Floodplain Soils Research Articles

Evaluating floodplain organic carbon across a gradient of human alteration in the boreal zone

River corridors play an important role in the carbon cycle as sites of carbon transport, storage, and transformation. Floodplain soil organic carbon (OC) and dead, downed large wood (LW) are two of the largest OC stocks in rivers. Human modifications of river corridors, such as damming and floodplain land-use change, have likely modified floodplain OC storage and retention through removal of LW and potential reduction of OC concentrations in soils. However, the effect of human alterations on floodplain OC storage is poorly understood. We measured floodplain soil OC and downed LW loads on three rivers in northern Sweden that display a gradient in the degree of human alteration. The Muddus River is located in a national park and is unaltered. The Vindel River is free-flowing but has been modified via logging and other land-use changes within the floodplain. The Ume River is dammed along its length and has also experienced floodplain logging and land-use change. We used statistical models to determine which factors are associated with differences in mineral soil OC and LW among rivers with different degrees of human alteration. We find the highest mineral soil OC concentrations on the unaltered Muddus River (mean ± standard error (SE) = 3.70 ± 0.59%; median = 3.81%), with lower soil OC along the Vindel (mean ± SE = 1.44 ± 0.22%; median = 0.72%) and Ume (mean ± SE = 2.47 ± 0.44%; median = 1.12%) Rivers. The Muddus River also has the highest downed LW loads (mean ± SE = 22.25 ± 6.99 m3 ha−1) compared to the Vindel (mean ± SE = 3.10 ± 1.26 m3 ha−1) and Ume (mean ± SE = 7.26 ± 3.53 m3 ha−1) Rivers. Variations in soil OC and downed large wood loads indicate that damming may reduce floodplain OC in these boreal systems through reducing lateral channel-floodplain connectivity and longitudinal connectivity. Logging and other land-use changes likely reduce OC inputs to the floodplain surface through removal of organic matter and LW. Further research is needed to elucidate the impact of human modifications on floodplain OC across diverse regions and to inform river restoration efforts to enhance floodplain OC storage.

Roots reinforcement by riparian trees in restored rivers

Riparian vegetation directly and indirectly affects many fluvial processes. In particular, the root system of riparian trees and shrubs may greatly influence river morphodynamics by imparting higher shear strength to riverbanks compared to unvegetated channel margins. Therefore, the bank-stabilizing role of riparian vegetation should be quantitatively considered in river restoration projects. This work aims to quantify the additional strength due to the root systems of naturally established riparian vegetation after two river restoration projects carried out in the Italian Alps (Ahr and Mareit rivers, South Tyrol). These projects represent the largest restoration interventions carried out so far in Italian rivers, and the two sites feature contrasting channel patterns along with varying river-floodplain dynamics.The mechanical properties of roots and their distribution in the floodplain soils in the two sites have been measured to estimate root cohesion distribution associated to gray alder (Alnus incana) and pioneering willows (Salix spp.).Results show that roots of plants colonizing the gravelly substrate of building islands in the Mareit River have less tensile strength than those belonging to trees growing in the floodplain of the Ahr River, rich in fine sediments. However, the higher root contribution to the overall soil strength occurs in the island site, due its lack of fine sediments.

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.

Effect of the water regime, crop rotation and fertilizers in biogenic matters leaching into ground water and surface water

The purpose of our work was to establish features of formation of filtration processes and to define prevention measures towards the nutrients leaching from drainage soils into the ground waters. Our researches were carried out on typical drained floodplain soils of Panfil Research Station, Institute of Agriculture of National Academy of Agrarian Science (floodplain of Supiy River, Yahotyn district, Kiev region, Ukraine) in 2016-2018. The arable layer of peatlands had high level of decomposition (50-60%) with gross nitrogen contamination of 1.9%, phosphorus

Application of biochar prepared from ethanol refinery by-products for Hg stabilization in floodplain soil: Impacts of drying and rewetting

This study evaluated three biochars derived from bioenergy by-products — manure-based anaerobic digestate (DIG), distillers’ grains (DIS), and a mixture thereof (75G25S) — as amendments to stabilize Hg in contaminated floodplain soil under long-term saturated (up to 200 d) and cyclic drying and rewetting conditions. Greater total Hg (THg) removal (72 to nearly 100%) and limited MeHg production (<65 ng L−1) were observed in digestate-based biochar-amended systems under initial saturated conditions. Drying and rewetting resulted in limited THg release, increased aqueous MeHg, and decreased solid MeHg in digestate-based biochar-amended systems. Changes in Fe and S chemistry as well as microbial communities during drying and rewetting potentially affected MeHg production. Digestate-based biochars may be more effective as amendments to control Hg release and minimize MeHg production in floodplain soils under long-term saturated and drying and rewetting conditions compared to distillers’ grains biochar.

Assessment of potentially harmful elements in floodplain soils and stream sediments in Ile-Ife area, South-western Nigeria

The enrichment of potentially harmful elements (PHEs) in stream sediments (SS) and floodplain soils (FS) poses great environmental hazards to water bodies and other parts of the ecosystem. The aim of this research was to evaluate the distribution pattern of selected PHEs (Cu, Pb, Zn, Co, Mn, As, Cd, V, Cr, Ni, Th, Sr and La) in SS of selected rivers that drain Ile-Ife area and their adjacent FS, to ascertain the pollution status of these elements in the study area. Sixty samples (40 SS and 20 FS) were purposely collected for this study; the samples were analysed with ultra-trace inductively coupled plasma mass spectrometry method (ICP-MS). The PHEs results showed decreasing trend of average contents of PHEs studied; Mn > Zn > V > Cr > Pb > La > Sr > Cu > Ni > Co > Th > As > Cd for both SS and FS. Also, PHEs concentration in the studied geo media showed a significant level of enrichment as observed from the results. Elemental association showed positive correlation for topsoil, Pb/Zn = R2, 0.85 and negative correlation for topsoil Cr/Zn = R2 0.02 among the other PHEs. Source apportionment showed that the studied metal enrichment is largely anthropogenic rather than geogenic. Geoaccumulation and metal ratio indexes indicated that FS and SS studied have received significant PHEs of between moderately to strongly polluted, which implies significant environmental implications in the study area.

Immobilization of agricultural phosphorus in temperate floodplain soils of Illinois, USA

Nutrient losses from Mississippi watersheds degrade downstream water bodies. As forested floodplains intercept agricultural drainage waters, a limiting nutrient like phosphorus (P) could potentially be sequestered in forest soils, reducing P loss to the Gulf of Mexico. Thus far, the role of temperate deciduous floodplain soils for P has not been extensively investigated in the Midwestern United States. The objective of this study was to investigate the buffering capacity of P in floodplain soils using soil biochemical chemical assays, 31P nuclear magnetic resonance spectroscopy (NMR) and P K-edge X-ray absorption near edge structure spectroscopy (XANES). Phosphorus reaction dynamics were compared between floodplains and surrounding upland soils in east-central Illinois, USA. Total organic P was significantly greater in the floodplain (277.27 ± 159.51 mg kg−1) than that in the upland (113.04 ± 74.88 mg kg−1), illustrating its buffering capacity. Notably, microbial biomass P (averaged 13.08 mg kg−1) was greater in the floodplain than that in the upland. The results of 31P NMR analysis showed the presence of organic P (e.g., orthophosphate monoesters) and orthophosphate. The P K-edge XANES analysis shows that these inorganic and organic P species are predominantly adsorbed in calcite and precipitated as calcium phosphate in floodplain soils. These findings suggest that temperate deciduous floodplain soils have a great potential to immobilize agricultural P in the Upper Mississippi watershed.

How Simulations of the Land Carbon Sink Are Biased by Ignoring Fluvial Carbon Transfers: A Case Study for the Amazon Basin

Summary Land-surface models are important tools for simulation of the past, present, and future capacity of terrestrial ecosystems to absorb anthropogenic CO2 emissions. However, fluvial carbon (C) transfers are presently neglected in these models. Using the Amazon basin as a case study, we show that this negligence leads to significant underestimation of the net uptake of atmospheric C while terrestrial C storage changes are overestimated. These biases arise from the fact that C—in reality, leached from soils and exported through the river network—is instead represented as partly being respired and partly being stored in soils. Moreover, these biases scale mainly to the fluvial C export to the coast, despite aquatic CO2 emission to the atmosphere being the major pathway of riverine C exports. We further show that fluvial C transfers may change significantly in response to changes in either hydrology or in atmospheric C uptake by vegetation.

Selection of direct, residual and cumulative doses of zinc and boron fertilizers for potato-rice-rice pattern in floodplain soil

A study was conducted to evaluate different doses of Zn and B along with their application schedule for the component crops in potato-rice-rice pattern in floodplain soil. The experimental layout was Randomized Complete Block Design with 3 replications. As treatment, zinc and boron were applied to the component crops of the pattern in different distributions so that their direct, residual and cumulative effects could be estimated. Other nutrients i.e., N, P, K and S were used equally at recommended rates for all plots. In such a 3-crop pattern, application of 4.0 kg Zn ha−1 and 1.5 kg B ha−1 at a time to the first crop or 2.0 kg Zn ha−1 to each of the first two crops along with 1.5 kg B ha−1 to the first crop was found sufficient to achieve satisfactory yield, system productivity, nutrient uptake by crops, and protein and Zn concentrations of crop produce. Zinc and boron containing fertilizers need not to apply in each of the component crops of a cropping pattern potato-rice-rice in floodplain soil. Each fourth crop is essential to be fertilized with 4.0 kg Zn ha−1 and 1.5 kg B ha−1.

Impact of multiple drying and rewetting events on biochar amendments for Hg stabilization in floodplain soil from South River, VA

Frequent drying and rewetting due to flooding/precipitation and drainage events in floodplains induces changes in biogeochemical conditions that may influence the effectiveness of in situ Hg stabilization using biochars as soil amendments. This study evaluated two selected biochars anaerobic digestate (DIG) and sulfurized hardwood (MOAK)) as potential amendment materials in moderately reduced floodplain soil under repeated drying and rewetting events using a modified humidity cell protocol. Enhanced release of filter-passing (0.45-μm) total Hg (THg) and MeHg was observed at early times. Elevated concentrations of 0.45-μm THg were associated with DOC and Mn in sediment control and biochar-amended systems. Elevated concentrations of MeHg were associated with Mn in the MOAK-amended system. Thereafter, decreases in 0.45-μm (up to 57%) and unfiltered THg (up to 93%) were observed. As wetting and drying events continued, decreases in pH and alkalinity as well as increases in SO42− (up to 796 mg L−1) and Ca (up to 215 mg L−1) were observed in the MOAK-amended systems with the microbial community shifted towards sulfur-oxidizing bacteria, indicating microbially-driven oxidation of MOAK. Although results of S K-edge X-ray absorption near edge structure (XANES) analysis suggest polysulfur is the predominant S phase in both MOAK- and DIG-amended systems, microbially-driven oxidation of DIG was not observed. Polysulfur in MOAK from the sulfurization process is more bioavailable to sulfur oxidizing communities than in DIG under the repeated drying and wetting conditions. Results of this study suggest biogeochemical conditions as well as biochar properties should be considered when planning full-scale field applications.

Classification and assessment of agricultural potential of the lower Niger floodplain soils of Atani, Southeastern Nigeria

The soils of Atani floodplain in Anambra State of Nigeria contribute significantly to the food production of the State, hence the need to understand their behavior in order to enhance their management and productivity. Profile pits were sited along three physiographic units viz: levee crest, levee slope and flood basin. Soil samples were collected from the profile horizons and subjected to standard laboratory procedures. Characterization of the soils was based on their morphological, physical and chemical properties. Soil classification was carried out using the USDA Soil Taxonomy and correlated with FAO/IUSS World Reference Base. Its agricultural potential was assessed using the fertility capability classification. The soils were deep. Topsoil colour was dominantly blackish black (10YR 3/2). Mottles were pervasive; an indication of impeded drainage conditions. The soils were predominantly fine textured. Soil pH values ranged from 4.8 to 6.2. Exchangeable Calcium was low to moderate (2.6-8.2 cmol kg−1); Magnesium was moderate to high (1.6-6.8 cmol kg−1); Sodium was high to very high (1.0-2.5 cmol kg−1), while potassium was high (1.2-4.2 cmol kg−1). Cation exchange capacity values ranged from 11.6 to 42.6 cmol kg−1. Total nitrogen was very low to low (0.14-1.12 g kg−1), while organic carbon was low to moderate (0.4-15.2 g kg−1). Available phosphorus was very low to high ranging from 0.93 to 31.71 mg kg−1 while base saturation ranged from 64 to 93%. The soils were classified as Typic Fluvaquents (Typic Fluvisols), Fluvaquentic Endoaquepts (Endostagnic Cambisols) and Fluventic Endoaquepts (Endostagnic Cambisols) according to the USDA and FAO/IUSS. The fertility capability evaluation of the soils revealed that the pedons were Lgn in classification due to limitations in drainage.&#x0D; Key words: alluvium, cambic horizon, Inceptisols, lithologic discontinuity

Soil suitability evaluation of Babayau flood plain for selected arable crop cultivation in Ardo-kola, Taraba State, Nigeria

The study's objective was to characterize the soils and carry out suitability evaluation of floodplain soils in Ardo-Kola, Taraba State. Six (6) profile pits were dug from two physiographic units and the most predominant land use (woodland area and arable land area). Three (3) profile pits were dug on each of the identified units using standard dimension. Soil morphological results indicated that the soils were sub-angular blocky, strong to fine structure, very sticky, hard when dry and firm when moist in the woodland area. Colour ranged from pale brown 10YR (6/3) to dark greyish brown 10YR (4/2). Soils in the arable land area were mostly very sticky, firm when moist and hard when dried. The colour ranged from light yellowish-brown 10YR (6/4) to dark grey 10YR (4/1). Results of particle size distribution were sandy loamy and loamy sand across the pedons. Bulk density values ranged from 1.50 to 1.67gm/cm3, and total porosity ranged from 37 to 43% respectively. The soils were generally moderately acidic to slightly acidic, organic carbon and total nitrogen was low (&lt;2% and &lt;0.15%), calcium and magnesium were rated medium (2-5cmol/kg and 0.3-1.0cmol/kg) respectively. Base saturation values were rated medium (50-80%) to high (&gt;80%) across the pedons. Soil suitability result for the woodland area showed overall suitability for maize in pedon BYF1 was S3w (marginally suitable) with limitation in nutrient availability and suitable (S1) in pedon BYF5. Arable land area was also marginally suitable (S3) with limitation in oxygen availability except for pedon BYF4, which was not suitable (N) for maize cultivation. Woodland area was moderately suitable (S2) and suitable (S1) for the arable land area with limitation in texture except for pedon BYF 3 with limitation in oxygen availability. Rice production is encouraged in the arable land area while maize in the woodland area using fertilizers and organic materials to ameliorate low fertility limitations observed in the study area.

Evaluating the Effectiveness of Some Productivity Models on Floodplain Soils of Wukari Area, Northern Guinea Savanna, Nigeria

A study on quantifying the productivity of Wukari flood plain soils using Neill’s Productivity Index (PI), Modified Neill’s Productivity Index (PIm) and Riquier Productivity Index (RI) was carried out. The applicability and validity of the productivity index models were determined using rice as a test crop. Result showed significant relationships with coefficients of determination (R2) of 0.7158, 0.7204 and 0.8778 found between grain yield of rice (Y) and PI, PIm and RI values respectively. The highest and the lowest grain yield of rice to a reasonable extent correspond to the higher and the lower productivity index values, respectively. Higher productivity indices explained higher mean grain yield of rice. The productivity indices values decreased with the decrease in grain yield. The grain yield of grain followed productivity index predictions and are hereby recommended as tools of soil productivity assessment in the study area.

Assessment of the Effects of Seasonal Flooding on the Properties of Floodplain Soils of Wukari, Taraba State, Nigeria

The aim of this study was to examine the effects of seasonal flooding on the properties of floodplain soils of Wukari Area of Taraba state. The treatments consisted of five different locations of Gidan-Idi, Gindin-Dorowa, Tsokundi, Rafin-Kada and Nwuko and three different soil sample depths of 0-20 cm, 20-40 cm, and 40-60 cm laid out in a completely randomized design (CRD) and replicated three times. Soil samples were collected from each plot in 2016 and 2017. All soil samples were analyzed for physical and chemical properties. The results obtained were subjected to analysis of variance and means separated using F-LSD test at p≤.05. The results of the soil properties analysis showed that some of the determined parameters were significantly different at the different sample locations at p≤.05. The soils of Wukari Floodplains are mostly clay loam in texture having very slightly acid to neutral soil reaction, moderate organic matter, low total N, moderate available P, low exchangeable bases and CEC. The flood plain soils were moderate in soil fertility, a confirmation of the general characteristic of Savanna soils. The soils were not deficient in micronutrients. Seasonal flooding had significant (positive) influence on some physical and chemical properties of the flood plains most particularly at Rafin-Kada.

Floodplain Inundation and Salinization From a Recently Restored First‐Order Tidal Stream

AbstractThe systematic response of coastal ecosystems to inundation and salinity exposure is fundamental to their ecology and biogeochemical function. Here we observe and model freshwater‐seawater interactions in a first‐order stream—floodplain system where tidal access was recently restored. Subsurface flow and transport modeling were used to quantify and better understand the interplay of processes, properties, and conditions that control water level and salinity in the floodplain to the tidal stream. Water levels in the stream were highly correlated with tidal forcing, which resulted in episodic inundation of the floodplain at quasi‐monthly frequency. The tidal stream is the only source of salinity to the floodplain, yet shallow groundwater salinity was considerably higher than average stream salinity. The low‐permeability clay floodplain soils limit lateral groundwater flow and transport, resulting in floodplain groundwater and salinity dynamics driven almost exclusively by infiltration during inundation events. As inundation occurs during high tide, estuarine waters reach the floodplain with minor attenuation in salinity from the stream's freshwater discharge. Infiltration and salinity exposure are topography controlled and regulated by ponding depth and duration, seasonal ground saturation, and depth to water table. The model suggests that floodplain salinity is currently in an early stage of transition from pre‐restoration freshwater conditions and will not reach equilibrium for ~20 years. These findings have broad relevance for understanding how and over what time scales coastal ecosystems will respond to increasing seawater exposure from sea level rise, ocean‐originating storms, and changes in natural and man‐made barriers.

Quantifying denitrification following floodplain restoration via the two-stage ditch in an agricultural watershed

In agricultural streams, constructed floodplains have been shown to expand bioreactive surface area and enhance nitrate (NO3−-N) removal via microbial denitrification, thereby reducing export to downstream ecosystems. At the Shatto Ditch Watershed (Indiana, USA), 0.6 km of two-stage ditch was constructed at the watershed outlet in 2007, while an additional 3.7 and 2.7 km were constructed in 2017 and 2018, respectively. We quantified denitrification following floodplain construction using experimental incubations of stream sediments and floodplain soils from Spring 2017 to Spring 2019. We measured dissolved dinitrogen gas (N2) concentrations using membrane inlet mass spectrometry (MIMS) and found that denitrification on unconsolidated stream sediments was minimally impacted by stream dredging during two-stage construction in 2017 and 2018. In contrast, even one year after the 2017 construction, denitrification on floodplain soils fell below detection limits; we finally observed measurable rates in Spring 2019. As predicted, stream sediment denitrification was driven by water column NO3−-N concentration, while organic matter limited denitrification on floodplain soils. Floodplains constructed via the two-stage ditch can increase NO3−-N removal by >20% in agricultural watersheds, representing an effective ecological engineering solution to combat downstream eutrophication. However, our results also show that denitrification on floodplain soils may take longer to recover from construction-related activities as organic matter builds up more slowly over time. As such, lags in the recovery or enhancement of ecosystem function are important to consider when documenting restoration success.

THE CONTENT OF VITAMINS AND HEAVY METALS IN BERRIES OF WILD BLACKCURRANT OF YAKUTIA

The results of research on the content of vitamins (E, B1, B2, B6 and C) and heavy metals zinc, iron, cobalt, mercury, as well as iodine in the soil and berries of wild black currant growing on forest and floodplain soils of the Central and Vilyuisk zones of the Republic of Sakha (Yakutia) are presented. It was established that the maximum amount of vitamins in berries and leaves of black currant is contained in the conditions of Amginsky and Ust-Aldan districts: vitamin E – 90.07–134.25 mg/kg; C – 1259.87–2092.4 mg/100g; B1 – 2.28–2.72 mg/kg; B2 – 17.83–24.92 mg/kg; B6 – 24.4–37.93 mg/kg. At the same time, the content of the studied vitamins in wild black currant berries from the Vilyuy group of districts was less: vitamin E – 68.53–76.46 mg/kg; C – 839.03–953.50 mg/100g; B1 – 2.43–2.63 mg/kg; B2 – 12.76–14.08 mg/kg; B6 – 16.73–18.68 mg/kg. Studies on the content of heavy metals in the soil and berries in the Central and Vilyuy zones of Yakutia. Proved that the amount of heavy metals contained in the soil, and their removal by black currant berries is different. There is no cadmium or mercury in wild currant berries. Zinc, iron, cobalt and iodine in the berries of currant are present within the permitted levels.

Effects of Soil Fertility Status and Its Management on Productivity of Rice in Flood Plains of Wukari, Taraba State, Nigeria

An experiment was carried out to determine the soil fertility status and productivity of rice on flood plain soils at different locations in Wukari LGA of Taraba State in the southern guinea Savanna zone of Nigeria. The treatments consisted of five locations (Gidan-Idi, Gindin-Dorowa, Tsokundi, Rafin-Kada and Nwuko) that was laid out in a Randomized Complete Block Design (RCBD) and replicated three times. The field was cleared, ploughed and harrowed, and marked into plots of 5 m x 5 m with an alley of 1 m between replications and 0.5 m between plots. Rice seeds (faro 44 (sipi 6920233)) were sown by dibbling at 25 cm×20 cm intra row. Nitrogen fertilizer was applied (at 3 to 4 weeks after planting as urea at the rate of 120 kgN ha-1) by top dressing method. Phosphorus fertilizer was also applied at 5 to 8 weeks after planting in split doses at the rate of 40 kg P2O5 ha-1 as single super phosphate and Potassium oxide fertilizer was applied 10 to 12 weeks after planting at 40 kg K2O ha-1 by top dressing method. Soil and plant data were collected and analyzed using standard procedures. The results were subjected to analysis of variance and means separated using F-LSD test. Significant (P≤0.05) differences in plant height and grain yield were observed during 2016 and 2017. Rafin-Kada recorded the highest grain yield of 8.36 tons/ha while Nwuko recorded lowest grain yield of 7.43 tons/ha in 2016. Gidan-Idi recorded the highest grain yield of 8.33 tons/ha while Gindin-Dorowa recorded lowest grain yield of 7.41 tons/ha in 2017.

Influence Of The Large Flood On The Element Composition Of Fluvisols In The Amur River Valley

Floodplain soils function as long-lasting stock or source of different substances, including pollutants. The main factor determining biochemical processes in fluvisols is flooding. Global climate change, which is causing more frequent and massive floods, is urging us to assess the potential environmental risks and create appropriate environmental management strategies. This study was performed to estimate the impact of a heavy flood on the total content of major elements and both total and mobile trace elements in fluvisols of one of the longest rivers in the world, the Amur. The study was conducted in field conditions by sampling from the same soil profiles before and after the flood. As a result, 10 major and 42 trace elements were distinguished. Major-element composition was determined with X-ray fluorescent method, trace-element composition - with the inductive coupled plasma mass spectroscopy. Maximum decrease of concentration was determined for CaO, MnO, P2O5 (up to 60%) and Sr, Cd, Ba, Tl and Pb (up to 40%). Significant increase was in concentration of Ni, Cu, and Mo (up to 160%). Among mobile trace elements, increase was observed in concentration of Sc, Ni and Th (up to 400%). With the correlation analysis, it was also established that the main causes of changes in elemental composition of the soils were decrease of pH, development of redox environment and washing out of organic matter. The main factor determining the influence of the flood on fluvisols was floodplain relief, which affected the length of the inundation, flood water velocity and the way allochthonic matter retained.

Mercury methylation from mercury selenide particles in soils

Selenium-inhibited monomethylmercury (MeHg) production is an attractive strategy for mitigating the risks of MeHg exposure. However, it is poorly understood the methylation potential of mercury selenide (HgSe) particles during their aging in soils and sediments. Net MeHg production in three floodplain soils amended with different geochemical species of mercury selenides, i.e., dissolved inorganic mercury freshly mixed with selenite (Hg(II)+Se(IV)), HgSe nanoparticles (45.2 ± 0.5 nm) and microparticles (> 1 μm) is examined. Among mercury types, the methylation from nanoparticulate HgSe was similar to (0.05 – 0.5 % vs. 0.1 – 0.4 %, yellow brown soil) or 12.9 – 21.0 times lower (0.02 – 0.1 vs. 0.6 – 1.5 %, black soil) than that from Hg(II)+Se(IV); however, net MeHg production from HgSe nanoparticles (0.02 – 0.5 %) was 1.9 – 15.5 times greater than HgSe microparticles (< 0.05 %) in all soils. Furthermore, net MeHg production from nanoparticulate HgSe varied significantly among soil types, attributable to differences in soil organic matter contents (2.4–5.8%) and microbial methylator community among soils. These results address the importance of geochemical intermediates of mercury selenide precipitation reactions and soil properties in MeHg production, and develop Se-based remediation strategy to minimize negative effects of MeHg on environmental and human health.