Sediment Capping Research Articles

Sediment capping technology for eutrophication control and its potential for application in Indonesian lakes: a review

Eutrophication occurs when the lakes become enriched with nutrients. Some nitrogen and phosphorus fractions will settle in sediment, and others will be released back into the overlying water column. Excess nutrients in water bodies resulting in hypoxic to anoxic conditions that can cause a mass fish death. Hence, we need a sediment management strategy to minimize resuspension and transport of sediment back into the water column. Sediment capping is a containment technology to reduce the release of nutrients from sediment as a strategy for eutrophication control. This study aims to provide insight into sediment capping technology, including several considerations in capping design, as well as information on several active materials that have been applied as capping materials and their efficiencies. Capping materials such as calcite, zeolite, bentonite, activated carbon, sludge, biochar, and gypsum from previous studies showed the efficiency of 54–99 % nutrient reduction with capping duration of 10–300 days in some eutrophic lakes. Sediment capping technology has successfully promoted lake ecosystem restoration in other countries, and this technology has the potential to be applied in Indonesian eutrophic lakes as a strategy for eutrophication control and sustainable management of lake ecosystems by considering the selection of the most effective, efficient, easy, inexpensive, and eco-friendly capping materials.

Reversing the damage: ecological restoration of polluted water bodies affected by pollutants due to anthropogenic activities.

Aquatic ecosystems provide a large number of cultural, regulating, and supporting services to humans and play a pivotal role in sustaining freshwater-dependent ecosystems. However, an increase in human population coupled with economic growth in the last few decades has severely affected their functioning and ecological health. This has led to an increase in concentrations of pollutants originating from anthropogenic activities such as heavy metals, plastics, semi-volatile organic compounds, and endocrine disruptors. These pollutants provoke deleterious impacts on aquatic biodiversity and affect the water quality and functioning. In this paper, we discuss the sources and impacts of such pollutants as well as restoration techniques for reducing their impact on aquatic ecosystems. Several physical and chemical ecological restoration techniques, such as dredging, sediment capping, water diversion, adsorption, aeration, and flushing, can be employed to improve the water quality of water bodies. Additionally, biological techniques such as phytoremediation, phycoremediation, the use of biomembranes, and the construction of ecological floating beds can be employed to increase the population of aquatic organisms and improve the overall ecological health of aquatic ecosystems. Restoration techniques can effectively reduce the concentrations of suspended solids and dissolved phosphorus and increase the levels of dissolved oxygen. The restoration techniques for improving the ecological health of water bodies should not be limited to simply improving the water quality but should also focus on improving the biological processes and ecosystem functioning since it is essential to mitigate the adverse effects of pollutants and restore the vital ecosystem services provided by water bodies for future generations.

Inhibition of sediment erosion and phosphorus release by remediation strategy of contaminated sediment backfilling

The management of sediment-water interfaces, especially bed stability, is essential for controlling accumulated contaminants in the sediment. In this study, the relationship between sediment erosion and phosphorus (P) release under the remediation strategy of contaminated sediment backfilling (CSBT) was explored through a flume experiment, i.e. the dredged sediment was calcined into ceramsite after dewatering and detoxification and then backfilled to the dredged area for sediment capping, thus avoiding the introduction of foreign materials via in-situ remediation and the large-scale land occupation associated with ex-situ remediation. Acoustic Doppler velocimeter (ADV) and optical backscatter sensor (OBS) were used to measure the vertical distributions of flow velocity and sediment concentration in the overlying water, respectively, and diffusive gradients in thin films (DGT) was used to measure the P distribution in the sediment. The results revealed that improving bed stability from CSBT can considerably improve the robustness of sediment-water interface and reduce sediment erosion by more than 70%. The corresponding P release from the contaminated sediment could be inhibited with an inhibition efficiency as high as 80%. CSBT is a potent strategy for managing contaminated sediment. This study provides a theoretical reference for controlling sediment pollution, further supporting river and lake ecological management and environmental restoration.

Effect of landing disturbance caused by capping materials on the control efficiency of contaminated sediment capping

Effect of landing disturbance caused by capping materials on the control efficiency of contaminated sediment capping

Sediment metals adhering to biochar enhanced phosphorus adsorption in sediment capping

Abstract Metal ions in sediment are inherent Ca and Fe sources for biochar modification. In this work, the effect of Ca2+ and Fe2+ released from sediment on biochar for phosphorus adsorption was evaluated. Results showed that raw peanut shell biochar (PSB) was poor in phosphorus adsorption (0.48 mg/g); sediment-triggered biochar (S-PSB) exhibited a P adsorption capacity of 1.32 mg/g in capping reactor and maximum adsorption capacity of 10.72 mg/g in the Langmuir model. Sediment released Ca2+ of 2.2–4.1 mg/L and Fe2+/Fe3+ of 0.2–9.0 mg/L. The metals loaded onto the biochar surface in the forms of Ca-O and Fe-O, with Ca and Fe content of 1.47 and 0.29%, respectively. Sediment metals made point of zero charge (pHpzc) of biochar shifted from 5.39 to 6.46. The mechanisms of enhanced P adsorption by S-PSB were surface complexation of CaHPO4 followed by precipitation of Ca3(PO4)2 and Ca5(PO4)3(OH). Sediment metals induced the modification of biochar and improvement of P adsorption, which was feasible to overcome the shortcomings of biochar on phosphorus control in sediment capping.

Mechanisms and risks of joint control of nitrogen and phosphorus through sediment capping technology in a pilot-scale study.

Purpose Nitrogen (N) and phosphorus (P) are the key elements leading to eutrophication, and it is important to jointly control N and P release from sediments into the water column.MethodsDifferent mixed materials including P sorbent, natural organic carbon (C), and an oxidizing agent were applied in a 1-year pilot-scale experiment.ResultsThe addition of iron-rich (IR) clay and Phoslock agent promoted the formation of iron bound P (Fe(OOH)~P) and calcium bound P (CaCO3~P) in sediments, respectively. IR clay offered more advantages in immobilization of phosphorus as refractory P, and the Phoslock agent more effectively reduced the risk of P release into water, which was expressed as a low equilibrium P concentration (EPC0). Mixtures of sugarcane (SU) detritus and IR clay exhibited high carbohydrate (CHO) contents, which further fuelled both denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This indicated that the SU dosage should be controlled to avoid DNRA over denitrification. Attention should be given to the fact that SU introduction significantly promoted the generation of an anaerobic state, leading to the desorption and release of Fe(OOH)~P, which could be alleviated by using Oxone. Multienzyme activity analysis showed that P and N transformation shifted from P desorption to organic P hydrolysis and from ammonification to denitrification and DNRA, respectively.ConclusionWe recommend the use of P sorbent and organic C combined with oxidizing agents as effective mixed materials for sediment remediation, which could enhance P adsorption and provide electron donors for denitrification, while also avoiding the generation of anoxia.

An application of Bayesian Belief Networks to assess management scenarios for aquaculture in a complex tropical lake system in Indonesia.

A Bayesian Belief Network, validated using past observational data, is applied to conceptualize the ecological response of Lake Maninjau, a tropical lake ecosystem in Indonesia, to tilapia cage farms operating on the lake and to quantify its impacts to assist decision making. The model captures ecosystem services trade-offs between cage farming and native fish loss. It is used to appraise options for lake management related to the minimization of the impacts of the cage farms. The constructed model overcomes difficulties with limited data availability to illustrate the complex physical and biogeochemical interactions contributing to triggering mass fish kills due to upwelling and the loss in the production of native fish related to the operation of cage farming. The model highlights existing information gaps in the research related to the management of the farms in the study area, which is applicable to other tropical lakes in general. Model results suggest that internal phosphorous loading (IPL) should be recognized as one of the primary targets of the deep eutrophic tropical lake restoration efforts. Theoretical and practical contributions of the model and model expansions are discussed. Short- and longer-term actions to contribute to a more sustainable management are recommended and include epilimnion aeration and sediment capping.

The efficacy of Phoslock® in reducing internal phosphate loading varies with bottom water oxygenation

Eutrophication in lakes and reservoirs has prompted interest in using sediment capping technology to reduce the sediment contribution to internal nutrient loading. One such sediment capping technology is Phoslock®, a lanthanum-embedded clay, which can bind phosphate at the sediment surface and limit its diffusion into the water column. However, in well-oxygenated lakes, naturally occurring iron can bind phosphate by a similar mechanism. We sought to test the efficacy of Phoslock® in limiting phosphate (PO43−) fluxes relative to untreated iron-rich lake sediment under conditions of bottom-water oxia and anoxia through laboratory batch core incubations of intact sediment cores from Jordan Lake, a reservoir in central North Carolina. We found that Phoslock® decreased phosphate fluxes relative to the control under anoxic conditions (7.5 ± 9.5 vs. 236 ± 74 µmol PO43−•m−2•d−1), but provided no benefit relative to the control when the water column was oxygenated (4.5 ± 4.3 vs. 7.0 ± 11.4 µmol PO43−•m−2•d−1). We also found that Phoslock® itself can act as a source of NH4+ to Jordan Lake waters. Applied at recommended levels to the whole lake, Phoslock® addition would result in a pulse increase in water column NH4+ concentrations of approximately 2.6 ± 0.8 μM (an increase of 10 to 275% compared to ambient).

Contaminated aquatic sediments.

The remediation of contaminated aquatic sediments requires a range of expertise from assessment (investigation, risk evaluations, modeling, and remedy selection) to design and construction. Research in 2019 has added to knowledge on optimizing the use of passive samplers for assessing chemical concentrations in sediment porewater. The porewater and black carbon appear to be better predictors of contaminant bioaccumulation than total organic carbon alone. This has led to better characterization of potential risk at sediment sites. Tools to identify and model sources of chemicals have been developed and used particularly for some metals, polynuclear aromatic hydrocarbons and polychlorinated biphenyls. There is great emphasis on beneficially using dredged sediment, treating it as a resource rather than a waste. Amendments used in sediment caps continue to be refined including the use of activated carbon within the caps and by itself. A technique involving 16S rRNA has been established as a means of identifying microbiological composition that naturally degrade contaminants. © 2020 Water Environment Federation PRACTITIONER POINTS: Sediment capping technology continues to advance Sampling and testing methods continue to be refined Natural processes such as biodegradation are being better understood Beneficial use of dredged sediment continue to be emphasized.

Interception of phosphorus release from sediments using Mg/Fe-based layered double hydroxide (MF-LDH) and MF-LDH coated magnetite as geo-engineering tools

A magnesium/iron-based layered double hydroxide (MF-LDH) and a composite of MF-LDH and magnetite (MF-LDH@Fe3O4) were synthesized, characterized and used as solid-phase phosphorus (P)-sorbents (SPPSs) to control the release of sedimentary P. The behavior and mechanism of phosphate adsorption onto MF-LDH and MF-LDH@Fe3O4 were studied. The effect of MF-LDH capping and amendment on the migration of P in sediments were comparatively investigated, and the impact of fabric-wrapped and unwrapped MF-LDH@Fe3O4 capping on P mobilization in sediments were also comparatively investigated. Results showed that both MF-LDH and MF-LDH@Fe3O4 had good phosphate adsorption performance, and the adsorption mechanisms included cation exchange, electrostatic attraction, ligand exchange and inner-sphere complex formation. Sediment capping and amendment using MF-LDH both could dramatically reduce the risk of the release of soluble reactive P (SRP) and diffusive gradient in thin-films-labile P (P-DGT) from sediments into overlying waters (OLY-Ws), and the MF-LDH capping had a better suppressing efficiency of sediment-P release into OLY-W than the MF-LDH amendment. Sediment capping with the fabric-wrapped and unwrapped MF-LDH@Fe3O4 both greatly decreased the risk of SRP and P-DGT released from sediment into OLY-W, and the efficiency of the prevention of SRP released from sediment into OLY-W by the fabric-wrapped MF-LDH@Fe3O4 capping layer (about 81–90%) was slightly lower than that by the unwrapped MF-LDH@Fe3O4 capping layer (about 94–99%). The reduction of P-DGT in the top sediment and the direct interception of the soluble P from pore water (POR-W) to OLY-W by the MF-LDH@Fe3O4 capping layer were the keys to the management of P released from sediment by the MF-LDH@Fe3O4 capping. From the standpoint of the efficiency of sedimentary P suppression, the convenience of application and the sustainability of sediment remediation, sediment capping with the fabric-wrapped MF-LDH@Fe3O4 is a promising approach to manage the release of sedimentary P into OLY-W.

Utilization of zirconium-modified granular zeolite as capping and mixing materials to suppress phosphorus release from sediment in landscape water body

A zirconium-modified granular zeolite (ZMGZ) was created and investigated for the suppression of the internal P loading in shallow landscape water bodies in this study. Results showed that the as-synthesized ZMGZ possessed high phosphate sorption capacity with a Langmuir maximum monolayer uptake capacity of 6.87 mg PO43−/g. Capping of landscape water body sediments with ZMGZ reduced the releasing rate of soluble reactive P (SRP) from the sediments into the overlying water, and it significantly reduced the SRP releasing rate under anoxic condition. Furthermore, the sediment capping decreased the pore water SRP concentration, and it was difficult for most of P trapped by the ZMGZ covering layer to be re-released into the water column. When the ZMGZ in the covering layer was mixed with the sediment, the ZMGZ became a sediment amendment. Mixing of landscape water body sediments with ZMGZ also resulted in the reduction of the SRP concentrations in the overlying and pore waters under the conditions of low and high dissolved oxygen, and it was also hard for most of P adsorbed by the added ZMGZ to be released back into the water column. Additionally, the addition of sediments with ZMGZ led to the decrease of the amounts of mobile and bioavailable P in the sediments. To sum up, we conclude that the capping/mixing combination method, which involves sediment capping with ZMGZ at first and then gradual mixing of ZMGZ with sediment via various natural disturbances (e.g., physical disturbance and bioturbation), is a very promising strategy for inhibiting the release of SRP from shallow landscape water body sediments into the overlying water.

Phosphorus and Cyanobacteria Precipitation and Sediment Capping in Lake Water Using Alum and Natural Minerals

AbstractThe objective of this study was to evaluate the use of natural minerals to enhance the precipitation of phosphorus and cyanobacteria during alum coagulation, and to reduce phosphate release...

Synergy of Algal Sedimentation and Sediment Capping for Methane Emission Control in Bloom Waters

This study tested a strategy in simulated column systems to control methane emissions from algal bloom waters using the combined technology of algae sedimentation and sediment capping. The results demonstrated that the synergy of algal sedimentation and sediment capping can effectively improve the water environment and reduce methane emissions; however, the improvement rate differed among capping materials. The use of activated carbon yielded better performance on the water environment improvement and methane emission control than soil and zeolite. Compared with the control system, the dissolved oxygen and redox potential in the water were increased from<2.5 mg·L-1 to 3.1 mg·L-1 and from<100 mV to 174 mV, respectively. In addition, the redox potential in the surface sediment was reversed from -125 mV to 168 mV after algal sedimentation with subsequent activated carbon capping. As a result, methane emissions in the algal sedimentation-activated carbon capping systems were decreased by 90.2% over the incubation period relative to the control system. This study provides useful insights into methane emission control in eutrophic waters.

Simultaneous control of nitrogen and phosphorus release from sediments using iron-modified zeolite as capping and amendment materials

The use of zeolite as a geo-engineering tool has a high potential to control nitrogen (N) release from sediments, but its efficiency for controlling sedimentary phosphorus (P) release still need to be further increased. To address this issue, this work synthesized an iron-modified zeolite (IM-Z) by coating iron onto the surface of natural zeolite (NAT-Z) and then the as-obtained IM-Z was utilized as a geo-engineering material to block the upward mobilization of N and P from sediments to the overlying water. The efficiencies of IM-Z covering and amendment to prevent the liberation of N and P from sediments were evaluated, and the controlling mechanism was explored. Capping and amendment with IM-Z not only resulted in the tremendous reduction of the levels of ammonium-N (NH4+-N) and reactive soluble P (RSP) in the overlying water, but also led to the decrease of the contents of NH4+-N and RSP in the pore water. More importantly, sediment capping and amendment with IM-Z resulted in the formation of a static layer in the upper sediment directly below the sediment-water interface, with very low concentration of RSP in the pore water. In addition, IM-Z capping and addition effectively immobilized the diffusive gradients in thin films (DGT)-labile P in the overlying water and sediment. Furthermore, the decrease of the DGT-labile Fe concentrations in the overlying water as well as the top sediment were also observed after IM-Z capping and addition. Nearly 70% of P bound by IM-Z is stable and difficult to be released back into the overlying water under common pH and anoxic conditions. The adsorption of pore water NH4+-N on IM-Z, the immobilization of pore water RSP and DGT-labile P by IM-Z and the uptake of DGT-labile Fe on IM-Z played a significant role in the simultaneous control of NH4+-N and RSP liberation. Compared to NAT-Z, the efficiency of IM-Z to block the liberation of sedimentary P was higher. Results of this study demonstrate that IM-Z is suitable for use in the simultaneous interception of the upward transportation of NH4+-N and RSP from sediments into the overlying water.

Magnetite-modified activated carbon based capping and mixing technology for sedimentary phosphorus release control

In this study, magnetite-modified activated carbon (MAC) was synthesized, characterized and used as capping and amendment materials to control sedimentary phosphorus (P) release. Batch experiments were applied to determine the behavior of phosphate adsorption and desorption on/from MAC. Sediment incubation experiments were utilized to evaluate the impact of MAC capping and addition on the mobilization of P in sediments. Sediment capping and amendment with MAC both can greatly reduce the amount of reactive soluble P (RS-P) in the overlying water (OLY-water), with a reduction efficiency of higher than 83%. MAC capping and amendment both can significantly reduce the concentrations of labile P measured by diffusive gradient in thin-films (DGT) in the upper sediment, which gives rise to in the formation of the static layer of P (P–S-Layer) in the upper sediment. The forms of P bound by MAC were mainly redox-sensitive P (PRS), NaOH extractable inorganic P (IPNaOH) and HCl extractable P (PHCl), which accounted for 47.2, 18.5 and 32.9% of the total adsorbed P, respectively. Almost half of P adsorbed by MAC existed in the form of PRS, which is easy to be released under anoxic condition, and the retrieval of MAC from the waterbody after its application is very necessary. The concentrations of RS-P in OLY-water and mean DGT-labile P in P–S-Layer under capping condition were much less than those under amendment condition. The reduction of the apparent diffusion efflux of P across the interface between OLY-water and sediment by the MAC capping was much larger than that by the MAC amendment. Results of this work suggest that MAC capping and amendment are very promising methods for blocking the liberation of P from sediments into OLY-water, and MAC capping can achieve a higher efficiency of sedimentary P release control compared to MAC amendment.

Enhancement of active thin-layer capping with natural zeolite to simultaneously inhibit nutrient and heavy metal release from sediments

This study strove to enhance the efficiency of sediment capping using active thin-layer capping (ATC) with natural zeolite to simultaneously prevent the release of nutrients (PO43- and NH4+) and heavy metals (Pb2+, Cd2+, Mn2+, and Zn2+) from polluted reservoir sediment. A series of lab-scale column experiments were performed in different conditions by varying capping thickness, ionic strength of Na+ and Ca2+, and the redox environment in overlying water. Results showed that the release of nutrients and heavy metals could be prevented effectively using ATC with zeolite. There was no significant difference in the efficiency of nutrient (except PO43-) and heavy metals inhibition among three capping thicknesses. The greatest efficiency was obtained with 2 cm thickness, which the inhibition rates of NH4+, PO43-, Cd2+, Pb2+, Mn2+, and Zn2+ were 91.9%, 57.7%, 35.7%, 85.7%, 65.6%, and 57.8%, respectively. And, the capping thickness of 1 cm was sufficient to simultaneously prevent the release of nutrients and heavy metals from sediment. The presence of high Ca2+ concentration in the overlying water promoted the release of nutrients and heavy metals. However, aerobic environment could enhance the efficiency of inhibition of nutrient and heavy metal (except Cd2+) release from sediment. Additionally, fluxes of NH4+, PO43-, and Pb2+ in aerobic conditions with capping were significantly lower than those in anaerobic conditions without capping in an in situ capping simulated experiment. Therefore, the efficiency of inhibiting the release of nutrients and heavy metals from sediments could be enhanced by ATC with natural zeolite through a series of measures, including increasing suitable capping thickness, creating an aerobic environment, and reducing the content of Ca2+ in overlying water.

Fluxes of nutrients and trace metals across the sediment-water interface controlled by sediment-capping agents: bentonite and sand.

The effect of bentonite and sand, as natural capping agents, on the fluxes of nutrients and trace metals across the sediment-water interface was studied through sediment incubation, and the ecotoxicological impact was assessed by using Daphnia magna. Bentonite and sand were layered on the sediment at 15, 75, and 225mgcm(-2), and the concentration of cations, nutrients, and trace metals was measured. Sediment incubation showed that bentonite reduced the N flux but increased the P flux as a result of dissolution of non-crystalline P from bentonite, while sand slightly decreased the N fluxes but not the P flux. The concentration of Na increased in the overlying water with increasing application rates of bentonite, while that of Ca decreased. However, regardless of the rate of sand application, concentrations of all cation species remained unchanged. The concentration of As and Cr increased with bentonite application rate but decreased with sand. Both capping materials suppressed fluxes of Cd, Cu, Ni, and Zn compared to control, and the extent of suppression was different depending on the trace metal species and capping agents used. During sediment incubation, the survival rate of D. magna significantly decreased in bentonite suspension but began to decrease at the end in sand suspension. Sediment capping of mildly polluted sediments by using bentonite and sand lowered the level of nutrients and trace metals. However, unexpected or undesirable side effects, such as influxes of P and As from bentonite to the overlying water and a possibility of toxic impacts to aquatic ecosystems, were observed, suggesting that capping agents with an adequate assessment of their side effects and toxicity should be predetermined for site-specific sediment management strategies.

Improvement of water quality by sediment capping and re-vegetation with Vallisneria natans L.: A short-term investigation using an in situ enclosure experiment in Lake Erhai, China

This study evaluated the effects of sediment capping with local unpolluted soil and re-vegetation with Vallisneria natans on the water quality in a two-month in situ experiment in a mesotrophic lake. Water quality was improved substantially by sediment capping whether alone or along with re-vegetating using V. natans, although varied greatly with time. Sediment capping was an effective technique to reduce nitrogen (N) and phosphorus (P) release from fertile sediment, which thus inhibited phytoplankton growth in the water column. Re-vegetation using V. natans helped to improve water quality slightly more. Sediment capping alone or along with re-vegetating also changed interactions of the water quality parameters substantially. Compared to the control, sediment capping alone enforced the relationships between Chl-a and both SD and K, but along with re-vegetation weakened the relationships. In addition, sediment capping alone enforced the relationship between Chl-a and N-NH4, but with or without along with the re-vegetation the relationships between Chl-a and both TN and N-NO3 decreased.

Stability of Capped Dredged Sediments in a Confined Disposal Facility at Malmøykalven, Oslofjord, SE Norway

Conventional sediment capping is a widely used technique where clean sediments are placed over contaminated sediments to reduce the migration of contaminants to the environment. A concern of the method is initial contaminant transport through the cap during the consolidation of the underlying disposed sediments. The current study was conducted to investigate the efficiency of the cap placed over the Malmøykalven confined disposal facility (CDF). The thickness of the soft disposed sediments reached 6 m in maximum, and was subject to extensive consolidation when the cap was placed. Vertical profiles of trace metals (Cd, Cu, Hg, Pb, Zn) and the structure of the cap layer were studied in six gravity cores. The cap material was clearly distinguishable in the sediment cores, both visually and chemically. The results provided evidence that consolidation-induced pore water advection was able to transport fine particles (<63 µm) and organic material into the cap layer. Metal transport in the particulate phase was suggested to be the main transport process into the cap layer. The study shows the importance of an appropriate cap layer design to prevent any particle transport and to minimize the effects of consolidation-induced advective transport.

Sand Cap Placement and Cap Thickness Monitoring: A Case Study at a Confined Disposal Facility

Thin sediment capping is a commonly used technique to prevent mobilization of contaminants from sediments into the environment. A 70‐m‐deep subaqueous confined disposal facility (CDF, 350,000 m2) at Malmøykalven, Oslofjord, which received dredged contaminated sediments from Oslo Harbor, was capped with 148,900 m3 of sand in 2009. This research serves as a case study regarding some of the key considerations involved with the cap placement and monitoring of the cap layer. Uncertainty is included in all the cap thickness monitoring methods and a combined use of them provided a better understanding of the cap coverage and structure at the site. An open water disposal model (STFATE) was used to simulate the behavior of the barge‐released cap material. The modeling results were consistent with field observations regarding the material spread, and the results provided insight into the relatively high material losses calculated. Better knowledge obtained of material settling resulted in cap properties and cap monitoring methods that are useful when planning similar operations. ©2015 Wiley Periodicals, Inc.