Migration characteristics and potential determinants of mercury in long-term decomposing litterfall of two subtropical forests.

It is of great importance to elucidate the mechanism of mercury (Hg) migration in the forest litterfall so as to clearly understand global Hg deposition. However, it is still unclear for the migration and transformation of Hg in different forest litters during long-term decomposition. Therefore, the dynamics of total Hg (THg), methylmercury (MeHg), carbon, nitrogen, microbial biomass carbon and nitrogen in the litterfall of the evergreen broadleaf (EB) and mixed broadleaf-conifer (MBC) forests, southwest China were investigated, aiming to understand the migration characteristics of Hg in the two-year decomposing litterfall. Results showed that carbon decreased, while nitrogen accumulated slightly in the process of litterfall decomposition. THg levels in the second year of the EB and MBC forests decreased by 16.9% and 11.3%, while MeHg levels reduced by 141.4% and 210.7% respectively comparing with those in the first year. The total percentage of hydrochloric acid-soluble mercury (Hg-h) and water-soluble mercury (Hg-w) had a significant impact on the migration of THg and MeHg in the two forest stands. The C/N ratio in the EB forest bore a positive correlation with THg and MeHg levels, whereas that in the MBC forest was adverse. Besides, microbial biomass C and N were positively related with THg and MeHg levels in both the EB and MBC forests. It is proposed that THg and MeHg accumulation in the second year drastically decreased probably due to finite nutritional conditions, which implies that Hg accumulation risks alleviate with degradation time.

American college of radiology ovarian-adnexal reporting and data system ultrasound (O-RADS): Diagnostic performance and inter-reviewer agreement for ovarian masses in children.

Objective: To evaluate the diagnostic performance and inter-observer agreement of the American College of Radiology Ovarian-Adnexal Reporting and Data System Ultrasound (O-RADS) in the diagnosis of ovarian masses in children. Methods: From June 2012 to December 2021, 163 ovarian masses in 159 patients with pathologic results were retrospectively analyzed. Each mass was classified into an O-RADS category according to the criteria. The diagnostic performance of O-RADS for detecting malignant ovarian masses was assessed using histopathology as the reference standard. Kappa (k) statistic was used to assess inter-observer agreement between a less-experienced and a well-experienced radiologist. Results: Out of 163 ovarian masses, 18 (11.0%) were malignant and 145 (89.0%) were benign. The malignancy rates of O-RADS 5, O-RADS 4, and O-RADS 3 masses were 72.7%, 34.6%, and 4.8%, respectively. The area under the receiver operating characteristic curve was 0.944 (95% CI, 0.908-0.981). The optimal cutoff value for predicting malignant ovarian masses was > O-RADS 3 with a sensitivity, specificity, and accuracy of 94.4%, 86.2% and 86.2% respectively. The inter-observer agreement of the O-RADS category was good (k = 0.777). Conclusions: O-RADS has a high diagnostic performance for children with ovarian masses. It provides an effective malignant risk classification for ovarian masses in children, which shows high consistency between radiologists with different levels of experience.

Understanding heavy metal accumulation in roadside soils along major roads in the Tibet Plateau.

The heavy metal accumulation in the Tibet Plateau (TP) poses a serious ecologic risk to the health of human and the other biota. Given the TP far away from the large anthropogenic emission sources, the rapid development of traffic activities during last several decades possibly leads to the elevated heavy metal concentration in the roadside soils. Therefore, we comprehensively assessed the heavy metal distribution in the 0-5 cm and 15-20 cm depth soils located at 5 m, 50 m, and 100 m distance to the edge of two major roads among the different vegetation covers and climatic conditions in the TP to verify this hypothesis. Results show that most of heavy metal concentrations in soils of different distance to the major road display an insignificant difference. The Nemero Synthesis indexes which represent the risk of pollution for these regions almost range 1 to 2 (low pollution risk), except 12.7 (extreme pollution risk) at one site. These indicate the limited impacts from the traffic activities for the whole region, but at some specific sites with the elevated traffic pollution. The forest cover at the altitude of 3700-4100 m has the highest mercury accumulation due to the vegetation and climatic factors induced the higher atmospheric depositions and stronger complexation with the organic matters. The statistical analysis finally suggests the geogenic weathering processes, climate, terrain and vegetation play an important role in shaping heavy metal distribution along the roadside of the TP.

Bacteria and archaea involved in anaerobic mercury methylation and methane oxidation in anaerobic sulfate-rich reactors.

The identification of dominant microbes in anaerobic mercury (Hg) methylation, methylmercury (MeHg) demethylation, and methane oxidation as sulfate-reducing bacteria, methanogens or, probably, anaerobic methanotrophic archaea (ANMEs) is of great interest. To date, however, the interrelationship of bacteria and archaea involved in these processes remains unclear. Here, we demonstrated the dynamics of microorganisms participating in these processes. Anaerobic fixed-bed reactors were operated with swine manure and sludge to produce methane stably, and then, sulfate (reactor C), sulfate and Hg(II) (reactor H), and sulfate and MeHg (reactor M) were added, and the reactors were operated for 120 d, divided equally into four periods, P1-P4. The bacterial compositions changed nonsignificantly, whereas Methanosaeta in reactors H and M decreased significantly, revealing that it was irrelevant for Hg transformation. The abundances of Syntrophomonadaceae, Methanoculleus, Candidatus Methanogranum and Candidatus Methanoplasma increased continuously with time; these species probably functioned in these processes, but further evidence is needed. Desulfocella and Desulfobacterium dominated first but eventually almost vanished, while the dominant archaeal genera Methanogenium, Methanoculleus and Methanocorpusculum were closely related to ANME-1 and ANME-2. PLS-DA results indicated that both bacteria and archaea in different periods in the three reactors were clustered separately, implying that the microbial compositions in the same periods were similar and changed markedly with time.

Characteristics of archaea and bacteria in rice rhizosphere along a mercury gradient.

Several strains of archaea have the ability to methylate or resist mercury (Hg), and the paddy field is regarded to be conducive to Hg methylation. However, our knowledge of Hg-methylating or Hg-resistant archaea in paddy soils is very limited so far. Therefore, the distribution of archaea and bacteria in the rhizosphere (RS) and bulk soil (BS) of the rice growing in Xiushan Hg-mining area of southwest China was investigated. Bacterial and archaeal 16S rRNA gene amplicon sequencing of the rice rhizosphere along the Hg gradient was conducted. THg concentrations in RS were significantly higher than that in BS at site S1 and S2, while MeHg concentrations in RS was always higher than that in BS, except S6. Bacterial species richness estimates were much higher than that in archaea. The bacterial α-diversity in high-Hg sites was significant higher than that in low-Hg sites based on ACE and Shannon indices. At the genus level, Thiobacillus, Xanthomonas, Defluviicoccus and Candidatus Nitrosoarchaeum were significantly more abundant in the rhizosphere of high-Hg sites, which meant that strains in these genera might play important roles in response to Hg stress. Hg-methylating archaea in the paddy field could potentially be affiliated to strains in Methanosarcina, but further evidence need to be found. The results provide reference to understand archaeal rhizosphere community along an Hg gradient paddy soils.

Methyl and Total Mercury in Different Media and Associated Fluxes in a Watershed Forest, Southwest China.

Mercury (Hg) deposition in the forest ecosystem is a significant source of input for methyl Hg (MeHg) and total Hg (THg) to the subtropical forest field and downstream aquatic systems. Wet deposition, litterfall, runoff, and fluxes with forest soil percolate of MeHg and THg were sampled for two years in a watershed forest of southwest China. Results showed that the depositions of THg and MeHg through litterfall and throughfall were 86 µg m-2 yr-1 and 0.8 µg m-2 yr-1 respectively, with litterfall acting as a predominant route for the input of both THg and MeHg. The estimated fluxes of THg and MeHg in the throughfall and litterfall were 3 and 4 times greater than those in the precipitation. Methylmercury in the decomposed litter migrates during its erosion by surface runoff and the concentrations of MeHg were quite consistent with that in the surface runoff. Methylmercury mainly accumulated in the lower layer of the litter and upper layer of the soil (Oi), and its transfer through the soil cross-section was delayed. THg retention was not consistent with MeHg, probably with lower soil layers (Oe and Oa) storing and enriching THg in the forest ecosystem. The forest floor of the lower soil is an effective sink for THg but not for MeHg. Methylmercury accumulated in decomposing litter and upper soil layer might transfer with soil percolate, possessing potential ecological risks for residents living around the downstream aquatic systems.

[Migration and Transformation of Mercury in Unsubmerged Soil and Sediment at One Typical Forest Reservoir in Southwest China].

Mercury (Hg) has been regarded as a global pollutant due to its volatility and toxicity. The sediment in the reservoirs or lakes is an important compartment for Hg methylation and it has also been considered as a sensitive area of Hg. In this study, a typical forest reservoir surrounding by evergreen broad-leaved forest in Chongqing of southwest China was selected to investigate the migration and transformation of Hg in unsubmerged soil and sediment. The unsubmerged soil and sediment were also replaced to each other to observe the dynamics of THg and TMeHg concentrations in equilibrium processes. The results were as follows:① The THg and TMeHg mean concentrations in Dahonghai reservoir water were (1.89±0.72) ng·L-1 and (0.13±0.04) ng·L-1, respectively, which were lower than the first class water quality standards in environmental quality standard of China and other reservoirs or lakes, implying that this study area did not affect by Hg pollution. Meanwhile, the THg and TMeHg mean concentrations in unsubmerged soil and sediment were also lower than those in other reservoirs or lakes. ② Seasonal variations of THg and TMeHg concentrations in reservoir water and soil were both observed higher in warm seasons, and more obvious variations occurred for TMeHg which probably influenced by meteorological parameters, such as, temperature and rainfall. ③Compared with unsubmerged soil, the THg and TMeHg mean concentrations in sediment were both elevated, suggesting the sediment was an important sink of Hg. While, the sediment would be a source of Hg (especially TMeHg) with a high THg and TMeHg level. ④ The THg and TMeHg mean concentrations in unsubmerged soil and sediment after situ replacement were equilibrated with ambient soil in a short time (one or two months), implying the hydro-fluctuation belt of reservoir promoting the geochemical cycle of Hg.

[Mercury Release Flux and Its Influencing Factors Under Four Typical Vegetation Covers at Jinyun Mountain, Chongqing].

In order to reveal the characteristics of mercury release flux and exchange across the soil/atmosphere interface under different vegetation cover types, four of these types (evergreen broad-leaved forest, bamboo forest, shrub, and grassland) were chosen as research samples at Jinyun Mountain National Nature Reserve, Chongqing, Continuous monitoring of the different vegetation covers, soil/atmosphere interface, and mercury release flux was conducted, at the same time as the effects of environmental factors were also considered. Results show that the annual average Hg emission flux for the four kinds of forest cover have obvious differences. The overall emission performance of Hg is ranked as:bamboo forest[17.77 ng·(m2·h)-1] > grassland[17.58 ng·(m2·h)-1] > shrubbery[16.87 ng·(m2·h)-1] > evergreen broad-leaved forest[14.32 ng·(m2·h)-1]. There are obviously seasonal differences between Hg emission and the four kinds of forested stands in Jinyun mountain and there are significant differences among the different forests. These differences mainly reflect that emissions in the warm season are higher than in the cold season. There is also an obvious diurnal variation of soil mercury release flux from different forested stands in Jinyun Mountain. Meteorological factors of light intensity, air temperature, soil temperature, and relative humidity also effects the soil/air interface meaning that mercury flux is not the same across land cover types. Temperature is the main factor affecting evergreen broad-leaved forest, shrub forests, and bamboo forests. Light intensity is the main influencing factor for grasslands.

[Effect of Sewage Sludge Compost Products Application on Total Mercury and Methylmercury in Soil and Plants].

Two different sludge composting products (with and without biochar) were applied in field to study the variations of total mercury (THg) and methylmercury (MeHg) in soil and plants,as well as their migration in the soil-plant system and accumulation ability in plants during the sludge compost land use process.The results indicated that the concentrations THg and MeHg in soil increased after applying sewage sludge compost products,while the THg level was still lower than the secondary standard of national soil environmental quality.Biochar was speculated to probably promote the soil mercury methylation with lower MeHg/THg ratios in different soil treatments.THg concentrations in mature plants were significantly lower than those in seedling stage,but MeHg levels were higher than those in seedling stage.An obvious influence of composting on MeHg enrichment in plants was observed,and this similar effect was not found for THg enrichment.MeHg concentration in the soils applied with biochar compost was significantly higher than that without applying biochar compost soil,while MeHg in plant presented a contrary trend with higher level observed in no-biochar compost soil,suggesting that the addition of biochar could be in favour of soil MeHg formation and inhibit the MeHg accumulation in plants by influencing its migration.Since a strong MeHg accumulation ability with BCF of 1.24-14.63 was present in plant,the mercury ecological risk in soil environment caused by long-term fertilizing should be noticed.

[Effect of Soil and Dominant Plants on Mercury Speciation in Soil and Water System of Water-Level-Fluctuation Zone in the Three Gorges Area].

Plentiful plants in the water-level-fluctuation-zone (WLFZ) of Three Gorges Reservoir ( TGR) grow vigorously during the non-flooded period, especially the herbaceous ones. Then, the WLFZ is submerged gradually from the end of September. Soil-plant system that under a long time flooded condition may change the form of mercury, thus resulting in a secondary pollution of the water environment in TGR. To understand the characteristics of mercury species in soils and water after submerged, four kinds of typical plants from TGR were tested in the lab under submerged condition. The results indicated that the plants could promote the formation of soil methylmercury ( MeHg) , and had a significant effect on the different forms of mercury concentrations of the overlying water during inundation. Cynodon dactylon as the dominant species in WLFZ, because of its higher content of total mercury ( THg ) and methylmercury, the effect on MeHg and the other forms of mercury in the soil and the overlying water system was obvious. After 90 days, the soil MeHg level was the highest in Cynodon dactylon & soil & water treatment (B1) [(1,135.86 ± 113.84) ng · kg⁻¹]. It was approximately 2 times less than that of the soil MeHg in soil & water treatment (CK2) . The variation characteristics of total mercury (THg), reactive mercury (RHg) , dissolved mercury (DHg), total methylmercury (TMeHg) and dissolved methylmercury (DMeHg) of overlying water all showed a parabolic shape with a peak skewed to the left, and the peak was reached on the 30th day. Meanwhile, TMeHg, THg and DHg in B1 treatment were the highest, which were (2.88 ± 0.06), (40.29 · 2.42) and (35.51 · 3.77) ng · L⁻¹ respectively, and TMeHg and THg in the overlying water were mainly in the form of dissolved state. Therefore, it could be inferred that the water consumption of the Three Gorges reservoir would increase the mercury pollution load of the reservoir.

[Dynamic Characteristics of Base Cations During Wet Deposition in Evergreen Broad-leaf Forest Ecosystem].

Based on field tests and laboratory experiments, effects of precipitation, throughfall, litterfall, and groundwater runoff of the ever-green broad-leaf forest on the dynamic characteristics of base cations in Simian Mountain were investigated from September 2012 to August 2013. The results showed that the rainfall of Simian Mountain was apparently acidic, with average pH of 4.90 and maximum pH of 5.14. The soil and canopies could increase pH of precipitation, with soils having the maximum increment, followed by the forest canopy. Forest canopy only had the function of interception on Na⁺. And precipitation could leach out Ca2⁺, Mg2⁺ and K⁺ of the canopies. Moreover, the degradation of litter was probably the main reason for the increase of base cations concentrations in the surface litter water. The litter water leached Ca2⁺, Mg2⁺ and Na⁺ of the forest soil through downward infiltration. The total retention rates of Ca²âº, Mg²âº, Na⁺ and K⁺ were 33.82%, -7.06%, 74.36% and 42.87%, respectively. Ca²âº, Na⁺, K⁺ were found to be reserved in the forest ecosystem, and the highest interception rate was found for Na⁺.

IL-1beta signals through the EGF receptor and activates Egr-1 through MMP-ADAM.

The immediate-early gene Egr-1 controls the inducible expression of many genes implicated in the pathogenesis of a range of vascular disorders, yet our understanding of the mechanisms controlling the rapid expression of this prototypic zinc finger transcription factor is poor. Here we show that Egr-1 expression induced by IL-1beta is dependent on metalloproteinases (MMP) and a disintegrin and a metalloproteinase (ADAM). Pharmacologic MMP/ADAM inhibitors and siRNA knockdown prevent IL-1beta induction of Egr-1. Further, IL-1beta activates Egr-1 via the epidermal growth factor receptor (EGFR). This is blocked by EGFR tyrosine kinase inhibition and EGFR knockdown. IL-1beta induction of Egr-1 expression is reduced in murine embryonic fibroblasts (mEFs) deficient in ADAM17 despite unbiased expression of EGFR and IL-1RI in ADAM17-deficient and wild-type mEFs. Finally, we show that IL-1beta-inducible wound repair after mechanical injury requires both EGFR and MMP/ADAM. This study reports for the first time that Egr-1 induction by IL-1beta involves EGFR and MMP/ADAM-dependent EGFR phosphorylation.