Application of a water quality model in the White Cart water catchment,Glasgow, UK

Water quality models of urban systems have previously focused on point source (sewerage system) inputs. Little attention has been given to diffuse inputs and research into diffuse pollution has been largely confined to agriculture sources. This paper reports on new research that is aimed at integrating diffuse inputs into an urban water quality model. An integrated model is introduced that is made up of four modules: hydrology, contaminant point sources, nutrient cycling and leaching. The hydrology module, T & T consists of a TOPMODEL (a TOPography-based hydrological MODEL), which simulates runoff from pervious areas and a two-tank model, which simulates runoff from impervious urban areas. Linked into the two-tank model, the contaminant point source module simulates the overflow from the sewerage system in heavy rain. The widely known SOILN (SOIL Nitrate model) is the basis of nitrogen cycle module. Finally, the leaching module consists of two functions: the production function and the transfer function. The production function is based on SLIM (Solute Leaching Intermediate Model) while the transfer function is based on the flushing hypothesis which postulates a relationship between contaminant concentrations in the receiving water course and the extent to which the catchment is saturated. This paper outlines the modelling methodology and the model structures that have been developed. An application of this model in the White Cart catchment (Glasgow) is also included.     

The ecosystem of the bay of Mali Ston natural and anthropogenic influence

Chemical hydrography, nutrients and trace metals in water, sediments and marine organisms were studied in the Bay of Mali Ston and their role in terms of pollution discussed. Results show that the entire study area is very strongly affected by the adjacent land. The overall area is well aerated so that no dangerous accumulation of nutrients with oxygen content reduction was recorded.

Results of analyses of trace metals show that the water and sediments of the bay contain high levels of some metals significantly higher than those from the open sea. This may be attributed to the natural sedimentation processes and the Neretva River and submarine spring runoffs carrying constituents of ignous and limestone rocks.     

An initial assessment of spatial relationships between respiratory cases,soil metal content,air quality and deprivation indicators in Glasgow,Scotland, UK: relevance to the environmental justice agenda

There is growing interest in links between poor health and socio-environmental inequalities (e.g. inferior housing, crime and industrial emissions) under the environmental justice agenda. The current project assessed associations between soil metal content, air pollution (NO₂/PM₁₀) and deprivation and health (respiratory case incidence) across Glasgow. This is the first time that both chemical land quality and air pollution have been assessed citywide in the context of deprivation and health for a major UK conurbation. Based on the dataset ‘averages’ for intermediate geography areas, generalised linear modelling of respiratory cases showed significant associations with overall soil metal concentration (p = 0.0367) and with deprivation (p < 0.0448). Of the individual soil metals, only nickel showed a significant relationship with respiratory cases (p = 0.0056). Whilst these associations could simply represent concordant lower soil metal concentrations and fewer respiratory cases in the rural versus the urban environment, they are interesting given (1) possible contributions from soil to air particulate loading and (2) known associations between airborne metals like nickel and health. This study also demonstrated a statistically significant correlation (?0.213; p < 0.05) between soil metal concentration and deprivation across Glasgow. This highlights the fact that despite numerous regeneration programmes, the legacy of environmental pollution remains in post-industrial areas of Glasgow many decades after heavy industry has declined. Further epidemiological investigations would be required to determine whether there are any causal links between soil quality and population health/well-being. However, the results of this study suggest that poor soil quality warrants greater consideration in future health and socio-environmental inequality assessments.     

Benthic polychaetes in the Ratnagiri bay, India: influence of anthropogenic factors

Study of changes in macrobenthic community structure is an intrinsic part of many environmental monitoring programmes. Hence, it is pivotal to distinguish the effects of natural and anthropogenic factors on these sensitive organisms for accurate assessment and management of coastal environment. Polychaete species diversity of five stations in the Ratnagiri bay was investigated during premonsoon and postmonsoon months in 2007. Though no spatial trends in polychaete diversity vis-à-vis the pollution was visible, the polychaete univariate indices were uniformily better in premonsoon indicating clear seasonal trends. Shannon diversity values ranged from 1.4-2.4 during premonsoon and 0.6-1.6 during postmonsoon. Station 5, which was most impacted by anthropogenic wastes as demonstrated by the anoxic conditions coupled with higher nutrient load, had comparatively higher H' values (1.9 and 1.6) and better evenness values (0.9 and 0.7) during both seasons indicating that the polychaetes were not influenced by anthropogenic contamination. The study indicates that the polychaete distribution and diversity in the bay were governed primarily by variations in sediment texture rather than the anthropogenic disturbances.     

攀枝花市水系沉积物与土壤中重金属的地球化学特征比较

水系沉积物和土壤都是表生作用的产物,是环境中污染物质的重要受纳体,但两者在物质来源和受纳污染物方面又有不同。重金属通过不同方式进入到水系沉积物和土壤之中产生污染,对于区域环境具有重要的影响。为了了解攀枝花市水系沉积物和土壤中重金属元素地球化学特征的异同和污染状况,在攀枝花市范围内系统采集了水系沉积物和土壤样品,从环境地球化学角度,应用地球化学方法研究了攀枝花市水系沉积物及土壤中重金属的地球化学特征,应用地质累积指数法评价了污染情况,并对二者进行了比较研究。结果表明,攀枝花市水系沉积物中重金属的含量普遍高于土壤;水系沉积物和土壤中重金属的分布具有相似的特征;水系沉积物中重金属的污染程度高于土壤,但总体上来说,重金属的污染程度较小。两者的污染程度不同是因为接受污染物的方式不同;两者的分布趋势相同,说明具有相同或相近的污染来源。     

The spatial relationship between human activities and C,N, P,S in soil based on landscape geochemical interpretation

The development and formation of chemical elements in soil are affected not only by parent material, climate, biology, and topology factors, but also by human activities. As the main elements supporting life on earth system, the C, N, P, S cycles in soil have been altered by human activity through land-use change, agricultural intensification, and use of fossil fuels. The present study attempts to analyze whether and how a connection can be made between macroscopical control and microcosmic analysis, to estimate the impacts of human activities on C, N, P, S elements in soil, and to determine a way to describe the spatial relationship between C, N, P, S in soil and human activities, by means of landscape geochemical theories and methods. In addition, the disturbances of human activities on C, N, P, S are explored through the analysis of the spatial relationship between human disturbed landscapes and element anomalies, thereby determining the diversified rules of the effects. The study results show that the rules of different landscapes influencing C, N, P, S elements are diversified, and that the C element is closely related to city landscapes; furthermore, the elements N, P, and S are shown to be closely related to river landscapes; the relationships between mine landscapes and the elements C, N, P, S are apparent; the relationships between the elements C, N, P, S and road landscapes are quite close, which shows that road landscapes have significant effects on these elements. Therefore, the conclusion is drawn that the response mechanism analysis of human disturbance and soil chemical element aggregation is feasible, based on the landscape geochemical theories and methods. The spatial information techniques, such as remote sensing and geographic information systems, are effective for research on soil element migration.     

Spatio-temporal changes associated with natural and anthropogenic factors in wetlands of Great Rann of Kachchh,India

Studies about wetlands have been identified as a key component of environmental change. The present study assesses the spatio-temporal changes in the wetlands of the Great Rann of Kachchh, in the Kachchh Biosphere Reserve, India, using remote sensing and GIS techniques. Satellite time-series data from Landsat (1977, 1990 and 1999) and IRS P6 (2006, 2008–2012) were used. The Normalised Difference Water Index (NDWI) was derived for each year and the layers were manually edited to obtain a high classification accuracy. The analysis found that the area has undergone considerable change from 1977 to 2011. The natural wetland area of 30.6 km² was converted to salt pans. An area of about 255 km² (41.6 %) of natural grassland was invaded by Prosopis juliflora, which raises further conservation concerns and emphasises the importance of having intervention plans to manage this ecosystem. The highest water spread of 1171 km² was observed in September 2011, followed by 2010, 2009 and 2008 in the same month. The present study is useful in planning the long-term management and conservation of the Great Rann of Kachchh wetland.     

Determining factors that influence the dispersal of a pelagic species: A comparison between artificial neural networks and evolutionary algorithms

Because of increasing transport and trade there is a growing threat of marine invasive species being introduced into regions where they do not presently occur. So that the impacts of such species can be mitigated, it is important to predict how individuals, particularly passive dispersers are transported and dispersed in the ocean as well as in coastal regions so that new incursions of potential invasive species are rapidly detected and origins identified. Such predictions also support strategic monitoring, containment and/or eradication programs. To determine factors influencing a passive disperser, around coastal New Zealand, data from the genus Physalia (Cnidaria: Siphonophora) were used. Oceanographic data on wave height and wind direction and records of occurrences of Physalia on swimming beaches throughout the summer season were used to create models using artificial neural networks (ANNs) and Na?ve Bayesian Classifier (NBC). First, however, redundant and irrelevant data were removed using feature selection of a subset of variables. Two methods for feature selection were compared, one based on the multilayer perceptron and another based on an evolutionary algorithm. The models indicated that New Zealand appears to have two independent systems driven by currents and oceanographic variables that are responsible for the redistribution of Physalia from north of New Zealand and from the Tasman Sea to their subsequent presence in coastal waters. One system is centred in the east coast of northern New Zealand and the other involves a dynamic system that encompasses four other regions on both coasts of the country. Interestingly, the models confirm, molecular data obtained from Physalia in a previous study that identified a similar distribution of systems around New Zealand coastal waters. Additionally, this study demonstrates that the modelling methods used could generate valid hypotheses from noisy and complicated data in a system about which there is little previous knowledge.     

Assessing geochemical influence of traffic and other vehicle-related activities on heavy metal contamination in urban soils of Kerman city,using a GIS-based approach

Heavy metal pollution caused by traffic activities is increasingly becoming a great threat to urban environmental quality and human health. In this paper, soils of Kerman urban and suburban areas were collected to assess the potential effects of traffic and other vehicle-related pollution by heavy metal accumulation in soils. Eighty-six samples were collected along streets and from residential and rural sectors, as well as vehicle-related workshops from depth of 0–5 and 15–20 cm and analyzed by flame atomic absorption spectrometry (FAAS) for heavy metals (Cd, Cr, Cu, Pb, Sn and Zn), as well as major elements (Al, Ca, Fe and Mn). Several hot-spot areas were identified in the composite geochemical maps produced based on Geographical Information System (GIS) technology. The majority of the hot-spot areas were identified to be vehicle-related workshops, fuel stations and road junctions. The most polluted hot-spot in the study area was located in soils close to a car battery processing workshop in the southwestern part of Kerman city, with concentrations of Cd (0.32 mg/kg), Cr (169 mg/kg), Cu (250 mg/kg), Pb (5,780 mg/kg), Sn (27.2 mg/kg) and Zn (178 mg/kg) of 1, 8.5, 8.3, 230, 13.5 and 3 times more than the relevant mean concentrations in natural soils, respectively. Traffic pollution has resulted in significant accumulation of heavy metals in soils and sediments, and that level of accumulation varied remarkably among elements. Based on X-ray diffraction analysis, most parts of soils and sediments of the Kerman basement consist of calcite and clay minerals. Abundance of clay minerals and medium to alkaline pH causes low mobility of heavy metals in soils of Kerman.     

The impact of urban land expansion on soil quality in rapidly urbanizing regions in China: Kunshan as a case study

At a stage of rapid economic development and urbanization in China, most cities are faced with serious problems caused by environment deterioration such as pollution, space press, afforestation degradation, and disordering. Kunshan City, one of the most economically vigorous regions in China, has suffered a more prominent conflict between urbanization and environmental safety. In this paper, urban land expansion in Kunshan City in the Yangtze River Delta was measured with reference to the Landsat data recorded in 1982, 1991, 1995, and 2003 and change in land-use pattern in 1981, 1991, 1995, and 2004 as well as that in nutrients in soils of different purposes between the periods were analyzed to study the effect of urban land-use expansion on soil characteristics. To get a better understanding of soil nutrients, heavy metal content, and pollution, on-the-spot investigation, sampling and laboratory analysis were all conducted, and the geo-accumulation factors and revised Nemerow comprehensive index method were adopted for evaluation of the findings. The results show that the content of organic matter, total nitrogen, rapidly available nitrogen, and available phosphorus in the soil (except available potassium) all increased, and the average content of As, Cd, Cr, Cu, Pb, Ni, Hg, Se, and Zn prove to be 8.61, 0.12, 83.53, 32.49, 29.93, 30.45, 0.27, 0.24, and 93.3 mg kg⁻¹, respectively, showing degradation in soil quality.     

Use of a physiologically based extraction test to estimate the human bioaccessibility of potentially toxic elements in urban soils from the city of Glasgow,UK

A simple, two-stage, physiologically based extraction has been applied to assess the human bioaccessibility of potentially toxic elements (PTE) in 20 urban soils from a major UK city. Chromium and iron bioaccessibilities were found to be markedly higher in the intestinal phase, whilst lead and zinc bioaccessibilities were higher in the stomach. Copper and manganese bioaccessibilities were generally similar under both extraction conditions. Principal component analysis was used to study relationships amongst bioaccessible element concentrations and land use. Distinctions could be observed between the distributions of the urban metals—copper, lead and zinc—and metals predominantly of geogenic origin, such as iron. There was no clear delineation between roadside soils and soils obtained from public parks. Bioaccessible analyte concentrations were found to be correlated with pseudototal (aqua regia soluble) analyte concentrations for all elements except iron. Results of the BCR sequential extraction did not, in general, provide a good indication of human bioaccessibility. Comparison of bioaccessible PTE concentrations with toxicological data indicated that lead is the element of greatest concern in these soils but that levels are unlikely to pose a health risk to children with average soil intake.     

The effect of texture and irrigation on the soil moisture vertical-temporal variability in an urban artificial landscape: a case study of Olympic Forest Park in Beijing

Soil moisture variability in natural landscapes has been widely studied; however, less attention has been paid to its variability in the urban landscapes with respect to the possible influence of texture stratification and irrigation management. Therefore, a case study was carried out in the Beijing Olympic Forest Park to continuously monitor the soil in three typical profiles from 26 April to 11 November 2010. The texture stratification significantly affected the vertical distribution of moisture in the non-irrigated profile where moisture was mostly below field capacity. In the profile where irrigation was sufficient to maintain moisture above field capacity, gravity flow led to increased moisture with depth and thus eliminated the influence of texture. In the non-irrigated sites, the upper layer (above 80 cm) exhibited long-term moisture persistence with the time scale approximating the average rainfall interval. However, a coarse-textured layer weakened the influence of rainfall, and a fine-textured layer weakened the influence of evapotranspiration, both of which resulted in random noise-like moisture series in the deeper layers. At the irrigated site, frequent irrigation neutralized the influence of evapotranspiration in the upper layer (above 60 cm) and overshadowed the influence of rainfall in the deeper layer. As a result, the moisture level in the upper layer also behaved as a random noise-like series; whereas due to deep transpiration, the moisture of the deep layer had a persistence time-scale longer than a month, consistent with characteristic time-scales found for deep transpiration.     

珠江三角洲城市群大气微生物与环境相关性

运用生态学的方法,结合实地调查与数理统计分析,对珠江三角洲城市群的大气微生物与环境的相关性问题进行探讨,拟为珠江三角洲城市环境污染的综合防治和卫生防疫工作提供依据,研究结果表明.(1)珠江三角洲城市群中广州和东莞的大气微生物含量较高,其中细菌比真菌含量高;室内较室外,无绿化地较有绿化地的大气微生物含量高,在全年中,春、夏季节的大气微生物含量相对较高.(2)大气风速、湿度、气温、可吸入颗粒、总悬浮颗粒、人口流动,绿化状况等环境因子与大气微生物真菌、细菌的平均含量有较明显的相关关系,大气微生物含量与气象因子多数呈正或负的线性关系.相关分析的计算结果为:真菌、细菌平均含量在春、夏、秋、冬四个季度中与大气温度、湿度、风速大多数地区相关程度比较高,其值R在0.583～0.988之间,真菌、细菌与可吸人颗粒数和总悬浮颗粒数,R值分别为为0.525,0.388和0.081,-0.044.一元线性回归分析和多元线性回归分析计算结果为:大气微生物含量与气象因子有明显的正或负的线性关系.真菌、细菌的平均含量与温度、湿度、风速一元线性回归模型的置信水平较高,其p值大多在0.019～0.483之间,T值在0.001～0.246之间;多元线性回归模型的置信水平也较高,其P值大多数在0.083～0.220之间,T值在0.026～0.132之间;排序值显示:温度、风速变化是大气微生物含量高低影响重要性最大的环境因子.(3)统计数据比较分析表明:大气微生物含量与人口密集状况、人口流动大小和绿化状况好坏也有较明显的相关性,火车站,汽车客运站售票厅,人口流量大,绿化无,大气微生物(真菌细菌)平均含量高;而人口流量相对较少,但车流量大,有一定的绿化带的道路大气微生物平均含量较低;环境条件、绿化较好的公园绿地大气微生物含量低,车流、人流多,绿化少的地段、商业中心大气微生物含量较高.     

Distribution of phytoplankton community and its influence factors in an urban river network,East China

To reveal the distribution characteristics of phytoplankton and the main influence factors under different conditions in the urban rivers, the investigations were conducted during autumn and winter 2014 in Changzhou City, East China. 178 taxa of phytoplankton belonging to 28 functional assemblages were identified. In autumn, the phytoplankton community compositions have high similarity for enhanced hydrological connectivity. The chlorophytes and diatoms (prevailing functional groups C, F, J, P), together with euglenoids (W1), showed high proportions of biomass in the main rivers and connected rivers. It was related to the well mixed eutrophic conditions. The phytoplankton community exhibited spatiotemporal heterogeneity in winter. Affected by the low water level and temperature, the free-living phytoflagellates (X2) replaced groups F and J in the main rivers. Phytoplankton productivity was the highest in the Tongji River. Chlorophytes Dictyosphaerium ehrenbergianum and Chlamydobotrys stellata had an overwhelming superiority during the winter bloom. They were significantly correlated with ammonium, total phosphorus and biochemical oxygen demand. Affected by tail water supply, the diatoms (MP) and euglenoids (W1) dominated in a beheaded river. The multivariate analyses based on the phytoplankton functional groups helped to evaluate the relationships and variations between the urban rivers. The redundancy analysis (RDA) results showed that nitrate nitrogen, water temperature, total nitrogen and total suspended solids were the main influence factors on the phytoplankton community. Except MP, the prevailing groups all showed significant negative correlations with nitrate nitrogen. Availability and utilization of dissolved inorganic nitrogen and hydrodynamic conditions affected the phytoplankton distribution.

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蕉园土壤因子与香蕉枯萎病发病的相关性研究

香蕉枯萎病（Fusarium oysporum f.cubense）是当前严重威胁我国华南地区香蕉生产的重要土传病害,目前尚未找到有效的防治方法。于2010年采集了3个典型香蕉枯萎病患病样地（尖峰、冲坡、十月田）和2个健康样地（临高、广州）的根际与非根际土壤样品共46份,采用常规分析方法测定了19项土壤理化指标含量。旨在从农艺措施的角度考虑香蕉枯萎病的防治提供理论依据。结果表明：健康蕉园的大多理化性状和养分含量高于患病蕉园。尤以土壤粘粒、有机质、CEC、全N、全P、有效P、有效Cu、有效Fe、有效B和交换性Ca含量表现更为明显,其在健康蕉园中的含量均为患病蕉园的1.5倍以上。同一患病蕉园根际土壤中的pH值随植株感病级别增加而上升,而有效P和有效B含量随植株感病级别增加而降低。由此可以推论,在蕉园适当增施P肥和B肥有助于抑制香蕉枯萎病发生。     

Modeling the impact of natural and anthropogenic nutrient sources on phytoplankton dynamics in a shallow coastal domain, Western Australia

The influence of different nutrient sources on the seasonal variation of nutrients and phytoplankton was assessed in the northern area of the Perth coastal margin, south–western Australia. This nearshore area is shallow, semi-enclosed by submerged reefs, oligotrophic, nitrogen-limited and receives sewage effluent via submerged outfalls. Analysis of 14 year of field observations showed seasonal variability in the concentration of dissolved inorganic nitrogen and phytoplankton biomass, measured as chlorophyll-a. For 2007–2008, we quantified dissolved inorganic nitrogen inputs from the main nutrient sources: superficial runoff, groundwater, wastewater treatment plant effluent, atmospheric deposition and exchange with surrounding coastal waters. We validated a three-dimensional hydrodynamic-ecological model and then used it to assess nutrient-phytoplankton dynamics. The model reproduced the temporal and spatial variations of nitrate and chlorophyll-a satisfactorily. Such variations were highly influenced by exchange through the open boundaries driven by the wind field. An alongshore (south–north) flow dominated the flux through the domain, with dissolved inorganic nitrogen annual mean net-exportation. Further, when compared with the input of runoff, the contributions from atmospheric-deposition, groundwater and wastewater effluent to the domain’s inorganic nitrogen annual balance were one, two and three orders of magnitude higher, respectively. Inputs through exchange with offshore waters were considerably larger than previous estimates. When the offshore boundary was forced with remote-sensed derived data, the simulated chlorophyll-a results were closer to the field measurements. Our comprehensive analysis demonstrates the strong influence that the atmosphere–water surface interactions and the offshore dynamics have on the nearshore ecosystem. The results suggest that any additional nutrient removal at the local wastewater treatment plant is not likely to extensively affect the seasonal variations of nutrients and chlorophyll-a. The approach used proved useful for improving the understanding of the coastal ecosystem.     

北京城区大气颗粒物与地表土壤金属元素空间关联分析

为研究北京市区大气降尘金属来源及其与表层土壤的关系,在北京市区五环内的典型地段采集落尘与土壤样品。研究中使用电感耦合等离子体原子光谱仪(ICP-AES)测定了9种金属元素Cd、Cu、Zn、Fe、Pb、V、Ti、Mn、Al的质量分数。结果显示,降尘和土壤中Al、Fe两种元素所占比例最大,质量分数分别为16144.8、12881.9μg· g-1和21400.9、815712.2μg· g-1。其次降尘中Zn、Ti和土壤中Ti、Mn居第二位。随后基于灰度关联法对大气降尘与表层土壤的金属元素关系分析可知,大气降尘与表层土壤是高度关联的,关联值均介于0.92~0.95之间,二者间关联较为紧密。其中在空气降尘对表层土壤的影响研究中分析得出,空气降尘对表层土壤的影响与采样点的空间位置变化相关性不强,与风向、风速等自然环境因素的关联度较大。在表层土壤对空气降尘的影响研究中分析得出,表层土壤对空气降尘的影响度随采样点环境变化较大,尤其是北京南站。最后,通过对降尘金属元素进行因子分析得出,第一因子Z1同时与Pb、V、Ti、Mn、Al、Fe、Cu、Cd等元素有较大关系;第二个因子Z2与Cd、Cu等元素有较大的相关性;第三个因子Z3与Zn、Fe等元素有较大相关性,与其它7种元素的相关性不明显。前三因子 Z1、Z2、Z3方差累积贡献率可达97.2%,由此可知,降尘来源主要与风引起的地面扬尘,与塑料制品的焚烧,冶金、化工等工业影响及轮胎磨损有关。     

The influence of drainage networks on patterns of soil respiration in a desert catchment

Hydrologic flow and connectivity act as important determinants of ecological pattern and process in heterogeneous landscapes. Here we examine how the routing of water through the drainage network of an upper Sonoran Desert basin influences landscape patterns of soil respiration (SR) at both seasonal and event-based timescales. At seasonal timescales, SR varied up to 13-fold with downstream position in the drainage network, and annual estimates of CO2 efflux ranged from 185 g C x m(-2) x yr(-1) to 1190 g C x m(-2) x yr(-1) for sites arrayed along the same flow path. Spatial patterns of SR were unrelated to the carbon and water content of surface soils, but rather tracked changes in plant size and productivity, which in turn reflect downstream increases in groundwater availability. The relative importance of precipitation and temperature as drivers of SR also changed with landscape position, with the latter becoming more important in downstream locations. At the scale of individual precipitation events, SR increased up to 30-fold upon rewetting but typically returned to background levels within 24 h, even when soil moisture remained elevated. Unlike patterns observed at seasonal scales, event-based losses of CO2 varied across the landscape as a function of the organic-matter content in surface soils. Results from labile carbon amendments confirm that CO2 losses following precipitation pulses are initially constrained by substrate availability, not soil drying. By mediating spatial patterns of vegetation structure and soil resource availability, drainage networks represent an important physical template upon which belowground processes are organized in desert basins.     

Verifying the effect of acid precipitation on soil leachates: A comparison between published records and model predictions

A model for predicting the effects of acid precipitation on the acid (H⁺ + Al³⁺ + Fe³⁺- and base (Na⁺ + K + Ca²⁺ + mg²⁺)-cation losses from soils via leaching as function of time was verified by examining published results for one indoor and five outdoor lysimeter studies (with precipitation pH-values ranging from 2 to 6), and five watershed studies. In each case the predictions of the model were in acceptable (but not perfect) agreement with the observed acid and base cation losses. These studies were selected from other relevant studies because they nearly met the information requirements of the model. The prediction of the acid cation content of soil leachates is important for considering the generally negative effects of such cations (especially the dominating Al³⁺-ions) on plant growth and ground-, stream- and later water quality.