Cu phytoextraction and biomass utilization as essential trace element feed supplements for livestock.

Copper (Cu), as an essential element, is added to animal feed to stimulate growth and prevent disease. The forage crop alfalfa (Medicago sativa L.) produced during Cu phytoextraction may be considered a biofortified crop to substitute the Cu feed additives for livestock production, beneficially alleviating Cu contamination in soils and reducing its input into agriculture systems. To assess this, alfalfa was grown in three similar soils with different Cu levels, i.e., 11, 439 and 779 mg kg-1 for uncontaminated soil (A), moderately Cu-contaminated soil (B) and highly Cu-contaminated soil (C), respectively. EDDS (Ethylenediamine-N,N'-disuccinic acid) was applied to the soils seven days before the first cutting at four rates (0, 0.5, 2 and 5 mmol kg-1) to enhance bioavailable Cu uptake. Alfalfa grew well in soils A and B but not in the highly Cu-contaminated soil. After applying EDDS, a significant biomass reduction of the first cutting shoot was only observed with 5 mmol kg-1 EDDS in the highly Cu-contaminated soil, with a 45% (P < 0.05) decrease when compared to the control. Alfalfa grown in the three soils gradually wilted after the first cutting with 5 mmol kg-1 EDDS, and Cu concentrations in the first cutting shoot were augmented strongly, by 250% (P < 0.05), 3500% (P < 0.05) and 6700% (P < 0.05) compared to the controls, respectively. Cu concentrations in alfalfa shoots were found to be higher in this study than in some fodder plants and further augmented in soils with higher Cu levels and with EDDS application. These findings suggest that alfalfa grown on clean soils or soils with up to 450 mg Cu kg-1 (with appropriate EDDS dosages) has the potential to be considered as a partial Cu supplementation for livestock. This research laid the foundation for the integration between Cu-phytoextraction and Cu-biofortification for livestock.

The beneficial and hazardous effects of selenium on the health of the soil-plant-human system: An overview.

Selenium (Se), which can be both hazardous and beneficial to plants, animals and humans, plays a pivotal role in regulating soil-plant-human ecosystem functions. The biogeochemical behavior of Se and its environmental impact on the soil-plant-human system has received broad attention in the last decades. This review provides a comprehensive understanding of Se biogeochemistry in the soil-plant-human system. The speciation, transformation, bioavailability as well as the beneficial and hazardous effects of Se in the soil-plant-human system are summarized. Several important aspects in Se in the soil-plant-human system are detailed mentioned, including (1) strategies for biofortification in Se-deficient areas and phytoremediation of soil Se in seleniferous areas; (2) factors affecting Se uptake and transport by plants; (3) metabolic pathways of Se in the human body; (4) the interactions between Se and other trace elements in plant and animals, in particular, the detoxification of heavy metals by Se. Important research hotspots of Se biogeochemistry are outlined, including (1) the coupling of soil microbial activity and the Se biogeochemical cycle; (2) the molecular mechanism of Se metabolic in plants and animals; and (3) the application of Se isotopes as a biogeochemical tracer in research. This review provides up-to-date knowledge and guidelines on Se biogeochemistry research.

Zn phytoextraction and recycling of alfalfa biomass as potential Zn-biofortified feed crop.

Zn is an essential micronutrient for living organisms and, in that capacity, it is added to animal feed in intensive livestock production to promote growth and eliminate diseases. Alfalfa (Medicago sativa L.) may have the potential to compensate and substitute the need for chemical Zn additives in feeds as a Zn-biofortified feed crop when grown on Zn-enriched soils. Thus, this possibility was investigated with a greenhouse experiment using three soils with Zn concentrations (mg kg-1) of 189 (soil A), 265 (soil B) and 1496 (soil C). Ethylenediamine-N,N'-disuccinate acid (EDDS) and Nitrilotriacetic acid (NTA) at different rates (0 as control, 0.5, 2 and 5 mmol kg-1) were applied as soil additives to enhance the phytoextraction efficiency of alfalfa. The results showed that Zn was highly transferable in alfalfa tissues in the three soils even without additives. EDDS was more effective than NTA in enhancing Zn phytoextraction by alfalfa. The maximum Zn accumulation in the third cutting shoots was obtained with the EDDS concentration of 5 mmol kg-1 in soil A and of 2 mmol kg-1 in soil B, with a 462% and 162% increase compared with controls, respectively. However, the higher EDDS concentration resulted in a significant reduction in biomass production. In soil C, all EDDS concentrations resulted in similar Zn accumulations in the third shoot. To improve the phytoextraction efficacy of Zn while minimizing its phytotoxicity on alfalfa, the rate of 2 mmol kg-1 EDDS proved to be optimal for soil B, and 0.5 mmol kg-1 EDDS for soils A and C. Findings suggest that phytoextraction of Zn-enriched soil can be combined with Zn biofortification, thus allowing to recycle Zn into biomass that can, to an extent, substitute Zn feed additives. This study provided a primary data set for the combination of Zn-biofortification and Zn-phytoextraction.

Leaching behavior of Cd, Zn and nutrients (K, P, S) from a contaminated soil as affected by amendment with biochar.

In Campine region in Flanders (Belgium) there are contaminated sites with Cd and Zn due to atmospheric deposition from industry. Flanders is also known for its large surpluses of nitrogen and phosphorous coming from intense livestock production. To solve both issues, the potential of biochar to sorb metals and nutrients was investigated. Experiments were conducted to examine whether biochar could reduce the leaching of nutrients (K, P and S) and metals (Cd and Zn) into the soil solution. Most biochars caused an increase in pH of approximately 1 unit which is often the main driver of the metal immobilization. Nutrient concentrations in the leachate of soil amended with oak-based biochar were lower compared to the blank soil. For the other amendments, however, the results were higher due to the nutrients leached from the applied products. The result of this experiment emphasize the potential of biochar to immobilize nutrients and metals in soil water systems, thus keeping the nutrients longer available for the plant and reducing the metal toxicity. However, the amount of metals immobilized was lower than expected. Further research is required to determine whether biochar from livestock products could act as a slow release fertilizer.

Optimizing the configuration of integrated nutrient and energy recovery treatment trains: A new application of global sensitivity analysis to the generic nutrient recovery model (NRM) library.

This paper describes the use of global sensitivity analysis (GSA) for factor prioritization in nutrient recovery model (NRM) applications. The aim was to select the most important factors influencing important NRM model outputs such as biogas production, digestate composition and pH, ammonium sulfate recovery, struvite production, product purity, particle size and density, air and chemical requirements, scaling potential, among others. Factors considered for GSA involve: 1) input waste stream characteristics, 2) process operational factors, and 3) kinetic parameters incorporated in the NRMs. Linear regression analyses on Monte Carlo simulation outputs were performed, and the impact of the standardized regression coefficients on major performance indicators was evaluated. Finally, based on the results, the paper describes the original use of GSA to obtain insight in complex nutrient recovery systems and to propose an optimal nutrient and energy recovery treatment train configuration that maximizes resource recovery and minimizes energy and chemical requirements.

Nutrient recovery from digested waste: Towards a generic roadmap for setting up an optimal treatment train.

This paper aims to develop a generic roadmap for setting up strategies for nutrient recovery from digested waste (digestate). First, a guideline-based decision-tree is presented for setting up an optimal bio-based fertilization strategy as function of local agronomic and regulatory criteria. Next, guidelines and evaluation criteria are provided to determine the feasibility of bio-based fertilizer production as function of the input digestate characteristics. Finally, a conceptual decision making algorithm is developed aiming at the configuration and optimization of nutrient recovery treatment trains. Important input digestate characteristics to measure, and essential factors for monitoring and control are identified. As such, this paper provides a useful decision-support guide for wastewater and residuals processing utilities aiming to implement nutrient recovery strategies. This, in turn, may stimulate and hasten the global transition from wastewater treatment plants to water resource recovery facilities. On top of that, the proposed roadmap may help adjusting the choice of nutrient recovery strategies to local fertilizer markets, thereby speeding up the transition from a fossil-reserve based to a bio-based circular nutrient economy.

Arsenic, chromium, molybdenum, and selenium: Geochemical fractions and potential mobilization in riverine soil profiles originating from Germany and Egypt.

The fractionation and potential mobilization of As, Cr, Mo, and Se in four floodplain soil profiles collected along the Nile (Egypt) and Wupper (Germany) Rivers were assessed using the BCR sequential extraction procedure. The concentrations of total and the geochemical fractions (acid soluble (F1), reducible (F2), oxidizable (F3), and residual (F4) fraction) of the elements were determined. The Wupper soils had the highest total concentrations (mg kg-1) of As (378) and Cr (2,797) while the Nile soils contained the highest total Mo (12) and Se (42). The residual fraction of As, Cr, Mo, and Se was dominant in the Nile soils suggesting the geogenic source of the elements in these soils. The residual fraction of As and Mo and the oxidizable fraction of Cr and Se were dominant in the Wupper soils. Among the non-residual fractions (potential mobile fractions; PMF = ∑F1-F3), the oxidizable fraction was dominant for Cr, Mo, and Se in the Nile soils and for Mo in the Wupper soils, while the reducible fraction was dominant for As in both soils. The PMF of As, Cr, and Se was higher in the Wupper than in the Nile soils which might reflect the anthropogenic sources of these elements in the Wupper soils, while the opposite was the case for the PMF of Mo. The high PMF of Se (87%), Cr (87%), and As (21%) in the Wupper soils suggested that a release of these toxic elements may happen which increase the potential environmental risks in the anthropogenically polluted soils.

Bioaccessibility of selenium from cooked rice as determined in a simulator of the human intestinal tract (SHIME).

BACKGROUND: As an essential but also potentially toxic element, both overexposure and underexposure to selenium (Se) can significantly affect public health. Rice is a common source of Se, especially in Asia. Not all Se may be released from the rice and become available for absorption into the bloodstream upon digestion in the gastrointestinal tract. Therefore, the bioaccessibility of Se in cooked white (polished) rice was assessed in vitro using the static gastrointestinal simulator SHIME (Simulator of the Human Intestinal Microbial Ecosystem). RESULTS: The common cooking procedure in China prior to consumption [i.e. boiling at low rice:water ratios (1:3) until all of the water is absorbed into the rice] did not change total Se levels in the rice. Gastrointestinal digestion of the cooked rice matrix revealed a Se bioaccessibility of 67-76% of total Se. Subsequent microbial activity in the colon reduced the accessibility of Se in the cooked rice to 51-62%. CONCLUSION: Not all Se present in cooked white rice should be considered as being bioavailable in the small intestine. A minor part is transferred with the remaining food matrix to the colon, where it is available for the microbial metabolism. © 2017 Society of Chemical Industry.

Forest floor leachate fluxes under six different tree species on a metal contaminated site.

Trees play an important role in the biogeochemical cycling of metals, although the influence of different tree species on the mobilization of metals is not yet clear. This study examined effects of six tree species on fluxes of Cd, Zn, DOC, H(+) and base cations in forest floor leachates on a metal polluted site in Belgium. Forest floor leachates were sampled with zero-tension lysimeters in a 12-year-old post-agricultural forest on a sandy soil. The tree species included were silver birch (Betula pendula), oak (Quercus robur and Q. petraea), black locust (Robinia pseudoacacia), aspen (Populus tremula), Scots pine (Pinus sylvestris) and Douglas fir (Pseudotsuga menziesii). We show that total Cd fluxes in forest floor leachate under aspen were slightly higher than those in the other species' leachates, yet the relative differences between the species were considerably smaller when looking at dissolved Cd fluxes. The latter was probably caused by extremely low H(+) amounts leaching from aspen's forest floor. No tree species effect was found for Zn leachate fluxes. We expected higher metal leachate fluxes under aspen as its leaf litter was significantly contaminated with Cd and Zn. We propose that the low amounts of Cd and Zn leaching under aspen's forest floor were possibly caused by high activity of soil biota, for example burrowing earthworms. Furthermore, our results reveal that Scots pine and oak were characterized by high H(+) and DOC fluxes as well as low base cation fluxes in their forest floor leachates, implying that those species might enhance metal mobilization in the soil profile and thus bear a potential risk for belowground metal dispersion.

Identification of dredged sediment-derived soils in the alluvial plains of the Leie and the Upper and Sea Scheldt rivers (Belgium) based on physico-chemical soil properties.

An approach was developed to identify surface soils affected by historical dredged sediment disposal in the alluvial plains of the Upper Scheldt, the Sea Scheldt and the Leie river. Dredged sediment-derived soils were identified based on field observations, comparative granulometric analyses and chemical analyses. Criteria developed were based on a comparison between reference data from 102 aerobic soil samples of areas known to be affected by dredged sediment disposal and 104 samples from undisturbed alluvial soils along the studied rivers. A comparative grain size analysis with optical laser diffractometry between the A and C horizon proved useful for the identification of levelled-up sites. The chemical soil characteristics that were most useful in identifying dredged sediment-derived soils were CaCO3, sulfur (S), organic carbon (OC) and phosphorus (P) contents, electrical conductivity (EC), and the C/P and C/S ratios. Criteria for concluding the origin of an investigated soil were specific for the studied area, but the approach presented may provide useful guidelines for developing criteria valid for different regions.