Evaluation of the effectiveness of ex-situ stabilization for arsenic and antimony contaminated soil: Short-term and long-term leaching characteristics.

Ex-situ stabilization for As and Sb co-contaminated soil was conducted through an iron-based stabilizer, PFSC (a mixture of polymerized ferric sulfate (PFS) and hydrated lime (Ca(OH2)) with a dry mass ratio of 2:1). After field aging for one week, the stabilized contaminated soil was subjected to a horizontal vibration leaching test (HJ 557), Wenzel's sequential extraction, and a semi-dynamic leaching test (ANS 16.1). By assessing the cumulative fractions of As and Sb, the observed diffusion coefficients (Dobs) and leachability indices (LX) of metalloids released from the soil specimens were calculated. The PFSC ex-situ stabilization was effective to immobilize metalloids, and the As and Sb leached concentrations of stabilized contaminated soil samples were lower than remediation targets. Nonspecifically bound As and Sb in the stabilized contaminated soil samples decreased from 4.5 - 9.2 % to 1.5-2.5 % and from 2.2 - 5.8 % to 1.1-1.5 %, respectively. The mechanisms controlling the leaching behaviors of As and Sb included wash-off and diffusion and they were changed with the leaching interval. The mean Dobs of As and Sb released from stabilized contaminated soil specimen were 3.46 × 10-12 and 2.99 × 10-13 cm2 s-1, in the which were two orders of magnitude lower than that of untreated contaminated soil specimen. The mean LX of stabilized contaminated soil specimen for As and Sb releases were 11.40 and 12.83, respectively, indicating that the stabilized contaminated soil was acceptable for "controlled utilization".

[Gene Detection Analysis of Thalassemia in 2 494 Cases of Childbearing Couples in Haikou City].

OBJECTIVE: To observe the genotypes and composition ratio of thalassemia in couples of reproductive age, and provide a reference for the prevention and control of thalassemia in Haikou. METHODS: Gene diagnosis was performed in 2 494 subjects who were screened for thalassemia before marriage or prenatal by cross-breakpoint PCR, PCR-reverse dot hybridization, and PCR-electrophoresis. RESULTS: A total of 1 037 thalassemia gene carriers were detected in 2 494 samples, with a detection rate of 41.57%, of which 75.02% was α-thalassemia, 18.61% was ß-thalassemia, and 6.36% was α-ß complex thalassemia. There were 778 cases of α-thalassemia, mainly of deletion type, accounting for 76.99% (599/778). Twenty genotypes were detected, the highest three was --SEA/αα (33.42%, 260/778), -α3.7/αα(23.91%, 186/778), and -α4.2/αα(19.02%, 148/778), respectively. A rare HKαα/-α3.7 was detected, who immigrated from other province. There were 193 cases of ß-thalassemia, all of them were light (ß0/ßA or ß+/ßA). Eight genotypes were detected, the highest two was 41-42M/N (74.61%, 144/193) and 654M/N (10.36%, 20/193), respectively. There were 66 cases of α-ß compound type of thalassemia, 15 genotypes were detected, the highest three was ααWS/αα complex 41-42M/N (28.79%, 19/66), -α3.7/αα complex 41-42M/N, and -α4.2/αα complex 41-42M/N (16.67%, 11/66 for both). CONCLUSION: In Haikou city, the gene carrying rate of thalassemia is very high, and the genotype distribution is different from other cities in Hainan Province, attention should be paid to the impact of population inflow on the frequency spectrum change of local thalassemia gene.

Review of the risk factors for SARS-CoV-2 transmission.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, which has lasted for nearly a year, has made people deeply aware of the strong transmissibility and pathogenicity of SARS-CoV-2 since its outbreak in December 2019. By December 2020, SARS-CoV-2 had infected over 65 million people globally, resulting in more than 1 million deaths. At present, the exact animal origin of SARS-CoV-2 remains unclear and antiviral vaccines are now undergoing clinical trials. Although the social order of human life is gradually returning to normal, new confirmed cases continue to appear worldwide, and the majority of cases are sporadic due to environmental factors and lax self-protective consciousness. This article provides the latest understanding of the epidemiology and risk factors of nosocomial and community transmission of SARS-CoV-2, as well as strategies to diminish the risk of transmission. We believe that our review will help the public correctly understand and cope with SARS-CoV-2.

Geoenvironmental properties of industrially contaminated site soil solidified/stabilized with a sustainable by-product-based binder.

This paper presents a study on utilizing a novel BCP binder, basic oxygen furnace slag (BOFS) activated with mixed calcium carbide residue (CCR) and phosphogypsum (PG), to solidify/stabilize heavy metals in industrial contaminated site soil. The effects of curing time and binder dosage on the geoenvironmental properties of the solidified/stabilized soil including soil pH, electrical conductivity, unconfined compressive strength, and leachability were tested and discussed. Chemical speciation of target heavy metals, pore-size distribution of treated soil, and phase identification of reaction products were analyzed to understand the mechanisms leading to the change of geoenvironmental properties. The results demonstrated that the addition of the BCP binder yielded remarkable increase in soil pH, unconfined compressive strength, and relative binding intensity index (IR) of target heavy metals including nickel (Ni) and zinc (Zn), while significantly decreased the electrical conductivity and leachability of contaminated soil. The IR value of heavy metals had a good linear relationship with the leached concentrations on a semi-logarithmic scale. The formation of heavy metal-bearing precipitates, absorptivity of calcium silicate hydrate (C-S-H), heavy metals encapsulation by C-S-H, and ion-exchange of heavy metals with ettringite (AFt) contributed to the immobilization of heavy metals in the solidified/stabilized soil.

In-situ solidification/stabilization of heavy metals contaminated site soil using a dry jet mixing method and new hydroxyapatite based binder.

In this study, in-situ treatment using dry jet mixing construction method and SPC (single superphosphate and calcium oxide) new binder are used to solidify/stabilize a heavy metal contaminated site soil with relatively high content of organic matters. Time-dependent field performance of the soils at 41 and 326 days after treatment is evaluated, which includes electrical conductivity (EC), leachability of heavy metals and chemical oxygen demand (COD), soil penetration resistance, acid neutralization capacity (ANC), and chemical speciation of heavy metals. The results indicate that the stabilized soils exhibit satisfactory performance which is comparable with the laboratory study. In-situ SPC treatment significantly decreases EC values and increases penetration resistance values of the soils. Leachability of lead, zinc, cadmium and COD decreases with increasing SPC content or curing time. Large percentages of heave metals in the soils are transformed from exchangeable fractions to residual fractions after treatment. These, coupled with the improved ANC, result in low heavy metal leachability in stabilized soils.