderate.

Spatial distribution of heavy metals of agricultural soils in Dongguan, China.

Distribution and speciation of heavy metals of agricultural soils(85 surface soil samples and 4 soil profiles) in Dongguan were investigated, while total Cr, Cu, Ni, Pb, Zn(abbreviated as Cr, Cu, Ni, Pb, Zn) and available Cu, Zn(Av-Cu, Av-Zn) were analyzed by a flame absorption spectrophotometer(AAS), and total Cd(Cd) was analyzed using graphite furnace AAS. The content of Cd, Cu and Ni was partially much more than the second grade of GB15618-1995 even though the mean contents of all heavy metal were less than the threshold value of the second grade and only the mean content of Pb was more than the value of national background. Results of descriptive statistic showed that the mean content of heavy metals should depend on land utilization and spatial location at some extent. The heavy metal contents were higher in the Southwest and Northwest than in the Central. In addition, the mean contents of Zn and Pb in Dongguan paddy soils were significantly higher than those of Pearl River Delta(PRD) and Taihu Lake region(TLR). Correlation analyses indicated that there existed significant correlation between Cr and Ni in orchard soils, and among Zn, Cd and Cu, between Av-Cu and Cu, between Av-Zn and Cr, Ni, pH value in vegetable soils, and a weak relationship between Cd, Cu and Pb, between Av-Zn and Zn. Principal component analyses(PCA) showed that the order of importance should be Zn > Pb > Cr > Ni > Cu.