[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.

MiRNA-15a-3p inhibits the metastasis of hepatocellular carcinoma by interacting with HMOX1.

OBJECTIVE: To uncover the relationship between microRNA-15a-3p (miRNA-15a-3p) level and clinical features of hepatocellular carcinoma (HCC), and to explore the influence of miRNA-15a-3p on metastasis of HCC cells. PATIENTS AND METHODS: HCC and paracancerous tissues were surgically resected from 44 HCC patients. Their clinical data and follow-up files were recorded. Differential expressions of miRNA-15a-3p in HCC samples were determined. The relationship between miRNA-15a-3p level and clinical features of HCC patients was analyzed. Changes in proliferative, migratory and invasive potentials in Huh7 and HepG2 cells overexpressing miRNA-15a-3p were examined. The downstream gene of miRNA-15a-3p and its involvement in HCC development were finally explored. RESULTS: MiRNA-15a-3p was downregulated in HCC tissues. High metastasis rate and poor prognosis were observed in HCC patients expressing a low level of miRNA-15a-3p. Overexpression of miRNA-15a-3p attenuated proliferative, migratory and invasive potentials in HCC. Protein levels of HMOX1, CD31, c-Myc, MMP-2 and MMP-9 were downregulated in HCC cells after overexpression of miRNA-15a-3p. HMOX1 was the downstream gene of miRNA-15a-3p, which was upregulated in HCC samples. Highly expressed HMOX1 was unfavorable to the prognosis in HCC. Overexpression of HMOX1 abolished the regulatory effects of miRNA-15a-3p on HCC cell phenotypes. CONCLUSIONS: MiRNA-15a-3p is closely linked to lymphatic metastasis, distant metastasis and poor prognosis in HCC. It inhibits the malignant development of HCC by interacting with HMOX1.

[Implication of BRAF V600E and CTNNB1 gene mutations in the pathological classification of craniopharyngioma].

Objective: To investigate the clinicopathological significance of BRAF V600E and CTNNB1 gene mutations in adamantinomatous craniopharyngiomas (ACP) and papillary craniopharyngiomas (PCP). Methods: The retrospective study included a total of 67 craniopharyngiomas diagnosed from October 2009 to August 2018 at Xuanwu Hospital, Capital Medical University. The immunohistochemical staining for ß-catenin and BRAF V600E expression, Sanger sequencing of exon 3 of CTNNB1, BRAF mutation analysis by scorpions amplification refractory mutation system (ARMS) fluorescence quantitative PCR were performed. Univariate survival analysis was used to correlate with tumor recurrence. Results: Of the 67 patients, 53 were ACPs and 14 were PCPs. Four patients underwent multiple operations and one of them presented with malignant transformation into squamous cell carcinoma. Histologically, ACPs were characterized by whorl-like cell clusters, peripheral palisaded layer, stellate reticulum, finger-shaped protrusions, ghost cells and wet keratinous substances. While PCPs usually consisted of mature squamous epithelium associated with fibrovascular stroma resulting in papillary appearance. The nuclear immunopositivity for ß-catenin was observed in 73.6% (39/53) of ACPs, and it was absent in PCPs (0/14). The nuclear translocation of ß-catenin usually presented at whorl-like structures or around ghost cells. Of all the cases, mutations analysis in exon 3 of ß-catenin gene CTNNB1 were successful in 46 cases and 42.1% (16/38) of ACP showed CTNNB1 gene mutation, while none of the PCPs harbored CTNNB1 gene mutation (0/8). The cytoplasmic immunopositivity for BRAF V600E mutant protein was found in all PCPs (14/14) and negative in all ACPs (0/53). ARMS-PCR results showed that BRAF V600E mutations were observed in 13/14 of PCPs but not seen in ACPs (0/53). Follow-up data were available in 35 patients with duration of 2 to 120 months. Ten patients experienced recurrences after the first surgery. Upon univariate survival analysis, only subtotal excision was found to be associated with increased recurrence (P=0.032), while pathological type, postoperative radiotherapy and CTNNB1 gene mutation were not (P>0.05). Conclusions: There is significant difference in the expression of BRAF V600E and CTNNB1 genes between ACP and PCP, and their immunohistochemical and molecular detection therefore can be used in the diagnosis and differential diagnoses of craniopharyngiomas.

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.

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.

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.

Relevance and clinical significance of serum resistin level in obese T2DM rhesus monkey models.

Resistin is a type of hormone-like adipocytokines, which is secreted specifically by adipocytes. It may be a key factor in the development of type 2 diabetes mellitus (T2DM) from obesity- associated insulin resistance due to results that show that it has a close relationship with insulin resistance in rodents. We utilized the rhesus monkeys as study objects to preliminarily test the association with glucose metabolism and to conduct a correlation analysis for clinical parameters and serum resistin levels in obese rhesus monkey models of T2DM. The results suggested that resistin was significantly increased in T2DM monkeys (P <0.01), and that resistin had a positive correlation respectively with total cholesterol (TC), low-density lipoprotein (LDL-C), fasting plasma glucose (FPG), fasting insulin (FPI) and glycated hemoglobin (HbA1c), Insulin resistance index (HOA-IR), but a negative correlation with islet ß-cell function (HOMA-ß). In the course of glucose metabolism, reverse release change of resistin and insulin in T2DM monkeys occurred, but the phenomenon that was not observed in the control group, these findings indicated that resistin negatively regulated and interfered with carbohydrate metabolism in T2DM monkey models. The character of the releasing change of resistin might be a unique process in T2DM. Therefore, all of the results could provide references for clinical diagnostic criteria for human cases of T2DM, and could have clinical significance for obese T2DM diagnosis and degree of insulin resistance.

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.

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.

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.

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.

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.

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.

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.