Distribution of and Temporal Variation in Volatiles in Tea (Camellia sinensis) Flowers during the Opening Stages

Tea (Camellia sinensis) flowers emit a large amount of volatiles that attract pollinators. However, few studies have characterized temporal and spatial variation in tea floral volatiles. To investigate the distribution of volatiles within tea flowers and their variation among opening stages, volatile components from different parts of tea flowers and different opening stages were collected by headspace solid-phase microextraction and analyzed by gas chromatography-mass spectrometry. A total of 51 volatile compounds of eight chemical classes were identified in the tea flowers. Volatile compounds were most abundant in tea flowers of the Shuchazao cultivar. Acetophenone, 1-phenylethanol, 2-phenylethanol, and benzyl alcohol were the most abundant volatiles. Terpenes were common in the sepals, and benzoids were common in the stamens. The fatty acid derivatives were mainly distributed in the pistils and receptacles and were less abundant in the petals, sepals, and stamens. During the opening phase of tea flowers, the volatile content increased 12-fold, which mainly stemmed from the increase in benzoids. These results enhance our understanding of the formation of volatiles in tea flowers.

Occurrence, Sources, and Health Risks of Polycyclic Aromatic Hydrocarbons in Road Environments from Harbin, a Megacity of China

To obtain a comprehensive understanding about that occurrence, sources, and effects on human health of polycyclic aromatic hydrocarbons (PAHs) in road environmental samples from Harbin, concentrations of 32 PAHs in road dust, green belt soil, and parking lot dust samples were quantified. The total PAH concentrations ranged from 0.95 to 40.7 μg/g and 0.39 to 43.9 μg/g in road dust and green belt soil, respectively, and were dominated by high molecular weight PAHs (HMW-PAHs). Despite the content of PAHs in arterial roads being higher, the composition profile of PAHs was hardly influenced by road types. For parking lot dust, the range of total PAH concentrations was 0.81-190 μg/g, and three-ring to five-ring PAHs produced the maximum contribution. Compared with surface parking lots (mean: 6.12 μg/g), higher total PAH concentrations were detected in underground parking lots (mean: 33.1 μg/g). The diagnostic ratios of PAHs showed that petroleum, petroleum combustion, and biomass/coal combustion were major sources of PAHs in the samples. Furthermore, according to the Incremental Lifetime Cancer Risk model, the cancer risks of three kinds of samples for adults and children were above the threshold (10-6). Overall, this study demonstrated that PAHs in the road environment of Harbin have a certain health impact on local citizens.

[Spatio-temporal dynamics of gross primary productivity in China from 1982 to 2017 based on different datasets]

Understanding the spatio-temporal variations of gross primary productivity (GPP) of terrestrial ecosystem and its relationship with climatic factors can provide important basis for vegetation restoration and protection. Based on meteorological data and three public GPP datasets (EC-LUE GPP, GLASS GPP, and NIRv GPP), we syste-matically analyzed the spatial-temporal variations of GPP and its response to climate change in China during 1982-2017. All the results based on the three GPP datasets showed that the annual and seasonal GPP in China increased annually from 1982 to 2017, with that in 1998 and 2002 significantly being higher than the average level during the study period, and that in 1989 and 1992 significantly being lower than the average annual GPP. From 1982 to 2017, GPP showed a significant upward trend in most regions of China, with the regions with significant increases accounting for 75.7%, 73.0%, and 69.6% of the whole study area, respectively. There was a significant positive correlation between annual GPP and precipitation and temperature, but spatial heterogeneity was strong. Among them, the regions with positive correlation between GPP and temperature were mainly distributed in Northwest and Central China, while the regions with positive correlation between GPP and precipitation were mainly distributed in North China. There was obvious spatial-temporal heterogeneity in regions that GPP being affected by temperature and precipitation in different seasons. Temperature was the limiting factor of GPP in spring, autumn and winter, while summer GPP was mainly affected by precipitation.

[Source Apportionment of PM2.5 Based on Hybrid Chemical Transport and Receptor Model in Chongqing]

In order to further improve the accuracy of fine particulate matter (PM_2.5) source apportionment results, a hybrid source apportionment approach (CTM-RM) combining the capabilities of a receptor model (RM) and chemical transport model (CTM) was developed. The CTM-RM method was evaluated and applied according to a typical PM_2.5 pollution process from January 21 to 27, 2019 in Chongqing. The average value of square prediction error based on CTM-RM was 84.58% lower than that of CAMx/PSAT during the campaign. Compared with that of CAMx/PSAT, the fractional error of PM_2.5 and its chemical component concentrations decreased by 15.69%-92.86%. Furthermore, the temporal and spatial variations in PM_2.5 source impacts could be obtained using the CTM-RM method in Chongqing. The average adjustment factor (R) values were 1.39±0.38 (agriculture sources), 1.54±0.48 (industrial sources), 1.01±0.13 (power sources), 1.02±0.58 (residential sources), 0.86±0.59 (transportation sources), and 0.58±0.67 (other sources) in the main urban areas of Chongqing. Additionally, the cumulative distribution functions of R were found to be distinct among the six sources. The residential and industrial sources were the main sources of PM_2.5, with contributions of 46.23% and 28.23%, respectively. In contrast to that of the other sources, the transportation source impacts of PM_2.5 (8.62%) increased significantly from the clear period to pollution period (P<0.001), indicating that the increase in PM_2.5 concentrations was mainly driven by vehicular emissions during the pollution period in the main urban areas of Chongqing. The fitting functions between the initial simulated concentrations and R values of each source in the main urban areas of Chongqing could be used to evaluate PM_2.5 concentrations at 47 air quality monitoring stations in Chongqing, and the correlation between the refined simulated concentrations and measured concentration of PM_2.5 was significant (r=0.82, P<0.001). Compared with that during the clear period, the increases in the percentages of industrial source impacts of PM_2.5 in Northeast Chongqing and residential source impacts of PM_2.5 in Southeast Chongqing were 17.20% and 9.15% higher, respectively, than that in other areas during the pollution period. By contrast, the increasing percentage of transportation source impacts of PM_2.5 in the main urban areas of Chongqing (66.39%) and Western Chongqing (84.16%) from the clear period to the pollution period were higher than that in other areas. The results of CTM-RM on January 26 indicated that the residential source impacts in Northeast Chongqing (64.56%) were higher than those in other areas, and the industry source impacts of PM_2.5 were primarily observed in the main urban areas of Chongqing and Western Chongqing, with contributions of 25.26% and 21.20%, respectively.

[Temporal and Spatial Variation Characteristics and Source Analysis of Agricultural Non-point Source Pollution Load in Guangdong During the Past 20 Years]

The agricultural non-point source pollution (ANPSP) load in Guangdong province is very large and has a serious impact on the regional ecological environment. Inventory analysis was used to assess and analyze the temporal and spatial variation characteristics of the ANPSP load of Guangdong province during 1999-2019, and the sources of ANPSP were discussed, as well as the relationship between them. The results showed that, during the past 20 years, the total ANPSP pollution loads of Guangdong province decreased by 6.08%, and the pollution loads of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) increased by -11.88%, 4.99%, and 26.17%, respectively. The input intensity of chemical fertilizers and pesticides increased by 112.19% and 60.38%, respectively. The Pearl River Delta had the highest ANPSP loads in Guangdong province, followed by those in northern, western, and eastern Guangdong. Livestock and poultry breeding were the main sources of COD, the total percent fertilizers and livestock and poultry breeding were the main sources of TN, and livestock and poultry breeding and aquaculture were the main sources of TP. In addition, the contribution of pollutants discharged from aquaculture showed an obvious increasing trend. There were certain differences in the pollution sources in different regions. In western Guangdong, northern Guangdong, and eastern Guangdong, livestock and poultry breeding were the main sources of COD and TP, and fertilizer was the main source of TN; by contrast in the Pearl River Delta, aquaculture had become the main source of TN and TP pollution loads. The correlation results showed that the decline in the total ANPSP in Guangdong province was mainly due to the increase in high urbanization rate and the decrease in the proportion of rural population. In general, there were stage changes in the time and differences in spatial characteristics and sources of ANPSP in Guangdong province. A combination of comprehensive treatment and targeted pollution treatment should be adopted, and fertilizer reduction measures and pollution treatment in the aquaculture should be strengthened in an all-around way, focusing on strengthening the treatment of pollution from aquaculture in the Pearl River Delta region and the treatment of rural life pollution in northern Guangdong.

[Mercury in tree rings: Advances, problems and prospects]

As a highly biotoxic element, mercury (Hg) can be enriched by the food chain and has negative effect on ecosystems. Changes of Hg flux and reserves in forest have important effects on its biogeochemical cycle in forest ecosystem. Due to limitation of temporal and spatial monitoring, there is not comprehensive understanding on Hg distribution. Widely distributed trees can be used as effective bio-monitors and Hg records in tree rings can be used to study Hg temporal and spatial distribution. Hg accumulated by root, leaf, bark, and other tissues can be detained in bole and record environmental Hg variations. Therefore, historical Hg trends can be restructured by analyzing Hg concentration in tree rings and the biogeochemical characteristics can be understood with Hg isotope ratio. We reviewed the method of measurement of Hg concentration and isotope ratio and application of reconstruction using Hg concentration in tree ring. We suggested the great application potential of Hg isotope ratio in atmospheric Hg construction and biogeochemistry cycle and raised concerns in further studies.

[Spatio-Temporal Variation of Release Flux of Sediment Nitrogen and Phosphorus in High-Risk Period of Algal Bloom in Lake Erhai]

Spatial and temporal characteristics of release fluxes of sediment nitrogen (N) and phosphorus (P) were investigated in the high-risk period of algal blooms in Lake Erhai. Moreover, the influence factors were examined. Results show that the release flux of N and P increased in recent years, exhibiting a clear increase in the period from 2009 to 2013, and a slight increase in the period since 2013. The release flux of dissolved total nitrogen (DTN) ranged between 11.71-14.15 mg·(m²·d)^-1, within which the release flux of dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) were 6.39-8.42 mg·(m²·d)^-1 and 5.31-5.73 mg·(m²·d)^-1, accounting for 58% and 42% of the DTN, respectively. The release flux of dissolved total phosphorus (DTP) ranged between 0.11-0.14 mg·(m²·d)^-1, within which the release flux of dissolved organic phosphorus (DOP) and dissolved inorganic phosphorus (DIP) were 0.04-0.05 mg·(m²·d)^-1 and 0.07-0.09 mg·(m²·d)^-1, accounting for 34% and 66% of the DTP, respectively. The distribution of release flux of N showed a decreasing order:south > north > middle, while P was north > middle > south. The release flux of N increased by 17%, 13% and 23%, and the release flux of P increased by 19%, 28%, and 29% in north, middle, and south part of Lake Erhai from 2009 to 2018. Comparing the years 2009, 2013 and 2018, although the contents of N and P were stable, the release flux of N and P in the sediment was enhanced due to increasing pH and decreasing DO. Therefore, the increasing release of nitrogen and phosphorus from sediments, caused by changes in the water environment factors, should be paid attention to for the protection of Lake Erhai.

[Temporal and Spatial Variations in the Conductivity in Different Media in Taihu Lake, China]

Conductivity is an important parameter for characterizing dissolved solids and salinity in water, and is also one of the routinely measured parameters in water quality monitoring. To reveal temporal and spatial variations in conductivity in different media in Taihu Lake, historical data (1980-2009) were collected and field monitoring data (2009-2018) were analyzed. The results indicated that water conductivity in Taihu Lake has shown a significant increasing trend over the past 40 years and diverged in 1996-1997. Conductivity values increased from (239.43±70.60)μS·cm^-1 in the period 1980-1996 to(477.31±23.47)μS·cm^-1 in the present day, with an average annual increase of 10.40 μS·(cm·a)^-1. Spatially, the conductivity of water in the northwest part of the lake was significantly higher than the southeast part. These changes in conductivity are dominated by changes in major ions, and the contribution of nitrogen was essentially negligible. Human activities in the basin have been the main factors causing changes in water conductivity. In addition, conductivity is significantly affected by seasonal runoff. Compared with the water, the conductivity of the surface sediments and pore water (0-10 cm) in the northwest part of the lake were lower than in the southeast part, while this trend was opposite in the deeper sediments (>10 cm). The conductivity of the sediment and pore water were no different between surface (0-10 cm) and deeper (>10 cm) sediments in the northwest lake, while these were higher in the surface sediments in the southeast part of the lake. Sediment conductivity was positively correlated with organic matter (P<0.01) and was negatively correlated with pH (P<0.05). This indicated that organic matter promotes the activation and migration of metal ions, which are more activated under acidic conditions. We found that conductivity in the surface sediments and pore water (0-10 cm) were significantly positively correlated with conductivity in the overlying water (P<0.01). In contrast, the conductivity of overlying water was not correlated with the conductivity of deeper sediments and pore water (>10 cm). These patterns indicated that surface sediments and pore water have a significant effect on the conductivity of overlying waters. In addition, there was a significant positive correlation between the conductivity of sediment and pore water (P<0.01) within the entire sedimentary section (0-50 cm), indicating efficiency ion-exchange between the two. The interaction between sediment and pore water was generally stronger than their interaction with the overlying water.

[Spatial and temporal changes of farmland soil acidification and their influencing factors in different regions of Guangdong Province, Chin]

Based on the three datasets from 1980s, 2010 and 2015 in Guangdong Province, we analyzed the spatial and temporal variations of soil pH in farmlands in different regions of Guangdong Province and analyzed the driving factors for such variations. The results showed that the spatial distribution of soil pH in Guangdong Province changed significantly in different periods. During 1980s to 2010, soil pH showed an acidification trend with a decline of 0.3, and increased by 0.09 from 2010 to 2015, with more uneven trend and more obvious acid base differentiation. From the perspective of each region, there was generally a trend of acidification from the 1980s to 2010. From 2010 to 2015, the average pH value of farmland soil in the Pearl River Delta increased by 0.27, while that on the east wing and west wing decreased by 0.05 and 0.15 respectively, showing a unapparent change of soil pH in the mountainous area. Our results showed that soil acidification in diffe-rent areas of Guangdong Province was affected by natural factors such as soil itself and precipitation. In addition, anthropogenic factors such as acid rain, unreasonable fertilization and the planting structure of high-yielding crops were also the main causes of soil acidification. Industrialization, urbanization, mining development, and the spread of soil testing formula fertilization increased soil pH in local areas. Our results could provide theoretical guidance for controlling and alleviating soil acidification and improving the quality of cultivated land in different areas.

[Temporal and Spatial Characteristics of Heavy Metals in Suspended Particulate Matter in Pearl River Estuary and Its Influencing Factors]

Simultaneous sampling and observation were conducted at 16 stations in the Pearl River Estuary, and the temporal and spatial characteristics of the contents of six heavy metals (Cr, Cu, Zn, Pb, As, and Cd) were analyzed. The influencing factors of suspended particulate matter (SPM) were explored through the combined results of our statistical analyses. With the influence of discharge, temperature and particle size, the content of heavy metals in the dry season is higher than that in flood season. Regarding the estuary filter, the content of heavy metals in the estuary segment was lower than that in the far mouth segment, which was principally caused by the difference in salinity and sediment concentration between the two segments during the dry season. Both the sediment quality standard and enrichment factor methods were used to evaluate heavy metals. The results showed that the threat of heavy metals in the dry season was stronger than that in the flood season. As and Zn were more harmful to the ecological risk, while Cd, As, and Zn were the more abundant pollutants in the Pearl River Estuary. Heavy metal pollution was more severe in the far mouth segment. The degree of pollution for Cu, Zn, As, and Cd- which are classified as heavy pollution, severe to extremely heavy pollution, severe heavy pollution, and extremely heavy pollution, respectively-in the Beijiang River were higher compared to the Xijiang River and Dongjiang River. The pollution level of the six heavy metals in the four eastern outlets and four western outlets were similar, and the most serious pollution in Humen may be related to local industrial development. The source of heavy metals in SPM of the Pearl River Estuary is related to geological background, industry, and the mining area.

[Distribution and Sources of Polycyclic Aromatic Hydrocarbons in a Karst Groundwater System in a Strongly Industrial City]

To understand the spatiotemporal variation characteristics and sources of polycyclic aromatic hydrocarbons in karst groundwater in a strongly industrial city, the authors collected 23 groundwater samples in the water and dry period in Liuzhou using component spectra of 16 types of polycyclic aromatic hydrocarbons in combination with the physical and chemical properties and analyzed the spatiotemporal variation characteristics and sources of the polycyclic aromatic hydrocarbons (PAHs) in karst groundwater in heavy industrial city. The results show that the average concentration of ∑PAHs in the groundwater in the wet period has an order of Liubei District > Liudong District > Liuxi District > Jila Underground River and the concentration proportion of PAHs decreases with the increase of the molecular weight, while the order in the dry period is Jila Underground River > Liubei District > Liuxi District > Liudong District. The PAHs in the groundwater during the dry season have a high pollution level, while a low pollution level is observed in the wet season. The main sources of PAHs are organic matter burns at high temperature such as fossil fuel, which are produced by human activities such as industrial processes, transportation, heating, and cooking.

[Temporal and Spatial Distribution of the Soil Water δD and δ18O in a Typical Karst Valley: A Case Study of the Zhongliang Mountain, Chongqing City]

In this study, we analyzed the stable hydrogen and oxygen isotopes of precipitation and three different land use patterns (cultivated land, grass land, and forest land) at 0-15 cm and 15-45 cm in a karst ridge-trough area (Zhongliang Mountain, Beibei District, Chongqing) in May 2017 and September 2017 to investigate the spatial and temporal variation of stable isotopes in different soil profiles using the isotope tracer technique. The results show that:① The average values of the soil water δD and δ¹⁸O are -50.0‰±33.6‰ and -7.9‰±4.3‰, respectively, and all plot around the local meteoric water line (LMWL), indicating that precipitation is the main source of the soil water supply in this area. ② The seasonal variations of δD and δ¹⁸O of the soil water are significant in different months of the rainy season, May (-19.4‰±6.8‰ and -4.1‰±1.0‰)>September (-82.2 ‰±14.0‰ and -11.9‰±2.2‰). ③ However, there is no significant difference in the soil water δD and δ¹⁸O under different land use patterns. ④ The soil water δD and δ¹⁸O change with soil depth gradients, which decrease along the depth in vertical direction for all types of soil land use in May but mainly increase/decrease in the cultivated land and woodland/grassland in September, respectively.

[Pollution Characteristic of Ni in Sediments in the Three Gorges Reservoir]

The Three Gorges Reservoir (TGR) has achieved the target of water storage of 175 m for eight consecutive years until October 2017. To study the temporal and spatial variation of nickel (Ni) in different water periods under 175 m operating conditions in the TGR area, probe the impact of a large-scale water conservancy project on the Ni enrichment, and establish the pollution evaluation system of Ni in the TGR area, we collected 173 surface sediment samples from the TGR area during four consecutive water periods from December 2015 to June 2017 and measured the Ni concentration by using inductively coupled plasma mass spectrometry (ICP-MS). The mean values of Ni in the four water periods are higher than the background value of Yangtze sediment and soil. At the spatial scale, the Ni content in the mainstream exhibits a clear upward trend from upstream to downstream and is lower than that of the tributary. The tributaries of the lower reaches shows a notably higher Ni content than the tributaries of the upper and middle reaches. At the temporal scale, the water period exerts an insignificant effect on the Ni content. The Ni content is relatively stable and shows a downward tendency at a 175 m water level. The regional geochemical baseline (RGB) value of Ni was obtained through building a geochemical baseline model in the area. The RGB values of Ni in sediments during four consecutive water periods are 47.0, 44.2, 42.9, and 41.9 mg·kg^-1, respectively. The Ni contents in the middle and lower reaches of the mainstream and tributary are significantly affected by human activities. Moreover, the pollution evaluations based on global Ni background values, local background values, and geochemical baseline values as reference values were compared and the geoaccumulation index and potential ecological risk of Ni were determined to comprehensively assess its pollution risk. The assessment data indicate that Ni in the aquatic environment of the TGR area is almost uncontaminated and poses a low ecological risk, except for samples in regions around Fengdu County and Guizhou Town in the Zigui County along the mainstream, which were uncontaminated to moderately contaminated. Relative to global and regional background values, the pollution assessment results obtained using the RGB as a reference value are more scientific and better match the temporal and spatial variation of the study area.

[Effects of temporal and spatial variation of canopy structures and light conditions on population characteristics of Fargesia decurvata.]

The canopy structures and light conditions and the population characteristics of Fargesia decurvata, a dominant understory species, were investigated in three typical communities, i.e., deciduous broad-leaved forest, evergreen and deciduous broad-leaved mixed forest, evergreen broad-leaved forest. The results showed that with the succession from deciduous broad-leaved forest to evergreen and deciduous broad-leaved mixed forest and to evergreen broad-leaved forest, the Shannon index, Simpson index and Pielou index were increased, suggesting that the development of communities in Jinfo Mountains tended to be stable. Moreover, canopy structures were significantly changed, in that the canopy openness and mean leaf angle decreased, leaf area index increased, and canopy extinction ability enhanced, resulting in the decrease of light intensity under the canopy. The upper canopy was the main contributor for canopy closure, with the crown depth and crown area of canopy being the two main influencing factors. Moreover, canopy structures were significantly correlated with light conditions in the forest, with the greatest influence on the diffuse solar radiation. With the growth season coming, canopy openness and understory light conditions were decreased, while leaf area index increased, and their maximum values appeared in June or July in the three forest types. The maximum and minimum value of mean leaf angle appeared in spring and summer, respectively. Clonal growth of F. decurvata was closely related to canopy structures and light conditions. In evergreen and deciduous broad-leaved mixed forest with moderate light, F. decurvata grew best, with high and thick ramets, high ramet density (29.69±1.68 ind·m^-2) and high ability to expand rhizomes. In deciduous broad-leaved forest, the strong light condition caused the reduction of soil water might have effects on the growth of F. decurvata. However, in the evergreen broad-leaved forest with low light condition, ramets of F. decurvata tended to be short and thin, with low ramet density (5.80±1.16 ind·m^-2) and the clonal expansion ability. Those results suggested that forest succession would change canopy structures and understory light conditions. Low understory light conditions prohibited the regeneration and development of F. decurvata population.

[Evaluation of Temporal and Spatial Variation Characteristics of Nutrients in Surface Sediment in the Three Gorges Reservoir Area]

With the construction of the Three Gorges Dam, the river flow pattern and sediment dynamics are expected to be affected. As a consequence, the sediment traits could be impacted by these changes. The temporal and spatial variation characteristics of the nutrient content from 2000 to 2015 in surface sediment were analyzed in the main stream from Jiangjin to the dam site section of the Yangtze River and in the estuaries of the representative input tributaries of the Three Gorges Reservoir, such as the Jialing River, Yulin River, Wujiang River, Xiaojiang River, Daning River, and Xiangxi River. Then, the state of the pollution was assessed. Results revealed that the average concentrations of total phosphorus (TP) in the surface sediments of the main stream ranged from 678.2 to 928.6 mg·kg^-1, the average contents of total nitrogen (TN) ranged from 0.203% to 0.362%, the average contents of potassium ranged from 1.74% to 2.37%, and the average contents of organic matter ranged from 0.94% to 1.54%. The average concentrations of TP in the estuaries of the representative input tributaries ranged from 490.1 to 832.3 mg·kg^-1, the average contents of TN ranged from 0.257% to 0.495%, the average contents of potassium ranged from 1.69% to 2.32%, and the average contents of organic matter ranged from 1.21% to 2.27%. The concentrations of TP and potassium in the study sections were generally within background concentration ranges, while the concentrations of TN were obviously above background levels, and the concentrations of organic matter were obviously below background levels. The nutrient contents in the surface sediment did not display significant differences among the study sites; however, the distributions of different nutrient contents along the river varied widely. Although the nutrient contents in the surface sediments fluctuated somewhat during different flow periods, they were seemingly unaffected by the impoundment, since no obvious enrichment was observed throughout the impoundment. The evaluation of organic index indicated a clean state for the surface sediments in the majority of the study area, while there was a moderately polluted state in some local sections. The evaluation of nitrogen pollution indicated a polluted state for most sections. Overall, the nutrients in the surface sediments of the Three Gorges Reservoir showed moderate ecological risks, possibly caused by TP and TN.

[Characteristics Analysis of the Surface Ozone Concentration of China in 2015]

Surface ozone concentration data from 189 cities in China in 2015 were processed by ArcGIS software in order to obtain the characteristics of the surface ozone concentration, such as time and space, topographical features, temperature, etc. The trend for surface ozone concentration was a decrease followed by an increase in China in 2015. The concentrations during the four seasons followed the order:summer > autumn > spring > winter, and the maximum appeared in July. The ozone pollution of East China, South China, and North China were more serious than other regions in China. The variation of longitude had a small influence on the ozone concentration, while the influence of latitude is significant. According to the analysis contrasting three different topographies in the same latitude, the influence of topography on ozone concentration was negligible. Furthermore, the research found a significant positive correlation between surface ozone concentration and temperature.

[Temporal and Spatial Variation Characteristics of the Heavy Metals Content in the Surface Sediment and the Potential Ecological Risk Trends in the Three Gorges Reservoir Area]

With the construction progress of the Three Gorges Project, the hydrological situation of Three Gorges Reservoir changes greatly, which causes the changes of suspended solids precipitation conditions and surface sediment traits. This research analyzed the temporal and spatial variation of the heavy metal pollution in the surface sediment and the potential ecological risk trends during the years from 2000 to 2015 in the trunk stream of the Yangtze River from Jiangjin to the Three Gorges Dam area and some major tributaries, such as Jialing River, Yulin River, Wujiang River, Xiaojiang River, Xiangxi River. The results showed that the average content ranges of heavy metals (including Cu, Pb, Mn, As, Hg etc.) in surface sediments at the main stream monitoring sections during the study period were 46.5-85.7 mg·kg^-1(Cu), 43.8-65.1 mg·kg^-1(Pb), 784.2-910.6 mg·kg^-1(Mn), 8.44-11.91 mg·kg^-1(As), 0.193-0.236 mg·kg^-1(Hg) respectively; The average content ranges of the heavy metals in surface sediments at the main stream monitoring sections during the study period were 16.5-85.6 mg·kg^-1(Cu), 25.8-74.8 mg·kg^-1(Pb), 573.7-996.3 mg·kg^-1 (Mn), 6.96-13.31 mg·kg^-1 (As), 0.160-0.232 mg·kg^-1 (Hg) respectively. The results also showed that there were obvious differences of the heavy metals content in some areas between the left and right bank of the trunk stream of the Yangtze River in the Three Gorges Reservoir area. The results also showed that the concentration variation trends of the heavy metals were different in the surface sediments, such as Cu, Pb, Mn, As and Hg. The content of Hg was the most influenced element by the water period effect. The concentration variation trends of these elements were different at different monitoring sections during the construction and water harvesting progress of the Three Gorges project. The contents of Cu, Pb, Mn and As in sediment from the Three Gorges Reservoir area showed strong positive correlations between each other. But there was a low correlation between the content of As and those of other elements. There was no significant correlation between the content of Hg and those of other heavy metal elements. According to the geoaccumulation index analytical method, the contents of the heavy metals in surface sediments in the Three Gorges Reservoir area were generally at low enrichment level. But the pollution caused by Hg should be paid attention. The change of potential ecological risk index was small in the main stream and the major tributaries of the Yangtze River (except Wujiang River) in most of the time. It should also be noted that the change of potential ecological risk index fluctuated obviously at a high level before the year of 2008, and then the change fluctuations trends descended with time and tended to be stable.

[Spatial-temporal variation of fraction of absorbed photosynthetically active radiation (FPAR) in Beijing during 2010-2012.]

In this study, the spatial distribution of fraction of absorbed photosynthetically active radiation (FPAR) of vegetation in Beijing during 2010-2012 was analyzed based on the MODIS-FPAR data with a resolution of 1 km and the functional classification of vegetation. The yearly dynamics of FPAR of different vegetation types were also investigated. Furthermore, the correlation between FPAR and leaf area index (LAI) was explored. The results showed that, there was a spatially descended trend from the northeast mountains to the central urban area of Beijing. The annual average FPAR of different vegetation types changed little during 2010-2012. These values varied in the ranges of 0.42-0.44, 0.38-0.39, 0.32-0.33, and 0.21-0.22 for coniferous forest, broadleaf forest, grassland, and crop, respectively. However, the range of variation was big for each vegetation type within the year. There was significant linear or logarithm relationship between FPAR and LAI of each vegetation type. Additionally, the smooth time series of MODIS-FPAR of vegetation types could better reflect seasonal variation, which was generated by Savitzky-Golay filtering in software Timesat.

Coral-Associated Actinobacteria: Diversity, Abundance, and Biotechnological Potentials

Marine Actinobacteria, particularly coral-associated Actinobacteria, have attracted attention recently. In this study, the abundance and diversity of Actinobacteria associated with three types of coral thriving in a thermally stressed coral reef system north of the Arabian Gulf were investigated. Coscinaraea columna, Platygyra daedalea and Porites harrisoni have been found to harbor equivalent numbers of culturable Actinobacteria in their tissues but not in their mucus. However, different culturable actinobacterial communities have been found to be associated with different coral hosts. Differences in the abundance and diversity of Actinobacteria were detected between the mucus and tissue of the same coral host. In addition, temporal and spatial variations in the abundance and diversity of the cultivable actinobacterial communities were detected. In total, 19 different actinobacterial genera, namely Micrococcus, Brachybacterium, Brevibacterium, Streptomyces, Micromonospora, Renibacterium, Nocardia, Microbacterium, Dietzia, Cellulomonas, Ornithinimicrobium, Rhodococcus, Agrococcus, Kineococcus, Dermacoccus, Devriesea, Kocuria, Marmoricola, and Arthrobacter, were isolated from the coral tissue and mucus samples. Furthermore, 82 isolates related to Micromonospora, Brachybacterium, Nocardia, Micrococcus, Arthrobacter, Rhodococcus, and Streptomyces showed antimicrobial activities against representative Gram-positive and/or Gram-negative bacteria. Even though Brevibacterium and Kocuria were the most dominant actinobacterial isolates, they failed to show any antimicrobial activity, whereas less dominant genera, such as Streptomyces, did show antimicrobial activity. Focusing on the diversity of coral-associated Actinobacteria may help to understand how corals thrive under harsh environmental conditions and may lead to the discovery of novel antimicrobial metabolites with potential biotechnological applications.

Patterns of spatio-temporal distribution, abundance, and diversity in a mosquito community from the eastern Smoky Hills of Kansas

Nearly 30% of emerging infectious disease events are caused by vector-borne pathogens with wildlife origins. Their transmission involves a complex interplay among pathogens, arthropod vectors, the environment and host species, and they pose a risk for public health, livestock and wildlife species. Examining habitat associations of vector species known to transmit infectious diseases, and quantifying spatio-temporal dynamics of mosquito vector communities is one aspect of the holistic One Health approach that is necessary to develop effective control measures. A survey was conducted from May to August, 2010 of the abundance and diversity of mosquito species occurring in the mixed-grass prairie habitat of the Smoky Hills of Kansas. This region is an important breeding ground for North America's grassland nesting birds and, as such, it could represent an important habitat for the enzootic amplification cycle of avian malaria and infectious encephalitides, as well as spill-over events to humans and livestock. A total of 11 species, belonging to the three genera Aedes, Anopheles, and Culex, was collected during this study. Aedes nigromaculis, Ae. sollicitans, Ae. taeniorhynchus, Culex salinarius, and Cx. tarsalis accounted for 98% of the collected species. Multiple linear regression models suggested that mosquito abundances in the grasslands of the central Great Plains were explained by meteorological and environmental variables. Temporal dynamics in mosquito abundances were well supported by models that included maximum and minimum temperature indices (adjusted R(2) = 0.73). Spatial dynamics of mosquito abundances were best explained by a model containing the following environmental variables (adjusted R(2) =0.37): ground curvature, topographic wetness index, distance to woodland, and distance to road. The mosquito species we detected are known vectors for infectious encephalitides, including West Nile virus. Understanding the microhabitat characteristics of these mosquito species in a grassland ecosystem will aid in the control and management of these disease vectors.