ABSTRACT
To explore the differences in structure and diversity of nirK-type denitrifying microbial community in marsh soils at different invasion stages of Spartina alterniflora, the mudflat (MF, before invasion) and the S. alterniflora marsh after seaward invasion for 1-2 years (SAN) and 6-7 years (SA) in Shanyutan of the Minjiang River estuary were investigated by high-through put sequencing method. Results showed that the seaward invasion of S. alterniflora reduced the richness and diversity of nirK-type denitrifying microbial community in marsh soils. The nirK-type denitrifying microbial community in soils at different invasion stages included Proteobacteria and Actinobacteria, with Proteobacteria as the dominant one. The seaward invasion of S. alterniflora greatly altered the composition of nirK-type denitrifying microbial community in marsh soils. The highest relative abundance of genus in soils from different invasion stages were Bradyrhizobium, Mesorhizobium and Alcaligenes, respectively. The seaward invasion of S. alterniflora increased the spatial heterogeneity of nirK-type denitrifying microbial community composition in marsh soils. In SAN plot, the enhancement of spatial heterogeneity was primarily due to higher environmental disturbances in plots and the increased spatial heterogeneity of environmental variables caused by the seaward invasion of S. alterniflora. The seaward invasion of S. alterniflora altered the physico-chemical properties (e.g., grain composition, pH and moisture) and N nutrient conditions (total N, NH4+-N and NO3--N) in marsh soils, which greatly altered the structure and diversity of nirK-type denitrifying microbial community. Our findings reveal the microbial mechanism of denitrification process in marsh soils during the seaward invasion of S. alterniflora.
Subject(s)
Microbiota , Wetlands , Soil/chemistry , Estuaries , Rivers , Introduced Species , PoaceaeABSTRACT
We examined the effects of Spartina alterniflora invasion on phosphorus forms of marsh soils, based on the method of space-for-time substitution by selecting S. alterniflora marshes with different invasion years (SA1, 5-6 years; SA2, 8-10 years; and SA3, 12-14 years) in Shanyutan of the Minjiang River estuary. The results showed that in marsh soils of different invasion years, the proportion of hardly decomposable phosphorus (HCl-Pi and Residual-P) was the highest (46.4%-46.7%), followed by moderately decomposable phosphorus (NaOH-Pi, NaOH-Po and Sonic-Pi) (40.0%-44.0%), and the easily decomposable phosphorus (Resin-Pi, NaHCO3-Pi and NaHCO3-Po) was the lowest (9.5%-13.3%). With increasing invasion years of S. alterniflora, soil phosphorus forms and their spatial distributions were greatly altered. The contents of moderately decomposable phosphorus, hardly decomposable phosphorus, and total phosphorus (TP) generally increased, while easily decomposable phosphorus content generally decreased. Compared with SA1, the contents of moderately decomposable phosphorus, hardly decomposable phosphorus and TP in SA2 increased by 11.5%, 9.7% and 10.5%, while those in SA3 increased by 24.8%, 13.2% and 13.5%, respectively. The distribution of phosphorus forms was greatly altered with increasing invasion years, which was dependent on the variations of key factors such as EC, pH value and grain composition. The implementation of regular mowing activities for S. alterniflora in the Minjiang River estuary in recent years, to some extent, reduced the return of phosphorus from residues to soils and decreased the availability of the easily decomposable phosphorus in soils.
Subject(s)
Soil , Wetlands , China , Estuaries , Introduced Species , Phosphorus/analysis , Poaceae , Rivers , Sodium Hydroxide , Soil/chemistryABSTRACT
Sulfur oxidation-reduction process (SORP) in marsh soil is an important link in sulfur cycle, which plays an important role in maintaining the stability and health of marsh. We summarized the SORP in marsh soil and its influencing factors, and analyzed the research progress of its coupling effects with other elements. The influencing factors of SORP in marsh soil mainly involved biotic (plants, microorganisms, zoobenthos, human activities, etc.) and abiotic factors (physical factors such as temperature, moisture and particle size, and chemical factors such as pH, salinity, organic matter, etc.). Related research on the coupling effects of SORP and other elements in marsh soil mainly involved in biogenic elements such as carbon (C), nitrogen (N) and phosphorus (P), and metal elements such as iron (Fe) and manganese (Mn). Currently, the underlying mechanism of SORP was not deeply explored, the research on coupling effects was unbalance, and the ecological effects were insufficient. In the future, key functional microorganisms involved in SORP should be strengthened, the coupling mechanism between SORP and micro-elements should be enhanced, and the ecological effects produced by the coupling effects of SORP with other elements should be emphasized.
Subject(s)
Soil , Wetlands , Carbon , Humans , Oxidation-Reduction , Soil/chemistry , SulfurABSTRACT
To investigate the distributions and stocks of total phosphorus (TP) in plant-soil systems of marshes in Shanyutan of the Minjiang River estuary and explore its influencing factors, Phragmites australis (PA) marsh and Cyperus malaccensis (CM) marsh before spatial expansion and ecotonal marsh (EM, P. australis and C. malaccensis in EM were denoted by PA' and CM', respectively) during spatial expansion were studied. Results showed that, as affected by spatial expansion, the contents of TP in both plant and soil in different marshes showed great variations. Compared with PA and CM marshes, soil TP in EM increased by 20.0% and 7.1%, respectively. The variation of soil TP in EM might be attributed to the alteration of soil particle composition, plant bio-mass and root/shoot ratio during spatial expansion. Except for leaves, TP in organs of P. australis in P. australis-C. malaccensis community (PA') was lower than that in C. malaccensis in P. australis-C. malaccensis community (CM'), due to the differences in absorption, utilization and translocation way of P among organs between the two species. The competition effect caused by spatial expansion greatly changed plant P allocation ratio of the two species. Compared with PA and CM, the allocations of P in roots and leaves of PA' increased, while only that in roots of CM' rose. During spatial expansion, the two species might adopt different adaptation strategies for P absorption and utilization to maintain their competitiveness. The PA might compete primarily by strengthening the P accumulation capacities of its roots and promoting leaf photosynthesis, whereas the CM might resist the spatial expansion of PA by increasing its underground biomass to enhance P absorption.
Subject(s)
Cyperus , Estuaries , China , Phosphorus , Poaceae , Rivers , Soil , WetlandsABSTRACT
In this work, Bi(4)Nb(x)Ta((1-x))O(8)I photocatalysts have been synthesized by solid state reaction method and characterized by powder X-ray diffraction, scanning electron microscope and UV-Vis near infrared diffuse reflectance spectroscopy. The photocatalytic activity of these photocatalysts was evaluated by the degradation of methyl orange (MO) in aqueous solutions under visible light, UV light and solar irradiation. The effects of catalyst dosage, initial pH and MO concentration on the removal efficiency were studied, and the photocatalytic reaction kinetics of MO degradation as well. The results indicated that Bi(4)Nb(x)Ta((1-x))O(8)I exhibited high photocatalytic activity for the removal of MO in aqueous solutions. For example, the removal efficiency of MO by Bi(4)Nb(0.1)Ta(0.9)O(8)I was as high as 92% within 12 h visible light irradiation under the optimal conditions: initial MO concentration of 5-10 mg L(-1), catalyst dosage of 6 g L(-1) and natural pH (6-8), the MO molecules could be completely degradated by Bi(4)Nb(0.1)Ta(0.9)O(8)I within 40 min under UV light irradiation, and the photodegradation efficiency reaches to 60% after 7 h solar irradiation. Furthermore, the photocatalytic degradation of Bisphenol A (BPA) was also investigated under visible light irradiation. It is found that 99% BPA could be mineralized by Bi(4)Nb(0.1)Ta(0.9)O(8)I after 16 h visible light irradiation. Through HPLC/MS, BOD, TOC, UV-Vis measurements, we determined possible degradation products of MO and BPA. The results indicated that MO was degradated into products which are easier to be biodegradable and innocuous treated, and BPA could be mineralized completely. Furthermore, the possibility for the photosensitization effect in the degradation process of MO under visible light irradiation has been excluded.
