Comprehensive and cumulative risk evaluation of dietary exposure to aflatoxins and ochratoxin A on fermented teas worldwide by a new assessment model.

Recently, mycotoxin risks in fermented tea have received high attention, but mycotoxin transfer rates from tealeaf to infusion during brewing were rarely considered. In addition, the assessment data (i.e., mycotoxin occurrences and tea consumption) in previous assessments were usually limited. Here, a comprehensive and cumulative risk assessment of aflatoxins and ochratoxin A was performed using a tea assessment model, by which mycotoxin transfer rates were included and the assessment data were collected worldwide. By 10 times of brewing, the aflatoxin transfer rate was only 2.94% and OTA was 63.65%. Besides the extreme case, hazard quotients (HQs) from all consumers were lower than the threshold of 1.0, indicating no noncarcinogenic risk; the P95 cumulative margin of exposure (1/MoET) values were 2.52E-04 (30-39 years of age) and 2.42E-04 (≥50 years of age) for two high exposure groups under the upper bound scenario, which a little higher than the carcinogenic risk threshold of 1.00E-04. Notably, the P95 cumulative 1/MoET values (3.24E-03 -7.95E-03) by food assessment model were ten times higher than those of by tea assessment model. The comparative results showed that mycotoxin dietary risks on tea consumption by food assessment model were much overestimated. The result of this study indicated that the contaminants transfer rates should be considered for risk assessment on tea consumption in future work.

Determination of four aflatoxins on dark tea infusions and aflatoxin transfers evaluation during tea brewing.

In daily tea drinking, little is known on aflatoxin transfers from tea-leaf to infusion during brewing and the actual intake. A verified aflatoxins analytical method on tea infusion is significant to the exposure assessment. Here, an optimal method 3 (M3) was screened and validated on four aflatoxins (B1, B2, G1 and G2) simultaneous determination. Recoveries of AFG1 and AFB1 were 87.37 %±1.99 %-102.03 %±8.62 %, and AFG2 and AFB2 were 83.99 %±8.65 %-100.14 %±1.69 %. The correlation coefficient on the fortified samples determination was > 0.99 for each aflatoxin. In accuracy and precision validation, aflatoxins recoveries in high and low fortified samples were 85.94 %-103.83 %, and RSDs were 2.20 %-9.15 %. Method applicability test showed that the M3 was qualified for six different dark tea types. Extraction rate of 30-days stored AFB1 fortified tea-leaf by acetonitrile-water (84:16, v/v) was < 50 %; meanwhile, only 2.94 % spiked AFB1 was released by ten times tea brewing which indicated that Puerh tea have strong adsorbability to aflatoxin.

Insights into enhanced removal of Cd2+ from aqueous solutions by attapulgite supported sulfide-modified nanoscale zero-valent iron.

The sulfidation of nanoscale zerovalent iron (nZVI) has received increasing attention for reducing the oxidizability of nZVI and improving its reactivity toward heavy metal ions. Here, a sulfide (S)-modified attapulgite (ATP)-supported nanoscale nZVI composite (S-nZVI@ATP) was rapidly synthesized under acidic conditions and used to alleviate Cd2+ toxicity from an aqueous solution. The degree of oxidation of S-nZVI@ATP was less than that of nZVI@ATP, indicating that the sulfide modification significantly reduced the oxidation of nZVI. The optimal loading ratio was at an S-to-Fe molar ratio of 0.75, and the adsorption performance of S-nZVI@ATP for Cd2+ was significantly improved compared with that of nZVI@ATP. The removal of Cd2+ by S-nZVI@ATP was 100% when the adsorbent addition was 1 g/L, the solution was 30 mL, and the adsorption was performed at 25 °C for 24 h with an initial Cd2+ concentration of 100 mg/L. Kinetics studies showed that the adsorption process of Cd followed the pseudo-second-order model, indicating that chemisorption was the dominant adsorption mechanism. The adsorption of Cd2+ by S-nZVI @ATP is dominated by the complexation between the iron oxide or iron hydroxide shell of S-nZVI and Cd2+ and the formation of Cd(OH)2 and CdS precipitates.

Study on Mechanical Properties of Permeable Polymer Treated Loess.

The reinforcement and durability of loess are of great importance for road performance. In this study, a self-designed grouting system and newly permeable polymers were adopted to investigate the mechanical properties and durability of solidified loess (SL), considering different dry densities and water contents. The unconfined compression test and piezocone penetration (CPTU) test were used to examine the mechanical properties. The mechanism of the loess solidified by permeable polymer was analyzed from the micro-level by SEM, MIP, and XRD tests. The test results show that the effect of polymer grouting is obvious, the unconfined compressive strength (UCS) of the SL after grouting is as high as 3.05−5.42 MPa; it is 11.83−20.99 times that of unsolidified loess (UL). The UCS of the SL after grouting is inversely proportional to the dry densities and water contents. After 56 days of immersion, the SL still shows a high compressive strength. The additional erosion of the SL was not caused by the salt solution; the durability is significantly better than that of cement mixing soil. The sensitivity of various factors on the UCS of the SL are service environment > water content > dry density. The SEM tests clearly show that the gel formed by the reaction of the polymer with water on the surface of soil particles makes the bond of soil particles tighter. It can be observed from the MIP test that the cumulative mercury of SL was 0.115 mL/g, which was 33.72% of UL (0.341 mL/g), and the cumulative mercury of SL after immersion in water and salt solutions was 0.183 mL/g and 0.175 mL/g, which was 53.7% and 51.3% of UL (0.341 mL/g), respectively. The XRD results show that there are no other new mineral components produced after grouting and the spacing between crystalline planes decreases, which proves that permeable polymer grouting makes the soil denser and does not erode the soil particles.

Mechanism-Enhanced Active Attapulgite-Supported Nanoscale Zero-Valent Iron for Efficient Removal of Pb2+ from Aqueous Solution.

In this study, attapulgite-supported nano zero-valent iron (nZVI@ATP) was synthesized by a liquid-phase reduction method using active attapulgite (ATP) as raw material, and used for Pb2+ remediation in aqueous solution. To understand the mechanism of Pb2+ removal, various techniques were used to characterize nZVI@ATP. The results showed that spherical nZVI particles were uniformly dispersed on the surface of ATP, and the agglomeration of nZVI particles was significantly weakened. The adsorption performance of nZVI@ATP for Pb2+ was greatly improved compared with that of ATP ore, in which the Fe/ATP mass ratio of 1:2 was the best loading ratio. Under the conditions of a temperature of 25 °C and a pH of 5.00, the initial concentration of Pb2+ was 700 mg/L, and the Pb2+ removal rate of nZVI@ATP was 84.47%. The adsorption of nZVI@ATP to Pb2+ was mainly a spontaneous endothermic reaction of heterogeneous surfaces, and the adsorption rate of nZVI@ATP to Pb2+ was proportional to pH in the range of 2-5.5. The presence of Na+, Mg2+, and Ca2+ can inhibit the removal of Pb2+, and Ca2+ has the strongest inhibition effect on the removal of Pb2+. The removal mechanism of Pb2+ by nZVI@ATP obtained from SEM-EDS, BET, XRD, FTIR and XPS included reduction, precipitation, and the formation of complexes.