黄土区沟道泥沙微生物群落变化特征及其影响因素

在黄土高原沟壑区,通过16S rRNA基因片段和ITS高通量测序,研究沟道泥沙中细菌和真菌群落在上-中-下游的变化特征.结果表明:与沟头相比,把口站的细菌群落中拟杆菌门(Bacteroidetes)与厚壁菌门(Firmicutes)的相对丰度分别增加6.6%和10.5%,而变形菌门(Proteobacteria)的相对丰度降低15.1%;真菌群落中担子菌门(Basidiomycota)的相对丰度增加7.7%,而子囊菌门(Ascomycota)降低30.2%;泥沙中黏粒含量与细菌丰富度(Chao1指数)和多样性(Shannon指数)之间显著负相关(P<0.05),与真菌的丰富度和多样性无显著相关性;细菌和真菌群落多样性和丰富度的空间差异与SOC、Olsen-P的变化有关(P<0.05).因此,泥沙中颗粒组成物和养分含量可能是影响沟道微生物群落变化的主要因素.

Spatial Distribution of Heavy Metals in Agricultural Soils of an Industry-Based Peri-Urban Area in Wuxi, China

In industry-oriented peri-urban areas, the heavy metal accumulation in soils caused by industrialization has become a potential threat. The top soil samples from 27 paddy fields and 75 vegetable fields were collected from a typical industry- based peri-urban area of about 8 km^2 in Wuxi, China, to study the accumulation and distribution of As, Hg, Cu, Zn, Pb, Cr, and Cd in comparison with heavy metal contents in soils near developed industrial sites （Guangzhou, China; Wallsend Burn of Tyneside, UK; and Osnabrück, Germany）. Kriging interpolation was used to determine the metals, spatial distribution. The results showed that most soils, compared to the background values, contained elevated contents of As, Hg, Cu, Zn, and Pb with some having elevated contents of Cd and Cr. Except for less than 10% of the soil samples of Cu, Zn and Cd contents, these heavy metal contents were lower than the soil threshold levels of the Grade Ⅱ criteria for the Chinese environmental quality standard. Probably, because of the scattered distribution and diversity of industries in the study area, spatial distributions of these heavy metals from Kriging interpolation indicated little similarity. Nevertheless, when compared with other areas in the Taihu Lake region, mean contents of Cu, Zn, Pb, and Cd were relatively high in the Wuxi peri-urban area. Additionally, compared to soils in agricultural areas around Guangzhou, Osnabrück, or Wallsend Burn, contents of most heavy metals in soils from this area were lower.

Spatial distribution,sources and ecological risk assessment of heavy metals in Shenjia River watershed of the Three Gorges Reservoir Area

Surface soil/sediment samples were collected from the Water-Level Fluctuation Zone(WLFZ), cultivated land and forest land at 50 different grid points from Shenjia watershed, the Three Gorges Reservoir area in August 2013. The spatial distribution, sources and ecological risk assessment for Arsenic(As), Cadmium(Cd),Chromium(Cr), Copper(Cu), Nickel(Ni), Lead(Pb)and Zinc(Zn) were analyzed in this study. The results showed all tested metals had similar distribution patterns except Ni and Cr, with areas of high concentrations distributed in the southwest(WLFZ and watershed outlet) of the study area. Ni and Cr,which were highly positively correlated and present in high concentrations, were primarily distributed in the south and middle zones of the study area. Lower concentration areas of all metals were uniformly distributed west of the high-elevation zones and forest land. Factor analysis(FA) and factor analysismultiple linear regression(FA-MLR) showed that the major sources of Cd were fertilizer and traffic sources,which together accounted for 87% of Cd. As, Zn and Cu levels were primarily supplied by industrial and domestic sources, accounting for 76% of As, 75% of Cu and 67% of Zn. Surface soils/sediments of the study watershed contaminated by Cd represent a high ecological risk, whereas other metals represent low ecological risks. The potential ecological risk index(PERI) analysis indicated that it had a low(widerange) ecological risk and a moderate(small-range)ecological risk primarily distributed in the outlet of the study watershed. Fertilizers and traffic are the primary sources of Cd pollution, which should be more closely controlled for the purposes of water quality and ecological conservation.

The distribution and potential ecological risk of Pb for multi-phase medium of artificial reefs in summer

Using inductively coupled plasma mass spectrometry(ICP-MS)to detect the Pb content in the multi-phase medium(water,sediment and large benthic organisms)in the artificial reef areas of Bohai Bay in Tianjin to analysis its spatial distribution characteristics and potential ecological risk.Using different evaluation methods.The results showed that:the Pb content is varied from 0.003-0.024μg/L,mean 0.008±0.007μg/L,the highest values appear in the No.9 station;the minimum value is 5 stations.Pb content of sediment is varied from 0.003-0.024μg/L,mean 0.008±0.007μg/L,the highest values appear in the No.9 station;the minimum value is 5 stations.The vertical sediment distribution of Pb decreased in the order:lower>middle>upper layer in each station.Risk evaluation showed that potential ecological risk index of Pb is low in the reef sediments;accumulate partial index is belong to moderate pollution levels;enrichment factor is belong to the light^pollution-free.Pb content of organisms is rang from 0.004-0.519 mg/kg,mean 0.185±0.170 mg/kg in reef area;BCF value of Pb content in organisms is generally higher than BAF value;its health risk factor is far less than 1,indicating that Pb has no obvious health risks on exposure population.

PERFORMANCE EVALUATION AND COMPARISON OF THREE COUNTING BLOOM FILTER SCHEMES

The Counting Bloom Filter （CBF） is a kind of space-efficient data structure that extends a Bloom filter so as to allow approximate multiplicity queries on a dynamic multi-set. This paper evaluates the performance of multiplicity queries of three simple CBF schemes-the Naive Counting Bloom Filter （NCBF）, the Space-Code Bloom Filter （SCBF） and the d-left Counting Bloom Filter （dlCBF）-using metrics of space complexity and counting error under both uniform and zipfian multiplicity distributions. We compare their counting error under same space complexity, and their space complexity when similar counting errors are achieved respectively. Our results show that dICBF is the best while SCBF is the worst in terms of both space-efficiency and accuracy. Furthermore, the performance gap between dlCBF and the others has a trend of being enlarged with the increment of space occupation or counting accuracy.

Soil Heavy Metal Pollution and Bioavailability in Baoshantao Mining Area, China

In areas with a high geological background of heavy metals,some edible plants could pose a serious threat to human health.In order to find effective methods to remove heavy metals or reduce their harm,this study investigated the enrichment conditions of five soil heavy metals,Cd,Pb,Cu,Zn and Cr,in four edible plants in a mining area,Baoshantao,in eastern China that has a high geological background of metals,and two groups of experiments were designed to investigate the effects of passivators on their enrichment.The results showed that the soil heavy metal content in the study area has a certain degree of spatial variability.The five heavy metal element contaminants in the soil are in the order of Cd>Cu>Zn>Pb>Cr.The enrichment coefficients and the transfer coefficients of different edible plants were different for the different heavy metals.The two groups of passivators showed better passivating effects with an increase in passivating agent dosage.The smaller the enrichment coefficient of water spinach,the lower the bioavailability.The results of this study can provide a scientific basis for the restoration of soil heavy metal pollution and the safe use of land in areas with a high geological background of heavy metals.

Spatial Distribution Patterns and Potential Sources of Heavy Metals in Soils of a Crude Oil-Polluted Region in China

Twenty-two soil samples were collected at the subregional scale （50 km2） around Gudao Town, a typical oil-producing region of the Shengli Oilfield in the Yellow River Delta, China to determine the spatial distribution patterns and potential sources of heavy metals in soils of crude oil-polluted regions. The concentrations of total petroleum hydrocaxbons （TPHs） and heavy metals as well as other soil properties were determined and the enrichment factor values were calculated for the heavy metals measured. Principal component analysis （PCA） and cluster analysis （CA） were used to estimate potential sources contributing to the concentrations of heavy metals in the soils. The results revealed that the soils were slightly alkaline （pH = 7.33-8.05） and high in salinity （1.43-41.30 g kg-1）, TPHs （0.51 28.40 g kg-1） and organic matter （1.74-31.50 g kg-1）. The mean concentrations of the measured heavy metals Cu, Zn, Pb, Cd, Cr, Ni and V were 18.4, 78.2, 20.8, 0.19, 56.6, 26.3 and 62.1 mg kg-1, respectively. Although the concentrations of all the metals measured in this study were not high enough to exceed the national control standards, there was a significant enrichment of Cd in the study area and Zn and Ni were in the category of deficiency to minimal enrichment. The spatial distribution patterns of Cu, Cr, Ni and V were similar and partially affected by oil exploitation and petroleum hydrocarbon spills. Potential sources of Cr, Ni, V and Cu in the soils were both natural sources and petroleum hydrocarbon spills, while Zn, Pb and Cd were probably from anthropogenic sources such as farming activities and traffic.

Spatial and Seasonal Variations of Heavy Metals in Wetland Soils of the Tidal Flats in the Yangtze Estuary, China: Environmental Implications

The environment of estuarine wetlands has been attracting worldwide attention. To study the spatial distribution of pollutants in the tidal flats of the Yangtze Estuary, Southeast China, the Eastern Tidal Flat of Chongming Island (EC) and the Jiuduansha Shoal (JS) of the estuary were selected as the study sites. At each of the two sites, a cross-transect from land to sea was established and topsoil and soil core samples in the cross-transect were collected spatially and seasonally to determine their contents of heavy metals (Cu, Zn, Pb, Cd, Cr, Ni, Mn, and Fe) and grain-size characteristics. The results showed that the heavy metal loads were commonly higher in the soils of nearshore high tidal flats and had a tendency of decreasing from land to sea at both of the study sites. The contents of heavy metals in the soils of the high and medial tidal flats were mostly higher in April and November but lower in July. Corresponding spatial and seasonal variations in grain size of the intertidal soils were also observed at the two study sites. The soils in the nearshore high tidal flats were finer and gradually got coarser seawards; they were relatively finer in April and November but coarser in July. Furthermore, the contents of heavy metals in the intertidal soils of both the sites EC and JS were significantly positively correlated with the clay (<2 μm) and 2-20 μm fractions, but negatively with the sand (>63 μm) and 20-63 μm fractions, which suggested that the heavy metals in the intertidal soils were primarily combined with the fine particulate fraction (<20 μm), especially clay, and hence the spatial and seasonal variations in heavy metals were actually caused by the change of the grain-size characteristics of the intertidal soils due to the different sedimentary environments in the estuary. The results of this study may also contribute to a better understanding of the soil formation and classification in the tidal flats of the Yangtze Estuary.