Spatial analysis of riverine microplastic in a Rhine floodplain soil in Germany

<p>The Rhine River flows through six European countries and is in exchange with diverse land use forms and human activities that potentially release microplastics (MPs). The Rhine interacts permanently with its surrounding banks and floodplains by changing water-levels. Several studies have documented the presence of MPs in the Rhine along its course as well as in its tributaries. However, the spatial distribution of MPs due to certain flood events in alluvial floodplains remains widely unclear. The knowledge about the amount and distribution of MPs and on their potential entry pathways into Rhine floodplains is essentially important for an ecological risk assessment. In this study, we analysed the amount and distribution of MPs in a floodplain soil in the nature reserve Merkenich-Langel, in the northern periphery of Cologne (Germany). We hypothesize that MPs are transported by the Rhine and are deposited at the site during flood events. For spatial analysis we used the MIKE software (DHI A/S, Hørsholm Denmark) merged with a digital terrain model of the study site to analyse past flood events and their potential deposition of MP. We chose three sampling transects located within the past flooded area each with three sampling spots with increasing distance and elevation to the river. Samples were taken from two different soil depths (0–5 cm and 5–20 cm) and the samples of the three sampling spots and same depth were combined to one mixed soil sample per transect. MP concentrations were analysed via ATR-FTIR and µ-FPA-FTIR spectroscopy after density separation and enzymatic-oxidative purification. We found an increase of MP concentration per kg of dry soil in the depth 5–20 cm with increasing distance to the river ranging from 25.612 particles/kg to 85.076 particles/kg. The results of MP concentration in 0–5 cm topsoil layer will be compared to the concentration in the soil depth of 5–20 cm. We correlate these results to the frequency of flood events.</p>

Holocene alluvial floodplains in Belgium: from natural to human-dominated environments

<p>Rivers and alluvial floodplains are dynamic environments that experience both natural and anthropogenic impacts. Sustainable management of these ecosystems requires a thorough understanding of the functioning of floodplains and their sensitivity to changes in driving forces, including anthropogenic land-cover change. Looking at past human-environment interactions in river catchments can help to develop such sustainable management strategies for the future.</p><p>During the Early and Middle Holocene, most floodplains in northeastern Belgium were stable environments, mainly driven by natural forces, resulting in large marshes where peat accumulated and river channels were absent or small. During the Late Holocene, these environments changed completely towards single channel meandering rivers with overbank deposits, impeding peat accumulation. These changes can to a large extent be linked to increasing human activities in the catchment. However, the timing of this change in floodplain geoecology strongly varies within and between different catchments.</p><p>Five river catchments in northeastern Belgium with varying soil properties, topographies, and durations and intensities of human impact were selected in this study, to uncover regional differences in land-cover evolution. The catchments of Dijle (750 km²), Grote Gete (300 km²) and Mombeek (90 km²) are located in the central Belgian loess belt, whereas the Grote Nete (525 km²) and Zwarte Beek catchments (50 km²) are situated in the sandy Campine region. A multi-proxy approach, including sedimentological proxies, pollen, and macrobotanical remains, was chosen to reconstruct alluvial floodplain characteristics and anthropogenic land-cover changes. We constructed a database of 27 records for these five catchments (of which 9 containing pollen, 4 containing macrobotanical remains, and 14 containing both) for which 132 radiocarbon dates in total provide a chronostratigraphic framework.</p><p>Qualitative, semi-quantitative (NMDS) and quantitative (REVEALS) analyses of the palynological data revealed regional differences in the initiation and intensity of human impact. From the Neolithic period onwards, deforestation is detected in both the loess and sandy region, although the loess belt underwent a more rapid and severe reduction of woodland. While this deforestation is accompanied by an increase in cropland in the loess region from the Bronze Age onwards, the sandy region only starts to show limited agriculture from the Iron Age onwards, related to its later and less dense human occupation.</p><p>While the amount of records and their resolution is rather low in the sandy region, the numerous and detailed records of the loess belt also allow detection of more local and short-term effects (< 200 years) of changes in human impact. A decrease in human impact during the Dark Ages, which can be related to the decreased population density in Europe during the first millennium AD, is visible: hillslope–floodplain connectivity reduced due to the regeneration of vegetation barriers, in turn lowering sediment input, which facilitated local reactivation of peat growth and regrowth of the natural alder-carr floodplain vegetation. After this temporary decrease, human impact on floodplain geoecology started to increase again up till modern times. The impact also got more direct, as peat extraction from the floodplains became common practice, especially in the sandy Campine region.</p>

Contaminant Removal and Precious Metal Recovery by Lateral Channel Filtration in Mining-Impacted Alluvial Floodplains

Water quality impacts from artisanal and small-scale alluvial (placer) gold mining operations occur in developing economies across several continents including Asia, Africa, and South America. They often occur in remote and/or resource-poor settings in which mitigation strategies must contend with extreme seasonal variation in river flow as well as the economic incentive to periodically churn (mine) alluvial floodplains without riparian restoration. A novel strategy addressing these constraints is herein explored which employs the alluvial floodplain for filtration-driven removal of particulate contaminants and gold from streams. This process of lateral channel filtration is explored in the Rio Nambija of southern Ecuador, in terms of success in achieving the hydraulic objective of passively driven lateral flow, and the corresponding removal of particulate contaminants (e.g., total mercury, lead, iron, and manganese) by filtration. Accumulation of gold was examined to evaluate whether incorporation of this proposed practice in alluvial (placer) mining can reduce particle-bound contaminants in streams and simultaneously increase economic benefit. Excavation of channels lateral to mining-impacted streams was shown to achieve the hydraulic, water quality, and economic (gold accumulation) objectives. The modest flow capture for any given lateral segment, along with the months-long timescale associated with economic gold accumulation and clogging by suspended solids, dictate a “cultivation” process whereby multiple lateral segments are worked annually.

Quantitative reconstruction of Holocene vegetation cover in Flanders, Belgium - a study based on pollen-records from alluvial floodplains

<p>Rivers and alluvial floodplains are dynamic environments facing natural and anthropogenic impacts. A thorough knowledge of the functioning of alluvial floodplains and their sensitivity to changes in internal and external driving forces is required for sustainable management of these ecosystems.</p><p>During the Early and Middle Holocene, most floodplains in northern and central Belgium were stable environments with limited floodplain aggradation resulting in the formation of peat. During these times, floodplains consisted mainly of large marshes where peat accumulated and river channels were absent or small. During the Late Holocene, these environments changed completely towards single channel meandering rivers with overbank deposits, impeding peat accumulation, largely as a result of increasing anthropogenic impact. However, this evolution in floodplain geoecology is diachronous as some river valleys transform a few thousand years before others.</p><p>Previous research already showed that river systems respond non-linearly to changes in land-use and land-cover in their catchments, as land-use intensity and slope-channel coupling need to cross a certain threshold to result in significant change. Hence, the differences in timing of floodplain response can to some extent be related to different land-use trajectories in the river catchments. Based on previous qualitative and semi-quantitative research the exact land-cover threshold, i.e. the land-use intensity required to result in transformation of the fluvial system, as well as the timing at which this threshold is crossed, could not be detected. Hence, a quantitative assessment of the resilience of floodplain environments to regional land-use changes is needed. A successful pilot REVEALS-based reconstruction of the Dijle catchment, showed a decrease in forest cover from the Bronze Age onwards, accompanied by an increase in the proportion of cereals.</p><p>In this study, we constructed a database of pollen-records collected in the eastern part of Flanders, mainly retrieved from river floodplains, as deposits from large lakes are not available in the area. We selected sites with varying soil properties, topographies, and histories of human impact in their catchments, to uncover regional differences in land-cover evolution through the application of the REVEALS model. To assess the applicability of this model to alluvial deposits, modern pollen data will be included and outcomes will be compared to modern vegetation maps. In addition, vegetation reconstructions will be compared with historical maps (available from 1778 AD onwards).</p><p>Results will help to answer questions regarding the sensitivity of Flanders to (future) environmental changes. Our study contributes to the understanding of Holocene land-cover change and its drivers, by providing quantitative vegetation cover reconstructions for Belgium that are currently lacking in the European REVEALS reconstructions. Moreover, it extends the application of the REVEALS model to pollen-records retrieved from alluvial deposits.</p>

Amazonian dark earths in the fertile floodplains of the Amazon River, Brazil: an example of non-intentional formation of anthropic soils in the Central Amazon region

ABSTRACT Amazonian dark earths (ADEs) are fertile soils created by pre-Columbian Amerindian societies of the Amazon Basin. However, it is still not clear whether these soils were produced intentionally to improve infertile Amazonian upland soils or if they resulted from the accumulation of organic matter from sedentary settlements. This study characterizes the ADEs found in the naturally fertile alluvial floodplains of the Amazon River in the Central Brazilian Amazon according to total, exchangeable, and available contents of elements and organic carbon in soil profiles. ADEs contained higher levels of available elements and total P, Ca, Zn, and Cu. High total Cr, Ni, Co, and V content in these soils indicate that mafic minerals contributed to their composition, while higher contents of P, Zn, Ba, and Sr indicate anthropic enrichment. The presence of ADEs in floodplain areas strongly indicates non-intentional anthropic fertilization of the alluvial soils, which naturally contain levels of P, Ca, Zn, and Cu higher than those needed to cultivate common plants. The presence of archaeological sites in the floodplains also shows that pre-Columbian populations lived in these regions as well as on bluffs above the Amazon River.

Distribution, habitat, morphological diversity and genetic interrelations of native Vigna in the Pilbara, Western Australia

A 2-week road trip was made through the Pilbara region to collect seed of native Vigna species. Thirty-two new accessions were collected, all of which were within what can be broadly described as the V. lanceolata Benth. complex. All 32 accessions were amphicarpic, rhizomatous, trailing or vining perennials. The largest and most widely distributed group of 21 accessions belonged to the Silverleaf morphotype and a further nine accessions belonged to the Central morphotype. Two accessions from the Karratha region were of a recently described diminutive species, V. triodiophila. The Silverleaf accessions were all collected from grassy woodlands on river levees and alluvial floodplains. The Central accessions were collected from a more diverse range of habitats, albeit again mostly in wetter or ‘run-on’ parts of the landscape. Measurements of selected traits on a subset of accessions grown for seed increase in Townsville indicated that the Pilbara Silverleaf and Central accessions were comparable with accessions of these morphotypes from elsewhere in northern Australia. Healthy, viable F1 hybrids were readily obtained from crosses between accessions from all three Vigna groups collected from the Pilbara, indicating that all belong to same primary gene pool. This includes V. triodiophila, notwithstanding its taxonomy. Healthy, viable and fertile F1 hybrids were also obtained between the Pilbara accessions of both the Silverleaf and Central morphotypes and respective accessions of these morphotypes from elsewhere in northern Australia. The F1 hybrids between V. triodiophila and both the Silverleaf and the Central accessions exhibited near-normal plant phenotype in terms of the size of their vegetative and reproductive structures, indicating that the diminutive size of V. triodiophila is a recessive trait. The most plausible explanation is that V. triodiophila is a dwarf variant of the Central morphotype, which it most closely resembles apart from its size. The fact that the F1 hybrids between V. triodiophila and two Pilbara Central accessions were fully self-fertile supports that conclusion, while the recovery of dwarf segregants from small numbers of F2 and backcross progeny from one of the crosses indicates that the dwarf trait may involve just a single gene. These 32 new accessions extend the range of climatic and edaphic environments, especially at the harsher end, from which accessions of V. lanceolata have been collected and seeds conserved.