Multivariate statistical techniques for the evaluation of spatial and temporal variations in water quality of Gomti River (India)--a case study

This case study reports different multivariate statistical techniques applied for evaluation of temporal/spatial variations and interpretation of a large complex water-quality data set obtained during monitoring of Gomti River in Northern part of India. Water quality of the Gomti River, a major tributary of the Ganga River was monitored at eight different sites selected in relatively low, moderate and high pollution regions, regularly over a period of 5 years (1994-1998) for 24 parameters. The complex data matrix (17,790 observations) was treated with different multivariate techniques such as cluster analysis, factor analysis/principal component analysis (FA/PCA) and discriminant analysis (DA). Cluster analysis (CA) showed good results rendering three different groups of similarity between the sampling sites reflecting the different water-quality parameters of the river system. FA/PCA identified six factors, which are responsible for the data structure explaining 71% of the total variance of the data set and allowed to group the selected parameters according to common features as well as to evaluate the incidence of each group on the overall variation in water quality. However, significant data reduction was not achieved, as it needed 14 parameters to explain 71% of both the temporal and spatial changes in water quality. Discriminant analysis showed the best results for data reduction and pattern recognition during both temporal and spatial analysis. Discriminant analysis showed five parameters (pH, temperature, conductivity, total alkalinity and magnesium) affording more than 88% right assignations in temporal analysis, while nine parameters (pH, temperature, alkalinity, Ca-hardness, DO, BOD, chloride, sulfate and TKN) to afford 91% right assignations in spatial analysis of three different regions in the basin. Thus, DA allowed reduction in dimensionality of the large data set, delineating a few indicator parameters responsible for large variations in water quality. This study presents necessity and usefulness of multivariate statistical techniques for evaluation and interpretation of large complex data sets with a view to get better information about the water quality and design of monitoring network for effective management of water resources.     

Trace element differentiation in ferruginous accumulation soil patterns under tropical rainforest of southern Cameroon,the role of climatic change

Regions under tropical rainforest cover, such as central Africa and Brazil are characterised by degradation and dismantling of old ferricrete structures. In southern Cameroon, these processes are relayed by present-day ferruginous accumulation soil facies, situated on the middle and the lower part of hill slopes. These facies become progressively harder towards the surface, containing from bottom to top, mainly kaolinite, kaolinite-goethite and Al-rich goethite-hematite, and are discontinuous to the relictic hematite-dominated ferricrete that exist in the upper part of the hill slope. These features were investigated in terms of geochemical differentiation of trace elements. It appears that, in contrast to the old ferricrete facies, the current ferruginous accumulations are enriched in transitional trace elements (V, Cr, Co, Y, Sc) and Pb, while alkali-earth elements are less differentiated. This recent chemical accumulation is controlled both by intense weathering of the granodiorite bedrock and by mobilisation of elements previously accumulated in the old ferricrete. The observed processes are clearly linked to the present-day humid climate with rising groundwater tables. They slowly replace the old ferricretes formed during Cretaceous time under more seasonal climatic conditions, representing an instructive case of continuos global change.     

The Ribble/Wyre observatory: major, minor and trace elements in rivers draining from rural headwaters to the heartlands of the NW England historic industrial base

Information on a new observatory study of the water quality of two major river basins in northwestern England (the Ribble and Wyre) is presented. It covers upland, intermediate and lowland environments of contrasting pollution history with sufficient detail to examine transitional gradients. The upland rivers drain acidic soils subjected to long-term acidic deposition. Nonetheless, the acidic runoff from the soils is largely neutralised by high alkalinity groundwaters, although the rivers retain, perhaps as colloids, elements such as Al and Fe that are mobilised under acid conditions. The lowland rivers are contaminated and have variable water quality due to variable urban/industrial point and diffuse inputs reflecting local and regional differences in historic and contemporary sources. For most determinands, pollutant concentrations are not a major cause for concern although phosphate levels remain high. Set against earlier studies for other regions, there may be a general decline in pollutant levels and this is most clearly observed for boron where effluent inputs have declined significantly due to reductions in household products that are flushed down the drain. High concentrations of sodium and chloride occurred briefly after a severe cold spell due to flushing of road salts.A major inventory for water quality within rural, urban, industrial and agricultural typologies is provided within data summary attachments for over 50 water quality determinands. Within the next year, the full dataset will be made available from the CEH website. This, with ongoing monitoring, represents a platform for water quality studies across a wide range of catchment typologies pertinent to environmental management of clean and impacted systems within the UK. The study provides a base of research “from source to sea” including extensions to the estuary and open sea for a semi-confined basin, the Irish Sea, where there are many issues of pollution inputs and contamination.     

Assessment of nutrients using multivariate statistical techniques in estuarine systems and its management implications: a case study from Cochin Estuary,India

The status of nutrients in Cochin Estuary in relation with other physico-chemical variables was assessed using monthly data from seven locations for a period of 3 years. Seasonal comparative assessments were made and the probable sources of nutrients were modelled using principal component analysis (PCA). The results pointed out that the nutrients have higher concentration in premonsoon season compared with other seasons. The correlation coefficients of nutrients pointed out that strong correlation exists indicating that their source of origin could be same. Factor analysis extracted three principal components (PCs) in which the first component attributed to run-off, the second to influx of marine water and the third to intensive human activities. The proposed statistical model based on PCA gave a reasonable explanation on relation between physico-chemical parameters and environmental factors which have far reaching implications in the management of water systems.     

滇东南矿集区地球化学致矿信息提取

从复杂的地球化学场中识别不同级次的地球化学特征,结合区域地质背景和地质成矿事件解释异常,发现隐含在复杂地球化学场中的致矿地质异常特征和控矿地质异常特征,能够为成矿预测提供有效线索。文章尝试将传统的因子分析与非线性二维经验模分解技术(BEMD)相结合,以滇东南1∶20万区域地球化学数据为例,应用因子分析揭示滇东南矿集区的成矿背景和致矿异常元素组合及其空间分布特征,并应用BEMD方法进行分解滇东南矿集区成矿有利的因子组合,实现深层次致矿异常信息的提取,研究表明:(1)多元统计及因子分析结果揭示了区域成矿有利特征及两种主要的成矿元素组合:以Sn-Cu和PbZn-Ag等高—中—低温热液叠加矿化元素组合和以W-Be-Bi为主的一组典型中高温深成热液成矿元素组合;(2) BEMD方法的应用使得因子分析结果得到精细化逐级分解,经BEMD方法分解得到因子组合1的IMF1分量和因子组合3的IMF2分量反映了由规模相对较小(或埋藏较浅)的地质体引起的相对高频元素组合异常,因子组合1的IMF3分量和因子组合3的IMF3分量反映了由规模相对较大(或埋藏较深)的地质体引起的相对低频元素组合异常,其中因子组合1的IMF3分量的高值区在空间上与已知矿床对应程度较高,因子组合3的IMF3分量高值区为进一步找寻Sn-Cu多金属矿床的远景地段;(3) BEMD方法分解得到因子组合1和因子组合3的Res剩余分量则代表了由规模最大的深埋的地质体引起的低频元素组合异常,指明了个旧超大型Sn-Cu多金属矿床的成矿物质来源。     

Trace metals and their source in the catchment of the high altitude Lake Respomuso, Central Pyrenees

Lake Respomuso is a dammed lake of glacial origin at 2200 m altitude in the Central Pyrenees. This study investigated the source of a number of trace elements (As, Cd, Co, Cu, Mn, Ni, Pb and Zn) in its catchment and their possible link to the local geology. Altogether 24 sediment and 29 water samples were collected from all major streams feeding the lake. The sediments were analysed for trace elements, major mineral components, minerals and organic matter whilst water samples were analysed for dissolved metal concentrations.The trace element levels in the catchment sediment and water were relatively high compared to other similar altitude sites, with concentrations in the headwaters being generally higher than in the lower basin because of the source being concentrated in these areas. The principal component analysis revealed that the source of sediment-bound trace elements in the Lake Respomuso catchment is geogenic, and originated possibly in the sulphide minerals from slate formations.Except at one site, none of the water samples exceeded the WHO drinking water guideline for arsenic. Arsenic in water was significantly correlated with its concentration in the sediments, possibly due to the oxidation of arsenic bearing minerals. The dissolved concentrations of all other trace elements were generally lower than the WHO drinking water guide values and they were not related to their sediment concentrations.The As, Cd, Ni contents in sediment from several catchment streams exceeded their sediment quality thresholds. This geogenic source may pose risk to the stability of fragile local biodiversity and to the wider environment in the valley bellow particularly if the metals are mobilised, possibly due to environmental change.     

Heavy metals in benthic foraminifera from the highly polluted sediments of the Naples harbour (Southern Tyrrhenian Sea, Italy)

A systematic investigation evaluated the concentrations of a selected number of trace elements (Cd, Co, Cu, Li, Ni, Pb, V and Zn) in carbonates of the benthic foraminifera Ammonia tepida collected from surface sediments of the highly polluted harbour of Naples. Application of cleaning procedures, combined with Scanning Electron Microscopy investigation (SEM) of the analysed shells allowed reliable quantification of the elements in the carbonate lattice. Adoption of biogenic carbonate/seawater distribution coefficients reported in the literature provided the ranges of variability of total dissolved trace elements in the studied marine environment. Very high concentrations of Zn, Cd, and Cu calculated in seawater (from 100 to 10,000 times higher than those reported for uncontaminated Mediterranean seawaters) testify to intense effects of anthropogenic impact on the harbour mainly related to the industrial and commercial activities carried out in the neighbouring area. The ensemble of the obtained results emphasizes the high potential of measurements of trace elements in the biogenic carbonates of benthic foraminifera as tracers of anthopogenic pollution of seawater and reliable proxies of potentially bioavailable forms (as free ions and/or more labile organic complexes) of seawater dissolved metals.     

The comparison of two heavy fuel oils in composition and weathering pattern, based on IR, GC-FID and GC-MS analyses: Application to the Prestige wreackage

This paper compares the weathering patterns of two similar fuel oils: a fuel oil spilled after a ship accident (Prestige-Nassau, off the Galician coast -NW Spain-) and a fuel designed to cope with the numerous quests for samples to carry out scientific studies (IFO). Comparative studies were made to evaluate the capability of common fingerprinting analytical techniques to differentiate the fuels, as well as their capabilities to monitor their weathering. The two products were spilled under controlled conditions during ca. four months to assess how they evolved on time. Mid-IR spectrometry and gas chromatography (flame ionization and mass spectrometry detectors) were used. IR indexes related to total aromaticity, type of substituents (branched or linear chains) and degree of aromatic substitution reflected well the differences between the fuels during weathering. Regarding the chromatographic measurements, the n-alkanes became highly reduced for both fuel oils and it was found that the PAHs of the synthetic fuel (IFO) were more resistant to weathering. Regarding biomarkers, the different profiles of the steranes, diasteranes and triaromatic steroids allowed for a simple differentiation amongst the two products. The %D2/P2 ratio differentiated both products whereas the %N3/P2 one ordered the samples according to the extent of their weathering.