Substance-related environmental monitoring

Background  Due to the requirements of the EU Water Framework Directive and other legal regulations (e.g., national laws like the German Federal Soil Protection Act), but also due to the implementation of the new EU chemicals management system REACH, environmental monitoring will gain increasing importance for the surveillance of environmental quality as well as for the assessment of chemicals. Against this background, the Work Group on ‘Environmental Monitoring’ of the Division of ‘Environmental Chemistry and Ecotoxicology’ within the German Chemical Society has compiled a position paper on substance-related environmental monitoring. Scope  Core elements of this position paper are the definitions of important terms like monitoring, exposure monitoring, effect monitoring, and integrated monitoring. Moreover, temporal and spatial aspects (monitoring of spatial distributions, trend monitoring, and retrospective monitoring) and their applications are discussed. The main focus of this position paper is the coverage of aspects which have to be observed for the preparation and implementation of a monitoring program. Essential is the clear specification of the targets of the monitoring which determine the development of the monitoring concept and its realization, e.g., if environmental media (compartments) or organisms are most appropriate as samples for the aim of the study. Of course, also the properties of the target substances are important (e.g., lipophilicity/bioaccumulation as pre-requisite for an exposure monitoring with organisms). Finally, the monitoring phases of sample planning, sampling, storage and transport of samples, selection of analytical methods, quality assurance measures as well as reporting are discussed. Perspectives  An important issue for the future is to link the quantification of chemicals in environmental compartments (exposure and pollution monitoring) more closely to the study of biological effects (effect monitoring) than has been the case up to now. Furthermore, by inclusion of a spatial differentiation, a comprehensive evaluation of the state of an ecosystem can be obtained and the relevance of the results improved. Practical examples of monitoring studies which illustrate various aspects covered in this position paper will be presented in a series of publications by members of the Work Group in the following issues of this journal.

Sediment integrative assessment of the Bay of Cádiz (Spain): An ecotoxicological and chemical approach

This study consisted of the sediment toxicity assessment of the Bay of Cádiz based on two endpoints: growth inhibition for Cylindrotheca closterium (benthic microalgae) and fecundity inhibition for Tisbe battagliai (harpacticoid copepod). A new methodology to eliminate (but not as storage technique) the autochthonous biota present in the sediment samples by immersing them in liquid nitrogen (? 196 °C) was also assessed. Sediment toxicity data showed different toxicity levels for both organisms. In general, T. battagliai was more sensitive; however a good correlation (r = 0.75; p  < 0.05) between sediment toxicity results for both species was found. Data in pore water (pH, redox potential, and toxicity for microalgae and copepod) and sediment (pH, redox potential, organic carbon, and metal concentrations) demonstrated that ultra-freezing did not alter sample characteristics; thus, this technique can be adopted as a pre-treatment in whole-sediment toxicity tests in order to avoid misleading results due to presence of autochthonous biota. Multivariate statistical analysis such as cluster and principal component analysis using chemical and ecotoxicological data were employed. Silt and organic matter percentage and lead concentration were found to be the factors that explain about 77% of sediment toxicity in the Bay of Cádiz. Assay methodology determined in this study for both assayed species is considered adequate to be used in sediment toxicity monitoring programs. Results obtained using both species show that the Bay of Cádiz can be considered a moderately polluted zone.     

Spatial distribution of uranium and thorium in the surface soil around proposed uranium mining site at Lambapur and its vertical profile in the Nagarjuna Sagar Dam

The understanding and evaluation of the possible interactions of various naturally occurring radionuclides in the world's third largest man-made dam, Nagarjuna Sagar located in Andhra Pradesh, India and built on river Krishna assumed significance with the finding of uranium deposits in locations near the dam. For the present work, surface soil samples from the mineralized area of Lambapur, Mallapuram, Peddagattu and sediment core samples from the Nagarjuna Sagar dam were analyzed for naturally occurring radionuclides namely uranium and thorium using gamma spectrometric technique. Also toxic elements lead and chromium were analysed by the Energy Dispersive X-ray Fluorescence Spectrometer (EDXRF) technique. Surface soil samples show a variation from 25 to 291 Bq/kg (2.02–23.5 mg/kg) for ²³⁸U and 32–311 Bq/kg (7.9–76.9 mg/kg) for ²³²Th. U/Th concentration ratio in surface soil samples ranged from 0.19 to 0.31 and was found comparable with the nation wise average of 0.26. The study of sediment core samples reflected higher U/Th concentration ratio of 0.30–0.33 in the bottom section of the core as compared to 0.22–0.25 in the upper section. The concentration ratio in the upper section of the core was similar to the ratio 0.23 found in the western Deccan Basalt region through which the river originates. A higher concentration of lead and chromium was observed in the upper section of the core compared to bottom section indicating the impact of river input on the geochemical character of dam sediment.     

Radioecology, radiobiology, and radiological protection: frameworks and fractures

A framework for the protection of the general public has been in existence for a very long time, although steps have recently been made by the ICRP to ensure that it is more fully comprehensive with regard to all actual and potential exposure situations. Protection of the environment, however, has only recently begun to be addressed in a structured manner, and is still an evolving subject. Nevertheless, it needs to be centred around some form of parallel framework to that which has evolved for the protection of human beings, although clearly on a different scale. It also needs to be embedded within the basic science of radiobiology, and form a central part of radioecology.     

Spatial identification by satellite imagery of the crop–fallow rotation cycle in northern Laos

In the mountainous regions of northern Laos, shifting cultivation, or slash-and-burn agriculture, is widely practiced. However, the crop–fallow rotation cycle is becoming shorter owing to forest conservation policies and population pressure, causing loss of productivity that deleteriously affects farmers’ livelihoods in the region. To investigate regional land use conditions, we have developed a method of identifying the crop–fallow rotation cycle from Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper+ (ETM+) data. We assessed the impact of the identified cycle on plant production measured by Normalized Difference Vegetation Index (NDVI). The study site was an area in Luang Prabang Province. Using eight TM and ETM+ images acquired annually from 1995 to 2003, except for 1998, when cloud-free data were not collected, we classified land use in each year as crop or fallow by the presence of vegetation in the late dry season. Conformity with fallow age determined by field investigation was 69.1%. The cultivation frequency from 1995 to 2002 showed that 77,000 ha (17.3% of the study site) had not been used for cropping during the period, but 41,000 ha (9.2%) had been used every year. Of the study site, 129,000 ha (29.1%) was cultivated one or two times, 83,000 ha (18.7%) was three or four times, and 54,000 ha (12.2%) was five or six times. The NDVI of crops in November did not provide sufficient evidence to prove the assumption that a longer fallow period would result in better crop yields. Instead, the regeneration of fallow vegetation was evidenced by the higher NDVI values after longer fallow. More than 8 years would be needed to reach the same NDVI as forest. From the produced maps indicating fallow age and cultivation frequency, we found that areas with high potential for regeneration decreased as cultivation frequency increased. Areas near rivers were intensively used, and fallow length was accordingly short. Low-potential areas were found in the western basin of the Mekong River. This spatial information can be used to detect areas where biomass productivity is at high risk of deteriorating. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Widespread waterborne pollution in central Swedish lakes and the Baltic Sea from pre-industrial mining and metallurgy

Metal pollution is viewed as a modern problem that began in the 19th century and accelerated through the 20th century; however, in many parts of the globe this view is wrong. Here, we studied past waterborne metal pollution in lake sediments from the Bergslagen region in central Sweden, one of many historically important mining regions in Europe. With a focus on lead (including isotopes), we trace mining impacts from a local scale, through a 120-km-long river system draining into Mälaren - Sweden's third largest lake, and finally also the Baltic Sea. Comparison of sediment and peat records shows that pollution from Swedish mining was largely waterborne and that atmospheric deposition was dominated by long-range transport from other regions. Swedish ore lead is detectable from the 10th century, but the greatest impact occurred during the 16th-18th centuries with improvements occurring over recent centuries, i.e., historical pollution > modern industrial pollution.     

Quantifying local traffic contributions to NO2 and NH3 concentrations in natural habitats

NO₂ and NH₃ concentrations were measured across a Special Area for Conservation in southern England, at varying distances from the local road network. Exceedances of the critical levels for these pollutants were recorded at nearly all roadside locations, extending up to 20 m away from roads at some sites. Further, paired measurements of NH₃ and NO₂ concentrations revealed differences between ground and tree canopy levels. At “background” sites, away from the direct influence of roads, concentrations were higher within tree canopies than at ground level; the reverse pattern was, however, seen at roadside locations. Calculations of pollutant deposition rates showed that nitrogen inputs are dominated by NH₃ at roadside sites. This study demonstrates that local traffic emissions contribute substantially to the exceedance of critical levels and critical loads, and suggests that on-site monitoring is needed for sites of nature conservation value which are in close proximity to local transport routes.     

Ultraviolet absorbance as a proxy for total dissolved mercury in streams

Stream water samples were collected over a range of hydrologic and seasonal conditions at three forested watersheds in the northeastern USA. Samples were analyzed for dissolved total mercury (THg_d), DOC concentration and DOC composition, and UV₂₅₄ absorbance across the three sites over different seasons and flow conditions. Pooling data from all sites, we found a strong positive correlation of THg_d to DOC (r² = 0.87), but progressively stronger correlations of THg_d with the hydrophobic acid fraction (HPOA) of DOC (r² = 0.91) and with UV₂₅₄ absorbance (r² = 0.92). The strength of the UV₂₅₄ absorbance-THg_d relationship suggests that optical properties associated with dissolved organic matter may be excellent proxies for THg_d concentration in these streams. Ease of sample collection and analysis, the potential application of in-situ optical sensors, and the possibility for intensive monitoring over the hydrograph make this an effective, inexpensive approach to estimate THg_d flux in drainage waters.     

Effects of tree size and spatial distribution on growth of ponderosa pine forests under alternative management scenarios

Forest ecosystems may be actively managed toward heterogeneous stand structures to provide both economic (e.g., wood production and carbon credits) and environmental benefits (e.g., invasive pest resistance). In order to facilitate wider adoption of possibly more sustainable forest stand structures, defining growth expectations among alternative management scenarios is crucial. To estimate the effect of tree size and spatial distributions on growth for forest structures commonly considered in uneven-aged forest stand management, large (0.2 ha+) plots were established in 14 uneven-aged ponderosa pine stands in eastern Montana. All study trees were stem-mapped and measured for diameter and 10-year sapwood and basal area increment. A generalized growth model was developed to predict both total and merchantable 10-year basal area increment for nine hypothetical stand structures [three diameter distributions (reverse-J, irregular, flat) × three spatial distributions (clumpy, partial clumpy, uniform)]. Results indicate that the size and spatial distributions of individual trees have a considerable effect on overall stand growth. The greatest total stand growth was in stands with reverse “J” shaped tree size distributions, while the greatest merchantable stand growth was in stands with “flat” diameter distributions and uniform spatial distributions. Through better comprehension of generalized uneven-aged stand growth dynamics, forest managers may better assess the effects of alternative stand structures on stand growth while providing forest stand structures that may be more resilient in a changing climate.