[Show abstract][Hide abstract] ABSTRACT: A plant growth-promoting bacterial (PGPB) strain SC2b was isolated from the rhizosphere of Sedum plumbizincicola grown in lead (Pb)/zinc (Zn) mine soils and characterized as Bacillus sp. based on (1) morphological and biochemical characteristics and (2) partial 16S ribosomal DNA sequencing analysis. Strain SC2b exhibited high levels of resistance to cadmium (Cd) (300 mg/L), Zn (730 mg/L), and Pb (1400 mg/L). This strain also showed various plant growth-promoting (PGP) features such as utilization of 1-aminocyclopropane-1-carboxylate, solubilization of phosphate, and production of indole-3-acetic acid and siderophore. The strain mobilized high concentration of heavy metals from soils and exhibited different biosorption capacity toward the tested metal ions. Strain SC2b was further assessed for PGP activity by phytagar assay with a model plant Brassica napus. Inoculation of SC2b increased the biomass and vigor index of B. napus. Considering such potential, a pot experiment was conducted to assess the effects of inoculating the metal-resistant PGPB SC2b on growth and uptake of Cd, Zn and Pb by S. plumbizincicola in metal-contaminated agricultural soils. Inoculation with SC2b elevated the shoot and root biomass and leaf chlorophyll content of S. plumbizincicola. Similarly, plants inoculated with SC2b demonstrated markedly higher Cd and Zn accumulation in the root and shoot system, indicating that SC2b enhanced Cd and Zn uptake by S. plumbizincicola through metal mobilization or plant-microbial mediated changes in chemical or biological soil properties. Data demonstrated that the PGPB Bacillus sp. SC2b might serve as a future biofertilizer and an effective metal mobilizing bioinoculant for rhizoremediation of metal polluted soils.
Journal of Toxicology and Environmental Health Part A 07/2015; 78(13-14):931–944. DOI:10.1080/15287394.2015.1051205 · 2.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sedum plumbizincicola X.H. Guo et S.B. Zhou ex L.H. Wu (Crassulaceae), a new species restricted to lead–zinc mining areas in Zhejiang Province, China, is described and illustrated. This taxon belongs to sect. Sedum (H. Ohba) S.H. Fu based on the adaxially gibbous carpels and follicles. It superficially resembles S. alfredii Hance and three other Sedum species found in the same area, but differs from these other taxa in bearing 4-merous flowers. Differences in geographical distribution, growth habit, phenology, macromorphology, leaf and stem anatomy, as well as seed micromorphology among S. plumbizincicola, S. alfredii and other related taxa in the genus Sedum are also reported. nrDNA internal transcribed spacers (ITS) sequences from seven populations of S. plumbizincicola support the recognition of this as a taxonomic entity distinct from S. alfredii.
[Show abstract][Hide abstract] ABSTRACT: We investigated the occurrence of 14 selected antibiotics including five therapeutic classes of tetracyclines, sulfonamides, macrolides, fluoroquinolones and chloramphenicols in manures collected from four swine farms of different sizes in eastern China. Tetracyclines (tetracycline, oxytetracycline, chlortetracycline, and doxycycline) and sulfadiazine were the most prominent contaminants in the manure samples, with maximum concentrations reaching 98.2 x 10(3), 354.0 x 10(3), 139.4 x 10(3), 37.2x 10(3), and 7.1x 10(3) mu g/kg, respectively. The occurrence of these compounds was dependent on breeding scale, animal type, and breeding season. Manure storage and vermiculture were not able to effectively deplete the heavier contaminants (tetracyclines and sulfadiazine), resulting in high levels of these chemicals remaining in manures. Therefore, the occurrence of these antibiotics in agricultural soils (0.1-205.1 mu g/kg) collected from four types of agricultural land (pear orchard, tea plantation, bamboo forest, and paddy field) near the studied farms, was a reflection of manure application. However, the extremely high concentrations of antibiotics in manures were unlikely from feed consumption, but from other direct forms of medicine application.
Chinese Science Bulletin 02/2012; 57(6-6):606-614. DOI:10.1007/s11434-011-4830-3 · 1.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A Cd and Zn contaminated soil was mixed and equilibrated with an uncontaminated, but otherwise similar soil to establish a gradient in soil contamination levels. Growth of Thlaspi caerulescens (Ganges ecotype) significantly decreased the metal concentrations in soil solution. Plant uptake of Cd and Zn exceeded the decrease of the soluble metal concentrations by several orders of magnitude. Hence, desorption of metals must have occurred to maintain the soil solution concentrations. A coupled regression model was developed to describe the transfer of metals from soil to solution and plant shoots. This model was applied to estimate the phytoextraction duration required to decrease the soil Cd concentration from 10 to 0.5 mg kg(-1). A biomass production of 1 and 5 t dm ha(-1) yr(-1) yields a duration of 42 and 11 yr, respectively. Successful phytoextraction operations based on T. caerulescens require an increased biomass production.
[Show abstract][Hide abstract] ABSTRACT: Soil organic matter can be divided into different organic carbon (C) pools with different turnover rates. The organic pollutants in soils associated with these organic C pools may have different bioavailability and environmental risks during the decomposition of soil organic matter. We studied the distribution patterns of 15 USEPA priority polycyclic aromatic hydrocarbons (PAHs) in different particle-size separates (clay, fine silt, coarse silt, fine sand and coarse sand) and density fractions (light and heavy fractions) of nine agricultural topsoils (0–20 cm depth) from a contaminated area in the Yangtze River Delta region of east China. There was a decreasing trend in PAH concentration in particle-size separates with decreasing particle size. However, the different particle-size separates had similar PAH composition. The concentration of PAHs in the light fraction ranged from 13 037 to 107 299 μg kg−1, far higher than in the heavy fraction, which ranged from 222 to 298 μg kg−1. Although the light fraction accounted for only 0.4–2.3% of the soils, it was associated with 31.5–69.5% of soil PAHs. The organic matter in coarse silt had the strongest capacity for enrichment with PAHs. Combining the distributions of PAHs and the turnover rates of organic matter in different soil fractions, the environmental risks of PAH-polluted soils may be due mainly to the PAHs associated with sand and the light fraction.
European Journal of Soil Science 11/2008; 59(6):1020 - 1026. DOI:10.1111/j.1365-2389.2008.01066.x · 2.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Chemical fractions of copper (Cu) and zinc (Zn) in the organic-rich particles collected from filtered aqueous extracts (< 20 mu m) of an acid soil were determined. A sequential extraction procedure was used to partition the particulate Cu and Zn into four operationally defined chemical fractions: adsorbed (ADS), iron (Fe) and manganese (Mn) oxides bound (FeMnOX), organic matter bound (OM) and residual (RESD). Total extractable concentrations of Cu and Zn in the fine particles were higher than their total concentrations in the original bulk soil. The concentration of particulate Cu was usually much higher than that of particulate Zn. Addition of lime stabilized sewage sludge cake and/or inorganic metal salts markedly increased the concentrations of particulate Cu and Zn in aqueous extracts, especially from limed soil. The proportional distributions of particulate Cu and Zn were quite similar. The two particulate metals were present predominantly in the ADS and FeMnOX fractions, with less (about 20%) in the OM and RESD fractions. Some of the ADS metal fraction was associated with dissolved organic substances. The concentrations of particulate Cu and Zn in the various extractable fractions were significantly affected by the application of lime, lime stabilized sewage sludge cake, or inorganic metal salts.
Communications in Soil Science and Plant Analysis 11/2008; 27(18-20):2973-2986. DOI:10.1080/00103629609369755 · 0.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two pot experiments were conducted to investigate the time course effects of the (S, S)-N, N'-ethylenediamine disuccinic acid (EDDS) addition to contaminated soil on the uptake of Cu and Zn by the Cu accumulator Elsholtzia splendens and on plant Cu and Zn concentrations at different growth stages. EDDS increased the amounts of Cu and Zn soluble in the soil, taken up by plants, concentrated in the xylem sap, and translocated from roots to stems and leaves. The increase in soil-soluble metals, especially Cu, resulted in a corresponding increase in metal concentrations in the xylem sap and leaves. The addition of EDDS to the soil increased plant Cu and Zn concentrations, especially in the leaves, and changed the proportions of Cu and Zn taken up by different plant parts. The proportions of Cu and Zn taken up by the roots were higher than by the leaves of control plants, but EDDS-treated plants showed the opposite trend. EDDS exerted greater effects at the end of the vegetative growth stage than at the start of the flowering or reproductive stages.
International Journal of Phytoremediation 06/2007; 9(3):227-41. DOI:10.1080/15226510701376091 · 1.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Polycyclic aromatic hydrocarbons (PAHs) were quantified in 30 soil profiles from the Yangtze River Delta Region, in east China. Relative concentrations of PAH compounds with different benzene rings and ratios of fluoranthene to fluoranthene plus pyrene and benz(a)anthracene to benz(a)anthracene plus chrysene were used to identify the possible sources of soil PAHs. Total concentrations of 15 PAHs in topsoils ranged from 8.6 to 3881 microg kg(-1) with an average of 397 microg kg(-1). Half of the soil samples were considered to be contaminated with PAHs (>200 microg kg(-1)) and two sampling sites were heavily polluted by PAHs with concentrations >1000 microg kg(-1). Phenanthrene was found in soils below a depth of 100 cm in half of the sampling sites, but the detectable ratio of benzo(a)pyrene decreased sharply from 100% in topsoil to 0 in the 4th horizon.
[Show abstract][Hide abstract] ABSTRACT: Information on carbon (C) storages and the changes under the shifting of land use is of particular interest for estimating the gains and losses of soil C at a regional scale. The present study attempted to quantify the soil organic carbon (SOC) storage in the Hong Kong soils for the first time as well as to demonstrate the changes of SOC density after the transformations of paddy fields to other land usages due to the decline of agricultural activities. SOC storages were estimated by combining the land-use areas and profile data derived from our recent soil survey (248 samples were collected) and other reports. The results indicated that SOC densities to the upper 100 cm ranged from 25.06 Mg ha− 1 of urban park land to 288.65 Mg ha− 1 of swamp and mangrove, and total SOC storage in the upper 100 cm was 8.8548 × 106 t, approximately 0.51% of that in the soils of Guangdong Province China. Approximately 46.5% to 70.5% of the SOC pool was stored in the upper 40-cm depth, and SOC densities were much consistent in depth distributions under different land uses. Different changes of SOC density were evidenced after the conversion from paddy fields to orchards, vegetable land and grassland. The uncertainties were also discussed for lack of the data from a long term survey at a particular location.
[Show abstract][Hide abstract] ABSTRACT: A total of 66 surface (0–10 cm) soil samples covering the whole territory of Hong Kong were collected for analysis of the seven PCB congeners. The detectable concentrations of PCBs in the soils of Hong Kong ranged from 0.07 to 9.87 μg kg− 1, with a higher concentration in the urban area than in the countryside. PCB patterns were dominated by the low chlorinated congeners. PCB118, a dioxin-like congener, was found in samples from Tsuen Wan and Sha Tin and was assumed to be deposited from local sources. Principal component analysis (PCA) revealed that the sources of PCBs were mainly associated with Aroclor 1242 and Aroclor 1248. A significant linear correlation between the concentrations of soil organic matter (SOM) and the sum of 7 PCBs and of SOM and PCB153 was observed. In total, PCBs were not a severe contamination in the soils of Hong Kong from the current results. However, long-term monitoring is still recommended to keeping, especially in the landfill deposits and some urban parks.
[Show abstract][Hide abstract] ABSTRACT: A geochemical baseline provides the means to distinguish between the pedogenic origin and the anthropogenic origin of the
trace element in the environmental compartments. We collected 271 soil samples representative of different parent rocks and
soil types from the whole territory of Hong Kong and analyzed the composition of clay mineralogy and the contents of 15 chemical
elements (Fe, Cd, As, etc.) for these samples. The baseline was predicted with the method of the normalization procedure combined
with the relative cumulative frequency curve. The result indicated that Fe was the best reference element for the normalization
procedure among the five potential reference elements (Fe, Al, Sc, Ti, and Mn), followed by Sc and Ti. A poor correlation
was found between Sc, Ti, and Cu. The predicted baseline was much lower than the A-value of the Dutch List used usually in screening the polluted soil of Hong Kong, implying that the extent of heavy metal
pollution might have been underestimated with respect to local lands. We also applied the cluster analysis to distinguish
the geochemical associations of the trace elements due to its importance to the baseline. Approximately three major associations
including the Fe–Mn-oxides related, Al oxides or Al-bearing-clay-mineralogy related and sulfide- related associations were
observed from the dendrogram.
[Show abstract][Hide abstract] ABSTRACT: A soil column experiment was carried out to investigate the effects of inoculation of bacteria on metal bioavailability, mobility and potential leachability through single chemical extraction, consequential extraction and in situ soil solution extraction technologies. Results showed that bacteria inoculated, including Azotobacter chroococcum, Bacillus megaterium and Bacillus mucilaginosus, may pose both positive and negative impacts on bioavailability and mobility of heavy metals in soil, depending on the chemical nature of the metals. The activities of bacteria led to an increase of water dissolved organic carbon (DOC) concentration and a decrease of pH value, which enhanced metal mobility and bioavailability (e.g. an increase of water-soluble and HOAc-soluble Zn). On the other hand, bacteria could immobilize metals (e.g. a great reduction of water-soluble Pb) due to the adsorption by bacterial cell walls and possible sedimentation reactions with phosphate or other anions produced through bacterial metabolism.
[Show abstract][Hide abstract] ABSTRACT: Surface soil (0-10 cm) samples from 53 sampling sites including rural and urban areas of Hong Kong were collected and analyzed for 16 EPA priority polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations were in the range of 7.0-410 microg kg(-1) (dry wt), with higher concentrations in urban soils than that in rural soils. The three predominant PAHs were Fluoranthene, Naphthalene and Pyrene in rural soils, while Fluoranthene, Naphthalene and Benzo(b + k)fluoranthene dominated the PAHs of urban soils. The values of PAHs isomer indicated that biomass burning might be the major origin of PAHs in rural soils, but vehicular emission around the heavy traffic roads might contribute to the soil PAHs in urban areas. A cluster analysis was performed and grouped the detectable PAHs under 4 clusters, which could be indicative of the PAHs with different origins and PAHs affected by soil organic carbon contents respectively.
[Show abstract][Hide abstract] ABSTRACT: A pot experiment was conducted to study the effect of growing vetiver grass on the biodegradation of benzo[a]pyrene (B[a]P) under glasshouse conditions. Plant biomass, microbial biomass C and degradation of B[a]P were determined. B[a]P disappeared faster in the plant treatments than in unplanted controls. Disappearance of B[a]P was accompanied by an increase in soil microbial biomass C. Vetiver grass may promote the biodegradation of B[a]P under flooded conditions by plant roots by stimulating the microbial biomass. Microbial biomass was the main factor affecting dissipation of B[a]P under flooded conditions.
Environmental Geochemistry and Health 04/2006; 28(1-2):183-8. DOI:10.1007/s10653-005-9029-6 · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An incubation experiment was conducted to monitor effect of sewage sludge application on changes in numbers of faecal coliforms in soils over time after sludge application and evaluate the hygiene risks. Soil faecal coliform counts were made after 1, 7, 14, 28, 56 and 84 days of incubation. The faecal coliform counts in the sludge-treated soils decreased substantially with time and were similar to those in the untreated controls after incubation for 56 days. Land application of air-dried sludges increased the hygiene risks due to the re-growth of faecal coliforms, and the counts of faecal coliforms in soil treated with air dried sludge from Suzhou (91% DM) were 50 times higher than in soils with fresh dewatered sludge from Suzhou (15% DM) after 7 days of incubation. The main factors affecting the changes in faecal coliform counts were sludge type and incubation time. Sludge type determined the faecal coliform counts and the ability of the faecal coliforms to re-establish, and indigenous microorganisms competed with the faecal coliforms for nutrients during the incubation process.
Environmental Geochemistry and Health 04/2006; 28(1-2):97-101. DOI:10.1007/s10653-005-9018-9 · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It was short of research on the organochlorine pesticides (OCPs) residues in the soils of Hong Kong. Sixty-six representative soil samples were collected from the 46 sites covering five types of land uses in Hong Kong. Hexachlorohexanes (HCH) and 7 Stockholm Convention OCPs were analyzed by gas chromatograph (GC) equipped with a Nickel 63 electronic capture detector (muECD). The results presented that HCH and 5 Stockholm Convention pesticides were detected in Hong Kong soils although the detectable ratio varies to a great extent. The concentration sequence of the five detectable OCPs was HCH > dichlorodiphenyltrichloroethane (DDT) > hexachlorobenzene (HCB) approximately = Endrin > alpha-endosulfan. Among the OCPs and their homologues or isomers, beta-HCH and p,p'-DDE were the two predominant substances according to the concentrations and detectable ratios, concentrations of which in soils were averagely 6.12 microg kg(-1) and 0.41 microg kg(-1) respectively. Soil horizon samples of 0-10 cm, 10-30 cm and >30 cm depth were selected from nine soil profiles to demonstrate the depth distributions of DDT and HCH in soil profiles. Concentrations of HCH tended to increase gradually from the topsoil to bottom layer while the lowest concentration of DDT is usually found in the subsoil (10-30 cm) in most sampling sites. In addition, close correlations of pH(KCl) and total organic carbon (TOC) with HCH indicated an effect on the residues of HCH caused by these two soils properties, but such relationships were not found with DDT or other OCPs.
[Show abstract][Hide abstract] ABSTRACT: A greenhouse study was carried out with Brassica juncea to critically evaluate effects of bacterial inoculation on the uptake of heavy metals from Pb-Zn mine tailings by plants. Application of plant growth-promoting rhizobacteria, including nitrogen-fixing bacteria and phosphate and potassium solubilizers, might play an important role in the further development of phytoremediation techniques. The presence of these beneficial bacteria stimulated plant growth and protected the plant from metal toxicity. Inoculation with rhizobacteria had little influence on the metal concentrations in plant tissues, but produced a much larger above-ground biomass and altered metal bioavailability in the soil. As a consequence, higher efficiency of phytoextraction was obtained compared with control treatments.
[Show abstract][Hide abstract] ABSTRACT: Plants that hyperaccumulate metals are ideal subjects for studying the mechanisms of metal and mineral nutrient uptake in the plant kingdom. Indian Mustard (Brassica juncea) has been shown to accumulate moderate levels of Cd, Pb, Cr, Ni, Zn, and Cu. In this experiment, 10 levels of Cd concentration treatments were imposed by adding 10-190 mg Cd kg(-1) to the soils as cadmium nitrate [Cd(NO3)2]. The effect of Cd on phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and the micronutrients iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in B. juncea was studied. Plant growth was affected negatively by Cd, root biomass decreased significantly at 170 mg Cd kg(-1) dry weight soils treatment. Cadmium accumulation both in shoots and roots increased with increasing soil Cd treatments. The highest concentration of Cd was up to 300 mg kg(-1) d.w. in the roots and 160 mg kg(-1) d.w. in the shoots. The nutrients mainly affected by Cd were P, K, Ca, Fe, and Zn in the roots, and P, K, Ca, and Cu in the shoots. K and P concentrations in roots increased significantly when Cd was added at 170 mg kg(-1), and this was almost the same level at which root growth was inhibited. Zn concentrations in roots decreased significantly when added Cd concentration was increased from 50 to 110 mg kg(-1), then remained constant with Cd treatments from 110 to 190 mg kg(-1). However, Zn concentrations in the shoots seemed less affected by Cd. It is possible that Zn uptake was affected by the Cd but not the translocation of Zn within the plant. Ca and Mg accumulation in roots and shoots showed similar trends. This result indicates that Ca and Mg uptake is a non-specific process.
Environmental Geochemistry and Health 05/2004; 26(2-3):319-24. DOI:10.1023/B:EGAH.0000039596.15586.b3 · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An orthogonally designed experiment was conducted to study the single and combined effects of N, P and K on phytoremediation of Cu-polluted soil by Indian mustard. Addition of fertilizer N and P significantly increased Indian mustard shoot yield. Two high treatments combined with N resulted in the highest yields, followed by low-P combined with N. In contrast, high P with no N gave no yield increase and K had no effect on yield of Indian mustard. Nitrogen and P increased the amount of chlorophyll in the leaves, indicating that the yield increases were due to enhanced photosynthesis. Nitrogen application had no effect on plant Cu concentrations but addition of P slightly decreased plant Cu concentrations, likely a dilution effect resulting from the increase in yield. Among the treatments, N and P applied at 100 and 200 mg kg(-1) respectively with no K application resulted in the highest Cu uptake. Thus, a combination of low N and high P produced a yield increase in Indian mustard that was more than adequate to compensate for a slight decrease in Cu concentration, resulting in the highest Cu removal from the contaminated soil.
Environmental Geochemistry and Health 05/2004; 26(2-3):331-5. DOI:10.1023/B:EGAH.0000039598.24033.4e · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mycorrhizal and non-mycorrhizal alfalfa (Medicago sativa) was grown in pots containing soil artificially contaminated with various levels of benzo[a]pyrene (B[a]P) (0, 1, 10 and 100 mg kg(-1)). Soil and plants were sampled after 30, 40, 50, 60 and 90 days and compared with unlanted pots. The percentage of mycorrhizal root length colonized by Glomus caledoniun was not significantly affected by the addition of B[a]P up to 10 mg kg(-1) but was significantly lower at 100 mg kg(-1)B[a]P compared with low concentrations (p < 0.05). There was no difference in soil polyphenol oxidase and dehydrogenase activity among the controls and applications of 1 and 10 mg kg(-1) of B[a]P. However, enzyme activities were significantly higher at 100 mg kg(-1) B[a]P compared with the other three treatments, and there was no mycorrhizal effect. Over a period of 90 days the concentration of B[a]P in soil in which alfalfa was grown was significantly lower than in unplanted soil (p < 0.05). Degradation rates of B[a]P added at 1, 10 and 100 mg kg(-1) without G. caledonium were 76, 78 and 53%, and with mycorrhizal inoculation were 86, 87 and 57%. The degradation rate in unplanted soil was significantly lower than in planted soil, and was significantly higher in medium- and low-B[a]P treatments than in the high B[a]P concentration tested. There is a possibility of enhancement phytoremediation of PAHs in rhizosphere soil with arbuscular mycorrhizal fungi.
Environmental Geochemistry and Health 05/2004; 26(2-3):285-93. DOI:10.1023/B:EGAH.0000039592.80489.e5 · 2.57 Impact Factor