Carbon Amendments Research Articles

Denitrification in a Grassed and a Wooded, Valley and Ridge, Riparian Ecotone

Dentrification is one of the major mechanisms responsible for changes in NO3−-N concentrations in shallow groundwater as subsurface flow passes from agricultural fields to the stream. In this study, denitrification is examined in a grassed and wooded riparian ecotone common to the Valley and Ridge physiographic province in Pennsylvania. Denitrification rates of 102 and 10 µg N kg−1 soil d−1 were measured using soil slurry and intact core incubation techniques, respectively. The grassed riparian site exhibited greater denitrification rates than the wooded site. Carbon amendments resulted in an increase in denitrification at the wooded site and suggest that denitrification may be C limited at this site. Denitrification generally decreased with distance away from the stream and also decreased with depth in the soil. Patterns of denitrification measured with the soil slurries corresponded closely to patterns of soil NO3− content.

DNA‐based monitoring of total bacterial community structure in environmental samples

Determining the structure of bacterial communities and their response to stimuli is key to understanding community function and the interactions that occur between micro-organisms and the environment. However, bacterial communities often comprise complex assemblages of large numbers of different bacterial populations. An approach is presented which allows bacterial community structure to be determined by fractionation of the complex mixture of total bacterial community DNA using the DNA-binding dye bisbenzimidazole which imposes G+C-dependent changes in the buoyant density of DNA. Bacterial community structure presented as percentage of total DNA vs. percentage G+C content of DNA is an indication of the relative abundance of phylogenetic groups of bacteria. Changes in the composition of a soil bacterial community in response to perturbations in the form of carbon amendment and altered water status were monitored.

Factors affecting the survival of a FLavo bacterium species in non-planted and rhizosphere soil

Factors affecting the survival of a Gram-negative soil Flavobacterium sp. (P25) were investigated in small-scale laboratory microcosms. Two terms for expressing P25 persistence are used: survival—describing the number of P25 reisolated from soil at a certain time point; and survival rate—expressed as the time in days taken for a 90% (t90), 99% (t99) or 99.9% (t99.9) decline in numbers of P25. Survival rates of P25 increased in rhizosphere as opposed to bulk soil and were increased further by applying the inoculum directly to the planted seedling (t99 = 21 d) rather than homogenizing it through the soil prior to planting (t99= 10.5d). Survival was increased by using greater inoculum densities, for example following inoculation at 1,1 × 10 9P25 g −1soil, numbers surviving at day 40 were 12.5-fold greater than that achieved with 1.1 × 10 4 P25 g −1 In addition, survival rates of P25 were increased by applying the inoculant to soil at moisture holding capacities (MHC) between 40 and 50% (t99.9 = 12.2 d) in comparison to either wetter (e.g. 100% MHC, t99.9 = 3.5 d) or drier (e.g. 10% MHC, t99.9 = 1 d) soils. Carbon amendments (i.e. galactose, maltose, sorbitol) significantly increased survival of P25 in non-planted soil throughout the 35 d study whereas in rhizosphere soil an increase was only recorded for the first 14 d.

Changes in composition of soil polysaccharides and aggregate stability after carbon amendments to different textured soils

Changes in the composition of soil polysaccharides, after amendment and incubation of different textured soils with either ground wheat-straw or glucose, were studied in relation to microbial activity and aggregate stability. Analyses of free and soil (straw)-bound saccharides were carried out by high performance anion exchange chromatography with pulsed amperometric detection (HPLC-PAD). Eighty-five percent of the added glucose was respired after 15 days of incubation (15°C). Metabolism of the glucose amendment did not affect the total soil saccharide content of a loamy sand during the course of the experimentation period. By contrast, total soil saccharides declined to approximately 50% of the unamended (control) silty loam. In the straw treatments, more of the straw saccharides remained in the loamy sand (54.9%) than in the silty loam (26.4%) after 15 days of incubation. At the end of the experiment (after 220 days) the saccharide concentrations of both treatments had approached those of the unamended control soils. The monosaccharide content of soils followed the same trend in most cases, these concentrations reflecting the degradation process in the straw amendment treatments. Mannose apparently was synthesized by soil microorganisms. Glucose and straw metabolism led to a significant increase in aggregate stability in the three soils during the incubation time. Independent of the clay content of the soils, aggregate stability was still pronounced together with an increased microbial biomass level (straw treatment only) after 220 days. However, no direct link between a specific monosaccharide content and aggregate formation or stability could be shown. Polysaccharide production seemed to be related to C-availability or C over-supply.

Selenium Mobility in Irrigated Soil Columns as Affected by Organic Carbon Amendment

Selenium Mobility in Irrigated Soil Columns as Affected by Organic Carbon Amendment

Selenium Mobility in Irrigated Soil Columns as Affected by Organic Carbon Amendment

Selenium Mobility in Irrigated Soil Columns as Affected by Organic Carbon Amendment

Selenium Mobility in Irrigated Soil Columns as Affected by Organic Carbon Amendment

Journal of Environmental QualityVolume 20, Issue 4 p. NP-NP ErrataFree Access Selenium Mobility in Irrigated Soil Columns as Affected by Organic Carbon Amendment This article corrects the following: Selenium Mobility in Irrigated Soil Columns as Affected by Organic Carbon Amendment Rosemary H. Neal, Garrison Sposito, Volume 20Issue 4Journal of Environmental Quality pages: 808-814 First Published online: October 1, 1991 Rosemary H. Neal, Rosemary H. NealSearch for more papers by this authorGarrison Sposito, Garrison SpositoSearch for more papers by this author Rosemary H. Neal, Rosemary H. NealSearch for more papers by this authorGarrison Sposito, Garrison SpositoSearch for more papers by this author First published: 01 October 1991 https://doi.org/10.2134/jeq1991.00472425002000040017xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume20, Issue4October‐December 1991Pages NP-NP RelatedInformation

Selenium Mobility in Irrigated Soil Columns as Affected by Organic Carbon Amendment

AbstractSamples of two agricultural soil profiles were collected from the western San Joaquin Valley, CA, and packed into 1.5‐m columns. The soils were leached sporadically over 9 wk with an aqueous solution containing selenate and subjected to two different chemical environments in order to investigate the effects of an added C source and intermittent irrigation on the fate of applied Se. Evaluation of the soluble Se present in the soil columns at the end of the leaching experiments showed the movement of Se to be retarded with respect to that of the leaching solution, and this was attributed to the effect of intermittent irrigation on the behavior of Se in the soil columns. Under control conditions, soluble Se was predominantly in the selenate form, whereas the inclusion of a C amendment resulted in reduced total soluble Se in the upper portions of the columns and transformation to organically associated Se. Elevated concentrations of soluble Mn were found where selenate had transformed to selenite and organically associated Se, indicating the possibility of localized reduction processes.

Stimulation of aldrin and dieldrin loss from soils treated with carbon amendments and saturated-ring analogues

The use of amendments (such as organic supplements and pesticide analogues) to enhance the biodegradation of organochlorines has received little attention. Maule et al. (1987) noted increased monodechlorination of dieldrin in the presence of formate and Guenzi and Beard (1968) found the addition of 1% alfalfa to DDT-contaminated soils promoted the formation of DDD. The present study investigates the effect of carbon amendments and analogues on the disappearance of aldrin and dieldrin residues from soil. MATERIALS AND METHODS Soil samples were collected from a 40 m 3 soil pile contaminated with aldrin (6.5 mg kg -I) and dieldrin (3.3 mg kg-1). The samples were sieved through a 5 m m mesh and stored in glass jars at ambient temperatures until used. The soil pile was located at a site in the Beaudesert Industrial estate, Brisbane and was the result of excavations from around the base of 28 wooden power poles treated with a technical aldrin-creosote mix to control termite pests. Disposable 5 ml syringes were used as incubation vessels for soil samples. They were adapted by cutting the Send reprint requests to P. Hugenholtz at the above address.

Preface

The in situ use of carbon amendments such as activated carbon (AC) and biochar to minimize the bioavailability of organic contaminants is gaining in popularity. In the first in situ experiment conducted at a Canadian PCB-contaminated Brownfield site, GAC and two types of biochar were statistically equal at reducing PCB uptake into plants. PCB concentrations in Cucurbita pepo root tissue were reduced by 74%, 72% and 64%, with the addition of 2.8% GAC, Burt's biochar and BlueLeaf biochar, respectively. A complementary greenhouse study which included a bioaccumulation study of Eisenia fetida (earthworm), found mechanically mixing carbon amendments with PCB-contaminated soil (i.e. 24 h at 30 rpm) resulted in shoot, root and worm PCB concentrations 66%, 59% and 39% lower than in the manually mixed treatments (i.e. with a spade and bucket). Therefore, studies which mechanically mix carbon amendments with contaminated soil may over-estimate the short-term potential to reduce PCB bioavailability.

Rhizosphere oxygenation by Typha domingensis Pers. in miniature artificial wetland filters used for metal removal from wastewaters

Miniature artificial wetland filters were used to treat a metal-enriched synthetic effluent by upward percolation through a gravel substratum. The systems were either planted with Typha domingensis Pers. or unplanted, and were with or without lactic acid or ground leaves as carbon amendments to enhance biological oxygen demand. Oxygen concentration, pH, redox potential and metal retention were higher in planted systems than in systems without plants. Respiration was increased by carbon amendments in all filters. Oxygen concentration in unplanted filters declined, but rhizosphere aeration maintained oxygenated conditions in all planted filters. The results demonstrate that available carbon supply improved heavy metal removal in the artificial wetland filters and affected the rate of rhizosphere oxygenation. Rhizosphere oxygenation, calculated from the sum of respiration and net oxygenation observed in static assay, was of the order of at least 80–300 μg l −1 h −1, or 210–750 μg h −1 filter −1.

Influence of inorganic and organic nutrients on aerobic biodegradation and on the adaptation response of subsurface microbial communities.

The influence of inorganic and organic amendments on the mineralization of ethylene dibromide, p-nitrophenol, phenol, and toluene was examined in subsurface soil samples from a pristine aquifer near Lula, Okla. The responses indicate that the metabolic abilities and nutrient requirements of groundwater microorganisms vary substantially within an aquifer. In some samples, additions of inorganic nutrients resulted in a more rapid adaptation to the test substrate and a higher rate of metabolism, indicating that metabolism may have been limited by these nutrients. In other samples from the same aquifer layer, inorganic amendments had little or no influence on mineralization. In general, the addition of multiple inorganic nutrients resulted in a greater enhancement of degradation than did the addition of single substances. Additions of alternate carbon sources, such as glucose or amino acids, inhibited the mineralization of the xenobiotic substrates. This inhibition appears to be the result of the preferential utilization of the more easily degradable carbon amendments.

Effect of organic compounds on the microbiological leaching of a complex sulphide ore material

Microbiological leaching of metals from sulphide ore material was evaluated with a pure culture ofThiobacillus ferrooxidans and with three mixed cultures of acidophiles. Organic carbon amendment was found to be a prerequisite for the microbiological extraction of metals from this ore material, regardless of the culture tested. The concentration of the organic compounds necessary for the biological leaching was related to the pulp density of the ore material. Surfaceactive agents did not increase the recoveries of nickel, zinc, copper and cobalt but several complex organic materials had a positive effect on the bacterial leaching. The chemical leaching was not influenced by the test compounds.

Carbon Mineralization in Acidic, Xeric Forest Soils: Induction of New Activities

Carbon mineralization was examined in Lakehurst and Atsion sands collected from the New Jersey Pinelands and in Pahokee muck from the Everglades Agricultural Area. Objectives were (i) to estimate the carbon mineralization capacities of acidic, xeric Pinelands soils in the absence of exogenously supplied carbon substrate (nonamended carbon mineralization rate) and to compare these activities with those of agriculturally developed pahokee muck, and (ii) to measure the capacity for increased carbon mineralization in the soils after carbon amendment. In most cases, nonamended carbon mineralization rates were greater in samples of the acid- and moisture-stressed Pinelands soils than in Pahokee muck collected from a fallow (bare) field. Carbon amendment resulted in augmented catabolic activity in Pahokee muck samples, suggesting that the microbial community was carbon limited in this soil. With many of the substrates, no stimulation of the catabolic rate was detected after amendment of Pinelands soils. This was documented by the observation that amendment of Pahokee muck with an amino acid mixture, glucose, or acetate resulted in a 3.0-, 3.9-, or 10.5-fold stimulation of catabolic activity, respectively, for the added substrate. In contrast, amendment of the Pinelands soils resulted in increased amino acid and acetate catabolic rates in Lakehurst sand and increased acetate metabolism only in Atsion sand. Other activities were unchanged. The increased glucose respiration rates resulted from stimulation of existing microbial activity rather than from microbial proliferation since no change in the microbial growth rate, as estimated by the rate of incorporation of C-labeled acetate into cell membranes, occurred after glucose amendment of the soils. A stimulation of microbial growth rate was recorded with glucose-amended Lakehurst sand collected from the B horizon.

Effectiveness of submersed angiosperm-epiphyte complexes on exchange of nutrients and organic carbon in littoral systems. III. Refractory organic carbon

Refractory dissolved organic compounds, consisting mainly of fulvic acids labelled with 14C of aquatic plant origin, were added to the inlet stream water of a hardwater lake and passed through two continuously, very slowly flowing ( 3 1 24 h ) littoral systems. System I contained a natural stand of Scirpus subterminalis Torr. and System II contained Myriophyllum heterophyllum Michx. Macrophytic epiphytic were left intact. Control systems, containing similar sediments without macrophytes, received identical treatments. Dissolved organic carbon (DOC), both labelled and unlabelled, of inflow and outflow water was fractionated into several molecular weight fractions; UV absorption and fluorescence of dissolved organic matter, particulate organic carbon (POC), and major cationic concentrations were also analyzed in inflowing and outflowing water. The pathways of the labelled refractory organic carbon amendments were followed in the water, the plant foliage and roots, epiphytes, and the sediments. DOC inputs, especially of high molecular weight, were appreciably reduced in the gradual movement through the macrophyte—epiphyte complexes, although more dissolved fluorescing organic matter of > 1000 Daltons was released from the plant complexes than from control systems without macrophytes. Cationic concentrations of calcium and magnesium were reduced markedly by passage through the littoral systems; those of sodium increased slightly from the Myriophyllum community. While a major portion of the labelled refractory dissolved organic compounds moved directly through the littoral complexes, reductions were found in outflows from the Scirpus system and increases in the < 1000 Dalton fractions from the Myriophyllum system. Both plant systems removed POC from inflowing waters. Appreciable quantities of labelled carbon of refractory DOC origin were found associated with the Scirpus and Myriophyllum plant tissue. Greater activity was found in the root tissue than in the shoots, and in plants located at the inlet end as compared to those growing at the outlet end of the littoral systems. Epiphytes contained appreciable quantities of labelled DOC, much of which was associated with precipitated CaCO 3. Greater amounts of labelled refractory DOC of sand sediments were found associated with precipitated CaCO 3 in the plant systems than in sediment control systems.

Phases of denitrification following oxygen depletion in soil

The short-term response of soil denitrification to reduced aeration was studied using the acetylene inhibition method for the assay of denitrification. Two distinct phases of denitrification rate were observed. An initial constant rate, termed phase I, was not decreased by chloramphenicol, was increased slightly or not at all by organic carbon amendment, and lasted for 1–3 h. Phase I was attributed to the activity of pre-existing denitrifying enzymes in the soil microflora. Following phase I the denitrification rate increased; chloramphenicol inhibited this increase. In soils without organic-C amendment a second linear phase, termed phase II, was attained after 4–8 h of anaerobic incubation. The linearity of this phase was attributed to the full derepression of denitrifying enzyme synthesis by the indigenous population and to the lack of significant growth of denitrifiers. Phase I rate was dependent on the initial or in situ aeration state of the soil sample; phase II was not. Therefore, phase I may be more directly related to field denitrification rates. Denitrification rate changes following water saturation of soils in aerobic atmospheres were also examined. Rates were greatly increased by wetting but only after a lag of several hours. Our interpretation is that following wetting of natural soils, anaerobic or partially anaerobic conditions are established by respiration and reduced O 2 diffusion rate; this first eliminates O 2 inhibition then derepresses the synthesis of denitrifying enzymes. Although denitrifying enzymes are apparently present even in relatively dry soils, their activity is low until O 2 inhibition is eliminated. From this evidence we reason that most N is lost from soils during brief periods beginning a few hours after irrigation or a rainfall.

Effects of soil water suction, soil temperature, carbon and nitrogen amendments, and host rootlets on survival in soil of zoospores of Phytophthora cactorum

Zoospores of P. cactorum were added to air-dry soil and recovered periodically on soil-dilution plates. Such inoculum survived longer in relatively dry soil than in wet soil. Temperature at which soil was stored after infestation had little effect on persistence but survival tended to be longer at 10 °C than at 26.7 °C. Adding dextrose or sucrose, and ammonium sulfate, alone or together, had no appreciable effect on fungus survival. Addition of urea, 500 ppm N w/w air-dry soil, shortened considerably the period through which cysts were recovered on dilution plates. This effect was not obtained with urea 250 ppm N. Other common nitrogen fertilizers had no consistent effect on fungus survival. When sprouted apple seeds were planted in soil infested with zoospores, the number of propagules increased substantially and the fungus was recovered for several weeks longer from planted than from non-planted soil. Soil may be infested with P. cactorum more readily by using zoospores than by using other propagules.