Table of Content

08 May 2011, Volume 30 Issue 05

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Articles

Earth surface natural mercury emission: Research progress and perspective.

2011, 30(05):  845-856. 

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Earth surface natural mercury (Hg) emission includes the Hg emission from natural sources and the re-emission from previously deposited Hg. It was demonstrated that the total amount of natural Hg emission from earth surface could be far larger than that of the direct emission from human activities. It is of great importance to quantify the natural Hg emission, not only for the evaluation of the effects of reducing anthropogenic Hg emission on the global environment, but also for providing guidance on the policy-making in global Hg-reduction strategy. Due to the lack of reliable methodologies in quantifying the Hg emission from natural sources, we still don’t have a clear understanding about the processes and mechanisms of Hg exchange between earth surface and atmosphere as well as the effects of atmospheric Hg deposition on the processes of earth surface natural Hg emission, and thereby, we are hard to accurately quantify the Hg emission from natural sources. However, with the development of new technologies, we have the feasibility to study the processes, mechanisms, and fluxes of Hg emission from natural sources. To quantify the Hg emission from natural sources would be one of the research frontiers about the biogeochemical cycling of Hg in the environment.

Atmospheric mercury depletion events (AMDEs) in the polar regions: A review.

2011, 30(05):  857-864. 

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Mercury (Hg) is the unique heavy metal transported with gaseous elemental Hg (GEM). Atmospheric Hg can be transported for a long distance, which plays an important role in global Hg cycle. Because of global transportation and deposition, Hg pollution in the polar regions has been concerned. Studies found atmospheric Hg depletion events (AMDEs) in Arctic and Antarctic in 1995 and 2000, respectively. This phenomenon presented a new cycling knowledge of atmospheric Hg in extreme climate and environment. However, current knowledge on atmospheric Hg chemistry and transporting process in polar regions is still unclear. In this paper, the authors presented atmospheric Hg distribution and AMDEs mechanisms, re-emission and impact on organisms in polar regions based on recent years work and proposed an overview on future research in the field.

Environmental mercury pollution in mercury mining areas: A review.

2011, 30(05):  865-873. 

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The mercury (Hg) pollution of surrounding environment caused by mercury mining has been paid attention. Although most of worldwide Hg mining activities have been discontinued or ceased, those abandoned Hg mines pose a lasting impact and damage to the local environment and residents’ health by the remaining solid waste, drainage, and Hg-contaminated soils. This review summarized the analysis method of various Hg forms in environmental samples, the global Hg mining activities distribution and their environmental impact of Hg smelting. The risk assessment and pollution control and treatment were prospected.

Progress in research on microbial methylation of mercury.

2011, 30(05):  874-882. 

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Mercury methylation by microbes plays a key role in mercury biogeochemical cycle, and closely related with public health. It has received increasing attention. The paper reviewed the research history and development state, the factors affecting mercury methylation rates, the methylation mechanism and the main study methods used in this research field. It is pointed out that determining the specific microbes in specific ecosystem, making out the mechanism of microbial methylation, demethylation and species-specific stable isotope fractionation of mercury during microbial methylation will become the hot and focal topics of researches.

Transgenic technology used for phytoremediation of mercury contaminated soil: A review.

2011, 30(05):  883-888. 

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Mercury (Hg) is considered as a global extreme destructive pollutant. Now, the problem of contaminated soil was more and more serious because of industry development and mercury mine exploitation, which took painful results not only to environment, but also to mankind. So, this problem has been concerned by many scientists. Phytoremediation of mercury-contaminated soil had many advantages, including low cost and environment-friendly. This paper introduced the technology of phytoremediation in mercury contaminated sites, especially, the application of transgenic technology in mercury contaminated soil. The significance of transgenic technology in mercury contaminated soil was also discussed.

Evaluation methods for soil heavy metals contamination: A review.

2011, 30(05):  889-896. 

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Due to the long-term residence and accumulation in environment, soil heavy metals had many realistic and potential risks to the ecological environment and human health, being come under more and more attentions. To evaluate the soil heavy metals contamination degree is of significance to the environmental and human health issues, which needs a kind of or several kinds of correct evaluation methods. This paper summarized several related evaluation methods commonly adopted at home and abroad, including index method, model index method, speciation analysis- based method, quantitative analysis of available and total heavy metals contents, human health risk assessment method, and GIS and geostatistics-based method. The index method mainly includes Nemerow index method, enrichment factor method, geo-accumulation index method, and potential ecological hazard index method; and the model index method mainly includes fuzzy mathematics model, grey clustering model, and analytic hierarchy process, etc. The advantages, disadvantages, and limitations of the related methods were also discussed.

Present situation of soil heavy metals contamination in an artisanal zinc-smelting zone of Guizhou, China.

2011, 30(05):  897-901. 

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An investigation was made on the farmland soil heavy metals concentration and their spatial distribution in a former artisanal zinc-smelting zone of Xinguanzhai, Hezhang County, Guizhou Province, aimed to assess the soil heavy metals contamination after the ceasing of artisanal zinc-smelting activities. The average concentrations of Pb, Zn, Cd, Hg, Cu, and As in surface soil were 337, 648, 9.0, 0.44, 121, and 17 mg·kg^-1, being 7.5, 7.9, 26.4, 2.2, 4.7 and 0.8 times as higher as the background values of Guizhou farmland soils, respectively. The single factor pollution index revealed that Cd was the most serious contaminant, followed by Zn, Pb, As, Hg, and Cu. The integral pollution index indicated that within the range of 4 km in the zone, surface soil underwent serious heavy metals combined contamination. Most of the heavy metals accumulated in upper 30 cm soil layer and reduced with soil depth, while Zn and Cd moved downward 15-20 cm due to their higher activity and mobility.

Mercury pollution in natural soil collected from Wanshan mercury mining area, Guizhou Province.

2011, 30(05):  902-906. 

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To clarify the distribution of mercury pollution in the natural soil in Wanshan mercury (Hg) mining area, total mercury (THg) concentrations were measured in 0-30 cm soil layers of alluvial soil, shrub soil and forest soil along the Aozhai river and Xiaxi river with a interval of 4 km. THg concentrations in the same vegetation cover area varied in a wide range (alluvial soil was 0.16-389 mg·kg^-1, shrub soil was 0.09-312 mg·kg^-1 and forest soil was 0.05-299 mg·kg^-1), and spatial distribution of THg indicated that THg in natural soil decreased with increasing distance from the Hg mining area. Moreover, THg concentrations decreased from alluvial soil, shrub soil to forest soil in a sample site, and they decreased with increasing depth in soil profiles.

Distribution of mercury speciation in polluted soils of Wanshan mercury mining area in Guizhou.

2011, 30(05):  907-913. 

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The optimized Tessier sequential extraction procedure (SEP) method was used to analyze the speciation and bioavailability of mercury (Hg) in pollution soils of Wanshan mercury mining area, Guizhou Province. The results indicated that the concentration of Hg in rice paddies was dominated by residual fraction (79.65%), followed by organic bound fraction (19.97%), oxide bound fraction (0.31%), specifically sorbed fraction (0.04%) and exchangeable fraction (0.03%). The content of mercury species in soil samples were found to decrease with distance increasing from pollution sources, except specifically sorbed fraction; the proportion of bioavailable (exchangeable fraction and specifically sorbed fraction) mercury was very low in contaminated area, but the content was obviously higher than those in reference soil.

Methylmercury exposure through rice consumption and its health risk assessment for the residents in Guizhou mercury mining areas.

2011, 30(05):  914-921. 

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Rice, vegetable, pork meat,  and drinking water were sampled from Guizhou mercury (Hg) mining areas to analyze their total mercury (T-Hg) concentrations. All the samples had higher concentration T-Hg, but only rice accumulated methylmercury (Me-Hg). The average intake of Me-Hg through rice consumption by the residents in three villages of Wanshan Hg mining area occupied 97.5%, 94.1%, and 93.5% of the total Me-Hg intake, respectively, and the Me-Hg intake from rice per resident per day had significant relationship with the Me-Hg level of hair, suggesting that rice consumption was the main route of Me-Hg exposure for the local residents in Guizhou Hg mining areas. The T-Hg concentration in the hairs of artisanal mining workers was significantly higher than that of the common people and control group, and the proportion of Me-Hg to T-Hg in the hairs of the common people and control group was only 12.4% on average, illustrating the impact of Hg vapor from artisanal mining activities. Comparing with control group, the residents in Guizhou Hg mining areas had a higher Me-Hg concentration in their hairs. The daily Me-Hg intake through rice consumption by parts of the residents in Guizhou Hg mining areas exceeded the JECFA-recommended value (0.23 μg·d^-1·kg^-1), and that for a majority of the residents exceeded the USEPA-recommended value (0.10 μg·d^-1·kg^-1). The residents in Gouxi and Laowuchang of Tongren areas were at a health risk of Me-Hg exposure through rice consumption, and those in other Hg mining areas were at a potential risk of Me-Hg exposure.

Mitigation effects of Vetiveria zizanioides and additives on surface runoff mercury concentration from mercury-contaminated soil and slag under simulated rainfall.

2011, 30(05):  922-927. 

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A pot experiment with simulated rainfall was conducted to study the mitigation effects of Vetiveria zizanioides and additives (sawdust and humus soil) on the surface runoff mercury concentration from Hg-contaminated soil and slag. In the surface runoff, particle mercury accounted for 80% of the total mercury, being the leading form of mercury transported to environment. Planting V. zizanioides on the Hg-contaminated soil or applying V. zizanioides mixed with sawdust or humus soil into the contaminated soil could effectively reduce the total mercury, particle mercury, and dissolved mercury transportation to environment by 63%-85%, 63%-85%, or 27%-73%, respectively, and the effect was significantly higher than that of applying single sawdust (5%) or humus soil (23%) into the contaminated soil. Applying background soil or sawdust into the Hg-contaminated slag, planting V. zizanioides on the slag, or applying V. zizanioides mixed with background soil, sawdust, or humus soil into the slag could effectively fix the total mercury, particle mercury, and dissolved mercury in slag by 29%-82%, 27%-84%, or 20%-70%, respectively.

Effects of flue gas mercury emission from two coal-fired power plants in Shanghai on peripheral environment.

2011, 30(05):  928-932. 

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Samples of top soil and air around two coal-fired power plants in Shanghai were collected, and their mercury (Hg) concentrations were determined, aimed to study the effects of flue gas Hg emission from the power plants on their peripheral environment. An atmospheric dispersion model was used to predict the ground level concentration of Hg dispersed continuously down from the point source of high stack. The Hg concentrations in the air around power plants G and J were 9.7-15.6 ng·m^-3 and 15.2-22.9 ng·m^-3, the ground level concentrations of gaseous element Hg were 0.218 ng·m^-3 and 3.034 ng·m^-3, and the ground level concentrations of particulate Hg were 0.038 ng·m^-3 and 1.199 ng·m^-3, respectively. The Hg concentrations in the top soils around power plants G and J were 36.3-136.5 ng·g^-1 and 44.3-115.9 ng·g^-1, and the Hg concentrations in plant leaves were 215.3-342.3 ng·g^-1 and 223.4-396.9 ng·g^-1, respectively. Both the field monitoring and the model estimate showed that the flue gas emission from the coal-fired power plants contributed to the distribution and accumulation of Hg in the peripheral environment.

Distribution characteristics of mercury in precipitation of Guiyang, China.

2011, 30(05):  933-938. 

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A study of the daily event precipitation in Guiyang was taken between July and September, 2008. The average concentration of total Hg (THg) in daily event precipitation was 18 ng·L^-1 with a range from 0.4 to 57.4 ng·L^-1; the average concentration of methyl Hg (MeHg) in daily event precipitation was 0.07 ng·L^-1, with a range from 0.02 to 0.2 ng·L^-1. The main inorganic ions were SO^2-₄, NO^-₃, Ca²⁺, NH₄⁺, and Mg²⁺. The average concentrations of SO^2-₄ and NO^-₃ were 151 mol·L^-1 and 145 mol·L^-1, respectively. The average concentration of Ca²⁺ was 123 mol·L^-1 with a range from 3.7 mol·L^-1 to 560 mol·L^-1. The average concentrations of NH₄⁺ and Mg²⁺ were 52.2 mol·L^-1 and 20.4 mol·L^-1, respectively. According to the relationships between the concentrations of THg and inorganic ions, we identified that the possible sources were fossil fuels burning.

Atmospheric total gaseous mercury concentration in Guiyang: Measurements intercomparison with Lumex RA-915AM and Tekran 2537A.

2011, 30(05):  939-943. 

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From May 12 to June 19, 2010, a high-time resolution observation on the atmospheric total gaseous mercury (TGM) concentration in an urban area of Guiyang was continuously conducted by using Lumex RA-915AM (made in Russia) and Tekran 2537A (made in Canada). Though the two sampling instruments have distinct operation principles, the overall characteristics and temporal distribution patterns of measured atmospheric TGM concentration were quite consistent, indicating that both of the instruments could accurately measure the atmospheric TGM concentration. The atmospheric TGM concentration in Guiyang was much higher than the mean global background value, and also, higher than the atmospheric TGM concentration in urban areas of Europe and North America. The preliminary sources identification suggested that the point source mercury emission from domestic activities played an important role in affecting the atmospheric TGM concentration in Guiyang, and some large factories located at the east of Guiyang were also the important sources to the regional atmospheric mercury.

Mercury pollution from automobile exhaust in Guilin City.

2011, 30(05):  944-950. 

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Atmosphere, soil and vegetable samples (56 for each) were collected along 4 highway profiles in Guilin suburbs to analyze the mercury (Hg)concentration, aimed to understand the situation of Hg pollution from automobile exhaust in the suburbs. The Hg concentration along the highway profiles all exhibited a symmetrical single-peaked distribution, and the diffusion range of automobile exhaust Hg was approximately 200 m. The soil and vegetable Hg had close relations with atmosphere Hg, and the automobile exhaust Hg contamination degree of the highway profiles increased with increasing road age and vehicle flow. The Hg contamination of the highway profiles was considered to be mainly come from the Hg in fuel oil. According to the National Soil Environmental Quality Standard of China for non-pollution vegetables, the Hg concentration in 48% of the soil samples was above its maximum allowable concentration. The Hg concentration in the vegetables along the Guiyang highway profile was 10-70% times higher than the threshold value (0.29±0.03 μg·g^-1) of the National Standard for non-pollution agricultural products. This study showed that the highway profiles in Guilin were moderately contaminated by mercury.

Distribution of total mercury and methylmercury in two hydroelectric reservoirs of Guizhou Province, China.

2011, 30(05):  951-960. 

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To investigate the distribution of mercury (Hg) and characteristics of its methylation in Wujiangdu (WJD), a reservoir with a high level of primary productivity, and in Yinzidu reservoir (YZD) with a low level of primary productivity, a fully adequate set of Hg species in water samples from a depth profile near of the dam in both reservoirs and from interface water in WJD were analyzed during winter (January 2007), spring (May 2007), summer (August 2007), and autumn (November 2007). The results showed that no significant difference was found between the levels of total mercury (THg), dissolved mercury (DHg), particulate mercury (PHg), reactive mercury (RHg) in WJD and YZD. Elevated MeHg concentrations in water samples from the bottom and water/sediment interface demonstrated an active net Hg methylation near the dam of WJD during all the sampling periods. There was no discernable Hg methylation occurring in the YZD during our sampling seasons. Results indicate that the primary productivity is an important indicator of Hg methylation in reservoirs.

Distribution of different mercury forms of Hongjiadu Reservoir from Guizhou Province.

2011, 30(05):  961-968. 

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We studied the concentration of different mercury (Hg) species in Hongjiadu Reservoir within Guizhou Province, China, and discussed the distribution and speciation of different Hg species and the mechanism of methylmercury (MeHg) production in the water column in Hongjiadu Reservoir. The results showed that total Hg (THg) concentration ranged from 0.32 to 6.75 ng·L^-1, dissolved Hg (DHg) concentration was between 0.23 and 2.27 ng·L^-1, particulate Hg (PHg) concentration ranged from 0.03 to 4.51 ng·L^-1, total MeHg (TMeHg) concentration ranged from 0.04 to 0.18 ng·L^-1, dissolved MeHg (DMeHg) concentration ranged from 0.02 to 0.08 ng·L^-1, particulate MeHg (PMeHg) concentration ranged from 0.01 to 0.13 ng·L^-1. The concentrations of different Hg species changed with season. In summer and autumn, THg, DHg and PHg concentrations were significantly higher than in spring and winter. In spring and summer, TMeHg, DMeHg and PMeHg concentrations were significantly higher than in autumn and winter. Spatially, total MeHg levels did not increase with depth in water column, nor did MeHg levels increase spatially, from upstream to the dam. Total MeHg concentration in water column of Hongjiadu Reservoir was much lower than those reported (range: 0.01-6.6 ng·L^-1) in North America and Europe. Hongjiadu Reservoir did not show the obvious characteristics of Hg methylation in water column, which was correlated with the low levels of nutrient and organic matter in flooded soil.

Spatial and temporal distribution of mercury species in water in Yelanghu Reservoir.

2011, 30(05):  969-975. 

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A study was conducted during July 2006, January 2007 and March 2007 to determine the distribution of mercury species (total Hg (THg), dissolved Hg (DHg), particulate Hg (PHg)) and the impacts of some major controlling factors in the Yelanghu Reservoir, Guizhou, China. By comparison, the average concentrations of THg (4.48±2.59 ng·L^-1), DHg (2.37±1.40 ng·L^-1), PHg (2.11±1.86 ng·L^-1) in the summer campaign are significantly higher (P<0.001) than those in the winter and spring campaigns, while no significant differences of concentrations of different mercury species are found between the latter two campaigns. Our investigation revealed that SPM and NO^-₃ may play an important role in controlling the seasonal distribution of mercury species in the reservoir. It is assumed that higher concentrations of mercury species in the summer could be a result of runoff impact. High runoff volume due to abundant precipitation in the summer carried Hg-containing particulates eroded from the agriculture-dominated watershed into the reservoir. Spatial distribution reveals that mercury concentrations generally decreased from the reservoir inlet to the outlet, while no notable vertical trends were found at each sampling site.

Distribution patterns of total mercury and methyl mercury in Aha Reservoir sediment.

2011, 30(05):  976-980. 

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In order to make clear whether the sediment in Aha Reservoir was contaminated by the mercury (Hg) from mining wastewater drainage, an investigation was conducted on the vertical distribution patterns of total Hg (THg) and methyl Hg (MeHg) in the sediment. The THg concentration in the sediment ranged from 160 to 252 ng·g^-1, with an average of 210 ng·g^-1, being obviously higher than that in uncontaminated lakes. The THg concentration increased with sediment depth, which was related to the sediment environment. The MeHg concentration varied from 0.2 to 7.2 ng·g^-1, with an average of 1.8 ng·g^-1. In the period with abundant water, the MeHg concentration decreased with sediment depth, and that in sedment surface layer was obviously higher, as compared in low water period, which was related to the increased organic matter content and anaerobic enviroment in sedment surface layer in abundant water period.

Distribution characteristics and pollution assessments of heavy metals in Dongjiang river sediments.

2011, 30(05):  981-986. 

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Heavy metals in sediments from Dongjiang River were detected by ICP-MS. The results showed that the distribution characteristics of these heavy metals, including Cu, Zn, Cd, Hg, were similar, and the sites with higher and lower value were approximately in accordance. Cu, Zn, Cd, Hg, Pb were the main heavy metal pollutants. The average contents of these heavy metals in the sediments were 157.29, 213.21, 0.98, 0.42, 50.77 mg·kg^-1 respectively, which exceeded the sediment background value in China. The degree of pollution was evaluated by the index of geoaccumulation and the index of the Hakanson ecological risk. The results showed that the geoaccumulation of the pollutants in Dongjiang River was in the order: Cd, Cu, Zn, Hg, Pb, while the ecological risk degree of the pollutants was in the order: Hg, Cd, Cu, Pb, Zn. On the whole, in Dongjiang River, the potential ecological risk of sediments from upstream (Heyuan) was at low level, middle stream (Huizhou) at relatively high level, and downstream (Dongguan) at very high level.

Temporal and spatial distribution of mercury in the rivers from the Changbai Mountain area.

2011, 30(05):  987-992. 

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The temporal and spatial distributions of mercury in river water in the Changbai Mountain area were studied. Total mercury and methylmercury were measured in water samples collected in both low flow period and flood period from Changbai Mountain forest area. The results show that total mercury concentrations varied from 2.0 to 20 ng·L^-1 and were higher in low flow period than those in flood period due to local coal combustion for domestic heating in winter. Methylmercury concentrations ranged from 0.12 to 0.55 ng·L^-1 and were almost comparable between the different periods. Mercury concentrations were decreased with increase of altitude. The influence of the Songhua River in which several rivers flow into was evident, dissolved mercury decreased and particulate mercury increased with river inflow. Compared to other forest rivers worldwide, methylmercury concentrations were relatively lower, however, total mercury concentrations were higher. The estimated output of THg and MeHg to downstream in study area was 33 kg·a^-1 and 200 g·a^-1 respectively, which further increase the downstream loads of mercury.

Spatiotemporal variation of mercury in sediments of Wulihe River, Liaoning Province.

2011, 30(05):  993-997. 

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Sediment samples were collected from the Wulihe River historically contaminated by chlor-alkali production in Huludao City, Liaoning Province, aimed to study the past 25 years spatiotemporal variation of total and methyl mercury in the River. Under 25-year artificial management and natural purification, the total and methyl mercury contents in the sediments collected from different segments showed an overall decreasing trend, being more obvious for methyl mercury, but the total mercury content was still quite high (0.491-26.395 mg·kg^-1, averagely 13.766 mg·kg^-1), 371 times higher than the background value (0.037 mg·kg^-1) of soils in the Province. The methyl mercury content was in the range of 0.253-12.079 mg·kg^-1. The segments with heavy mercury-contamination were at the Hugong Bridge near to pollution source and the North Cishan Bridge near to the downstream estuarine.

Effects of land use change on mercury content in Sanjiang Plain wetland.

2011, 30(05):  998-1003. 

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This paper analyzed the mercury (Hg) content in the soils of Doyeuxia augustifolia marsh, corn field, and lowland rice field and in the plants of D. augustifolia, Carex meyeriana, C. lasiocarpa, poplar, and moss in Sanjiang Plain, aimed to approach the sources and distribution characteristics of soil and plant Hg in the Plain as well as the effects of land use change on the soil Hg content. The total Hg content in the soils was in the range of 0.006-0.208 mg·kg^-1, with an average of 0.053 mg·kg^-1, which was higher than the background value of the soils in Heilongjiang Province. From the top layer to the bottom, the Hg content in the soils changed little in D. augustifolia marsh, but varied greatly in corn field and lowland rice field. The Hg content in the plants was in the order of moss > C. meyeriana > D. augustifolia > C. lasiocarpa> poplar, among which, the Hg content in moss was up to 0.132 mg·kg^-1. Correlation analysis suggested there was a significant positive relationship between soil Hg and dissolved organic carbon (r=0.269, P<0.05). Atmospheric dry and wet deposition and the plant uptake of atmospheric Hg could be the main Hg sources for the marsh. After the marshland was reclaimed into cropland, the soil Hg content was decreased by 45.6%, but after the upland field was changed into lowland field, the soil Hg content was increased by 18.3%.

Mercury distribution and speciation in the sediments of mangrove wetland in Quanzhou Bay.

2011, 30(05):  1004-1007. 

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Surface sediments were sampled from the mangrove wetland in Quanzhou Bay to study the distribution, speciation, and bio-availability of mercury in the sediments. The total mercury content in the sediments ranged in 0.03-0.22 mg·kg^-1, which met the first class standard of Marine Sediment Quality (GB 18668-2002), with the exception of that at site 14. The average proportion of different speciation mercury to total mercury in the sediments presented a sequence of oxidizable (84.0%) > residual (14.0%) > reducible (1.8%) > weak acid soluble (0.2%). The relatively high bio-availability of mercury in the sediments indicated certain potential hazard to the mangrove ecosystem.

Mercury concentration and biological quality index of major fish species from Dongzhaigang mangrove forest area of Hainan.

2011, 30(05):  1008-1012. 

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Mercury can threat human health through fish enrichment. In order to understand the mercury concentration and biological quality of major fish species in Dongzhaigang mangrove forest area of Hainan, this paper analyzed the mercury concentrations of 14 main fish species and different environmental media in this forest area. It was detected that the mercury concentration in fish muscle was 34.9-154.9 ng·g^-1, with an average of 67.7 ng·g^-1, and that in sea water, mangrove leaves, and sediments was 0.4 μg·L^-1, 153.9 ng·g^-1, and 314.1 ng·g^-1, respectively. Relative to sea water, the fishes enriched more mercury from the environment. The mercury concentration in the fishes was related to their food sources and living habits. Omnivorous fish had higher mercury concentration than herbivorous fish and carnivorous fish. All the fishes had the biological quality index lower than 1, being safe as foods.

Impacts of mercury stress on Avicennia marina seedlings eco-physiology.

2011, 30(05):  1013-1017. 

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In order to understand the heavy metals resistance mechanism of mangrove, a stress experiment with the seedlings of mangrove species Avicennia marina from Fujian Province was conducted to study the impacts of different concentration (1, 5, 10, 50, and 100 mg·L^-1) mercury (Hg²⁺) on the seedlings leaf photosynthesis and antioxydase activities. With the increase of added Hg²⁺ concentration and exposure time, the seedlings leaf net photosynthetic rate (P_n) and chlorophyll content decreased. Under the stress of high concentration Hg²⁺ (≥50 mg·L^-1), the decrement of P_n was higher than that under the stress of low concentration Hg²⁺, and the P_n decreased rapidly after 48 h. There was a significantly negative correlation between P_n and extracellular carbon dioxide concentration (C_i). The chlorophyll content decreased with increasing  Hg²⁺ concentration. The stomatal conductance (G_s) had different responses to the stress of different  Hg²⁺ concentration. At low  Hg²⁺ concentration, stomatal factors could limit the photosynthesis; while at high  Hg²⁺ concentration, non-stomatal factors could be the main causes inhibiting photosynthesis. Low  Hg²⁺ concentration promoted the activities of superoxide dismutase and peroxidase, while high  Hg²⁺ concentration inhibited the activities of the two enzymes, being the lowest under the stress of 100 mg Hg²⁺·L^-1. All the results implied that Hg²⁺ could inhibit the leaf photosynthesis of A. marina, and high concentration Hg²⁺ impaired the active oxygen elimination capability of A. marina, making the plants easily to be damaged.

Pollution characteristics of atmospheric black carbon in Guiyang City, Southwest China.

2011, 30(05):  1018-1022. 

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By using URG Model 2000-01J and Aethalometer, the atmospheric black carbon concentration in Guiyang City was continuously detected from September to November, 2008. The 24 h atmospheric black carbon concentration during the detection period was 1.6-12 μg·m^-3, with a mean value of 4.1 μg·m^-3. The 12 h atmospheric black carbon concentration was mainly in the range of 2-5 μg·m^-3, its daytime variation range was 1.9-9.2 μg·m^-3, with a mean value of 3.9 μg·m^-3, and its nighttime variation range was 0.48-15 μg·m^-3, with a mean value of 4.3 μg·m^-3. The atmospheric black carbon concentration had the same variation trend as atmospheric PM_2.5 concentration, and there existed a positive correlation (r=0.84, P<0.0001, n=178) between them. The variation trend of the atmospheric black carbon concentration was also affected by the relative humidity, temperature, and wind speed.

Chlorophyll-a distribution and phosphorus cycle in water body of Hongfeng Reservoir, Guizhou.

2011, 30(05):  1023-1030. 

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In August (summer) 2009 and January (winter) 2010, water and sediment samples were collected from Hongfeng Reservoir in Guizhou to analyze the total nitrogen (TN), total phosphorus (TP), phosphate (PO^3-₄), and chlorophyll-a (Chl-a) in water body and the dissolved phosphorus (DP) in sediment pore water. The mean TN concentration in water body was 1.58±0.73 mg·L^-1, and no obvious difference was observed between summer and winter. The mean TP concentration in water body was higher in summer (0.091±0.070 mg·L^-1) than in winter (0.026±0.055 mg·L^-1). In summer, the lake water at the depth 8 m was thermally stratified, with the TN and TP concentrations being higher in hypolimnion than in thermocline. The Chl-a in water body was mainly concentrated in thermocline, with a mean concentration 33.2±13.0 mg·m^-3 in summer and 11.1±3.7 mg·m^-3 in winter. There was a significant positive linear correlation between Chl-a and TP in the upper 8 m water layer (r=0.965,P<0.01), suggesting that the eutrophication of Hongfeng Reservoir was limited by phosphorus. The DP concentration in sediment pore water and the phosphate (PO^3-₄-P) concentration in water body were much higher than the PO^3-₄-P concentration in overlying water, which meant that the DP had a strong upward diffusion tendency. According to Fick’s first law, the phosphorus emission flux from sediment to overlying water was calculated. The phosphorus emission rate was higher in summer than in winter, possibly because the bottom anoxic water environment and its higher temperature in summer favored the formation of DP during the early diagenesis. Based on the phosphorus flux from sediment to overlying water, the annual phosphorous emission from sediment to water body was estimated as 5.0±5.6 metric tons. It was suggested that the eutrophication of Hongfeng Reservoir was controlled by phosphorous, and the sediment had a great potential in releasing phosphorous, being an important inner source of lake water phosphorous. To control the eutrophication of Hongfeng Reservoir, more strict policy was necessary to limit the anthropogenic phosphorous input from the watershed.

Temporal and spatial characteristics of phytoplankton community in Wanfeng Reservoir.

2011, 30(05):  1031-1038. 

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To understand the temporal and spatial characteristics of phytoplankton community structure in Wanfeng, a deep altiplano reservoir, phytoplankton was measured in September, 2009 and January, 2010. Forty-nine species of algae were identified. In summer the community was dominated by Cylindrospermopsis rackiborskii at the surface (0-10 m) and at the bottom (>60 m) Synedra ulna and Cyclotella meneghiniana became dominant, but in winter the community was dominated by Synedra ulna and Cyclotella meneghiniana. The phytoplankton abundance ranged from 13.0×10⁴ to 54.6×10⁴ cells·L^-1 in summer and 17.43×10⁴ to 25.28×10⁴ cells·L^-1 in winter. The maximum phytoplankton abundance was at Yeyatang (S2), but the minimum phytoplankton abundance was at Baai (S4). In summer, phytoplankton collected at the surface (0-10 m) was primarily composed of cyanophyta. The highest percent composition of cyanophyta was 90.3% at Daba (S1). Shannon diversity index was higher in summer than in winter, but the evenness was lowest at the surface in summer. In winter, phytoplankton mainly distributed at the surface (0-10 m) and at the mid-level (10-50 m), and was primarily composed of bacillariophyta. The percent composition of bacillariophyta was above 90% in all water layers. Judged by phytoplankton community structure and abundance, Wanfeng Reservoir is mesotrophic in summer. Water quality was better in winter than in summer. A relationship between phytoplankton abundance, temperature, and water depth was obvious in winter and summer.

Impacts of seasonal thermal stratification on the water environment of Wanfeng Lake.

2011, 30(05):  1039-1044. 

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The water temperature and hydrochemical parameters during September 2009 and January 2010 of Wanfeng Lake in Guizhou Province were surveyed. A clear thermal stratification was found at the vertical profile of water column in autumn and winter.  In autumn, a double thermocline appeared, which effectively limited the convective mixing of upper, intermediate and bottom of the layer water, caused water and water chemistry layed significantly.  In winter, with the decreasing temperature of upper layer water, because the subsidence of the upper water due to the density changing, the water stratified structure changed, and convection exchange appeared between the upper and the bottom water, so the reducing matter released by anaerobic digestion was brought into the upper layer water. Seasonal thermal stratification played an important role in water quality and environmental change of Wanfeng Lake. Correlation analysis shows that, in Wanfeng Lake, the water temperature was significantly correlated with hydrochemical parameters (DO, pH, and total phosphorus) in September of 2009 and January of 2010, thus water chemistry layered with the temperature stratification synchronization.