[Status of Heavy Metal in Organic Fertilizers in Main Tea Growing Regions of China].

To provide guidance for the safe use of organic fertilizers and improve soil quality and tea safety, it is necessary to conduct systematic analyses of the heavy metal content of organic fertilizers applied in the main tea producing areas of China. In this study, we analyzed the heavy metal contents in organic fertilizer samples collected from 2017 to 2019. The risks of collected organic fertilizers from different areas and sources were calculated. The results showed that the average concentrations of ω(As), ω(Hg), ω(Pb), ω(Cd), ω(Cr), ω(Cu), ω(Zn), and ω(Ni) in the collected organic fertilizers were 4.60, 0.22, 27.1, 0.78, 27.9, 58.3, 250.1, and 16.3 mg·kg-1, respectively. According to the assessment standard in NY/T 525- 2021, the over-limit rates of As, Hg, Pb, Cd, and Cr were 6.19%, 1.33%, 4.42%, 4.42%, and 1.33%, respectively. With respect to the area, the qualified rates were 100% in Shaanxi, Jiangsu, Anhui, Fujian, and Guangxi; 80%-90% in Shandong, Zhejiang, Hubei, Sichuan, Yunnan, and Guangdong; and only 54.5% in Jiangxi. The qualified rates of sources were 100% in rapeseed cake, soybean cake, and pig manure; 95.8% in sheep manure; 91.7% in cow manure; 90.7% in chicken manure; 87.2% in manure of other animals; 82.4% in the mixture of plant and animal sources; 65.2% in other plant sources; and 63.6% in other sources. According to the recommended application rate, the accumulation rate of heavy metals in soil with pig manure, cow manure, chicken manure, and sheep manure would be much higher than that with rapeseed cake and soybean cake. The average accumulation rate of organic fertilizer from animal sources was 7-30 times higher than that from plant sources. Therefore, it is recommended to use rapeseed cake or soybean cake fertilizer in tea plantation and to increase the supervision of heavy metal accumulation in soil and tea in those high-risk areas.

[Heavy Metal Contamination in Farmland Soils at an E-waste Disassembling Site in Qingyuan, Guangdong, South China].

Crude e-waste dismantling activities have caused a series of environmental pollution problems, and the pollutants released from the dismantling activities would finally pose high risks to human health by means of the accumulation through food chains. To explore the contamination status of heavy metals to the surrounding farmland soils in Longtang and Shijiao Town, Qingyuan, Guangdong, China, 22 farmland soil samples were collected and analyzed for the contents, spatial distributions and chemical forms of 6 heavy metals (Pb, Cu, Cd, Zn, Cr and Ni). The results showed that the 6 heavy metals exhibited obvious accumulations when compared to the corresponding background values in Guangdong Province. According to farmland environmental quality evaluation standard for edible agricultural products HJ 332-2006, the pollution severity of heavy metals was evaluated by monomial pollution index and Nemerow synthetic pollution index methods, the results indicated that 72. 7% of the soil samples contained one or more kinds of heavy metals with higher concentrations than the corresponding standard values, Cd, Cu, Pb and Zn were the main metals in the polluted soils, and for the proportion of contaminated soil samples in all the 22 samples, Cd was the highest, followed by Cu, and finally Pb and Zn. Nemerow synthetic pollution index further revealed that 68. 2% of soil samples were contaminated, and among them 53. 3% of samples were heavily contaminated. Most of the heavy metals were well correlated with each other at the 0. 05 or 0. 01 level, which indicated that primitive e-waste recycling activities were an important source of the heavy metal contamination in Longtang and Shijiao Town. The contents of Cd, Pb, Cu and Zn in surface soils were higher than those of other soil layers, and the contents of these 4 metals in deep soils (20- 100 cm) did not show significant decreases with the increasing depths. The contents of Cr and Ni maintained constant, and exhibited no statistical differences with the sampling depths. Sequential leaching tests showed that the active fractions of Pb, Cu and Cd ranged from 36. 9% to 90. 6%, 39. 6% to 93. 9% and 43. 7% to 99. 6%, with mean values of 61. 3% 65. 3% and 80. 7%, respectively. The active fractions of these three metals in most samples accounted for more than half of their own total contents, which would cause a high ecological risk.

Bioaccumulation characterization of cadmium by growing Bacillus cereus RC-1 and its mechanism.

In an effort to explore the protective mechanism of growing Bacillus cereus RC-1 against the toxicity of different Cd(II) concentrations, bacterial growth, cadmium consumption, surface interactions and intra- and extra-cellular Cd(II) contents were examined. Cellular morphology and growth were evidently affected by the initial metal concentrations above 20 mg L(-1), according to the analysis of SEM, AFM, TEM and UV spectrophotometer. Surface complexation and electrostatic attraction played an important role in the different Cd(II) concentrations, as determined by the FTIR and Zeta potential analysis. Intracellular accumulation was the predominant mechanism in culture with lower metal concentrations (below 20 mg L(-1)), but was overshadowed by extracellular adsorption at higher concentrations. This suggested that the growing cells might employ one dominant mechanism at lower concentrations and then shift to another at higher concentrations. These results suggest options could be exploited for bioremediation of aqueous solution in which the Cd(II) concentration is less than 20 mg L(-1).

[Dynamic adsorption of cadmium (II) in water on modified peanut shells].

Peanut shells modified by potassium permanganate were used as absorbents for cadmium (II) removal in a fixed bed. The effects of influencing parameters such as bed height (ranging between 30 and 50 cm), initial concentration (ranging between 0.55 and 11.00 mg x L (-1)) and influent flow rate (ranging between 15.11 and 37.00 mL x min(-1)) were studied and the corresponding breakthrough curves were obtained. This result indicated that the column packed with modified peanut shells had good adsorption properties for cadmium (II) removal. In the initial adsorption stage cadmium (II) outflow concentration was less than 0.001 mg x L(-1). According to different operating conditions the operation time reached 2-62 h and the removal rate was above 54%. The height of mass transfer zone was primarily driven by initial concentration and influent flow rate. The height of mass transfer zone kept substantially unchanged and the breakthrough time increased with the increase of bed height. The height of mass transfer zone increased and the breakthrough time decreased with the elevated initial concentration and influent flow rate. The bed depth service time (BDST) model was used to fit the experiment data resulting in a good effect with R2 > 0.99 under low concentration. The operation time can be accurately predicted using the BDST model.

[Investigation on mechanism of pyrite oxidation in acidic solutions].

The mechanism of pyrite oxidation in acidic solutions was investigated by electrochemical analysis methods, such as open-circuit potential, cyclic voltammetry, Tafel polarization curve and anodic polarization curve, using a pyrite-carbon paste electrode as working electrode. The results showed that the oxidation process of pyrite in acidic solutions was via a two-step reaction: the first step was the dissolution of iron moiety and formation of a passivation film composed of elemental sulphur, metal-deficient sulfide and polysulfide; the second step was the further oxidation of these intermediate products to SO4(2-). The final reaction products of pyrite oxidation were Fe3+ and SO4(2-) in acidic solutions. In addition, the open-circuit potential and corrosion potential were positively shifted, the peak current and the corrosion current were increased with the increase in concentration of H2SO4 solutions. This indicated that increased acidity of the system was advantageous to the oxidation of pyrite.

[Interrelationships of rhamnolipids, hydrophobic substrate and degrading bacteria].

The effect of rhamnolipids on pyrene degradation by Pseudomonas sp. GP3A was investigated to explore the interrelationships of biosurfactant, hydrophobic substrate and degrading bacteria. The cell surface hydrophobicity, lipopolysaccharide, hydrogen bond, bacterial biomass and pyrene degradation were determined. The results showed that the apparent solubility of pyrene was enhanced significantly when the concentration of rhamnolipids was higher than critical micelle concentration (CMC) of 60 mg x L(-1). Biosurfactant can increase the cell surface hydrophobicity by releasing the component of the cell wall-lipopolysaccharide; With the increase of cell surface hydrophobicity from 12% to 55%, bacterial biomass increased from 4.4 x 10(6) CFU x mL(-1) to 1.2 x 10(7) CFU x mL(-1), corresponding with the increase of pyrene degradation from 16% to 44%. Meanwhile, hydrogen bond was formed between biosurfactant and bacteria, which was beneficial to hydrophobic substrate degradation. The half-life of pyrene was shorten significantly. The average residual rate of pyrene in 10 days was 81% without rhamnolipids, but decreased to 57%, 41%, 33% and 26%, respectively with the addition of 20, 50, 200 and 500 mg x L(-1) of rhamnolipids.

The effects of nutrient amendment on biodegradation and cytochrome P450 activity of an n-alkane degrading strain of Burkholderia sp. GS3C.

The promotion of hexadecane biodegradation activity by an n-alkane degrading strain of Burkholderia cepacia (GS3C) with yeast extract amendment was studied using various carbon, nitrogen, vitamin, and amino acid amendments. Cytochrome P450 monooxygenase enzymes play a very important role and are especially required to introduce oxygen in n-alkane degradation. These enzymes from GS3C were located and detected using amino acid amendments. It was shown that biodegradation activity was promoted with amino acids amendments. However, only specific amino acids (L-phenylalanine, L-glutamic acid, L-proline, L-lysine, L-valine and L-leucine) have biodegradation promoting ability for GS3C. Cell protein concentration and cytochrome P450 activity were promoted significantly with the addition of L-phenylalanine and yeast extract. Furthermore, a significant positive linear relationship between cytochrome P450 activity and biodegradation efficiency of GS3C was observed. The results indicate that amino acid is the primary factor of nutrient amendment in promoting hexadecane biodegradation by influencing cytochrome P450 activity in GS3C.

[Effect of Cd on remediation of DDT contaminated soil using different laccase forms].

This study investigated the effect of Cd on remediation of DDT contaminated soil using free laccase and immobilized reversed micelles laccase. The results show: degradation rates of ingredients of DDT and total DDT reduced with increasing of Cd concentration, the higher percentage of components in total DDT, the greater impact of Cd on them. Degradation rates of different components were p, p'-DDT > p, p'-DDD > o,p'-DDT > p, p'-DDE. When Cd concentration was 0, 0.5, 1 and 2 mg x kg(-1), the responding degradation rates of DDTs were measured at 50.68%, 32.50%, 14.92% and 13.40%, respectively. Compared with free laccase, degradation rate of total DDT by immobilized reversed micelles laccase nearly increased by 20% in soil without Cd and 30% in soil with 0.5 mg x kg(-1) Cd, implying that immobilized reversed micelles laccase is more effective for DDT degradation than free laccase.

Modeling and prediction of photolysis half-lives of polycyclic aromatic hydrocarbons in aerosols by quantum chemical descriptors.

Quantitative structure-property relationship (QSPR) modeling is a powerful approach for predicting environmental fate parameters of organic pollutants with their structure descriptors. This study reports QSPR models for photolysis half-lives of polycyclic aromatic hydrocarbons (PAHs) in aerosols. Quantum chemical descriptors computed with density functional theory at B3LYP/6-31G(d) level and partial least squares (PLS) analysis with optimizing procedure were used for generating QSPR models. The correlation coefficient of the optimal model was 0.993, and the fitting results showed this optimal model had high fitting precision and good predictability. The predicted photolysis half-lives by the optimal model are very close to those observed. The PLS assistant analysis indicated that PAHs with large electronic spatial extent tend to be photolyzed faster, while PAHs with high molecular total energy and small Mulliken atomic charges on the most negative carbon atom tend to be photolyzed slower in aerosols.