Migration and emission characteristics of metal pollutants in fluid catalytic cracking (FCC) process

Fluid catalytic cracking (FCC) is the core unit for heavy oil conversion in refineries. In the FCC process, the metal contaminants from the feedstock are deposited on the catalysts, causing catalyst deactivation and metal particulate matter (PM) emission. However, the migration and emission characteristics of metal pollutants in FCC units are still unclear. Here, the stack tests of three FCC units were carried out to monitor metal PM emissions, and the metal contents of the feedstock oil and spent catalyst were detected. For the metal migration from the feedstock to the catalysts, Ni, Fe, and V have high concentrations and migration rates while other metals perform much lower. The metal distribution on the spent catalysts profoundly determines the metal mobility to the flue gas and the regeneration process affects the catalyst attrition, leading to metal PM emissions discrepancy. The migration rate and emission concentration of V in the deeper layers of the catalysts are much lower than those of Ni at the particle's exterior. Finally, the stack data was used to calculate the emission factors and ratio factors of the metal PM. This work is expected to advance metal migration cognition and metal pollutants emissions estimation in FCC units.

Lacustrine plastisphere: Distinct succession and assembly processes of prokaryotic and eukaryotic communities and role of site, time, and polymer types

Microplastics as a carrier can promote microbial diffusion, potentially influencing the ecological functions of microbial communities in aquatic environments. However, our understanding of the assembly mechanism of microbial communities on different microplastic polymers in freshwater lakes during succession is still insufficient, especially for the eukaryotes. Here, the colonization time, site, and polymer types of microplastics were comprehensively considered to investigate the composition and assembly of prokaryotic and eukaryotic communities and their driving factors during the lacustrine plastisphere formation. Results showed that the particle-associated microorganisms in water were the main source of the plastisphere prokaryotes, while the free-living microorganisms in water mainly accounted for the plastisphere eukaryotes. The response of prokaryotic communities to different microplastic polymers was stronger than eukaryotic communities. The assembly of plastisphere prokaryotic communities was dominated by homogenizing processes (mainly homogenous selection), while the assembly of eukaryotic communities was dominated by differentiating processes (mainly dispersal limitation). Colonization time was an important factor affecting the composition of prokaryotic and eukaryotic communities during the formation of the plastisphere. The Chao1 richness of prokaryotic communities in the plastisphere increased with the increase of colonization time, whereas the opposite was true in eukaryotic communities. This differential response of species diversity and composition of prokaryotic and eukaryotic communities in the plastisphere during dynamic succession could lead to their distinct assembly processes. Overall, the results suggest that distinct assembly of microbial communities in the plastisphere may depend more on specific microbial sub-communities and colonization time than polymer types and colonization site.

Occurrence and potential release of heavy metals in female underwear manufactured in China: Implication for women's health

Underwear is a potential source of women's exposure to heavy metals owing to its direct contact with the skin, especially the skin of the vagina and vulva, which has a strong absorptive capacity. However, information regarding the prevalence of metals in female underwear, and its potential hazards, remains scarce. In the present study, we examined the concentrations and potential release of Cr, Co, Ni, Cu, As, Cd, Sb, and Pb in brassieres and briefs manufactured in China. We detected higher levels of Pb and moderate levels of other metals, relative to the metal levels reported for other textiles in the literature. Cu, As, Ni and Cd, had higher migration rates (MRs) from the underwear, with medians of 100%, 100%, 30.1%, and 20.7%, respectively. The median MRs of the other metals were in the range 1.07%-15.7%. On the whole, the total and extractable concentrations of these metals differed by item and fabric type. The pollution of raw materials and the use of chemical additives containing metals commonly contributed to the metals in the underwear. On the basis of the exposure estimation, the non-carcinogenic risks posed by the underwear metals were acceptable, but the carcinogenic risks from the metals in 5.18% of brassiere samples exceeded the acceptable level.

Distribution of trace metals in a soil-tea leaves-tea infusion system: characteristics, translocation and health risk assessment

The effects of metal pollution on tea are of great concern to consumers. We apply Geographic information systems technology to study the distribution of heavy metal elements in tea plantation ecosystems in Jiangsu Province, explore the relationships among metals in the soil, tea leaves and tea infusions, and assess the human safety risks of metals. The concentrations of nine metals in a soil-tea leaves-tea infusion system were studied at 100 randomly selected tea plantations in Jiangsu Province, China. Concentrations of selected metals, zinc (Zn), nickel (Ni), manganese (Mn), chromium (Cr) and copper (Cu), were quantified using an inductively coupled plasma-optical emission spectrometer (ICP-OES), and cadmium (Cd), arsenic (As), plumbum (Pb) and mercury (Hg) were quantified using inductively coupled plasma-mass spectrometry (ICP-MS). Arc-Map 10.3 was used for the spatial analysis of metals in soil, tea leaves and tea infusions. We found that the contents of Mn, Ni and Zn are high level in soil, tea leaves and tea infusions. The Mn level showed a spatial distribution pattern with greater concentrations at the junction of Nanjing and Yangzhou, southwest of Changzhou and west of Suzhou. The hazard index (HI) values in north-central Nanjing, southern Suzhou, southwestern Changzhou and northern Lianyungang were relatively greater. The Zn, Ni, Mn, Cr and Cu levels in the soil-tea infusion system were 17.3, 45.5, 54.5, 1.5 and 14.3%, respectively. The order of the leaching rates of the elements was Ni > Cr > Zn > Mn > Cu. The relative contribution ratios of HI were in the order of Mn > Ni > Cu > Zn > Cr > Pb > Cd > As > Hg. In tea infusions, the Mn level has the greatest potential health risks to consumers. Moreover, using C_soil it was inferred that the safety thresholds of Zn, Ni, Mn, Cr and Cu in soil were 27,700, 50, 1230, 493,000 and 16,800 mg L^-1, respectively. The content of heavy metals in soil and tea varies greatly in different regions of Jiangsu Province, 92% of the soil has heavy metal content that meets the requirements of pollution-free tea gardens, 91% of tea samples met the requirements of green food tea. The thresholds for Ni (50 mg L^-1) and Mn (1230 mg L^-1) can be used as maximum limits in tea plantation soils. The consumption of tea infusions did not pose metal-related risks to human health.

Comparative analysis of lead content during food processing

Heavy metals in groups 3-16 in periods 4 and greater. They exist naturally in the earth's crust. People are exposed to heavy metals by the inhalation of polluted air and via the intake of contaminated food. People are exposed to lead (Pb), one of heavy metals, by consuming foods that are contaminated from the environment. Pb is ubiquitous in the environment and accumulates in plants and animals that eat contaminated plants. The Pb in foods before and after processing were analyzed via Inductively coupled plasma with mass spectrometry to determine the effects of the procedures on the Pb migration and residue. This analytical method was verified to have a limit of detection of 0.011-0.859 µg/kg, acceptable linearity with the regression coefficient of 0.999, relative recoveries of 78.1-89.9% and repeatability of 1.4-7.7%. The amount of Pb was reduced during the following processes: more than 79.6% by extracting ginseng, extracting red ginseng and balloon flower roots via alcohol, more than 47.9% by blanching Chwinamul, more than 18.2% by brewing coffee with cold and hot water, more than 22.2% by extracting juices from fruits and peeling fruits. Therefore, proper cooking and food processing can be advantageous in terms of reducing exposure to Pb.

Computational modeling of human bone fracture healing affected by different conditions of initial healing stage

Background

Bone healing process includes four phases: inflammatory response, soft callus formation, hard callus development, and remodeling. Mechanobiological models have been used to investigate the role of various mechanical and biological factors on bone healing. However, the effects of initial healing phase, which includes the inflammatory stage, the granulation tissue formation, and the initial callus formation during the first few days post-fracture, are generally neglected in such studies.

Methods

In this study, we developed a finite-element-based model to simulate different levels of diffusion coefficient for mesenchymal stem cell (MSC) migration, Young’s modulus of granulation tissue, callus thickness and interfragmentary gap size to understand the modulatory effects of these initial phase parameters on bone healing.

Results

The results quantified how faster MSC migration, stiffer granulation tissue, thicker callus, and smaller interfragmentary gap enhanced healing to some extent. However, after a certain threshold, a state of saturation was reached for MSC migration rate, granulation tissue stiffness, and callus thickness. Therefore, a parametric study was performed to verify that the callus formed at the initial phase, in agreement with experimental observations, has an ideal range of geometry and material properties to have the most efficient healing time.

Conclusions

Findings from this paper quantified the effects of the initial healing phase on healing outcome to better understand the biological and mechanobiological mechanisms and their utilization in the design and optimization of treatment strategies. It is also demonstrated through a simulation that for fractures, where bone segments are in close proximity, callus development is not required. This finding is consistent with the concepts of primary and secondary bone healing.

Feasibility and oncological safety of sentinel node biopsy in breast cancer patients with a local recurrence

OBJECTIVES

To investigate the role and feasibility of sentinel lymph node biopsy (SLNB) in breast cancer patients with a local recurrence and no clinically positive axillary lymph nodes.

MATERIALS AND METHODS

A total of 71 patients underwent SLNB for breast cancer recurrence. At first surgery, they had received SLNB (46.5%), axillary lymph node dissection (ALND) (36.6%) or no axillary surgery (16.9%).

RESULTS

Lymphatic migration was successful in 53 out of 71 patients (74.6%) and was significantly higher in patients with previous SLNB or no axillary surgery than in those with previous ALND (87.9% vs. 53.8%; p = 0.009). Aberrant lymphatic migration pathways were observed in 7 patients (13.2%). The surgical SLNB was successfully performed in 51 patients (71.8%). In 46 patients (90.2%) the SLN was histologically negative, in 3 patients (5.9%) micrometastastatic and in 2 patients (3.9%) macrometastatic. The 2 patients with a macrometastates in SLN underwent ALND, In 4 out of the 18 patients with failure of tracer migration ALND, performed as surgeon's choice, did not find any metastatic node. After a median follow-up period of 39 months (range: 2-182 months), no axillary recurrence has been diagnosed.

CONCLUSION

A SLNB in patients with locally recurrent breast cancer, no previous ALND and negative axillary lymph nodes is technically feasible and impacts on the ALND rate. In patients who at primary surgery received ALND, migration rate is significantly lower, aberrant migration is frequent and no clinically useful information has been obtained.

Population connectivity and larval dispersal of the exploited mangrove crab Ucides cordatus along the Brazilian coast

BACKGROUND

The mangrove crab Ucides cordatus is considered a key species for the ecological balance of mangrove forests and a major source of employment and income for traditional crab collectors in Brazil. Several studies evidenced weak genetic variation among populations due to an efficient larval transport. However, gene flow patterns of the species is poorly understood, with no information about migration rates. The influence of the two main Brazilian currents in larval dispersion is also not clear. In order to provide baseline information for conservation, planning and management of this important fishery resource, the present study aimed to estimate and evaluate spatial distribution of genetic diversity, migration rates and gene flow directivity among populations of U. cordatus in Brazil.

METHODS

Nine microsatellites were used to resolve population structure of 319 crabs collected from six sites located along the Brazilian coast. The degree of geographical differentiation included estimates of genetic diversity, population structure and gene flow models, with spatial analysis of shared alleles (SAShA), isolation by distance tests, AMOVA, discriminant analysis of principal components (DAPC) and Bayesian clustering. We estimated the amount of ongoing gene flow between clusters using the coalescent-based method implemented in Migrate-N.

RESULTS

Loci were highly polymorphic (average of 12.4 alleles per locus) evidencing high genetic variability. There was significant differentiation among localities, despite of the low value of FST (= 0.019; P < 0.001). FST and Jost's D indexes were also estimated in pairwise comparisons and showed significant differences between most of the surveyed site pairs (P < 0.05). Structure evidenced a single genetic group among samples, however SAShA pointed to a non-panmictic condition (P = 0.011). AMOVA detected four statistical significant clusters with low level of differentiation (FCT = 0.037; P = 0.023). The gene flow model that best described the population connectivity was the island model, with ∼24 crabs being exchanged among localities per generation.

DISCUSSION

The high migration rates found among localities seem to be the main force acting to sustain the distribution of the genetic diversity of U. cordatus. Despite the high gene flow and the weak population structure among samples, the significant genetic differences found suggest that gene flow alone does not bypass the effects of genetic drift, natural selection and/or human exploitation. These findings are vital for the establishment of a database to be used in the development of conservation programs.

Downward migration of radiocesium in an abandoned paddy soil after the Fukushima Dai-ichi Nuclear Power Plant accident

After the Fukushima Dai-ichi Nuclear Power Plant accident on March 2011, continuous monitoring of the detailed vertical distribution of radiocesium in soil is required to evaluate the fate of radiocesium and establish strategies for remediation and management of the contaminated land. It is especially important to investigate paddy soil because little knowledge has been accumulated for paddy soil and wetland rice is a major staple in Japan. Therefore, we monitored the vertical distribution of ¹³⁷Cs in abandoned paddy soil in a planned evacuation zone from June 2011 to March 2016. The decontamination works (i.e., 5 cm of surface soil removal and re-covering with uncontaminated soil) were conducted by the government in 2015. As a result of monitoring, the ¹³⁷Cs gradually migrated downward with time and the ¹³⁷Cs concentration in the 0-10 cm soil was almost homogenous in October 2014, although it was non-cultivated. The liner relationship was obtained between the median depth, which is the thickness of a soil layer containing half of the total ¹³⁷Cs inventory, and the time after the accident, indicating the migration rate was constant (1.3 cm y^-1) before the decontamination works. After the decontamination works, the ¹³⁷Cs concentration in the uppermost surface layer was reduced by 90%, however the total ¹³⁷Cs inventory was reduced by only 50-70%. It was shown that the efficiency of ¹³⁷Cs removal by the decontamination works decrease linearly over time in fields like the studied paddy, in which the homogenization of ¹³⁷Cs concentration occurred. Conversely, the downward migration of ¹³⁷Cs to subsurface layers deeper than 10 cm (i.e., plowpan layer) with low permeability rarely occurred. It is expected that these unique trends in distribution and migration of ¹³⁷Cs would be found in abandoned paddy soils with properties similar to the studied soil, sandy loam but poorly drained because of the low permeable plowpan layer, although further validation is necessary.

Asymmetric dispersal in the multi-patch logistic equation

The standard model for the dynamics of a fragmented density-dependent population is built from several local logistic models coupled by migrations. First introduced in the 1970s and used in innumerable articles, this standard model applied to a two-patch situation has never been fully analyzed. Here, we complete this analysis and we delineate the conditions under which fragmentation associated with dispersal is either favorable or unfavorable to total population abundance. We pay special attention to the case of asymmetric dispersal, i.e., the situation in which the dispersal rate from patch 1 to patch 2 is not equal to the dispersal rate from patch 2 to patch 1. We show that this asymmetry can have a crucial quantitative influence on the effect of dispersal.

Effect of sampling methods, effective population size and migration rate estimation in Glossina palpalis palpalis from Cameroon

Human and animal trypanosomiases are two major constraints to development in Africa. These diseases are mainly transmitted by tsetse flies in particular by Glossina palpalis palpalis in Western and Central Africa. To set up an effective vector control campaign, prior population genetics studies have proved useful. Previous studies on population genetics of G. p. palpalis using microsatellite loci showed high heterozygote deficits, as compared to Hardy-Weinberg expectations, mainly explained by the presence of null alleles and/or the mixing of individuals belonging to several reproductive units (Wahlund effect). In this study we implemented a system of trapping, consisting of a central trap and two to four satellite traps around the central one to evaluate a possible role of the Wahlund effect in tsetse flies from three Cameroon human and animal African trypanosomiases foci (Campo, Bipindi and Fontem). We also estimated effective population sizes and dispersal. No difference was observed between the values of allelic richness, genetic diversity and Wright's FIS, in the samples from central and from satellite traps, suggesting an absence of Wahlund effect. Partitioning of the samples with Bayesian methods showed numerous clusters of 2-3 individuals as expected from a population at demographic equilibrium with two expected offspring per reproducing female. As previously shown, null alleles appeared as the most probable factor inducing these heterozygote deficits in these populations. Effective population sizes varied from 80 to 450 individuals while immigration rates were between 0.05 and 0.43, showing substantial genetic exchanges between different villages within a focus. These results suggest that the "suppression" with establishment of physical barriers may be the best strategy for a vector control campaign in this forest context.

Study on the rate of plutonium vertical migration in various soil types of Lublin region (Eastern Poland)

Soil contamination level with 239+240Pu of Lublin region was determined using the alpha spectrometric method. Results were compared with similar data from the study performed 15 year earlier. Decrease in total 239+240Pu concentration and reducing quantity of Chernobyl fraction (up to almost negligible value of 1 %) has been observed in upper soil layer. Determination of 239+240Pu concentration in soil profile layers allows calculating a vertical migration velocity of plutonium applying a compartment migration model. It was found that 239+240Pu migration rate varies depending on soil type from 0.29 cm year-1 in Podsols to 0.58 cm year-1 in Fluvisols with mean value of 0.5 cm year-1.