AM fungi increase uptake of Cd and BDE-209 and activities of dismutase and catalase in amaranth (Amaranthus hypochondriacus L.) in two contaminants spiked soil.

Soil co-contaminated with cadmium (Cd) and decabromodiphenyl ether (BDE-209) is a widespread environmental problem, especially in electronic waste contaminated surroundings. Accumulation of Cd and BDE-209 in crops has possibly harmful effects on local human health. In order to assess the potential of arbuscular mycorrhizal (AM) fungi and amaranth (Amaranthus hypochondriacus L.) in remediation of soil co-contaminated with Cd and BDE-209, pot trials were performed to investigate interactive effects of AM fungi, Cd and BDE-209 on growth of amaranth, uptake of Cd and BDE-209, distribution of chemical forms of Cd and activities of antioxidant enzymes in shoots and dissipation of BDE-209 in soil. The present results showed that shoot biomass of non-mycorrhizal plants was significantly inhibited by increasing of Cd addition (5-15 mg kg-1), but were only slightly declined with BDE-209 addition (5 mg kg-1). The interaction of Cd and BDE-209 reduced the proportions of ethanol- and d-H2O-extractable Cd in shoots, consequently alleviated Cd toxicity to plants and enhanced root uptake of Cd and BDE-209. Inoculation of AM fungi resulted in significantly greater shoot biomass as well as higher concentrations of Cd and BDE-209 compared with non-mycorrhizal treatment. Moreover, AM fungi played a beneficial role in relieving oxidative stress on amaranth by increasing the activities of dismutase (SOD) and catalase (CAT) in shoots and significantly improved the dissipation of BDE-209 in soil. The present study suggested that combination of AM fungi and amaranth may be a potential option for remediation of Cd and BDE-209 co-contaminated soils.

Mycorrhizal colonization status of lowland rice (Oryza sativa L.) in the southeastern region of China.

The accumulation, distribution, and speciation of contaminants, such as arsenic, in rice can be affected by soil microorganisms such as arbuscular mycorrhizal fungi (AMF). As a potential measure to control contaminant acquisition in rice, the status and performance of AMF in the field need to be investigated. Root samples of rice plants were collected in seven different cities in Guangdong, Jiangxi, Hubei, and Jiangsu Provinces in China in order to investigate the colonization rate of AMF. The total DNA of the roots was extracted, followed by PCR and sequencing, and further confirmed the existence of AMF. The highest colonization rates (19.5 ± 7.2%) were observed in samples from Huizhou City, Guangdong Province. Sequences of ribosomal DNA derived from Pingtan (PT) and Shuikou (SK) in Huizhou shared a similarity of 73 and 86% to Glomus cf. clarum Att894-7 (FM865542) and "uncultured fungus" (EF434122.1), respectively. The moisture tolerance of the AMF from different sources was tested by subjecting to different levels of water content in the soil. Only AMF from PT, SK, and LJ colonized rice under a condition of 100% of the soil water holding capacity (WHC), but not those isolated from upland plants. The AM colonization rate could be governed by the lighting conditions and temperature. AMF isolated in paddy fields has been shown to have more tolerance to moisture than other upland species. Radial oxygen loss (species and stress dependent) could be an essential factor influencing the colonization rate and requires more investigation.

[The Ion Identification and Molecular Logic Gate of a Thiacalix[4]arene Fluorescent Probe].

A disubstituted phthalimide-based thiacalix[4] arene derivative (probe s1) was synthesized from cone 1, 3-thiacalix[4] arene and hydroxyethyl phthalimide, with benzyl appended the lower edge of thiacalix[4]-arene by triazole ring in the 2,4 position. The relative fluorescence quantum yield of probe s1 is 0.43 in CH3CN solvent. The strong fluorescence emission of probe s1 at 390 nm wavelength can be selectively quenched by Fe3+ in DMF/H2O solution. Similarly, the presence of I- also induced a significant fluorescence quenching of probe s1 at 310 nm wavelength in CH3CN solution. Spectral titration and isothermal titration calorimetry were showed that probe s1 with Fe3+ or I- both form 1 : 1 complexes, the binding constants up to 10(5) and coordinate process were spontaneous. The linear ranges of fluorescence detect Fe3+ or I- were 1.0 x 10(-7) - 1.6 x 10(-4) mol x L(-1) and 1.0 x 10(-7) - 8.5 x 10(-5) mol x L(-1), detection limits were up to 2.30 x 10(-8) mol x L(-1) and 1.17 x 10(-8) mol x L(-1), respectively. Meanwhile, take advantage of identification and coordination action, a logic circuit constructed at the molecular level by controlling two input signals of Fe3+ and F-, which causing probe s1 cycling of fluorescence emission or quenching. IR spectrum speculated that the nitrogen atoms of triazole groups are involved in the complexation with Fe3+, while the hydrogen atoms of triazole groups were complexed with I- by hydrogen bonding.

Size fraction effect on phthalate esters accumulation, bioaccessibility and in vitro cytotoxicity of indoor/outdoor dust, and risk assessment of human exposure.

Indoor and outdoor dusts from two urban centers in the Pearl River Delta, China, were analyzed and phthalate esters varied from 4.95 to 2,220 µg g(-1) in indoor dust, significantly higher than outdoor dust (1.70-869 µg g(-1)). Di-2-ethylhexyl phthalate (DEHP) was the dominant phthalate found and the highest distribution factor (DF) (1.56 ± 0.41) was noted in the <63 µm fraction (p<0.05). In vitro cytotoxicity of dust extract on human T cell lymphoblast leukemic cell line (CCRF-CEM) indicated by Lethal Concentration 50 (LC50) decreased with particle size. The power model was found as a better fit for explaining the relationship between LC50 and phthalates (R(2)=0.46, p<0.01). Bioaccessibility of phthalates in dust varied with different particle sizes, with the greatest bioaccessible fraction (2.49-38.6%) obtained in <63 µm. Risk assessment indicated that indoor dust ingestion accounted for the major source for DEHP exposure (81.4-96.4% of non-dietary exposure and 36.5% of total exposure), especially for toddlers. The cancer risks associated with DEHP via home dust were high (10(-6)-10(-4)), with 10% of houses estimated with unacceptable risks (>10(-4)). After corrected with the bioaccessibility of phthalates, the cancer risks of dust exposure were moderate (10(-7)-10(-5)).

Root exudates of wetland plants influenced by nutrient status and types of plant cultivation.

The present study investigated the amounts of root exudates and composition of organic acids released from two wetland plants (Typha latifolia and Vetiver zizanioides) under two nutrient treatments: low level (0.786 mM N and 0.032 mM P) and high level (7.86 mM N and 0.32 mM P) and two types of plant cultivation: monoculture and co-culture of the two plants. Low nutrient treatment significantly (p < 0.05) increased the root exudates of T. latifolia during the initial growth period (1-21 d) and those of V. zizanioides and the co-culture during the whole growth period. The concentrations of dissolved organic carbon in the root exudates of the co-culture in the low nutrient treatment were 3.23-7.91 times of those in the high nutrient treatment during the medium growth period (7-28 d). The compositions of organic acids varied between the two plant species and between the two nutrient treatments. The pattern of organic acids was also different between the co-culture and the monoculture. Oxalic acid was by far the major organic acid exuded from the two wetland plants. The present study on root exudates suggests that co-culture of wetland plant species would be more useful in the reclamation of waste water than a monoculture system.

The influence of mariculture on mercury distribution in sediments and fish around Hong Kong and adjacent mainland China waters.

To study the influence of mariculture on mercury (Hg) speciation and distribution in sediments and cultured fish around Hong Kong and adjacent mainland China waters, sediment samples were collected from six mariculture sites and the corresponding reference sites, 200-300 m away from the mariculture sites. Mariculture activities increased total mercury, organic matter, carbon, nitrogen and sulfur concentrations in the surface sediments underneath mariculture sites, possibly due to the accumulation of unconsumed fish feed and fish excretion. However, methylmercury (MeHg) concentrations and the ratio of MeHg to THg (% MeHg) in sediments underneath mariculture sites were lower than the corresponding reference sites. The % MeHg in sediments was negatively correlated (r = -0.579, p < 0.05) with organic matter (OM) content among all sites, indicating that OM may have inhibited Hg methylation in surface sediments. Three mariculture fish species were collected from each mariculture site, including red snapper (Lutjanus campechanus), orange-spotted grouper (Epinephelus coioides) and snubnose pompano (Trachinotus blochii). The average MeHg concentration in fish muscle was 75 µg kg⁻¹ (wet weight), and the dietary intake of MeHg through fish consumption for Hong Kong residents was 0.37 µg kg⁻¹ week⁻¹, which was lower than the corresponding WHO limits (500 µg kg⁻¹ and 1.6 µg kg⁻¹ week⁻¹).

Oral bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) through fish consumption, based on an in vitro digestion model.

An in vitro gastrointestinal digestion model was used to evaluate bioaccessibility of PAHs in 20 fish species collected from Hong Kong markets. The average bioaccessibilities of PAHs were 24.3 and 31.1%, respectively, in gastric and intestinal conditions. When bioaccessibility was taken into consideration, the values of potency equivalent concentrations (PEC) decreased from 0.53 to 0.18 ng g(-1) for freshwater fish and from 1.43 to 0.35 ng g(-1) for marine fish. This indicated that bioaccessibility should be taken into account for health risk assessment with regard to PAH contamination in fish. The relative accumulation ratios (R(nn)) of PAH congeners were significantly correlated with their physicochemical parameters and their corresponding concentrations reported in subcutaneous fats of Hong Kong residents. The data suggest that R(nn) values calculated in the present study could effectively reflect the accumulations of PAHs in the human body.

The effect of arbuscular mycorrhizal fungi and phosphate amendement on arsenic uptake, accumulation and growth of Pteris vittata in As-contaminated soil.

This study investigated the contributions of mixed arbuscular mycorrhizal fungi (AMF) inoculum-i.e., mixed populations of indigenous mycorrhiza (Glomus intraradices, Glomus geosporum, Glomus mosseae) (IM) isolated from arsenic (As) contaminated soil and non-indigenous mycorrhiza such as G. mosseae (GM), which possess metal tolerance characteristics-and the addition of phosphate rock (PR) towards the uptake and accumulation of As by Pteris vittata (As hyperaccumlator) grown in As-contaminated soil. Regardless of As levels added to soil, plant growth was substantially improved in amended treatments when compared with the control. In addition, root surface area (0 mg/kg As: 15.2 cm2; 150 mg/kg As: 16.9 cm2; 300 mg/kg As: 20.7 cm2), chlorophyll contents (0 mg/kg As: 1.16 mg/g; 150 mg/kg As: 1.46 mg/g; 300 mg/kg As: 1.81 mg/g) and As translocation factor (0 mg/kg As: 0; 150 mg/kg As: 4.29; 300 mg/kg As: 5.22) in P. vittata of PR+IM/GM were also increased. Such combination could further enhance plant growth (indicated by higher N, P and chlorophyll contents) and As uptake by P. vittata.

Effects of root anatomy and Fe plaque on arsenic uptake by rice seedlings grown in solution culture.

Hydroponic experiments were carried out to investigate the effects of root anatomy, induced by aeration and stagnation, and Fe plaque on arsenic (III&V) uptake and translocation by rice plants. The results showed that As uptake in rice plants (Gui Chao-2) treated by aeration was decreased due to lower root specific surface area. Rice roots with larger specific surface area tended to form more Fe plaque, and Fe plaque affected As uptake kinetics by changing As influx curves from linear to hyperbolic for As(III) and from hyperbolic to S-curve for As(V). Fe plaque increased As(III&V) adsorption and minimized the effects of root anatomy characteristics on As uptake into roots and subsequently translocation to shoots. Fe plaque increased As(III) uptake rate at As(III) concentrations of 0.5 to approximately 8 mg L(-1), reduced As(V) uptake rate at low As(V) concentrations (<2 mg L(-1)), but increased As uptake rate at high As(V) concentrations (>6 mg L(-1)).