Effects of citric acid and the siderophore desferrioxamine B (DFO-B) on the mobility of germanium and rare earth elements in soil and uptake in Phalaris arundinacea

Effects of citric acid and desferrioxamine B (DFO-B) on the availability of Ge and selected rare earth elements (REEs) (La, Nd, Gd, Er) to Phalaris arundinacea were investigated. A soil dissolution experiment was conducted to elucidate the effect of citric acid and DFO-B at different concentrations (1 and 10 mmol L^?1 citric acid) on the release of Ge and REEs from soil. In a greenhouse, plants of P. arundinacea were cultivated on soil and on sand cultures to investigate the effects of citric acid and DFO-B on the uptake of Ge and REEs by the plants. Addition of 10 mmol L^?1 citric acid significantly enhanced desorption of Ge and REEs from soil and uptake into soil-grown plants. Applying DFO-B enhanced the dissolution and the uptake of REEs, while no effect on Ge was observed. In sand cultures, the presence of citric acid and DFO-B significantly decreased the uptake of Ge and REEs, indicating a discrimination of the formed complexes during uptake. This study clearly indicates that citric acid and the microbial siderophore DFO-B may enhance phytoextraction of Ge and REEs due to the formation of soluble complexes that increase the migration of elements in the rhizosphere.     

Assessment the Exposure Level of Rare Earth Elements in Workers Producing Cerium,Lanthanum Oxide Ultrafine and Nanoparticles

In order to assess occupational exposure level of 15 rare earth elements (REEs) and identify the associated influence, we used inductively coupled plasma mass spectrometry (ICP-MS) based on closed-vessel microwave-assisted wet digestion procedure to determinate the concentration of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in urinary samples obtained from workers producing ultrafine and nanoparticles containing cerium and lanthanum oxide. The results suggest that La and Ce were the primary component, together accounting for 97 % of total REEs in workers. The urinary levels of La, and Ce among the workers (6.36, 15.32 μg.g^?1 creatinine, respectively) were significantly enriched compared to those levels measured in the control subjects (1.52, 4.04 μg.g^?1 creatinine, respectively) (p < 0.05). This study simultaneously identified the associated individual factors, the results indicate that the concentrations in over 5 years group (11.64 ± 10.93 for La, 27.83 ± 24.38 for Ce) were significantly elevated compared to 1–5 years group (2.58 ± 1.51 for La, 6.87 ± 3.90 for Ce) (p < 0.05). Compared the urinary levels of La and Ce at the separation and packaging locations (9.10 ± 9.51 for La, 22.29 ± 21.01 for Ce) with the other locations (2.85 ± 0.98 for La, 6.37 ± 2.12 for Ce), the results show urinary concentrations were significantly higher in workers at separation and packaging locations (p < 0.01). Inter-individual variation in levels of La and Ce in urine is the result of multi-factorial comprehensive action. Further researches should focus on the multiple factors contributing to the REEs levels of the occupationally exposed workers.     

Rare earth elements and relation between their potential bioavailability and soil properties, Nidda catchment (Central Germany)

Rare earth elements (REEs) are widely used in industry and the entry of REEs into the pedosphere is assumed. Data about REEs in soils are scarce since only a few studies discuss their ecologically relevant behavior. Hence, we investigated total contents (aqua regia digestion) and potentially bioavailable contents (EDTA extraction) of REEs in soils from the Nidda catchment in Hesse (Central Germany). The study site covers a 1,600 km² sized area and 232 soil samples from 63 soil profiles were examined. The total REE content varied considerably, ranging from 544 mg kg^?1 to 41 mg kg^?1 (mean 201.1 mg kg^?1) with a high proportion of light REEs. Highest REE contents were found in the soilscape VB, followed by LVB, WNE, T, WSW and BF with the smallest concentrations. With respect to the parent material the contents decreased in the following order: basalt > clay slate > loess > sandstone. On average 15.9% of the total REEs belong to the potentially bioavailable fraction. They range greatly by a factor of 100, between 1.3 and 171.3 mg kg^?1 (average 33.5 mg kg^?1). Remarkably, Yttrium has a maximum available proportion of 75%. In contrast, Ce showed the highest total contents with the smallest potentially bioavailable proportion of all elements. Regression analyses established relation between soil properties and the potential bioavailability of REEs. Around 53% (range from 29.9 to 76.8%) of the REE’s potential bioavailability variations could be explained by the chosen variables (pH, clay and C_org contents and the total element concentrations). Occurrence patterns and concentrations of REEs lie within the range of the results found in the available literature. Bioavailability is linked to soil properties and varies greatly according to the individual element. In comparison with the chosen soil properties the pH value shows the least impact on bioavailability.     

Elemental composition of ambient air particles in Taiyuan,China: evaluation of lifetime cancer and non-cancer risks

Abstract

Shanxi is a heavily polluted area in China. Our aim was to analyze the elemental concentration (71 elements) in ambient air in Taiyuan and evaluate cancer and non-cancer risks. Air was sampled in four urban sites and one rural site in the heating season (winter/spring) and summer season (totally 118?days sampling time). Mean total suspended particles (TSP) across all sampling sites were 248 µg/m³ in summer and 478 µg/m³ in winter. The heating season had higher levels of S, Pb, Br, Mn, Se, As, Ni, Cd, and Hg (23.3 µg/m³, 821?ng/m³, 725?ng/m³, 460?ng/m³, 79?ng/m³, 65?ng/m³, 34?ng/m³, 17?ng/m³, and 3.5?ng/m³, respectively) than the summer season (9.6 µg/m³, 276?ng/m³, 138?ng/m³, 283?ng/m³, 0?ng/m³, 21?ng/m³, 21?ng/m³, 6.8?ng/m³, and 0?ng/m³, respectively), except for Cr and Co, of which the levels were higher in summer. Many elements had a high correlation with the TSP level (r?=?0.70–0.96) and S (r?=?0.61–0.95). A health risk assessment demonstrated that Mn and Cr could have a risk of non-cancer effects. Estimated lifetime cancer risks (R_i>10^?6) were observed for As, Cd, Co, Cr, and Ni, indicating that cancer risks from air pollution were relatively high in Taiyuan.     

Probabilistic risk assessment of inhalation of nickel-rich soil particulates on Jeju Island,Korea

The soils of Jeju Island contain naturally abundant nickel originating from prehistoric volcanic activity. Nickel is a known human carcinogen via inhalation exposure. A risk assessment of soil particle inhalation was conducted for the first time in Korea through the analysis of soil and air data obtained from agricultural sites. Sixteen sites in Jeju were selected—13 farms, 2 citrus orchards, and 1 ranch. Forty-four soil samples were taken from these sites and analyzed for nickel content. Total suspended solids (TSP) and particulate matter up to 10 µm in size (PM10) were measured directly from the agricultural sites, and nickel concentrations in TSP and PM10 were quantified for use in the inhalation risk assessment. We conducted a probabilistic inhalation risk analysis using monitoring data obtained from the 16 sites on Jeju Island. Risk assessment procedures followed both the Korean Ministry of Environment and the U.S. Environmental Protection Agency (USEPA) risk assessment methodologies. The cancer risk associated with inhalation followed by application of the Korean risk assessment approach ranged from 4.98 × 10^?9 to 3.43 × 10^?7, whereas the cancer risk associated with inhalation followed by application of the USEPA risk assessment approach ranged from 3.40 × 10^?9 to 3.74 × 10^?7. This study demonstrates that no carcinogenic risk is associated with inhalation in Jeju, based on a lower cancer risk limit of 10^?6.     

Fractionations of rare earth elements in plants and their conceptive model

Fractionations of rare earth elements (REEs) and their mechanisms in soybean were studied through application of exogenous mixed REEs under hydroponic conditions. Significant enrichment of middle REEs (MREEs) and heavy REEs (HREEs) was observed in plant roots and leaves respectively, with slight fractionation between light REEs (LREEs) and HREEs in stems. Moreover, the tetrad effect was observed in these organs. Investigations into REE speciation in roots and in the xylem sap using X-ray absorption spectroscopy (XAS) and nanometer-sized TiO₂ adsorption techniques, associated with other controlled experiments, demonstrated that REE fractionations should be dominated by fixation mechanism in roots caused by cell wall absorption and phosphate precipitation, and by the combined effects of fixation mechanism and transport mechanism in aboveground parts caused by solution complexation by intrinsic organic ligands. A conceptive model was established for REE fractionations in plants based on the above studies.     

Onsite chelate resin solid-phase extraction of rare earth elements in natural water samples: its implication for studying past redox changes by inorganic geochemistry

Rare earth element (REE) patterns in natural water and geological samples provide information on previous changes in environmental conditions, such as redox changes and material cycles; however, quantitative analysis of REEs in these samples is complicated by the relatively low contents of REEs in such samples as well as mass interference from ¹³⁵Ba¹⁶O and ¹³⁷Ba¹⁶O in inductively coupled plasma mass spectrometry (ICP-MS) analyses. In this study, onsite solid-phase extraction and preconcentration methods for REEs using an iminobisacetic acid–ethylenediaminetriacetic acid chelate resin (Nobias Chelate PA1, Hitachi High-Tech Fielding) were adopted for the analyses. Standard reference materials (SPS-SW1 artificial surface water) and natural ground water and spring water samples were used to evaluate the methods. Using the chelate resin, background levels of REEs were found to be less than 0.3 ng L^?1 and recovery rates (REEs, 1 ng L^?1) were 97.9–106.7% for the artificial surface water. Ba contents were lower than the detection limit after extraction. Additionally, duplicate analyses were performed to check the reproducibility of the onsite extraction. The REE patterns in the natural water samples were in good agreement with those obtained using a previous method (the interference calibration method without solid-phase extraction). Therefore, onsite solid-phase extraction using the chelate resin was demonstrated to be a rapid and simple preparation technique for REE analyses.     

Risk of adult street vendor exposure to traffic-related air pollution in Bangkok,Thailand

Traffic-related air pollution (TRAP), including particulate matter (PM) in respirable coarse and fine size fractions (PM10 and PM2.5), is known to have exposure effects on human health and environment. Real-time PM10 and PM2.5 concentrations were collected from the study locations in Bangkok, Thailand, using TSI AM510 particle counters. Temperature and % relative humidity (%RH) were also collected. Data were compared to data from the closest station of the Pollution Control Department (PCD), Thailand. Real-time mean concentration varied from 86 to 1107 µg/m³ (PM10) and varied from 25 to 664 µg/m³ (PM2.5). In addition, real-time mean PM10 (223.1 µg/m³) was nearly four times greater than that measured by the PCD station, 60 µg/m³. Temperature and %RH from real-time air monitoring and PCD station were comparable. In each study location (five locations, two in morning and afternoon/evening), there were significant positive correlations between PM10 and PM2.5 concentrations and significant negative correlations between temperature and RH%. Results suggested that outdoor TRAP via measured real-time PM concentrations were more realistic exposure concentration estimates among street vendors as related to respiratory and other symptoms than data obtained from PCD station. Nevertheless, PM10 as measured by the PCD station might be a reasonable surrogate for estimated outdoor PM2.5 exposure.     

Fractionations of rare earth elements in plants and their conceptive model

Fractionations of rare earth elements (REEs) and their mechanisms in soybean were studied through application of exogenous mixed REEs under hydroponic conditions. Significant enrichment of middle REEs (MREEs) and heavy REEs (HREEs) was observed in plant roots and leaves respectively, with slight fractionation between light REEs (LREEs) and HREEs in stems. Moreover, the tetrad effect was observed in these organs. Investigations into REE speciation in roots and in the xylem sap using X-ray absorption spectroscopy (XAS) and nanometer-sized TiO2 adsorption techniques, associated with other controlled experiments, demonstrated that REE fractionations should be dominated by fixation mechanism in roots caused by cell wall absorption and phosphate precipitation, and by the combined effects of fixation mechanism and transport mechanism in aboveground parts caused by solution complexation by intrinsic organic ligands. A conceptive model was established for REE fractionations in plants based on the above studies.     

Influence of Rare Earth Elements on Metabolism and Related Enzyme Activity and Isozyme Expression in Tetrastigma hemsleyanum Cell Suspension Cultures

The effects of rare earth elements (REEs) not only on cell growth and flavonoid accumulation of Tetrastigma hemsleyanum suspension cells but also on the isoenzyme patterns and activities of related enzymes were studied in this paper. There were no significant differences in enhancement of flavonoid accumulation in T. hemsleyanum suspension cells among La³⁺, Ce³⁺, and Nd³⁺. Whereas their inductive effects on cell proliferation varied greatly. The most significant effects were achieved with 100 μM Ce³⁺and Nd³⁺. Under treatment over a 25-day culture period, the maximal biomass levels reached 1.92- and 1.74-fold and the total flavonoid contents are 1.45- and 1.49-fold, than that of control, respectively. Catalase, phenylalanine ammonia-lyase (PAL), and peroxidase (POD) activity was activated significantly when the REE concentration range from 0 to 300 μM, whereas no significant changes were found in superoxide dismutase activity. Differences of esterase isozymes under REE treatment only laid in expression level, and there were no specific bands. The expression level of some POD isozymes strengthened with increasing concentration of REEs within the range of 50–200 μM. When REE concentration was higher than 300 μM, the expression of some POD isozymes was inhibited; meanwhile, some other new POD isozymes were induced. Our results also showed REEs did not directly influence PAL activity. So, we speculated that 50–200 μM REEs could activate some of antioxidant enzymes, adjust some isozymes expression, trigger the defense responses of T. hemsleyanum suspension cells, and stimulate flavonoid accumulation by inducing PAL activity.     

Single-Phase and Two-Phase Anaerobic Co-Digestion of Residues from the Treatment Process of Waste Vegetable Oil and Pig Manure

The co-digestion of residues from the pre-treatment process of waste vegetable oil (OW) and pig manure (PM) was performed under different OW/PM feed ratios (1:0, 1:1 and 1:3 v/v) and at organic loading rates ranging from 0.25 to 3.1 kg VS m^?3 day^?1 in lab-scale single-phase (SP) and two-phase (TP) systems. From the experiments, it was observed that digestion of OW alone was inhibitory for the anaerobic degradation. Mixing OW with PM neutralized the negative effects of lipids accumulation and high VS removal efficiencies were realized in both systems (63 and 71 % in SP system and 69 and 72 % in TP system, at 1:1 and 1:3 OW/PM mixtures, respectively). Under the same operational conditions, the methane yield was 0.30 and 0.22 m³ CH₄ kg^?1 VS removed for the SP anaerobic digester and 0.30 and 0.27 m³ CH₄ kg^?1 VS removed for the TP configuration. Additionally, TP digestion presented more stable operation and higher treatment capacity.     

Body temperature and respiratory dynamics in un-shaded beef cattle

In this study body temperature (BT, °C) and panting score (PS, 0–4.5; where 0?=?no panting/no stress and 4.5?=?catastrophic stress) data were obtained from 30 Angus steers housed outside over 120 days Steers were implanted with a BT transmitter on day ?31, BT was recorded at 30-min intervals to a data logger and downloaded each day to a database. The cattle were housed in ten outdoor un-shaded pens with an earthen floor, eight of which had a pen floor area of 144 m² (three transmitter steers plus five non-transmitter steers; 18 m²/steer) and two had an area of 168 m² (three transmitter steers and six non-transmitter steers; 18.7 m²/steer). Only data from the transmitter steers were used in this study. The PS of the steers was obtained daily (± 15 min) at 0600 hours (AM), 1200 hours (MD) and 1600 hours (PM). At the same times climate variables (ambient temperature, black globe temperature, solar radiation, relative humidity, wind speed and rainfall) were obtained from an on-site weather station. PS observations were made from outside the pens so as not to influence cattle responses. The two closest BT values to the time when PS was obtained were downloaded retrospectively from a logger and averaged. A total of 8,352 observations were used to generate second order polynomial response curves: (AM) y?=?39.08?+?0.009?x +?0.137x ² (R ²?=?0.94; P? y?=?39.09?+?0.914x ? 0.080x ² (R ²?=?0.89; P? y?=?39.52?+?0.790x ? 0.068x ² (R ²?=?0.83; P?x?PS. These data suggest that PS is a good indicator of body temperature. The BT at MD corresponded to slightly lower PS compared with PM, e.g., for PS 1; BT at MD?=?39.1?±?0.05 °C whereas BT at PM?=?39.5?±?0.05 °C. However during AM, BT was lower (P?相似文献   

Time-of-day effects of exposure to solar radiation on thermoregulation during outdoor exercise in the heat

High solar radiation has been recognised as a contributing factor to exertional heat-related illness in individuals exercising outdoors in the heat. Although solar radiation intensity has been known to have similar time-of-day variation as body temperature, the relationship between fluctuations in solar radiation associated with diurnal change in the angle of sunlight and thermoregulatory responses in individuals exercising outdoors in a hot environment remains largely unknown. The present study therefore investigated the time-of-day effects of variations in solar radiation associated with changing solar elevation angle on thermoregulatory responses during moderate-intensity outdoor exercise in the heat of summer. Eight healthy, high school baseball players, heat-acclimatised male volunteers completed a 3-h outdoor baseball trainings under the clear sky in the heat. The trainings were commenced at 0900 h in AM trial and at 1600 h in PM trial each on a separate day. Solar radiation and solar elevation angle during exercise continued to increase in AM (672–1107 W/m² and 44–69°) and decrease in PM (717–0 W/m² and 34–0°) and were higher on AM than on PM (both P < 0.001). Although ambient temperature (AM 32–36°C, PM 36–30°C) and wet-bulb globe temperature (AM 31–33°C, PM 34–27°C) also continued to increase in AM and decrease in PM, there were no differences between trials in these (both P > 0.05). Tympanic temperature measured by an infrared tympanic thermometer and mean skin temperature were higher in AM than PM at 120 and 180 min (P < 0.05). Skin temperature was higher in AM than PM at the upper arm and thigh at 120 min (P < 0.05) and at the calf at 120 and 180 min (both P < 0.05). Body heat gain from the sun was greater during exercise in AM than PM (P < 0.0001), at 0–60 min in PM than AM (P < 0.0001) and at 120–180 min in AM than PM (P < 0.0001). Dry heat loss during exercise was greater at 0–60 min (P < 0.0001), and lower at 60–120 min (P < 0.05) and 120–180 min (P < 0.0001) in AM than PM. Evaporative heat loss during exercise was greater in PM than AM at 120–180 min (P < 0.0001). Total (dry + evaporation) heat loss at the skin was greater during exercise in PM than AM (P < 0.0001), at 0–60 min in AM than PM (P < 0.0001) and at 60–120 and 120–180 min in PM than AM (P < 0.05 and 0.0001). Heart rate at 120–150 min was also higher in AM than PM (P < 0.05). Neither perceived thermal sensation nor rating of perceived exertion was different between trials (both P > 0.05). The current study demonstrates a greater thermoregulatory strain in the morning than in the afternoon resulting from a higher body temperature and heart rate in relation to an increase in environmental heat stress with rising solar radiation and solar elevation angle during moderate-intensity outdoor exercise in the heat. This response is associated with a lesser net heat loss at the skin and a greater body heat gain from the sun in the morning compared with the afternoon.     

Bioaccessibility and health risk assessment of rare earth elements in Porphyra seaweed species

In this study, the content and bioaccessibility of rare earth elements (REEs) in Porphyra spp. Samples before and after thermal treatments were investigated. Additionally, the risks of REEs exposure to human health were assessed. REEs content significantly reduced after thermal processing (P < 0.01), and the removal rate of REEs was approximately 30%. Thermal treatment increased REEs bioaccessibility from 44% to 64.34%. The concentration and bioaccessibility of Ce, La, Y, Nd were high in raw and thermally treated Porphyra samples, and there was no correlation between REEs content and bioaccessibility. Based on the following parameters: highest content of REEs in the studied seaweed samples (13.45 mg/kg), the highest daily seafood consumption (44.9 g/day), and the highest bioaccessibility (64.34%), the ratio of the calculated daily intake (DI) to daily allowable intake by diet (DAI_diet) of REEs did not exceed the reference value in rare earth mining areas or under extreme conditions. The DI via seafood consumption would be exceeded when the content of REEs in the seafood sample is greater than 15.77 mg/kg. In this study, the concentration of REEs did not exceed 15.77 mg/kg in any sample. Thus, the human health risks of REEs associated with seafood are low.     

Particulate matter and bacteria characteristics of the Middle East Dust (MED) storms over Ahvaz,Iran

The Middle East Dust storms have greatly affected the south and west parts of Iran during the last decade. The main purpose of this study was to examine and compare culturable airborne bacteria concentration in particulate matter (PM) during normal, semi-dust, and dust event days in different places and seasons in Ahvaz from November 2011 to May 2012. Sampling was performed every 6 days and on dust event days at different sampling stations. The overall mean concentrations of PM₁₀, PM_2.5, and PM₁ for the entire study period were 598.92, 114.8, and 34.5 μg/m³, respectively. The PM concentrations during the dust event days were much higher than normal and semi-dust event days. The highest mean PM concentrations were observed in March 2011. The low PM_2.5/PM₁₀ ratios indicate that these PM are mostly originating from natural sources such as dust storms. The overall mean concentration of total bacteria during the study period was 620.6 CFU/m³. The greatest bacterial concentrations were observed during dust event days and at areas with high traffic and more human activities compared with normal days and greener areas. The percentage of gram-positive bacteria was significantly higher than that during the study period (89 vs 11 %). During this study, 26 genera of culturable bacteria were identified from all the sampling stations. The most dominant genera in all sampling stations were Streptomyces, Bacillus, Kocuria, Corynebacterium, and Paenibacillus. The results also showed that there were positive correlations between PM and bacterial concentrations during the study period (p < 0.05).     

感耦等离子体发射光谱法研究土壤—铁芒萁系统中稀土元素的分布、累积和迁移特征

用感耦等离子体发射光谱法（ICP－AES）测定了东西赣南地区非稀土矿区和4处不同稀土矿区内,土壤－铁芒萁系统中La、Ce、Pr、Nd、Sm、Gd、Dy、Yb和Y的含量,并对其在土壤剖面层及铁芒萁植物体内的分布、迁移特征进行了研究,结果表明,土训层的底土层含量最高,但表土层铈相对富集、稀土元素总量（∑REE）在铁芒萁植物体内的分布规律是叶＞根＞茎＞叶柄,单一稀土的分布规律各异,La、Ce、Pr、Nd的分布规律表现为：叶＞根＞茎＞叶柄;Sm和Gd在不同采样点表现为叶＞根＞茎＞叶柄或根＞叶＞茎＞叶柄;Dy、Yb和Y均有3种不同的分布模式：叶＞根＞茎＞叶柄、根＞叶＞茎＞叶柄及根＞茎＞叶＞叶柄,稀土元素在铁芒萁体内的迁移过程中,发生了明显的分馏作用,茎、叶柄、叶中的重稀土相对贫乏。     

Characterization,source apportionment,and human health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in road dust of a small island state in the Caribbean

Sixty-four and fifty-six road dust samples were collected over two seasons from various locations throughout the island of Trinidad and analyzed for the 16 priority PAHs. Total PAH concentrations ranged from 21 ng g^?1 to 4723 ng g^?1 (d.w.) for the rainy season and 36 ng g^?1 to 2428 ng g^?1 (d.w.) for the dry season. The Σ4–6 ring PAHs accounted for 88% and 63% of the 16 PAHs in road dust samples for the rainy and dry seasons, respectively. PAH diagnostic ratios, principal component analysis, and cluster analysis revealed both pyrogenic and petrogenic sources in road dust for the two seasons, with major contributions from vehicular emissions. Contributions from incomplete combustion and petroleum sources were also identified. The estimated Incremental Lifetime Cancer Risk (ILCR) associated with exposure to road dust PAHs in Trinidad for the rainy and dry seasons indicated no potential risk for both children and adults, as denoted by ILCR values lower than 10^?6.     

Bioaccessibility-Based Risk Assessment of PAHs in Soils from Sites of Different Anthropogenic Activities in Lagos,Nigeria Using the Fed Organic Estimation Human Simulation Test Method

The aim of this study was to carry out a bioaccessibility-based risk assessment of polycyclic aromatic hydrocarbons (PAHs) in soils from sites of different anthropogenic activities in Lagos, Nigeria. Using an in vitro gastrointestinal model—Fed Organic Estimation Human Simulation Test method (FOREShT), the concentration of bioaccessible 16 priority US Environmental Protection Agency (USEPA) PAHs in soils were determined. Total concentration of 16 priority USEPA PAHs was also determined. The concentration range was 702–253,922 ng g^?1 and 92–760 ng g^?1 for total and bioaccessible PAHs, respectively. For persons involved with activities at these sites no health risks were observed, based on bioaccessibility values of PAHs. Mean daily intake of PAHs from these soils were below the oral mean daily intake threshold for PAHs in food. Also, overall estimated theoretical cancer risk (2.5 × 10^?09, 6.5 × 10^?07, 5.5 × 10^?10, 2.7 × 10^?09, 6.5 × 10^?10, 9.5 × 10^?10, 2.0 × 10^?09, and 4.1 × 10^?07 for the eight sites based on their bioaccessible concentration) for exposure to PAHs in surface soils were below the health guidelines for extreme (1 × 10^?04) and normal (1 × 10^?06) exposures.     

Photosynthetic Characterization of the Plant Dicranopteris dichotoma Bernh. in a Rare Earth Elements Mine

In order to investigate the distribution of rare earth elements （REEs） in the natural hyperaccumulator fern Dicranopteris dichotoma Bernh. and to characterize this plant photosynthetically, concentrations of REEs in D. dichotoma from mines mining heavy and light REEs （HREEs and LREEs, respectively）, as well as in D. dichotoma from an area in which no mining occurred, in southern Jiangxi Province were determined using inductively coupled plasma-mass spectrometry. The REE concentrations in the lamina of D. dichotoma were in the order LREEs mine 〉 HREEs mine 〉 non-mining area. The maximum REE content in the lamina of D. dichotoma from the LREE mine was approximately 2 648 mg/kg dry weight. The photosynthetic activity of D. dichotoma from areas of HREE and LREE mines was improved by the presence of high concentrations of REEs in the lamina compared with D. dichotoma from the non-mining area. However, this enhancement varied according to the concentrations of the REEs, as well as their type. In addition, 77K fluorescence, electron transport rate, and chlorophyll-protein complex studies showed that the enhancement of the photosynthetic activity of D. dichotoma from HREE mines was mainly due to an increase in the chlorophyll-protein complex of the reaction center of photosystem （PS） Ⅰ, whereas the enhancement observed in D. dichotoma from LREE mines was due to an increase in the internal antennae chlorophyll-protein complex of PS Ⅱ and greater light energy distribution to the light-harvesting chlorophyll-protein complex of PS Ⅱ.     

感耦等离子体发射光谱法研究土壤-铁芒萁系统中稀土元素的分布、累积和迁移特征

用感耦等离子体发射光谱法(ICP-AES)测定了江西赣南地区非稀土矿区和处不同稀土矿区内,土壤-铁芒萁系统中La、Ce、Pr、Nd、Sm、Gy、Db、Yb和Y的含量,并对其在土壤剖面层及铁芒萁植物体内的分布、迁移特征进行了研究.结果表明,土壤剖面层的底土层含量最高,但表土层铈相对富集.稀土元素总量(∑REE)在铁芒萁植物体内的分布规律是叶＞根＞茎＞叶柄,单一稀土元素的分布规律各异,La、Ce、Pr、Nd的分布规律表现为:叶＞根＞茎＞叶柄;Sm和Gd在不同采样点表现为叶＞根＞茎＞叶柄或根＞叶＞茎＞叶柄;Dy、Yb和Y均有3种不同的分布模式:叶＞根＞茎＞叶柄、根＞叶＞茎＞叶柄及根＞茎＞叶＞叶柄.稀土元素在铁芒萁体内的迁移过程中,发生了明显的分馏作用,茎、叶柄、叶中的重稀土相对贫乏.