Cattail Litter Research Articles

Temporal variations in dissolved organic matter properties in a eutrophic lake under water dilution and aquatic plant litter decomposition: A simulated microcosm study revealing the environmental and microbial driving factors

Dilution by importing external clean water and restoration of aquatic vegetation are widely applied strategies for improving water quality of eutrophic lakes, while the influence of dilution or aquatic plant litter decomposition on dissolved organic matter (DOM) properties, which is closely associated with the health of aquatic ecosystems, is rarely known. In this study, the temporal variations of DOM properties in the overlying water of a eutrophic lake (Yilong lake in Yunnan, southwest China) under water dilution and aquatic plant litter decomposition were comparatively investigated via a simulated microcosm study using in situ samples. The results showed that water dilution reduced DOM concentration and bioavailability in the overlying water in a short term (about 45 d), and increased DOM humification, but such effect diminished over time. DOM concentration increased substantially during aquatic plant litter decomposition, and reed litter released much more amounts of DOM than that of cattail litter, which dominated by protein-like substances and characterized by high bioavailability and low humification degree. Nutrient (available phosphorus (AP), NH4+-N and TN) contents in the sediment indirectly affected DOM properties by remarkably influencing microbial community compositions and enzyme activities. The strong correlations between the relative abundances of dominant genera Bacillus and Clostridium and concentrations of DOM components implied the important roles of these taxa in DOM transformations. Our findings highlighted the effects and potential mechanisms of dilution and aquatic plant litter decomposition on DOM properties in eutrophic water bodies, and the necessity of proper water diversion and plant litter harvest to reduce endogenous organic pollution in lakes.

Testing restoration methods for Lake Ontario wetlands at a wetland scale

Sedges and grasses have a competitive advantage over cattails at higher elevations in Great Lakes wetlands where periodic low lake levels result in soils too dry to support cattails. Regulation of Lake Ontario water levels eliminated low lake-level years, resulting in cattail invasion. At a wetland scale at two Lake Ontario sites, we tested restoration methods by dredging channels through cattails, using spoil materials to create mounds suitable for sedge/grass growth, seeding mounds, and controlling cattails (T. × glauca) using methods adapted from experimental studies. Soil moisture and subsidence of mound soils were monitored. Vegetation was sampled pre-restoration and in shoreline sedge/grass meadow, emergent, and mound zones for two years following implementation. Although spoil mounds decreased in elevation at both sites, soil moisture increased more at the site with greater subsidence. Mean percent cover and ramet counts of cattails were reduced in sedge/grass and emergent zones at both sites. Mounds with greater soil moisture held more cattails post-construction. Across years at both sites, Carex lacustris and Calamagrostis canadensis increased in the sedge/grass meadow zone with reduction in Typha; Calamagrostis increased on the mounds. Key factors affecting results were cattail litter and, on the mounds, a second year of seeding with in situ cold, moist stratification, as well as soil moisture related to subsidence. Recommendations for future restorations include conducting more detailed soil surveys to assess potential subsidence, dredging wider and deeper channels to provide spoil for higher mounds, actively controlling invasive species, and conducting additional years of post-restoration data collection.

Biochar based constructed wetland for secondary effluent treatment: Waste resource utilization

• The sustainable reuse of sludge and wetland macrophyte litter was realized. • SBC and CBC promoted nutrient removal and reduced N 2 O emissions fluxes in CWs. • Biochar-derived DOM can supplement carbon source for denitrification in CWs. • SBC significantly enhanced the key enzyme activities and ETSA in CWs. • Biochar enhanced the enrichment of nitrogen and phosphorus removing microorganisms. Constructed wetlands (CWs) are widely used to treat the effluent of wastewater treatment plants (WWTPs) due to their energy-saving and environmentally friendly advantages. Wetland macrophyte litter and sludge are wastes produced by CWs and WWTPs, respectively. However, there are few studies on the reuse of sludge and macrophyte litter as CW filling materials. In this study, sewage sludge and cattail litter were selected as raw materials to prepare biochar, which was used as CW filling materials to enhance the advanced treatment of secondary effluent. The results showed that the sludge biochar CWs (SBC-CWs) and the cattail biochar CWs (CBC-CWs) possessed better total nitrogen removal efficiency (91% and 81%, respectively) compared with the control (67%). Furthermore, SBC-CWs significantly improved total phosphorus removal efficiency by 20% than that of the control (p < 0.05), and reduced nitrous oxide emissions by 66% compared with the control (p < 0.05). The dissolved organic matter (DOM) released in the biochar was beneficial to replenish carbon sources and accommodate adaptive microorganisms. Electrochemical characterization and molecular methods revealed that the sludge biochar had stronger electron transfer capacity (ETC) than the cattail biochar, which could better promote the activities of key enzymes of the pollutant removal procedure. High-throughput sequencing showed that microorganisms such as Thaurea , Rhodocyclaceae , Hydrogenophaga and Fusibacter related to nitrogen removal were well enriched in the SBC-CWs and CBC-CWs. This research shows the potential for the simultaneous energy-saving advanced treatment of WWTP tailwater and waste resource recovery.

Se transformation and removal by a cattail litter treatment system inoculated with sulfur-based denitrification sludge: Role of the microbial community composition under various temperature and aeration conditions

With a narrow margin between deficiency and toxicity, rising levels of selenium (Se) are threatening aquatic ecosystems. To investigate the role of microorganisms in Se bioremediation, a cattail litter system inoculated with the sulfur-based denitrification sludge was conducted. The results show the litter, as a carrier and nutrient source for bacteria, efficiently removed Se by ~ 97.0% during a 12-d treatment with water circulating. As the major removal pathways, immobilization rates of selenite were ~ 2.9-fold higher than selenate, and the volatilization, contributing to ~ 87.7% of the total Se removal, was significantly correlated with temperature (positively) and oxidation-reduction potential (ORP; negatively). Using X-ray absorption spectroscopy to speciate litter-borne Se, more Se0 formed without aeration due to abundant Se-reducing bacteria, among which Azospira and Azospirillum were highly related to the removal of both Se oxyanions, while Desulfovibrio, Azoarcus, Sulfurospirillum, Thauera, Geobacter, Clostridium, and Pediococcus were the major contributors to selenate removal. Overall, our study suggests microbial Se metabolism in the litter system was significantly affected by temperature and ORP, which could be manipulated to enhance Se removal efficiency and the transformation of selenate/selenite into low toxic Se0 and volatile Se, reducing risks posed by the residual Se in the system.

Selenium removal by clam shells and gravels amended with cattail and reed litter

Increasing selenium (Se) levels in aquatic environments raise concerns all over the world. This study investigated effects of organic amendments (cattail and reed litter) and porous media (gravels and clam shells) on Se removal efficiency of horizontal subsurface flow constructed wetlands. Our results show clam shells reduced Se (by mass) up to 2.4-fold faster than gravels within 19 days. Using clam shells as the sole substrate, 96.3% removal efficiency was obtained for cattail litter as an amendment, compared to 88.7% for reed litter over 10 days, although the latter released carbon and nitrogen at least 1.4-fold faster than the former. Meanwhile, speciation analysis suggests Se0 (~75%) and organo-Se (~94%) dominated the biofilms on shells and plant litter, respectively, as substrates. Overall, this study suggests clam shells and cattail litter as an effective medium and carbon source, respectively, can enhance microbial Se removal without posing risks to wildlife health.

Enhancement of nitrogen removal via addition of cattail litter in surface flow constructed wetland

Abstract: Decomposition of aquatic plant litters is an important process in ecological system, which will significantly affect the water environment and internal organisms. In this study, cattail litter was added into surface flow constructed wetland (SFCW) system to utilize as the additional carbon source for denitrification process. The adding method for the litter was determined by evaluating the influence of different adding methods on the water environment (pH, dissolved oxygen) and the litter utilization efficiency. Then, the change of effluent organic concentration (total organic carbon, TOC) and nitrogen removal efficiency of the system was investigated after the litter addition, meanwhile, the microbial community change was analyzed by high-throughput sequencing. The results showed that cattail litter should be added in batches to the SFCW system with the dosage of 0.1 g L−1 d−1, and the TN removal and loading of the system were significantly increased without obvious increase of the effluent TOC. After the litter addition, summer had higher increasing level of the denitrification efficiency of the system, which was lower in winter. This study could provide suitable method for cycling utilization of aquatic plant litters, and improve the denitrification effect of SFCW system.

Biogeochemical Controls on Strontium Fate at the Sediment-Water Interface of Two Groundwater-Fed Wetlands with Contrasting Hydrologic Regimes.

Radioactive strontium (Sr) is a common groundwater contaminant at many nuclear sites. Its natural retention in groundwater-fed wetlands is an attractive remediation strategy. However, at present, the biogeochemical mechanisms controlling Sr transport at the sediment-water interface are poorly understood. In this field study, Sr fate was investigated in two wetlands with contrasting vegetation and hydrologic regimes. The marsh was an open-water wetland with constant water table and no emergent vegetation. The swamp was vegetated with fluctuating water levels and a thick mat of submerged cattail litter in the water column. High-resolution porewater Sr concentrations and solid-phase sediment Sr species revealed distinct profiles between the two wetlands. The marsh exhibited a strongly reduced environment and sharp concentration peaks at the sediment-water interface. In contrast, the smaller concentration gradients of the swamp resulted in a reduced flux of Sr to the surface water. The organic fraction of the sediment dominated Sr retention compared to the inorganic iron and manganese oxides. However, the marsh had a significant fraction of recalcitrant Sr presumably due to its incorporation into sulfur and/or carbonate minerals. These results suggest that vegetated wetlands with fluctuating hydrologic regimes could act as efficient sinks for Sr pollution.

Decomposition characteristics of three different kinds of aquatic macrophytes and their potential application as carbon resource in constructed wetland

Decomposition of aquatic macrophytes usually generates significant influence on aquatic environment. Study on the aquatic macrophytes decomposition may help reusing the aquatic macrophytes litters, as well as controlling the water pollution caused by the decomposition process. This study verified that the decomposition processes of three different kinds of aquatic macrophytes (water hyacinth, hydrilla and cattail) could exert significant influences on water quality of the receiving water, including the change extent of pH, dissolved oxygen (DO), the contents of carbon, nitrogen and phosphorus, etc. The influence of decomposition on water quality and the concentrations of the released chemical materials both followed the order of water hyacinth > hydrilla > cattail. Greater influence was obtained with higher dosage of plant litter addition. The influence also varied with sediment addition. Moreover, nitrogen released from the decomposition of water hyacinth and hydrilla were mainly NH3-N and organic nitrogen while those from cattail litter included organic nitrogen and NO3−-N. After the decomposition, the average carbon to nitrogen ratio (C/N) in the receiving water was about 2.6 (water hyacinth), 5.3 (hydrilla) and 20.3 (cattail). Therefore, cattail litter might be a potential plant carbon source for denitrification in ecological system of a constructed wetland.

Decomposition of Emergent Aquatic Plant (Cattail) Litter Under Different Conditions and the Influence on Water Quality

Decomposition of aquatic plant might generate a significant influence on the receiving water body. In this study, decomposition of emergent aquatic plant (cattail) litter was investigated under different conditions to determine the influencing level of the decomposition process on the water quality. Different litter addition rates (0.1, 0.5, 1.0 g L−1), temperature changes, sediment additions, and kinestates (static and dynamic conditions) were selected as the influencing factors for the decomposition process. The results suggested that the decomposition process could be all accelerated when conducted at a higher litter addition rate, under a cold condition, with sediment addition or on dynamic condition, respectively. Additionally, the maximum ratio of releasing carbon to nitrogen (C/N) was increased when the decomposition process was conducted with a higher litter addition rate, under a cold condition (31.0), with sediment addition (24.6) and on a dynamic condition (28.0), respectively, and the C/N ratios were all higher than that with only 0.5 g L−1 litter addition (24.5), suggesting that lowering of water temperature, sediment addition, and increasing of oxygen might also enhance the C/N. The high C/N released during the decomposition process implied that the cattail litter might be utilized as the potential organic carbon source for nitrogen removal in the CW system.

Performance of experimental horizontal subsurface-flow-constructed wetlands treating river water: effect of substrate, configuration, hydraulic retention time, temperature and external carbon source

The water quality of Yapu River flowing into Lake Taihu was monitored for one year and the effects of substrate, configuration, hydraulic retention time (HRT) and temperature on nitrogen removal were evaluated in five pilot-scale horizontal subsurface-flow-constructed wetlands (CWs). Additionally, the impact of adding external carbon on nitrogen removal was investigated. Yapu River was shown to be eutrophic, with a low C/N ratio (COD/TN ≤ 1.5) and the main pollutant was total nitrogen (TN ≥ 2 mg/L). CWs with substrates of combined gravel-zeolite and gravel-ceramsite showed higher ammonium nitrogen (NH4+-N) and chemical oxygen demand (COD) removal efficiencies than the CWs with gravel substrates. Trapezoidal CWs showed improved dissolved oxygen in the front when compared with the rectangular CWs, enabling complete nitrification. A longer HRT (four days) improved the removal efficiencies of organics, nitrogen, and phosphorus. CWs performed better during the warm period. Moreover, addition of 400 g cattail litter during winter led to increased influent of COD. The average removal efficiencies of NO3--N and TN were increasing up to 90.5 and 85.3%, respectively.

Effects of cattail biomass on sulfate removal and carbon sources competition in subsurface-flow constructed wetlands treating secondary effluent

Sulfate is frequently found in the influent of subsurface-flow constructed wetlands (SSF CWs) used as tertiary treatments. To reveal the effects of plants and litters on sulfate removal, as well as the competition for organic carbon among microorganisms in SSF CWs, five laboratory-scale SSF CW microcosms were set up and were operated as a batch system with HRT 5 d. The results showed that the presence of Typha latifolia had little effect on sulfate removal in CWs, with or without additional carbon sources. Cattail litter addition greatly improved sulfate removal in SSF CWs. This improvement was linked to the continuous input of labile organic carbon, which lowers the redox level and supplies a habitat for sulfate reducing bacteria (SRB). The presence of SRB in cattail litter indicated the possibility of sulfate removal around the carbon supplier, but the quantity of microbes in cattail litter was much lower than that in gravel. Stoichiometry calculations showed that the contribution of SRB to COD removal (21–26%) was less than that of methane-producing bacteria (MPB) (47–61%) during the initial stage but dominated COD removal (42–65%) during the terminal stage. The contributions of aerobic bacteria (AB) and denitrification bacteria (DB) to COD removal were always lower than that of SRB. It was also observed that the variations in COD: S ratio had a great influence on the relative abundance of genes between SRB and MPB and both of them could be used as good predictors of carbon competition between SRB and MPB in CWs.

Effects of plant biomass on denitrifying genes in subsurface-flow constructed wetlands

The effect of Typha latifolia and its litter on density and abundance of three denitrifying genes (nirS, nirK and nosZ) were investigated in six laboratory-scale SSF CW microcosms. Results showed that the copy numbers of nirS, nirK and nosZ in wetland microcosms were ranged between 10(8)-10(9), 10(6)-10(7) and 10(7)-10(8) copies g(-1), respectively. The presence of T. latifolia encouraged the growth of nirK containing bacteria. Addition of cattail litter could greatly stimulate the growth of bacteria containing nirS and nosZ gene. Path analysis illustrated that the presence of plants and litters had no significant direct impact on denitrifying genes, while it affected the denitrifying genes via alteration of dissolved oxygen and carbon sources.

Effects of Alkali-Pretreated Plant Biomass on Nitrate Removal in Subsurface-Flow Constructed Wetlands

Denitrification is strongly dependent on carbon quantity and quality in most constructed wetlands (CWs), and pH may be a key factor in determining the supply of available carbon source (ACS) in the pre-treatment of external plant biomass. In this study, three bath CWs were designed, and were fed with nitrate-dominated water to investigate nitrate removal affected by external cattail litter with different pH pre-treatment (pH = 7.0, 10.0, 12.0). During the experiment, higher nitrate removal was observed in the wetland using pH12.0 pre-treatment litter leachate as the carbon source. Strong alkaline fermentation at ambient temperature can be considered as a sustainable technology for wetland plant litter pre-treatment.

Pretreatment methods for aquatic plant biomass as carbon sources for potential use in treating eutrophic water in subsurface-flow constructed wetlands

Plant biomass is usually added to constructed wetlands (CW) to enhance denitrification. In this study, we investigated effects of different pretreatments on two common external plant carbon sources, cattail and reed litter. We determined the average ratio of chemical oxygen demand (COD) to total nitrogen (TN), designated as C/N, in water samples after addition of litter subjected to various pretreatments. The C/N in the water samples ranged from 4.8 to 6.4 after addition of NaOH-pretreated cattail litter, which was four to six times greater than that of water from the Yapu River and 3.84-39.15% higher than that of systems that received untreated cattail litter. The C/N of systems that received H(2)SO(4)-pretreated carbon sources varied from 1.7 to 3.6. These two methods resulted in TN and total phosphorus (TP) levels lower than those in river water. The C/N was 1.4-1.7 after addition of CH(3)COOH-pretreated reed litter, which was 34.87-53.83% higher than that of river water. The C/N was 2.5 in systems that received mild alkali/oxidation-pretreated reeds, which was 30.59% higher than that of systems that received non-pretreated reeds. The residue rates of cattail and reed litter subjected to various pretreatments were greater than 60%. Our results showed that NaOH, H(2)SO(4), and mild alkali/oxidation pretreatments were useful to rapidly improve the C/N of river water and enhance denitrification.

Development of a Constructed Wetland Water Treatment System for Selenium Removal: Use of Mesocosms to Evaluate Design Parameters

The Salton Sea in California is an important habitat for fish and waterfowl. Its ecosystem is threatened due to diminishing water supplies and increasing salinity. An alternative source of water to support species conservation habitat may be obtained from local rivers (e.g., Alamo or New Rivers), provided that a wetland treatment system can be developed to remove selenium (Se), fertilizer nutrients, and other contaminants. Here, we used mesocosms to evaluate a number of potential design options (e.g., plant species selection, sediment composition and arrangement, forced aeration, organic amendments, etc.) to improve the efficiency of Se removal using treatment wetlands. Our results show that, of five different substrate arrangements tested for Se removal, the most efficient was obtained for cattails growing in a substrate of cattail litter overlying sand and peat moss sediment (water column Se was reduced from 15 μg Se/L to <0.1 μg Se/L in 72 h). The addition of organic amendments in the form of alfalfa hay or alfalfa meal was also helpful in lowering Se levels. These results suggest that it may be possible to design constructed wetland water treatment systems capable of reducing Se concentrations in river water to values below 1 μg Se/L.

Litter decomposition in created and reference wetlands in West Virginia, USA

Large amounts of resources have gone into wetland mitigation in recent years; however, it is still unclear whether wetland function is being replaced along with wetland area. Litter decomposition is linked to numerous wetland functions. In this study, we measured plant litter decomposition potential over 12 months in 8 created and 8 reference wetlands located in the Allegheny Mountains of West Virginia, USA. Broadleaf cattail (Typha latifolia L.) litter bags were placed in each wetland and collected at 3 month intervals. Linear decomposition rate constants and percent mass remaining were similar between wetland types (created and reference) and among Cowardin classifications (palustrine: unconsolidated bottom, aquatic bed, emergent, and scrub/shrub). Created wetland age was not correlated with decomposition potential. Our study found that created wetlands had similar litter decomposition potential as reference wetlands indicating that similar processes are likely acting upon litter decomposition within both natural and created wetlands.

Effects of plant biomass on nitrate removal and transformation of carbon sources in subsurface-flow constructed wetlands

Denitrification is strongly dependent on carbon quantity and quality in most constructed wetlands (CWs). In this study, four batch CWs were designed, and were fed with nitrate-dominated water to investigate nitrate removal affected by plant and external cattail litter with or without alkali pretreatment. The results showed that the unit with plant and alkali-pretreated litter was more efficient in the initial stage whereas unit with plant and unpretreated litter was superior to other units in the middle and terminal stages. Plant accounted for less than 37% of the nitrate removal in biomass-up added CWs. The different nitrate removal rates were found to be greatly affected by the composition of the plant biomass as well as the quantity and quality of the available organic matters. It was also observed that plant biomass degradation over the period of this study resulted in various N species and concentrations in effluent.

Litter accumulation promotes dominance of invasive species of cattails (Typha spp.) in Lake Ontario wetlands

Wetlands of the Great Lakes region are increasingly dominated by invasive cattails (Typha angustifolia and Typha X glauca) which form dense stands of live and dead biomass that may reduce plant diversity. We hypothesized that differences in plant litter accumulation explain cattail dominance under certain hydrologic regimes related to wetland hydrogeologic setting. We investigated cattail abundance, litter accumulation, and species density in three bayside wetlands hydrologically connected and three protected wetlands hydrologically isolated from Lake Ontario. Mean litter biomass was higher in bayside wetlands (1.7-2.6 vs. 0.4-1.2 kg/m 2 ) and negatively related to species density (p 5 0.004) in both settings. A litter addition experiment demonstrated that fallen litter negatively influenced seedling survival (p 5 0.061) and species density (p 5 0.024). Decomposition rates accounted only partially for higher overall litter accumulation in bayside wetlands. Growing season water levels in bayside wetlands tracked Lake Ontario levels and showed less variation than protected wetlands. More stable water levels and higher density of standing dead stems in bayside wetlands may limit litter fragmentation, resulting in greater litter accumulation. Thus, anthropogenic and natural factors affecting cattail litter production, fragmentation, and decomposition could influence species diversity in coastal wetlands.

Nitrate removal and DO levels in batch wetland mesocosms: Cattail ( Typha spp.) versus bulrush ( Scirpus spp.)

Nitrate removal rates and dissolved oxygen (DO) levels were evaluated in small batch-mode wetland mesocosms with two different plant species, cattail ( Typha spp.) and bulrush ( Scirpus spp.), and associated mineral-dominated sediment collected from a mature treatment wetland. Nitrate loss in both cattail and bulrush mesocosms was first-order in nature. First-order volumetric rate constants ( k V) were 0.30 d −1 for cattail and 0.21 d −1 for bulrush and rates of nitrate loss were significantly different between plant treatments ( p < 0.005). On an areal basis, maximum rates of nitrate removal were around 500 mg N/(m 2 d) early in the experiment when nitrate levels were high (> 15 mg N/L). Areal removal rates were on average 25% higher in cattail versus bulrush mesocosms. DO in mesocosm water was significantly higher in bulrush versus cattail ( p < 0.001). DO in bulrush generally ranged between 0.5 and 2 mg/L, while DO in cattail mesocosms was consistently below 0.3 mg/L. Based on cumulative frequency analysis, DO exceeded 1 mg/L around 50% of the time in bulrush, but only 2% of the time in cattail. DO in bulrush exhibited a statistically significant diel cycle with DO peaks in the late afternoon and DO minimums in the early morning hours. Difference in nitrate removal rates between wetland plant treatments may have been due to differing plant carbon quality. Cattail litter, which has been shown in other studies to exhibit superior biodegradability, may have enhanced biological denitrification by fueling heterotrophic microbial activity, which in turn may have depressed DO levels, a prerequisite for denitrification. Our results show that the cattail is more effective than bulrush for treating nitrate-dominant wastewaters.

Enhanced nitrate removal efficiency in wetland microcosms using an episediment layer for denitrification.

Microbial denitrification is the principal removal mechanism for nitrogen in treatment wetlands. For this study, flow-through wetland microcosms were designed to testwhether variations in the macroporous structure of the denitrification zone affected overall nitrate removal. In a sediment-only treatment, carbon as cattail (Typha latifolia) litter was mixed throughout a porous sediment matrix. A second treatment contained a distinct layer of loosely aggregated litter pieces placed atop the sediment matrix to form an episediment zone. Results showed that across nine conditions (NO3- influent = 7, 36, 65 mg N L(-1) and t(res) = 2.2, 2.9, 4.4, 7.7 d; n = 48) average denitrification was 33% greater (p < 0.0001) in the episediment treatment than in the sediment-only treatment. Both sediment-only and episediment treatments followed apparent reaction kinetics close to first order, with k(epi) = 0.21 d(-1) for the episediment treatment and k(sed) = 0.12 d(-1) for the sediment-only treatment. Analysis of vertical nitrate profile data using diffusive and turbulent mixing models indicated that denitrification occurred in a partially mixed episediment layer, as well as in an underlying sediment layer. Approximately 40% of the nitrate removal that occurred in the episediment treatment was estimated to occur in the episediments themselves. We conclude that enhancementof an episediment layer can increase denitrification in treatment wetlands which receive nitrate in overlying water.