Lahn River Research Articles

Potential Analysis and Feasibility Study on the Hydrothermal Utilization of Rivers—Using Marburg on the Lahn River as Case Study

Due to their high specific heat capacity and constant thermal regeneration through flow, rivers are a promising renewable environmental heat source. The suitability of a river for hydrothermal use depends on river section-specific and site-specific factors. This paper presents a methodological proposal for a river section-specific potential analysis and site-specific feasibility study. The presentation of measured values in the form of hydrographs and duration curves as well as the use of suitable mean values and confidence intervals are central steps in the evaluation. The application of the potential analysis showed that the discharge in particular influences the size of the heat potential, while the water temperature determines whether and how the hydrothermal use is possible. The focus of this work was on the analysis of water temperature. Its significance for hydro-thermal use is multi-layered, and an assessment should be carried out at different levels. Using two specific sites on the Lahn river as a case study, the feasibility study method is demonstrated in this paper.

Evaluating the effectiveness of the MicroPlastic Sediment Separator (MPSS)

Effective laboratory methods are a requirement to obtain accurate data on the contamination of the environment with microplastics. However, current methods often lack specification and validation of performance. The aim of this work was to provide the first evaluation of the effectiveness of the commercially available MicroPlastic Sediment Separator (MPSS) operated with sodium chloride. We performed density separation experiments with pristine plastic particles spiked into both commercial sand (experiment I) and natural river sediments (experiment II) and with environmental microplastics contained in natural river sediments (experiment III). The natural sediments were taken from the Lahn River in Germany, a medium-scale central European tributary. The pristine test particles were ground polypropylene fragments, sieved in three different size classes: larger than 1 mm, 0.5–1 mm, and 0.3–0.5 mm. In experiment I, the mean recovery rate was 97 % for particles of the largest size class (standard deviation s=6~%; n=30 per size class), but dropped to 75.33 % (s=21.29~%) in the medium and to 54 % (s=25~%) in the smallest size class. After density separation, 87 % of all unsuccessfully separated test particles were found at the inner walls of the MPSS. In experiment II, the recovery rate was not correlated with the particle size distribution of the natural river sediments. In experiment III, a subsequent second density separation step contributed on average 38 % (s=18~%; n=5) to the total number of extracted environmental microplastics. This study illuminates central aspects of a density separation and aims to contribute to quality improvements of recovery rate experiments and field studies for the generation of reliable data on microplastics in the environment.

Persistence of trace metal contamination in a fluvial system: Lahn River, central Germany

To monitor short-term changes in trace metal concentrations (Cu, Pb, Zn) at geomorphically sensitive floodplain locations and examine the persistence of contaminants in the fluvial environment, near-channel sites along the Lahn River, central Germany, that were sampled in 2007 were revisited in 2019. Thirty-three cores were extracted from sites <5 m from the active channel along a 75-km reach of the river. The median concentrations of Cu and Zn in 2019 were statistically unchanged from concentrations in 2007, but median concentrations of Pb in 2019 were statistically higher than in 2007. Concentration of all three trace metals remain above the background concentrations, but only Zn concentrations exceed the 2ϭ background upper limit. On an individual sample site basis, the Cu concentration increased at 48 % of the sites and the Zn concentration increased at 45 % of the sites between 2007 and 2019. Pb concentration increased at 70 % of the sites. Concentrations of trace metals generally increased with distance downstream; the lowermost reach of the Lahn River continues to have the highest concentration of trace metals. Between 2007 and 2019, the concentrations (mean and median) of all three metals increased in the uppermost and lowermost sections of the study area whereas in the middle section the mean and median concentrations of Cu and Zn and the median concentration of Pb decreased (the mean concentration of Pb increased in the middle reach). Changes in metal concentrations between 2007 and 2019 do not appear to be caused by factors such as changes in substrate of samples, variable sedimentation rates and flood history, or the percentage of clay and organic matter content. Elevated concentrations of trace metals persist in near-channel sediments and will continue to pose a risk of future downstream heavy metal pollution in the study reach, especially along the lowermost reach of the Lahn River where the most contaminated sediments are located. Trace metal concentrations in the study reach appear to have become “uncoupled” from overall decreases in metal releases to the environment.

Identifying Spatial Patterns and Ecosystem Service Delivery of Nature-Based Solutions

Compared to technical infrastructure, nature-based solutions, NBS, strive to work with nature and to move beyond business-as-usual practices in order to address societal challenges such as flood risks. This research aims to spatially identify possible NBS areas and evaluate the areas capacity to provide selected ecosystem services, ES, for the Lahn river landscape in Germany. The research follows the functional landscape approach using hydromorphological landscape units, HLU, based on specific biophysical spatial criteria, such as slope, to then identify locations which may be considered suitable for NBS. The current ES delivery of these possible NBS areas is then evaluated. The three ES assessed are carbon storage, nutrient retention and recreation. We then undertake a geospatial comparison analysis to show the spatial relationships and patterns that emerge in regards to the ES configuration of the distinct NBS apt areas. Results show the HLU method serves to delineate and identify areas where NBS may exist or be implemented. The data depicts a distinct spatial pattern for each possible NBS space and complementary ES delivery. This explorative method is a useful spatial approach that can support NBS implementation and serve to investigate the multiple benefits NBS provide. The use of ecosystem services to compare and understand NBS is a viable prospect that must, however, be cautiously, locally and scientifically approached. Noticeable limitations regarding ES assessment remain, as available methods are often insufficiently inclusive of natural ecosystem processes and functions. Further research should assess a broader spectrum of NBS and their delivery of ES.

Advancing Sustainable Development Goals with localised nature-based solutions: Opportunity spaces in the Lahn river landscape, Germany

Nature-based solutions (NBS) are recognized as promising actions to alleviate societal challenges and achieve the United Nation's Sustainable Development Goals (SDGs). One scientific challenge to implement NBS in practice is to locate areas suitable for an effective implementation of NBS (opportunity spaces). Opportunity spaces either already host NBS that need to be safeguarded or restored, or provide the socio-ecological conditions for establishing new NBS. Complex methods have been proposed to model potential locations of selected NBS, but they are often too data and resource intensive to be applied in practice for landscape planning. The aim of this article is to put forward a pragmatic method for identifying NBS opportunity spaces that contribute to advance multiple SDGs, and to test its application in a participatory, extended peer-review process in the Lahn river landscape, Germany. Our method includes: (i) synthesizing a generic catalogue of NBS in river landscapes, (ii) estimating the potential of NBS to achieve simultaneously Lahn development goals (LDGs) and SDGs, and (iii) applying key spatial indicators and best available data to explore opportunity spaces for selected NBS. The generic catalogue provides a systematic overview of 650 individual NBS for river landscapes and their respective potentials for addressing LDGs and SDGs. The NBS Renaturalising floodplains through land use changes, Revitalising historic floodplains, and Creating buffer strips are those actions contributing to the greatest number of local SDGs (locally adapted SDGs that include LDGs). Results of the spatial analysis in the Lahn river landscape showed about 4739 ha of areas where NBS were already in place and need to be safeguarded and additional 1323 ha with opportunities for further NBS creation. The proposed method presents a robust and transferable approach that facilitates spatial mapping of NBS to local SDGs for planning practitioners facing time and resource constraints.

Spatial Connections between Microplastics and Heavy Metal Pollution within Floodplain Soils

Soils contain an increasing number of different pollutants, which are often released into the environment by human activity. Among the “new” potential pollutants are plastics and microplastics. “Recognized” pollutants such as heavy metals, of geogenic and anthropogenic origin, now meet purely anthropogenic contaminants such as plastic particles. Those can meet especially in floodplain landscapes and floodplain soils, because of their function as a temporary sink for sediments, nutrients, and pollutants. Based on a geospatial sampling approach, we analyzed the soil properties and heavy metal contents (ICP-MS) in soil material and macroplastic particles, and calculated total plastic concentrations (Ptot) from preliminary studies. Those data were used to investigate spatial connections between both groups of pollutants. Our results from the example of the Lahn river catchment show a low-to-moderate contamination of the floodplain soils with heavy metals and a wide distribution of plastic contents up to a depth of two meters. Furthermore, we were able to document heavy metal contents in macroplastic particles. Spatial and statistical correlations between both pollutants were found. Those correlations are mainly expressed by a comparable variability in concentrations across the catchment and in a common accumulation in topsoil and upper soil or sediment layers (0–50 cm). The results indicate comparable deposition conditions of both pollutants in the floodplain system.

Deposition and in-situ translocation of microplastics in floodplain soils

The microplastic (MP) contamination of oceans, freshwaters, and soils has become one of the major challenges within the Anthropocene. MP is transported in large quantities through river systems from land to sea and is deposited in river sediments and floodplains. As part of the river system, floodplains and their soils are known for their sink function with respect to sediments, nutrients, and pollutants. However, the questions remain: To what extend does this deposition occur in floodplain soils? Which spatial distribution of MP accumulations, resulting from possible environmental drivers, can be found? The present study analyzes the spatial distribution of large (L-MP, 2000–1000 μm) and medium (M-MP, 1000–500 μm) MP particles in floodplain soils of the Lahn River (Germany). Based on a geospatial sampling concept, the MP contents in floodplain soils are investigated down to a depth of 2 m through a combined method approach, including MP analyses, soil surveys, properties, and sediment dating. The analysis of the plastic particles was carried out by density separation, visual fluorescence identification, and ATR-FTIR analysis. In addition, grain-size analyses and 210Pb and 137Cs dating were performed to reconstruct the MP deposition conditions. The results prove a more frequent accumulation of MP in upper floodplain soils (0–50 cm) deposited by flood dynamics since the 1960s than in subsoils. The first MP detection to a depth of 2 m and below recent (>1960) sediment accumulation indicates in-situ vertical transfer of mobile MP particles through natural processes (e.g., preferential flow, bioturbation). Furthermore, the role of MP as a potential marker of the Anthropocene is assessed. This study advances our understanding of the deposition and relocation of MP at the aquatic-terrestrial interface.

Exploring perceptions of stakeholder roles in ecosystem services coproduction

Stakeholder groups engage in ecosystem services coproduction as both coproducers and beneficiaries. Stakeholder group perceptions of their own and each other’s roles in ecosystem services coproduction therefore influence how ecosystem services are provided in a given landscape. However, only a few studies have investigated self-perceived and attributed stakeholder group roles in this context. The aim of this paper is to assess the self-perceived and attributed engagement and importance of stakeholder groups in the coproduction of ecosystem services in a case study of the Lahn River landscape in Germany. The research questions address (i) local stakeholder group perceptions of their own engagement in the coproduction of ecosystem services and (ii) differences and commonalities between self-perceived and attributed stakeholder group importance in ecosystem services coproduction. Our method involves a survey local stakeholder groups regarding involvement in the coproduction of twelve ecosystem services and social network analysis to assess the survey data concerning network structures. Our findings indicate that self-perceived and attributed perceptions differ mainly regarding the central role of stakeholder groups in collaborative networks. We further identify differences in the self-perceived levels of importance of stakeholder groups within collaborative networks but similarities in the understanding of the overall stakeholder group network structure. We conclude by highlighting key implications for ecosystem services governance, including the need to address power imbalances and the need to foster collaborative engagement to ensure sustained and just ecosystem services delivery.

Spatially assessing unpleasant places with hard- and soft-GIS methods: a river landscape application

ABSTRACT This paper explores the visual, acoustic and olfactory impairments to landscape aesthetic quality in a river landscape case study, using hard- and soft-GIS approaches. The research objectives are (1) to develop a model that localizes the spatial distribution of areas likely perceived as unpleasant and assesses the intensity of visual, acoustic and olfactory impairments in those areas by using a hard-GIS method, and (2) to test the statistical validity of the model based on results gained from a soft GIS method. The case study area is the Lahn river landscape, Germany. Results show a substantial share of the study area affected by modelled impairments, especially areas close to urban environments and along rivers. The area affected by impairments is highest for visual (91%), followed by acoustic (84%) and olfactory factors (54%). However, impairment intensities are greatest for acoustics (30% of study area) and visual (18%). Soft-GIS data tests revealed statistical defensibility of modeled impaired areas. The results highlight the importance of disaggregate analyses of impairments and can provide information on suitable locations for interventions to minimize impairments. Combining hard-GIS with soft-GIS methods may contribute to the credibility, relevance and legitimacy of scientific findings for planning processes and decision-making.

Integrating sense of place into participatory landscape planning: merging mapping surveys and geodesign workshops

ABSTRACT This article explores the potential of integrating sense of place into participatory landscape planning processes. In an illustrative case study, spatial information on sense of place assessed through a participatory mapping survey from local citizens is integrated into a geodesign workshop at the Lahn river, Germany, with local stakeholders and planning administration representatives. Results show that sense of place information (1) has been considered interesting and relevant for the planning process by the majority of workshop participants, (2) revealed areas in the landscape that participants did not expect to be meaningful, and (3) spurred discussion on the potential meanings of the places and areas. We recommend planners to consider options for eliciting and integrating sense of place in future participatory landscape planning to reveal citizens’ unknown people-place relationships for the use in actual deliberation and negations.

Joint recording of contamination status, multi-element dynamics, and source identification on a sub-catchment scale: The example Lahn River (Germany)

Investigations on the enrichment level, binding dynamics, and source identification of contaminants are important objectives of environmental research into surface waters, but are often carried out independently of each other. To simultaneously address these issues an investigative approach is presented that combines multi-element analyses of water and suspended particulate matter (SPM) and is applied on the scale of a sub-catchment, using the Lahn River (Germany) as an example. Analyses of water and SPM comprised phosphorus (P), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), lead (Pb), and uranium (U). For the dissolved phase, the investigations additionally included nitrogen compounds (NH4, NO3) and dissolved organic carbon (DOC). SPM of the Lahn showed increased average concentrations of Zn (2.13 g kg−1), Cd (4.01 mg kg−1), and Pb (160 mg kg−1). The water phase sampled from points along the length of the Lahn showed significant spatial differences in the dissolved concentrations of Mn (15.7–98.4 μg l−1), Co (0.08–0.66 μg l−1), Ni (0.75–4.69 μg l−1), Zn (19.9–187 μg l−1), and Cd (0.01–0.18 μg l−1), which could be attributed to the inflow of two tributaries draining historic mining areas. The study emphasizes the importance of mine waters during low water periods and proves that such sources can differently affect the SPM quality and the dissolved concentrations of their receiving waters.

Planning nature-based solutions: Principles, steps, and insights

Nature-based solutions (NBS) find increasing attention as actions to address societal challenges through harnessing ecological processes, yet knowledge gaps exist regarding approaches to landscape planning with NBS. This paper aims to provide suggestions of how planning NBS can be conceptualized and applied in practice. We develop a framework for planning NBS by merging insights from literature and a case study in the Lahn river landscape, Germany. Our framework relates to three key criteria that define NBS, and consists of six steps of planning: Co-define setting, Understand challenges, Create visions and scenarios, Assess potential impacts, Develop solution strategies, and Realize and monitor. Its implementation is guided by five principles, namely Place-specificity, Evidence base, Integration, Equity, and Transdisciplinarity. Drawing on the empirical insights from the case study, we suggest suitable methods and a checklist of supportive procedures for applying the framework in practice. Taken together, our framework can facilitate planning NBS and provides further steps towards mainstreaming.

Spatial patterns of mesoplastics and coarse microplastics in floodplain soils as resulting from land use and fluvial processes

Plastic, and especially microplastic, contamination of soils has become a novel research field. After the detection of microplastics in soils, spatial distribution and dynamics are still unknown. However, the potential risks associated with plastic particles in soils cannot be sufficiently assessed without knowledge about the spatial distribution of these anthropogenic materials. Based on a spatial research approach, including soil surveys, this study quantified the mesoplastic (MEP, > 5.0 mm) and coarse microplastics (CMP, 2.0–5.0 mm) content of twelve floodplain soils. At four transects in the catchment area of the Lahn river (Germany), soils down to a depth of 2 m were examined for plastic content for the first time. MEP and CMP were detected through visual examination after sample preprocessing and ATR-FTIR analyses. Average MEP and CMP concentrations range between 2.06 kg−1 (±1.55 kg−1) and 1.88 kg−1 (±1.49 kg−1) with maximal values of 5.37 MEP kg−1 to 8.59 CMP kg−1. Plastic particles are heterogeneously distributed in samples. Both plastic size classes occur more frequently in topsoils than in soil layers deeper than 30 cm. The maximal depth of CMP occurrence lies between 75 and 100 cm. Most common CMP polymer type was PE-LD, followed by PP and PA. MEP and CMP particles occur frequently at near channel sides and more often on riparian strips or grassland than on farmland. Vertical distribution of CMP indicates anthropogenic relocation in topsoils and additional deep displacement through natural processes like preferential flow paths or bioturbation. By comparing sedimentation rates of the river with the maximum age of plastic particles, sedimentation as a deposition process of plastic in floodplains becomes probable. From our findings, it can be concluded that an overall widespread but spatial heterogenous contamination occurs in floodplain soils. Additionally, a complex plastic source pattern seems to appear in floodplain areas.

Prevalence and seasonal dynamics of blaCTX-M antibiotic resistance genes and fecal indicator organisms in the lower Lahn River, Germany.

Antibiotic-resistant bacteria represent an emerging global health problem and are frequently detected in riverine environments. Analyzing the occurrence of corresponding antibiotic-resistant genes in rivers is of public interest as it contributes towards understanding the origin and dissemination of these emerging microbial contaminants via surface water. This is critical for devising strategies to mitigate the spread of resistances in the environment. Concentrations of blaCTX-M antibiotic resistance genes were quantified weekly over a 12-month period in Lahn River surface water at two sampling sites using quantitative real-time PCR. Gene abundances were statistically assessed with regard to previously determined concentrations of fecal indicator organisms Escherichia coli, intestinal enterococci and somatic coliphages, as well as influential environmental factors. Similar seasonal patterns and strong positive correlations between fecal indicators and blaCTX-M genes indicated identical sources. Accordingly, linear regression analyses showed that blaCTX-M concentrations could largely be explained by fecal pollution. E. coli provided the best estimates (75% explained variance) at the upstream site, where proportions of blaCTX-M genes in relation to fecal indicator organisms were highest. At this site, rainfall proved to be more influential, hinting at surface runoff as an emission source. The level of agricultural impact increased from downstream to upstream, linking increasing blaCTX-M concentrations after rainfall events to the degree of agricultural land use. Exposure assessment revealed that even participants in non-swimming recreational activities were at risk of incidentally ingesting blaCTX-M genes and thus potentially antibiotic resistant bacteria. Considering that blaCTX-M genes are ubiquitous in Lahn River and participants in bathing and non-bathing water sports are at risk of exposure, results highlight the importance of microbial water quality monitoring with an emphasis on antibiotic resistance not only in designated bathing waters. Moreover, E. coli might serve as a suitable estimate for the presence of respective antibiotic resistant strains.

Trace metal concentrations along tributary streams of historically mined areas, Lower Lahn and Dill River basins, central Germany

Watersheds with a history of mining frequently have high concentrations of trace metals stored in downstream floodplain sediments. To assess the contribution of tributary streams to the elevated trace metal concentrations previously documented along the lower Dill and lower Lahn Rivers of central Germany, I examined the concentrations of Cu, Pb, and Zn in fourteen cores collected from near-channel sediments along 9 tributary streams. Five tributaries empty into the lower Dill River and 4 drain into the lower Lahn River. The tributary streams drain areas that were mined for Fe, Cu, and Pb for more than a century, with the last mine closing in 1983. Cores were also collected from near-channel sediments at 7 sites along the lower Lahn River to more broadly assess the storage of trace metals along the river. Large quantities of Cu, Pb, and Zn from mining activity are not stored in near-channel positions along the length of the sampled tributaries. Mean and median concentrations of Cu, Pb, and Zn along the tributaries are less than the mean and median concentrations along the lower Dill and Lahn Rivers; concentrations along the tributaries differ little from background trace metal levels and are less than contamination standards contained in the German Federal Soil Protection Act. The mean concentrations of Cu, Pb, and Zn along the lower Lahn River are greater than background concentrations and mean concentrations exceed contamination standards from the German Federal Soil Protection Act. Tributary streams are not a source for the elevated trace metal concentrations found along the lower Dill and Lahn Rivers and mined areas will likely not serve as a source of future heavy metal pollution. The results of this study indicate that the mining process did not release large quantities of metals to the fluvial system.

Addressing societal challenges through nature-based solutions: How can landscape planning and governance research contribute?

Nature-based solutions (NBS) in river landscapes, such as restoring floodplains, can not only decrease flood risks for downstream communities but also provide co-benefits in terms of habitat creation for numerous species and enhanced delivery of diverse ecosystem services. This paper aims to explore how landscape planning and governance research can contribute to the identification, design and implementation of NBS, using the example of water-related challenges in the landscape of the Lahn river in Germany. The objectives are (i) to introduce the NBS concept and to provide a concise definition for application in planning research, (ii) to explore how landscape planning and governance research might support a targeted use and implementation of NBS, and (iii) to propose an agenda for further research and practical experimentation. Our methods include a focused literature review and conceptual framework development. We define NBS as actions that alleviate a well-defined societal challenge (challenge-orientation), employ ecosystem processes of spatial, blue and green infrastructure networks (ecosystem processes utilization), and are embedded within viable governance or business models for implementation (practical viability). Our conceptual framework illustrates the functions of NBS in social-ecological landscape systems, and highlights the complementary contributions of landscape planning and governance research in developing and implementing NBS. Finally, a research and experimentation agenda is proposed, focusing on knowledge gaps in the effectiveness of NBS, useful approaches for informed co-design of NBS, and options for implementation. Insights from this paper can guide further studies and support testing of the NBS concept in practice.

Impacts of river impoundment on dissolved heavy metals in floodplain soils of the Lahn River (Germany)

The effects of changing soil moisture conditions and oxidation–reduction (redox) processes on dissolved fractions of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), manganese (Mn), lead (Pb) and zinc (Zn) were studied in floodplain soils in the Lower Lahn Valley (Germany). Multiple weirs and locks affect the groundwater levels in the adjacent river banks by modifying the river’s discharge rate. Redox conditions act as a key factor for sorption and desorption processes and are strongly regulated by groundwater levels. Hence, floodplain soils situated up- and downstream of impounded river segments were characterized by various contents of their mobile heavy metal fraction. To quantify the variations of the dissolved heavy metal concentrations during seasonal and periodic fluctuations of the groundwater levels, a 2-year field study was conducted. The results indicated that higher seasonal changes of river discharge downstream of a weir caused higher amplitudes of groundwater levels, redox changes and variations in dissolved As, Fe and Mn in soil depths (50–60 cm) with a strong groundwater influence. Upstream of a weir, higher dissolved concentrations and more smooth variations of As, Fe and Mn dominated within the same depths. A high rise of capillary waters within the same study site caused significant enrichments of dissolved Cd and Zn in the middle (25–35 cm) of the soil profile. The comparison of floodplain soils along the Lahn River showed how the stream regulations influence heavy metal concentrations of soil pore waters, which may in turn influence the quality of the river water.

Off-line and On-line Enrichment of α-Aminocephalosporins for Their Analysis in Surface Water Samples Using CZE Coupled to LIF

This study examines the potential of application of capillary zone electrophoresis (CZE) coupled to laser-induced fluorescence (LIF) detection involving derivatization with fluorescamine for the separation and determination of α-aminocephalosporins in surface water samples. Via their α-amino group, the non-fluorescent cefadroxil and cefalexin are capable of forming a highly fluorescent derivative via their reaction with fluorescamine. This reaction permits the selective and sensitive detection of aliphatic primary amines when combined with CE/LIF, which was achieved with a low-noise diode laser emitting at a wavelength of 375 nm (P cw = 5.6 mW) in combination with a fiber optic-coupled detection cell. Different types of solid phase extraction cartridges were investigated to select the optimum solid phase providing maximum recovery for the studied antibiotics, which were extracted from spiked Lahn river water samples. Highest recovery (cefalexin 109.4 ± 3.9 % and cefadroxil 92.6 ± 4.0 %) was reached with a polymer-based solid phase (Oasis HLB cartridge), with which a tenfold off-line enrichment was obtained. On-line enrichment was achieved by sweeping and large volume sample stacking (LVSS). The high complex formation constant between the formed derivative and 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) and the low electric conductivity of the extract after the off-line enrichment constitute an ideal basis for additional analyte enrichment by sweeping and LVSS. The enrichment efficiency obtainable with this on-line enrichment step (after having filled the complete capillary with the sample solution) in comparison to field-amplified sample stacking (FASS) reaches approximately an additional 25-fold improvement. With the developed method, combining off-line and on-line enrichment with optimized fluorescence detection, detection limits as low as 4.9 and 7.5 ng L−1 are obtained for cefalexin and cefadroxil, respectively, with a starting sample volume as low as 50 mL. The high repeatability and accuracy of the proposed strategy permits its application to the analysis of α-aminocephalosporins in surface water samples. Its applicability can be extended to other environmental compartments and other types of primary amino group containing compounds. In addition, it provides equivalent sensitivity to other methods using more expensive equipment like HPLC–MS/MS.

Development of multiple linear regression models as predictive tools for fecal indicator concentrations in a stretch of the lower Lahn River, Germany

Since rivers are typically subject to rapid changes in microbiological water quality, tools are needed to allow timely water quality assessment.A promising approach is the application of predictive models. In our study, we developed multiple linear regression (MLR) models in order to predict the abundance of the fecal indicator organisms Escherichia coli (EC), intestinal enterococci (IE) and somatic coliphages (SC) in the Lahn River, Germany. The models were developed on the basis of an extensive set of environmental parameters collected during a 12-months monitoring period. Two models were developed for each type of indicator:1) an extended model including the maximum number of variables significantly explaining variations in indicator abundance and 2) a simplified model reduced to the three most influential explanatory variables, thus obtaining a model which is less resource-intensive with regard to required data.Both approaches have the ability to model multiple sites within one river stretch. The three most important predictive variables in the optimized models for the bacterial indicators were NH4–N, turbidity and global solar irradiance, whereas chlorophyll a content, discharge and NH4–N were reliable model variables for somatic coliphages.Depending on indicator type, the extended mode models also included the additional variables rainfall, O2 content, pH and chlorophyll a.The extended mode models could explain 69% (EC), 74% (IE) and 72% (SC) of the observed variance in fecal indicator concentrations. The optimized models explained the observed variance in fecal indicator concentrations to 65% (EC), 70% (IE) and 68% (SC). Site-specific efficiencies ranged up to 82% (EC) and 81% (IE, SC). Our results suggest that MLR models are a promising tool for a timely water quality assessment in the Lahn area.

Recent changes in heavy metal contamination at near-channel positions of the Lahn River, central Germany

Short-term monitoring of heavy metal concentrations along rivers affords the opportunity to examine the persistence of contaminants in the fluvial environment. This paper examines changes in the concentrations of Cu, Pb, and Zn at near-channel positions along a 75-km reach of the Lahn River, an agrarian watershed in central Germany, between 2000 and 2007. Thirty-three sites sampled in 2000 were re-sampled in 2007 in order to document changes in trace metal contamination. The concentrations of Cu and Pb decreased between 2000 and 2007, whereas the concentration of Zn was statistically unchanged. The Pb concentration decreased at 82% of the sample sites over the study period, whereas Cu concentrations decreased at 70% of the sites. Site-to-site variation in the concentrations of Pb with distance downstream from potential source areas declined between 2000 and 2007. The downstream variation in Cu also decreased over the study period, albeit to a lesser degree. The decrease in Pb, and to a lesser extent Cu, concentrations adjacent to the Lahn River appears to reflect the recent reductions in the release of trace elements to the environment. Zinc concentrations were unchanged, suggesting that it is derived from different sources than are Cu and Pb or is cycling through the watershed differently than Cu and Pb. Lower concentrations of Cu and Pb in channel bank sediments translate to a reduced risk of future downstream heavy metal pollution in the study area.