[Population structure of food-borne Staphylococcus aureus in China]

Objective: To understand the population structure of food-borne Staphylococcus (S.) aureus in China. Methods: Whole genome sequencing was used to analyze 763 food-borne S. aureus strains from 16 provinces in China from 2006 to 2020. Multilocus sequence typing (MLST), staphylococcal protein A gene (spa) typing, and staphylococcal chromosome cassettemec (SCCmec) typing were conducted, and minimum spanning tree based on ST types (STs) was constructed by BioNumerics 7.5 software. Thirty-one S. aureus strains isolated from imported food products were also included in constructing the genome phylogenetic tree. Results: A total of 90 STs (20 novel types) and 160 spa types were detected in the 763 S. aureus isolates. The 72 STs (72/90, 80.0%) were related to 22 clone complexes. The predominant clone complexes were CC7, CC1, CC5, CC398, CC188, CC59, CC6, CC88, CC15, and CC25, accounting for 82.44% (629/763) of the total. The STs and spa types in the predominant clone complexes changed over the years. The methicillin-resistant S. aureus (MRSA) detection rate was 7.60%, and 7 SCCmec types were identified. The ST59-t437-Ⅳa (17.24%, 10/58), ST239-t030-Ⅲ (12.07%, 7/58), ST59-t437-Ⅴb (8.62%, 5/58), ST338-t437-Ⅴb (6.90%, 4/58) and ST338-t441-Ⅴb (6.90%, 4/58) were the main types in MRSA strains. The genome phylogenetic tree had two clades, and the strains with the same CC, ST, and spa types clustered together. All CC7 methicillin sensitive S. aureus strains were included in Clade1, while 21 clone complexes and all MRSA strains were in Clade2. The MRSA strains clustered according to the SCCmec and STs. The strains from imported food products in CC398, CC7, CC30, CC12, and CC188 had far distances from Chinese strains in the tree. Conclusions: In this study, the predominant clone complexes of food-borne strains were CC7, CC1, CC5, CC398, CC188, CC59, CC6, CC88, CC15, and CC25, which overlapped with the previously reported clone complexes of hospital and community-associated strains in China, suggesting that close attention needs to be paid to food, a vehicle of pathogen transmission in community and food poisoning.

[Application and clinical efficacy of ultrasound debridement method in residual burn wounds]

Objective: To investigate the application and clinical efficacy of ultrasound debridement method in residual burn wounds. Methods: A retrospective cohort study was conducted. From August 2017 to August 2021, 64 patients with residual burn wounds who met the inclusion criteria were admitted to the 980th Hospital of the Joint Logistic Support Force of PLA. According to the debridement method adopted for the residual wounds, the patients were divided into ultrasound debridement group (34 cases, 22 males and 12 females, aged (31±13) years) and traditional debridement group (30 cases, 19 males and 11 females, aged (32±13) years). After the corresponding debridement, the wounds of patients in the two groups were selected for stamp skin grafting or large skin grafting according to the wound site and skin donor status. For unhealed wounds after stage Ⅰ surgery, secondary debridement and skin grafting were be performed, with the wound debridement methods in the 2 groups being the same as those of stage Ⅰ, respectively. On postoperative day 3, drug-sensitive test was used to detect the bacteria in the wound and the positive rate of bacteria was calculate. On postoperative day 7, the survival rate of skin slices in wound and the incidence of subcutaneous hematoma were calculated. At discharge, wound healing time and debridement times of patients were counted, and the secondary debridement rate was calculated. Data were statistically analyzed with independent sample t test or chi-square test. Results: On postoperative day 3, the wounds in ultrasound debridement group were infected with Staphylococcus aureus in 2 cases and Pseudomonas aeruginosa in 2 cases, and the wounds in traditional debridement group were infected with Staphylococcus aureus in 5 cases, Pseudomonas aeruginosa in 3 cases, Acinetobacter baumannii in 1 cases, Klebsiella pneumoniae in 1 cases, and Enterobacter cloacae in 1 cases. The positive rate of bacteria of wound in ultrasound debridement group was significantly lower than that in traditional debridement group (χ2=5.51, P<0.05). On postoperative day 7, the survival rate of skin grafts in ultrasound debridement group was (92±5) %, which was significantly higher than (84±10) % in traditional debridement group (χ2=6.78, P<0.01); the incidence of subcutaneous hematoma in ultrasound debridement group was 17.6% (6/34), which was significantly lower than 40.0%( 12/30) in traditional debridement group, χ2=3.94, P<0.05. At discharge, the wound healing time in ultrasound debridement group was (11.0±2.0) d, which was significantly shorter than (13.0±3.1) d in traditional debridement group (t=3.81, P<0.01); the secondary debridement rate of wounds in ultrasound debridement group was 2.9% (1/34), which was significantly lower than 20.0% (6/30) in traditional debridement group (χ2=4.76, P<0.05). Conclusions: Ultrasound debridement method can significantly reduce the bacterial load of residual burn wounds, reduce postoperative hematoma formation, and promote the survival of skin grafts to shorten the course of disease of patients.

[Mucinous adenocarcinoma of the gallbladder: report of 5 cases]

The clinical manifestations, laboratory and imaging results, diagnosis and treatment and prognosis of 5 patients with mucinous adenocarcinoma of the gallbladder were analyzed. It was found that the clinical characteristics of mucinous adenocarcinoma of the gallbladder were very similar to that of gallbladder malignant tumor, and it was difficult to differentiate. Ultrasound guided gallbladder needle biopsy can confirm the diagnosis before surgery. Surgery is still the first choice of treatment. Since laparoscopic surgery has obvious advantages over open surgery, it is recommended to be preferentially used. If the tumor is under T2 stage and has no aggressive metastasis, the prognosis is generally good.

Cathepsin L is involved in proliferation and invasion of breast cancer cells

Cathepsin L(CTSL), a lysosomal endopeptidase was found overexpressed in Breast cancer (BC). The purpose of this work was to investigate the possible role of CTSL in the development of BC. RNA interference(RNAi) with a CTSL small hairpin RNAs(CTSL-shRNA) and plasmid with CTSL were used to identify the effects of CTSL on malignant behaviors of BC. MCF-7 and SKBR-3 were selected as cell models in vitro and in vivo. The results showed that down-regulation of CTSL can significantly inhibit the proliferative and invasive ability of MCF-7 cell, while up-regulation of CTSL in SKBR-3 cells had opposite effects. Comparing to parental BC cells, CTSL knockdown cells exhibited attenuated capacities in developing tumor in nude mice, furthermore, the growth of these xenografts were dramatically regressed. In conclusion, our findings suggest that CTSL contributes to the proliferation and metastasis of BC and might be a potent molecular target for BC treatment.

Evaluation of soil amendments as a remediation alternative for cadmium-contaminated soils under cacao plantations

Elevated plant-available cadmium (Cd) in soils results in contamination to cacao (Theobroma cacao L) beans. Effectiveness of vermicompost and zeolite in reducing available Cd in three cacao-growing soils was studied under laboratory conditions. Sorption-desorption experiments were conducted in soils and amendments. Cadmium was added at 0 or 5 mg kg(-1) (spiked), then, amendments were incorporated at 0, 0.5, or 2 %. Amended soils were incubated at room temperature for 28 days. Plant-available Cd was determined using 0.01 M CaCl2 (WSE) and Mehlich 3 (M3) extraction procedures in subsamples taken from individual bags at six time intervals. Soils and amendments displayed different sorption characteristics and a better fit was attained with Freundlich model (R (2) > 0.82). Amendments were ineffective in reducing extractable Cd in non-spiked soils. In Cd-spiked soils, vermicompost at 2 % significantly reduced WSE-Cd (P < 0.01) from 3.36, 0.54, and 0.38 mg kg(-1) to values lower that instrument's detection in all the three soils and significantly diminished M3-extractable Cd (P < 0.05) from 4.62 to 4.11 mg kg(-1) in only one soil. Vermicompost at 0.5 % significantly decreased WSE-Cd (P < 0.01) from 3.04 and 0.31 to 1.69 and 0.20 mg kg(-1), respectively, in two soils with low sorption capacity for Cd. In contrast, zeolite failed to reduce WSE- or M3-extractable Cd in all studied soils. A negative correlation occurred between soil pH and WSE-Cd (r > -0.89, P < 0.01). The decrease in WSE-Cd appears to be associated with the increase in pH of the vermicompost-amended soils.

Chemical speciation of cadmium: An approach to evaluate plant-available cadmium in Ecuadorian soils under cacao production

Elevated concentration of cadmium (Cd) in cacao beans has raised serious concerns about the chocolate consumption on human health. Accumulation of Cd in cacao bean in southern Ecuador has been related to soil contamination. In this study, soil fractionation approach was used to identify available Cd pools in the soils and to correlate these Cd pools with bean Cd concentration and soil test indexes. The distribution of soil Cd fractions decreased in the order: oxidizable > acid-soluble > residual > reducible >> water-soluble (+exchangeable). Oxidizable and acid-soluble fractions accounted for 59 and 68% of the total recoverable Cd for the 0-5 and 5-15 cm soil depth, respectively. Acid-soluble fraction was closely related to bean-Cd, with correlation coefficients (r) of 0.70 and 0.81 (P < 0.01) for the 0-5 and 5-15 cm soil depth, respectively. Acid-soluble Cd was significantly correlated with 0.01 M HCl- (r = 0.99, P < 0.01) or Mehlich 3- extractable Cd (r = 0.97, P < 0.01). These results indicate that acid-soluble Cd fraction is an important part of available Cd pool. Since approximately 60% of Cd in the cacao-growing soils is related to the acid-soluble fraction and bound to organic matter, remediation of the contaminated soils should consider to the dynamics of soil pH and organic matter content.

Concentration of cadmium in cacao beans and its relationship with soil cadmium in southern Ecuador

Cadmium (Cd) content in cacao beans above a critical level (0.6 mg kg(-1)) has raised concerns in the consumption of cacao-based chocolate. Little is available regarding Cd concentration in soil and cacao in Ecuador. The aim of this study was to determine the status of Cd in both, soils and cacao plants, in southern Ecuador. Soil samples were collected from 19 farms at 0-5, 5-15, 15-30, and 30-50 cm depths, whereas plant samples were taken from four nearby trees. Total recoverable and extractable Cd were measured at the different soil depths. Total recoverable Cd ranged from 0.88 to 2.45 and 0.06 to 2.59, averaged 1.54 and 0.85 mg kg(-1), respectively in the surface and subsurface soils whereas the corresponding values for M3-extractable Cd were 0.08 to 1.27 and 0.02 to 0.33 with mean values of 0.40 and 0.10 mg kg(-1). Surface soil in all sampling sites had total recoverable Cd above the USEPA critical level for agricultural soils (0.43 mg kg(-1)), indicating that Cd pollution occurs. Since both total recoverable and M3-extractable Cd significantly decreased depth wise, anthropogenic activities are more likely the source of contamination. Cadmium in cacao tissues decreased in the order of beans>shell>>leaves. Cadmium content in cacao beans ranged from 0.02 to 3.00, averaged 0.94 mg kg(-1), and 12 out of 19 sites had bean Cd content above the critical level. Bean Cd concentration was highly correlated with M3- or HCl-extractable Cd at both the 0-5 and 5-15 cm depths (r=0.80 and 0.82 for M3, and r=0.78 and 0.82 for HCl; P<0.01). These results indicate that accumulation of Cd in surface layers results in excessive Cd in cacao beans and M3- or HCl-extractable Cd are suitable methods for predicting available Cd in the studied soils.

Implication of polymorphisms in DNA repair genes with an increased risk of hepatocellular carcinoma

We explored the association between 4 XRCC1 (Arg194Trp and Arg399Gln) and XPD (Asp312Asn and Lys751Gln) polymorphisms with the development and prognosis of hepatocellular carcinoma (HCC). A total of 218 cases with HCC and 277 healthy controls were included in the study. Genotyping of the XRCC1 (Arg194Trp and Arg399Gln) and XPD (Asp312Asn and Lys751Gln) polymorphisms was performed in a 384-well plate format on the Sequenom MassARRAY platform. We found that individuals with the XRCC1 399AA genotype had a higher risk of HCC compared with the GG genotype (odds ratio, OR = 1.85, 95% confidence interval, CI = 1.03-3.23). Similarly, individuals carrying the XPD 751GG genotype showed a greatly increased risk of HCC (OR = 2.97, 95%CI = 126- 7.38). Cox regression analysis showed that individuals carrying XPD 751Gln/Gln genotypes had a 0.30-fold increased risk of death from HCC. These results suggest that polymorphisms in XRCC1 and XPD may have functional significance in HCC.

Enhanced adsorption of fluoride from aqueous solution using an iron-modified attapulgite adsorbent

Attapulgite modified with iron was used as an adsorbent for fluoride removal from aqueous solutions. The pristine attapulgite and the iron-modified attapulgite composite were characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) techniques, and the pH point of zero charge measurement. The XRD analysis indicates the existence of iron oxide hydroxide (FeO[OH]) in the iron-modified attapulgite composite. The FT-IR spectra of the iron-modified attapulgite composite before and after adsorption indicate that the involvement of the hydroxide radical in the fluoride adsorption. The effects of pH, contact time, initial concentration, and temperature on fluoride adsorption by the adsorbent were studied in a batch system. Kinetics studies show that the fluoride adsorption kinetics over the adsorbent is well-described by the pseudo-second-order kinetic model. The fluoride adsorption isotherm is well-fitted by the Langmuir model. Desorption studies show that the iron-modified attapulgite adsorbent can be easily regenerated at pH 12.5. The adsorption mechanism is discussed in detail.

Reclaimed wastewater: impact on soil-plant system under tropical conditions

This study investigated the ionic speciation of reclaimed urban wastewater (RWW), and the impact of increasing RWW irrigation rates on soil properties and plant nutrition under field conditions. Most RWW elements (>66%) are readily available as NH(4)(+), Ca(2+), Mg(2+), K(+), SO(4)(2-), Cl(-), H(3)BO(3), Mn(2+) and Zn(2+), but in imbalanced proportion for plant nutrition. Lead, Cd, Cr and Al in RWW are mostly bounded with DOM or OH(-).(.)Irrigation with RWW decreased soil acidity, which is beneficial to the acidic tropical soil. Although RWW irrigation builds exchangeable Na(+) up, the excessive Na(+) was leached out of the soil profile after a rainy summer season (>400 mm). Benefits of the disposal of RWW to the soil under tropical conditions were discussed, however, the over irrigation with RWW (>100% of crop evapotranspiration) led to a nutritional imbalance, accumulating S and leading to a plant deficiency of P and K.

Assessing lead thresholds for phytotoxicity and potential dietary toxicity in selected vegetable crops

Lead tolerance and accumulation in shoots and edible parts varied with crop species and soil type. The critical Pb concentrations at 10% yield reduction were 24.71, 28.25, and 0.567 mg kg(-1) for pakchoi, celery, and hot pepper, respectively under hydroponic conditions, whereas were 13.1, 3.83, 0.734 mg kg(-1) grown in the Inceptisol and 31.7, 30.0, 0.854 mg kg(-1) in the Alluvial soil, respectively. Based on the threshold of human dietary toxicity for Pb, the critical levels of soil available Pb for pakchoi, celery, and hot pepper were 5.07, 8.06, and 0.48 mg kg(-1) for the Inceptisol, and 1.38, 1.47, and 0.162 mg kg(-1) for the Alluvial soil, respectively. Similarly, the total soil Pb thresholds were different from vegetable species and soil types.

Adsorption-desorption characteristics of mercury in paddy soils of China

Mercury (Hg) has received considerable attention because of its association with various human health problems. Adsorption-desorption behavior of Hg at contaminated levels in two paddy soils was investigated. The two representative soils for rice production in China, locally referred to as a yellowish red soil (YRS) and silty loam soil (SLS) and classified as Gleyi-Stagnic Anthrosols in FAO/UNESCO nomenclature, were respectively collected from Jiaxin County and Xiasha District of Hangzhou City, Zhejiang Province. The YRS adsorbed more Hg(2+) than the SLS. The characteristics of Hg adsorption could be described by the simple Langmuir adsorption equation (r2 = 0.999 and 0.999, P < 0.01, respectively, for the SLS and YRS). The maximum adsorption values (Xm) that were obtained from the simple Langmuir model were 111 and 213 mg Hg(2+) kg(-1) soil, respectively, for the SLS and YRS. Adsorption of Hg(2+) decreased soil pH by 0.75 unit for the SLS soil and 0.91 unit for the YRS soil at the highest loading. The distribution coefficient (kd) of Hg in the soil decreased exponentially with increasing Hg(2+) loading. After five successive desorptions with 0.01 mol L(-1) KCl solution (pH 5.4), 0 to 24.4% of the total adsorbed Hg(2+) in the SLS soil was desorbed and the corresponding value of the YRS soil was 0 to 14.4%, indicating that the SLS soil had a lower affinity for Hg(2+) than the YRS soil at the same Hg(2+) loading. Different mechanisms are likely involved in Hg(2+) adsorption-desorption at different levels of Hg(2+) loading and between the two soils.

Effects of pH, organic acids, and competitive cations on mercury desorption in soils

The effects of pH, organic acids, and competitive cations on Hg(2+) desorption were studied. Three representative soils for rice production in China, locally referred to as a yellowish red soil (YRS), purplish clayey soil (PCS), and silty loam soil (SLS) and classified as Gleyi-Stagnic Anthrosols in FAO/UNESCO nomenclature, were, respectively, collected from Jiaxin County, Deqing County, and Xiasha District of Hangzhou City, Zhejiang Province. Most of the added Hg(2+) was adsorbed at low initial concentrations (<2 mg l(-1)). Desorption of the adsorbed Hg(2+) in 0.01M KCl (simulating soil solution) was minimal, but was significantly enhanced by the change of pH, and the presence of organic acids or competitive cations. The desorption of Hg(2+) in the soils decreased with pH from 3.0 to 5.0, leveled off at pH 5.0-8.0, but increased with pH from 7.0 to 9.0. The presence of organic ligands enhanced Hg(2+) desorption in the soils except for YRS, in which the addition of tartaric, malic, or oxalic acid reduced Hg(2+) desorption at low concentrations (<10(-4)M), but Hg(2+) desorption generally increased with organic acid concentration. Citric acid was most effective in increasing Hg(2+) desorption, followed by tartaric acid and malic acid; and oxalic acid was the least effective. Desorption of adsorbed Hg(2+) increased with increasing concentrations of added Cu(2+) or Zn(2+). Applied Cu(2+) increased Hg(2+) desorption more than Zn(2+) at the same loading rate.

CAPSULE

The effects of organic acids and competitive cations on Hg desorption in soil-water system are related to their concentrations, basic chemical properties, and soil properties.

Effects of pH, organic acids, and inorganic ions on lead desorption from soils

The desorption characteristics of lead in two variable charge soils (one developed from Arenaceous rock (RAR) and the other derived from Quaternary red earths (REQ)) were studied, and the effects of pH value, organic acid, and competitive ions were examined. Desorption of Pb(2+) decreased from nearly 100.0 to 20.0% within pH 1.0-4.0 in both soils, and then the decrease diminished at pH > 4.0. Organic ligands at relatively low concentrations (< or =10(-3) mol L(-1)) slightly inhibited Pb(2+) desorption, but enhanced Pb(2+) desorption at higher concentrations. In this study, citric acid or acetic acid at higher concentrations (>10(-3) mol L(-1)) had the greatest improvement of Pb(2+) desorption, followed by malic acid; and the smallest was oxalic acid. Desorption of the adsorbed Pb(2+) increased greatly with increasing concentrations of added Cu(2+) or Zn(2+). Applied Cu(2+) increased Pb(2+) desorption more than Zn(2+) at the same loading.

Leaching potential of heavy metals (Cd, Ni, Pb, Cu and Zn) from acidic sandy soil amended with dolomite phosphate rock (DPR) fertilizers

There is an increasing concern on heavy metal leaching from the soils amended with sewage sludge. A column study was conducted to examine the extent of leaching of five important heavy metals (Cd, Ni, Pb, Cu and Zn) from an acidic sandy soil amended with different dolomite phosphate rock (DPR) fertilizers (an application rate of 1% fertilizers) developed from DPR and N-Viro (consisting of biosolids and fly ash) at 0%, 10%, 20%, 30%, 40%, 50% and 100% DPR. Ten leaching events were carried out with each event done at an interval of 7 days and with total leaching volume of 1183mm, which is equivalent to the mean annual rainfall of this region during the period of 2001-2003. Leachate was collected after each leaching event and analyzed for heavy metals. The maximum leachate concentrations of Cd, Ni, Pb, Cu and Zn were all below drinking water quality guidance limits set by Florida Department of Environmental Protection and World Health Organization, suggesting that the application of DPR fertilizers may not pose a threat to water quality by leaching. Most of leachate concentrations of Cd, Ni and Pb were below their detection limits and there were no significant differences between the control and the treatments with different DPR fertilizers. By contrast, there were higher leachate concentrations of Cu and Zn (ranging from 0.7 to 37.1mug Cu/l and 5.1 to 205.6mug Zn/l for all treatments) due to their higher contents in both the soil and different DPR fertilizers compared with Cd, Ni and Pb. The leachate concentrations of Cu and Zn for each treatment decreased with increasing leaching events. The differences in leachate concentrations of Cu and Zn between the control and the treatments with different DPR fertilizers containing N-Viro were significant, especially in the first several leaching events and, moreover, they increased with increasing proportion of N-Viro in the DPR fertilizers. There were similar trends in total losses of Cu and Zn after ten leaching events. Greater differences in both leachate concentrations and total losses of Zn between the control and the treatments containing N-Viro were noted. Total losses of Zn for the treatments containing N-Viro were 3.0-5.1 times higher than those for the control compared with 1.4-2.2 times higher for total losses of Cu, suggesting that greater proportions of Zn losses came from the DPR fertilizers due to the greater mobility of Zn in the DPR fertilizers compared with Cu.

Use of dolomite phosphate rock (DPR) fertilizers to reduce phosphorus leaching from sandy soil

There is increasing concern over P leaching from sandy soils applied with water-soluble P fertilizers. Laboratory column leaching experiments were conducted to evaluate P leaching from a typical acidic sandy soil in Florida amended with DPR fertilizers developed from dolomite phosphate rock (DPR) and N-Viro soil. Ten leaching events were carried out at an interval of 7 days, with a total leaching volume of 1,183 mm equivalent to the mean annual rainfall of this region during the period of 2001-2003. Leachates were collected and analyzed for total P and inorganic P. Phosphorus in the leachate was dominantly reactive, accounting for 67.7-99.9% of total P leached. Phosphorus leaching loss mainly occurred in the first three leaching events, accounting for 62.0-98.8% of the total P leached over the whole period. The percentage of P leached (in the total P added) from the soil amended with water-soluble P fertilizer was higher than those receiving the DPR fertilizers. The former was up to 96.6%, whereas the latter ranged from 0.3% to 3.8%. These results indicate that the use of N-Viro-based DPR fertilizers can reduce P leaching from sandy soils.

Growth response and phytoextraction of copper at different levels in soils by Elsholtzia splendens

Phytoremediation is a promising approach for cleaning up soils contaminated with heavy metals. Information is needed to understand growth response and uptake mechanisms of heavy metals by some plant species with exceptional capability in absorbing and superaccumulating metals from soils. Greenhouse study, field trial, and old mined area survey were conducted to evaluate growth response and Cu phytoextraction of Elsholtzia splendens in contaminated soils, which has been recently identified to be tolerant to high Cu concentration and have great potential in remediating contaminated soils. The results from this study indicate that the plant exhibited high tolerance to Cu toxicity in the soils, and normal growth was attained up to 80 mg kg(-1) available soil Cu (the NH4OAc extractable Cu) or 1000 mg kg(-1) total Cu. Under the field conditions, a biomass yield of 9 ton ha(-1) was recorded at the soil available Cu level of 77 mg kg(-1), as estimated by the NH4OAc extraction method. Concentration-dependent uptake of Cu by the plant occurred mainly at the early growth stage, and at the late stage, there is no difference in shoot Cu concentrations grown at different extractable soil Cu levels. The extractability of Cu from the highly polluted soil is much greater by the roots than that by the shoots. The NH4OAc extractable Cu level in the polluted soil was reduced from 78 to 55 mg kg(-1) in the soil after phytoextraction and removal of Cu by the plant species for one growth season. The depletion of extractable Cu level in the rhizosphere was noted grown in the mined area, even at high Cu levels, the NH4OAc extractable Cu in the rhizosphere was 30% lower than that in the bulk soil. These results indicate that phytoextraction of E. splendens can effectively reduce the plant-available Cu level in the polluted soils.

Characteristics of cadmium uptake and accumulation by two contrasting ecotypes of Sedum alfredii Hance

The mined ecotype of Sedum alfredii Hance has been identified to be a zinc (Zn) hyperaccumulator native to China. In the present article, the characteristics of cadmium (Cd) uptake and accumulation were compared with hydroponic experiments between the mined and the nonmined ecotypes of Sedum alfredii Hance. The results indicate that the plants of the mined ecotype (ME) have higher tolerance of Cd than the plants of the nonmined ecotypes (NME) in terms of dry matter yield. The thresholds of external Cd levels for the reduction of plant growth were 100 micromolL(-1) for the NME and 400 micromolL(-1) for the ME, respectively. Kinetic study showed that the rates of Cd influx into roots (IR) and transport to shoots (TR) were higher in the ME than in the NME, with 5-fold higher for the maximum IR (Imax) and 13-fold higher for the maximum TR (Tmax) in the NME, respectively. Cadmium concentrations increased with increasing external Cd supply levels. Root Cd concentrations in the NME were higher than that in the ME, with a maximum being 5646 mg kg(-1) for the NME and 2889 mg kg(-1) for the ME at 1000 micromolL(-1) Cd. On the contrary, shoot Cd concentrations of the NME were far lower than that of the ME. Maximum shoot Cd concentrations were 533 mg kg(-1) in leaves and 935 mg kg(-1) in stems at 1000 micromol L(-1) Cd for NME, whereas, 4933 and 3874 mg kg(-1) at 400 micromol L(-1) Cd for the ME, respectively. Meanwhile, Cd concentrations in the shoots of both the NME and ME increased with advancing Cd treatment time. At 100 micromolL(-1) Cd, concentrations of Cd in leaves and stems of the NME sharply increased within initial 8 and 12 days, and those in the ME increased dramatically until D20 and D16, respectively. However, leaf and stem Cd concentrations reached their maximum values on D4 for the NME and D8 for the ME, respectively, when the plants were exposed to 1 micromol L(-1) Cd. Cadmium accumulation by plant shoots was obvious higher in the ME than in the NME at varied Cd supply levels or Cd treatment time. The maximum Cd taken up by the shoots was 1032 microg plant(-1) in concentration-dependent uptake, and 1699 microg plant(-1) in time-course uptake for the ME, with 15-fold and 18-fold higher than those for the NME, respectively. The ratios of shoot/root of Cd ranged from 12 to 39, varying with Cd supply levels, and from 13 to 24 in the varied treatment times for the ME, more than 10 times greater than those for the NME. In addition, Cd distribution in leaves, stems and roots of ME was greatly different from those of NME. The percentage of Cd distribution in shoots was more than 79 at the varied Cd supply levels, or 83 in the varied treatment time for ME, both higher than that for NME. It could be concluded that the mined ecotype of Sedum alfredii Hance has a greater ability to tolerate, transport, and accumulate Cd, as compared with the nonmined ecotype.

Solubility of phosphorus and heavy metals in potting media amended with yard waste-biosolids compost

The potential risk of surface and ground water contamination by phosphorus (P) and heavy metals leached from compost-based containerized media has become an environmental concern. Solubility and fractionation of P and heavy metals were evaluated in media containing 0, 25, 50, 75, or 100% compost derived from biosolids and yard trimmings for potential impacts on the environment. As compost proportion in peat-based media increased from 0 to 100%, concentrations of total P, Cd, Cu, Ni, Pb, Zn, and Mn in the media increased whereas concentrations of total Co and Cr decreased. Except for Cu, all heavy metals in the water-soluble fraction decreased with increasing compost proportion in the media, because of higher Fe, Al, and Ca concentrations and pH values of the composts than the peat. When the media pH is controlled and maintained at normal range of plant growth (5.5-6.5), leaching of the heavy metals is minimal. Incorporation of compost to the peat-based media also decreased the proportion of total P that was water-soluble. However, concentrations of bioavailable inorganic phosphorus (NaHCO3-IP), readily mineralizable organic phosphorus (NaHCO3-OP), potentially bioavailable inorganic phosphorus (NaOH-IP), and potentially bioavailable organic phosphorus (NaOH-OP) were still higher in the media amended with compost because of higher total P concentration in the compost. Further study is needed to verify if less or no topdressing of chemical P fertilizer should be applied to the compost-amended media to minimize P effect on the environment when compost-amended potting media are used for nursery or greenhouse crop production systems.

Adsorption-desorption characteristics of lead in variable charge soils

Adsorption desorption processes of Pb at contaminated levels in two variable charge soils were investigated. The red soil (RAR) developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) adsorbed more Pb2+ than the red soil (REQ) derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult). The maximum adsorption values (Xm) that were obtained from the simple Langmuir model were 52.6 mmol Pb2+ kg(-1) soil and 29.9 mmol Pb2+ kg(-1) soil, respectively, for the RAR and REQ. Adsorption of Pb2+ decreased soil pH by 1.10 unit for the RAR soil and 1.21 unit for the REQ soil at the highest loading. The adsorption equilibrium pH of RAR was higher than that of REQ at the same Pb2+ concentration. The distribution coefficient (Kd) of Pb in the soils decreased exponentially with increasing Pb2+ loading. Most of the adsorbed Pb2+ in the soils was not desorbed in the 0.01 mol L(-1) NaNO3 solution. After five successive extractions with NaNO3, only 0-11% of the total adsorbed Pb2+ in the RAR soil was desorbed and the corresponding value of the REQ soil was 0-19%, indicating that the RAR soil had a greater affinity for Pb2+ than the REQ soil at the same Pb2+ loading. Different mechanisms might be involved in Pb2+ adsorption/desorption at different levels of Pb2+ loading and between the two soils.

Accumulation and partitioning of phosphorus and heavy metals in a sandy soil under long-term vegetable crop production

Increased inputs of phosphorus (P) and heavy metals to agricultural soils have caused considerable concern. Information on accumulation and chemical forms of the elements in soils is needed as a guide for the judicious application of agricultural chemicals and organic manures. The focus of this study was to assess accumulation of P and heavy metals among various fractions of a sandy soil with a 25 year history of vegetable crop production and primarily inorganic fertilization. The results demonstrated that long-term vegetable production practices changed concentrations and partitioning of P and heavy metals in the soil. Phosphorus, Cu, Zn, and Mn were significantly accumulated and moved downward along the soil profile. Most of the total Cr in the vegetable soil accumulated in the upper 0-15 cm. However, there was no significant accumulation and transport of Cd, Co, Mo, Ni, and Pb in the vegetable soil. Major P fractions in the vegetable soil were NaHCO3-P, followed by HCl-P and residual P. Copper, Zn, and Mn accumulated predominantly in the CaCO3 fraction or oxide fraction, whereas Cr accumulated mainly in the organically bound fraction, indicating that P, Cu, Zn, and Mn in the vegetable soil have greater mobility potential. Compared with adjacent forest soil, the vegetable soil had a lower percentage of P, Cu, Zn, and Mn in the residual fractions, and a higher percentage of P, Cu, Zn, and Mn in the CaCO3 fractions or organically bound fraction.

Adsorption-desorption behavior of copper at contaminated levels in red soils from China

Adsorption-desorption of copper (Cu2+) at contaminated levels in two red soils was investigated. The red soil derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult) (REQ) adsorbed more Cu2+ than the red soil developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) (RAR). The maximum adsorption values (M(A)) that are obtained from the simple Langmuir model were 25.90 and 20.17 mmol Cu2+ kg(-1) soil, respectively, for REQ and RAR. Adsorption of Cu2+ decreased soil pH, by 0.8 unit for the REQ soil and 0.6 unit for the RAR soil at the highest loadings. The number of protons released per Cu2+ adsorbed increased sigmoidally with increasing initial Cu2+ concentration for the RAR soil, but the relationship was almost linear for the REQ soil. The RAR soil released about 2.57 moles of proton per mole of Cu2+ adsorbed at the highest Cu2+ loading and the corresponding value for the REQ soil was 1.12. The distribution coefficient (Kd) decreased exponentially with increasing Cu2+ loading. Most of the adsorbed Cu2+ in the soils was readily desorbed in the NH4Ac. After five successive extractions with 1 mol L(-1) NH4Ac (p 5.0), 61 to 95% of the total adsorbed Cu2+ in the RAR soil was desorbed and the corresponding value for the REQ soil was 85 to 92%, indicating that the RAR soil had a greater affinity for Cu2+ than the REQ soil at low levels of adsorbed Cu2+.

Release potential of phosphorus in Florida sandy soils in relation to phosphorus fractions and adsorption capacity

Information on P release potential in relation to labile P and P fractions in sandy soils is limited. In this study, P release potential was determined by leaching, and labile P, soil P fractionation, and P adsorption capacity were measured in the laboratory using 96 Florida sandy soil samples to evaluate the relationship between P release in water and soil P status. The sandy soils had a very low P adsorption capacity. The adsorption maximum, as calculated from the Langmuir equation, averaged 40.4 mg P kg(-1). More than 10% of the soil P was water soluble, indicating a high risk of P leaching from soil to water. Successive leaching using deionized water released, on average, 7.7% of total P (144.5 mg kg(-1)) in different soils, whereas labile P recovered by successive water extraction accounted for 39.2% of the total P. Variation in release potential among the different soils could be explained more by the difference in amounts of extractable P than the adsorption capacity. Total amounts of P released by successive leaching were significantly correlated with all labile P indices measured by different methods and all soil P fractions except for residual P. The correlation coefficients (r) were 0.97** for water-soluble P, 0.96** for 0.01 M CaCl2-P, 0.94** for Olsen P, 0.86** for Mehlich 1-P, 0.77*** for Mehlich 3-P, and 0.64*** for Bray 1-P. There were no obvious turning points in the relationships between Olsen-P, water-soluble P, or CaCl2-P and the amounts of P released from the sandy soils. The release of P from the sandy soils appeared to be controlled by a precipitation-dissolution reaction rather than a P sorption-desorption process. Furthermore, the sequential extraction of soils using deionized water indicated that P released was not limited to the labile P (H2O-P, NaHCO3-IP) and potentially labile P (NaOH-P) pools, but also from the HCl-P, indicating that all of P fractions except for residual P in the sandy soils can contribute to P release.

Clinical significance of hair cadmium content in the diagnosis of mental retardation of children

Cadmium (Cd) is known to be closely related to the development of children's intelligence. To investigate the clinical significance of the hair cadmium content in the diagnosis of mental retardation (MR), 415 normal and 85 MR children's hair cadmium contents were measured by 79-1 anodic stripping voltmeter. The data were processed by an Apple-II microcomputer. Comparing the median value and using the Chi-square test the Cd contents in the hair of both male and female MR children were obviously higher than those of normal children (P less than 0.001). If the Cd content in the hair of male children is higher than 0.239 microgram/g, and higher than 0.180 microgram/g in the female, MR can be diagnosed. The sensitivity and specificity of the test are greater than 90%; false positive and false negative rates are lower than 10%. Hair Cd can be used as an additional criterion in the diagnosis of MR and may be important in the screening for MR.