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Soil is an essential part of our ecosystem and plays a crucial role as a nutrient source, provides habitat for plants and other organisms. Overuse of antibiotics has accelerated the development and dissemination of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). ARB and ARGs are recognized as emerging environmental contaminants causing soil pollution and serious risks to public health. ARB and ARGs are discharged into soils through several pathways. Application of manure in agriculture is one of the primary sources of ARB and ARGs dissemination in the soil. Different sources of contamination by ARB and ARGs were reviewed and analyzed as well as dissemination mechanisms in the soil. The effects of ARB and ARGs on soil bacterial community were evaluated. Furthermore, the impact of different sources of manure on soil microbial diversity as well as the effect of antibiotics on the development of ARB and ARGs in soils was analyzed. Human health risk assessments associated with the spreading of ARB and ARGs in soils were investigated. Finally, recommendations and mitigation strategies were proposed. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is widely used in various fields and is considered to be relatively biocompatible. Herein, "indirect" nanotoxicity is first defined as toxic amplification of toxicants or pollutants by nanomaterials. This work revealed that GO greatly amplifies the phytotoxicity of arsenic (As), a widespread contaminant, in wheat, for example, causing a decrease in biomass and root numbers and increasing oxidative stress, which are thought to be regulated by its metabolisms. Compared with As or GO alone, GO combined with As inhibited the metabolism of carbohydrates, enhanced amino acid and secondary metabolism and disrupted fatty acid metabolism and the urea cycle. GO also triggered damage to cellular structures and electrolyte leakage and enhanced the uptake of GO and As. Co-transport of GO-loading As and transformation of As(V) to high-toxicity As(III) by GO were observed. The generation of dimethylarsinate, produced from the detoxification of inorganic As, was inhibited by GO in plants. GO also regulated phosphate transporter gene expression and arsenate reductase activity to influence the uptake and transformation of As, respectively. Moreover, the above effects of GO were concentration dependent. Given the widespread exposure to As in agriculture, the indirect nanotoxicity ofGOshould be carefully considered in food safety. [ABSTRACT FROM AUTHOR]

It is well known that graphene (G) induces nanotoxicity towards living organisms. Here, a novel and biocompatible hydrated graphene ribbon (HGR) unexpectedly promoted aged (two years) seed germination. HGR formed at the normal temperature and pressure (120 days hydration), presented 17.1% oxygen, 0.9% nitrogen groups, disorder-layer structure, with 0.38 nm thickness ribbon morphology. Interestingly, there were bulges around the edges of HGR. Compared to G and graphene oxide (GO), HGR increased seed germination by 15% root differentiation between 52 and 59% and enhanced resistance to oxidative stress. The metabonomics analysis discovered that HGR upregulated carbohydrate, amino acid, and fatty acids metabolism that determined secondary metabolism, nitrogen sequestration, cell membrane integrity, permeability, and oxidation resistance. Hexadecanoic acid as a biomarker promoted root differentiation and increased the germination rate. Our discovery is a novel HGR that promotes aged seed germination, illustrates metabolic specificity among graphene-based materials, and inspires innovative concepts in the regulation of seed development [ABSTRACT FROM AUTHOR]

Purpose: Two main pathways of phytoremediation of heavy metal-contaminated soils are phytostabilization and phytoextraction. Some soil amendments can strengthen phytostabilization or phytoextraction through either reducing heavy metal bioavailability in soil or increasing the heavy metal accumulation capacity of the hyperaccumulator (enhancing heavy metal concentration or shoot biomass of the hyperaccumulator). Urea and chicken manure are often used as fertilizers. This research will explore their effects on a newly found hyperaccumulator, Rorippa globosa (Turcz.) Thell., phytoremediating cadmium (Cd). Materials and methods: Pot culture experiment was conducted to study the accumulation characteristics of R. globosa at different Cd contamination concentrations under one fertilizer level (1 g kg for urea and 100 g kg for chicken manure), as well as the same Cd dose (20 mg kg) under different fertilizer doses. Cd was artificially spiked at 2.5, 5, 10, and 20 mg kg. Urea was amended at 0.5, 1, and 2 g kg, while chicken manure was supplemented at 50, 100, and 200 g kg. The heavy metal concentration in soil and plant samples was determined using an atomic absorption spectrophotometer. pH, N, P, K, and so on in soil samples were determined by normal method. Results and discussion: The results showed that urea application did not affect the Cd concentrations in root, stem, leaf, inflorescence, and shoot of R. globosa, but chicken manure significantly decreased ( p < 0.05) them by 28.4%, 29.3%, 30.8%, 24.9%, and 28.3%, respectively, owing to decreased extractable Cd in soil. Thus, strengthening the capacity (Cd accumulation in plant shoot, micrograms per pot) of urea was higher than that of chicken manure, though both shoot biomasses increased by one to threefold. Furthermore, the addition of urea and chicken manure increased the organic material, nitrogen, phosphorus and potassium, the microorganism count, urease, and the phosphatase activities of soil, indicating their eco-friendly function. Urea is ideal for optimizing phytoextraction of Cd using R. globosa, while chicken manure is appropriate for phytostabilization. Conclusions: Although chicken manure addition significantly increased ( p < 0.05) Cd extraction capacity (micrograms per pot) of R. globosa, extractable Cd concentration in soil was significantly decreased ( p < 0.05). In contrast, urea addition had no impact on soil extractable Cd and significantly increased Cd extraction capacity (micrograms per pot) of R. globosa by growth stimulation. Thus, this study demonstrates the effect of fertilizer amendment in enhancing phytoextraction using a Cd hyperaccumulator, R. globosa, only by increased plant biomasses. Furthermore, chicken manure can strengthen phytostabilization because it decreased extractable Cd in soil. [ABSTRACT FROM AUTHOR]

Purpose: Chlorimuron-ethyl is a sulfonylurea herbicide widely used to control many annual broadleaf weeds, and the residue for a long period posed a heavy hazard to rotational crops or vegetables. Knowledge about effect of soil pH and organic matter on desorption processes of chlorimuron-ethyl remains obscure. In this study, desorption behavior of chlorimuron-ethyl as a function of soil pH and organic matter was investigated. Materials and methods: Two typical soils in northeastern China, brown earth (luvisols) and black soil (phaeozem), were used in this study. Soils were treated with peroxide to remove organic matter. Desorption kinetics of chlorimuron-ethyl in the original and HO-treated soils were simulated. The adsorption and desorption experiments were conducted at three different pH values with the original soils using batch equilibration methods. For the soils after having removed organic matter, the lower concentrations of adsorption were not used for desorption study because the concentrations expected were lower than the limit of detection of the method. Results and discussion: The pseudo-second-order equation could well describe the desorption kinetics and the desorption velocity increased significantly from the soils after the removal of organic matter. The desorption data were well fitted with the Freundlich isotherm with high regression coefficients ( R > 0.97). Besides, the apparent hysteresis was observed for the desorption of chlorimuron-ethyl from the two soils, and the desorption from black soil was weaker than that from brown earth due to the higher content of organic matter and clay, and lower proportion of sand. The desorption of chlorimuron-ethyl from both soils became more difficult with an increase in the initial concentrations as a result of the gradient effect of concentrations. The degree of hysteresis increased as soil pH increased due to the strengthened binding energy of adsorption interactions. Conclusions: The desorption of chlorimuron-ethyl from brown earth and black soil was significantly hysteretic, and the degree of hysteresis was greater for black soil than for brown earth. The increase of soil pH would enhance the retention of chlorimuron-ethyl and thus effectively retard chlorimuron-ethyl from entering the aqueous phase. The method of removing organic matter by HO treatment was not fit for researching effect of organic matter on the desorption of chlorimuron-ethyl from original soils. [ABSTRACT FROM AUTHOR]

Pot culture experiments were conducted to study the remediation potentials of a newly found accumulator Kalimeris integrifolia Turcz. ex DC. under different cadmium (Cd) concentrations with same fertilizer level, as well as the same Cd dose under different fertilizer doses. At medium (100 g/kg) chicken manure level, Cd concentrations in roots, stems, leaves, inflorescences, and shoots of K. integrifolia grown in the soils contaminated with 2.5, 5, 10, and 25 mg/kg Cd significantly decreased ( p < 0.05) in average by 23.8%, 29.9%, 24.0%, 30.1%, and 38.6%, respectively, when compared to those of the pots without addition of chicken manure. In contrast, the medium urea amendment level (1 g/kg) showed no effect on the bioaccumulated Cd concentrations of K. integrifolia regardless of the spiked Cd doses. However, Cd extraction capacities (micrograms per pot) of K. integrifolia shoots were significantly increased ( p < 0.05) due to the gain in biomass (more than one- to twofolds) by the soil fertilizing effect of urea and chicken manure. Particularly, Cd extraction capacities (micrograms per pot) of K. integrifolia shoots amended by urea were higher than that of chicken manure. Under the condition of 25 mg/kg Cd addition, shoot biomasses of K. integrifolia were significantly increased ( p < 0.05) with the amendment of chicken manure (50, 100, and 200 g/kg) and urea (0.5, 1, and 2 g/kg). As a result, the Cd extraction capacities (micrograms per pot) were increased in treatments even though soil extractable Cd concentrations were significantly decreased ( p < 0.05) by amendment with chicken manure and maintained by urea addition. For practical application concerns, chicken manure is better used as phytostabilization amendment owing to its reducing role to extractable heavy metal in soil, and urea is better for phytoextraction. [ABSTRACT FROM AUTHOR]

Introduction: More attention has been paid to tetracycline contamination in view of its rapid increasing concentration in the environment. Therefore, it is important to set up rapid, simple, and accurate methods for monitoring tetracycline ecotoxicity. Methods: In the present study, a hydroponics experiment was conducted to examine toxic effects of tetracycline at the concentration range of 0.5 to 300 mg L on growth, antioxidative, and genetic indices of wheat ( Triticum aestivum L.). Results: The results indicated that tetracycline at 0.5-10 mg L could stimulate seed germination, cell mitotic division, and growth of wheat seedlings and did not induce a significant increase in the activity of antioxidative enzymes. However, tetracycline at the high concentrations (10-300 mg L) could significantly inhibit these parameters in the concentration-dependent manner, including germination percentage (≥100 mg L), shoot height (≥100 mg L), root length (≥50 mg L), and mitotic index (≥50 mg L), and increased the activity of antioxidative enzymes (≥25 mg L) in the dose-dependent manner, including superoxide dismutase, catalase, and peroxidase. Tetracycline at 5 mg L and above significantly augmented chromosome aberration frequency and malondialdehyde (MDA) content. On the other hand, MDA has positive correlation with the inhibition rates of seed germination, root length, shoot length, mitotic index, and antioxidative enzyme activities. Conclusion: Tetracycline may have potential physiological, biochemical, and genetic toxicity to plant cells, and chromosome aberration and MDA might be sensitive bioindicators for tetracycline contamination than the other plant characteristics. [ABSTRACT FROM AUTHOR]

Purpose: Organic dyes have been turned into an important emerging type of chemical pollutants with the development of rural textiles, synthetic dye, printing, and dyeing industries and the continuous release from washing fabrics and clothes in recent decades. In order to assess ecological risk of reactive X-3B red dye as a typical dye, the adsorptive and desorptive traits of the dye in soils were investigated and the environmental factors influencing those processes were examined and discussed. Materials and methods: Adsorptive and desorptive isotherms and dynamics of reactive X-3B red dye as a typical emerging pollutant were investigated by the standard batch experiments using four typical soils in China including relatively clean brown earth (burozem), drab soil (cinnamon soil), paddy soil (aquorizem), and red soil (krasnozem) and calculated by mathematical models using the Microsoft Excel software. Results and discussion: It was suggested that the adsorptive behavior of reactive X-3B red dye by the four soils can basically be described using the Langmuir equation, and their maximum adsorbing capacity was in the sequence paddy soil > red soil > brown earth > drab soil. The adsorption could be divided into four stages including high-speed adsorption, slowdown adsorption, tardiness adsorption, and zero-approaching adsorption. It was also indicated that the adsorption ability of the dye decreased with the reduction in soil organic matter or air temperature and under neutral, runny, or unwatered conditions. The increase of desorption was observed with the decrease of soil organic matter and the increase of air temperature or soil moisture, while desorption was inhibited by the acidification or basification of soils. The comparative study validated that the basic adsorption–desorption laws of the dye at high concentrations were basically consistent with those at low concentrations. Conclusions: It could be concluded that reactive X-3B red dye has the potential properties of persistent organic pollutants with high ecological risk, and its release from contaminated soils and uptake by crops can be disturbed and changed by human activities. [ABSTRACT FROM AUTHOR]

In order to solve environmental problems resulting from ammonia released into the atmosphere, the emission of ammonia contamination from monosodium glutamate (MSG) production was quantitatively observed, and the relationships with relevant influencing factors (ammonium-N, nitrate/nitrite-N and pH) were statistically analyzed. The results indicated that the release of gaseous ammonia from MSG production including the treatment and discharge of wastewater was highly dependent on the technical processes utilised. The flux of ammonia released from the fermentation workshop was highest, up to 8.98 × 10 mg m min, and the flux from the sugar-refining workshop was lowest, only 85.1 mg m min. The release of gaseous ammonia during the whole MSG production was significantly proportional to the concentration of ammonium-N in the discharged solution, and exponentially proportional to the concentrations of nitrate–nitrogen and nitrite-nitrogen in the discharged solution. Although there was no linear relationship between the flux of ammonia released during the whole MSG production and pH values in the discharged solution, pH was significantly related to the flux of ammonia released during the treatment and discharge of wastewater. [ABSTRACT FROM AUTHOR]

Abstract  This objective of this study is to conduct a systematic investigation of the effects of configurations, electrolyte solutions, and electrode materials on the performance of microbial fuel cells (MFC). A comparison of voltage generation, power density, and acclimation period of electrogenic bacteria was performed for a variety of MFCs. In terms of MFC configuration, membrane-less two-chamber MFCs (ML-2CMFC) had lower internal resistance, shorter acclimation period, and higher voltage generation than the conventional two-chamber MFCs (2CMFC). In terms of anode solutions (as electron donors), the two-chamber MFCs fed with anaerobic treated wastewater (AF-2CMFCs) had the power density 19 times as the two-chamber MFCs fed with acetate (NO3 −2CMFCs). In terms of cathode solutions (as electron acceptors), AF-2CMFCs with ferricyanide had higher voltage generation than that of ML-2CMFCs with nitrate (NO3 −ML-2CMFCs). In terms of electrode materials, ML-2CMFCs with granular-activated carbon as the electrode (GAC-ML-2CMFCs) had a power density 2.5 times as ML-2CMFCs with carbon cloth as the electrode. GAC-ML-2CMFCs had the highest columbic efficiency and power output among all the MFCs tested, indicating that the high surface area of GAC facilitate the biofilm formation, accelerate the degradation of organic substrates, and improve power generation. [ABSTRACT FROM AUTHOR]

Organic contaminants and toxic heavy metals often coexist in contaminated soils. However, little information concerning the interactive effects of organic contaminants and heavy metals on their sorption behaviors on soils is available. In this study, the competitive sorption effects of 1,4-dichlorobenzene (1,4-DCB) and typical heavy metals, cadmium (Cd) and copper (Cu), on their sorption characteristics on two Chinese soils were examined using a batch equilibration method. The results indicated that the coexistence of Cd and Cu inhibited the sorption of 1,4-DCB on soils and the inhibitive effects increased with increasing concentrations of Cd and Cu. This can be attributed to the inner-sphere complexation of Cd and Cu to form hydration shells of dense water that directly compete for surface sorption sites with 1,4-DCB. Additionally, pore blockage is presumed to be an alternative mechanism for the inhibitive effect. The extent of inhibitive effects depends on not only the relatively chemical characteristics of metals but also on the types of soils. However, the concurrence of 1,4-DCB (50 mg/L) in soils has little effects on the sorption capacity of Cd and Cu due to their higher sorption affinity for the soils than 1,4-DCB. These findings indicated that the coexistence of metals can greatly affect sorption behaviors of hydrophobic organic compounds on soils and thus their fate, transportation, and bioavailability. [ABSTRACT FROM AUTHOR]

This paper demonstrates the Pb2+ adsorption capacity and adsorption rate of Saccharomyces cerevisiae by both static and dynamic testing to verify its feasibility as a heavy metal bio-absorbent in wastewater treatment. The static testing was divided into two parts. First, we tested S. cerevisiae by itself, and then we tested immobilized S. cerevisiae. In static testing of the non-immobilized S. cerevisiae, the Pb2+ adsorption capacity and adsorption rate increased up to 6.52 mg/g and 52.94%, respectively, with time. After immobilization, the Pb2+ adsorption capacity and adsorption rate reached 10 mg/g and 80%, respectively. In dynamic testing, the optimal saturated adsorption capacity of immobilized S. cerevisiae for Pb2+ was 6.64 mg/g. In addition to the static and dynamic testing of adsorption capacity and rate, we used SEM imaging to analyze the mechanics of adsorption, and the images showed that the cell wall played the major roll in Pb2+ adsorption. [ABSTRACT FROM AUTHOR]

In the process of bioremediation in the soil contaminated by different oil concentrations, the changes in the microbial numbers (bacteria and fungi) and the enzyme (catalase (CAT), polyphenol oxidase (PPO) and lipase) activities were evaluated over a 2-year period. The results showed that the microbial numbers after 2-year bioremediation were one to ten times higher than those in the initial. The changes in the bacterial and the fungal populations were different during the bioremediation, and the highest microbial numbers for bacteria and fungi were 5.51 × 109 CFU g−1 dry soil in treatment 3 (10,000 mg kg−1) in the initial and 5.54 × 105 CFU g−1 dry soil in treatment 5 (50,000 mg kg−1) after the 2-year bioremediation period, respectively. The CAT and PPO activities in the contaminated soil decreased with increasing oil concentration, while the lipase activity increased. The activities of CAT and PPO improved after the bioremediation, but lipase activity was on the contrary. The CAT activity was more sensible to the oil than others, and could be alternative to monitor the bioremediation process. [ABSTRACT FROM AUTHOR]

In a microcosm experiment, the amplified ribosomal DNA restriction analysis was adopted to investigate the Pseudomonas community structure in soils applied with different concentrations (0, 50, 150, and 250 mg/kg) of acetochlor, and an in vitro assay was made to examine the antagonistic activity of isolated Pseudomonas strains acting on soil-borne pathogen Rhizoctonia solani. The results showed that acetochlor application changed the community structure of Pseudomonas in aquic brown soil. The diversity of Pseudomonas and the amount of isolated Pseudomonas strains with antagonistic activity decreased with an increasing acetochlor concentration, and the toxic effect of acetochlor reached to a steady level at 150–250 mg/kg. [ABSTRACT FROM AUTHOR]

The screening of hyperaccumulators is still very much needed for phytoremediation. With properties such as strong tolerance to adverse environment, fast growing and highly reproductive rate, weed species may be an ideal plant for phytoremediation. The objectives of this study were to examine the tolerance and hyperaccumulative characteristics of 24 species in 9 families to Cd, Pb, Cu and Zn by using the outdoor pot-culture experiment. In the screening experiment, only Conyza canadensis and Rorippa globosa displayed Cd-hyperaccumulative characteristics. In a further concentration gradient experiment, C. canadensis was affirmed that it is not a Cd hyperaccumulator. Only R. globosa, indicated all Cd hyperaccumulative characteristics, especially Cd concentration in its stems and leaves were higher than 100 mg/kg, the minimum Cd concentration what a Cd-hyperaccumulator should accumulate. Thus, R. globosa was further validated as a Cd-hyperaccumulator. [ABSTRACT FROM AUTHOR]

Application of synthetic chelates such as ethylene diamine tetraacetic acid (EDTA) has been proposed as an alternative technology for phytoextraction of contaminated soils. In a pot experiment, the effects of EDTA application at three growing stages on growth and Cd uptake and accumulation of Solanum nigrum L. were investigated. The results showed that the 0.1 g/kg EDTA treatment was the most effective treatment, in which the concentrations of Cd in stems and leaves increased significantly compared with the control (Cd only), and the accumulation of Cd in shoots increased by 51.6%, 61.1% and 35.9% at the seedling, flowering and mature stages, respectively. Moreover, at the flowering stage, the height, dry shoot biomass and Cd accumulation in the plants reached the maximum, which were 18.9 cm, 1.8 g/plant and 292.8 μg/pot, respectively. However, higher rate of EDTA (0.5 g/kg) could reduce the plant biomass and the total amount of Cd removed. The results indicated that moderate rate of EDTA applied at the flowering stage would be important to enhance phytoremediation efficiency in practice. [ABSTRACT FROM AUTHOR]

Soil pollution by cadmium has been a long standing ecological problem in Zhangshi Irrigation Area, Shenyang, China, as a result of the 30-year practice of irrigation with wastewater containing high levels of heavy metals. To evaluate the adverse impact of cadmium contamination on soil ecosystems, the responses of soil microbiota to both long-term and short-term cadmium stress were studied by molecular microbial community profiling with denaturating gradient gel electrophoresis (DGGE) analysis. Our results show that soil characteristics and nutrient conditions were likely more important than cadmium toxicity in shaping the soil bacterial community structure in the long term. In comparison, soil microbial genetic diversity was shown to be more closely correlated to cadmium levels under short-term cadmium stress, with the highest microbial genetic diversity occurring at mild cadmium stress conditions, which might be attributed to the enrichment of metal-resistant microbial populations through mechanisms of competitive selection and genetic adaptation. In contrast, severe cadmium stress likely presented a condition that fewer microbial populations could survive, thus leading to reduced microbial genetic diversity. [ABSTRACT FROM AUTHOR]

The remediation of diesel fuel contaminated soil over a 2-year period by the plant–microorganism synergy was evaluated. Results indicated that the growth of Astragalus adsurgens was affected significantly, when the diesel fuel concentration was higher than 10 g kg−1 dry soil. After a 2-year period, the removal of diesel fuel was >67%, and about 58–70% removal of aromatic hydrocarbons was obtained in these treatments. The removal of diesel fuel and its components was 13–30% higher than that of plant alone. These results show that an appropriate plant–microorganism synergy may serve as a low-cost, effective remedial technology for diesel-contaminated soil. [ABSTRACT FROM AUTHOR]

Phytoremediation, which mainly employs hyperaccumulators to remove heavy metals from contaminated soils, is receiving more attention world-wide. The identification of hyperaccumulators is still a key step for phytoremediation. This research is devoted to identify some plants with hyperaccumulative characteristics from weed species. In a pot culture experiment, the hyperaccumulative characteristics of 13 weed species in 11 families to Cd, Pb, Cu and Zn were examined. The result showed that Taraxacum mongolicum and Rorippa globosa indicated some Cd hyperaccumulative properties. In a sample-analysis experiment conducted in a Pb−Zn mining area, T. mongolicum and R. globosa also displayed the same hyperaccumulative characteristics. However, in a concentration gradient experiment, Cd content in shoot of T. mongolicum was not higher than 100 mg/kg (DW, dry weight), the minimum Cd concentration for a Cd-hyperaccumulator in any treatment. The concentration of Cd in the stems and leaves of R. globosa were greater than 100 mg/kg, under the conditions of the soils spiked with 25 and 50 mg/kg Cd. The Cd accumulation factors and translocation factors in the shoots of R. globosa were higher than 1 too, and the plant biomasses did not decrease significantly ( p < 0.05) compared with the control. Thus, we conclude that only R. globosa showed the whole Cd-hyperaccumulator properties, which is a Cd-hyperaccumulator. [ABSTRACT FROM AUTHOR]

This article discusses cadmium and lead speciation in the soil of northeast China as affected by the level of metal loading, aging time and the interaction between the two metals. The concentrations of these heavy metals were analyzed using an atomic absorption spectrophotometer. Sequential extraction was developed for fractions defined as SE (water soluble plus exchangeable); WSA (bound to carbonate or weakly specifically adsorbed); OX (bound to Fe or Mn oxides); OM (bound to organic matter) and RES (residual). According to the authors, good linear relationships were obtained between the soluble exchangeable fraction content of metals in soil and the ionic impulsion. Apparently, for longer aging times there is a movement of cadmium and lead to the weakly specifically absorbed and residual fractions.

The use of low-cost and environmental safety amendments for the in situ immobilization of heavy metals has been investigated as a promising method for contaminated soil remediation. Natural materials and waste products from certain industries with high captive capacity of heavy metals can be obtained and employed. Reduction of extractable metal concentration and phytotoxicity could be evaluated and demonstrated by the feasibility of various amendments in fixing remediation. In this review, an extensive list of references has been compiled to provide a summary of information on a wide range of potentially amendment resources, including organic, inorganic and combined organic-inorganic materials. The assessment based on the economic efficiency and environmental risks brought forth the potential application values and future development directions of this method on solving the soil contamination. [ABSTRACT FROM AUTHOR]

A systematic investigation was conducted to screen for cadmium-hyperaccumulator from 54 species in 20 weed families using outdoor pot-culture experiment and small-scale field experiment. The results from the outdoor pot-culture experiment showed that Cd concentrations in the stems and leaves of Solanum nigrum L. growing in a soil spiked with 25 mg/kg Cd were up to 103.8 and 124.6 mg/kg (DW), respectively, which was greater than 100 mg/kg, minimum Cd concentration for a Cd-hyperaccumulator. The Cd enrichment factor (EF, concentration ratio in plant to soil) in shoots was as high as 2.68. Moreover, Cd accumulation in shoots was greater than that in roots (TF, concentration ratio in shoots to roots) and the plant biomass growth was not inhibited at the Cd concentrations tested compared with the control. The results of the small-scale field experiment also showed that the characteristics of Cd accumulation in S. nigrum were all consistent with the characteristics of Cd-hyperaccumulators. Thus S. nigrum can be classified as a Cd-hyperaccumulator. This work is important for further research in the areas of hyperaccumulators screening, and plant-tolerance physiology and evolution. It provides a patentable new plant species for phytoremediation of Cd-contaminated soils. [ABSTRACT FROM AUTHOR]

Potential release of soil colloids into groundwater has attracted considerable attention because of their association with heavy metals. Much effort has been focused on using colloid-deposition-based parameters (batch experiment) to predict colloid release in soils (column experiment), though they are two separate processes. In this paper, relative colloid stability ratio was estimated and used to relate to colloid release in soils. Changes in colloid release with incubation times were measured in two lead-contaminated soils. Colloid stability ratio (W) is defined as the ratio of the colloid flocculation rate of a suspension under normal observation conditions (slow flocculation) to the rate under rapid flocculation conditions. Assuming that colloid flocculation rate is related to changes in light absorbency of a solution, relative colloid stability ratio (RW) was estimated by dividing the rate of absorbency change of soil suspension observed in 0.06 M NaCl (slow flocculation) by that in 0.01 M CaCl2 (rapid flocculation) electrolyte solutions. Both colloid release and R W changed randomly with incubation times in both soils. However, colloid release generally increased as RW increased with correlation coefficients of 0.67-0.89. This result suggests that the overall colloid release from these soils was related to RW, even though they are different conceptually. However, research is needed to further develop the concept of using relative colloid stability ratio to predict colloid release in soils. [ABSTRACT FROM AUTHOR]

The responses of wheat Triticum aestivum, rice Oryza sativa, earthworms Eisenia foetida, and prawns Penaeus japonicus to combined acetochlor-Cu, Cd-Zn were studied in hydroponic and soil-culturing systems using the methods of ecotoxicology. In particular, systematically quantitative analyses were documented by field experiments. Results showed that ecotoxicological effects under the combined pollution were not only related to chemical properties of pollutants but also dependent on the concentration level of pollutants, in particular on the combination of concentrations of pollutants in ecosystems. Additionally, species of organisms, especially the type of ecosystem, determined the influences. To some extent, biological tissue targets attacked by pollutants were an important factor. [ABSTRACT FROM AUTHOR]

Previous field investigations and a pot-culture experiment treated with 0, 5, 10, and 20 mg kg-1 of reactive X-3B red dye (RRD), combined with chemical and statistical analyses, indicated that the amount of iron accumulated in seeds of soybean (Glycine max) and rice (Oryza sativa) and edible parts of watermelon (Citrullus Vulgaris Schrad) decreased with the increase in the amount of RRD added to various soils including burozem, aquorizem and krasnozem. There were significant negative relationships between the uptake of iron by the crops and the concentration of RRD added to the soils. Thus, chemical pollution of some organic dyes in agricultural soils may result in the deficiency of iron in crops. According to the extraction with 1.0 M NH4OAc solution and the determination of enzyme activity, the adverse effect inhibiting the uptake of iron in crops was chemical chelation and immobilization of iron with RRD. The activity of iron reductase was also greatly affected. [ABSTRACT FROM AUTHOR]