Linkages between unpaved forest roads and streambed sediment: why context matters in directing road restoration

Unpaved forest roads remain a pervasive disturbance on public lands and mitigating sediment from road networks remains a priority for management agencies. Restoring roaded landscapes is becoming increasingly important for many native coldwater fishes that disproportionately rely on public lands for persistence. However, effectively targeting restoration opportunities requires a comprehensive understanding of the effects of roads across different ecosystems. Here, we combine a review and a field study to evaluate the status of knowledge supporting the conceptual framework linking unpaved forest roads with streambed sediment. Through our review, we specifically focused on those studies linking measures of the density of forest roads or sediment delivery with empirical streambed sediment measures. Our field study provides an example of a targeted effort of linking spatially explicit estimates of sediment production with measures of streambed sediment. Surprisingly, our review uncovered few studies (n = 8) that empirically tested the conceptual framework linking unpaved forest roads and streambed sediment, and the results varied considerably. Field results generally supported the conceptual model that unpaved forest roads can control streambed sediment quality, but demonstrated high‐spatial variability in the effects of forest roads on streambed sediment and the need to address hotspots of sediment sources. The importance of context in the effects of forest roads is apparent in both our review and field data, suggesting the need for in situ studies to avoid misdirected restoration actions.     

Faunal response to benthic and hyporheic sedimentation varies with direction of vertical hydrological exchange

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Membrane‐Based Approach for the Downstream Processing of Influenza Virus‐Like Particles

Currently, marketed influenza vaccines are only efficient against homologous viruses, thus requiring a seasonal update based on circulating subtypes. This constant reformulation adds several challenges to manufacturing, particularly in purification due to the variation of the physicochemical properties of the vaccine product. A universal platform approach capable of handling such variation is therefore of utmost importance. In this work, a filtration‐based approach is explored to purify influenza virus‐like particles. Switching from adsorptive separation to size‐based purification allows overcoming the differences in retention observed for different influenza strains. The proposed process employs a cascade of ultrafiltration and diafiltration steps, followed by a sterile filtration step. Different process parameters are assessed in terms of product recovery and impurities’ removal. Membrane chemistry, pore size, operation modes, critical flux, transmembrane pressure, and permeate control strategies are evaluated. After membrane selection and parameter optimization, concentration factors and diafiltration volumes are also defined. By optimizing the filtration mode of operation, it is possible to achieve product recoveries of approximately 80%. Overall, the process time is decreased by 30%, its scalability is improved, and the costs are reduced due to the removal of chromatography and associated buffer consumptions, cleaning, and its validation steps.     

Pesticides and heavy metals in Danish streambed sediment

The role of streambed sediment as a sink for pesticides and heavy metals was investigated in 30 Danish lowland streams. The investigated streams drain catchments varying in hydrology, topography, soil type and land use. The <250 m newly accumulated fraction of the uppermost 1–2 cm layer of streambed sediment was analysed for 19 old and modern pesticides and 9 heavy metals. DDE was present in the sediment of all the streams. Of the herbicides, fungicides and insecticides currently in use, the most frequently detected was diuron (50.0%), fenpropimorph (66.7%) and lambda-cyhalothrin (6.7%), respectively. The pesticides detected in the highest concentration were fenpropimorph (1700 ng g^–1), propiconazole (130 ng g^–1) and isoproturon (110 ng g^–1). The heavy metals are listed in order of increasing median concentration: Cd (0.80 g g^–1), Co (9.1 g g^–1), As (12.0 g g^–1), Ni (19.0 g g^–1), Cr (19.2 g g^–1), Pb (19.7 g g^–1), Cu (20.1 g g^–1), V (28.5 g g^–1), Zn (103 g g^–1). The average number of pesticides detected in the 27 streams draining predominantly agricultural catchments was (3.7±2.0) being higher (p=0.077) than in the three streams draining non-agricultural catchments (1.7±0.6). Pesticides were significantly related to catchment size, soil type and hydrological regime. Several heavy metals (Cr, Cu, Pb, V and Zn) were related to urban activity and soil type.     

猪圆环病毒2型病毒样颗粒的高效组装技术研究*

目的:探索猪圆环病毒2型(PCV2)病毒样颗粒(VLPs)的高效组装技术,提高VLPs的稳定性。方法:利用大肠杆菌表达PCV2 Cap蛋白自组装为VLPs,分析不同离子强度下VLPs的稳定性。利用切向流技术添加尿素,降低pH,可使VLPs解组装,利用硫酸铵分级沉淀、阴离子交换层析纯化获得Cap蛋白,去除尿素,提高离子强度和pH,实现VLPs的高效再组装。结果:PCV2 Cap蛋白自组装VLPs在150mmol/L NaCl下稳定性较差,而在500mmol/L NaCl下可提高VLPs的稳定性,但仍较易发生聚集,核酸含量均较高。在150mmol/L NaCl、300mmol/L尿素和pH 5.5的缓冲体系条件下,能够使VLPs解组装。经25%~50%饱和硫酸铵(V/V)分级沉淀粗纯,阴离子交换层析500mmol/L NaCl下洗脱获得精纯Cap蛋白,蛋白质纯度≥95%,并能够有效去除核酸。通过切向流技术去除体系中的尿素,并将NaCl浓度提高至1mol/L、pH提高至8.0,改变蛋白质表面静电荷分布,实现VLPs的高效、均一再组装,组装效率≥99%,回收率为65.85%,并明显提高VLPs的稳定性,能够稳定保存6个月以上。结论:利用硫酸铵分级沉淀、阴离子交换层析纯化获得Cap蛋白,去除尿素,提高离子强度和pH,实现VLPs的高效再组装。     

The Effect of Outflow Depth on Phosphorus Retention in a Small,Hypertrophic Temperate Reservoirwith Short Hydraulic Residence Time

Stratification and phosphorus fluxes (input, output, sedimentation, and release from sediments) were studied in České údolí Reservoir (49°43′N, 13°21′E; V – 2.65 × 10⁶ m³; A – 1.04 × 10⁶ m²; z_max – 5.5 m; surface altitude – 314 m a.s.l.) during two summer stratification periods which differed in outlet operation and in hydraulic residence time (1997: surface outlets and 14 days; 1998: bottom outlets and 23 days). Use of bottom outlets resulted in weaker thermal stratification, a less pronounced oxygen deficit in the hypolimnion, and significantly lower P retention (17%) in comparison with surface discharge (42%). Factors apparently contributing to lower retention of P during the use of bottom outlets were: (i) faster flushing of the hypolimnion which intensified longitudinal transport of particles, (ii) more intense P release from sediments due to a lower concentration of nitrate in the water column and to more frequent contact of sediments in the shallows with water of pH >9. During both periods, phytoplankton production was limited only by light, not by nutrients. Phytoplankton biomass was comparable in both years despite some differences in vertical distribution.     

Transport of Algal Cells in Hyporheic Sediments of the River Elbe (Germany)

The advective transport of algal cells into the interstices of the hyporheic zone of the River Elbe was spatially and temporally heterogenous. Even deep sediment layers were reached by large phytoplankton species. Therefore, it is suggested that (i) the advective interstitial transport patterns vary between different algal sizes and morphotypes and (ii) sediment characteristics, expressed by the permeability coefficient k_f of porous media, affect retention and retardation of surface water algae during subsurface transport. The transport behaviour of different green algae (Chlorella sp., Scenedesmus acuminatus, Desmodesmus communis, and Pediastrum duplex) and algal sized microspheres was tested in flow‐through column experiments with hyporheic sediments. The algal cell transport was directly related to the permeability of the column sediments. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

From Demographic Strategies to Mathematical Models: Trends in Population Dynamics Studies of Aquatic Oligochaeta

The existence of a negative relationship between fine sediment infiltration during the incubation period and salmonid embryo survival has often been discussed in the literature. However, few studies have specifically addressed this relationship in the field. We conducted a field experiment to examine the relationship between survival of Atlantic salmon (Salmo salar) embryos contained in incubation baskets and the patterns of fine sediment infiltration into the baskets during the incubation period. The results indicate that survival to pre-eyed (STPE), eyed (STE) and hatched (STH) stages of development were all negatively correlated with the percentage of fine sediment entering the baskets. STPE and STE were most strongly affected by silts and clays (<0.063 mm) although this size class represented only a small fraction of the grain size distribution inside the incubation baskets (0.03–0.41%). STH was most strongly correlated with the infiltration of medium sand (0.25–0.50 mm) material. On average, 66% of the implanted embryos survived to the pre-eyed stage of development compared to 63% for the eyed and 48% for the hatched stages of development.     

Filtration and ingestion rates of Salpa fusiformis Cuvier (Tunicata : Thaliacea): Effects of size,individual weight and algal concentration

Filtration and ingestion rates of Salpa fusiformis Cuvier were determined while fed Phaeodactylumtricomutum Bohlin at concentrations of 2?64 × 10³ cells·ml^?1. Filtration and ingestion rates increase exponentially with increasing length and body protein. The relations between protein content and body length, and between filtration rate and weight are similar for blastozooids and oozooids. A capture efficiency of the order of 6–32% is calculated: Salpa fusiformis seems to have a low retention efficiency, but its very high filtration rate gives it pride of place amongst filter-feeders. Specific filtration rates are independent of weight; specific ingestion rates are independent of weight for blastozooids, but for oozooids they seem to diminish with increasing weight. The mean daily ration (μg C ingested · μg body C^?1) is 107% for a blastozooid and 117% for an oozooid. Specific filtration rates decrease exponentially as particle concentration rises, as for many other filter-feeders, and the specific ingestion rate follows an Ivlev relation.     

Robust scale-up of dead end filtration: impact of filter fouling mechanisms and flow distribution

Robust design of a dead end filtration step and the resulting performance at manufacturing scale relies on laboratory data collected with small filter units. During process development it is important to characterize and understand the filter fouling mechanisms of the process streams so that an accurate assessment can be made of the filter area required at manufacturing scale. Successful scale-up also requires integration of the lab-scale filtration data with an understanding of flow characteristics in the full-scale filtration equipment. A case study is presented on the development and scale-up of a depth filtration step used in a 2nd generation polysaccharide vaccine manufacturing process. The effect of operating parameters on filter performance was experimentally characterized for a diverse set of process streams. Filter capacity was significantly reduced when operating at low fluxes, caused by both low filtration pressure and high stream viscosity. The effect of flux on filter capacity could be explained for a variety of diverse streams by a single mechanistic model of filter fouling. To complement the laboratory filtration data, the fluid flow and distribution characteristics in manufacturing-scale filtration equipment were carefully evaluated. This analysis identified the need for additional scale-up factors to account for non-uniform filter area usage in large-scale filter housings. This understanding proved critical to the final equipment design and depth filtration step definition, resulting in robust process performance at manufacturing scale.     

Depth perception in disparity-defined objects: finding the balance between averaging and segregation

Deciding what constitutes an object, and what background, is an essential task for the visual system. This presents a conundrum: averaging over the visual scene is required to obtain a precise signal for object segregation, but segregation is required to define the region over which averaging should take place. Depth, obtained via binocular disparity (the differences between two eyes’ views), could help with segregation by enabling identification of object and background via differences in depth. Here, we explore depth perception in disparity-defined objects. We show that a simple object segregation rule, followed by averaging over that segregated area, can account for depth estimation errors. To do this, we compared objects with smoothly varying depth edges to those with sharp depth edges, and found that perceived peak depth was reduced for the former. A computational model used a rule based on object shape to segregate and average over a central portion of the object, and was able to emulate the reduction in perceived depth. We also demonstrated that the segregated area is not predefined but is dependent on the object shape. We discuss how this segregation strategy could be employed by animals seeking to deter binocular predators.This article is part of the themed issue ‘Vision in our three-dimensional world’.     

The effects of increased flow and fine sediment on hyporheic invertebrates and nutrients in stream mesocosms

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Isolation of Plant Gene Space-Related Sequence Elements by High C+G Patch (HCGP) Filtration: Model Study on Rice

For the isolation of gene space representative sequence elements, a new methodology—high C+G patch (HCGP) filtration—has been developed using rice as a model. The method is based on the fragmentation of the genomic DNA by methylation-sensitive HpaII and MspI restriction endonucleases having exclusively G/C base pair-containing recognition sites. These enzymes fragment the genome at high C+G content and hypomethylated regions. Cloning fragments spanning such regions in close vicinity (200–2,000 bp) revealed that about 60% of the clones represented gene space sequences resulting in twofold enrichment of these sequences, which is close to the theoretical maximum in rice. The sequence information of clones used in the present study was deposited in the NCBI database under the accession numbers EI 365676–EI 366364.     

Effects of Planting Depth,Sediment Grain Size,and Nutrients on Ruppia maritima and Potamogeton perfoliatus Seedling Emergence and Growth

Protocols are now available for seed harvest, storage and germination of several mesohaline and polyhaline species; however, low seedling survival rates point to the need for an increased understanding of factors affecting seedling establishment. Depth of seed burial in sediments and initial seedling growth rates are shown to be limiting factors for photosynthetic competency of Ruppia maritima and Potamogeton perfoliatus. Seedling emergence is inversely proportional to planting depth on sediments ranging in grain size from coarse sands (850 μm) to silt (63 μm). Less than 6% of the seeds of either species emerged when buried to a depth of 3 cm in test sediments. Germination was greatest for seeds placed on the surface of sediments; however, these seedlings were subject to displacement because of the weak and fragile roots produced during early growth. Fine sediments may be more favorable for R. maritima seedling establishment, because seedling emergence and height decreased with increasing sediment grain size. Potamogeton perfoliatus seedlings seem to be more tolerant of a wider range of sediment grain sizes than R. maritima as indicated by the lack of an effect of sediment grain size on P. perfoliatus seed emergence, seedling height, and biomass. Increasing nutrients stimulated seedlings of both species; however, even at the highest concentrations tested, growth, as determined by shoot elongation and leaf and root formation, slowed within 7–10 days. This suggests factors other than mineral nutrients and light limit growth or that growth shifts from aboveground biomass production to belowground vegetative spread.     

Influence of streambed sediment clogging on microbial processes in the hyporheic zone

1. The hyporheic zone plays a key role in hydrological exchange and biogeochemical processes in streambed sediments. The clogging of sediments caused by the deposition of particles in the bed of streams and rivers can decrease sediment permeability and hence greatly affect hyporheic microbial processes. 2. The main objective of this study was to determine the influence of sediment clogging on hyporheic microbial processes in three French rivers (the Usses, Drôme and Isère). In each river, microbial abundance and activity were studied at three depths (10, 30 and 50 cm) in the sediment at one unclogged (high porosity) and one clogged site (low porosity). 3. The results showed that the sediment clogging had inconsistent effects on microbial processes in the three rivers. Increases (Usses) or decreases (Drôme and Isère) in both aerobic and anaerobic processes were detected at the clogged sites compared to unclogged sites. These results suggest that microbial changes because of the sediment clogging are mainly mediated by the residence time of water within the hyporheic sediments. 4. A single model predicting the effect of clogging on hyporheic microbial processes cannot be applied generally to all rivers because the degree of clogging creates heterogeneous effects on flow rates between surface and interstitial waters. As a consequence, the influence of heterogeneous clogging on surface water–hyporheic exchanges needs to be evaluated by water tracing and hydraulic modelling to determine the links between microbial processes and hydraulic heterogeneity induced by clogging in hyporheic sediments.     

Effects of Particle Size and Redox Potential on Arsenic Fractionation in Soils Irrigated with Arsenate-rich Water

Aging affects arsenic (As) bioaccessibility in soils. This study focuses on the influences of particle size and redox potential on As(V) aging in irrigated soils. The results showed that variation of As fractions in fine particles, except the loosely adsorbed fraction, was larger than that in coarse particles over time. Anoxic conditions decreased the change in As fractions, with the exception of the exchangeable fraction in soils over time, in comparison to the aerobic condition. The aging processes of As(V) in different particle sizes and soils at different redox potentials exhibited several stages. The only significant difference in the aging process of As(V) in different particle sizes was the longer transformation period of the water-soluble fraction into the Fe/Mn/Al oxides-bound fraction in fine particles than in coarse particles. The redox potential had a significant influence on the aging process of As(V) in soils after 10 days of incubation. In terms of As bioaccessibility, anoxic conditions shortened the aging process of As(V) in soils. During the aging process, fine particles and aerobic conditions intensified the decrease in As(V) bioaccessibility in soils in comparison to the coarse particles and anoxic condition.     

Vertical Profile of PAHs and Dredging Depth of River Sediments

Sediment dredging is an effective engineering measure to reduce the negative effects of PAHs pollution on water environment. The dredging depth is a key parameter in environmental dredging engineering. A guidance of environmental dredging depth needed to reduce the toxicity risk was developed which was specifically designed for the removal of river sediments contaminated by PAHs based on the mean effect range median quotients (mean-ERM-q). The dredging depths for removing river sediments were calculated based on the vertical profile of PAHs content and the quality guidelines of sediment. Pinghu water system was carried out to determine the dredging depths of sediments from nine rivers by the proposed method. Each sediment core was collected from different river. The results showed the profiles of PAHs in sediment cores were irregular and diverse due to river dredging events and human activities in different periods. The risk assessment of PAHs toxicity showed one of nine cores with moderate-high probability, 4 of nine cores with low-moderate probability and the others with low toxicity risk. The achievement can offer a reference to the dredging engineering in other similar river systems.     

应用TFF微孔过滤澄清白喉、破伤风毒素培养液及超滤浓缩的试验

用ＴＦＦ微孔过滤系统对白喉、破伤风毒素培养液分别进行了两次澄清过滤试验,澄清过滤后的毒素上清液立即用ＴＦＦ超滤系统浓缩至原培养液体积的１／１０－１／２０。白喉毒素总回收率分别为８６％、７６．６％,破伤风毒素总回收率为９４．１％、９２％。澄清过滤中白喉毒素平均Ｆ１ｕｘ分别为２３．４、１４．３Ｌ／ｍ２／ｈ,破伤风毒素平均Ｆｌｕｘ为２４及２２．９Ｌ／ｍ２／ｈ。结果表明破伤风两次试验有很好的一致性,白喉毒素回收率差别不甚明显,而两次试验Ｆｌｕｘ相差较大,ＴＦＦ微孔过滤系统用于澄清白喉培养液,滤膜使用后的清洗程序仍需改良,以提高膜滤过功能的恢复。     

Strong Interplay between Sodium and Oxygen in Kesterite Absorbers: Complex Formation,Incorporation, and Tailoring Depth Distributions

Sodium and oxygen are prevalent impurities in kesterite solar cells. Both elements are known to strongly impact performance of the kesterite devices and can be connected to efficiency improvements seen after heat treatments. The sodium distribution in the kesterite absorber is commonly reported, whereas the oxygen distribution has received less attention. Here, a direct relationship between sodium and oxygen in kesterite absorbers is established using secondary ion mass spectrometry and explained by defect analyses within the density functional theory. The calculations reveal a binding energy of 0.76 eV between the substitutional defects Na_Cu and O_S in the nearest neighbor configuration, indicating an abundance of Na? O complexes in kesterite absorbers at relevant temperatures. Oxygen incorporation is studied by introducing isotopic ¹⁸O at different stages of the Cu₂ZnSnS₄/Mo/soda‐lime glass baseline processing. It is observed that oxygen from the Mo back contact and contaminations during the sulfurization are primary contributors to the oxygen distribution. Indeed, unintentional oxygen incorporation leads to immobilization of sodium. This results in a strong correlation between sodium and oxygen, in excellent agreement with the theoretical calculations. Consequently, oxygen availability should be monitored to optimize postdeposition heat treatments to control impurities in kesterite absorbers and ultimately, the solar cell efficiency.