Study of the elemental composition of suspended particles in large northern-Asian lakes （Baikal and Khubsugul）

Lakes Baikal （Russia） and Khubsugul （Mongolia） are rift freshwater water bodies. The maximal depth of Baikal is 1642 m, that of Khubsugul -238 m. One of the important aspects in the study of suspended matter is its geochemical composition which depends on mineralogy and granulometry of the suspended matter. As the concentration of suspended matter in the sites of deep lakes is not high - about 1 mg/L, to determine the elements in the suspended matter the monochromatized synchrotron radiation method （SRXFA, Novosibirsk, Russia） was used. Water sampling was conducted in three basins of Lake Baikal and in Lake Khubsugul on central vertical cross-sections and in near-coastal sites. The water samples were collected with 10-liter batometers. The suspension was extracted from the water by filtration under vacuum through ＂Nuclepore＂ filters of 47 mm in diameter with pore size of 0.4 mkm. The mean weight of dry suspension on the filters was about 1 rag. The results of study of lacustrine suspended matter show that such elements as Fe, Ca, Mn, Ti, V, Cr, Cu, Zn, Pb dominate in lakes Baikal and Khubsugul. The concentration of other elements is low. On the whole, the vertical distribution of total amount of suspended matter in open Baikal decreases from the surface to the bottom. As for Lake Khubsugul, it increases.     

The acid neutralizing capacity （ANC） of South Africa＇s freshwater ecosystems

Acidification is considered the most important one of the primary chemical stress factors that impact on freshwater ecosystems. In unpolluted freshwater systems, the primary controls on the degree of acidification are factors such as the geological substrate of the catchment area, the presence of organic acids secreted by vegetation in the river system, and equilibrium exchange of carbon dioxide with the atmosphere. Anthropogenic factors that can impact on the degree of acidification of freshwater systems include agricultural, mining and industrial activities, either through direct runoff into river systems or through deposition of atmospheric pollutants from these sources. The capacity factors alkalinity and acidity, which represent the acid- and base-neutralizing capacity （ANC and BCN） of an aqueous system, have been used as more reliable measures of the acidic character of freshwater systems than pH. Unlike pH, ANC and BNC are not affected by parameters such as temperature and pressure. Therefore, ANC has been employed as a predictor of biological status in critical load assessments. Freshwater systems with ANC＇s eq/L isμeq/L are considered sensitive to acidification, ANC=0 μbelow 150 commonly used as the predictor for fish species such as trout in lakes, and an eq/L as more realistic for streams. Acid-neutralizing capacity μANC value of 40 （ANC） can be determined by titration with a strong acid to a preselected equivalence point. Alternatively, it can be calculated as the difference between base cations （[BC]） and strong acid anions （[SAA]）： ANC=[BC]- [SAA]=[Ca^2＋]＋[Mg^2＋]＋[Na^＋]＋[K^＋]-[SO4^2-]-[NO3^-]-[Cl^-] To date, there has been no attempt to establish the ANC of South Africa＇s freshwater ecosystems or variability therein, despite the fact that long-term water quality monitoring data exist for all the parameters needed to calculate it according to the above equations. As a result, the relationship between the acid neutralizing capacity of freshwater ecosystems in South Africa and biodiversity factors, such as fish status, is unknown. Results of the first comprehensive （country-wide scale） evaluation of the acid neutralizing capacity of river systems in South Africa will be presented. Long-term monitoring data obtained from the Department of Water Affairs and Forestry （DWAF） from most of South Africa＇s river systems were used to establish geographic and temporal variabilities in ANC. The results show that the Berg and Breede River systems are most susceptible to acidification, and that geological substrate appears to explain most of the geographic variabilities observed.     

Assessment of nutrient sources and paleoproductivity during the past century in Longgan Lake, middle reaches of Yangtze River, China

A 63-cm sediment core documents that the concentrations of nutrients in sediment, such as organic carbon, nitrogen and phosphorous, continually increased during the last century in Longgan Lake, middle reaches of the Yangtze River, China. C/N ratio and δ^13Corg revealed that organic matter in the sediment derived mainly from aquatic and terrestrial sources is a minor contributor. Excess phosphorous is related to human activities marked by utilization of phosphoric fertilizers since 1952 A.D. The increase of δ^13Corg towards the sediment surface, together with increasing of OC and N accumulation, indicated the elevation of lake primary productivity due to excess phosphorous loading caused by utilization of phosphoric fertilizer. The decrease of δ^15N during the primary productivity elevation process, especially after 1952, can be attributed to the discharged of nitrogen with lower δ^15N into the lake.     

Heavy metals in soil of the Baikal biosphere reserve （in connection with degradation of fir forests of the northern macroslope of Khamar-Daban Range）

The Baikal biosphere reserve （Khamar-Daban Range, South Pribaikalye） demonstrates withering of fir forests, progressing from 1970＇s. As to possible reasons of this phenomenon concerned, there are many viewpoints; the main among them is the technogenic influence of the Baikalsk pulp and paper plant （BPPP） and Irkutsk industrial center （IIC） on forest ecosystems. Geochemical characteristics of the snow cover within the Baikal reserve, investigated by us earlier indicate that degradation of fir forests at present does not result from the transfer of industrial emissions from BPPP and IIC to places of growing fir forests. Aimed at further revealing of reasons of fir forests withering, we investigated the chemical composition of soil （as a substratum feeding trees） in the Baikal biosphere reserve. We studied brown mountain-forest and alluvial-turf soil predominating in the reserve, which are characterized by weak differentiation profiles, in places （at the slope＇s bottom） by significant （up to 2.5-3 m） thickness. Samples of 250-300 gr. were collected from the genetic soil horizons distinguished visually and roughly by the thickness. Total contents of heavy metals （HM）-Cu, Cr, Ni, Zn, Co, Mn, Cd, Li, Rb, Sr, their mobile modes of occurrence （m/m）, extracted by acetate-ammonium buffer with pH=4.8 were determined. We also measured the concentrations of metals in the insoluble （fixed） residue （FR） obtained after extracting their mobile modes by atomic-absorption （Perkin-Elmer -503 spectrometer） method. The analytical error by this method does not exceed 10 %.     

Temporal and dimensional distribution of sulfate-reducing bacteria （SRB） groups and quantity in the sediments of Lake Erhai

The purpose of the thesis is to analyze the temporal and dimensional distribution of sulfate-reducing bacteria （SRB） groups and quantity in Lake Erhai. In April and September 2005, two sediment cores were collected from Lake Erhai. SRB groups were analyzed by PCR with six-groups primers designed according to the specific 16SrDNA sequence. FISH （fluorescence in-situ hybridization） was established with the oligonucleotide probe （SRB385） and utilized to analyze SRB quantity in the sediments. The results showed that in the sediments of Lake Erhai four SRB groups were detected except Desulfobacterium and Desulfobacter, meanwhile Desulfovibrio-Desulfomicrobium were detected only in autumn; different SRB groups had different temporal and dimensional distribution, and each group in autumn is distributed more widely than in spring; FISH used to count SRB in the sediments of fresh lake was set up successfully; the analysis of correlation between the sediment＇s depth and SRB quantity had statistical meaning （P〈0.05） . The result showed that SRB quantity showed a decreasing trend with increasing depth. Through the analysis of randomized block designed analysis of variance, the difference in SRB quantity between spring and autumn also had statistical meaning （P〈0.001）, which revealed SRB quantity in autumn was larger than in spring; the result of FISH showed that there were some SRB in the deeper sediments in which no above-mentioned six SRB groups were detected by PCR. SRB groups in the sediments of Lake Erhai were rich, and the quantities of SRB groups in autumn were larger than in spring; possibly there were uncultivable SRB groups in the sediments of Lake Erhai.     

Selected aspects of studies of sediments from the Ebro River （Spain） and the Dobczyce drinking water reservoir （Poland） within the frames of the European and national research projects

Mineral and organic matter either soluble or suspended are transported by the rivers and when deposited in the bed of the river or in the water reservoir, sediments are formed, whose chemical composition may serve as a fingerprint of the history of the ecosystem. The results of the studies of sediments in water systems （river catchments, reservoirs） can be used not only for the evaluation of the current state of the ecosystem but also to prevent any dangerous environmental changes. Bottom sediments can in many ways accumulate both suspended and soluble components. The process is influenced by several factors like pH, red-ox potential, oxygen content, interactions, etc. The complexity of those phenomena causes that in order to study the accumulation processes of compounds in sediments the application of various analytical techniques is required. The authors participate in two big projects on sediment studies. The AquaTerra Project is the EU funded project on understanding river-sediment-soil-groundwater interactions for support of management of river basins and catchment areas. Our group＇s studies are focused on mercury determination and its speciation in sediments and fish from the Ebro River in Spain. The Dobczyce Project is the national project funded by the Ministry of Education and sciences of Poland which is also a EU member country. The latter covers many aspects of accumulation and fate processes of chemical compounds in sediments of the reservoir which supplies 60% of drinking water to about one million population in the city of Krakow in Poland.     

Cross- and counter-current treatment systems for the removal of equilibrium constrained metals on unconventional sorbants [Bauxsol （TM）]

Bauxsol （TM） is a chemically modified industrial residue from bauxite refining. Consequently, the basis for the technology makes the new procedure an excellent example of ‘Green Technology＇. It has a high metal binding capacity （〉1500 meq/kg）, good phosphate retention （about 2% P by mass）, which remains plant available, and an acid neutralizing capacity from 2.5-7.5 mol/kg. Metal removal to the Bauxsol （TM） material generally shows a strong binding to the mineral surfaces, which improves with aging, and the removal shows a typical Langmuir isotherm. However, for some metals （e.g. Co^2＋, Tl^-, Hg^2＋ UO^2＋ and to some extent Mn^2＋） the removal isotherm rapidly becomes asymptotic, and a partitioning equilibrium between the water and solid appears to be achieved, which controls further metal removal. For these metals to be removed in a single pass type system exceptionally large quantities of Bauxsol （TM） are required. For example, Tl removal from a 1400 p,g/L solution to a single dose of 20 g/L Bauxsol （TM） gives an effluent Tl concentration of 47 μg/L for a 30-minute reaction time; longer reaction times do reduce the concentration （e.g. at 120 minutes Tl concentration is half that at 30 minutes）. However, at 30 minutes, which is typical for an industrial treatment plant, a single dose rate of roughly 300-400 g/L would be necessary to meet the groundwater criteria of 2 μg/L, and a dose rate of 2.3-3.9 kg/L to achieve the surface water criteria of 0.24 μg/L. Clearly, such high dose rates are uneconomic and impractical and this paper investigates the use of cross-current and counter-current treatment systems to counteract the effects of the equilibrium partitioning. The effects of these treatment systems on metal removal and effective dose rate are dramatic such that Tl in a 4-stage cross-current system requires only 18-22 g/L of Bauxsol （TM） to achieve the surface water criteria （about 1% of the single application requirement）.     

A preliminary study on the distribution characteristics of nutrients （N, P, Si, C） in the Wujiang River Basin

The distribution of nutrients (N, P, Si, C) in the Wujiang River surface water was studied during the high-flow and low-flow periods in 2002. The results showed that nitrate nitrogen (NO3-N) is the main form of dissolved inorganic nitrogen (DIN) in the Wujiang River Basin. It accounts for about 90% of DIN. The average NO3-N concentrations in the mainstream are 147.5 μM in the high-flow period and 158.0 μM in the low-flow period, respectively. The average concentrations of total phosphorus (TP) are 6.43 μM in the high-flow period and 4.18 μM in the low-flow period, respectively. Of the various forms of phosphorus, particulate phosphorus (PP) has the highest percentage ( 62.9%) of TP in the high-flow period. In the low-flow period, however, phosphate is the main form of phosphorus, which accounts for 49% of TP. With the Wujiangdu Reservoir as the boundary, the concentrations of DIN and phosphorus in the upper reaches are different from those in the lower reaches of the Wujiang River. As a whole, the concentrations of DIN and phosphorus are both higher in the low-flow period than in the high-flow period. The spatial and temporal variations of DIN and phosphorus concentrations suggested that DIN and phosphorus come from agricultural and domestic wastewaters and groundwaters and that the Wujiangdu Reservoir has an important impact on the concentrations and distribution of DIN and phosphorus in the Wujiang River. The distribution patterns of dissolved silica (DSi) and dissolved organic carbon (DOC) are similar. Both of them maintain no change in the whole course of the river and their concentrations (with the exception of the reservoir itself) are higher in the high-flow period than in the low-flow period. The average DSi and DOC concentrations in the mainstream are 85.4, 84.6 μM in the high-flow period and 60.8, 53.9 μM in the low-flow period, respectively. The concentrations of nutrients in most of the major tributaries are lower than in the mainstream. This suggested that the contributions of most tributaries are relatively small but importance should be attached to the influence of some individual tributaries such as the Qingshuijiang River and the Weng'an River on the mainstream.     

Devonian land-sea interaction： Evolution of ecosystems and climate （DEVEC）—the new IGCP Project 499

During the last two decades research on the Devonian period was part of some successful IGCP projects, such as IGCP 216 ““““““““Global biological events in Earth history““““““““ (led by O.H. Walliser), IGCP 335 ““““““““Biotic recoveries from mass extinctions““““““““ (led by D.H.Erwin and E.G. Kauffman), and IGCP 421 ““““““““North Gondwanan Mid-Palaeozoic bioevent /biogeography patterns in relation to crustal dynamics““““““““ (led by R. Feist and J.A. Talent）.     

Strontium isotope composition of the Arno River Valley waters （Tuscany, Italy） as a natural tracer of water-rock interaction and mixing processes

Sr isotope studies of surficial waters have highlighted that differences in the ^87Sr/^86Sr ratio and Sr concentration are primarily caused by mixing of waters of various origins with specific isotopic and chemical characteristics, resulting from water-rock interaction processes. In this paper we reported the first Sr isotopic ratios, coupled with water chemistry, the measurement was carried out on samples related to （1） the Amo River （Tuscany, central-northern Italy）, between the source and the mouth, （2） the most important tributaries and to （3） the thermal water discharges seeping out in the southern part of the basin. The main goals are： a） to use the ^87Sr/^86Sr ratio as a discriminative parameter of source areas, b） to define its variation along both the main course and principal tributaries, and c） to estimate the effects of the mixing process of the different end-embers. The outcropping rocks in the Amo River Basin are predominantly sedimentary, mainly made up of Mesozoic limestones, Oligocene sandstones and Plio-Pleistocene marine-lacustrine formations. Triassic and Mesosinian evaporites crop out in the Elsa and Era reaches, whereas Paleozoic quartzitic formations occur in the Mrs. Pisani area. Strontium isotopic composition is generally controlled by lithology and does not seem to be affected by anthropic input and flow rate. The ^87Sr/^86Sr ratios in the Arno Basin vary between 0.707963 and 0.712743, the highest ratios being related to waters circulating in the Palezoic rocks and Oligocene sandstone formations. Less radiogenic values pertain to the Elsa and Era tributaries where contributions related to the dissolution of evaporitic sequences, and mixing processes with the thermal discharges have been distinguished. The tributaries show that water samples in the pristine area have higher ^87Sr/^86Sr ratios than the respective tributaries from which water samples were collected near the confluence. Eventually, water samples collected along the Arno River, close to the mouth, tend to have Sr isotopic ratios similar to those of the present seawater.     

Study on Migration and Transformation Rule of Organic Pollutants （COD） in Aerated Zone

Collecting waste water with a certain concentration of organic pollutants COD (chemical oxygen demand), static adsorption, static biodegradation and dynamic soil column experiments were made in laboratory,we researched migration and transformation of COD in aerated zone. and put for-ward a mathematical model showing the process.The results show that adsorption of organism in aerated zone is linear,which is erprsented by henry‘s law s=Kdc sd, adsorption coefficient Kd=0.0693; biodegradation diagram accord basically with first-order kinetics equation c=coe^-k1t, biodegradation co-efficient K1=0.0499d^-1; dispersion coefficient D=0.0042m^2/d in experiments. The migration and transformation of organic pollutants (COD) in aerated zone jointly result from many factors such as dispersion, adsorption and biodegradation etc..     

The effects of microbial activity on the geochemistry of highly acidic crater lakes： An example from Laguna Caliente, Poas volcano （Costa Rica）

Laguna Caliente is a crater lake hosted within the Poas volcano （Costa Rica） that is considered one of the most active volcanic systems of Central America. Laguna Caliente is characterized by extremely low pH （-1） and very high TDS values （up to 33700 mg/L）, although, in the last two decades, the lake volume has significantly changed, mainly in relation to variations of the fumarolic activity. In this work, we present the chemical and isotopic compositions of water and dissolved gases collected along the vertical profile of the lake in order to constrain the main processes that control its physical-chemical features. Water and gas samples were collected. Laguna Caliente has a Ca （Mg）-Cl （SO4） composition, typical of acid-brine lakes of active volcanic systems. Among dissolved gases, CO2 content, by considering the low pH, is particularly high （up to 18.1% by vol.）, and relevant amounts of oxygen （15.8. % by vol.）, preventing the formation of any anoxic hypolimnion, are also present at the maximum depth. Temperature and chemical species remain almost constant along the vertical profile, with the exception of F- that shows a moderate increase with depth and CI and SO4^2-, whose contents increase by more than 10% at the depth of 20 m, and, below 20 m, decrease to values similar to those measured at surface. This compositional stratification may be tentatively explained by the complex combination of, at least, three processes： （1） input of high-temperature volatiles from sub-lacustrine fumaroles, （2） loss of HCl and H2S from lake surface through evaporation, and （3） SO4^2- and CI consumption due to microbial activity at the bottom of the lake.     

Experimental research on the influence of two cultivation practices on rainfall runoff- and （sandy and muddy） sediment-generating processes in purple soil environment

Rainfall simulations have been conducted to study the soil erosion process of purple soil in two cultivation practices---contour cultivation and downslope cultivation. Results showed that under the two cultivation practices, the surface runoff can be described by the logarithmic function formula. In the initial period of rainfall, the amount of runoff increased with the rainfall duration and 20 minutes later it became relatively constant. The changing process of soil erosion rate may be described by the logarithmic function formula. The erosion rate increased with the rainfall duration and 20 minutes later it also became constant. Under downslope cultivation condition, the soil erosion rate increased more significantly than that under contour cultivation condition in the case of gentle rainfall intensity, and there is no obvious difference in erosion rate for downslope cultivation and contour cultivation practices. However, with increasing rainfall intensity the soil erosion rate under the downslope cultivation condition could be more than 30 times that under the contour cultivation condition. But this kind of difference would be reduced to some extent in the case of heavy rain.     

Dissolution of hydrous Th （Ⅳ） oxide in aqueous Na^＋-H^＋-OH^——NO3^——H2O^- solutions in the presence of citrate, EDTA and oxalate

Data on the hydrolysis of Th （Ⅳ） and solubility of ThO2 in the presence of organic ligands are of critical importance to the safe disposal and treatment of high-level nuclear waste. Such data are required to predict reliably thorium behaviour in high-level waste repositories where organic anions may be present. In addition, recent studies of the performance of thorium-based fuels report that these fuels can be used to reduce concerns related to potential proliferation of nuclear weapons and disposal of the current uranium dioxide fuel waste. Because several reactor concepts based on thorium fuel cycles are under consideration, it is important to have thermodynamic data to predict how such fuel and its waste form will behave in the environment. To establish the effect of pH and organic ligands on the hydrolysis of Th （Ⅳ）, experiments on the solubility of hydrous ThO2 in aqueous solution at room temperature were performed, covering a wide range of pH （pH=3.0 to 12.0） in 0.1 molal NaNO3 solutions. Experiments also were conducted in the presence of citrate, EDTA and oxalate with a concentration range 100 to 500 μmol. Approach to equilibrium was from supersaturation. Slopes of straight lines fit to plots of log mTh vs. pH were approximately -4 at the acidic region and near 0 at neutral and alkaline region for experiments conducted at constant ionic strength （I=0.1）, implying that the dominant Th species should be Th4^＋ and Th （OH）4（aq） The←→Th^4＋＋2H2O ThO2＋2H2O←→Th （OH）40 as follows： ThO2＋4H^＋ solubility of ThO2 decreases with increasing pH （pH 3 -6） and remains near the detection limit of ICP-MS （in the order of 10^-9 M to 10^1- M） in the range of pH 6-12. These values are in accordance with data in the literature.