Work Resumption Rate and Migrant Workers' Income During the COVID-19 Pandemic.

The COVID-19 public health crisis has quickly led to an economic crisis, impacting many people and businesses in the world. This study examines how the pandemic affects workforces and workers' income. We quantify the impact of staggered resumption of work, after the coronavirus lockdowns, on the migrant workers' income. Using data on population movements of 366 Chinese cities at the daily level from the Baidu Maps-Migration Big Data Platform and historical data on the average monthly income of migrant workers, we find that the average work resumption rate (WRR) during the period of the Chinese Lantern Festival was 25.25%, which was only 30.67% of that in the same matched lunar calendar period in 2019. We then apply Gray Model First Order One Variable [GM (1, 1)] to predict the monthly income of migrant workers during the period of the COVID-19 pandemic. We show that, if without the influence of the COVID-19 pandemic, the average monthly income of migrant workers in 2020 will be expected to increase by 12% compared with 2019. We further conduct scenario analysis and show that the average monthly income of migrant workers in 2020 under the conservative scenario (COS), medium scenario (MES), and worse scenario (WOS) will be predicted to decrease by 2, 21, and 44%, respectively. Through testing, our prediction error is <5%. Our findings will help policymakers to decide when and how they implement a plan to ease the coronavirus lockdown and related financial support policies.

The speciation, transformation kinetics and fate of spiked Pu (IV) in highly saline groundwater.

The mobility of plutonium (Pu) in groundwater is dependent of its speciation distribution and transformation. The speciation and transformation kinetics of Pu(IV) and its colloids in highly saline groundwater have, however, been rarely studied. In the present study, groundwater (Ionic strength 1 M) from Dunhuang region, NW China, was collected for investigating the speciation, transformation kinetics and fate of spiked Pu (IV) with aging time. The results showed that ~99% of the spiked Pu (IV) (over initial concentration c0 range 2.5 × 10-10-7.8 × 10-7 mol·L-1) was easily associated with the natural colloids and transformed into relatively unstable Pu pseudo-colloids in 1 day, which then gradually deposited and/or adsorbed on the container walls with aging. The suspended Pu pseudo-colloids decreased in similar exponential models, with rate equations r(t) = -3.1 × 10-10e- t/4 and -1.3 × 10-8e-/3 for c0 = 1.25 × 10-9 mol·L-1and 4.17 × 10-8 mol·L-1, respectively. The chemical speciation of the suspended colloidal Pu was dominated by "Fe/Mn Oxides" at the early time, while "Carbonates" with slower depositing rate (r(t) = -6.9 × 10-12e- 0.149t) dominated it (~82%) at equilibrium state. Whatever the c0 was, the concentration of dissolved Pu (i.e., the apparent solubility of Pu) kept at 0.7 × 10-11 mol·L-1 over aging. The valence of dissolved Pu was dominated by Pu(IV) at early time, while Pu(V + VI) would become dominant (~95%) at equilibrium state with transformation rate of r(t) = -92.9e- t/16.6 + 96.9. The equilibrium times of Pu deposition (and/or adsorption), speciation transformation of the suspended colloidal Pu, and valence change of the dissolved Pu were 30 d, 80 d and 120 d, respectively. The kinetic process for each Pu species could be well fitted with exponential model. These results suggest that the majority of released Pu(IV) into highly saline groundwater will be easily associated with natural aquatic colloids and then become immobile in short time due to deposition (and/or adsorption) onto the environmental medium, but potential migration risk caused by stable suspended Pu colloids cannot be ignored.

Free-radical-promoted conversion of graphite oxide into chemically modified graphene.

The preparation of chemically modified graphene (CMG) generally involves the reduction of graphite oxide (GO) by using various reducing reagents. Herein, we report a free-radical-promoted synthesis of CMG, which does not require any conventional reductant. We demonstrated that the phenyl free radical can efficiently promote the conversion of GO into CMG under mild conditions and produces phenyl-functionalized CMG. This pseudo-"reduction" process is attributed to a free-radical-mediated elimination of the surface-attached oxygen-containing functionalities. This work illustrates a new strategy for preparing CMG that is alternative to the conventional means of chemical reduction. Furthermore, the phenyl-functionalized graphene shows an excellent performance as an electrode material for lithium-battery applications.

Photoactive graphene sheets prepared by "click" chemistry.

Graphene sheets modified by phenylacetylene moieties provide a facile platform for attaching various photoactive functional molecules via"click" chemistry. The produced photoactive graphene materials are well-dispersed in various solvents and show dramatically improved photo-current responses.