Effects of Environmental Factors on NH_4^+ Release in Sediment from Chaohu Lake

[Objective] The aim of the research was to reveal the influence mechanism of sediment-water exchange of nutrients in Chaohu Lake. [Method] The effects of environmental factors (overlying water, temperature, pH and dissolved oxygen concentration) on NH_4^+ release in sediment from Chaohu Lake were studied under controlled laboratory conditions. [Results] With the rising of temperature and the decrease of NH_4^+ concentration in overlying water, NH_4^+ released from sediment increased significantly. pH had a great effect on NH_4^+ release with a complicated mechanism. The largest release amount of NH_4^+ under anaerobic condition was about 6 times as much as that under aerobic condition. [Conclusion] This research would provide theoretical support for environmental management of Chaohu Lake in the project of leading water from the Yangtze River to Chaohu Lake.

The environmental implication of diatom fossils in the surface sediment of the Changjiang River estuary(CRE) and its adjacent area

In order to depict the distribution of diatom fossils in surface sediments and to establish a reliable reference data for further paleoenvironmental study in the Changjiang (Yangtze) River estuary and its adjacent waters, the diatom fossils from 34 surface sediment samples and their relationship with environmental variables were analyzed by principal component analysis and redundancy correspondence analysis. The diversity and abundance of diatom fossils were analyzed. Some annual average parameters of the overlying water (salinity, temperature, turbidity, dissolved oxygen, depth, dissolved inorganic nitrogen, dissolved inorganic phosphate and dissolved inorganic silicate) were measured at each sampling site. A total of 113 diatom taxa and one silicoflagellate species were identified in the investigation area. Diatom fossils were better preserved in fine sediments. The absolute abundance of diatom fossils did not significantly diff er between inshore and off shore areas, the species diversity decreased from inshore to off shore. This may be because high nutrients and low salinity promoted the growth of more brackish species in coastal waters. The diatom taxa were divided into three groups, on the basis of their response and indication to environmental changes. For example, Actinocyclus ehrenbergii and Cyclotella stylorum were dominant in coastal waters (Group 1 and Group 3) with high nutrients and low salinity;the relative abundances of Paralia sulcata and Podosira stelliger were significantly higher in off shore sites (Group 2, average 39.5%), which were characterized by high salinity and deep water. Four environmental variables (salinity, dissolved inorganic nitrogen, temperature and water depth) explained the composition and distribution of diatom taxa independently ( P< 0.05), this finding can be applied in further paleoenvironmental reconstruction research in this area.

The Correlation of Inorganic C, O Isotopic Values for Lake Chenghai Sediments and Its Environmental Implications

As one of the lakes on the Yunnan-Guizhou plateau, Lake Chenghai, which is a typical closed lake with the precipitation accounting for one-third or more of the annual water input, has a high total salinity (almost like a saline lake).The inorganic C,O isotopic composition of lake sediments bears much sensitive information about environmental change in the catchment, while their correlations revealed the hydrological conditions under which the lake was closed. Their compositional variations are controlled by temperature, precipitation, photosynthesis, dissolving equilibrium of the carbonate system and hydrological condition. According to our research on inorganic C, O isotopic composition of Lake Chenghai sediments, we investigated the environmental change of this catchment several decades ago. The results showed that Lake Chenghai has kept good hydrological closing conditions in the past several decades, as indicated by the good correlation of inorganic C, O isotopic composition of sediments; and that the environmental change in this catchment shows a tendency of periodical evolution on a 10\+\{-11\}-years scale, although the signal noise is relatively high at the bottom of the sediment core. And we also can extend C, O isotopes, a sensitive environmental indicator, to nearly saline lake environments with a high degree of mineralization.

Classifying the sedimentary environments of the Xincun Lagoon,Hainan Island,by system cluster and principal component analyses

An understanding of the sedimentary environment in relation to its controlling factors is of great importance in coastal geomorphology,ecology,tourism and aquaculture studies.We attempt to deal with this issue,using a case study from the Xincun Lagoon,Hainan Island in southern China.For the study,surficial sediment samples were collected,together with hydrodynamic and bathymetric surveys,during August 2013.Numerical simulation was carried out to obtain high-spatial resolution tidal current data.The sediment samples were analyzed to derive mean grain size,sorting coefficient,skewness and kurtosis,together with the sand,silt and clay contents.The modern sedimentary environments were classified using system cluster and principal component analyses.Grain size analysis reveals that the sediments are characterized by extremely slightly sandy silty mud（ESSSM） and slightly silty sand（SSS）,which are distributed in the central lagoon and near-shore shallow water areas,respectively.Mean grain size varies from 0 to 8.0Ф,with an average of 4.6Ф.The silt content is the highest,i.e.,52% on average,with the average contents of sand and clay being 43% and 5%,respectively.There exists a significant correlation between mean size and water depth,suggesting that the surficial sediments become finer with increasing water depth.Cluster analyses reveals two groups of samples.The first group is characterized by mean grain size of more than 5.5Ф,whilst the second group has mean grain size of below 3.5Ф.Further,these groups also have different correlations between mean grain size and the other grain size parameters.In terms of the tidal current,the average values of the root mean square velocity（RMSV） are 7.5 cm/s and 6.9 cm/s on springs and neaps,respectively.For the RMSVs that are higher than 4 cm/s,a significant positive correlation is found between the content of the 63–125 μm fraction and the RMSV,suggesting that the RMSV determines the variability of the very fine sand fraction.Based on system cluster and principal component analyses（PCA）,the modern sedimentary environments are classified into three types according to the grain size parameters,RMSVs and water depth data.The results suggest the importance of grain size parameters and high-spatial resolution hydrodynamic data in differentiating the coastal sedimentary environments.

The sources and composition of organic matter in sediments of the Jiaozhou Bay：implications for environmental changes on a centennial time scale

The Jiaozhou Bay is characterized by heavy eutrophication that is associated with intensive anthropogenic activities. Four core sediments from the Jiaozhou Bay are analyzed using bulk technologies, including sedimentary total organic carbon（TOC）, total nitrogen（TN）, the stable carbon（δ13C） and nitrogen（δ15 N） isotopic composition to obtain the comprehensive understanding of the source and composition of sedimentary organic matter and further shed light on the environmental changes of the Jiaozhou Bay on a centennial time scale.Results suggest that the TOC and TN concentrations increase in the upper core, having indicated a probable eutrophication process since the 1920 s in the inner bay and the 2000 s in the bay mouth. The TOC and TN concentrations outside the bay have also changed since 1916 owing to the variation of terrigenous input.Considering TOC/TN ratio, δ13 C and δ15 N, it can be concluded there is a mixture of terrigenous and marine organic matter sources in the study area. A simple two end-member（terrigenous and marine） mixing model usingδ13 C indicats that 45%–79% of TOC in the Jiaozhou Bay is from the marine source. The environmental changes of the Jiaozhou Bay are recorded by geochemical proxies, which are influenced by the intensive anthropogenic activities（e.g., extensive use of fertilizers, and discharge of sewage） and climate changes（e.g., rainfall）.

Environmental changes during modern period from the record of Gaoyou Lake sediments, Jiangsu

Based on analysis of parameters of cores taken from Gaoyou Lake, including magnetic susceptibility, grain-size characteristics and sedimentary rate, environmental changes during the modern period were examined with the assistance of historical records and Gaoyou Lake water level materials. It is concluded that during the modern period a higher value of magnetic susceptibility and a lower sediment grain size coincided with a wet climate, while a lower value of magnetic susceptibility and a higher grain size were related with a dry climate. The results indicate that the climate in the 123 years period from 1880 to 2003AD can be divided into four stages： two low water level stages （1880-1915AD, 1948-1981AD） and two high water level stages （1915-1948AD, 1981-2003AD）. It appears that the regional climate generally underwent a dry-wet-dry-wet pattern in 30-year cycles. At present, it is at the end of a wet period, so the regional climate is expected to become dry in the near future. This conclusion corresponds with the climate records in the historical literature of the Gaoyou area, and it also matches with the climatic changes in North Jiangsu area.

Distributions of surface sediments surrounding the Antarctic Peninsula and its environmental significance

We analyzed grain size composition to provide information on the types and distributions as well as depositional varieties of marine surface sediments from the area surrounding the Antarctic Peninsula. The samples retrieved from the study area contain gravel, sand, silt and clay. As suggested by bathymetry and morphology, the study area is characterized by neritic, hemipelagic and pelagic deposits. The glacial-marine sediments can be divided into two types, residual paratill and compound paratill, which are primarily transported by glaciers and as ice-rafted debris. Ocean current effects on deposition are more obvious, and the deposit types are distributed consistently with terrain variations.

Erosion environment in the sediment-rich area on the Loess Plateau

Based on the investigation and analysis of characteristics of precipitation, natural environment, socio-economic factors and soil erosion, this paper indicates that the precipitation is the main driving force for the soil erosion in the sediment-rich area, its variability determines the characteristics of soil and water loss; the natural conditions such as the drainage systems, geological and topographic features, the composition of soil and land surface materials, vegetation and climate determine the seriousness of soil and water loss; irrational socio-economic activities of human beings usually accelerated soil and water loss; meanwhile, the low preservation rate and inferiority of soil and water conservation measures made it impossible to make rapid progress on soil and water loss control. Furthermore, the characteristics of erosion environment endowed this area with more sediment that is the main reason for the flooding disasters by the Yellow River. Therefore, more emphasis should be placed on the enhancement of soil and water conservation. The soil loss prediction models will provide scientific basis for the planning of soil and water conservation, the designing of soil and water conservation measures and the valuation of effects of soil and water loss control. According to the analysis of the previous studies on soil loss prediction, and the water-sediment variation features, it is thought that study on soil loss prediction under various rainfall conditions and soil-water conservation measures should be carried out.

Geochemical records of phosphorus in Jiaozhou Bay sediments—Impli-cations for environmental changes in recent hundred years

Phosphorus is a key element and plays an important role in global biogeochemical cycles. The evolution of sedimentary environment is also influenced by phosphorus concentrations and fractions as well as phosphate sorption characteristics of the marine sediments. The geochemical characteristics of phosphorus and their environmental records were presented in Jiaozhou Bay sediments. Profiles of different forms of phosphorus were measured as well as the roles and vertical distributions of phosphorus forms in response to sedimentary environment changes were investigated. The results showed that inorganic phosphorus （IP） was the major fraction of total phosphorus （TP）; phosphorus which is bound to calcium, iron and occluded phosphorus, as well as the exchangeable phosphorus were the main forms of IP, especially calcium - phosphorus, including detrital carbonate-bound phosphorus （Det- P） and authigenic apatite-bound phosphorus （ACa- P）, are the uppermost constituent of IP in Jiaozhou Bay sediments. Moreover, the lead-210 chronology technology was employed to estimate how much phosphorus was buried ultimately in sediments. And the research showed that the impacts of human activities have increased remarkably in recent years especially between the 1980s and 2000. According to research, the development of Jiaozhou Bay environment in the past hundred years can be divided into three stages ： （ 1 ） before the 1980s characterized by the relatively low sedimentation rate, weak land-derived phosphorus inputs and low anthropogenic impacts; （2） from the 1980s to around 2000, accelerating in the 1990s, during which high sedimentation rates, high phosphorus abundance and burial fluxes due to the severe human activities impacted on the whole environmental system ; （ 3 ） after 2000, the period of the improvement of environment, the whole system has been improved including the decreasing sedimentation rates, concentration and the burial fluxes of phosphorus.

SPOT image used in river water suspendedsediment and its environmental background analysis

High spatial and spectral resolution sensors such as Landsat Thematic mapper wereusually used to estimate the suspended sediment concentrstions in the coastal zones. But few peoplehave used SPOT image in estimating suspended sedanment concentlations. When studying thesuspended sediment concentlation in Danshui hiver in Taiwan. SPOT adage was used because of itshigher spatial resolution and Danshui hiver being not as wide enough as the coastal area. The riversuspended sediment concentlation was divided into four levels by MLC classifer. Composite ofband1 and band2 was found the best combination to express the suspended sediment. And therelationship of river suspended sediment and its environmental background was analyzed byoverlaying the map of suspended sediment, vegetation type and pollution resouxces.

Environmental Flow Assessment Using Water-Sediment Approach at the Sekampung River, Indonesia

Environmental issue has been considered more significant in many aspects of engineering decision-making process particularly in river management. There is an increasing effort to conserve functioning of rivers for human use as well as nature, therefore environmental flow assessment has been widely developed. This paper discusses on environmental flow assessment of the Sekampung River, particularly on its middle reach. A new analytical approach based on water-sediment equations was introduced in order to determine a minimum environmental flow at the certain cross section of a river. The result of the new method was then compared with a minimum environmental flow provided by using two hydrological based methods, namely, Tennant and Flow Duration Curve Analysis (FDCA) method. The result shows that the concerned discharge provided by the water-sediment method (3.5 m3/s) is the smallest compare with a minimum environmental flow that is provided by both Tennant (5.7 m3/s) and FDCA method (4.5 m3/s). It is promising that the water-sediment method can be used as a simple approach on preliminary state of environmental flow assessment. The method involves not only water discharge but also its related sediment flow of the river in order to mitigate further ecological and morphological risks.

The significance of lake sediments geochemistry in environmental reconstruction of south Hongshan Lake, northwestern Tibetan Plateau during the past 150 years

A 107cm piston-core (SHC-2) was drilled at the site with water depth of 5m in South Hongshan Lake, northwest Tibet in 1998. Based upon the 0.72cm/a of modern sedimentary rate that was tested by 210Pb method and also calibrated by 137Cs method as well as the 1cm interval sample cutting level, a lake sedimentary record of 150-yr old and with a resolution of 1.4 yrs was obtained. Ratio of geochemistry contents (TOC, TN, CaCO3) and concentrations of trace elements such as B, Sr, Ba, Ca, Mg, K, Na, Al, Ti, Cu, Zn, Fe, Mn, Ni, Cr, V, Pb, etc were analyzed. The values of TOC, TN, C/N, CaCO3, Sr/Ba and Fe/Mn had clear environmental significance and well reflected the environmental changes. Geochemical multi-proxies of lacustrine sediments from SHC-2 core showed that the environmental changes in this area during the past 150 years could be reconstructed as follows: Stage 1 (1850s-1880s) was a cold period; Stage 2 (1880s-1920s) was a warm period. But the variation of lake water volume was stable in the two periods. Stage 3 (1920s-1950s) was a fluctuant and transitional period in temperature, but there were a short cold period in the 1920s and a warm period in the 1930s. Stage 4 (1950s-) showed a warming tendency, though there existed a cold period from the mid 1970s to the end of the 1980s. In the view of general trend in the past 150 years, South Hongshan Lake was shrinking gradually. It showed that, from the comparison with the Guliya ice core and meteorological records of adjacent weather stations, there is difference in the variations of temperature and precipitation among different regions and altitudes in Tibetan Plateau. It is necessary to search multi-scale and high-resolution records for environmental reconstruction and comparison.

Path Analysis on Environmental Factors Controlling Runoff and Sediment Yields in Shelter Forests in Three Gorges Reservoir Region

Effects of environmental factors such as climate,topography,vegetation and soil in shelter forests in Three Gorges Reservoir Region on runoff and sediment yields were monitored to identify dominant environmental factors controlling runoff and sediment yields in 15 runoff plots in study area by soil sampling,laboratory analysis,stepwise regression analysis and path analysis,and to establish the main control environmental factors that affect runoff and sediment yields. The results showed that soil bulk density,herbaceous cover,slope,and canopy density were the significant factors controlling runoff,and the direct path coefficient of each factor was ranked as canopy closure(-0. 628) > litter thickness(-0. 547) > bulk density( 0. 509) > altitude( 0. 289). The indirect path coefficient was ranked as soil bulk density( 0. 354) >litter thickness(-0. 169) > altitude( 0. 126) > canopy closure(-0. 104). Therefore,canopy closure and litter thickness mainly had direct effects on runoff,while soil bulk density mainly had indirect effects through their contributions to other factors. Herbaceous cover,litter thickness,slope,canopy density,and altitude were the significant factors controlling sediment yields. The direct path coefficient of each factor was ranked as herbaceous cover(-0. 815) > litter thickness(-0. 777) > canopy closure(-0. 624) > slope( 0. 620). The indirect path coefficient was ranked as slope( 0. 272) > litter thickness(-0. 131) > canopy closure(-0. 097) > herbaceous cover(-0. 084). Therefore,herbaceous cover and litter thickness mainly had direct effects on sediment yields,while slope mainly had indirect effects through their contributions to other factors. All the selected environmental factors jointly explained 85. 5% and 78. 3% of runoff and sediment yield variability,respectively. However,there were large values of remaining path coefficients of other factors influencing runoff and sediment yields,which indicated that some important factors are not included and should be taken into account.

Environmental Geochemistry of Heavy Metal Contaminants in Soil and Stream Sediment in Panzhihua Mining and Smelting Area,Southwestern China

Mining and smelting activities are the main causes for the in creasing pollution of heavy metals in soil, water body and stream sediment. An e nvironmental geochemical investigation was carried out in and around the Panzhih ua mining and smelting area to determine the extent of chemical contamination in soil and sediment. The main objective of this study was to investigate the envi ronmental geochemistry of Ti, V, Cr, Mn, Cu, Pb, Zn and As in soil and sediment and to assess the degree of pollution in the study area. The data of heavy metal concentrations reveal that soils and sediments in the area have been slightly c ontaminated. Geochemical maps of I\-\{geo\} of each heavy metal show that the co ntaminated sites are located in V-Ti-magnetite sloping and smelting, gangues d am. The pollution sources of the selected elements come mainly from dusts result ant from mining activities and other three-waste-effluents. The area needs to be monitored regularly for trace metal, especially heavy metal enrichment.

Sedimentary Records and Environmental Analysis of the Ximencuo Lake in Northeast Qinghai-Tibet Plateau in the Past 1,700 Years

Lake sediment is the recorder of historical climate fluctuation and basin environment change. This study collected the Ximencuo Lake sediment in source area of the Yellow River, analyzed organic matters and geochemical elements of the core, obtained nearly environment changes of the past 1,720 years. The results showed the environment evolution process of the 47-cm columnar core can be divided into four stages: below 32 cm(before 900 A.D.), corresponding to the cool and wet climate; 32–20 cm(900 A.D–1300 A.D.), corresponding to the warming temperature and decreasing precipitation; between 20–3.5 cm(1300–1900 A.D.), the stage is more consistent with the Little Ice Age, and precipitation gradually reduced; 3.5–0 cm(since 1900 A.D.), this is the twentieth Century warming period with increasing temperature and reduced precipitation. Phosphorus content increased rapidly in the last 20 years, reflecting the continuously increasing human interventions, but before this period, the P content was low and stable, indicating the natural background of regional phosphorus content.

Changes in Sedimentation Rate of Tidal Flat and Environmental Significance at Qidong Foreland of the Yangtze Estuary

The sedimentation rate is an important environmental parameter to understand the evolution of coastal geomorphology. The tidal flat around Qidong foreland is located in the junction between Yangtze Estuary and Jiangsu coast,where the land-ocean interactions are strong and highly sensitive to environmental changes. The QDZ-1 core sediments collected at Qidong foreland was analyzed for137 Cs dating and grain size.The results showed that silt is the main sedimentary type with a trend of gradually fining from the bottom to the top,conforming to the sedimentation characteristic of the silt muddy tidal flat. The sedimentation rate could be divided into three distinct stages: 1963 to 1986 was 2. 61 cm/yr,1963 to 2011 was 1. 82 cm/yr,and 1986 to 2011 was 1. 10 cm/yr. Based on these,further explanation was made for the significance of environmental changes. According to the estimation of sedimentation rate,the impact of extreme environmental change was reflected by the sudden increase in sand proportion at the depth of 172. 5 cm. Since the introduction of Spartina alterniflora in the 1970 s,it has played an important role in tidal flat development. The tidal flat has a high sedimentary rate during this time. With continuous accretion of the tidal flat,low tidal flat turns to high tidal flat,the sedimentation rate gradually declines,and tidal flat sedimentation appears.

Aquaculture Environmental Capacity Research of Daiqu Fishery of Zhoushan: The Impact of Cage Culture on Sediment Quality

Impact of LaMmichthys crocea cage culture in Daiqu fishery （Zhoushan, Zhejiang Province） on the chemistry of the sediment was inves- tigated. Sediment samples, in different depths and from three stations at various distances from the cage, were collected, for analyzing total organic matter, total organic carbon, total nitrogen and phosphorus. The results showed a significant increase in all analyzed parameters in station 1, at 5 m from the cage. The difference between reference station （600 m from the cage） and station 2 at 95 m to the cage was insignificant, indicating lo- calized impact of cage farming to the vicinity of cage. The analyzed parameters in various depths did not show a significant difference. The values of analyzed parameters in the perimeter of the cage and their differences with reference stations showed small magnitude and localized impact on the chemistry of sediment. It might be because of deep water and moderate velocity of water current in this fjord. The magnitude of impact may dif- fer durina the summer when biomass and feedina rate would be at the maximum level.

Environmental magnetic measurements of marine sediments from Antarctica: implications to paleoclimate changes during the past 15 ka

In this paper, authors report some results obtained from systematic rock magnetic measurements on Core NP95 1 and Core NG93 1 , which were collected from the Prydz Bay, Eastern Antarctica and Great Wall Bay (Maxwell Bay), Western Antarctica respectively during the 11th and 9th CHINARE and a sequence of paleoclimate variations is well established based on sediment rock magnetic properties. In Antarctica, the magnetic properties show a close linkage to paleoenvironmental variations. The Core NP95 1 well recorded several paleoclimatic events, such as Heinrich event 1, Bolling Allerod warm period and Younger Dryas cold event. The Heinrich event 1 occurred at about 14 2 ka B.P., Younger Dryas cold event occurred between 11 7 ka B.P. and 10 3 ka B.P., and the boundary of Pleistocene and Holocene in Antarctica is 10 3 ka B.P.. In Holocene, two warm periods were recorded at about 10 0 ka B.P. and 6 0 ka B.P. with a little cold period between them. After 6 0 ka B.P. , two cores both recorded a cold climatic oscillation. Paleoclimate described by two cores rock magnetic measurements was simultaneously changed in Eastern and Western Antarctica during the same period two cores commonly covered.

Multi-proxy evidence for Late Pleistocene-Holocene climatic and environmental changes in Lop-Nur,Xinjiang,Northwest China

A 10.35-m-long sediment core from the Luobei depression in Lop-Nur,Xinjiang,Northwest China,provides detailed information about environmental changes during the Late Pleistocene.The samples taken every 5 cm of the core were analyzed for 10 environmental proxies,including magnetic susceptibility,granularity,chroma,carbonate and loss on ignition(LOI),and pH value.The chronology data are provided by the uranium/thorium disequi-librium dates.The sediments of the section were deposited during the last 32000 years.The results of analysis of 10 proxies were examined using multivariate statistical analysis,and the principal components were calculated.According to the results,the Late Pleistocene sequence contains four climatic and environmental stages appearing in the cycles of cold-wet and warm-dry changes.During 10-9 ka BP,it was the earliest warm episode in the Holocene.Environmental changes in this district were restricted by global change,as suggested by the analysis of glacial-interglacial cycles.But it was different from the mutative trend of a monsoon region in East China because of its own characteristics,which was the situation of cold-wet and warm-dry climate-environment change.The candidate reason may be the uplift of the Tibet Plateau and the westerly wind circulation.

LEADAT: a MATLAB-based program for lead-210 data analysis of sediment cores

The program described herein （LEADAT） serves to calculate sediment date and sedimentation rate using the ^210pb method for the studies of environmental processes and pollution history on a time scale of 100 - 150 a. The program written in MATLAB （ Version7.0） permits the user to select the principal models of ^210pb method, i. e. , the constant fluxes of sediment and lead-210 （ CF- SL） model, the constant flux of lead-210 （CFL） model, the constant initial concentration of lead-210 （CICL） model and the twolayer mixing （TLM） model. Although appropriate model selection is essentially based on understanding of the sedimentary processes, the pattern of the excess ^210pb profile is also helpful for model selection. The excess ^210pb profiles for two sediment cores collected from a brackish lake and an embayment respectively are used to demonstrate the application of the program. With a graphical user interface, the program can be easily executed. Not only ASCII but also graphical output can be generated by means of the program. Meanwhile, the code can be modified easily for extension.