Mixture Of Peat Research Articles

NITROGEN BALANCE OF THREE ORGANIC POTTING-MEDIA IN RELATION TO THE ADDED CARBON SOURCES

NITROGEN BALANCE OF THREE ORGANIC POTTING-MEDIA IN RELATION TO THE ADDED CARBON SOURCES

Performance of a full-scale biofilter with peat and ash as a medium for treating industrial landfill leachate: a 3-year study of pollutant removal efficiency

Shredder residues of end-of-life vehicles and white goods are a complex waste stream, which nowadays most often is disposed of at industrial landfills. This paper describes the most important findings concerning the complex composition of the landfill leachate and its on-site, year-round treatment under cold-climate conditions. A 3-year investigation has confirmed that concentrations of different types of pollutants, most of them at low initial concentrations, can be simultaneously reduced in vertical-flow biofilters consisting of a mixture of peat and carbon-containing ash. For metals such as Mn, Cu, Sn, Cd, Pb, Fe and Ni the average removal was 73, 72, 66, 60, 55, 55 and 37%, respectively. An average reduction of NH(4)-N (45%), N(tot) (25%), total organic carbon (30%), dissolved organic carbon (28%) and suspended solids (38%) was also obtained. A good reduction was achieved for phenols (between 75 and 95%), polychlorinated biphenyls (between 22 and 99%), and gas chromatography-mass spectrometry amenable pollutants, considered at initial concentration above 50 microg L( -1) (between 80 and 100%). The performance of the biofilter system was good in spite of large variations of inlet concentration during the considered period.

Inverse modeling of pesticide degradation and pesticide-degrading population size dynamics in a bioremediation system: Parameterizing the Monod model

Pesticide degradation models are compared which simulate the response of biofilters for treatment of pesticide-contaminated waste water to time-irregular pesticide supply in which the pesticide is used for growth and mineralized. Biofilter microcosms containing a mixture of straw, peat and soil and harboring micropopulations which uses the herbicide linuron for growth, were irrigated with linuron for 28 weeks with a stop in its supply between week 12 and 17. Matrix samples were regularly taken to assay linuron mineralization. A first-order approximation of the Monod model was used to simulate the observed mineralization data, while an inverse modeling framework combining a sensitivity analysis (Morris Sensitivity Analysis) with an inverse modeling approach (Shuffled Complex Evolution Metropolis) adopted to parameterize the model. Lag times in linuron mineralization decreased during the initial weeks of linuron irrigation but increased after supply of linuron ceased. The model well-simulated the lag time dynamics which were related to the dynamics of the predicted linuron-degrading population size in the microcosms. It was predicted that the population size decreased at a rate of 0.031 d −1 after pesticide supply ceased to reach its initial population size after 25 weeks. We conclude that modeling pesticide degradation in biofilters should incorporate biomass dynamics in case the pesticide is used as C-source. First-order approaches without incorporating biomass dynamics could lead to underestimation of the risk of pesticide leaching.

The effect of rockwool on physical properties of growing substrates for perennials 38

The possibility of peat replacement with crushed water absorbent rockwool in growing substrates in the amount of 35% vol. was verified in the experiment with perennials in containers. Three types of substrates, i.e. peat, and two mixtures of peat with alternative components – green waste compost (25% vol.) or composted spruce bark (40% vol.) were compared. A sand box in the range of –0.5 to –10 kPa was used to determine retention curves and other physical properties of the components and substrates. The addition of rockwool to the peat substrate increased content of air and easy available water, the plant growth was not affected. Plants grown in substrates with alternative organic components were smaller in comparison to peat substrate. The growth of perennials significantly decreased, mainly in substrates with bark, but the plants had good market value. The addition of rockwool to these substrates had no significant effect on the growth. Crushed rockwool in the amount of 35% vol. can replace peat in peat substrates and in mixtures with alternative components.

In vitro and in vivo germination of Cyclamen alpinum seeds

Cyclamen trochopteranthum O.Schwarz has a confusing history, having been identified in the last part of the 19^{th} century and described as Cyclamen alpinum Sprenger. It remained known as C. alpinum until 1975, when it was described as C. trochopteranthum by Otto Schwarz. Cyclamen trochopteranthum is a species distributed in the south-western part of Turkey, but the C. trochopteranthum described in 1975 is today describe again as Cyclamen alpinum. The seeds of this species were collected from red pine forests in the Gökbel-Dalyan area on May 3-7 and stored with and without capsules in incubators at 20 °C. Among the seeds that were sown 5-6 months later (October-November), the germination rate was 35% at 15 °C and 47% at 20 °C in October. Germination increased to 80% at 15 °C and 87% at 20 °C in November. The highest germination rate was observed in December (95%) and these seeds had been stored for 8 months. Seeds that were stored for 8 months (using different storage methods) were subjected to in vitro and in vivo germination tests at 15 °C and 20 °C. Seed storage method (in capsules and out of capsules) did not have a significant effect on in vitro germination in Murashige-Skoog medium, but storing seeds in capsules had a significant effect on germination on filter paper and in vivo (mixtures of peat, perlite, and sand). In darkness at 15 and 20 °C high germination rates were obtained, both in vitro and in vivo (in vitro at 15 and 20 °C, max. 95%; in vivo at 15 °C, max. 73%; at 20 °C, max. 93%); however, at 15 °C germination was faster (after the first 20 days at 15 °C, max. 95%; at 20 °C, 73%). The highest germination rate was obtained after 8-9 months of storage (in vitro average, 94%; in vivo average, 83%). A mixture of peat + perlite + sand in equal parts was a suitable in vivo germination medium (93% germination) for C. alpinum.

THE CALIBRATION OF WET-SENSOR FOR VOLUMETRIC WATER CONTENT AND PORE WATER ELECTRICAL CONDUCTIVITY IN DIFFERENT HORTICULTURAL SUBSTRATES

A frequency domain dielectric sensor (WET ® ), which measures permittivity (e), temperature (T, °C) and bulk electrical conductivity (σ, dS/m) simultaneously in the same soil volume, was calibrated for the volumetric water content (θ, m 3 m -3 ) and the salinity of both pore water (σP) and water extract (σE) in different horticultural substrates: peat, pumice, perlite and mixtures (1:1, v:v) of peat and perlite or peat and pumice. The experiment was conducted under laboratory conditions over a T range between 22 and 28°C using plastic pots filled with each substrate, irrigated to fully container capacity with nutrient solutions of known concentrations and left to dry in air to θ ranging from approx. 0.20 and 0.50 m 3 m -3 . In order to avoid the development of significant gradients in substrate moisture and salinity, the pots did not host plants and the evaporation from the top surface was prevented by means of a plastic wrap. Pore water was collected by centrifugation, whereas water extract was obtained by means of 1 substrate: 2 water suspension method. A significant linear relationship was found between σE and σP, with the slope dependent on the type of substrate. θ calibration was faintly dependent on the nature of substrate and it was not affected by the salinity of irrigation water, at least in the peat-pumice mixture. In this substrate, the linear regression of σP against σ was markedly affected by θ and hence e.

Optimization of the treatment of carbon monoxide-polluted air in biofilters

This work is the first extensive study on the removal of carbon monoxide from polluted air in biofilters. It compares the performance of two packing materials, namely lava rock alone and a mixture of peat and lava rock. The results show that the biofilter packed with the mixture of peat and lava rock performed much better than the other one. The effect of operating conditions as, among others, the inlet concentration and the empty bed residence time (EBRT) were studied. A maximum elimination capacity of 33 g m −3 h −1 was obtained with the mixed packing with more than 85% removal efficiency at EBRT of 3 min or more. Somewhat lower performances were reached at shorter EBRT. The results presented here suggest that the mixture of lava rock and peat, subject to further optimization, offers potential for the biological removal of CO from polluted gas streams.

Effect of grass litter on seedling recruitment of the critically endangered Cistus heterophyllus in Spain

Cistus heterophyllus Desf. is an Iberian-north African endemic plant species with only one wild population left in Spain. A sowing experiment under controlled conditions was designed to assess both the seedling emergence rate and the growth fitness of C. heterophyllus on a litter layer of Brachypodium retusum (Pers.) Beau., which forms dense carpets around the remnant population of C. heterophyllus. In order to test the physical effects of B. retusum litter on Cistus seedling recruitment, six sowing treatments in pots were compared that combined three doses of litter (0, 0.6 and 1.1 kg m −2) and different physical locations of the seeds (above, below the litter layer or within a litter–peat mixture). B. retusum litter interfered with the seedling recruitment of C. heterophyllus, negatively affecting both seedling emergence and their early growth. Such an effect was more severe when the seeds were located above a 0.6 kg m −2 litter layer, although seedlings from seeds sown under the litter showed a growth reduction ranging from 58% to 100% compared to the no-litter treatment. A significant negative effect of the litter–peat mixture on the number of leaves, leaf size and number of branches of seedlings was also inferred. These data provide experimental evidence on the serious threat that B. retusum litter represents for the conservation and regeneration of the last population of C. heterophyllus in Spain.

COMPARISON BETWEEN OPEN AND CLOSED HYDROPONIC SYSTEMS ON LETTUCE YIELD

In the present study, lettuce production under the dosed and open hydroponic systems was investigated. The tested substrates were perlite : peat (4 : 1, v/v), sand : peat (4 : 1, v/v) and sand: peat : perlite (3 : 1 : 1, v/v/v) under different shading treatments control, i.e. (without shading), medium shading (40 % shade) and heavy shading (80 % shade). The current study was conducted with lettuce (Laciuca saliva). The total yield was higher with the closed systems compared with open ones. Perlite and perlite + peat mixture gave the highest yields among the tested substrates. The highest nutrient consumptions were obtained from perlite and perlite + peat (4 : 1. v/v). On the other hand, medium shading (40 % shade) gave the highest yield Compared with other treatments. Also, the results obtained indicated that in the closed system could save both water and nutrient consumption.

Relationships between humification and productivity in peat-based and peat-free growing media

Peat-based and peat-free (compost) materials were tested in a vegetable forcing experiment with Danubia green pepper (<I>Capsicum annuum</I> L.). Stability and quality of humic substances and the turnover of different nitrogen forms was determined in the studied media during the vegetation period. The main objective was to find how the degree of humification might influence the productivity of a crop under greenhouse conditions. The highest humus stability and humus stability coefficient values were detected in the green waste compost. Among different peat media, the low-moor peat was more humificated than the mixture of low-moor and high-moor peat. When the medium is more humificated it has a larger mobile nitrogen reserve. However, the structure stability decreases with the increasing humification. The mixture of two types of peat had the most favourable effect on nitrogen supply and the yield of pepper was the highest when grown on this medium. The nitrogen supplying ability of the examined compost was excellent but its structure stability deteriorated during the growing season.

Growth of lulo (Solanum quitoense Lam.) plants affected by salinity and substrate

The effects of 0, 30 and 60 mM NaCl and substrates (red peat, sand or 3:1:1 [w/w] mixture of peat, sand, or soil) on vegetative growth of lulo, an Andean fruit species, during 12 weeks were studied. The experiment was carried out by using 2000 cm³ of polypropylene plastic pots under greenhouse conditions. Plant height, number of leaves and nodes, leaf area, total plant dry matter (DM), and shoot/root ratio were evaluated. With the increase of salt concentration, the plant height, the number of leaves and nodes, the leaf areas and plant dry mass DM decreased, whereas shoot/root ratio increased. Sand grown lulo plants were most affected by salinity and presented total mortality at 60 mM NaCl. On the other hand, plants held either in peat or in substrate mixture developed larger height, greater leaf and node numbers, higher leaf area and dry matter content. Shoot/root ratio in control (soil) and sand-grown plants (30 mM NaCl) was lower.

Rapid multiplication of Polyscias filicifolia by secondary somatic embryogenesis

Efficient plant regeneration through somatic embryogenesis was achieved in Polyscias filicifolia. Embryogenic calluses were induced on Murashige and Skoog (MS) basal medium supplemented with 0.5 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.0 mg l−1 benzylaminopurine (BAP; type I callus) and on MS medium with 2.0 mg l−1 2,4-D and 0.01 mg l−1 kinetin (type II callus) from leaf explants of a 2-yr-old plant. Primary somatic embryos (PSEs) developed after four passages of suspension culture established from embryogenic callus when cultured in liquid half-strength MS medium (1/2 MS) without growth regulators. PSEs in the cotyledonary stage were multiplied by adventitious embryogenesis. Single secondary somatic embryos (SSEs) or their clusters developed at the base of PSE hypocotyls and regenerated into plantlets in a one-step process on plant growth regulator-free 1/2 MS medium. Low sucrose concentration of 15 g l−1 promoted development of normal SSEs. All SSEs regenerated into single, well-rooted plantlets on a Nitsch and Nitsch medium supplemented with 0.5 mg l−1 kinetin, 0.1 mg l−1 indole-3-butyric acid, and 10 mg l−1 adenine sulfate. Subsequent two subculture cycles on the same medium were necessary to obtain plantlets sufficiency developed to allow successful transfer to the soil. Rooted plantlets were established in a peat mixture with 90% survival, with the plants showing normal morphological characteristics.

Reduction of trichloroethylene and nitrate by zero-valent iron with peat

The feasibility of using zero-valent iron (ZVI) and peat mixture as in situ barriers for contaminated sediments and groundwater was investigated. Trichloroethylene (TCE) and nitrate (NO3 −), redox sensitive contaminants were reduced by ZVI and peat soil mixture under anaerobic condition. Peat was used to support the sorption of TCE, microbial activity for biodegradation of TCE and denitrification while TCE and nitrate were reduced by ZVI. Decreases in TCE concentrations were mainly due to ZVI, while peat supported denitrifying microbes and further affected the sorption of TCE. Due to the competition of electrons, nitrate reduction was inhibited by TCE, while TCE reduction was not affected by nitrate. From the results of peat and sterilized peat, it can be concluded that peat was involved in both dechlorination and denitrification but biological reduction of TCE was negligible compared to that of nitrate. The results from hydrogen and methane gas analyses confirmed that hydrogen utilization by microbes and methanogenic process had occurred in the ZVI-peat system. Even though effect of the peat on TCE reduction were quantitatively small, ZVI and peat contributed to the removal of TCE and nitrate independently. The 16S rRNA analysis revealed that viable bacterial diversity was narrow and the most frequently observed genera were Bacillus and Staphylococcus spp.

Column studies aiming at identification of suitable filter materials for pollutant removal from landfill leachate

Landfill leachate contains a complex mixture of inorganic and organic pollutants, which need to be removed before they pollute the environment. Different filter media (peat mixed with either carbon-containing ash, polyurethane waste, or wood pellets) were investigated with respect to their possibility to simultaneously and at low initial concentrations remove metals, polar and non-polar organic compounds. The mixture of peat and carbon-containing ash was found to be the best medium. Reduction in leachate of phenolic substances was 96%, of PBDEs was over 98%, of DOC 40% and of important metals as Cu, Pb and Sn 60%, 90% and 93%, respectively.

Chromium Fate in Constructed Wetlands Treating Tannery Wastewaters

Nine experimental wetlands were built to determine chromium partitioning inside systems treating tannery wastewaters. Results showed 5-day biochemical oxygen demand and chromium removals of 95 to 99% and 90 to 99%, respectively. The majority of chromium was found in association with media (96 to 98%), followed by effluents (2.9 to 3.9%), and the least was found in plant parts (0.1%). Chemical speciation modeling of solutions and scanning electron microscope analysis suggest two potential chromium removal mechanisms--sorption/coprecipitation with iron hydroxides or oxyhydroxides and biomass sorption. The release of the majority of chromium in the iron- and organic-bound phases during sequential extractions supports the proposed dominant removal mechanisms. The use of a mixture of peat and gravel resulted in lower removal efficiencies and stronger partitioning in organic phases during sequential extractions. Chromium was efficiently removed by wetlands, retained through chemical and biological processes. Future research will focus on further exploring removal mechanisms and proposing management strategies for the chromium-containing wetland media.

GROWING MEDIA IN FRENCH HORTICULTURE

Our paper deals with the wise use of peat and substrates in France, from a horticultural point of view. Modern horticultural substrates have been used for many years now to grow potted plants, nursery plants in containers, bedding plants, cut flowers and vegetables. The substrate market is considerable at this time, at both the professional and home gardening level. Peat and peat mixtures represent the biggest part of substrates. However, France is not self-sufficient in terms of horticultural peat production. As a result, different products exist as an alternative to peat: composted bark, coir and wood fibres, green waste, expanded materials, mineral wool, etc. This paper discusses some major strategies concerning substrates, taking current trends in citizens' needs in modern society into account, including the social demand for an ecological approach towards a more environmentally-friendly agriculture, combined with effective technical and economic performance. Peat and peatland preservation as well as the contribution of horticulture to the ecological re-use of solid waste must be dealt with within the framework of horticultural substrates.

Use of stable nitrogen isotope fractionation to estimate denitrification in small constructed wetlands treating agricultural runoff

Constructed wetlands (CWs) in the agricultural landscape reduce non-point source pollution through removal of nutrients and particles. The objective of this study was to evaluate if measurements of natural abundance of 15NO 3 − can be used to determine the fate of NO 3 − in different types of small CWs treating agricultural runoff. Nitrogen removal was studied in wetland trenches filled with different filter materials (T1 — sand and gravel; T3 — mixture of peat, shell sand and light-weight aggregates; T8 — barley straw) and a trench formed as a shallow pond (T4). The removal was highest during summer and lowest during autumn and winter. Trench T8 had the highest N removal during summer. Measurements of the natural abundance of 15N in NO 3 − showed that denitrification was not significant during autumn/winter, while it was present in all trenches during summer, but only important for nitrogen removal in trench T8. The 15N enrichment factors of NO 3 − in this study ranged from − 2.5 to − 5.9‰ (T3 and T8, summer), thus smaller than enrichment factors found in laboratory tests of isotope discrimination in denitrification, but similar to factors found for denitrification in groundwater and a large CW. The low enrichment factors compared to laboratory studies was attributed to assimilation in plants/microbes as well as diffusion effect. Based on a modified version of the method presented by Lund et al. [Lund LJ, Horne AJ, Williams AE, Estimating denitrification in a large constructed wetland using stable nitrogen isotope ratios. Ecol Engineer 2000; 14: 67–76], denitrification and assimilation were estimated to account for 53 to 99 and 1 to 47%, respectively, of the total N removal during summer. This method is, however, based on a number of assumptions, and there is thus a need for a better knowledge of the effect of plant uptake, microbial assimilation as well as nitrification on N isotopic fractionation before this method can be used to evaluate the contribution of dinitrification in CWs.

Bacillus cereus in Free-Stall Bedding

To increase the understanding of how different factors affect the bacterial growth in deep sawdust beds for dairy cattle, the microbiological status of Bacillus cereus and coliforms in deep sawdust-bedded free stalls was investigated over two 14-d periods on one farm. High counts of B. cereus and coliforms were found in the entire beds. On average, 4.1 log10B. cereus spores, 5.5 log10B. cereus, and 6.7 log10 coliforms per gram of bedding could be found in the upper layers of the sawdust likely to be in contact with the cows’ udders. The highest counts of B. cereus spores, B. cereus, and coliforms were found in the bedding before fresh bedding was added, and the lowest immediately afterwards. Different factors of importance for the growth of B. cereus in the bedding material were explored in laboratory tests. These were found to be the type of bedding, pH, and the type and availability of nutrients. Alternative bedding material such as peat and mixtures of peat and sawdust inhibited the bacterial growth of B. cereus. The extent of growth of B. cereus in the sawdust was increased in a dose-dependent manner by the availability of feces. Urine added to different bedding material raised the pH and also led to bacterial growth of B. cereus in the peat. In sawdust, a dry matter content greater than 70% was needed to lower the water activity to 0.95, which is needed to inhibit the growth of B. cereus. In an attempt to reduce the bacterial growth of B. cereus and coliforms in deep sawdust beds on the farm, the effect of giving bedding daily or a full replacement of the beds was studied. The spore count of B. cereus in the back part of the free stalls before fresh bedding was added was 0.9 log units lower in stalls given daily bedding than in stalls given bedding twice weekly. No effect on coliform counts was found. Replacement of the entire sawdust bedding had an effect for a short period, but by 1 to 2 mo after replacement, the counts of B. cereus spores in the beds had increased about 2 log units and were as high as they were before bed replacement. Therefore, free-stall management could, to a limited extent, reduce the content of B. cereus spores in the beds by daily bedding and entire bed replacement.

Growing Picea abies container seedlings in peat and composted forest-nursery waste mixtures for forest regeneration

The suitability of using composted forest-nursery waste as a component in growing medium was studied. Norway spruce [Picea abies (L.) Karst.] seedlings were grown in containers filled with sphagnum peat (100P), forest-nursery waste compost (100C) and in peat mixtures containing 25 or 50% compost by volume (75P25C and 50P50C, respectively). Morphological and chemical characteristics of the seedlings and the water and nutrient contents of the growing media were studied during 22 weeks of nursery cultivation. The seedlings were outplanted the following spring, and the survival and growth were followed for 3 years. Compost additions decreased seedling height, diameter and shoot dry mass, but root dry mass was the same in 100P and 75P25C after nursery cultivation. Foliar nutrient concentrations were optimal in all the seedlings, although foliar nitrogen content was lower the greater the proportion of compost in the medium. Compost additions did not affect the root-egress potential tested before outplanting. The 100P seedlings grew significantly more than the other seedlings during the first summer at the forest site. Thereafter, compost additions did not affect growth, but the final height and diameter were still the lowest in 100C. The results suggest that forest-nursery waste compost has potential to be used as a component of peat-based growing medium. However, specially adjusted nursery-cultivation practices need to be used for compost-containing media.

Influence of Temperature on Survival and Conjugative Transfer of Multiple Antibiotic-Resistant Plasmids in Chicken Manure and Compost Microcosms

The aim of this study was to determine if mobile plasmids carrying antibiotic-resistant genes could survive and be transferred in chicken manure maintained under conditions similar to those found in commercial cage layer operations and during composting. Escherichia coli J5 harboring a self-transmissible plasmid (RP4) and E. coli C600 harboring a mobile plasmid (pIE723) were used as plasmid donors; E. coli CV601 was used as a plasmid recipient. At 23°C both plasmids were transferred to E. coli CV601 in chicken manure and in compost microcosms that consisted of a mixture of chicken manure and peat. The transfer frequencies ranged from 8.1 × 10−5 to 2.4 × 10−3 per donor cell in manure and from 2.4 × 10−5 to 5.5 × 10−4 per donor cell in compost microcosms. After 45 d of incubation at 23°C, RP4, but not pIE723, was recovered by an exogenous isolation method although their E. coli hosts were not cultured from the microcosms. However, when the temperatures of the compost microcosms were elevated to 50°C or above, neither the plasmids nor their E. coli hosts could be detected. The results suggested that composting of chicken manure at high temperatures could help prevent the spread of antibiotic-resistant genes via plasmids in the environment.