Neurotoxicity of tetramethylammonium ion on larval and juvenile zebrafish: Effects on neurobehaviors and multiple biomarkers.

Tetramethylammonium hydroxide (TMAH) is an important compound that utilized and released by the rapidly expanding semiconductor industry, which could hardly be removed by the conventional wastewater treatment techniques. As a cholinergic agonist, the tetramethylammonium ion (TMA+) has been reported to induce toxicity to muscular and respiratory systems of mammals and human, however the toxicity on aquatic biota remains poorly known. We investigated the neurotoxic effects of TMA+ exposure on zebrafish, based on neurobehavior tests and a series of biomarkers. Significant inhibitions on the swimming distance of zebrafish larvae were observed when the exposure level exceeded 50 mg/L, and significant alterations on swimming path angles (straight and deflective movements) occurred even at 10 mg/L. The tested neurobehavioral endpoints of zebrafish larvae were significantly positively correlated with reactive oxygen species (ROS) and malondialdehyde (MDA), significantly negatively related with the activities of antioxidant enzymes, but not significantly correlated with the level of acetylcholinesterase (AChE). Such relationship indicates that the observed neurotoxic effects on swimming behavior of zebrafish larvae is mainly driven by oxidative stress, rather than the alterations of neurotransmitter. At the highest exposure concentration (200 mg/L), TMA+ evoked more severe toxicity on zebrafish juveniles, showing significantly stronger elevation on the MDA activity, and greater inhibitions on the activities of antioxidant enzymes and AChE, suggesting juveniles were more susceptible to TMA+ exposure than larval zebrafish.

Variations in Hydraulic Conductivity of Montmorillonite in Dual-Cation Electrolyte Solutions.

The hydraulic conductivity of Na-montmorillonite in dual-cation solutions of Na+ and Mn+ (Mn+ = K+, Ca2+, Zn2+ and Al3+) with a constant ionic strength of 0.1 mol/L was determined. The focus of this study was on the influence of Mn+ on the grain-size distribution of montmorillonite and hence its hydraulic conductivity. All the tested cations showed a high affinity towards montmorillonite, and the high valency favored the exchange between Mn+ and Na+. The hydraulic conductivity of montmorillonite increased to the maxima and then decreased in a left-skewed log-normal shape as the cation exchange progressed. The grain size of montmorillonite concurrently decreased monotonically with the cation exchange. The XRD patterns of montmorillonite confirmed the occurrence of demixing of Na+ and K+ in the interlayers. It is proposed that the rearrangement and reaggregation of grains during cation exchange occurred, leading to variations in the hydraulic conductivity of montmorillonite.

Lindane degradation in wet-dry cycling soil as affected by aging and microbial toxicity of biochar.

This study determined the degradation of lindane in soil amended with biochar to evaluate the effects of biochar aging and microbial toxicity. Two biochars were prepared at 400 and 600 °C (BC400 and BC600) and subjected to acid washing to remove nutrition (WBC400 and WBC600). After 89 days of incubation under the alternate "wet-dry" conditions, scanning electron microscopy showed that acid washing rendered biochars especially susceptible to aging with structural collapse and fragmentation, with less surface covering. Aging impeded the release of toxic substances in BC400 and BC600 with reduced toxicity to degrading microorganisms. Lindane degradation was somewhat stimulated by biochar nutrition but mainly inhibited by adsorption. Acid washing facilitated the release of toxic substances and additionally reduced lindane degradation. The variations in fatty acid saturation degree (SFA/UFA) in soils confirmed the microbial toxicity of 5% WBC400 > 5% BC400 > 5% BC600 > 5% WBC600. High-throughput DNA sequencing showed that biochar delayed the formation of dominant degrading microbial communities in soil. Lindane degradation was completed by joint Sphingomonas, Flaviolibacter, Parasegetibacter, Azoarcus, Bacillus and Anaerolinaea. These findings are helpful for better understanding the effect of biochar in soil on long-term degradation of persistent organic pollutants.

Enhanced removal of cadmium from wastewater with coupled biochar and Bacillus subtilis.

Shortcomings of individual biochar or microbial technologies often exist in heavy metal removal from wastewater and may be circumvented by coupled use of biochar and microorganisms. In this study, Bacillus subtilis and each of three biochars of different origins (corn stalk, peanut shell, and pine wood) were coupled forming composite systems to treat a cadmium (Cd, 50 mg/L) wastewater formulated with CdCl2 in batch tests. Biochar in composite system enhanced the activity and Cd adsorption of B. subtilis. Compared with single systems with Cd removal up to 33%, the composite system with corn stalk biochar showed up to 62% Cd removal, which was greater than the sum of respective single B. subtilis and biochar systems. Further analysis showed that the removal of Cd by the corn stalk composite system could be considered to consist of three successive stages, that is, the biochar-dominant adsorption stage, the B. subtilis-dominant adsorption stage, and the final biofilm formation stage. The final stage may have provided the composite system with the ability to achieve prolonged steady removal of Cd. The biochar-microorganism composite system shows a promising application for heavy metal wastewater treatment.

Relation of tributyltin and triphenyltin equilibrium sorption and kinetic accumulation in carp and Ceratophyllum demersum.

Comparatively limited knowledge is known about the accumulation processes of tributyltin (TBT) and triphenyltin (TPT) in fish and aquatic plant in the freshwater environment, which has hindered a full understanding of their bioaccumulation potential and ecological risks. In the present study, sorption of TBT and TPT on dead biota of both carp and C. demersum from water via the batch equilibrium technique as well as uptake of them on live biota of both carp and C. demersum from water at a static and a dynamic kinetics tests were investigated, respectively. Both TBT and TPT exhibit a high affinity in carps and C. demersum. And C. demersum has a faster metabolism either for TBT or TPT than carp. The apparent uptake values (Cbio = 1904-8831 µg/kg) or bioconcentration factor (BCF = 3333-44000 L/kg) were one or two orders of magnitude higher than that of estimated by a simple sorption (405-472 µg/kg) or lipid model (74.5-149.6 µg/kg) for carp, indicating the uptake of TBT and TPT did not only depend on lipids but also oxygen ligands or macromolecules such as amino acids and proteins of the living organism. In contrast, the apparent Cbio values (149.1-926.4 µg/kg) of both TBT and TPT were lower than that of estimated by sorption model (1341-1902 µg/kg) for C. demersum, which were due to the rapid metabolic rate of them, especially for TBT. But no relation was observed between TBT and TPT concentrations and lipid contents in C. demersum.

Optimized mid-long term management of ketogenic diet in children with refractory epilepsy.

This study aims to explore the mid-long term management of ketogenic diet (KD) for the treatment of refractory epilepsy in children, and carry out an efficacy assessment. The data of epileptic children who received KD in our hospital from January 2011 to August 2012 (basic management plan group, n=57) were retrospectively analyzed. On this basis, epileptic children who received KD from September 2012 to April 2014 (optimized management plan group, n=52) were managed according to the mid-long term management plan. The effective rate of KD at the first, third, sixth and ninth month was 90.4%, 73.1%, 65.4% and 38.5%, respectively, in the optimized management plan group, and 63.2%, 45.6%, 38.6% and 21.1%, respectively, in the basic management plan group, and the differences were statistically significant. The compliance rate of KD at the third, sixth and ninth month was 94.2%, 78.8% and 63.5%, respectively, in the optimized management plan group, and 82.5%, 47.4% and 28.1%, respectively, in the basic management plan group, and the differences were statistically significant. Optimized mid-long term management of KD in children can improve the control rate of epileptic seizures, and the compliance of patients.

Removal of dichlorophenol by Chlorella pyrenoidosa through self-regulating mechanism in air-tight test environment.

Microalgae are surprisingly efficient to remove pollutants in a hermetically closed environment, though its growth is inhibited in the absence of pollutants. The final pH, algal density, Chl-a content, and the removal efficiency of 2,4-dichlorophenol (2,4-DCP) by Chlorellar pyrenoidosa in a closed system were observed under different initial pH, lighting regimes, and various carbon sources. The optimal condition for 2,4-DCP removal was obtained, and adopted to observe the evolution of above items by domesticated and origin strains. The results showed that both respiration and photosynthesis participated in the degradation of 2,4-DCP, and caused the changes of pH. The photosynthesis seemed to increase the solution pH, while the respiration and the biodegradation of 2,4-DCP to decrease the solution pH. The domesticated strain achieved nearly 100% removal when initial concentrations of 2,4-DCP lower than 200 µg L-1, due to providing a appropriate but narrow pH evolution range, mostly falling between 6.5 and 7.9. The research helps to understand the mechanism of biodegradation of chlorophenol compounds by green algae.

Cosolvent Effects on Dechlorination of Soil-Sorbed Polychlorinated Biphenyls Using Bentonite Clay-Templated Nanoscale Zero Valent Iron.

Zero-valent iron synthesized using bentonite clay as a template (CZVI) was tested for its reactivity toward polychlorinated biphenyl (PCB) dechlorination in soil slurries. Aqueous-phase decachlorobiphenyl (PCB209) was rapidly dechlorinated by CZVI with a reaction rate 10 times greater than that by conventional nanoscale zerovalent iron. This superior reactivity was due largely to the nanoscale size (∼0.5 nm) of the ZVI particles located in the clay galleries. In soil slurries where PCB209 was strongly soil-bound, adding ethanol as an organic cosolvent led to increased PCB209 desorption into the liquid phase, thereby enhancing the PCB209 dechlorination with CZVI. The more effective PCB209 dechlorination in such a cosolvent system also promoted the subsequent stepwise dechlorinative process, leading to a relatively more removal of chlorine in the product mixture. The dechlorination became more rapid as the ethanol fraction increased from 10% to 50%, due apparently to the increasingly greater PCB209 desorption and thus facilitated contact with CZVI. Further increase in ethanol fraction above 50% led to an insignificant enhancement in degradation rate, due partially to attenuated contact of PCB209 with CZVI and reduced proton source from limited water content in the liquid. It is suggested that addition of organic cosolvents may make CZVI potentially useful for remediation of soils containing halogenated organic contaminants.

Internalization and Phytotoxic Effects of CuO Nanoparticles in Arabidopsis thaliana as Revealed by Fatty Acid Profiles.

Internalization and phytotoxic effects of CuO nanoparticles (nCuO) in plants were studied at the cellular level. Arabidopsis thaliana was hydroponically challenged by nCuO (100 mg/L), as compared to Cu2+ ions (1.2 mg/L), to account for nCuO dissolution for 96 h and 28 days to monitor Cu accumulation in the plant as well as the fatty acid (FA) profiles of the plant cell membrane. Under the same growing conditions, the nCuO exposure resulted in more Cu accumulation than did the Cu2+ exposure. Multiple microscopic techniques confirmed the internalization and sequestration of nCuO in root cell vacuoles, where transformation of Cu(II) to Cu(I)Cl occurred. Short and long exposures (96 h versus 28 days) to both nCuO and Cu2+ elevated FA saturation degrees in plant cells through oxidative stress, as verified by in situ detection of superoxide radicals, with conversions mostly from C18:3, C16:3, and C18:2 to C16:0. Only the long exposure to nCuO significantly brought about an additional elevation of FA saturation degree in root cells. These results demonstrated that the acute effects of plant exposure to nCuO were mainly produced from the stress of Cu2+ ions released from nCuO dissolution, while the chronic effects in roots were significantly developed by the nCuO particle stress. The findings in this work are novel and may offer significant implications in better understanding nanoparticle-induced phytotoxicity and potential risks in ecosystems.

Corrigendum Effects of probucol on cultured human umbilical vein endothelial cells injured by hypoxia/reoxygenation - Genet. Mol. Res. 15 (1): gmr.15016752.

Published online: March 4, 2016 (DOI: 10.4238/gmr.15016752). Corrected after publication: June 3, 2016 (DOI: 10.4238/gmr.150267521). The information of authors' affiliations is as follows: Y. L. Chai(1,2), J.Z. Xu(1), Y.L. Zhang(1) and G.T. Sheng(2). (1)Department of Cardiovascular Medicine, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning, China. (2)No.1 Department of Cardiovascular Medicine, People's Hospital of Jiangxi Province, Nanchang, Jiangxi, China.

Effects of probucol on cultured human umbilical vein endothelial cells injured by hypoxia/reoxygenation.

There is increasing evidence suggesting that endoplasmic reticulum stress (ERS) plays an important role in the initiation and development of atherosclerosis. This study was designed to examine the effect of probucol on cultured human umbilical vein endothelial cells (HUVECs) injured by hypoxia/reoxygenation (H/R) and the potential mechanisms involving ERS. Injured HUVECs induced by Na2S2O4 served as an H/R model in vitro. The concentration of probucol in this study ranged from 3 to 27 µM. Cell viability was analyzed using MTT and a lactate dehydrogenase (LDH) assay. The expression of GRP78, X-box-binding protein (XBP)-1, and CHOP (c/EBP-hemologous protein) were quantified using western blot. Compared to cells with H/R injury alone, the results showed that the cell viability increased significantly with probucol, while the LDH leakage rate was significantly lower as analyzed by the LDH assay. Furthermore, the expression levels of GRP78, XBP-1, and CHOP were significantly downregulated. These results indicated that probucol effectively protected HUVEC from injury induced by H/R and that the mechanism might be related to attenuation of ERS.

[Inhibitory effect of migration-inducing gene-7-shRNA recombinant retrovirus combined with endostatin on growth and metastasis of hepatoma xenograft].

Objective: To investigate the inhibitory effect of migration-inducing gene-7(Mig-7)interfered with retrovirus-mediated RNA(shRNA)combined with recombinant human endostatin(ES)on the growth and metastasis of subcutaneous xenograft of human hepatoma cells in nude mice. Methods: Two Mig-7-mRNA oligonucleotide sequences(Mig-7-shRNA-1 and Mig-7-shRNA-2)and one sequence as a negative control(Mig-7-shRNA-N)were designed. The specific Mig-7-shRNA recombinant retrovirus expression vector plasmid was constructed and used for the transfection of human hepatoma MHCC-97H cells with high expression of Mig-7. The subcutaneous xenograft tumor model of human hepatocellular carcinoma(HCC)in nude mice was established, and according to the condition of transfection and administration, the nude mice were divided into pSIREN-M1 group, pSIREN-MN group, ES group, and pSIREN-M1+ES group. The xenograft tumor volume, mass, and metastasis were compared between groups. Immunohistochemistry was used to observe the formation of vasculogenic mimicry(VM)in xenograft tumor and the difference in tumor microvascular density(MVD), and Western blot was used to measure the expression of Mig-7 and vascular endothelial growth factor(VEGF)in each group. A one-way analysis of variance was used for comparison between groups, and the Fisher's exact test was used for comparison of continuous data between groups. Results: Compared with the pSIREN-MN group, the pSIREN-M1 group had significantly lower xenograft tumor volume, mass, and metastasis rate, Mig-7 expression, and formation of VM(P < 0.05), as well as significantly higher VEGF expression and MVD(P < 0.05). Compared with the pSIREN-MN group, the ES group had significantly lower xenograft tumor volume, mass, and metastasis rate, VEGF expression, and MVD(P < 0.05), as well as significantly higher Mig-7 expression and formation of VM(P < 0.05). Compared with the pSIREN-M1 group and the ES group, the pSIREN-M1+ES group had significantly lower xenograft tumor volume, mass, and metastasis rate, Mig-7 expression, formation of VM, VEGF expression, and MVD(P < 0.05). Conclusion: Mig-7-shRNA recombinant retrovirus combined with ES has a better inhibitory effect on the growth and metastasis of HCC xenograft tumor than Mig-7-shRNA recombinant retrovirus or ES alone. The anti-tumor angiogenesis therapy alone, which targets vascular endothelial cells in vivo, has a limited effect, since it may promote the formation of VM.

Ara-C and anti-CD47 antibody combination therapy eliminates acute monocytic leukemia THP-1 cells in vivo and in vitro.

Leukemia stem cells (LSCs) are regarded as the origin of leukemia and its recurrence. Side population (SP) cells possess some intrinsic stem cell properties and contain numerous LSCs. In this study, we examined the prognostic significance of cluster differentiation 47 (CD47) and identified the appropriate target for eliminating LSCs. We determined the percentage of SP cells in a THP-1 cell population and analyzed CD47 expression in different cell subsets. We then explored whether CD47 affected the phagocytic ability of macrophages to LSCs in vitro. Finally, the effect of anti-CD47 monoclonal antibodies, alone or combination with cytarabine, against leukemic cells was evaluated in vitro and in vivo to identify the optimal targets for the treatment of leukemia. We observed an SP sub-fraction at low frequency (1.81 ± 0.99%), which was a likely candidate for LSC enrichment. CD47 was more highly expressed on THP-1 LSCs (P < 0.05) and was an independent predictor of survival and refractory disease in THP-1-engrafted mice. Furthermore, the anti-CD47 monoclonal antibody stimulated preferential phagocytosis of LSCs by macrophages in vitro. Finally, single or combination treatment of THP-1 LSC-engrafted mice with cytarabine and anti-CD47 antibody resulted in targeting of LSCs and depletion of leukemia cells. These findings suggest that CD47 is an antibody target in LSCs and combination treatment with cytarabine and anti-CD47 monoclonal antibody represents an attractive option for the therapeutic targeting of acute monocytic leukemia.

Distribution and spatial variation of volatile methylsiloxanes in surface water and wastewater from the Yangtze River Basin, China.

Volatile methylsiloxanes (VMSs) earned serious concerns due to their detection and toxicities after their release to the environments. They were also detected in rivers around the globe, but their distribution remained to be explored in larger rivers with longer length, higher water volume and wider watershed. In the present study, 8 cyclic VMSs (cVMSs) and 7 linear ones (lVMSs) were investigated in 42 water samples (27 surface water (including 7 drinking source water) and 15 wastewater) from the Yangtze River Basin, China. Results showed that VMSs were detected in all sampling sites. In surface water, the concentrations of total cVMSs ranged from 17.3 to 4.57 × 103 ng/L, while those of lVMSs ranged from 1.72 to 81.6 ng/L. In wastewater, the total concentrations of cVMSs and lVMSs showed ranges of 17.6-1.66 × 103 ng/L and 2.59-252 ng/L, respectively. Apparently, cVMSs showed significantly higher concentrations than lVMSs. The concentrations of cVMSs followed an order of lower > upper > middle reaches, while those of lVMSs did not show clear distribution patterns. Among cVMSs, those with less Si numbers were dominant, while those with more Si numbers were dominant in lVMSs. Notably, the VMSs were also detected in 7 surface waters that served as drinking source waters, which earned them further concerns. In addition, the VMSs in surface water showed positive correlation with those in wastewater, which led to necessity in management on industrial emissions in the future.

Geochemical controls on the distribution and bioavailability of heavy metals in sediments from Yangtze River to the East China Sea: Assessed by sequential extraction versus diffusive gradients in thin-films (DGT) technique.

This study conducted a comprehensive investigation on the distribution and bioavailability of heavy metals (Cr, Co, Ni, Cu, Zn, Cd and Pb) in sediments along two typical transects from Yangtze River to the East China Sea continental shelf that spanning large physicochemical gradients. Heavy metals were mainly associated with the fine-grained sediments (enriched with organic matter), exhibiting decreasing trends from nearshore to offshore sites. The turbidity maximum zone showed the highest metal concentrations, which evaluated as polluted for some tested metals (especially Cd) using the geo-accumulation index. Based on the modified BCR procedure, the non-residual fractions of Cu, Zn and Pb were higher within the turbidity maximum zone, and significantly negatively correlated with bottom water salinity. The DGT-labile metals all positively correlated with the acid-soluble metal fraction (especially for Cd, Zn and Cr), and negatively correlated with salinity (except Co). Therefore, our results suggest salinity as the key factor controlling metal bioavailability, which could further modulate metal diffusive fluxes at the sediment-water interface. Considering that DGT probes could readily capture the bioavailable metal fractions, and reflect the impacts of salinity, we suggest DGT technique can be used as a robust predictor for metal bioavailability and mobility in estuary sediments.

Orthorhombic BiFeO3.

A new orthorhombic phase of the multiferroic BiFeO3 has been created via strain engineering by growing it on a NdScO(3)(110)(o) substrate. The tensile-strained orthorhombic BiFeO3 phase is ferroelectric and antiferromagnetic at room temperature. A combination of nonlinear optical second harmonic generation and piezoresponse force microscopy revealed that the ferroelectric polarization in the orthorhombic phase is along the in-plane {110}(pc) directions. In addition, the corresponding rotation of the antiferromagnetic axis in this new phase was observed using x-ray linear dichroism.

Altered transfer of heavy metals from soil to Chinese cabbage with film mulching.

The influence of film mulching on the migration of metals from soil to cabbage was investigated. Following a 50-day growth in field plots mulched or unmulched, root-zone soils and Chinese cabbage (Brassica chinensis L.) were sampled for metal analysis. Mulching slightly decreased the soil mobile (acid-extractable) Cd, but increased its transfer from root to the cabbage parts. As an essential element, Cu was readily transferred to the cabbage parts. While mulching decreased the soil mobile Zn, reduced soil pH resulted in its enhanced soil-to-root migration. This, however, did not increase the transfer of Zn within cabbage. Although mulching increased the soil mobile Pb by 200%, an increase in Pb in cabbage leaves but a decrease in stem result presumably from the enhanced foliar uptake of atmospheric Pb. This study suggests that mulching may promote the accumulation of toxic metals such as Cd and Pb in cabbage and therefore increase crop risks to human health.

Lindane uptake and translocation by rice seedlings (Oryza sativa L.) under different culture patterns and triggered biomass re-allocation.

The study was conducted to investigate the influence of the culture pattern on plant uptake and translocation of an organic chemical and the resultant acute response of plants, and to further reveal the interconnection. Plant exposure experiments were performed using a conventional rice seedling (Oryza sativa L. subsp. indica) under two kinds of culture patterns (viz., hydroponics and soil-based culture) with various culture matrices for a period of 7 days. The exposure concentration of lindane was ∼450 µg L-1 in the aqueous-phase matrices, and 200.1-756.0 µg kg-1 in the solid matrices. Lindane accumulation and its distribution in plant tissues were quantified, as well as the tissue biomass. The results showed the accumulation of lindane in all exposure groups were comparatively close over the period, confirming that the soil-bound lindane was scarcely available to plants. Similar trend of lindane uptake and translocation in seedlings was found among the groups under the same kind of cultivation pattern. In the hydroponic groups, lindane was mostly distributed in roots (about 60% at the end of exposure), whereas more lindane was translocated to shoots (approximate 70%) under the soil-based culture pattern. Allometric analysis demonstrated that the tissue part (root or shoot) with more lindane accumulation had a relatively higher growth rate over 7 days. Correspondingly, biomass allocation presented a slight trend of mutual proximity to lindane distribution. It was inferred that plants altered their allometric growth pattern to realize biomass re-allocation in response to the short-term lindane exposure, which could be considered as a plant defense strategy.

Blocking effect of fullerene nanoparticles (nC60) on the plant cell structure and its phytotoxicity.

Blockage of nanoparticles on plant pore structures might produce phytotoxicity and affect plant uptake indirectly. This study examined the blocking and phytotoxic effects of fullerene nanoparticles (nC60) on plants at the cellular level. The malondialdehyde content in plant was normal during nC60 exposure, implying that nC60 caused no acute phytotoxicity, while the normalized relative transpiration significantly decreased, showing that the pore structure of roots was seriously blocked by nC60. High power optical microscopy and transmission electron microscope showed that root endothelial cells were squeezed, and inner wall structures were damaged by the extrusion of nanoparticles. Low nC60 concentrations inhibited root uptake of lindane, whereas high nC60 concentrations promoted root uptake of lindane, indicating that serious pore blocking by nC60 damaged root cell structure and hence ready transport of lindane from roots to shoots. Significant alterations of fatty acid (FA) saturation degree of root cell membrane indicated that nC60 led to phytotoxicity in the root cell membrane after long-term exposure and nC60 produced phytotoxicity in the process of blocking root pore structures and interfering with cell membrane fluidity. Moreover, the plant cell structures under phytotoxicity were more likely to be damaged mechanically by the extrusion of nanoparticles. These findings may be helpful to better understand the transport pathways of nanoparticles in plants, the phytotoxicity of nanoparticles and the potential risks of nanomaterials used in agriculture.

Translocation versus ion trapping in the root uptake of 2,4-dichlorophenol by wheat seedlings.

Understanding of the plant uptake of ionizable organic compounds is critical to the evaluation of crop contamination, plant protection, and phytoremediation. This study investigated the time-dependent uptake of 2,4-dichlorophenol (DCP) by intact wheat seedling roots and subsequent translocation to shoots at pH 5.0 and 8.0. Sorption of DCP by cut roots and shoots at these two pHs was conducted to provide the uptake limits and the Donnan charge. For comparison, sorption was also conducted for 1,3-dichlorobenzene (DCB), a nonionizable compound having a structure similar to that of DCP. The DCB sorption isotherms were linear and independent of pH, yielding a consistent log Klip of 3.56 with both roots and shoots, reflective of the essential dominant role of lipids in plant partition uptake. Whereas the DCP sorption also showed a linear isotherm at pH 5.0 with log Klip = 2.88, the sorption at pH 8.0 was nonlinear with a concave downward shape, especially at low concentrations. With live wheat seedlings, the DCB uptake by roots and the DCB translocation to shoots rapidly approached a steady state, showing no obvious pH effect. On the DCP uptake by live plants, there was a rapid attainment of a steady state in roots at pH 5.0 coupled with a retarded transport to shoots due presumably to the polarity of DCP. At pH 8.0, the root uptake of DCP was comparatively slower and the translocation to shoots was completely inhibited due presumably to DCP ionization. At high pH, DCP was supposedly accumulated in an ionized form in root cells via an ion-trapping mechanism.