[Sources, Distribution, and Fluxes of Major and Trace Elements in the Yangtze River].

Surface water samples were collected from 20 sampling sites in the main stream and its major tributaries of the Yangtze River from April to May 2017. The concentrations of dissolved trace and major elements were analyzed to determine the spatial variation, source identification, and riverine fluxes using various multivariate statistical techniques, including correlation analysis, principal component analysis (PCA), and cluster analysis (CA) with the goal of determining the influence of natural factors and human activities, including the operation of the Three Gorges Dam on the distribution and loading of major and trace elements in the Yangtze River water environment. Spatial distribution results showed that Cu, Zn, Pb, Cd, and As were the major elements affected by human activities in the Yangtze River, and their concentrations downstream were significantly higher than those in the middle and upper reaches (P<0.05). All elements had fairly high concentration values in both channels of the Yangtze River mainstream in Chongqing city and Hanjiang River in Wuhan city, which were mainly related to the enhanced human activities. However, the low concentrations of multi-elements in the reach of the Yangtze River in Yichang were largely caused by the retention effect of Three Gorges Project on element transport, which decreased the riverine loadings of multi-elements. Principal component analysis (PCA) indicated that Na, Mg, K, Ca, Fe, Mn, Co, Ni, Mo, Cr, and V were mainly associated with the weathering and erosion of various rocks and minerals in the river basin. And Cu, Zn, and Pb were mainly affected by enhanced human activities, such as industrial wastewater, metal smelting, and mineral mining, whereas Cd and As were mainly related to agricultural activities. The spatial distribution of trace and major elements showed that concentrations of some elements in the Yangtze River channels were enhanced by human activities. Generally, the heavy metal pollution in the Yangtze River Basin was lower than that in other rivers of the world. However, the annual fluxes of Cu, Zn, Pb, Cd, and As could have far-reaching ecological effects on the Yangtze River estuary and offshore ecological environment.

[Sedimentary Phosphorus Speciation in the Coastal Hypoxic Area of Changjiang Estuary and Its Environmental Significance].

Phosphorus (P) is a potential limiting nutrient in Changjiang Estuary. Sedimentary P preservation and regeneration play an important role in indicating regional environmental changes and buffering P limitation in the water column. A series of coring experiments was implemented in the hypoxic area of Changjiang Estuary to explore sedimentary P speciation and distribution and their environmental significance. The results showed that the contents and distributions of P in the cores were largely influenced by terrestrial loading, and Detr-P was the dominant P form in the sediments, followed by Org-P, Fe-P, and Auth-P, whereas Exch-P was the minor phase of Tot-P (<5%). Auth-P was predominantly yielded by Org-P and Fe-P transformations. P preservation in Changjiang Estuary was significantly related to terrestrial inputs and environmental changes in the water column. P speciation in cores tracked the regional environmental changes effectively. Distribution of reactive P in the hypoxic area was significantly different from that in the oxic area, with fairly high C/P ratios. The benthic diffusive flux of DRP in the study area ranged from 0.90 to 1.13 µmol·(cm2·a)-1. Tot-P burial efficiency (PBE) was higher than 70% and the PBE for Detr-P was nearly 100%, whereas the PBEs for Fe-P and Org-P were 38% and 26%, respectively. Auth-P was the dominant fraction of reactive P preserved in the sediments, and about 51% of Auth-P originated from Fe-P and Org-P transformations. The PBE in the hypoxia area of Changjiang Estuary was fairly lower than that in the continental shelf of the East China Sea. Hypoxia leads to a decrease in the PBE, which would have long-term influence on ecological environmental problems, especially eutrophification. Changes in terrestrial inputs played a key role in P composition in the sediments; the P loads of Changjiang River coupled with primary production and hypoxia greatly affected the P cycling in the Estuary.

Diversity and Composition of Bacterial Community in Soils and Lake Sediments from an Arctic Lake Area.

This study assessed the diversity and composition of bacterial communities within soils and lake sediments from an Arctic lake area (London Island, Svalbard). A total of 2,987 operational taxonomic units were identified by high-throughput sequencing, targeting bacterial 16S rRNA gene. The samples from four sites (three samples in each site) were significantly different in geochemical properties and bacterial community composition. Proteobacteria and Acidobacteria were abundant phyla in the nine soil samples, whereas Proteobacteria and Bacteroidetes were abundant phyla in the three sediment samples. Furthermore, Actinobacteria, Chlorobi, Chloroflexi, Elusimicrobia, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Proteobacteria significantly varied in their abundance among the four sampling sites. Additionally, members of the dominant genera, such as Clostridium, Luteolibacter, Methylibium, Rhodococcus, and Rhodoplanes, were significantly different in their abundance among the four sampling sites. Besides, distance-based redundancy analysis revealed that pH (p < 0.001), water content (p < 0.01), ammonium nitrogen ([Formula: see text]-N, p < 0.01), silicate silicon ([Formula: see text]-Si, p < 0.01), nitrite nitrogen ([Formula: see text]-N, p < 0.05), organic carbon (p < 0.05), and organic nitrogen (p < 0.05) were the most significant factors that correlated with the bacterial community composition. The results suggest soils and sediments from a lake area in the Arctic harbor a high diversity of bacterial communities, which are influenced by many geochemical factors of Arctic environments.

Diversity and structure of soil bacterial communities in the Fildes Region (maritime Antarctica) as revealed by 454 pyrosequencing.

This study assessed the diversity and composition of bacterial communities in four different soils (human-, penguin-, seal-colony impacted soils and pristine soil) in the Fildes Region (King George Island, Antarctica) using 454 pyrosequencing with bacterial-specific primers targeting the 16S rRNA gene. Proteobacteria, Actinobacteria, Acidobacteria, and Verrucomicrobia were abundant phyla in almost all the soil samples. The four types of soils were significantly different in geochemical properties and bacterial community structure. Thermotogae, Cyanobacteria, Fibrobacteres, Deinococcus-Thermus, and Chlorobi obviously varied in their abundance among the 4 soil types. Considering all the samples together, members of the genera Gaiella, Chloracidobacterium, Nitrospira, Polaromonas, Gemmatimonas, Sphingomonas, and Chthoniobacter were found to predominate, whereas members of the genera Chamaesiphon, Herbaspirillum, Hirschia, Nevskia, Nitrosococcus, Rhodococcus, Rhodomicrobium, and Xanthomonas varied obviously in their abundance among the four soil types. Distance-based redundancy analysis revealed that pH (p < 0.01), phosphate phosphorus (p < 0.01), organic carbon (p < 0.05), and organic nitrogen (p < 0.05) were the most significant factors that correlated with the community distribution of soil bacteria. To our knowledge, this is the first study to explore the soil bacterial communities in human-, penguin-, and seal- colony impacted soils from ice-free areas in maritime Antarctica using high-throughput pyrosequencing.

[Flow injection-spectrophotometric determination of total dissolved nitrogen in seawater based on quantificational solenoid valves].

Using three pipe clamp solenoid valves to replace the traditional six-port valve for sample quota, a set of multi-channel flow injection analyzer was designed in the present paper. The authors optimized optimum instrumental testing condition, and realized determination and analysis of total dissolved nitrogen in seawaters. The construction of apparatus is simple and it has the potential to be used for analysis of total dissolved nitrogen. The sample throughput of total dissolved nitrogen was 27 samples per hour. The linear range of total dissolved nitrogen was 50.0-1 000.0 microgN x L(-3) (r > or = 0.999). The detection limit was 7.6 microgN x L(-3). The recovery of total dissolved nitrogen was 87.3%-107.2%. The relative standard deviation for total dissolved nitrogen was 1.35%-6.32% (n = 6). After the t-test analysis, it does not have the significance difference between this method and national standard method. It is suitable for fast analysis of total dissolved nitrogen in seawater.

[Chemicohydrographic characteristics and the seasonal variations of nutrients at 35 degrees N transect in the cold water mass of the Southern Yellow Sea].

Based on the four cruises during 2006-2007, the chemicohydrographic characteristics and the seasonal variations of nutrients at 35 degrees N transect in the cold water mass of the Southern Yellow Sea were analyzed. The results showed that: In Winter, hydrological conditions in the eastern part of the section was significantly influenced by the Yellow Sea Warm Current, and the vertical mixing in the deep water had not reached the bottom, which led to the different distribution of the elements in the eastern and western part of the section, the vertically uniform distribution was presented in the west and the upper water of the east, while the stratification structure was found in the bottom water of the east. In Spring, the Yellow Sea warm current residual water and the Qingdao cold water mass were the most obviously hydrological characteristics, and because of the increasing of the temperature in the upper water and the weakening of the vertical mixing, the stability of the water column increased gradually; compared with winter, the contour trend of DO, pH and nutrients in deep water transferred to the more horizontal direction, and with the arrival of spring blooming, the nutrient concentrations in the upper water decreased significantly, besides, the subsurface chlorophyll maximum (SCM) phenomena also began to emerge. In Summer, the section was influenced by the thermocline and the Yellow Sea cold water mass, which was accompanied with the maximum value phenomenon of DO and pH, in addition, the nutrient concentrations were low in upper water and high in bottom water, and compared with spring, the further reduction of the nutrient concentrations existed in upper water, but the nutrient concentrations were increasing dominantly in the water below the thermocline. In Autumn, with the decreasing of the temperature in the upper water and the enhancing of the vertical mixing, the stability of the water column decreased, but the vertical mixing in the deep water was still not smooth, and the nutrient concentrations in the bottom water of the east were higher than those in summer. This study further revealed the influencing mechanism of the mixing, stratification as well as other physical processes on the vertical distribution and its seasonal variations of the elements.