[Response of Phytoplankton Functional Groups to Eutrophication in Summer at Xiaoguan Reservoir].

Hydrology and Water Resources Bureau of Guizhou Province, Guiyang 550002, China) Abstract: In order to explore the distribution characteristics of phytoplankton functional groups, eutrophication characteristics and response of phytoplankton functional groups to eutrophication in Xiaoguan Reservoir, phytoplankton and water samples were taken once a week from 25th July 2014 to 27th September 2014. The results showed that there were 22 phytoplankton functional groups, groups S1, D, J, B, G, MP, L0, SN, X1, Y, Xph, F, T and W1 were comparatively common functional groups, Wherein, S1, D and J were the dominant functional groups. Weekly dynamics of phytoplankton functional groups were: S1-->S1-->S1-->S1-->S1--S1-->S1-->J/D/S1-->Sl1- >/1D. group Sl1dominated over other groups, the cell abundance of S1 appeared two peaks at week 5 and week 7 respectively, but there was a slump at week 8, and rose again at last, compared to two peaks before, the cell abundance had dropped from 108cells · L⁻¹ to 107cells · L⁻¹ Water flush caused by discharge gate opening artificially was the main reason. Based on the three methods of eutrophication evaluation, the water was in moderately eutrophic and eutrophic states in Xiaoguan Reservoir in the summer of 2014. Multivariate analysis (RDA) indicated transparency was the main factor affecting the distribution of phytoplankton functional groups, and nutrients were no longer the limiting factor. The study suggested that phytoplankton functional groups could make a good response to eutrophication: groups S1 and J adapted to the turbid eutrophic water bodies, D adapted to shallow turbid waters and was sensitive to nutrient depletion. Also, common functional groups like G, X1, WW1 F etc. mostly adapted to eutrophic water bodies.

[Mercury dynamics of several plants collected from the water-level fluctuation zone of the Three Gorges Reservoir area during flooding and its impact on water body].

Submerged plants are a major source for the abnormal elevation of methylmercury in reservoir. Several specific plants (Echinochloa crusgalli, Cynodondactylon and Corn stover) were collected and inundated in a simulated aquatic environment in the laboratory for investigating the mercury (Hg) dynamics in plants and the release process into water, aiming to find out the properties of Hg dynamics of plants under inundation conditions and its impact on water body in the Water-Level Fluctuation Zone of the Three Gorges Reservoir Area. The results showed that the contents of total mercury in several plants were in the range of 9. 21-12.07 ng x g(-1), and the percentage content of methylmercury (MeHg) was about 1%-2%. The content of total mercury (THg) in plants gradually decreased, by 35.81%-55.96%, whereas that of the dissolved mercury (DHg) increased sharply, by 103.23% -232.15%, which indicated an emission of Hg from plants to water in the process of decomposition. Furthermore, the state of inundation provided sufficient conditions for the methylation process in plants and therefore caused an increase of the content of methylmercury in the plant residues, which was 3.04-6.63 times as much as the initial content. The concentration of dissolved methylmercury (DMeHg) in the overlying water also increased significantly by 14.84- 16.05 times compared with the initial concentration. Meanwhile, the concentration of dissolved oxygen (DO) in the overlying water was significantly and negatively correlated with DMeHg. On the other hand, the concentration of dissolved organic carbon (DOC) in the overlying water was significantly and positively correlated with DMeHg. During the whole inundation period, the increase of DHg in the overlying water accounted for 41.74% -47.01% of the total amount of THg emission, and there was a negative correlation between the content of THg in plant residues and that of DHg in the overlying water.

[Influence of light wavelength and intensity on the reduction of divalent mercury in aquatic system].

Laboratory experiments were conducted to investigate the photo-reduction of HgCI2, under various light wavelengths and intensities. The whole process was tracked by changing Hg0 concentrations in argon and Hg0 flux was calculated for qualitative and quantitative analysis; the rate order was determined by both differential and integral methods. The principal results indicated: Higher mercury emission flux was observed under shorter light wavelength and stronger intensity, which shows the important role of photoenergy in the reaction. The degree of mercury reduction was determined by radiation wavelength and intensity, and it was also influenced by solution volume and the flow rate of carrier gas. Under different light conditions, Hg0 concentrations in argon all increased at the beginning and decreased after a specific time period, since the main reactions in rising period were the photo-reduction of Hg2+ and the emission of Hg0 while the reaction in decreasing period was the emission of Hg0 only. The rate order under visible light was the first order while it was the second order under UVA and UVB, which attributes to the fact that coordination complex has certain light absorption band, which is related with the available light wavelength provided by experimental lamps.

[Distribution and risk assessment of mercury species in soil of the water-level-fluctuating zone in the Three Gorges Reservoir].

To investigate pollution level and ecological risk of mercury in soils of the water-level-fluctuating zone in the Three Gorges Reservoir Region, 192 surface soil samples from 14 counties (districts) in Chongqing were obtained. Concentrations of THg and Hg species, bioavailable Hg were analyzed and discussed. Geoaccumulation index (I(geo)) and Håkanson potential ecological risk index (E(r)) were applied to assess the pollution status and potential ecological risk of THg and Hg species, respectively. The results showed that significant differences in the concentration of THg were found in soils of water-level-fluctuating zone in the Three Gorges Reservoir. The THg concentration ranged from 22.4 to 393.5 microg x kg(-1), with an average of (84.2 +/- 54.3) microg x kg(-1). 76.6% of the samples' THg content was higher than the soil background value in the Three Gorges Reservoir Region. The percentage of five mercury species (water-soluble Hg, HCl-soluble Hg, KOH-soluble Hg, H2O2-soluble Hg, residue Hg) in soils were 4.1%, 15.5%, 18.3%, 10.9%, 51.3%, respectively. The average concentrations of bioavailable mercury varied between 19.7-36.6 microg x kg(-1), and the percentage of bioavailable Hg was 22.1%-51.6% of THg. According to the geoaccumulation index, the soils were lightly polluted by Hg. Håkanson single potential ecological risk index evaluation showed that Hg species had a low potential ecological risk, moreover, soils of water-level-fluctuating zone in the Three Gorges Reservoir were at low ecological risk levels as evaluated by bioavailable Hg. While, the assessment results based on THg of soils was much higher than that based on the Hg species. Two methods of evaluation showed that the I(geo) and E(r) values calculated based on the Hg species better reflected the actual pollution levels of soils and its hazard to aquatic organisms.

[Mercury fluxes from conifer-broadleaf forested field in central subtropical forest zone].

Total gaseous mercury fluxes of forested field soils in the subtropical forest zones, Chongqing, Southwestern China were continually monitored from April 2011 to March 2012 to provide insights into the characteristics of gaseous mercury flux with conifer-broadleaf forest covers. Samples were collected from surfaces of forest fields as the most representative terrestrial surfaces in Jinyun Mountain. Simultaneously, meteorological parameters at the soil level relating to GEM fluxes, such as soil temperature, air humidity, and solar radiation were analyzed, and variations of atmospheric GEM concentration were examined. The results showed that annual averaged fluxes from soils in the forest and open-air site were (16.82 +/- 6.70) ng x (m2 x h)(-1), which was significantly higher than that in the natural background area. Moreover, there was a clear seasonal variation on the forest field. In growing season, the average mercury flux was (22.23 +/- 13.19) ng x (m2 x h)(-1), while in dormant season the value was (6.01 +/- 4. 05) ng x (m2 x h)(-1). Diurnal variation characteristics of mercury fluxes were closely related to solar radiation on the forest field. Mercury fluxes of the soils were significantly correlated with soil temperature, air temperature and relative humidity, which may be caused by the relationship between solar radiation intensity and mercury emission fluxes from soils.

[Effects of low molecular weight organic acids on redox reactions of mercury].

To study the effects of the main component of vegetation root exudates-low molecular weight organic acids on the redox reactions of mercury, laboratory experiments were conducted to investigate the roles of tartaric, citric, and succinic acid in the redox reactions of mercury, and to analyze their interaction mechanism. The results indicated that tartaric acid significantly stimulated the mercury reduction reaction, while citric acid had inhibitory effect. Succinic acid improved the reduction rate at low concentration, and inhibited the reaction at high concentration. The mercury reduction rate by tartaric acid treatment was second-order with respect to Hg2+ concentration, ranging from 0.0014 L x (ng x min)(-1) to 0.005 6 L x (ng x min)(-1). All three organic acids showed a capacity for oxidating Hg(0) in the early stage, but the oxidized Hg(0) was subsequently reduced. The oxidation capacity of the three organic acids was in the order of citric acid > tartaric acid > succinic acid.

[Release of mercury from soil and plant in water-level-fluctuating zone of the Three Gorges Reservoir area and its accumulation in zebrafish].

To investigate the production, distribution and bioavailability of methylmercury (MMHg) in soil and plants of the water-level-fluctuating zone (WLFZ) of the Three Gorges Reservoir area, simulation experiments were conducted in laboratory. Results indicated that the level of total mercury (THg) in soil decreased with the lengthening of submerging time while that in water increased obviously. The level of MMHg in inundated soil and water increased, especially in the water treated by Echinochloa crusgalli and soils. And the MMHg level in that treatment was 2.52 times higher than that treated only by soils for 21 days. This indicated that soil and plants of WLFZ were important sources of mercury in the water of the reservoir. Echinochloa crusgalli as the tested plant was decomposed after being submerged, leading to lower pH and DO and higher DOC, which had little effect on MMHg in soil but significant effect on MMHg in water. The level of THg in the head, viscera and muscle of zebrafish increased obviously, which had a significant correlation with that in water (P < 0.01). MMHg levels accumulated in the head, viscera and muscle of zebrafish differed to some degree, particularly in the head and muscle. After treated in the soils for 21 days, MMHg levels in the head, viscera and muscle of zebrafish were 1.75-6.25, 3.53-8.38 and 2.22-3.36 times higher than those in the control groups, respectively. While for the treatment of Echinochloa crusgalli and soil, MMHg levels in zebrafish's head, viscera and muscle were 3.57, 2.37 and 1.52 times higher than those treated only by soil, respectively. Therefore, submerged soil was the main source of MMHg in fish. And submerged plants changed the water condition and affected the release of mercury to water so as to cause elevated levels of MMHg in fish.

[Effect of nano-TiO2 on the release and activation of mercury in sediment].

To investigate the effects of nano-TiO2 on mercury release and activation in sediment, flooding simulation experiments were conducted. The impacts of nano-TiO2 on total mercury and methylmercury concentrations in overlying water were analyzed. And the influences of nano-TiO2 on the migration and transformation of mercury were discussed based on changes of mercury speciation in sediment. The results indicated that nano-TiO2 promoted the release of mercury in sediment, leading to more mercury released into the water. Compared with the control, 4 g x kg(-1) TiO2 nanoparticles increased the total mercury by 91.32%, when the concentration of total mercury in overlying water was the highest. Release of mercury in soil was increased by approximately 10% finally. The main reason may be that the dissolution of oxidation state mercury was improved by nano-TiO2. It indicated that the risk of mercury contamination in water may increase. Moreover, under the experimental conditions, nano-TiO2 may reduce the formation of methylmercury in sediment in the short-term, but no significant effects in the long-term. Generally, the effects of nano-TiO2 on the release and transformation of mercury in sediment showed concentration dependence. Thus, with increasing nano-TiO2 content in sediment or soil, its impact on the geochemical cycle of mercury may increase.

[Effects of nitrate ion on monomethylmercury photodegradation in water body].

To study effects of nitrate (NO3(-)) on monomethylmercury (MMHg) photodecomposition (PD), laboratory experiments were conducted to investigate the role of NO3(-) in MMHg PD under various light radiations, and to examine effects of NO3(-) concentration gradients on MMHg PD rates and end products. We analysed the react processes according to Hg2+ concentration. The results indicated that in the reactor exposed to natural and ultraviolet radiation, and treated with NO3(-), the rates of MMHg PD were calculated to be 0.10 L x (ng x h)(-1) and 0.046 L x (ng x h)(-1), respectively, Hg(0) fluxes were 1.05 and 1.27 ng, respectively, and Hg2+ concentrations were 16.97 ng x L(-1) and 28.92 ng x L(-1) respectively. In the experiments which were not spiked with nitrate or spiked with benzoic acid, MMHg PD rates were calculated to be 0.052 L x (ng x h)(-1) and 0.015 L x (ng x h)(-1), respectively, Hg(0) fluxes were 23.81 ng and 15.38 ng, respectively, and all concentrations of Hg2+ (< 10 ng x L(-1)) represented a trend of increasing firstly and then decreasing. There were no differences among the reactions exposed to visible light (P = 0.56), the PD rate was about 0.003 L x (ng x h)(-1), Hg(0) flux was about 5 ng, and Hg2+ concentrations showed a trend of increasing firstly and then decreasing. In the reactor exposed to natural light, with the increasing concentration of NO3(-), MMHg PD rate increased, Hg(0) flux decreased, and Hg2+ concentration increased with respect to time. All results indicate that NO3(-) has a significant effect on the react process, PD rate, and end products.

[Mercury speciation transformation in soil of the water-level-fluctuating zone in the Three Gorges area under alternative dry-wet condition].

The speciation transformation, influencing factors, as well as bioavailability of mercury (Hg) in soil of the water-level-fluctuating zone in the Three Gorges Reservoir Area were simulated. The results showed that Hg in soil under alternative dry-wet condition could be transformed and released. The total Hg content in the soil was decreased by 28.9% after two "wet-dry" cycles. The percentages of the six Hg species (water-soluble, exchangeable, carbonate-bound, humics-bound, organic-sulf and residual Hg) were 6.1%-16.8%, 5.8% -12.9%, 4.5%-17.7%, 12.5%-29.9%, 5.3%-12.8%, and 34.5%-51.6%, respectively. It was found that Hg in soils was dominantly residue Hg, whose percentage tended to decrease under alternative dry-wet condition. The percentage of humics-bound Hg increased gradually and an increase of the percentage of bioavailable Hg (including water-soluble, exchangeable, carbonate-bound, and humics-bound Hg) after two wet-dry cycles were observed. Bioavailable Hg could be easily absorbed by aquatic organisms to enter the food chain, which might increase the ecological risk of Hg in the reservoir.

Vesical varices causing gross hematuria in a four-year-old girl.

Primary vesical varices are rare. We report a case of a 4-year-old girl who presented with recurrent gross hematuria secondary to primary vesical varices. Ultrasonography, enhanced computed tomography, and voiding cystourethrogram revealed a solid mass in the right wall of the bladder. Cystoscopy revealed a group of dilated submucosal veins and a red mass. The mass was ablated, and the histopathologic examination demonstrated varices of the bladder. Observation of the patient for 6 months postoperatively showed no recurrence of the hematuria.

[Characteristics of monomethylmercury photodegradation in water body].

To investigate the photochemical process of monomethylmercury (MMHg) in the water environment, laboratory experiments were conducted using artificial and visible light sources to confirm the effects of wavelength and light intensity on MMHg photodegradation (PD), and the reaction process of MMHg PD was discussed based on Hg(0) emission rate. The results indicated that Hg(0) was the end product of MMHg PD, and the light conditions had an effect on the rate constant of MMHg PD and Hg(0) flux. When the reactor was exposed to UV light conditions, the rate constant of MMHg PD increased with the decrease in wavelength and the increase in light intensity. The rate of MMHg PD was first-order with respect to MMHg concentration in the reactor, and the rate constants were K(UVA) 0.403-0.562 h(-1), K(UVB) 0.961 h(-1), K(UVC) 1.221 h(-1) and K(VL+UVA+UVB) 1.346 h(-1), respectively and the emission rates of Hg(0) were 0.166-0.392 ng x min(-1). When the reactor exposed to visible light conditions, the rate of MMHg PD was only 0.061 h(-1), and the emission rate of Hg(0) was 0.008 ng x min(-1). In the experiments conducted under dark conditions, we did not observe MMHg PD and no Hg(0) was found. All the results suggest that the degradation of MMHg in artificial waters is mediated by ultraviolet (UV) radiation, and UV radiation plays a key role in the photochemical process of MMHg in freshwater lakes.

Cystic lymphatic malformation of bladder presenting as a pelvic mass.

We report a 5-year-old boy with a cystic lymphatic malformation (LM) of bladder, and the imaging characteristics of the lesion are reported. Cystic LM of the urinary system is rare, and a location in the bladder is extremely rare. The exact mechanism of the lesion that occurs in bladder is unknown. This case is different from the 3 cases reported before, for it is only presented with a palpable pelvic mass and the lesion did not penetrate full thickness of bladder. Although imaging examinations are helpful in the definition of cystic LMs, no characteristic findings are available to diagnose a cystic LM of the bladder before surgery. The diagnosis is always made after surgical intervention. Surgical excision is ideal, and an extensive operation is not warranted because the lesion is benign. Once excised completely, the prognosis of the disease is good.