Phosphorus Leaching Research Articles

The role of the understory in litter DOC and nutrient leaching in boreal forests

Dissolved organic carbon (DOC) derived from plant litter plays an important role in the ecosystem carbon balance and soil biogeochemistry. However, in boreal coniferous forests no integrated understanding exists of how understory vegetation contributes to litter leaching of DOC, nitrogen (N) and phosphorus (P) with different bioavailability at the forest stand level. We characterized water extractable leachates from fresh and decayed litter of dominant canopy and understory sources in a boreal coniferous forest, in order to explore the contribution of understory vegetation as a source of both total and bioavailable forms of DOC, N and P. Recently produced litter from deciduous species (including Vaccinium myrtillus) yielded the highest amounts of DOC. However, this leaching potential decreased exponentially with mass loss through litter decay. The DOC lability generally showed little interspecific variation, although wood derived DOC was more recalcitrant. Lability decreased progressively with litter aging. Water extractable nutrients increased proportionally with DOC, and roughly a quarter (N) or half (P) had directly bioavailable inorganic forms. Scaled to annual litterfall at the forest stand, understory vegetation contributed ~ 80% of the water extractable DOC and nutrients from fresh litter, with > 60% coming from Vaccinium myrtillus alone. However, as litter decomposes, the data suggest a lower leaching potential is maintained with a larger contribution from needle, wood and moss litter. Our study shows that understory vegetation, especially V. myrtillus, is a key driver of litter DOC and nutrient leaching in boreal coniferous forests.

Riparian land-use systems impact soil microbial communities and nitrous oxide emissions in an agro-ecosystem

Riparian buffer systems (RBS) are considered a best management practice (BMP) in agricultural landscapes to intercept soil nitrogen (N) and phosphorus (P) leaching and surface runoff into aquatic ecosystems. However, these environmental benefits could be offset by increased greenhouse gas (GHG) emissions, including nitrous oxide (N2O). The main sources of N2O in soil are linked to processes which are mediated by soil microbial communities. These microorganisms play crucial roles in N-cycling and in the reduction of nitrate to N2, and N2O gases. This study was conducted to determine the abundance and diversity of microbial communities and functional genes associated with N-cycling and their influence on N2O emissions in different riparian land-use: undisturbed natural forest (UNF), rehabilitated site (RH), grass buffer (GRB), and an adjacent agricultural land (AGR). Soil was sampled concurrently with N2O emissions on July 13, 2017. DNA was extracted and used to target key N-cycling genes for N-fixation (nifH), nitrification: (amoA), and denitrification (nirS, nirK, and nosZ) via quantitative PCR, and for high throughput sequencing of total bacterial and fungal communities. Non-metric multidimensional scaling (NMDS) was used to examine microbial community composition and indicated significant differences in bacterial (p < 0.001) and fungal (p < 0.0085) communities between sites. Bacterial abundance differed significantly (p = 0.0005) between RBS and AGR sites with the highest populations occurring in the UNF (2.1 × 1010 copies g−1 dry soil), and lowest in AGR (5.3 × 109 copies g−1 dry soil). However, the AGR site had the highest ammonia-oxidizing bacteria (AOB) abundance, indicating that nitrification is highest at this site. The abundance of the nosZ gene was highest in RH and GRB demonstrating the capacity for complete denitrification at these sites, lowering measured N2O. These results suggest N-cycling microbial community dynamics differ among RBS and are influencing N2O emissions in the sites investigated.

Short-term impacts of biochar, tillage practices, and irrigation systems on nitrate and phosphorus concentrations in subsurface drainage water.

Leaching of nitrogen (N) and phosphorus (P) from agricultural lands can cause serious environmental problems such as eutrophication. The objective of this study was to investigate the impacts of biochar application, tillage practices, and irrigation systems on nitrate and dissolved phosphorus (DP) concentrations in subsurface drainage water and grain yield of winter wheat using a strip-split plot design with 3 replications. Irrigation at three different levels (flood (Ifl), furrow (Ifu), and sprinkler (Is) systems) considered as main factor, tillage at two levels (reduced tillage (Tr) and conventional systems (Tc)) as subplot factor, and bagasse biochar at two levels (without biochar (B0) and 20tonha-1 biochar (B1)) as sub-subplot factor. Polyvinyl chloride (PVC) standpipes were used in each sub-subplot to collect leachate water at 100-cm depth. The results indicated that irrigation had significant effects on yield, collected water volume (CWV), nitrate, and DP concentrations (P < 0.01). Interaction of tillage and irrigation was significant for grain yield (P < 0.05). Biochar application only caused a significant decrease in nitrate concentration under sprinkler irrigation (P< 0.05), while no significant impact was observed under flood and furrow irrigation systems. Under sprinkler irrigation, the total nitrate collected in the PVC standpipes decreased by 37.51 and 34.29% compared with flood and furrow irrigations, respectively. Biochar application reduced the total nitrate collected by 16.84%, while difference among tillage treatments was negligible (4.51%). The total DP collected under sprinkler irrigation was lower in comparison with flood and furrow irrigations by 42.24 and 38.76%, respectively. Biochar application reduced the total DP collected by 10.84%, while reduced tillage increased the total DP collected by 8.90% compared with the conventional tillage.

Effect of heat processing on the nutrient composition, colour, and volatile odour compounds of the long-horned grasshopper Ruspolia differens serville.

Heat processing is commonly used to prepare edible insects for consumption. This study aimed at determining the effect of boiling and subsequent oven roasting on Ruspolia differens' nutrient composition, colour and odor compounds. Boiling leads to: a significant increase in protein and decrease in fat content on a dry matter basis; a minimal influence on its amino and fatty acids profile; a significant reduction in its ash content due to leaching of phosphorus, potassium and sodium; a significant increase in iron, zinc, copper, manganese and calcium content; and a fivefold reduction in the amount of vitamin B12. Roasting leads to a relative increase in the amount of calcium and trace mineral elements but doesn't affect other nutrients. Roasting results into a more uniform colour intensity when green and brown polymorphs are roasted together. Lipid oxidation is responsible for the colour and aroma of heat processed R. differens.

Activated dolomite phosphate rock fertilizers to reduce leaching of phosphorus and trace metals as compared to superphosphate

Use of water-soluble phosphorus (P) fertilizers such as superphosphates (SP) has been increasingly concerned due to the loss of P and trace metals such as cadmium (Cd) into the environment. Activated phosphate rock holds promising as an alternate due to non-destructive and slow release nature. The objective of this study was to assess the leaching potential of P and trace metals from newly developed activated dolomite phosphate rock (HA-DPR and SLS-DPR), as compared to water-soluble fertilizers, including superphosphate (SP), diammonium phosphate (DAP) and original dolomite phosphate rock (DPR). Two representative agricultural soils (Alfisol and Spodosol soil) were sampled at the 0–20 cm depth from two farms for the column leaching experiments. Seven leachings were conducted at day 1, 3, 7, 14, 21, 28, and 56, respectively, and a total of 1050 mL of deionized water (equivalent to half year's rainfall in the Indian River area) was applied for leaching. Leachates were collected from each leaching event and analyzed for water-soluble P and metals. Activated DPR application led to an increase in soil pH by 1.4–1.7 units, whereas SP resulted in a decrease in soil pH by 0.4–1.6 units. P leaching from activated DPR were 33–61 times less than that from SP or DAP. HA-DPR and SLS-DPR treatments reduced cumulative trace metals in leachate by 1.3–12.3 times for the Alfisol soil, and 1.4 to 8.4 times for the Spodosol soil, respectively. These results indicate that activated DPR fertilizers are more environmentally friendly than water-soluble fertilizers.

Preliminary Study on the Potential Use of Fly Ash as a Ventilated Improved Pit Latrine Additive

This study describes the results of a series of laboratory experiments on aimed at developing of a protocol for the use of fly ash as a pit additive in the ventilated improved pit latrines (VIPs) in South Africa. Model VIP vaults were prepared in the laboratory and filled with synthetic faecal sludge; and dosed with fly ash in amounts ranging from 5 to 20 % (w/w). The maximum leachable chemical oxygen demand (COD) accounted for 3.2 % of the total organic matter, while the maximum leachable ammonium accounted for 1.4 % of the leachable ammonium present in the synthetic faecal sludge. All phosphate in the synthetic faecal material was leachable. Mixing of the 20 % dose of fly ash into the synthetic faecal sludge resulted a minimum 98.9 % reduction (or about two log units) in the faecal coliform concentration after 28 days of incubation. As a result, addition of fly ash can decrease microbial threats to public and environmental health threats from the VIP faecal wastes, but can cause environmental contamination with phosphate. The fly ash dose and the duration of the faecal sludge treatment require further optimisation. Relationship between the chemical composition of the fly ash used as an additive to stabilise the VIP faecal sludge and the leaching of phosphorus from the sludge will also have to be investigated further.

EFFECTS OF CONTROLLED DRAINAGE ON SOIL WATER REGIME AND QUALITY IN LITHUANIA

Lithuania remains one of the most extensively drained of the Baltic and Nordiccountries. The overall drained area (ditches plus tile drains) totalled 87% of theagricultural land area. Many nutrients from soil are leached through drainageresulting in polluting streams (drain flow receivers) water. Drain flow is treated asa major determinant of water quality. Therefore, the reduction of nutrients enteringthe drains is very important. Controlled drainage conception, when the outflowheight is increased at the mouth, helps reduce drainage runoff and partially purifywater. The aim of the research was to establish controlled drainage influence on thesoil moisture regime, nitrogen and phosphorus leaching. Investigations werecarried out in sandy loam and loam soils in the Middle Lithuanian Lowland. Basedon studies, several tendencies were observed: when drainage outflow began, theamount of soil moisture in subsoil (50-80 cm layer of the soil) of controlleddrainage plot was higher than in the conventional drainage plot, and highermoisture supplies stayed for a longer period of time. Controlled drainage had nodirect impact on phosphorus and nitrogen concentrations but they were influencedby the leaching quantities of plant usable nutrients. The reason that in many caseslower nitrate nitrogen (54% of all measurements) and phosphorus concentrations(77% of all measurements) were found in the conventional system rather than inthe controlled drainage might be connected to the fact that the latter area containedpredominantly lighter textured soils (sandy loam) making it easier to wash awaythe nutrients unused by plant.

Phosphorus and Nitrogen Adsorption by Clinoptilolite Zeolite Coated with Iron-Oxide

ABSTRACTClinoptilolite zeolite coated with hydrous ferric oxide (FeZeo) may improve nutrient retention when blended into sand-based root zones. The objective of this study was to evaluate the effects of nutrient-charged FeZeo on nitrogen (N) and phosphorus (P) leaching and on growth of creeping bentgrass (Agrostis palustris Huds.). FeZeo was pre-loaded with 255 mg kg−1 N and 224 mg kg−1 P using a water-soluble fertilizer. Then, root zone mixes (RZM) containing 0, 5, 10, and 20% fertilizer-loaded FeZeo were packed into lysimeters and seeded with creeping bentgrass at a rate of 49 kg ha−1. RZMs with 20% FeZeo received no additional fertilization whereas those containing 0, 5, and 10% FeZeo received four additional fertilizer applications during the next 8 months so that the cumulative N and P rates for every lysimeter were equivalent to 149 kg ha−1 and 131 kg ha−1, respectively. Lysimeters were irrigated every 2 to 3 days and leachate was collected and analyzed. Compared to putting green sand, the 5, 10 and 20% FeZeo treatments reduced the quantity of leached P by 96.2%, 91.3%, and 90.3%, and the quantity of leached N by 88.6%, 82.7% and 76.7%, respectively. Results suggest that pre-fertilized FeZeo applied to sand-based root zone mixes at 5 to 10% can significantly reduce nutrient leaching while maintaining acceptable plant growth, but higher rates of FeZeo can reduce plant growth. An alternative use for higher rates of FeZeo might include a filtering material for agricultural tile drainage.Abbreviations: cation exchange capacity (CEC), electrical conductivity (EC), iron-oxide coated clinoptilolite zeolite FeZeo, nitrogen (N), RZM, root zone mix

Microbial Biomass Responses to Soil Drying-Rewetting and Phosphorus Leaching

Soil drying-rewetting is known to enhance soil phosphorus leaching, which in part is due to osmotic shock and lysis of microbial cells upon rewetting. However, it is not entirely clear how this may be influenced by the intensity and duration of soil drying. We hypothesized that the intensity and duration of soil drying play important roles in determining the extent of dissolved reactive phosphorus (DRP) leaching resulting from microbial biomass mortality. To test this hypothesis soil sub-samples of a loamy grassland soil were dried (30C or 40C for 2-days or 14-days), rewetted, and the leachate was analysed for DRP. Soil drying at 30C for 2-days and 14-days resulted in leachate DRP concentrations which were 71% and 271% respectively higher than those in leachate from a control moist counterpart. Relatively greater DRP leaching losses occurred from the soil dried at 40C for 2-days and 14-days (143% and 300% respectively). To determine the contribution of the microbial biomass to the DRP in leachate, soil sub-samples were fumigated with chloroform either before or after drying (30C or 40C for 2-days or 14-days). All soil treatments were then either leached with water and analysed for DRP or extracted with 0.5M sodium bicarbonate solution and analysed for microbial biomass phosphorus. Fumigating soil samples before or after drying reduced microbial biomass phosphorus. However, the effect of chloroform fumigation was more pronounced in terms of microbial biomass reduction in the DF (drying followed by fumigation) treatment. Moreover, results revealed that in the DF treatment, soils dried at 30C for 2-days and 14-days had 22% and 13% respectively more microbial biomass phosphorus than their counterparts dried at 40C for 2-days and 14-days respectively. These results suggest that soil drying at higher intensity and for prolonged periods significantly (p<0.05) affect microbial biomass and subsequently increases soil phosphorus leaching following rewetting, due to enhanced contributions from the microbial biomass. These findings, however, need to be verified over a range of soil types under natural field conditions to better assess soil drying-rewetting effects on nutrient leaching.

Control Measure Effects on the Effluent Quality from Extensive Green Roofs Based on Stabilized Sludge Recycling

Substrate type is an important factor affecting the quality of water deriving from rainfall onto extensively green roofed areas. Here, stabilized sludge was used as the main nutrient component of the substrate combined with biochar and a dual-substrate structure. Five green roof pilot facilities were constructed, and the effect of control measures on effluent quality was analyzed. The results showed that the stabilized sludge dosage was 3%, and the annual average mass concentrations of total nitrogen (TN) and nitrate nitrogen (NO3--N) were 3.27 mg·L-1 and 1.61 mg·L-1. The use of stabilized sludge as a nutrient component under real rainfall and temperature conditions in Shanghai did not cause significant leaching of TN and NO3--N. In order to further improve the quality of the effluent, biochar was used as an amendment measure. As a result, the concentrations of TN and NO3--N in the effluent were decreased to 2.16 mg·L-1 and 1.38 mg·L-1, respectively. Using an adsorption layer of pumice can alleviate the leaching of total phosphorus (TP) and chemical oxygen demand (COD). For the total nitrogen budget of each pilot facility, the retained TN was about 55% of the original TN after one year of operation. Thus, stabilized sludge could be used as a nutrient substrate to meet the long-term requirements of plants. In the substrate with biochar, the retained TN in the substrate and the NO3--N concentration in the effluent was decreased, which was related to the mineralization of organics during dry periods and the enhancement of denitrification during rainfall periods. Stabilized sludge was not a polluting source of N but was a source of P. Using biochar and a dual-substrate structure can effectively reduce the TN and COD load of the tested green roof facilities.

Phosphorus recovery from sewage sludge ash with bioleaching and electrodialysis

Phosphorus is an essential element for all living organisms and for plants. However, phosphate rock, which is the main source of phosphorus, is limited and thus it must be recovered from secondary sources like sewage sludge ash (SSA). SSA is one of the most promising secondary sources because it contains considerable amounts of phosphorus. The drawback of SSA as a secondary source is the presence of heavy metals along with phosphorus. In this study, a bioleaching process was applied to solubilize the phosphorus more economically, thus bioleaching bacteria was used to obtain acidic conditions for phosphorus leaching. For this purpose, batch bioleaching experiments were carried out with Sulfur oxidizing bacteria (SOB) to optimize the process in terms of phosphorus dissolution. Experiments were conducted with different amounts of ash, inoculum volumes, and sulfur concentrations. Because the application of the bioleaching process leads to solubilization of heavy metals beside phosphorus, an electrodialysis process was used to separate phosphorus from heavy metals. Electrodialysis experiments were performed in a 3 compartment electrodialysis reactor with gold coated copper electrodes. The maximum phosphorus bioleaching was obtained with 2 g of ash, 40% inoculum, and 10 g.l-1 elemental sulfur. Electrodialysis studies with gold coated copper electrodes lasted for 14 days and 24.6% of the phosphorus was transported to the anode.

Effects of iron, calcium, and organic matter on phosphorus behavior in fluvo-aquic soil: farmland investigation and aging experiments

Excessive fertilization has led to a high risk of phosphorus (P) leaching and related problems in the North China Plain, where the most typical cropland soil is fluvo-aquic soil. The main factors controlling environmental P behavior and the acting time sequence of these factors in soil after long-term P fertilizer application have not been well recognized. A clear understanding is essential for effective P management. Effects of Fe minerals, calcium carbonate, and organic matter (OM) on P immobilization in fluvo-aquic soil were studied systematically through farmland investigation and aging experiments. Phosphorus associated with Ca was the primary fraction in fluvo-aquic soil. Even though there was no significant correlation between the total contents of P and Ca in soils, formation of P-Ca phases facilitated by Ca2+ in soil solution was a mechanism of P retention when soil received excess P fertilizer. Positive correlations between the contents of P and Fe and total organic carbon (TOC) indicate that Fe minerals and OM have significant effects on P immobilization. Through the aging experiments, P was found to primarily adsorb on goethite and gradually forms Ca-P compounds. Organic fertilizer caused P release and inhibition of P adsorption in the initial stages; however, OM derived from organic fertilizer might facilitate P immobilization in the long term through the formation of a P-Ca-OM complex. Although superfluous application of P fertilizers leads to the gradual formation of Ca-P in fluvo-aquic soils, there is still a risk of P loss because P is not immediately adsorbed by Fe minerals. Moreover, application of organic fertilizers increases the risk of P loss. These results provide an important scientific basis for initiating P management policies for fluvo-aquic soils.

Sequential Bioleaching of Phosphorus and Uranium

Phosphorus and uranium are both vital elements for society. In recent decades, fears have arisen about the future availability of low-cost phosphorus and uranium. This has resulted in pressure to de-centralize production of both elements by utilizing lower-grade or complex deposits. The research presented here focused on phosphorus-containing apatite ores with uranium impurities; in order to separate uranium by selective and sequential bioleaching before phosphorus leaching. This would create an alternative process route for solvent-extraction, used to remove/recover uranium from the phosphorus acid product of apatite H2SO4 wet process. In this work, it was seen that the used fluorapatite ore required 24 h leaching at pH 1 by H2SO4 to result in 100% leaching yield for phosphorus. As this ore did not contain much uranium, an artificial fluorapatite-uranium ore was prepared by mixing standard uranium ore and fluorapatite. The research with this ore showed that 89% of uranium dissolved in 3 days at pH &gt; 2 and leaching was improved by applying Fe3+ oxidant. In these conditions only 4% of phosphorus was leached. By prolonged (28 days) leaching 95% uranium yield was reached. According to the experiments, the iron in the uranium leach solution would be mainly Fe3+, which allows the use of H2O2 for uranium recovery and then direct use of spent leachate for another uranium leaching cycle. After the dissolution of uranium, 90% of phosphorus was dissolved by decreasing the pH to 1.3. This was done by bioleaching, by utilizing biogenic sulfur oxidation to sulfuric acid.

Rice plant growth and nutrient leaching under different patterns of split chemical fertilization on sandy soil using a pot

Savannakhet Province has 25% of the total lowland rice cultivation area of Lao People’s Democratic Republic (Laos). However, most of the fields are rainfed, with highly permeable sandy soil, which has low water and nutrient availability. In such sandy rainfed fields, high leaching loss of nutrients from applied fertilizer is expected, and rice yield is also decreased. Therefore, an efficient fertilization scheme is required to improve rice yield in this area. We conducted a pot experiment to evaluate rice plant growth and nutrient leaching under different split chemical fertilizer application patterns. Sandy soil collected in a village in Savannakhet Province was placed in test pots. Four treatments, viz., standard fertilization (control: C, three splits), subdivided fertilization (SF, six splits), intensive fertilization (IF, once at the time of transplanting), and no fertilizer (NF) were tested. Irrigation was done every 3 days during the initial 3 months and every 10 days in the final month with reference to the rainfall pattern recorded in the rainy season of 2016. Although the maximum number of tillers in C and IF was higher than that of SF, they ultimately decreased to a smaller number than that of SF. The yield of SF was higher than that of the other three treatments. NF showed the lowest growth and yield. The six-split fertilization might supplement nitrogen (N) at the late growing stage. IF showed the largest N leaching loss among treatments. Because of low phosphorus (P) leaching loss, split P fertilization was ineffective. K leaching was completed by 39 days after transplanting, suggesting that all of the K applied by fertilizer and irrigation was consumed by rice plants or lost through leaching before panicle initiation. The proposed split fertilization is advantageous in that it supplies N for panicle initiation and maturing stages in sandy paddy fields, but the timing and amount of P application must be considered.

Obliteration of phosphorus deficiency in plants by microbial interceded approach

Phosphorus plays an indispensable part in keeping up soil richness and securing global sustenance production, however, its chief proportions remain interlocked in various insoluble forms of Ca, Fe and Al ion precipitates that cannot be taken by the plants proficiently. This prompts to an indiscriminate application of phosphatic chemical fertilizers to the crop field which has led to substantial pollution of soil, air, water and deleterious effects on soil health due to leaching and run-off of phosphorus into soil and water table. Microorganisms such as bacteria, fungi, actinobacteria, and cyanobacteria play a crucial role in mobilizing inorganic and organic P in the soil and simultaneously increases P uptake by the plant. In the present review, endeavors have been made to emphasize on the occurrence, mechanism, the role of phosphate solubilizing bacteria in solubilization of fixed phosphorus and genetics of phosphate solubilizing microorganisms.

Stability and phosphorus leaching of tilapia feed in water

ABSTRACT: The present research aimed to investigate the stabil¬¬ity of pellets and phosphorus leaching of diets formulated for juveniles of Nile tilapia (Oreochromis niloticus), with different sources of phosphorus and different exposure times in water. Six diets were elaborated by varying the source of phosphorus (1 ‒ dicalcium phosphate (DP); 2 ‒ meat and bone meal (MBM); 3 ‒ poultry meal (PM); 4 ‒ anchovy meal (AM); 5 ‒ tilapia filleting industrial meal (TM); 6 ‒ calcined bone meal (CBM)) and, then, were submitted to four exposure times in water (5, 10, 15 and 20 minutes), with three replicates. Thus, 72 aquariums of 30‒liters were used, each being an experimental unit. All diets were evaluated for electrical conductivity of water, turgidity of pellets, mineral matter leaching, flotation of pellets, and total phosphorus leaching. Only turgidity and flotation of pellets varied with the different sources of phosphorus in the diets. The MBM diet had the highest turgidity of pellets. The PM, AM, and CBM diets had the highest flotation of pellets. The total phosphorus leaching had a linear effect with the increase of the exposure time, showing a greater release of phosphorus in the water with increase of exposure time. Data showed that PM, AM, and CBM diets had less potential impact on the aquatic environment. Conversely, the TM diet has greater polluting potential. These results showed that diets formulated with different sources of phosphorus exhibit distinct actions in the water, providing different effects on the fish culture environment.

Effects of continuous use of livestock manure on phosphorus leaching and phosphorus forms in sandy upland field

Effects of continuous use of livestock manure on phosphorus leaching and phosphorus forms in sandy upland field

Sustainable utilization of a recovered struvite/diatomite compound for lead immobilization in contaminated soil: potential, mechanism, efficiency, and risk assessment.

A waste-struvite/diatomite compound (MAP@Dia) recovered from nutrient-rich wastewater treated by MgO-modified diatomite (MgO@Dia) was provided to immobilize lead in aqueous solution and contaminated soil. The mechanism and effectiveness of lead immobilization was investigated, and the pHstat leaching test and fixed-bed column experiments were carried out to assess the risk of MAP@Dia reuse for lead immobilization. The results showed that MAP@Dia were effective in immobilizing lead in aqueous solution with adsorption capacity of 832.47-946.50mg/g. The main mechanism of Pb immobilization by MAP@Dia could be contributed by surface complexation and dissolution of struvite followed by precipitation of hydroxypyromorphite Pb10(PO4)6(OH)2. Lead(II) concentration reduced from 269.61 to 78.26mg/kg, and residual lead(II) increased to 53.14% in contaminated soil when the MAP@Dia application rate was 5%. The increased neutralization capacity (ANC) and lower lead extraction yields in pHstat leaching test in amended soil suggested 5 times of buffering capacity against potential acidic stresses and delayed triggering of "chemical time bombs." The results of column studies demonstrated that amendment with MAP@Dia could reduce the risk of lead and phosphorus (P) leaching. This study revealed that MAP@Dia could provide an effective solution for both P recycling and lead immobilization in contaminated soil.

A laboratory study to determine the use of polluted river sediment as a substrate for extensive green roofs

In this study, laboratory-scale green (e.g. living) roof platforms were established to assess the potential use of polluted river sediment in their substrate mixture. The mean runoff retention of the green roof platforms, which contained peat and/or river sediment, after 11 artificial rainfall events was >72%, significantly higher than traditional roofs. However, green roof platforms that had been filled with peat soil showed chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) leaching. Green roofs that had used river sediment showed good leaching control for COD, TN and TP. The cumulative leaching masses from the green roofs contained 30% (COD), 42% (TN) and 47% (TP) as much as the total leaching mass from traditional roofs, and the Cu, Zn, Cd and Pb leaching risk from green roofs when river sediments are used as part of a substrate mixture was relatively low. Despite some nutrient leaching in the initial phase of runoff from the green roofs, river sediment has the potential to be used as a substrate for extensive green roofs.

Effects of biochar-based fertilizers on nutrient leaching in a tobacco-planting soil

Biochar is a soil amendment for increasing soil quality and decreasing nutrient leaching. However, there is little information on the impact of biochar-based fertilizer (BF) on soil nutrient leaching in agricultural soils. We conducted a soil column leaching experiment to study the effects of BF on the leaching of total nitrogen (TN), total phosphorus, and total potassium (TK) in tobacco soils. The distribution characteristics of NH4+-N, available P, and available K in soil profiles were analyzed after the application of BF. Biochar was prepared by pyrolysis of flue-cured tobacco stems. It was applied at four levels, 0%, 3%, 9%, and 15% (w/w), respectively, to the compound fertilizer. Compared with the control, the leaching loss of soil TN decreased by 8.36%, 6.72%, and 6.45%, and the loss of soil TK decreased by 9.18%, 9.31% and 11.82% in the 3%, 9%, and 15% BF treatments, respectively. However, BF had no significant effect on the P leaching due to the low movement of P in the soil profile. In addition, the BF addition increased the immobilization of NH4+-N, available P, and available K in the soil profile. These results indicate that addition of BF to a tobacco-planting soil reduced nutrient leaching, and suggest that BF could be an effective method of applying biochar to agriculture fields.