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Phytoremediation, as a green and effective in-situ remediation technology for heavy metal-contaminated soil, has attracted the attention of Chinese scholars and has resulted in a series of achievements over the past 20 years. In this study, the species characteristics, distribution of field discovery sites in various vegetation zones, habitat characteristics, habitat geological characteristics, and geochemistry of cadmium (Cd) of the Cd hyperaccumulators in China reported in the relevant literature from the past 20 years (from 2002 to 2021) were summarized by searching for related keywords. Finally, suggestions were proposed for the screening of new Cd hyperaccumulators. The results showed that a total of 45 species of Cd hyperaccumulators in China have been reported so far. In terms of plant species, they belonged to 22 families and 36 genera, among which Compositae with 14 species was the most abundant. There were 25 species discovered through the field investigation, which were mainly distributed in the subtropical broadleaf evergreen forest region of southern China. Additionally, the Cd hyperaccumulators discovered by field surveys were mainly found in high Cd-concentrated soils surrounding lead-zinc mines. In conclusion, abundant plant resources, high concentrations of heavy metal soils, and long-term domestication jointly promoted the formation of hyperaccumulators. Therefore, the region with these three points could be considered a high probability region for the presence of hyperaccumulators, and the screening of hyperaccumulators could be carried out around this. We proposed that the screening of new hyperaccumulators can be carried out through the following six steps:the identification and investigation of high probability areas, the enrichment capability test, the enrichment capability test in low concentration levels, the enrichment capability test between different ecotypes, the succession of enrichment capability, and the test of remediation proficiency.

Intercropping a Cd-accumulator with economically valuable crops is common in slightly or moderately Cd-polluted farmland soils. A field experiment was conducted to evaluate the effects of water-soluble chitosan (WSC) on the growth and Cd uptake of the Cd-accumulator Hylotelephium spectabile and soybean ( Glycine max ) during a co-cultivation in Cd-contaminated agricultural soil (WSC, 0 and 10 g·m -2 ). The results indicated that soybean yields were highest in response to the intercropping and WSC treatment. The results from the field trials generally showed that intercropping and WSC treatments significantly decreased Cd concentrations in inedible parts of soybean by 42.9-72.1% (except for stems), in the meantime, increased 95.8%-334.6% in shoot and root tissues of H. spectabile compared with the control ( p  < 0.05). The data revealed that Cd uptake was highest for H. spectabile during the intercropping and WSC treatment. The application of WSC in the intercropping system significantly increased the uptake of Cd by H. spectabile , but not by soybean. The findings of this study suggest that combining an intercropping system with a WSC treatment may be better for remediating Cd-contaminated soils than other methods involving the growth of a single hyperaccumulator.

In order to explore the distribution characteristics of heavy metal contamination of farmland soil surrounding Luancheng town, Shijiazhuang City, Henan province, the concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the surface soil and crops were determined and assessed. The principal components were also analyzed for source apportionment. The heavy metal concentrations in crops were further detected, and the non-carcinogenic health risks in the study area were evaluated using the probabilistic risk assessment method, as to provide a theoretical basis for the treatment, prevention, and control of heavy metal pollution in farmland soil in Luancheng. According to the results, ω (Cd), ω (Cr), ω (Cu), ω (Pb), and ω (Zn) in the soils were 0.06-1.08, 22.14-473.47, 12.83-150.74, 10.75-577.72, and 62.23-652.78 mg·kg -1 , which exceeded the standard with over-standard rates reaching 1.83%, 1.22%, 0.61%, 0.61%, and 1.22%, respectively. Further, Cd and Pb were transported into crops, in which Cd concentrations exceeded the standard in some corn samples, and Cd and Pb concentrations exceeded the standard in some wheat samples. The total non-carcinogenic health risks (TTHQ) to the human body caused by the consumption of heavy metals in corn grown in the study area were all less than 1, with no obvious negative effects, and TTHQ was higher than 1 in wheat, increasing the likelihood of negative impacts on the human body. With the influence of the distribution of pollution-related enterprises in the industrial zone, heavy metal concentrations were higher in the south, west, and middle directions of the study area. Among them, the study area soil was slightly contaminated by Cd (Level 1). Cd and Hg had a slight potential ecological risk (Level 2), whereas other heavy metals had low potential ecological risk (Level 1). In general, most of the surface cultivated soil was not obviously polluted by heavy metals in the study area. According to the PMF results and survey, we speculated that soil heavy metals mainly came from soil parent material (52.05%), artificial pollution sources (historical sewage irrigation and industrial manufacture) (32.98%), and atmospheric deposition (14.97%). To summarize, the study area should be divided into a priority protection category and safe utilization category. The input of pollution sources should be strictly controlled for the priority protection category, and alternative planting, rotating, and fallow should be implemented for the safe utilization category to reduce the risk of standard-exceeding agricultural products.

In order to explore the main controlling factors of Cd enrichment in rice under a geological high background in the Guangxi carbonate rock area, this study was based on rice grain-root soil samples from the carbonate rock areas in the southwest and north of Guangxi. Combined with diffusive gradients in thin films technology (DGT), the relationship between soil pH, organic matter, cation exchange capacity (CEC), DGT-Cd, and ω (rice-Cd)-BCF value in rice grains was analyzed and discussed. The main factors were determined by principal component analysis, and a quantitative model was established. The results showed that the average value of ω (soil-Cd) was 0.975 mg·kg -1 , and the over-standard rate was 33.33%; the average value of ω (rice-Cd) was 0.020 mg·kg -1 , and the average BCF value was 0.038, and the over-standard rate of Cd content in rice grains was 4.2%. The content of Cd in paddy soil was high, but bioavailability was low in the study area. The BCF value of rice grains in the study area was significantly negatively correlated with soil pH and cation exchange capacity at the level of 0.01, positively correlated with DGT-CD at the level of 0.01, and negatively correlated with organic matter at the level of 0.05. The results of principal component analysis showed that the total amount of Cd in the soil, pH, and DGT-Cd were the main factors affecting the accumulation of Cd in rice in the Guangxi carbonate rock area. Taking the total amount of Cd in the soil, pH, and DGT-Cd as variables, the fitting equation of BCF value of rice grains in the Guangxi carbonate rock region was established, and the determination coefficient of the model was 0.717, which could better predict the content of Cd in rice grains in this region.

A pot experiment was conducted to investigate the growth response and Cd accumulation characteristics among different populations of Hylotelephium spectabile in Cd-contaminated cinnamon soil (2.22 mg·kg -1 ) with the addition of different concentrations of NaCl. Results showed that the biomasses and Cd concentrations of H. spectabile showed significant differences among different populations under Cd alone or Cd-salt combined stress. Moreover, salt stress aggravated the growth inhibition of H. spectabile and the Cd concentrations in different H. spectabile populations showed a declining trend, which may be related to the salt-derived pH increase leading to a decrease in Cd bioavailability. In addition, the growth and Cd absorption responses of H. spectabile under salt stress were significantly different in the different populations. The shoot biomasses of the LN population were significantly higher than in other populations under different treatment, and showed no significant decrease with the addition of 1% NaCl when compared with the control treatment and the tolerance index remained 0.91. At the same time, the shoot Cd concentration of the LN population was significantly higher than in other populations under different treatments. The result may be attributed to the Cd accumulation and detoxification mechanisms in LN are prior than other populations that may also have important physiological mechanisms for tolerance of salt stress. In summary, although Cd uptake in H. spectabile decreased with salt stress, there were significant differences among different populations. LN populations accumulated 84.4 μg·plant -1 Cd in shoots with 2% NaCl addition, which was 48.4%-89.3% higher than in other populations. Therefore, H. spectabile, especially LN populations, is a good candidate for phytoremediation of Cd-contaminated saline soil.

In order to fully explore the spatial distribution of soil heavy metal contaminants in farmland soil surrounding a typical industrial area in Dakuai town, Xinxiang city, Henan Province, the concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn in the surface soil and within the soil profile were determined and assessed. The principal components were also analyzed for source apportionment to provide a theoretical basis for the control and prevention of heavy metal pollution. According to the results, the soils in the study area are severely contaminated by Cd and Cu and moderated contaminated by As due to the battery manufacture and Cu (e.g., pipe and wire) processing. The concentrations of Cd, Cu, and As in soils were (2.56±1.23) mg·kg -1 , (205.58±157.49) mg·kg -1 , and (15.27±4.14) mg·kg -1 , respectively, which exceeds standards by 100%, 89.44%, and 3.40%, respectively. Accounting for the influence of pollution sources, terrain, runoff erosion, and prevailing wind direction, all heavy metal concentrations were higher in the south direction, lower in the north direction. The concentrations of Cd and Cu in soil profile samples decreased with depth, with highest concentrations at the surface, indicating the strong effect of industrial activities. Arsenic concentrations varied little with soil depth due to its strong migration ability in alkaline soil, again suggesting an industrial source. Among them, the soil of study area was severely contaminated by Cd and Cu (Level 5). Cd poses a severe potential ecological risk (Level 5) and Cu poses a medium risk (Level 2) in the study soils, while other heavy metals show low potential ecological risk (Level 1). The order of the risk identified was Cd > Cu > Ni > As > Pb > Cr > Zn. In addition, the combined potential ecological risk of heavy metals in the target area is severe. The principal component analysis showed that the high As, Cd, and Cu contents are mainly derived from industrial areas. Therefore, it is urgent to remediate Cd and Cu soil contamination in this area and implement precautions to limit As contamination.

A field experiment with an orthogonally designed experiment L9(3 4 ) was designed to investigate the effect of different N, P, and K levels on plant growth and Cd uptake by Hylotelephium spectabile . The results showed that the biomass of H. spectabile significantly increased with the N application rate. The highest dry weight in the shoot occurred in the treatments with a high level of N (337.5 kg ·hm -2 ), which was 0.86-2.00 times higher than the value with no fertilizer treatment. The addition of K contributed to promoting the Cd absorption of H. spectabile , while no effect was observed when N and P were added. Consequently, NPK fertilizers contribute to increasing the Cd uptake of H. spectabile , and the N and K fertilizer play important role in plant growth and Cd absorption respectively. Moreover, the effect of fertilizers on Cd uptake of H. spectabile was in the order of N > K > P, which indicated that N fertilizer was the main factor for promoting the Cd phytoextraction efficiency of H. spectabile by increasing the biomass. Therefore, the application of high levels of N combined with moderate levels of P and K will be an effective approach to improve the Cd phytoremediation efficiency of H. spectabile by promoting its growth, and the Cd uptake can be increased by a factor of 0.9-2.2 compared to no fertilizer treatment condition.

To evaluate the safety of rice planting in cadmium geological anomaly areas, 41 natural soil, 479 paddy soil, and 432 rice samples were collected in southwestern Guangxi. The contents of Cd, Cu, Ni, and Zn and soil physical and chemical properties were measured. The single factor pollution index method ( P i ) was used to evaluate the degree of contamination of the sample, and correlation analysis were used to explore the main factors affecting the heavy metal content in rice. The results showed that ① soil pH of the paddy field was 6.8; the organic matter content was 39.00 g·kg -1 ; the risk screening value was based on the soil environmental quality standards for soil pollution risk control and control of agricultural land (GB 15618-2018), the exceeding standard rates of Cd, Cu, Ni, and Zn in soil were 60.75%, 2.09%, 0.83%, and 1.88%. ② The over-standard rates of Cd and Ni in rice were 9.03% and 4.39%, respectively. Considering straw as raw material for feed and organic fertilizer, the corresponding over-standard rates of Cd were 6.94% and 1.16%. ③ Correlation analysis showed that soil pH, organic matter, total heavy metal, and available content were the main factors affecting the content of heavy metals in rice. Cd and Ni in the study area all exhibited certain over-standard phenomena, and the low-accumulation rice varieties could be planted to reduce heavy metal content in rice.

Thermal desorption (TD) technology is the preferred treatment technology for treating soil contaminated by organic compounds. Under laboratory conditions, eggshell and plant ash were studied as additives during thermal desorption to further improve the soil thermal desorption efficiency and the quality of soil after thermal desorption. The results showed that temperature was still an important factor affecting the soil quality and removal efficiency of PAHs (polycyclic aromatic hydrocarbons). The efficiency of the thermal desorption of soil was significantly improved (from 91.7 to 96.6%) by adding two additives, and the agglomeration of the soil was alleviated to some extent according to the decreased amount of large soil particle (100-400 μm). Moreover, the TOC (total organic carbon) and CEC (cation exchange capacity) of the soil were increased. This work suggested that the addition of similar alkaline additives to the soil during thermal desorption might have a positive impact on both thermal desorption behavior and soil quality.

A hydroponic experiment was conducted to explore the differences in growth status and Cd accumulation characteristics of two Brassica napus L. cultivars (QY-1 and SYH) under different concentrations of cadmium (Cd) stress (0, 2, and 5 mg·L -1 ). The Cd subcellular compartmentalization and antioxidant enzyme activities were determined to elucidate the intrinsic mechanism of the differences in the Cd accumulation capacity between the two cultivars of Brassica napus L. Furthermore, field trials were conducted to further verify the differences in phytoremediation of the two cultivars. Results show that neither of the cultivars exhibited obvious growth inhibition under Cd stress. Under the 2 mg·L -1 Cd condition, there were no significant differences in shoot Cd concentrations between the two cultivars. Under 5 mg·L -1 Cd condition, however, the Cd concentrations in both shoot and root of SYH were significantly higher than that of QY-1, which increased by 32.05% and 99.57%, respectively. In addition, the bioconcentration factor (BCF) of the root in SYH is significantly higher than that of QY-1. The subcellular Cd distribution in leaves of the two cultivars of Brassica napus L. showed that, with an increase of Cd stress, Cd concentrations of heat stable protein (HSP) and metal-rich granule (MRG) fractions in leaves significantly increased by 143.69% and 118.91% for QY-1, and by 63.34% and 118.91% for SYH. Thus, the segregation of Cd in HSP and MRG, which was reported to be biological detoxified metal fractions (BDM), might play an important role in the detoxification of Brassica napus L. at a subcellular level under Cd stress. Moreover, the distribution of Cd in the cellular debris fraction might be another important factor contributing to the differences in Cd accumulation of the two Brassica napus L. cultivars, which was 4.41 times higher in SYH than in QY-1 under Cd stress. The results of the antioxidant enzyme activities of two Brassica napus L. cultivars showed that, under the 5 mg·L -1 Cd condition, the antioxidant enzyme system may represent an important detoxification mechanism for QY-1 to cope with stress induced by high concentrations of Cd, while SYH is more effective in reducing the toxicity of Cd by separation of Cd into BDM fractions. The results of the field trial confirmed that the Cd concentrations in the above- and underground parts of SYH were 2.34 and 1.43 times higher than in QY-1, respectively. Therefore, SYH possess a higher Cd phytoextraction capacity than QY-1, and might be a good candidate for the remediation of moderate and mildly Cd-contaminated farmland.

To investigate the levels of heavy metal Cd in paddy soils in high cadmium anomaly areas in Guangxi, and to assess their potential ecological risks to the environment. Through preliminary screening and detailed investigation, 912 pieces of soil samples from high-cadmium abnormal area were collected in multiple batches to determine the soil Cd content. The single-factor pollution index method and potential risk index method were used to control the Cd pollution degree of paddy soil. Potential risks were evaluated. The results showed that:① The average Cd values of natural soil, paddy soil, and dryland soil in the initial screening were 0.915, 0.591, and 0.593 mg·kg -1 , respectively. ② In the detailed investigation, the soil pH is 4.6-8.7, which is between acidic and weakly alkaline. If the Soil Environmental Quality Standard (GB 15618-2018) is used as the evaluation standard, the Cd of the soil sample in Pingguo County, Tiandong County, Long'an County, and Liucheng County is seriously exceeded, and the soil sample in the paddy field of Rongshui Country is not polluted. Based on the soil baseline value, the Cd in the soil samples of Tiandong County, Liucheng County, and Rongshui County were non-polluting. In the paddy soils of Tianyang County, Pingguo County, Tianxian County, Daxin County, Long'an County, and Rong'an County, the proportion of Cd in mild to moderate pollution was 4.2%, 3.7%, 14.9%, 2.6%, 7.1%, and 1.4%, respectively. ③ Cd in paddy soils of nine counties and cities presents different levels of potential ecological risks. The soil Cd of some paddy fields in Tiandeng County, Daxin County, and Long'an County was at a high ecological risk ratio of 4.3%, 2.6%, and 2.4%. The soil Cd of Tianyang County, Pingguo County, Rong'an County, and Liucheng County was medium-Middle and high potential risks. Tiandong County and Rongshui County are at low potential ecological risks. In conclusion, the overall Cd in the paddy soil of the study area is high, which may affect the safe planting of rice in the long-term. It will eventually pose a health threat to local residents and should be taken care of. It is recommended to carry out research on soil cadmium bioavailability and rice cadmium accumulation in the study area in order to assess its ecological risk and health risk more scientifically and reasonably.

To evaluate the remediation potential of Ageratum conyzoides L. on cadmium (Cd) contaminated farmland soil, the Cd-containing plants and root were collected and analyzed by field investigation, original pot experiment, and field experiment. The enrichment factor and removal rate of Ageratum conyzoides L. was calculated. The results showed that the maximum Cd content in the leaves of Ageratum conyzoide s L. growing in soil of different lead-zinc mines was 77.01 mg·kg -1 . In the high-concentration Cd soil treatment (T2), Cd content of the above-ground of Ageratum conyzoides L. was 69.71mg·kg -1 , and Cd enrichment coefficient was 6.09. In the low-concentration Cd soil treatment (T1), the enrichment characteristics of Cd ( Ageratum conyzoides L.) are consistent with the enrichment characteristics of Cd under high concentration conditions. Ageratum conyzoides L. exhibits stable accumulation characteristics for Cd. In the field experiment, the average Cd content of Ageratum conyzoides L. was 21.13 mg·kg -1 , and the enrichment coefficient was 6.93. The removal rate of the three planting Ageratum conyzoides L. per mu of soil using the Ageratum conyzoides L. to repair Cd contaminated soil was 13.2%-15.6%. The use of Ageratum conyzoides L. to repair Cd pollution in farmland has a good prospect for engineering application.

A hydroponic experiment was conducted to study the interaction of Cd and Zn affecting the root morphology and accumulation of Cd and Zn in Sedum aizoon . The results show that S. aizoon exhibits a high tolerance to single stress of Cd and Zn and the concentrations of Cd and Zn in the leaf, stem, and root of S. aizoon increase as the stress levels increase. A strong phytoextraction capacity in S. aizoon was also observed for the Cd concentration in the aboveground part reaching 133.0 mg·kg -1 . The combined stress of Cd and Zn has a greater effect on the growth of S. aizoon than single stress to which the root is more sensitive. The root length, surface area, root volume, and tips significantly decrease under combined stress of Cd and Zn; the effect on the tips is most significant. The low-level Zn application (10 mg·L -1 ) has a synergistic effect on the Cd accumulation in the shoot of S. aizoon because of the promotion of Cd translocation from root to shoot. However, the addition of Cd leads to a notable antagonism of the Zn absorption of S. aizoon . The concentration ratio of Zn and Cd also has a significant effect on the Cd uptake of S. aizoon . A high ratio promotes the Cd accumulation in the shoot, while the latter is inhibited by a low Zn/Cd ratio. Therefore, S. aizoon possesses a strong potential of Cd phytoextraction and can be applied for phytoremediation of Cd-contaminated soil, while the adjustment of the ratio of Cd and Zn in the growth medium will help to enhance the phytoremediation efficiency of S. aizoon .

Pot experiments were conducted to assess the effects of monoammonium phosphate (NH 4 H 2 PO 4 ) and citric acid (CA) on the arsenic uptake of Chinese brake fern (Pteris vittata L. in two typical arsenic-contaminated soils i.e. fluvo-aquic and brown) from Jiyuan (JY) City and Baoding (BD) City in Northern China. NH 4 H 2 PO 4 improved the biomass of P. vittata, whereas CA exerted no significant influence. NH 4 H 2 PO 4 and CA both increased the arsenic uptake of P. vittata by 6.08 and 2.72 times, respectively, in fluvo-aquic soil and 4.20 and 2.52 times, respectively, in brown soil. Moreover, CA, but not NH 4 H 2 PO 4 , promoted the transfer of arsenic from the root to the frond. NH 4 H 2 PO 4 and CA increased Olsen's arsenic contents in the soils and promoted the transformation of residual arsenic and crystalline Fe/Al oxide-bound arsenic to nonspecifically and specifically sorbed arsenic. This study proved that P. vittata can be used in Northern China. Applying NH 4 H 2 PO 4 and CA can enhance the effectiveness of P. vittata in the phytoremediation of arsenic-contaminated soils.

Unintentional formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) is observed and investigated during the thermal desorption in an airflow of a sandy soil, doped artificially with either 1,2-dichlorobenzene (1,2-DiCBz) or hexachlorobenzene (HCBz) using a lab-scale experimental set-up. At all temperatures investigated (200, 250, 300, 350 and 400 °C), this thermal treatment creates significant amounts of PCDD, PCDF and polychlorinated biphenyls (PCB), starting from 1,2-DiCBz. The highest yield of PCDD/F formed from 1,2-DiCBz occurs at 250 °C, with a total (gas + residual soil) output of 117 and 166 pg/g PCDD and PCDF, respectively. Most output reports to the gas phase and the PCDD/F signature is significantly different for residue and gas phase. Also PCB are formed, at a scale of 224 ng/g (300 °C). Compared with 1,2-DiCBz, HCBz converts into PCDD/F even more actively at 350 and 400 °C: the total PCDD/F output created attains 967 pg/g PCDD and 465 pg/g PCDF at 350 °C. As a precursor, 1,2-DiCBz favours formation of PCDF, while PCDD predominates, when the HCBz contaminated soil is treated.

The combination of mechanochemical method and thermal desorption for remediating polychlorinated biphenyls (PCBs) in contaminated soil was tested in this study. The effects of grinding time and heating time on PCB removal efficiency were investigated. The contaminated soil, mixed with CaO powder at a weight ratio of 1:1, was first ground using a planetary ball mill. After 4 h of grinding, the total PCB concentration and its toxic equivalence quantity (TEQ) decreased by 74.6 and 75.8%, respectively. Then, after being heated at 500 °C for 60 min, the residual PCBs in mechanochemical + thermal treated soil decreased to 247 ng/g, resulting in a removal efficiency of 99.95%. The removal effect can be promoted by longer grinding time and heating time; however, increased energy consumption was inevitable. The combination of grinding time and heating time should be optimized in a practical remediation process.

Copper dichloride is an important catalyst both in the dechlorination of chlorinated aromatic compounds and the formation of PCDD/Fs. The effect of copper dichloride on polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) was studied in treated soil and off gas after thermal desorption of PCB-contaminated soil at 300, 400, 500, 600 °C. The presence of copper dichloride clearly enhances thermal desorption by promoting PCBs removal, destruction, and dechlorination. After thermal treatment at 600 °C for 1 h, the removal efficiency and destruction efficiency for PCBs reached 98.1 and 93.9%, respectively. Compared with the positive influence on PCBs, copper dichloride catalyzed large amount of PCDFs formation at 300 °C, with the concentration ratio of 2.35. The effect of CuCl2 on PCDFs formation weakened with the rising temperature since PCDFs destruction became dominant under higher temperature. Different from PCDFs, PCDDs concentration in treated soil and off gas decreased continuously with the increasing temperature.

Mechanisms of Pteris vittata L. to hyperaccumulate arsenic (As), especially the efficient translocation of As from rhizoids to fronds, are not clear yet. The present study aims to investigate the role of transpiration in the accumulation of As from the aspects of transpiration regulation and ecotypic difference. Results showed that As accumulation of P. vittata increased proportionally with an increase in the As exposure concentration. Lowering the transpiration rate by 28∼67% decreased the shoot As concentration by 19∼56%. Comparison of As distribution under normal treatment and shade treatment indicated that transpiration determines the distribution pattern of As in pinnae. In terms of the ecotypic difference, the P. vittata ecotype from moister and warmer habitat had 40% higher transpiration and correspondingly 40% higher shoot As concentration than the ecotype from drier and cooler habitat. Results disclosed that transpiration is the main driver for P. vittata to accumulate and re-distribute As in pinnae.

The homologues levels, distribution characteristics and TEQ of 209 PCBs in soil collected around 3 storage sites of PCB-containing wastes were investigated. The PCBs contents and environmental risk were evaluated to provide a scientific basis for site remediation of PCBs contaminated soil. Totally 12 soil samples were collected from 3 PCB-contaminated sites. The analysis results showed that the PCB-concentration in Soil A was 1 705. 0 µg.g-1 ± 424. 3 µg.g-1 (n =4), higher than Soil B (233. 0 µg.g-1 ± 80. 0, n = 4) and Soil C (225. 7 µg.g-1 ± 90. 2 µg.g-1, n = 4), indicating the soil was heavily polluted by PCBs. Trichlorobiphenyl and Tetrachlorobiphenyl dominated the homologues of PCBs. The mass fraction of chlorine in Soil A, Soil B and Soil C was 43. 7% 1. 0%, 45.5% ± 0. 5% and 44.9% ± 0.3%, respectively, which was similar as Aroclor1242 and l#PCB insulating oil. There was an obvious linear correlation between indicator PCBs and total PCBs (R2 = 0. 998), so indicator PCBs can be used to estimate the level of total PCBs. PCB77, PCB105, PCB118 were predominant in doxin-like PCBs, accounting for 89. 5% ± 4. 0% in total. The TEQ levels of the soil samples (in WHO-TEQ) were 3. 56-63. 55 ng.g-1, which demonstrated a high environmental risk in the area. PCB28/31, PCB33/20, PCB66/80, PCB70, PCB32 and PCB18 were the main PCBs isomers. Compared with other results, the local soil was heavily contaminated by PCBs and the surroundings were under a relatively high risk of environmental contamination.

Synchrotron radiation X-ray absorption near edge structure was employed to study the arsenic (As) speciation in 13 Pteris vittata L. populations collected from 7 provinces, cities, and autonomous regions in China. As in roots of P. vittata was mainly combined with oxygen (O), with a small amount of As combined with glutathione (GSH). Populations from Hunan and Guangxi provinces showed higher percentages of As-GSH in soots. As in roots of P. vittata was predominated with As(V), with the percentage of As(V) to the total As being 59.6±0.6%~83.8±3.8%. The As(V) percentage was in the order of HN5HN3>HN1>TW>CQ>AH>FJ>HN5>HN2>GX2>GX3>HN4>GX1, within the range of 2.4%~12.9%. Different from that in roots, As in shoots was predominated with As(III), with no As(V) detected. The disclosure of As speciation in the roots and shoots of P. vittata contributes to the future research on As accumulation mechanism.

Oxygen plays an important role during the thermal treatment of soil, contaminated with polychlorinated biphenyls (PCBs), due to the potential oxidation of PCBs to form polychlorinated dibenzofurans (PCDFs). The effect of oxygen content (0, 5, 21 and 100%) in carrier gases on PCBs and PCDD/Fs was studied both in soil and gas after thermal desorption of PCBs contaminated soil at 500 °C. All 209 congeners of PCBs and 136 congeners of PCDD/Fs (P = 4 to 8) were analysed. Oxygen content showed little effect on PCB removal and destruction. Under different carrier gases, the removal efficiency and the destruction efficiency for PCBs attained 93.8-95.5 and 83.0-85.0 %, respectively. The levels of PCDD/Fs in soil and gas were correlated positively with oxygen content. Compared with PCDDs, PCDFs in soil were not effectively removed under oxidative conditions because there was chemistry going on and PCBs were being converted to PCDFs. The total concentration of PCDFs in soil and gas was 2.6, 11.3, 15.6 and 17.5 times of the initial PCDFs concentration (21.9 ng/g) in raw soil with increasing oxygen content. Thus, substantial amounts of PCDFs were generated in the presence of oxygen during the treatment of contaminated soil.

Agricultural soil in China contains high levels of di-(2-ethylhexyl) phthalate (DEHP), especially in paddy-field soil of Guangdong province of China, but the accumulation and translocation of DEHP by rice (Oryza sativa L.) remains unknown. In the present study, twenty rice cultivars were cultivated in paddy soil spiked with DEHP, and variations in DEHP accumulation and translocation among various cultivars were investigated. Our results showed that DEHP concentrations in roots and shoots of different rice cultivars at four growth stages (i.e., ripening, tillering, jointing, and flowering stages) varied greatly from 0.26 to 11.8 mg/kg (dry weight, dw) and 0.40 to 7.58 mg/kg (dw), respectively. No obvious change over time was observed. The greatest variation in DEHP concentrations among the rice cultivars occurred at ripening stage, whereas the lowest variation at flowering stage. During ripening stage, the largest variation in DEHP concentrations among cultivars were observed in stems (varying from 0.35 to 13.2 mg/kg), whereas the least one was observed in roots (ranging from 1.01 to 5.72 mg/kg). Significant differences in DEHP concentrations in the roots, stems, leaves and grains of most rice cultivars were found. The translocation factors of DEHP from roots to stems or stems to leaves were higher than those from shoots to grains. Overall, cultivars Tianfengyou 316, Wuyou 308, and Peizataifeng, which contained low levels of DEHP in grains but high levels in shoots, were ideal cultivars for simultaneous production of safe food and phytoremediation of contaminated soil., (Copyright © 2015 Elsevier Inc. All rights reserved.)

This study was launched to establish comprehensive environmental monitoring on the levels and patterns of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polycyclic aromatic hydrocarbons (PAHs) both in soil and ambient air around a thermal desorption plant in China. All 209 congeners of PCBs, 136 congeners of PCDD/Fs (P = 4 to 8) and 16 EPA priority PAHs were analyzed. The concentration of PCBs ranged from 20.0 to 536 ng g(-1) (or 0.077-5.27 pg WHO-TEQ g(-1)) in soil and from 972 to 991 ng Nm(-3) (or 0.245-0.374 pg WHO-TEQ Nm(-3)) in air samples, much higher than the levels in cities. A single soil sampling point could have been affected by some transfer of PCBs from the untreated soil by the fingerprint characteristics and the statistical analysis. Establishing blank values prior to the start-up of new plant is a safe and sure method to establish subsequent impacts on the environment. During the treatment of hazardous waste, strict control of all waste materials and all emissions is required.

In this study, thermal desorption was combined with the addition of nano zerovalent iron (nZVI) to remediate polychlorinated biphenyl (PCB)-contaminated soil collected from a storage point for PCB-contaminated capacitors and transformers. The thermal desorption test conditions were varied from 300 to 600 °C, both with blank soil and with 100 mg of nZVI added. Next, the effect of the amount of nZVI added (0, 20, 40, 100, 200 mg) was investigated by thermal treatment at 400 °C. The test results show that thermal desorption eliminates most of the PCB load and that the presence of nZVI clearly enhances thermal desorption. After thermal treatment at 400 °C, a removal efficiency of 94.2 % was reached, with the use of 200 mg of nZVI. At 600 °C, the PCB removal efficiency after 1 h attained 98.35 % with 100 mg of nZVI and 97.40 % without nZVI. The presence of nZVI effectively decreased both the sum and the WHO-TEQ value of the 12 dl-PCBs.

Background: Phytoextraction is an environmentally acceptable and inexpensive technique for mine tailing rehabilitation that uses metallophyte plants. These plants reduce the soil trace metal contents to environmentally acceptable levels by accumulating trace metals. Recently, whether more trace metals can be removed by species-rich communities of these plants received great attention, as species richness has been reported having positive effects on ecosystem functions. However, how the species richness affects trace metals removal of plant communities of mine tailing is rarely known., Methodology/principal Findings: We examined the effects of species richness on soil trace metal removal in both natural and experimental plant communities. The root lengths and stem heights of each plant species were measured in order to calculate the functional diversity indices. Our results showed that trace metal (Cu, Cd, Pb and Zn) concentrations in mine tailing soil declined as species richness increased in both the natural and experimental plant communities. Species richness, rather than functional diversity, positively affected the mineralomass of the experimental plant communities. The intensity of plant-plant facilitation increased with the species richness of experimental communities. Due to the incremental role of plant-plant facilitation, most of the species had higher biomasses, higher trace metal concentrations in their plant tissues and lower malondialdehyde concentrations in their leaves. Consequently, the positive effects of species richness on mineralomass were mostly attributable to facilitation among plants., Conclusions/significance: Our results provide clear evidence that, due to plant-plant facilitation, species richness positively affects the removal of trace metals from mine tailing soil through phytoextraction and provides further information on diversity conservation and environmental remediation in a mine tailing environment.

Thermal desorption is widely used for remediation of soil contaminated with volatiles, such as solvents and distillates. In this study, a soil contaminated with semivolatile polychlorinated biphenyls (PCBs) was sampled at an interim storage point for waste PCB transformers and heated to temperatures from 300 to 600 °C in a flow of nitrogen to investigate the effect of temperature and particle size on thermal desorption. Two size fractions were tested: coarse soil of 420-841 μm and fine soil with particles <250 μm. A PCB removal efficiency of 98.0 % was attained after 1 h of thermal treatment at 600 °C. The residual amount of PCBs in this soil decreased with rising thermal treatment temperature while the amount transferred to the gas phase increased up to 550 °C; at 600 °C, destruction of PCBs became more obvious. At low temperature, the thermally treated soil still had a similar PCB homologue distribution as raw soil, indicating thermal desorption as a main mechanism in removal. Dechlorination and decomposition increasingly occurred at high temperature, since shifts in average chlorination level were observed, from 3.34 in the raw soil to 2.75 in soil treated at 600 °C. Fine soil particles showed higher removal efficiency and destruction efficiency than coarse particles, suggesting that desorption from coarse particles is influenced by mass transfer.

The frequent co-existence of arsenic (As) and lead (Pb) necessitates the investigation of clean-up technologies for multi-metal(loid)s. Field survey and hydroponic experiments were conducted to elucidate the co-accumulation of As and Pb in Pteris vittata L. The P. vittata population isolated from a Pb-Zn mine in Yunnan province, China is a potential extractor of As and Pb co-contamination. Hydroponic experiment found that the highest frond As and Pb concentrations in mining population of P. vittata reached 12.2 and 0.99 g kg(-1), respectively. The interaction between As and Pb in P. vittata was further more disclosed. Pb (2 mg L(-1)) improved the frond As concentration by 60 to 150% in mining populations of P. vittata. Micro-X-ray absorption spectroscopy indicated that under the combined exposure of As and Pb, the As content in the rhizoid epidermis increased by about 10-fold, and the As(V) percentage increased in each rhizoid tissue, as compared with that under As exposure alone. The co-absorption of As and Pb on the epidermis and the enhanced transportation of As(V) from epidermis into the rhizoid were suggested to contribute to the increased As accumulation.

In order to disclose soil pollution caused by lead (Pb) smeltery and its human health risks, this study investigated Pb concentrations in farmland soil, hair and blood of residents surrounding a Pb smeltery in Henan Province, and discussed the rationality of estimation of the health protection zone from the Pb smeltery. It was found that the Pb concentrations in blood of children living in both M and Y villages exceeded the international Pb poisoning diagnostic criteria. The highest Pb concentration in blood was 491 microg x L(-1), with the percentages of mild, medium and severe Pb poisoning reaching 52.5%, 42.5% and 5.0%, respectively. Pb concentrations in hair of children living in Y village were in excess of the related standard, with the highest being 156 mg x kg(-1), and the average value 2.9 times of that in hair of adults. In terms of Pb in soil, Pb concentrations in 66.7% of the topsoils (0-20 cm) around the smeltery exceeded Grade II (350 mg x kg(-1), pH > 7.5) of the National Soil Environmental Quality Standard (GB 15618-1995), with the highest reaching up to 1687 mg x kg(-1). The severe soil pollution may have played a role in children's health issues in the villages surrounding the smeltery. Therefore, more attention should be paid to the scientific estimation of health protection zone from Pb smeltery and the remediation of heavy-metal contaminated soil in the surrounding areas.

Bulk soil organic carbon concentration and isotopic composition characterize its sources and fate, identify the anthropogenic input of organic carbon into the soil, and trace soil carbon turnover. Coal and/or coal combustion products represent the prime anthropogenic input of organic carbon into three soil profiles located in the vicinity of a steel company. Three profiles positioned away from any direct industrial contribution display vertical pattern in soil organic carbon concentration and isotopic composition that resemble more commonly observed downward gradients in soil carbon chemistry and indicate microbial soil carbon turnover. Two additional profiles located outside of the immediate industrial area display vertical carbon isotope profiles between typical of those from industrial and non-industrial areas. Eight soil profiles and their vertical distribution of bulk organic carbon isotopic composition and concentration collected in the Beijing area reveal and distinguish both anthropogenic and natural contributions of carbon to these soils., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Arsenic (As) contamination poses a high risk to human health. Phytoremediation based on As hyperaccumulator Pteris vittata has been utilized on large areas of contaminated farmland in southern China. However, the reason for the observed differences in As removal among P. vittata populations remains unclear. In this study, spores of four P. vittata populations were collected from four neighboring sites with varying soil As concentration (from 108 mg·kg(-1) to 7527 mg·kg(-1)) and then cultured in a controlled environment to analyze their differing abilities in terms of As accumulation and tolerance. The results indicate that populations from low-As habitats exhibited 80% greater shoot As concentrations compared with those from high-As habitats. On the other hand, populations from high-As habitats exhibited approximately five times greater biomass compared with those from low-As habitats when exposed to the same As stress. Thus, the As accumulation and tolerance of P. vittata were suggested to be two independent processes. Further investigations reveal that the As absorption and As species conversion occurring in roots are two essential activities that bridge the soil As concentration and the responses of P. vittata to As. Depending on the As concentration of the target soil, the selection of different P. vittata populations can result in approximately an eight-fold difference in terms of remediation efficiency., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Arsenic (As) reduction and translocation are key processes for As hyperaccumulation by the hyperaccumulator Pteris vittata L. Micro-X-ray adsorption spectroscopy of P. vittata's rhizoid tissues revealed that As reduction mainly occurred in endodermis during translocation from epidermis to vascular bundle. Prior to reduction, arsenate (As (V)) translocation was an active process requiring energy and employing a phosphate (P) transporter. Use of a synchrotron X-ray microprobe showed that As (V) and P were cotransported and that this process could be enhanced by As (V) exposure or P deficiency but restrained by energy release inhibition caused by 2,4-dinitrophenol or sodium orthovanadate. In contrast, after As reduction, As(III) translocation differed from P translocation and was more efficient, appearing free from the apparent endodermal blockage. The results here revealed the role of the P transporter on As translocation as well as the key role of As reduction in As hyperaccumulation by P. vittata., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

In order to determine the baseline contamination by polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in different areas in China, prior to the construction of municipal solid waste incinerators (MSWIs), a total of 32 representative soil samples was collected near 16 incinerators and analyzed for their PCDD/F concentrations. The PCDD/F baseline concentrations in the soil samples ranged from 0.32 to 11.4 ng I-TEQ kg(-1) (dry matter), with average and median value of 2.73 and 2.24 ng I-TEQ kg(-1) (dry matter), respectively, and a span between maximum and minimum recorded value of 36. The PCDD homologues predominated in 26 out of 32 soil samples, with the ratio (PCDDs)/(PCDFs) ranging from 1.1 to 164; however in the other 6 samples, PCDF homologues were larger, with the same ratio varying from 0.04 to 0.8. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to examine PCDD/F amount and profile in these soil samples, and their possible associations with known emission sources: in this process 6 really distinct isomer fingerprints were identified. Background PCDD/F levels and profiles were comparable to those found in soils from China and other countries and indicate a rather low baseline PCDD/F contamination of soils. The present data provide the tools for future assessment of a possible impact of these MSWIs., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) can be formed during the cooling of flue gases in waste incinerator. These pollutants are either in the gas phase or attached to the fine particles, escaping dust collection. After stack emission, they are slowly oxidized photochemically (gas phase), or eventually are deposited (dry and wet deposition of particulate) in earth surface. In 2007 and 2010, 11 soil samples were collected in the vicinity of a hospital waste incinerator (HWI), prior and after its startup. In order to find out any variation of PCDD/Fs in soil, in brief dioxins, their concentrations were analyzed by high-resolution gas chromatography with high-resolution mass spectrometry (HRGC/HRMS). Compared to the baseline survey (2007), PCDD/Fs in soil significantly increased, by average, +81.6% in total PCDD/Fs and +132.7% in international toxic equivalency (I-TEQ) unit. By principal component analysis (PCA), both the PCDD/Fs homologue and the HxCDF isomer profile in soil were found to become more similar with fly ash. Generally, this incinerator influences the soil only in a limited area. More comprehensive supervision, stricter management and more advanced technology should be implemented in this plant to reduce pollutants emission, even though the level of PCDD/Fs in soil is quite low at present.

This study has taken advantage of the characteristics of concentration of soil organic matter (SOC) and delta13 C(SOC) values to provide proofs for environment quality assessment and to know more about polluted sources, sizes and processes in Beijing steel company area. delta13C values of SOC is good for tracing sources and documenting shifts in community composition and distribution. Two sections (Beijing steel company area and Yongledian, Tongzhou) which belong to two different soil types collected in Beijing, and organic carbon isotopic composition and total soil organic carbon were analyzed. These results shows that SOC of soil samples from Beijing steel company area are quite high, and even 9.7% at the surface sample, however SOC from unpolluted area (Yongledian area) is lower than those of industrial area. delta13 C(SOC) from soils of Beijing steel company area and Yongledian area respectively vary from -24.8 per thousand to -23.1 per thousand and -26.4 per thousand to -20.5 per thousand, the results are quite different. The results reflect that there are different organic carbon sources in different types' soil: Organic carbon from Beijing steel company area has been mainly affected by coal burning, soil organic carbon concentrations are quite high, and pollution can affect on soils 70 cm deep underground; and soils from Yongledian area, have been not polluted, and organic matter is from natural litter (C3 plants). Although there are different soil organic carbon concentrations and isotope compositions, two soil sections have similar variation trends. This study provides proofs for environment quality assessment and know more about polluted and natural sources, sizes in Beijing.

In this study, the contamination of soil by PCDD/Fs and other dioxin-like chemicals in the vicinity of Municipal Solid Waste Incinerators (MSWIs) and Hazardous Waste Incinerators (HWIs) is estimated by the XDS-CALUX bioassay. The resulting CALUX-TEQ value is compared with the WHO-TEQ value obtained from HRGC/HRMS analysis, in order to validate the CALUX bioassay as suitable screening method for PCDD/Fs determination of soil samples. The results show that the CALUX-TEQ and the WHO-TEQ values are significantly correlated (R = 0.87). The WHO-TEQ and CALUX-TEQ of soil samples collected from four waste incineration plants in China were in the range from 1.72 to 31.4 pg-TEQ/g and 1.71 to 44.2 pg-TEQ/g respectively, with a mean value of 6.09 pg-TEQ/g and 11.0 pg-TEQ/g. Considering the homologue patterns, a principal component analysis (PCA) and a hierarchical cluster analysis (HCA) of the PCDD/Fs in the soil samples, the emissions of MSWIs and HWIs were probably not the only source of PCDD/Fs., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Remediation of heavy metals-contaminated soil is still a difficulty and a hotspot of international research projects. At present, the technologies commonly adopted for the remediation of contaminated sites mainly include excavation, solidification/stabilization (S/S), soil washing, soil vapor extraction (SVE), thermal treatment, and bioremediation. Based on the S/S technical guidelines of Unite State Environmental Protection Agency (EPA) and United Kingdom Environment Agency (EA) and the domestic and foreign patents, this paper introduced the concepts of S/S and its development status at home and abroad, and discussed its future development directions. Solidification refers to a process that binds contaminated media with a reagent, changing the media's physical properties via increasing its compressive strength, decreasing its permeability, and encapsulating the contaminants to form a solid material. Stabilization refers to the process that involves a chemical reaction which reduces the leachability of a waste, chemically immobilizes the waste and reduces its solubility, making the waste become less harmful or less mobile. S/S technology includes cement solidification, lime pozzolanic solidification, plastic materials stabilization, vitrification, and regent-based stabilization. Stabilization (or immobilization) treatment processes convert contaminants to less mobile forms through chemical or thermal interactions. In stabilization technology, the aim of adding agents is to change the soil physical and chemical properties through pH control technology, redox potential technology, precipitation techniques, adsorption technology, and ion-exchange technology that change the existing forms of heavy metals in soil, and thus, reduce the heavy metals bioavailability and mobility. This review also discussed the S/S evaluation methods, highlighted the need to enhance S/S technology in the molecular bonding, soil polymers, and formulation of China's S/S technical guidelines.

Mapping the spatial distribution of contaminants in soils is the basis of pollution evaluation and risk control. Interpolation methods are extensively applied in the mapping processes to estimate the heavy metal concentrations at unsampled sites. The performances of interpolation methods (inverse distance weighting, local polynomial, ordinary kriging and radial basis functions) were assessed and compared using the root mean square error for cross validation. The results indicated that all interpolation methods provided a high prediction accuracy of the mean concentration of soil heavy metals. However, the classic method based on percentages of polluted samples, gave a pollution area 23.54-41.92% larger than that estimated by interpolation methods. The difference in contaminated area estimation among the four methods reached 6.14%. According to the interpolation results, the spatial uncertainty of polluted areas was mainly located in three types of region: (a) the local maxima concentration region surrounded by low concentration (clean) sites, (b) the local minima concentration region surrounded with highly polluted samples; and (c) the boundaries of the contaminated areas., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Remediation of pesticide-polluted soil is particularly challenging when pesticides in soil are aged and a mixture of pesticides is present. Application of zerovalent iron (Fe(0)) was investigated to accelerate the degradation of HCHs (alpha-, beta-, gamma- and delta-hexachlorocyclohexane) and DDX (DDT, DDE and DDD) in the soil from a former organochlorine pesticide manufacturing plant. Ultrasonic extraction was used extract the organochlorine pesticides from soil. The identification and quantification of organochlorine pesticides in the extracts were accomplished by gas chromatograph. The addition of Fe(0) facilitated the degradation of the beta-HCH isomer, but had little effect on the degradation of alpha-HCH, gamma-HCH and delta-HCH. Zerovalent iron significantly increased the degradation of p,p'-DDT and o,p'-DDT in soil, and the percentage degradation of p,p'-DDT and o,p'-DDT increased with increased Fe(0) concentration during the first period of incubation. However, the amount of p,p'-DDD, the main dechlorinated product of p,p'-DDT, basically kept increased except in the unamended soil. The addition of Fe(0) therefore did not increased the percent degradation of summation SigmaDDT (p,p'-DDT+p,p'-DDD+p,p'-DDE) markedly., (2010 Elsevier Ltd. All rights reserved.)

The temporal variations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in 33 agricultural soil samples in the vicinity of a municipal solid waste incinerator (MSWI) in Eastern China were determined one year after the initial investigation in 2006. The soil PCDD/F concentrations in 2007 ranged from 73.6 to 377 ng kg(-1) (0.60-6.38 ng I-TEQ kg(-1)). During 2006-2007, the overall soil PCDD/F levels increased significantly, i.e., 33% and 39% for total concentration and I-TEQ (median value), respectively. Moreover, soils in the study area are proved to be almost free from previously suspected PCDD/F sources, i.e., pentachlorophenol/sodium penta-chlorophenate (PCP/PCP-Na) and 1,3,5-trichloro-2-(4-nitrophenoxy) benzene (CNP) contaminations. Furthermore, the results from a congener-specific factor analysis between soils (collected in two investigations) and dioxin emission sources suggest that diffuse sources including open burning of wastes, traffic and hot water boilers are major contributors that are responsible for the accumulation of PCDD/Fs in soils. By contrast, the impact of the presumably major PCDD/F source identified in our previous study, i.e., the MSWI, seems to be limited.

To investigate influences of mining activities on heavy metal contamination and health risk in vegetable of mining-affected area, the present study was undertaken as a preliminary survey of As, Cd, Co, Cr, Cu, Ni, Pb and Zn concentrations of majority vegetables and soils in area affected by an ancient tin ore, Yunnan province. Based on the soil heavy metals investigated, average Nemero index of soil heavy metals reach 50.1, showed that vegetable fields were contaminated by heavy metals, especially As: average As concentration of soils could reach 1225 mg x kg(-1). Heavy metal concentrations in the edible portions of majority vegetables exceeded the national standards of China seriously, especially As and Pb, and the maximum of As and Pb concentrations (DW) could reach 856 mg x kg(-1) and 506 mg x kg(-1), respectively. Heavy metal concentrations among 3 kinds of vegetables decreased in following order: leaf vegetables > fruit vegetables > rhizome vegetables. Consumption of vegetables from the mining-affected area may pose extremely high health risk of As and Pb to local residents, which the exposed risk indexes could reach 158 and 13.3, respectively.

Fertilization has become one of the essential measures for enhancing efficiency of phytoremediating contaminated soils with heavy metal. In order to screen optimal P fertilizer for As-phytoremediation, a greenhouse study was conducted on the growth, As-accumulation and uptake of N, P and K by Pteris vittata L. in As-contaminated soils with different forms of P fertilizers. The results indicated that the biomass of plant with As addition decreased compared to no As-addition treatments except fused calcium magnesium phosphate (CaMg-P) treatment. The plants in As addition soils with CaMg-P, calcium dihydrogen phosphate (CDP) and di-ammonium phosphate (DAP) had higher biomass than those with other P fertilizer and control (0.83 g/pot). The As accumulations of plant aboveground in As addition soils are in order of CDP > CaMg-P> DAP> Potassium Phosphate Monobasic > Monosodium phosphate > control > Calcium superphosphate. The efficiency of As removal from As addition soils with CDP was the highest, 7.28%. Thus it can be seen the ability of phytoremediation using P. vittata could be improved by P fertilization, which CDP should be recommended preferentially and CaMg-P and DAP is considered as replaceable fertilizer for sake of pH, N, P and available As in phytoremediated soils.

Isomer-specific data were investigated in order to identify the sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in agricultural soils, including Fluvo-aquic and paddy soils, in the vicinity of a Chinese municipal solid waste incineration (MSWI) plant. Homologue and isomer profiles of PCDD/Fs in soils were compared with those of potential sources, including combustion sources, i.e., MSWI flue gas and fly ash; and the impurities in agrochemicals, such as the pentachlorophenol (PCP), sodium pentachlorophenate (PCP-Na) and 1,3,5-trichloro-2-(4-nitrophenoxy) benzene (CNP). The results showed that the PCDD/F isomer profiles of combustion sources and agricultural soils were very similar, especially for PCDFs, although their homologue profiles varied, indicating that all the isomers within each homologue behave identically in the air and soil. Moreover, factor analysis of the isomer compositions among 33 soil samples revealed that the contamination of PCDD/Fs in agricultural soils near the MSWI plant were primarily influenced by the combustion sources, followed by the PCP/PCP-Na and CNP sources. This implication is consistent with our previous findings based on chemometric analysis of homologue profiles of soil and flue gas samples, and identifies PCP/PCP-Na as an additional important source of PCDD/Fs in the local area. This makes the similarities and differences of isomer profiles between Fluvo-aquic and paddy soils more explainable. It is, therefore, advisable to use isomer-specific data for PCDD/F source identifications where possible.

Certain plant species have been shown to vigorously accumulate some metals from soil, and thus represent promising and effective remediation alternatives. In order to select the optimum forms of nitrogen (N) fertilizers for the arsenic (As) hyperaccumulator, Pteris vittata L., to maximize As extraction, five forms of N were added individually to different treatments to study the effect of N forms on As uptake of the plants under soil culture in a greenhouse. Although shoot As concentration tended to decrease and As translocation from root to shoot was inhibited, overall As accumulation was greater due to higher biomass when N fertilizer was added. Arsenic accumulation in plants with N fertilization was 100-300% more than in the plants without N fertilization. There were obvious differences in plant biomass and As accumulation among the N forms, i.e., NH4HCO3, (NH4)2S04, Ca(NO3)2, KNO3, urea. The total As accumulation in the plants grown in As-supplied soil, under different forms of N fertilizer, decreased as NH4HCO3>(NH4)2S04 > urea > Ca(NO3)2 >KNO3>CK. The plants treated with N and As accumulated up to 5.3-7.97 mg As/pot and removed 3.7-5.5% As from the soils, compared to approximately 2.3% of As removal in the control. NH4+ -N was apparently more effective than other N fertilizers in stimulating As removal when soil was supplied with As at initiation. No significant differences in available As were found among different forms of N fertilizer after phytoremediation. It is concluded that NH4+ -N was the preferable fertilizer for P. vittata to maximize As removal.

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in As-hyperaccumulator, uptake and transport of arsenate (As(V)) and arsenite (As(III)) were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As(III) more than As(V), while the reverse was observed at high concentrations of phosphate (> or = 1.0 mmol/L). Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As(V). It may in part be due to competition between phosphorus and As(V) during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As(III). Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposed to As(V); but the suppression of phosphate to As transport may be insignificant when P. vittata exposed to As(III) under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P.

In an area near an arsenic mine in Hunan Province of south China, soils were often found with elevated arsenic levels. A field survey was conducted to determine arsenic accumulation in 8 Cretan brake ferns (Pteris cretica) and 16 Chinese brake ferns (Pteris vittata) growing on these soils. Three factors were evaluated: arsenic concentration in above ground parts (fronds), arsenic bioaccumulation factor (BF; ratio of arsenic in fronds to soil) and arsenic translocation factor (TF; ratio of arsenic in fronds to roots). Arsenic concentrations in the fronds of Chinese brake fern were 3-704 mg kg-1, the BFs were 0.06-7.43 and the TFs were 0.17-3.98, while those in Cretan brake fern were 149-694 mg kg-1, 1.34-6.62 and 1.00-2.61, respectively. Our survey showed that both ferns were capable of arsenic accumulation under field conditions. With most of the arsenic being accumulated in the fronds, these ferns have potential for use in phytoremediation of arsenic contaminated soils.

A field investigation and pot experiments were conducted to determine the potential of arsenic (As) hyperaccumulator, Pteris vittata L., to remediate sites co-contaminated with zinc (Zn) and As. We found that P. vittata L. had a very high tolerance to Zn and grew normally at sites with high Zn concentrations. In addition, P. vittata L. could effectively take up Zn into its fronds, with a maximum of 737 mg kg(-1) under field conditions. In pot experiments, the accumulated Zn concentration increased significantly as the Zn treatment was raised from 0 to 2000 mg kg(-1), with a maximum Zn accumulation of 0.22 mg pot(-1). Although the concentration of As in P. vittata L. was reduced by the addition of Zn, total frond accumulation of As was elevated when the Zn treatment was increased from 0 to 1000 mg kg(-1), with a maximum As accumulation of 8.3 mg pot(-1) in the presence of 1000 mg kg(-1) Zn. The high Zn tolerance, relatively high ability to accumulate Zn, and great capacity to accumulate As under conditions of suppression by high Zn suggest that P. vittata L. could be useful for the remediation of sites co-contaminated with Zn and As.

As soil arsenic concentration might have great effect on arsenic accumulation of hyperaccumulator Pteris vittata L. , three sample areas with different As pollution level in the soils are investigated in Chenzhou, Hunan Province, where Pteris vittata L. grows broadly. Great variation of As concentrations is found to be not only among different samples in the same sampling areas but also between rhizosphere and bulk soil of P. vittata L. So it is suggested that rhizosphere soil should be sampled to study the effect of soil contamination on plant accumulation. The As concentration in frond of P. vittata L. increased dramatically at lower As level but decreased slowly when As concentration higher than 1 000 mg/kg. Arsenic translocation factors of P. vittata L. were greater than 1 in all samples in this study, whereas As concentration in shoots in lower As contaminated soil and bioaccumulation factors in higher As contaminated soil are fail to meet the definition of As hyperaccumulator.

In order to assess soil As contamination and potential risk for human, soil, paddy rice, vegetable and human hair samples from the areas near the industrial districts in Chenzhou, southern China were sampled and analyzed. The results showed that the anthropogenic industrial activities have caused in local agricultural soils to be contaminated with As in a range of 11.0-1217 mg/kg. The GIS-based map shows that soil contamination with As occurred on a large scale, which probably accounted for up to 30% of the total area investigated. Soil As concentration abruptly decreased with an increase in the distance from the polluting source. High As concentrations were found in the rice grain that ranged from 0.5 to 7.5 mg/kg, most of which exceed the maximal permissible limit of 1.0 mg/kg dry matter. Arsenic accumulated in significantly different levels between leafy vegetables and non-leafy vegetables. Non-leafy vegetables should be recommended in As-contaminated soils, as their edible parts were found in relatively low As level. Arsenic concentrations in 95% of the total human hair samples in the contaminated districts were above the critical value, 1.0 mg/kg, set by the World Health Organization. Arsenic could be enriched in human hair to very high levels without being affected by As containing water. The results revealed that the soils and plants grown on them are major contributors to elevate hair As in the industrial population. Therefore, the potential impact on human health of ingestion/inhalation of soil As around the industrial districts seems to be rather serious. Hence proper treatments for As contaminated soils are urgently needed to reduce the contamination.

Assessing the concentration of potentially harmful heavy metals in the soil of urban parks is imperative in order to evaluate the potential risks to residents and tourists. To date, little research on soil pollution in China's urban parks has been conducted. To identify the concentrations and sources of heavy metals, and to assess the soil environmental quality, samples were collected from 30 urban parks located in the city of Beijing. Subsequently, the concentrations of Cu, Ni, Pb and Zn in the samples were analyzed. The investigation revealed that the accumulations of Cu and Pb were readily apparent in the soils. The integrated pollution index (IPI) of these four metals ranged from 0.97 to 9.21, with the highest IPI in the densely populated historic center district (HCD). Using multivariate statistic approaches (principal components analysis and hierarchical cluster analysis), two factors controlling the heavy metal variability were obtained, which accounted for nearly 80% of the total variance. Nickel and Zn levels were controlled by parent material in the soils, whereas Cu, Pb and, in part, Zn were accounted for mainly by anthropogenic activities. The findings presented here indicate that the location and the age of the park are important factors in determining the extent of heavy metal, particularly Cu and Pb, pollution. In addition, the accumulation of Zn did not appear to reach pollution levels, and no obvious pollution by Ni was observed in the soils of the parks in Beijing.