Search

Purpose: Phosphate is one of the most frequently used fertilizers to promote the crop growth, whereas the impact of phosphate on the adsorption behaviors of cadmium (Cd) is complex. The objectives of this study were to reveal effects of pH, phosphate, and organic molecules on Cd adsorption onto soil (hydr)oxides, and to validate the reliability of the NOM-CD model in depicting effect of pH and phosphate on Cd solubility in soil systems. Materials and methods: In this study, effects of phosphate on Cd adsorption onto goethite and a paddy soil at pH 3–8 were studied by combing batch adsorption experiments with an advanced surface complexation model, i.e., natural organic matter-charge distribution (NOM-CD) model. In the NOM-CD model, the adsorption of ions onto oxides in the absence of NOM is calculated with the charge distribution and multi-site complexation (CD-MUSIC) model. Results and discussion: Adsorption of Cd onto goethite is dramatically increased with the addition of phosphate at pH 5–8, whereas effects of citric acid on Cd adsorption are weaker. The synergic co-adsorption of Cd and phosphate onto goethite, according to CD-MUSIC model, is mainly due to electrostatic attractions of these two ions instead of formation ternary surface complex. The NOM-CD model can basically predict variations of Cd solubility in the soil system, and it is observed only a slight increase of Cd solubility with phosphate addition under acidic conditions. It might be caused by competitive adsorption between NOM and phosphate to soil (hydr)oxides, which leads to a higher amount of Cd binding by dissolved organic matters in soil solution, thus inhibiting Cd adsorption. Conclusions: Electrostatic attraction dominates the co-adsorption of Cd and phosphate onto goethite, whereas the interactions between Cd-P-oxide-NOM result in negligible effects of phosphate on Cd solubility in the soil. Overall, this study revealed that the NOM-CD model could make predictions on the distribution of Cd at soil–water interface, and the outcome of this study can provide a more in-depth understanding of the factors controlling Cd solubility and mobility in contaminated soil and sediment environment. [ABSTRACT FROM AUTHOR]

Proverbs listed by Chinese college students, who are often at the leading edge of cultural change, provide a window into the dynamic interplay of traditionality and modernity. Using thematic analysis, Study 1 examined popular proverbs listed frequently by Chinese college students (n = 298) and the embedded values. Study 2, which was a survey, examined Chinese college students' (n = 240) endorsement of individualism, collectivism, and the values identified in Study 1, and the predictive associations of individualism and collectivism with the values. Findings in Study 1 revealed 103 frequently listed proverbs and eight embedded values (i.e., Learnedness, Diligence, Practical Orientation, Collective Orientation, Social Relationship, Moral Virtue, Free Spirit, and Optimism). Findings in Study 2 indicated participants endorsed Practical Orientation and Learnedness the most, followed by Diligence, Moral Virtue, Social Relationship, Collective Orientation, Optimism, and Free Spirit. Furthermore, although Chinese young adults are more individualistic than collectivistic, collectivism remains a stronger predictor of the values uncovered in the proverbs. The value dynamics in general revealed tensions and harmony between Confucianism and Daoism and the hybridisation of tradition, modernisation, and Western individualism, thus reflecting the complexity of Chinese young adults' social psychology. [ABSTRACT FROM AUTHOR]

Background: Some natural compounds inhibit cancer cell growth in various cancer cell lines with fewer side effects than traditional chemotherapy. Here, we explore the pharmacological effects and mechanisms of worenine (isolated from Coptis chinensis) against colorectal cancer. Methods: The effects of worenine on colorectal cancer cell proliferation, colony formation and cell cycle distribution were measured. Glycolysis was investigated by examining glucose uptake and consumption, lactate production, and the activities and expressions of glycolysis enzymes (PFK-L, HK2 and PKM2). HIF-1α was knocked down and stimulated in vitro to investigate the underlying mechanisms. Results: Worenine somewhat altered the glucose metabolism and glycolysis (Warburg effect) of cancer cells. Its anti-cancer effects and capability to reverse the Warburg effect were similar to those of HIF-1α siRNA and weakened by deferoxamine (an HIF-1α agonist). Conclusion: It is suggested that worenine targets HIF-1α to inhibit colorectal cancer cell growth, proliferation, cell cycle progression and the Warburg effect. [ABSTRACT FROM AUTHOR]

Environmental context: The concentration, types and distribution of antibiotics in soils can have environmental effects and can be modelled using laboratory systems. Adsorption of ofloxacin (OFL) and levofloxacin (LEV) enantiomers to goethite can probe this behaviour and each binds differently to the solid phase. The different behaviour of LEV and OFL in relation to solid-solution partitioning will affect their environmental fate. The adsorption of ofloxacin enantiomers, namely levofloxacin (LEV) and ofloxacin (OFL), to goethite was investigated using batch experiments. Structural information of aqueous and adsorbed LEV or OFL was obtained with ultraviolet–visible (UV-Vis), three-dimensional excitation–emission matrix (EEM) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopic methods. The results indicated that LEV molecules formed a bridging bidentate complex (≡(FeO)2–LEV) with the surface of goethite, and OFL formed a monodentate complex (≡FeO–OFL). The adsorption of OFL to goethite was stronger than that of LEV, owing to differences in their physicochemical properties and bonding modes. The adsorption of LEV and OFL to goethite in single systems was well simulated using the charge distribution multi-site complexation (CD-MUSIC) model, but their adsorption in the LEV–OFL–goethite systems was overestimated at pH ~5.2 and high concentrations of LEV–OFL mixture (19.59 μM), in which the predicted amounts of adsorbed LEV and OFL were higher (20.0, 30.8 %) than the experimental results. Compared with the unprotonated LEV or OFL, the protonated (>99.9 %) ones were mainly adsorbed to the surface of goethite, and the single species may be used during their following modelling. Environmental context. The concentration, types and distribution of antibiotics in soils can have environmental effects and can be modelled using laboratory systems. Adsorption of ofloxacin (OFL) and levofloxacin (LEV) enantiomers to goethite can probe this behaviour and each binds differently to the solid phase. The different behaviour of LEV and OFL in relation to solid-solution partitioning will affect their environmental fate. [ABSTRACT FROM AUTHOR]

The consumption of agricultural products grown on paddy soils contaminated with toxic element has a detrimental effect on human health. However, the processes and mechanisms of iron (Fe) mineral-associated arsenic (As) availability and As reactivity in different paddy soil profiles are not well understood. In this study, the fractions, immobilization, and release risk of As in eleven soil profiles from the Changzhutan urban agglomeration in China were investigated; these studied soils were markedly contaminated with As. Sequential extraction experiments were used to analyze fractions of As and Fe oxide minerals, and kinetic experiments were used to characterize the reactivity of Fe oxide minerals. The results showed that concentrations of total As and As fractions had a downward trend with depth, but the average proportions of As fractions only showed relatively small changes, which implied that the decrease in the total As concentrations influenced the changes in fraction concentrations along the sampling depth. Moreover, we found that easily reducible Fe (Feox1) mainly controlled the reductive dissolution of the Fe oxides, which suggest that the reductive dissolution process could potentially release As during the flooded period of rice production. In addition, a high proportion of As was specifically absorbed As (As-F2) (average 20.4%) in paddy soils, higher than that in other soils. The total organic carbon (TOC) content had a positive correlation with the amount of non-specifically bound As (As-F1) (R = 0.56), which means that TOC was one factor that affected the As extractability in the As-F1. Consequently, high inputs of organic fertilizers may elevate the release of As and accelerate the diffusion of As. [ABSTRACT FROM AUTHOR]

Purpose: Excessive fertilization has led to a high risk of phosphorus (P) leaching and related problems in the North China Plain, where the most typical cropland soil is fluvo-aquic soil. The main factors controlling environmental P behavior and the acting time sequence of these factors in soil after long-term P fertilizer application have not been well recognized. A clear understanding is essential for effective P management. Materials and methods: Effects of Fe minerals, calcium carbonate, and organic matter (OM) on P immobilization in fluvo-aquic soil were studied systematically through farmland investigation and aging experiments. Results and discussion: Phosphorus associated with Ca was the primary fraction in fluvo-aquic soil. Even though there was no significant correlation between the total contents of P and Ca in soils, formation of P-Ca phases facilitated by Ca2+ in soil solution was a mechanism of P retention when soil received excess P fertilizer. Positive correlations between the contents of P and Fe and total organic carbon (TOC) indicate that Fe minerals and OM have significant effects on P immobilization. Through the aging experiments, P was found to primarily adsorb on goethite and gradually forms Ca-P compounds. Organic fertilizer caused P release and inhibition of P adsorption in the initial stages; however, OM derived from organic fertilizer might facilitate P immobilization in the long term through the formation of a P-Ca-OM complex. Conclusions: Although superfluous application of P fertilizers leads to the gradual formation of Ca-P in fluvo-aquic soils, there is still a risk of P loss because P is not immediately adsorbed by Fe minerals. Moreover, application of organic fertilizers increases the risk of P loss. These results provide an important scientific basis for initiating P management policies for fluvo-aquic soils. [ABSTRACT FROM AUTHOR]

The microbial fuel cell (MFC) provides an inexhaustible electron acceptor to generate current and enhance the degradation of organic compounds. In MFCs with metolachlor as the sole carbon source, the degradation efficiency accelerated by 98%, with 61–76% of enhancement for the degradates, ethane sulfonic acid and oxanilic acid, respectively. According to quantifying primary metabolites of deschloro and metolachlor-2-hydroxyas, dechlorination and alcoholization were deemed as antecedent steps of metolachlor bioelectrochemical degradation. The energy recovery was infeasible by sole addition of metolachlor (at 13 ± 4 °C from equivalent weight of 0.224 mg). In MFCs with metolachlor and sodium acetate as the concomitant carbon sources, the electricity generation recovered to a level comparable to the controls, instead of increasing the removal efficiency of metolachlor. These results suggest that a low-efficiently direct electron transfer occurred between electricigens and metolachlor degraders. The Illumina sequencing showed that species of Paracoccus and Aquamicrobium played a potential degradation effect, while Comamonas sp. replaced Geobacter sp. as the predominant electricigen after addition of metolachlor. This study demonstrates that MFCs could be used as a promising alternative for treatment of chloroacetanilide herbicide contaminated wastewaters by means of a rapidly established active bacterial community. [ABSTRACT FROM AUTHOR]

Given its major transformations in recent decades, China has figured prominently in research on cultural change. Previous research converges in showing a general trend towards individualism in contemporary China while noting that rising individualism tends to coexist with enduring collectivism. To further understand this, we tested whether perceived traditional importance of cultural values would modulate the trajectory of cultural change reflected in word usage frequencies in published books. We re‐analysed Google's Chinese corpus since 1980 based on a broad sample of words associated with individualism–collectivism. We replicated the pattern of rising individualism and declining collectivism among words of modest and low perceived traditional importance. Most important, however, collectivistic words of high perceived traditional importance increased in usage frequencies with time, thus departing from the general trend towards individualism. Overall, our research underscores the role of core culture in cultural maintenance during times of rapid cultural change. [ABSTRACT FROM AUTHOR]

Studying the modes of selenium occurrence in high-Se soils and its behaviors can improve understanding and evaluating its cycling, flux, and balance in geo-ecosystems and its influence on health. In this paper, using a modified sequential chemical extraction technique, seven operationally defined selenium fractions and Se valence distribution were determined about five soils in which paddy was planted (W1, W2, W3, W4, W5) and five soils in which maize was planted (H1, H2, H3, H4, H5) around the selenium-rich core, Ziyang County, Shaanxi Province, China. The results show that selenium fractions in the soils mainly include sulfide/selenide and base-soluble Se, and ligand-exchangeable Se is also high for five soils in which paddy was planted. For water-soluble Se, Se (IV) is main Se valence and almost no Se (VI) was determined about five soils in which paddy was planted, while almost 1:1 of Se (IV) and Se (VI) coexist about five soils in which maize was planted. For exchangeable Se, similar results were found. For the first time, two typical high-Se soils (W1 soil and H1 soil) were chosen to measure the pH-dependent solid-solution distribution of selenite in the pH range 3-9, and the results were explained using LCD (ligand and charge distribution) adsorption modeling. The desorbed selenite concentrations from the two soils are in general underestimated by the model due to a comparable binding affinity of phosphate and selenite on goethite and much lower amount of total selenite than total reactively adsorbed phosphate. The pH dependency of adsorption of selenite added to the soil can be successfully described with the LCD model for W1 soil. Whereas considering the influence of Al-oxides, by lowering selenite adsorption affinity constant K of Se adsorption on goethite by 16 times, the LCD model can describe the adsorption much better. The results can help to understand selenium cycling, flux, and balance in typical high-Se soils. [ABSTRACT FROM AUTHOR]

Purpose: The electrode aging in soil microbial fuel cells (MFCs) disturbed the removal of pollutants and sensitivity of electrophysiological signal. Therefore, surveying the causes of aging electrodes could assist to take the prevention measures for remediation and biosensor application of soil MFCs.Materials and methods: The surface morphology, element accumulation on the surface of electrodes, and element migration in soils between electrodes were investigated by scanning electronic microscopy, energy-dispersive spectrometry, and X-ray photoelectron spectroscopy in a constructed soil MFC.Results and discussion: The rust was observed on the anode, and the soil gypsification was noted on the cathode after a long-term (300-day) contribution of soil MFCs. The major elements (At%) Na and Ca in soils on two electrodes increased by 338–562 and 100–119%, respectively. Beside, Al and Fe of increment (24 and 21%) in the anode and Mg and Fe of augmenter (84 and 155%) in the cathode were detected.Conclusions: The stacking of Ca and Fe besides Na in soils adjacent to electrodes probably led to the electrode corrosion and soil gypsification on the surface of electrodes. Thus, the electrode aging of soil MFCs should be paid more attention in further applications. [ABSTRACT FROM AUTHOR]

Efficient noninvasive techniques are desired for repairing organic-contaminated soils. Bioelectrochemical technology, especially microbial fuel cells (MFCs), has been widely used to promote a polluted environmental remediation approach, and applications include wastewater, sludge, sediment, and soil remediation. Soil MFC remediation has been of significant concern in recent years, and thus, several aspects, including reactor configuration, electrode materials, soil conductivity, mass transfer, and microbial activity, are reviewed. Recent studies and key issues of soil MFCs and perspectives of organic-contamination remedial application are summarized, with the aim of assisting environmental scholars and engineers to gain a comprehensive understanding of MFC remediation. Insights are also offered on how to extend applications to help soil MFC remediation technology to advance and be applied in the future on a large scale. [ABSTRACT FROM AUTHOR]

Recent research points to Chinese people's elevated tendency to make positive self-evaluations, despite the general claim that East Asians do not self-enhance. We present three studies in support of a novel prediction that sociocultural change in China plays an important role in augmenting self-enhancement. We operationalized self-enhancement primarily in terms of the better-than-average effect (BTAE) and accounted for trait desirability or importance. We found that: (i) compared with Chinese Canadians, Chinese showed a stronger BTAE; (ii) within the Chinese, identification with contemporary Chinese culture uniquely predicted a stronger BTAE; and (iii) priming contemporary (vs. traditional) Chinese culture led to a stronger BTAE. Finally, we provided further evidence that motivation, in part, underlies the rising Chinese BTAE. We conclude by discussing the importance of both socioeconomic and cultural perspectives for understanding how and when of self-enhancement in contemporary China and other societies undergoing social change. [ABSTRACT FROM AUTHOR]

Aims: The study aimed to find soil parameters that are best related to Se plant uptake for low Se soils with predominantly organic Se, and to explore the mechanisms that control Se bioavailability in the soils under study. Methods: A pot experiment using nineteen soil samples taken from different fields of arable land (potato fields) in the Netherlands was conducted on summer wheat ( Triticum aestivum L.). Selenium in wheat shoots and soil parameters, including basic soil properties, C:N ratio, inorganic selenite content, and Se and organic C in different soil extractions (0.01 M CaCl, 0.43 M HNO, hot water, ammonium oxalate, aqua regia) were analysed. Regression analysis was performed to identify soil parameters that determine Se content in wheat shoots. Results: The regression model shows that Se:DOC ratio in 0.01 M CaCl soil extraction explained about 88 % of the variability of Se uptake in wheat shoots. Selenium uptake increased with Se:DOC ratio in CaCl extraction, which can be interpreted as a measure of the content of soluble Se-rich organic molecules. Selenium:DOC ratio in CaCl extraction and Se uptake increased towards higher soil pH and lower soil C:N ratio. The soil C:N ratio is also negatively correlated to Se:organic C ratio in other extractions (0.43 M HNO, hot water, ammonium oxalate, aqua regia), indicating that at low soil C:N ratio soil organic matter is richer in Se. Contrarily, the soil pH is positively and strongly correlated to Se:organic C ratio in CaCl and hot water extractions, but only weakly correlated to Se:organic C ratio in other extractions. Conclusions: Selenium-rich dissolved organic matter is the source of bioavailable Se in low Se soils with predominantly organic Se. The soil pH and quality of soil organic matter (i.e. soil C:N ratio) are the main soil properties determining Se bioavailability in these soil types. [ABSTRACT FROM AUTHOR]

Batch experiments were conducted to investigate the adsorption of a widely used fluoroquinolone antibiotic levofloxacin (LEV) to goethite and effects of nitrate, sulfate, small organic acids, and humic acid (HA). The concentrations of LEV and small organic acids in single systems or mixtures were determined by a high-performance liquid chromatography. Presence of nitrate or sulfate almost had no influence on the adsorption of LEV to goethite. HA promoted the adsorption significantly, and similar results were also observed in column experiments. LEV adsorption to goethite increased slightly in the presence of small organic acids. The π-π interactions between LEV molecules and the aromatic ring of organic acids (or HA) might be the main mechanism. In column experiments, LEV adsorption to the goethite-coated sand was well fitted with the two-site nonequilibrium model using the CXTFIT 2.1 program within the software STANMOD. The desorption process was well predicted with the model using the same parameters. In the presence of HA, more LEV was adsorbed to goethite-coated sand, and the desorption process showed some delay. Some LEV adsorbed to goethite-coated sand could not be desorbed with NaCl but was desorbed with phosphate. Presence of HA (or natural organic matters, phosphate) had a great influence on the mobility and distribution of LEV in soils and waters, which might also affect its degradability and antibacterial activity. Results obtained in this study were seldom reported in previous studies, which help us to better understand the behavior of antibiotics in the natural environment. [ABSTRACT FROM AUTHOR]

In this study, the characteristics of cadmium (Cd) uptake by roots and translocation from roots to leaves of two eggplant species ( Solanum melongena and Solanum torvum) under relatively low Cd concentrations were investigated using stable Cd isotope through a number of hydroponic experiments. The uptake and translocation of Cd was compared with those of Zn and N. The results showed more Cd was loaded to the vascular channels and translocated upward to the leaves in S. melongena than in S. torvum, while the Cd concentrations were significantly lower in the roots of S. melongena than in S. torvum. When the phloem and xylem were wounded by grafting treatments, the foliar Cd concentrations were decreased by more than 66 % regardless of the rootstock species, whereas the uptake of Cd in the root was not inhibited by grafting. Similar grafting effects were observed for Zn. Hence, wounding phloem and xylem by grafting disturbed the upward transport of Cd and Zn to the eggplant leaves. Similarly, interruption of the phloem by the girdling treatment reduced the concentrations of Cd in the leaves of S. melongena by approximately 51 %, though the uptake of Cd by roots was not reduced by the interruption of phloem. In contrast, neither Zn concentrations nor stable N isotope ratio (δN) values in the roots and leaves of S. melongena were significantly influenced by the interruption of phloem. In conclusion, the phloem played a dominant role in the long-distance transport of Cd from the root to the leaf of S. melongena, whereas the xylem was the main channel for the translocation of Zn and N. [ABSTRACT FROM AUTHOR]

The article presents information on the SoilTrEC project, a global initiative on Critical Zone (CZ) research and integration for the preservation of soil ecosystems. Topics include the efforts of the European Union Thematic Strategy for Soil Protection to mitigate soil degradation; the European Commission-funded research project on Soil Transformations in European Catchments (SoilTrEC); soil conservation services; and integrated modeling of soil processes.

Aim: Our aim was to improve the prediction of Zn bioavailability to wheat grown on low-Zn soils. The classical approach that directly relates Zn in a certain soil extract to Zn uptake has been shown to be inadequate in many cases. We tested a stepwise approach where the steps of the uptake process are characterized with, respectively, Zn solid-solution distribution, adsorption of Zn to root surface, Zn uptake into root and Zn translocation to shoot. Methods: Two pot experiments were done with wheat grown on nine low-Zn soils varying widely in pH, clay and organic matter content. Soluble Zn concentrations in two soil extracts (DTPA and CaCl 2) were measured. Free Zn ion concentrations in CaCl 2 soil extracts were determined with the Donnan Membrane Technique. These Zn concentrations were then related to plant Zn uptake following both the direct and the stepwise approach. Results: In the direct approach, Zn in the DTPA extract was a better predictor for shoot Zn uptake than Zn in the CaCl 2 extract. In the stepwise approach, the relationship between Zn in CaCl 2 extracts and the root surface adsorbed Zn was pH-dependent and nonlinear. Root surface adsorbed Zn was linearly related to root Zn uptake, and the latter was linearly related to the shoot Zn uptake. The stepwise approach improved the Zn uptake prediction compared to the direct approach and was also validated for different wheat cultivars. Conclusions: The adsorption of Zn on the root surface is pH dependent and nonlinear with respect to the soil Zn concentration, and a useful proxy for bioavailable Zn over a wide range of soils. [ABSTRACT FROM AUTHOR]

Red lead (Pb3O4) has been extensively used in the past in anti-corrosion paints for the protection of steel constructions such as electricity pylons or bridges. Until recently, little has been known about the behavior of these Pb compounds in soils. Therefore, three pylon soils and six red lead anti-corrosion paints were characterized in terms of solubility, Pb mineral composition, extractability, sorption and desorption, and the chemical speciation of Pb in soil extracts. The pylon soils were characterized by moderate total Pb concentrations (≈700 mg kg−1), while NH4NO3extractable Pb was exceptionally high (up to 15% of total Pb). In soil extracts, the free Pb2+fraction ranged from 33 to 81% of total soluble Pb. The equilibrium concentration of Pb derived from Pb3O4in ultra-pure water reached 68.5 mg L−1. This high solubility explains the observed high extractability in soils and contradicts earlier reports of much lower water solubilities of the compound. [ABSTRACT FROM AUTHOR]

An accurate and fast method for simultaneous determination of small organic acids and much larger humic acids was developed using high performance size exclusion chromatography. Two small organic acids, i.e. salicylic acid and 2,3-dihydroxybenzoic acid, and one purified humic acid material were used in this study. Under the experimental conditions, the UV peaks of salicylic acid and 2,3-dihydroxybenzoic acid were well separated from the peaks of humic acid in the chromatogram. Concentrations of the two small organic acids could be accurately determined from their peak areas. The concentration of humic acid in the mixture could then be derived from mass balance calculations. The measured results agreed well with the nominal concentrations. The detection limits are 0.05 mg/L and 0.01 mg/L for salicylic acid and 2,3-dihydroxybenzoic acid, respectively. Applicability of the method to natural samples was tested using groundwater, glacier, and river water samples (both original and spiked with salicylic acid and 2,3-dihydroxybenzoic acid) with a total organic carbon concentration ranging from 2.1 to 179.5 mg C/L. The results obtained are promising, especially for groundwater samples and river water samples with a total organic carbon concentration below 9 mg C/L. [ABSTRACT FROM AUTHOR]

In natural systems heavy metals are present in very low concentrations (less than micro-molar), so precise measurement of the free metal ions is difficult. Recently, a new method has been developed called the Donnan membrane technique (DMT). Several heavy metals could be measured simultaneously using this method. Furthermore, all the metals did not interfere with each other, and the balance between the measured system and the surrounding condition could not be disturbed. Improvements were made according to the internal condition. The free heavy metal ion concentrations were measured in different systems using the improved method, and satisfied results have been obtained. [ABSTRACT FROM AUTHOR]

The effect of pH on the bioaccumulation of nickel (Ni) by plants is opposite when using a nutrient solution or a soil as a growing medium. This paradox can be understood if the pH effect on the bioaccumulation, on the chemical speciation in the soil solution, and on the binding to the soil of Ni are all taken into account. Using simple equations to describe the individual relationships, it is possible to quantify these effects once the relationships have been established. Increased Ni uptake leads to reduced plant dry weight production for a certain growing period. The median effective concentration (EC50) decreased from 23 to 1.7 µM Ni in the nutrient solution for pH 4.0 to 7.0, whereas the EC50 of added Ni in a sandy soil increased from 0.72 to 9.95 mmol Ni/kg soil for pH 4.7 to 6.8. Bioaccumulation, binding to the soil solid phase, and binding to the dissolved organic matter all increase with increasing pH. However, the magnitude of the effect is the least for bioaccumulation as a function of pH, causing the apparent paradox. [ABSTRACT FROM AUTHOR]

A correction to the article "Predicting zinc bioavailability to wheat improves by integrating pH dependent nonlinear root surface adsorption" that was published in a 2013 issue is presented.

Soil colloids significantly facilitate the transport of contaminants; however, little is known about the effects of highly reactive iron oxide and the most representative organic matter on the transport of soil colloids with different physicochemical properties. This study investigated the effects of goethite (GT) and humic acid (HA) on the sedimentation and transport of soil colloids using settling and column experiments. The stability of soil colloids was found to be related to their properties and decreased in the following order: black soil colloids (BSc) > yellow soil colloids (YSc) > fluvo-aquic soil colloids (FSc). Organic matter increased the stability of BSc, and ionic strength (Ca2+) promoted the deposition of FSc. Colloids in individual and GT colloids (GTc) coexistence systems tended to stabilize at high pH and showed a pH-dependence whereby the stability decreased with decreasing pH. The interaction of GTc and kaolinite led to a dramatic sedimentation of YSc at pH 4.0. HA enhanced the stability of soil colloids, especially at pH 4.0, and obscured the pH-dependent sedimentation of soil colloids. The transport ability of soil colloids was the same as their stability. The addition of GT retarded the transport of soil colloids, which was quite obvious at pH 7.0. This retardation effect was attributed to the transformation of the surface charge of sand from negative to positive, which increased the electrical double-layer attraction. Although sand coated with GT–HA provided more favorable conditions for the transport of soil colloids in comparison to pure sand, the corresponding transport was relatively slow. This suggests that the filtration effect, heterogeneity, and increased surface roughness may still influence the transport of soil colloids. [ABSTRACT FROM AUTHOR]