[Structural Characteristics of Zooplankton and Phytoplankton Communities and Its Relationship with Environmental Factors in a Typical Tributary Reservoir in the Three Gorges Reservoir Region].

Based on the data of zooplankton, phytoplankton, and water environmental factors in different seasons in a typical tributary reservoir in the Three Gorges Reservoir Region (Changshou Lake), this study explored the relationships between the structures of the zooplankton and phytoplankton communities and environmental factors using Pearson correlation analysis. The results showed that there were a total of 107 species of 8 phyla of phytoplankton, and cyanobacteria was the most critical constituent with a relative abundance of 61%. The dominant populations included Phormidium tenue, Merismopedia punctata, and Anabaena oscillarioides. A total of 82 species of 4 phyla of zooplankton were identified, and rotifers was the most abundant with a relative abundance of 88%. The dominant populations included six species, such as Keratella cochlearis, Asplanchna priodonta, and Asplanchna girodi. The spatial differences in the abundances, biomass, and biodiversity indexes of zooplankton and phytoplankton were not significant, whereas the seasonal differences in all the other indexes were significant, except for the zooplankton biodiversity indexes. The abundance of phytoplankton was the highest in summer, followed by spring, and it was the lowest in winter. The maximum abundance of zooplankton occurred in spring, and the biomass of zooplankton and phytoplankton in spring was significantly higher than that in winter. The number of phytoplankton species and the Shannon-Wiener index, Pielou's uniformity index, and Margalef richness index in summer were significantly lower than those in winter and spring. The water quality evaluation showed that Changshou Lake was in a clean to oligo-pollution state in winter and spring and a moderate-pollution state in summer, thereby suggesting that Changshou Lake was in an overall eutrophic state. The environmental factors, including Chla, DOC, nutrients (TP, NO2--N, NO3--N, and NH4+-N), DO, Eh, and T, influenced the structures of the zooplankton and phytoplankton communities in Changshou Lake, and there were seasonal differences in the environmental factors.

[Spatial Distribution and Risk Assessment of Heavy Metals in Sediments of the Ruxi Tributary of the Three Gorges Reservoir].

Sediment column and soil samples collected from 12 sampling sites in four regions of the Ruxi River, a typical tributary of the Three Gorges Reservoir, were analyzed for eight selected heavy metals including Cr, Ni, Cu, Mn, Zn, Cd, Pb, and Hg to evaluate their spatial and vertical distribution, source, and biological toxic effects. The results showed that the average concentrations of heavy metals were (79.60±11.87), (41.340±4.999), (32.69±8.70), (823.34±125.76), (122.11±22.82), (0.393±0.140), and (29.122±6.811) mg·kg-1 for Cr, Ni, Cu, Mn, Zn, Cd, and Pb, respectively, and (74.84±39.50) µg·kg-1 for Hg, all of which exceeded the sediment background values of the Yangtze River. A spatial trend of decreasing metal concentrations was observed from the reach influenced by the human activities of Ruxi town to the backwater zone and then to the natural river reach. Moreover, in the backwater zone, the heavy metals in sediments and soil along the river were significantly lower than those in sediments, indicating that the sediments and soil were not one primary source for these metals in backwater zone sediment. From the vertical distribution of sediment, in addition to Pb, the highest level of metals was observed at 8 cm in the reach influenced by human activities, and their concentrations decreased with sediment depth in the backwater zone and natural river beach. Significant correlation was found between all the heavy metals (P<0.01, except Ni), indicating a potential homology of these metals in the Ruxi River. Evaluation results of the geoaccumulation index reveal that there exists light to partial moderate Cd and Zn pollution in the Ruxi River. The evaluation of biotoxicity effects showed that Ni was likely to have toxic effects on organisms with a probability of 10% to 75%, and Cd, Zn, Hg, Cu, Pb, and Cr are likely to have biotoxic effects at<10% probability. The combined effect values of multiple metals indicated that the risk of adverse effects was between low and lower medium in the sediments of the Ruxi River.

[Temporal and Spatial Variation of Mercury in the Water of the Ruxi River Estuary, a Typical Tributary of the Three Gorges Reservoir Area].

Four typical estuaries located in the Ruxi River, a tributary of the Yangtze River, were selected to investigate the possibility of mercury pollution in tributary estuaries from the Three Gorges reservoir water storage. Water samples were collected during the water storage period (September to October), the flooding period (November to December), the water withdrawal period (February to March), and the drying period (May to June) to determine the levels of mercury species including total mercury (THg), particulate mercury (PHg), dissolved mercury (DHg), reactive mercury (RHg), total methylmercury (TMeHg) and dissolved methylmercury (DMeHg). The results showed that the concentration of THg and TMeHg in the estuary of the Ruxi River was comparable with that of other reservoirs or natural waters in China. There was a significant difference in the concentration of DHg and TMeHg in the water at different depths, because DHg and TMeHg might be derived from the release of sediment to the overlying water. Comparing the concentrations of different mercury species in the four estuaries during the same period, it was found that the difference of water flow direction during the water storage period could lead to an uneven concentration distribution of THg and PHg in the estuary areas. During the water withdrawal period, the particles in the estuary water could adsorb and carry a large amount of PHg, resulting in higher THg concentration in the water in comparison with other periods. The concentration of TMeHg in the flooding and the drying periods was higher than in the other two periods, indicating that the stable water level might be conducive to the accumulation of methylmercury in the water, and the severe disturbance of the water level could significantly reduce the concentration of TMeHg in the water.

[Mercury Distribution Characteristics and Its Mass Balance in a Multifunctional Urban Wetland].

The distribution characteristics and the source-sink relationship of total mercury (THg) and methyl mercury (MeHg) were studied in a wastewater treatment area and in a lake deep purification area of a multifunctional urban wetland that integrates domestic sewage treatment plant effluent, water purification, and leisure entertainment in Chongqing. The results showed that the THg concentration ranged from 1.98 ng·L-1 to 38.03 ng·L-1[average concentration was (9.10±5.84) ng·L-1] and MeHg concentration ranged from 0.09 ng·L-1 to 0.84 ng·L-1[average concentration was (0.34±0.08) ng·L-1] in an outlet of wastewater treatment area. In the deep purification zone, the THg concentration ranged from 0.37 ng·L-1 to 85.69 ng·L-1[average concentration of (6.76±2.29) ng·L-1] and the MeHg concentration ranged from 0.04 ng·L-1 to 1.47 ng·L-1[average concentration of (0.35±0.17) ng·L-1]. The interference of human activities on mercury concentration is prominent. The vertical distribution of THg in the water is consistent with that of MeHg, the surface layer has lower values than the deep layer. Material balance suggested that THg in the wetland system decreases by 155.50 g per year, and MeHg decreases by 1.65 g per year, which has a protective effect on the downstream water.

[Distribution Characteristics of Mercury in Different Urban Constructed Wetlands].

To explore the spatial and temporal distribution and the methylation characteristics of mercury in different constructed wetlands in cities, and to understand the potential ecological exposure of mercury in urban wetlands, four artificial wetlands in Chongqing were studied from March 2017 to March 2018. The water samples were collected separately in four quarters, and the mass concentration of total mercury (THg) and methyl mercury (MeHg) was researched for one year. The results showed that the THg concentration in the four wetland waters is higher than the background value of the world's lakes and reservoirs for dam construction, but it is far lower than the waters with pollution history. The THg mass concentration of the water inside the wetlands is slightly higher than in the inlet and outlet. In addition, the THg mass concentration in the aquatic plant growing area, the construction area, the cruise ship parking area, and the frequent play area has an increasing trend, indicating that urban wetlands have a trapping and converging effect of the water's THg, so human activities influence total mercury a lot. The mass concentration of MeHg in the four wetland waters was slightly higher than that in other water bodies. With the exception of the Caiyun Lake, where the mass concentration of MeHg at the outlet was higher than that of the water inlet, the other three wetlands showed lower MeHg mass concentration in the outlet than the inlet. The mass concentration of MeHg in the wetland water increased with increasing water depth. The ratio of MeHg concentration to THg mass concentration (MeHg/THg) was higher than in other waters, indicating that urban wetlands have effect on net mercury methylation from waters. The photoreduction of mercury and its absorption by aquatic plants can reduce the mercury load from urban wetlands to downstream watersheds. The THg mass concentration of the four urban wetland water bodies was high in the spring and autumn, with a slight decrease in the summer, and lowest in the winter. The mass concentration of MeHg was the lowest in winter, and in the other three seasons it was basically flat, about three times higher than in winter. This study clarifies the temporal and spatial distribution and methylation of mercury in urban wetlands. It explores the degree of disturbance of human activities on wetlands and the response characteristics, as well as the impact of wetland mercury on downstream watersheds. To avoid potential mercury exposure, measures need to be established for the construction of artificial wetlands.

[Hair Mercury Concentrations in Residents of Fuling and Zhongxian in the Three Gorges Reservoir Region and Their Influence Factors].

To evaluate the mercury (Hg) exposure risk for residents of the Three Gorges Reservoir Region (TGRR), hair samples were collected from 238 local residents within the central regions of the TGRR (Fuling District and Zhongxian County) in this study. Subsequently, total mercury (THg) and methylmercury (MeHg) concentrations were determined. The results obtained showed that the average THg and MeHg concentrations in hair samples of the residents within these two areas were (0.50±0.54) µg·g-1 and(0.35±0.25) µg·g-1, respectively. Specifically, the average THg and MeHg concentrations in hair samples of Fuling residents were(0.71±0.87) µg·g-1 and(0.53±0.46) µg·g-1, respectively. Both these values were higher than those in hair samples of Zhongxian County residents [THg(0.41±0.36) µg·g-1 and MeHg (0.28±0.26) µg·g-1]. It is noteworthy that the hair Hg levels in residents of these two areas are both well below the U.S. Environmental Protection Agency's reference dose (1 µg·g-1). Hair Hg levels varied slightly among different age groups; higher Hg levels were detected in residents in the age group of 40-50 years(P<0.05). However, there was no significant difference between the hair Hg levels among genders(P>0.05). Hair Hg levels in females were slightly above those in males. Hair Hg levels were significantly correlated with the frequency of fish consumption. Furthermore, hair Hg levels in non-fishermen were significantly lower than those in fishermen. An elevated mean value of (1.44±0.79) µg·g-1(P<0.01), which exceeds the RfD of 1 µg·g-1, was detected in fishermen. Moreover, hair Hg levels in smokers of Fuling and Zhongxian County[(0.55±0.24) µg·g-1 and (0.58±0.54) µg·g-1, respectively] were both markedly higher than those in non-smokers[(0.51±0.30) µg·g-1 and (0.36±0.26) µg·g-1respectively]. In conclusion, the risk of Hg exposure to residents of the TGRR was lower. However, in this study, it was determined that fishermen are at significant risk of Hg exposure.

[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.

[Effects of Agricultural Activities on Soil Mercury Changes in the Water-Level-Fluctuating Zone of the Three Gorges Reservoir].

Farming in the water-level-fluctuating zone (WLFZ) of the Three Gorges reservoir, China, may result in a wide range of environment problems when the sediment is exposed to air. In this study, Qukou, Chongqing, was selected as the research site due to its large WLFZ area and significant agricultural activities. Four kinds of land use types, including rice, maize, vegetables, and grassland, were selected to investigate the distribution of mercury (Hg) in the surface soil. The results showed that the mean concentrations of soil total Hg (THg), bioavailable Hg (Hg-wh), and methylmercury (MeHg) in the surface soil were 25.80-68.74 ng ·g-1, 0.44-0.88 ng ·g-1, and 0.08-0.85 ng ·g-1, respectively. The concentrations of THg, Hg-wh, and MeHg in non-cultivated soil were higher than those in cultivated soil, indicating that farming disturbances could accelerate soil Hg loss. The MeHg concentrations in both non-cultivated and cultivated soil increased up to the maximum value 1-2 months after drying, and then gradually decreased to a relatively stable level. The peak value was approximately four times higher than that at the end of flooding. The percentage of MeHg to THg (% MeHg) was similar to the distribution of soil MeHg, and the peak value occurred at 1 month after drying. However, when% MeHg decreased to the stable level, no significant difference was found compared to the value at the end of flooding (P>0.05). Furthermore, the soil% MeHg had a significantly positive correlation with Hg-wh (r=0.642, P<0.01), while there was no significant correlation with THg (P>0.05), suggesting that Hg methylation was mainly affected by the bioavailability of Hg in the seasonally inundated soil of the WLFZ.

[Characteristics of Mercury Transformation in Soil and Accumulation in Rice Plants in an Acidic Purple Paddy Soil Area].

A pot experiment was conducted to analyze the characteristics of mercury (Hg) accumulation during the rice growth period in acidic purple paddy soil. Results showed that the soil total Hg concentration was stable with time during the rice growth period, while methylmercury (MeHg) increased greatly. Therefore, the ratio of MeHg/THg was mainly affected by MeHg concentration. THg concentration in rice plant parts followed the trend:root > grain > stalk > leaf > husk at the mature grain stage, while MeHg concentration followed grain > root > stalk > leaf > husk. The average of MeHg/THg in rice (24.03%) far exceeded that in soil (3.05%), suggesting that rice plants have a strong affinity for MeHg accumulation. This conclusion was supported also by the great difference in average of bio-concentration factors between MeHg (8.16) and THg (2.31) or the transfer factor in the grain, which was more than 1. Moreover, the bio-concentration factor for grain was higher than that for roots, stalks, and leaves, suggesting MeHg was prone to accumulation in grain compared with other part of rice plants.

[Distribution Characteristics and Risk Assessment of Heavy Metals in the Sediments of the Estuary of the Tributaries in the Three Gorges Reservoir, SW China].

To investigate the pollution status of sediments at the junction of the Three Gorges Reservoir area, sediment samples were collected over four seasons from the junction of the estuary located at a tributary of the Ruxi River and the Yangtze River. The content of eight heavy metals (HMs), including Cr, Zn, Mn, Ni, Cu, As, Cd, and Pb, in sediments was determined by ICP-MS. The results showed the average levels of investigated HMs (in mg·kg-1) were Cr (45.24), Zn (46.46), Mn (406.14), Ni (20.885), Cu (12.49), As (7.02), Cd (0.253), and Pb (11.042). The distribution analysis indicated that the levels of HMs at the river mouth were higher than that of the tributaries of the middle reaches and the two sections nearby. The seasonal distribution shows that the heavy metal content in the spring sediment is higher than in summer, autumn and winter. In addition, the correlation analysis indicated that the eight HMs possessed similar homologous characteristics and had common exogenous inputs. The assessment of the Geo Accumulation Index showed slight Cd pollution in the estuary of Ruxi River, and the Potential Ecological Risk index showed that Cd presented moderate ecological risks. The toxic effect of benthonic organisms was possibly correlated to Ni contamination at the intersection of the tributary and main stream, which was supported by the evidence from the sediment quality criteria. In conclusion, the rating of ecological risk at the mouth of the Ruxi River tributary is slight.

[Characteristics of Mercury Emissions from Coal-fired Power Plants in Chongqing].

Four typical coal-fired power plants in Chongqing, representing two different boiler types (circulating fluidized bed boiler and pulverized coal boiler), were chosen to investigate mercury emission characteristics through a mercury mass balance method by analyzing mercury contents in all input and output raw materials in order to accurately estimate mercury emissions. The results showed coal with mercury concentrations ranging (80.77±6.39)-(266.83±4.71) µg·kg-1 could be a significant contributor of input mercury in these four studied power plants. Most mercury output from these power plants entered into solid waste with high proportion of mercury entering the fly ash in CFB plants and entering the fly ash and desulfurization gypsum in PC plants. Mercury removal efficiencies of studied plants were in the range of 72.89%-96.05%, and these efficiencies in CFB plants were higher than those in PC plants. The mercury emission factors for EFelectricity and EFcoal of these four plants were 4.66-29.47 µg·(kW·h)-1 and 8.55-71.77 mg·t-1, respectively. The mercury emission was also calculated to be 6.13-429.17 g·d-1. Mercury emissions from coal-fired power plants were associated with the content of mercury in coal, boiler type, generation load, pollution control equipment, and so on. To control the mercury emissions, more attention should be paid to improving the generation load, increasing the mercury removal efficiency of flue gas cleaning equipment, and strengthening the supervision of solid waste re-utilization.

[Effect of Sediments on Bioaccumulation of Mercury in Fish Body in the Water-Level-Fluctuating Zone of the Three Gorges Reservoir Area].

Mercury (Hg) in the aquatic environment is easy to accumulate in fish. In order to study the effect of the sediments on Hg accumulation in fish in the water-level-fluctuation zone of the Three Gorges Reservoir, we conducted a 90-days simulated flooding experiment by using the sediments with different concentrations of Hg. Our study showed that the concentrations of the total mercury (THg) and methyl mercury (MeHg) in the overlying water increased after flooding, and the concentrations in the muscle of fish kept increasing in the period of experiment, the concentrations in the viscera and head increased in the earlier period but seemingly decreased in the later period. The bioaccumulated Hg content in the fresh was higher than that in the viscera and head, between which there was no significant difference. Compared with the control group (no sediment), the presence of sediments obviously increased the content of Hg bioaccumulated in fish, and the bioaccumulated Hg level increased with the Hg concentrations in sediment. The THg and MeHg in different fish parts presented a similar variation trend with the BCF ranging 1.93×105-8.89×105 for MeHg and 1.3×103-12.8×103 for inorganic mercury, indicating that MeHg was more prone to accumulate in fish. The MeHg in fish was significantly related with THg, and accumulated MeHg occupied about 80.1% (muscle), 79.3% (visceral) and 66.7% (head) of increased THg. After the reflooding of the sediment in the water-level-fluctuating zone, net methylation could occur with MeHg as the product, and then MeHg would diffuse to overlay water, further increasing the Hg bioaccumulation in fish. Therefore, the potential pollution risk of Hg in the water-level-fluctuationg zone with large area of the Three Gorges Reservoir cannot be ignored.

[Characteristics of Mercury Emissions from Modern Dry Processing Cement Plants in Chongqing].

Three typical modern dry processing cement plants in Chongqing were chosen to investigate mercury emission characteristics and its source and fate through a mercury mass balance method by analyzing mercury contents in all input and output materials. The results showed that limestone was the main source of mercury in three cement plants followed by coal, and their mercury concentrations were (0.025±0.001)-(0.032±0.002) mg·kg-1and (0.080±0.002)-(0.110±0.012) mg·kg-1, respectively. The highest mercury level in all required input materials was (0.447±0.007)-(0.525±0.009) mg·kg-1 for gypsum, while the mercury content of other raw materials were very low. Most of the mercury released from these cement plants entered into flue gas, and the mercury of gypsum entered into cement. The mercury emission fluxes were calculated to be (73.42±8.10)-(215.18±10.75) g·d-1 in these three selected plants. The mercury emission factors for clinke and cement (EFclinker and EFcement) were (0.016±0.001)-(0.049±0.001) g·t-1 and (0.011±0.000)-(0.036±0.001) g·t-1, respectively, which were significantly lower than that employed in cement industry according to the foreign mercury emission factors in the past.

[Release Characteristics of Mercury from Submersed Typical Herbaceous Plants in the Water-Level Fluctuation Zone of the Three Gorges Reservoir Area].

In suit inundation experiments of three typical herbaceous plants were conducted in field to investigate the mercury release characteristics of plants grown in the water-level fluctuation zone of the Three Gorges Reservoir after flooding by regulating the water level. To realize this objective, this study mainly focused on the dynamic change of total mercury (THg) concentrations in plants after inundation, the release rate and flux of THg from plants and its release load in this region. The results showed that the release process of THg in plants fitted exponential curve, suggesting that mercury release rate was quick in the initial inundation period and then flat afterwards as the decomposing plants. The THg release amounts (followed the order of Alternanthera philoxeroides > Polygonum lapathifolium > Cynodon dactylon) were probably influenced by initial C/N ratio and THg concentrations of plants. The decrement of THg concentrations in per unit mass of plants residue was found to be generally proportional to their initial C/N ratio, while the THg release amounts were generally proportional to the initial THg concentrations of plants. The total release loads of three plants (Alternanthera philoxeroides, Polygonum lapathifolium, Cynodon dactylon) were estimated to be 167.31, 78.13 and 88.33 mg·hm-2, respectively, according to their weight distribution and biomass in the water-level fluctuation zone of the Three Gorges Reservoir Area.

[Effects of Long-term Different Tillage Methods on Mercury and Methylmercury Contents in Purple Paddy Soil and Overlying Water].

A long-term experiment was conducted to evaluate the effect of tillage methods on mercury and methylmercury contents in the purple paddy soil and overlying water. The experiment included five tillage methods: no-tillage and fallow in winter, ridge-no-tillage, compartments-no-tillage, paddy-upland rotation and conventional tillage. The results showed that the content of total mercury in soil had the maximum value in the 10-20 cm layer of no-tillage and fallow in winter, ridge-no-tillage and compartments-no-tillage, and the enrichment effect of no-tillage and fallow in winter was especially significant. The concentration of total mercury in soil of paddy-upland rotation and conventional tillage decreased with the increase of the soil depth, and paddy-upland rotation was specifically beneficial to the migration of mercury. The distribution of soil methylmercury was similar to that of total mercury in the soil profile. The methylation ability of soil mercury in the surface and middle of the soil profile was weaker than that at the bottom, while there was an opposite trend for other tillage methods. The concentrations of dissolved mercury ( DHg) and dissolved methylmercury ( DMeHg) in the overlaying water declined with the rise of the water depth in all treatments. The content of DHg in sediment porewater was related to the value of soil total mercury, and they had the same distribution in the soil profile. The content of DMeHg and its proportion accounted for DHg in porewater owned their largest value in the 10-20 cm layer of no-tillage and fallow in winter and ridge-no-tillage, where showed the lowest value of DMeHg in porewater for paddy-upland rotation and conventional tillage. And the percentage of DMeHg in DHg in porewater grew with the increase of soil depth of the latter two methods. Noticeably, the concentration of DMeHg and its proportion accounted for DHg in porewater were both higher than the values in overlying water for all tillage methods.

[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.

Highly selective, sensitive and fluorescent sensing of dimeric G-quadruplexes by a dimeric berberine.

This paper describes the highly selective, sensitive and topology-specific fluorescent sensing of dimeric G-quadruplexes by a polyether-tethered dimeric berberine 1. Compound 1 displays high selectivity for dimeric G-quadruplexes over monomeric ones, and can be lit up by dimeric G-quadruplexes, in particular by the one linked with one TTA subunit. In addition, it shows no effect on the topology or thermal stability of the G-quadruplexes.

[Total Gaseous Mercury and Mercury Emission from Natural Surface at One Typical Agricultural Region in Three Gorges Reservoir].

In situ measurement of total gaseous mercury (TGM) and mercury exchange fluxes between soil with different utilization patterns and atmosphere was conducted at one typical agricultural region in Three Gorges Reservoir. The TGM concentration ranged from 2.67 to 75.5 ng·m-3 with the average of (6.26±8.11) ng·m-3, higher than the global background value. An obvious seasonal variation of TGM was observed, and the TGM values in spring and winter were significantly higher than those in summer and autumn. It was found that the mercury fluxes varied from different landscapes with the emission fluxes at three land use types following the trend:rainfed cropland >paddy field >forest land. Seasonal variations of mercury emission were obvious with highest fluxes in summer and lowest in winter, while the highest daily mercury emission fluxes appeared at midday. Mercury emission fluxes in our study region were mainly controlled by air and soil temperature, humidity, light and ultraviolet, and the air temperature and ultraviolet were regarded as the main factors. The influence of Hg level in soil on Hg emission was not obvious in the presence of environmental factors and agricultural activity.

[Concentrations and deposition fluxes of different mercury species in precipitation in Jinyun Mountain, Chongqing].

Concentrations of mercury (Hg) species in precipitation were measured during the period from April 2013 to March 2014 in Jinyun Mountain, Chongqing, and corresponding deposition fluxes were also estimated. The result showed that the ranges of concentration of total mercury (THg) , dissolved mercury (DHg), particulate mercury (PHg), reactive mercury (RHg), total methyl mercury (MeHg), dissolved methyl mercury (DMeHg), particulate methyl mercury (PMeHg) were 7.47-120.11, 2.51-43.03, 2.28-77.99, 0.14-15.14, 2.58 x 10(-2)-101.62 x 10(-2), 0.30 x 10(-2)-72.29 x 10(-2), and 1.45 x 10(-2)-63.55 x 10(-2) ng x L(-1), respectively. And their estimated annual deposition fluxes were 42.71, 23.51, 19.20, 5.87, 0.61, 0.34 and 0.27 µg x (m2 x a)(-1), respectively. The proportion of MeHg in THg ranged from 0.07% to 3.79% with a mean value of 1.34%, and both PHg and PMeHg in precipitation accounted for approximately 50% of THg (ranged from 10.49% to 89.30%) and TMeHg (ranged from 4.31% to 98.86%). Obvious seasonal variations of Hg concentrations and deposition fluxes were observed, with the highest VWM levels of THg, DHg and PHg occurring in winter and the lowest value occurring in summer. And the RHg concentrations in precipitation in winter and spring were significantly higher than those found in summer and autumn. The variations of deposition fluxes of THg, DHg, MeHg, DMeHg had a similar seasonal trend with the rainfall, decreasing from spring to summer and to autumn and then to winter. The maximum deposition fluxes of RHg also appeared in spring and the minimum value occurred in winter. The wet deposition of Hg in Jinyun Mountain was influenced by rain amount, rainfall frequency and other meteorological conditions. Hg levels in the precipitation were also affected by human activities.

[Distribution of Mercury in Plants at Water-Level-Fluctuating Zone in the Three Gorges Reservoir].

The mercury (Hg) distribution and storage in plants at water-level-fluctuating zone (WLFZ) in the Three Gorges Reservoir were investigated by analyzing the total mercury(THg) and methylmercury ( MeHg) levels in different parts of plants collected from three typical sites including Shibaozhai, Zhenxi and Hanfeng Lake in WLFZ. The results indicated that THg and MeHg concentrations in plants ranged from (1.62 ± 0.57) to (49.42 ± 3.93) µg x kg(-1) and from (15.27 ± 7.09) to (1 974.67 ± 946.10) ng x kg(-1), respectively. In addition, THg levels in different plant parts followed the trend: root > leaf > stem, and similar trend for MeHg was observed with the highest level in root. An obvious spatial distribution was also found with the THg and MeHg levels in plants in Hanfeng higher than those in the same plants in the other two sampling sites (Shibaozhai and Zhenxi), and there was a difference of THg and MeHg storage in plants in various attitudes. The corresponding THg and MeHg storages were 145.3, 166.4, 124.3 and 88.2 mg x hm(-2), and 1.9, 2.7, 3.6 and 3.2 mg x hm(-2) in 145-150, 150-160, 160-170 and 170-175 m attitudes. The accumulation ability of dominant plants in WLFZ for THg (bioaccumulation factor, BAF < 1) was weaker than that for MeHg (BAF > 1).