Crop residues and fertilizer nitrogen influence residue decomposition and nitrous oxide emission from a Vertisol

Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching, denitrification, and nitrous oxide (N₂O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content 55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral N addition, on N mineralization–immobilization and N₂O emission. Residues were added at the rate of 3 t C ha⁻¹ to soil with, and without, 150 kg urea N ha⁻¹. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of soil N. Amended soil had significantly (P < 0.05) lower NO₃⁻–N, which reached minimum values of 2.8 mg N kg⁻¹ for sugarcane (at day 28), 10.3 mg N kg⁻¹ for maize (day 7), and 5.9 mg N kg⁻¹ for sorghum (day 7), compared to 22.7 mg N kg⁻¹ for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased by 45 mg N kg⁻¹ in sugarcane, 34 mg kg⁻¹ in maize, 29 mg kg⁻¹ in sorghum, and 16 mg kg⁻¹ in cotton amended soil compared to soil + N fertilizer, although soil NO₃⁻–N increased by 7 mg kg⁻¹ in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum emissions of N₂O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the cumulative N₂O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N₂O emission was significantly and positively correlated with NO₃⁻–N (r = 0.92, P < 0.01) and total mineral N (r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO₂ in the first 3 and 5 days of incubation (r = 0.59, P < 0.05).     

Nitrate and Phosphate Leaching under Turfgrass Fertilized with a Squid-based Organic Fertilizer

Consumer demand for cleaned squid generates a substantial amount of waste that must be properly disposed of, creating an economic burden on processors. A potential solution to this problem involves converting squid by-products into an organic fertilizer, for which there is growing demand. Because fertilizer application to lawns can increase the risk of nutrient contamination of groundwater, we quantified leaching of NO₃–N and PO₄–P from perennial ryegrass turf (Lolium perenne L.) amended with two types of fertilizer: squid-based (SQ) and synthetic (SY). Field plots were established on an Enfield silt loam, and liquid (L) and granular (G) fertilizer formulations of squid and synthetic fertilizers were applied at 0, 48, 146, and 292 kg N ha⁻¹ year⁻¹. Levels of NO₃–N and PO₄–P in soil pore water from a depth of 60 cm were determined periodically during the growing season in 2008 and 2009. Pore water NO₃–N levels were not significantly different among fertilizer type or formulation within an application rate throughout the course of the study. The concentration of NO₃–N remained below the maximum contaminant level (MCL) of 10 mg L⁻¹ until midSeptember 2009, when values above the MCL were observed for SQG at all application rates, and for SYL at the high application rate. Annual mass losses of NO₃–N were below the estimated inputs (10 kg N ha⁻¹ year⁻¹) from atmospheric deposition except for the SQG and SYL treatments applied at 292 kg N ha⁻¹ year⁻¹, which had losses of 13.2 and 14.9 kg N ha⁻¹ year⁻¹, respectively. Pore water PO₄–P levels ranged from 0 to 1.5 mg P L⁻¹ and were not significantly different among fertilizer type or formulation within an application rate. Our results indicate that N and P losses from turf amended with squid-based fertilizer do not differ from those amended with synthetic fertilizers or unfertilized turf. Although organic in nature, squid-based fertilizer does not appear to be more—or less—environmentally benign than synthetic fertilizers.     

Rewetting CO2 pulses in Australian agricultural soils and the influence of soil properties

An incubation study determined the effect of one dry–rewetting (DRW) event on the turnover of carbon (C), phosphorus (P) and nitrogen (N). Thirty-two soils were collected from different climatic regions of southern Australia, varying in soil type, land use and agronomic management history. We hypothesised that respiration and nutrient pulses are related to soil physio-chemical properties. Respiration (CO₂ release) was measured intensively for 90 h after rewetting. C mineralisation (C _min) model fitting was used to describe the amount of mineralisable C (Co_90 h) and the proportional mineralisation rate (k). Compared to constantly moist soils, 13 soils showed increases in both Co_90 h and k, indicating that DRW increased the amount of mineralisable C and the rate at which C was mineralised over the 90-h period. In 17 soils, k was increased but not Co_90 h, showing an increase in C mineralisation rate but no change in the amount of mineralisable C. Two soils showed a reduction in k with no change in Co_90 h, possibly due to low C contents and small microbial biomass. Only one soil exhibited no change in either Co_90 h or k. Multiple linear regression analysis indicated that the magnitude of the increase in mineralisable C in response to the DRW event (∆Co_90 h = Co_90 h DRW − Co_90 h moist) was primarily explained by clay content (39%); however, inclusion of nine soil physio-chemical properties explained more of the variation in ∆Co_90 h than any of the properties alone. Five of the nine physio-chemical variables present in the multiple-regression model were related to C content or composition. Pulses in available N and P were not related to ∆Co_90 h.     

Perchlorate Depositional History as Recorded in North American Ice Cores from the Eclipse Icefield, Canada, and the Upper Fremont Glacier, USA

Temporal depositional rates are important in order to understand the production and occurrence of perchlorate (ClO₄⁻) as limited information exists regarding the impact of anthropogenic production or atmospheric pollution on ClO₄⁻ deposition. Perchlorate concentrations in discrete ice core samples from the Eclipse Icefield (Yukon Territory, Canada) and Upper Fremont Glacier (Wyoming, USA) were analyzed using ion chromatography tandem mass spectrometry to evaluate temporal changes in the deposition of ClO₄ ⁻ in North America. The ice core samples cover a time period from 1726 to 1993 and 1970 to 2002 for the Upper Fremont Glacier (UFG) and Eclipse ice cores, respectively. The average ClO₄ ⁻ concentration in the Eclipse ice core for the time period from 1970 to 1973 was 0.6 ± 0.3 ng L⁻¹, with higher values of 2.3 ± 1.7 and 2.2 ± 2.0 ng L⁻¹ for the periods 1982–1986 and 1999–2002, respectively. All pre-1980 ice core samples from the UFG had ClO₄ ⁻ concentrations <0.2 ng L⁻¹, and the post-1980 samples ranged from <0.2 ng L⁻¹ to a maximum of 2.6 ng L⁻¹ for the year 1992. A significant positive correlation (R = 0.75, N = 15, p < 0.001) of ClO₄⁻ with SO₄²⁻ was found for the annual UFG ice core layers and of ClO₄ ⁻ with SO₄²⁻ and NO₃⁻ in sub-annual Eclipse ice samples (R > 0.3, N = 121, p < 0.002). The estimated yearly ClO₄⁻ depositional flux for the Eclipse ice core ranged from 0.6 (1970) to 4.7 μg m⁻² year⁻¹ (1982) and the UFG from <0.1 (pre-1980) to 1.4 μg m⁻² year⁻¹ (1992). There was no consistent seasonal variation in the ClO₄⁻ depositional flux for the Eclipse ice core, in contrast to a previous study on the Arctic region. The presence of ClO₄⁻ in these ice cores might correspond to an intermittent source such as volcanic eruptions and/or any anthropogenic forcing that may directly or indirectly aid in atmospheric ClO₄⁻ formation.     

Effectiveness of Air,N<Subscript>2</Subscript> (gas), Fe<Superscript>+3</Superscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles on the Sonication of Less and More Hydrophobic Polycyclic Aromatic Hydrocarbons (PAHs) and Toxicity

In this study, the effects of 1 h aeration, nitrogen gas N₂(g) sparging (15 and 30 min) and increasing ferric ions (Fe⁺³) as FeSO₄ (10, 20 and 50 mg L⁻¹) and Fe₃O₄ nanoparticles (1, 2 and 4 g L⁻¹) concentrations on three less hydrophobic and three more hydrophobic polycyclic aromatic hydrocarbons (PAHs) and toxicity removals from a petrochemical industry in Izmir (Turkey) were investigated in a sonicator with a power of 650 W and an ultrasound frequency of 35 kHz; 1 h aeration increased the yields in benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene PAHs (less hydrophobic) from 62% to 67% to around 95–97% after 150 min sonication at 60°C. However, 1 h aeration did not contribute to the yields of more hydrophobic PAHs (indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene). The maximum yields were obtained at acidic and alkaline pH for more and less hydrophobic PAHs, respectively, after 60 and 120 min sonication at 30°C; 30 min N₂(g) sparging, 50 mg L⁻¹ Fe⁺³ increased the yields of less hydropobic PAHs after 150 min sonication at 60°C. Two milligrams per liter of Fe₃O₄ nanoparticles increased both less (87–88%) and more (96–98%) hydrophobic PAH yields. The Daphnia magna acute toxicity test showed that the toxicity decreased significantly with an hour aeration, 30 min N₂(g) sparging, 50 mg L⁻¹ Fe⁺³ and 2 g L⁻¹ Fe₃O₄ nanoparticles at 60°C after 120 and 150 min sonications. Vibrio fischeri was found to be more resistant to the sonicated samples than D. magna. Significant correlations were found between the physicochemical properties of sonicated PAHs and acute toxicities both organisms.     

Effects of moisture and temperature on greenhouse gas emissions and C and N leaching losses in soil treated with biogas slurry

The objective of this study was to examine the effects of soil moisture, irrigation pattern, and temperature on gaseous and leaching losses of carbon (C) and nitrogen (N) from soils amended with biogas slurry (BS). Undisturbed soil cores were amended with BS (33 kg N ha⁻¹) and incubated at 13.5°C and 23.5°C under continuous irrigation (2 mm day⁻¹) or cycles of strong irrigation and partial drying (every 6 weeks, 1 week with 12 mm day⁻¹). During the 6 weeks after BS application, on average, 30% and 3.8% of the C and N applied with BS were emitted as carbon dioxide (CO₂) and nitrous oxide (N₂O), respectively. Across all treatments, a temperature increase of 10°C increased N₂O and CO₂ emissions by a factor of 3.7 and 1.7, respectively. The irrigation pattern strongly affected the temporal production of CO₂ and N₂O but had no significant effect on the cumulative production. Nitrogen was predominantly lost in the form of nitrate (NO₃⁻). On average, 16% of the N applied was lost as NO₃⁻. Nitrate leaching was significantly increased at the higher temperature (P < 0.01), while the irrigation pattern had no effect (P = 0.63). Our results show that the C and N turnovers were strongly affected by BS application and soil temperature whereas irrigation pattern had only minor effects. A considerable proportion of the C and N in BS were readily available for soil microorganisms.     

Attenuation of Nitrogen,Phosphorus and <Emphasis Type="Italic">E. coli</Emphasis> Inputs from Pasture Runoff to Surface Waters by a Farm Wetland: the Importance of Wetland Shape and Residence Time

Water quantity and quality were monitored for 3 years in a 360-m-long wetland with riparian fences and plants in a pastoral dairy farming catchment. Concentrations of total nitrogen (TN), total phosphorus (TP) and Escherichia coli were 210–75,200 g N m⁻³, 12–58,200 g P m⁻³ and 2–20,000 most probable number (MPN)/100 ml, respectively. Average retentions (±standard error) for the wetland over 3 years were 5 ± 1%, 93 ± 13% and 65 ± 9% for TN, TP and E. coli, respectively. Retentions for nitrate–N, ammonium–N, filterable reactive P and particulate C were respectively −29 ± 5%, 32 ± 10%, −53 ± 24% and 96 ± 19%. Aerobic conditions within the wetland supported nitrification but not denitrification and it is likely that there was a high conversion rate from dissolved inputs of N and P in groundwater, to particulate N and P and refractory dissolved forms in the wetland. The wetland was notable for its capacity to promote the formation of particulate forms and retain them or to provide conditions suitable for retention (e.g. binding of phosphate to cations). Nitrogen retention was generally low because about 60% was in dissolved forms (DON and NO_X–N) that were not readily trapped or removed. Specific yields for N, P and E. coli were c. 10–11 kg N ha⁻¹ year⁻¹, 0.2 kg P ha⁻¹ year⁻¹ and ≤10⁹ MPN ha⁻¹ year⁻¹, respectively, and generally much less than ranges for typical dairy pasture catchments in New Zealand. Further mitigation of catchment runoff losses might be achieved if the upland wetland was coupled with a downslope wetland in which anoxic conditions would promote denitrification.     

Influence of N and non-N salts on atmospheric methane oxidation by upland boreal forest and tundra soils

 The short-term (24 h) and medium-term (30 day) influence of N salts (NH₄Cl, NaNO₃ and NaNO₂) and a non-N salt (NaCl) on first-order rate constants, k (h^–1) and thresholds (C_Th) for atmospheric CH₄ oxidation by homogenized composites of upland boreal forest and tundra soils was assessed at salt additions ranging to 20 μmol g^–1 dry weight (dw) soil. Additions of NH₄Cl, NaNO₃ and NaCl to 0.5 μmol g^–1 dw soil did not significantly decrease k relative to watered controls in the short term. Higher concentrations significantly reduced k, with the degree of inhibition increasing with increasing dose. Similar doses of NH₄Cl and NaCl gave comparable decreases in k relative to controls and both soils showed low native concentrations of NH₄ ⁺-N (≤1 μmol g^–1dw soil), suggesting that the reduction in k was due primarily to a salt influence rather than competitive inhibition of CH₄ oxidation by exogenous NH₄ ⁺-N or NH₄ ⁺-N released through cation exchange. The decrease in k was consistently less for NaNO₃ than for NH₄Cl and NaCl at similar doses, pointing to a strong inhibitory effect of the Cl^– counter-anion. Thresholds for CH₄ oxidation were less sensitive to salt addition than k for these three salts, as significant increases in C_Th relative to controls were only observed at concentrations ≥1.0 μmol g^–1 dw soil. Both soils were more sensitive to NaNO₂ than to other salts in the short term, showing a significant decrease in k at an addition of 0.25 μmol NaNO₂ g^–1 dw soil that was clearly attributable to NO₂ ^–. Soils showed no recovery from NaCl, NH₄ ⁺-N or NaNO₃ addition with respect to atmospheric CH₄ oxidation after 30 days. However, soils amended with NaNO₂ to 1.0 μmol NaNO₂ g^–1 dw showed values of k that were not significantly different from controls. Recovery of CH₄-oxidizing ability was due to complete oxidation of NO₂ ^–-N to NO₃ ^–-N. Analysis of soil concentrations of N salts necessary to inhibit atmospheric CH₄ oxidation and regional rates of N deposition suggest that N deposition will not decrease the future sink strength of upland high-latitude soils in the atmospheric CH₄ budget. Received: 30 April 1999     

The effect of reduced tillage on nitrous oxide emissions of silt loam soils

The effect of reduced tillage (RT) on nitrous oxide (N₂O) emissions of soils from fields with root crops under a temperate climate was studied. Three silt loam fields under RT agriculture were compared with their respective conventional tillage (CT) field with comparable crop rotation and manure application. Undisturbed soil samples taken in September 2005 and February 2006 were incubated under laboratory conditions for 10 days. The N₂O emission of soils taken in September 2005 varied from 50 to 1,095 μg N kg⁻¹ dry soil. The N₂O emissions of soils from the RT fields taken in September 2005 were statistically (P < 0.05) higher or comparable than the N₂O emissions from their respective CT soil. The N₂O emission of soils taken in February 2006 varied from 0 to 233 μg N kg⁻¹ dry soil. The N₂O emissions of soils from the RT fields taken in February 2006 tended to be higher than the N₂O emissions from their respective CT soil. A positive and significant Pearson correlation of the N₂O–N emissions with nitrate nitrogen (NO₃ ⁻–N) content in the soil was found (P < 0.01). Leaving the straw on the field, a typical feature of RT, decreased NO₃ ⁻–N content of the soil and reduced N₂O emissions from RT soils.     

Denitrification from the horticultural peats: effects of pH,nitrogen, carbon,and moisture contents

Denitrification plays an important role in N-cycling. However, information on the rates of denitrification from horticultural growing media is rare in literature. In this study, the effects of pH, N, C, and moisture contents on denitrification were investigated using four moderately decomposed peat types (oligotrophic, mesotrophic, eutrophic, and transitional). Basal and potential denitrification rates (20°C, 18 h) from the unlimed peat samples varied widely from 2.0 to 21.8 and from 118.9 to 306.6 μg (N₂O + N₂)–N L⁻¹ dry peat h⁻¹, respectively, with the highest rates from the eutrophic peat and the lowest from the transitional one. Both basal and potential denitrification rates were substantially increased by 3.6–14- and 1.4–2.3-fold, respectively, when the initial pH (4.3–4.8) was raised to 5.9–6.5 units. Emissions of (N₂O + N₂)–N from oligotrophic, mesotrophic, and transitional peats were markedly increased by the addition of 0.15 g NO₃–N L⁻¹ dry peat but further additions had no effect. Denitrification rates were increased by increasing glucose concentration suggesting that the activity of denitrifiers in all peat types was limited by the low availability of easily decomposable C source. Increasing moisture contents of all peats from 40 to 50% water-filled pore space (WFPS) did not significantly (p > 0.05) increase (N₂O + N₂)–N emissions. However, a positive effect was observed when the moisture contents were increased from 60% to 70% WFPS in the eutrophic peat, from 70% to 80% in the transitional, from 80% to 90% in the oligotrophic and from 70% to 90% in the mesotrophic peat. It can be concluded that liming, N-fertilization, availability of easily decomposable C, and moist condition above 60% WFPS could encourage denitrification from peats although the rates are greatly influenced by the peat-forming environments (eutrophic > mesotrophic > oligotrophic > transitional types).     

Production of Perchlorate by Laboratory Simulated Lightning Process

Perchlorate (ClO₄⁻), a thyroid hormone disruptor, is both naturally occurring and a man-made contaminant increasingly found in a variety of terrestrial environments. The environmental presence of ClO₄⁻ is considered to be the result of atmospheric formation and deposition processes. The ultimate processes, particularly heterogeneous-based reactions, leading to natural ClO₄⁻ formation are not well understood. Oxidation of chlorine species by an energetic source such as lightning is considered to be one of the potential heterogeneous sources of natural ClO₄⁻. Currently, there is very little information available on lightning-induced ClO₄⁻. We designed a laboratory electrical discharge reactor capable of evaluating ClO₄⁻ formation by the oxidation of “dry” sodium chloride (NaCl) aerosols (relative humidity (RH) <70%) in electrical discharge plasma at voltages and energies up to 24 kV and 21 kJ, respectively. Similar to other non-electrochemical ClO₄⁻ production processes, the amount of ClO₄⁻ produced (0.5–4.8 μg) was 3 orders of magnitude lower than the input Cl⁻ (7.1–60.1 mg). The amount of ClO₄⁻ generated increased with peak voltage (V) and theoretical maximum discharge energy with ΔClO₄⁻/ΔV = 0.28 × 10⁻³ μg V⁻¹ (R ² = 0.94) and ΔClO₄⁻/ΔE = 0.44 × 10⁻³ μg J⁻¹ (R ² = 0.83). The total ClO₄⁻ generated decreased with an increase in relative humidity from 2.8 ± 0.1 μg (RH ∼46%) to 0.9 ± 0.1 μg (RH ∼62%) indicating that the presence of moisture inhibits the formation of ClO₄⁻. Additional modifications to the reactor support the hypothesis of ClO₄⁻ formation due to the action of plasma on Cl⁻ aerosols as opposed to direct oxidation on the surface of the electrodes. Finally, the contribution of lightning-induced ClO₄⁻ in North America is calculated to have a wide range from 0.006 × 10⁵ to 5 × 10⁵ kg/year and is within the range of the measured ClO₄⁻ depositional flux in precipitation samples obtained across the USA (0.09 × 10⁵–1.2 × 10⁵ kg/y).     

Plant Availability and Uptake of Lead, Zinc, and Cadmium in Soils Contaminated with Anti-corrosion Paint from Pylons in Comparison to Heavy Metal Contaminated Urban Soils

Red lead (Pb₃O₄) has been used extensively in the past as an anti-corrosion paint for the protection of steel constructions. Prominent examples being some of the 200,000 high-voltage pylons in Germany which have been treated with red lead anti-corrosion paints until about 1970. Through weathering and maintenance work, paint compounds and particles are deposited on the soils beneath these constructions. In the present study, six such “pylon soils” were investigated in order to characterize the plant availability and plant uptake of Pb, Cd, and Zn. For comparison, three urban soils with similar levels of heavy metal contamination were included. One phase extractions with 1 M NH₄NO₃, sequential extractions (seven steps), and extractions at different soil pH were used to evaluate the heavy metal binding forms in the soil and availability to plants. Greenhouse experiments were conducted to determine heavy metal uptake by Lolium multiflorum and Lactuca sativa var. crispa in untreated and limed red lead paint contaminated soils. Concentrations of Pb and Zn in the pylon soils were elevated with maximum values of 783 mg Pb kg⁻¹ and 635 Zn mg kg⁻¹ while the soil Cd content was similar to nearby reference soils. The pylon soils were characterized by exceptionally high proportions of NH₄NO₃-extractable Pb reaching up to 17% of total Pb. Even if the relatively low pH of the soils is considered (pH 4.3–4.9), this appears to be a specific feature of the red lead contamination since similarly contaminated urban soils have to be acidified to pH 2.5 to achieve a similarly high Pb extractability. The Pb content in L. multiflorum shoots reached maximum values of 73 mg kg⁻¹ after a cultivation time of 4 weeks in pylon soil. Lime amendment reduced the plant uptake of Pb and Zn significantly by up to 91%. But L. sativa var. crispa cultivated on soils limed to neutral pH still contained critical Pb concentrations (up to 0.6 mg kg⁻¹ fresh weight). Possible mechanisms for the exceptionally high plant availability of soil Pb derived from red lead paint are discussed.     

Spatial variability and biophysicochemical controls on N<Subscript>2</Subscript>O emissions from differently tilled arable soils

Nitrous oxide (N₂O) emissions, soil microbial community structure, bulk density, total pore volume, total C and N, aggregate mean weight diameter and stability index were determined in arable soils under three different types of tillage: reduced tillage (RT), no tillage (NT) and conventional tillage (CT). Thirty intact soil cores, each in a 25 × 25-m² grid, were collected to a depth of 10 cm at the seedling stage of winter wheat in February 2008 from Maulde (50°3′ N, 3°43′ W), Belgium. Two additional soil samples adjacent to each soil core were taken to measure the spatial variance in biotic and physicochemical conditions. The microbial community structure was evaluated by means of phospholipid fatty acids analysis. Soil cores were amended with 15 kg NO₃⁻-N ha⁻¹, 15 kg NH₄⁺-N ha⁻¹ and 30 kg ha⁻¹ urea-N ha⁻¹ and then brought to 65% water-filled pore space and incubated for 21 days at 15°C, with regular monitoring of N₂O emissions. The N₂O fluxes showed a log-normal distribution with mean coefficients of variance (CV) of 122%, 78% and 90% in RT, NT and CT, respectively, indicating a high spatial variation. However, this variability of N₂O emissions did not show plot scale spatial dependence. The N₂O emissions from RT were higher (p < 0.01) than from CT and NT. Multivariate analysis of soil properties showed that PC1 of principal component analysis had highest loadings for aggregate mean weight diameter, total C and fungi/bacteria ratio. Stepwise multiple regression based on soil properties explained 72% (p < 0.01) of the variance of N₂O emissions. Spatial distributions of soil properties controlling N₂O emissions were different in three different tillages with CV ranked as RT > CT > NT.     

Use of Ozonization for the Treatment of Dye Wastewaters Containing Rhodamine B in the Agate Industry

The industrial processing of precious stones is a source of revenue for several Brazilian towns, especially in the state of Rio Grande do Sul. Given the growing number of small-sized companies that process precious stones, wastewater production is inevitable and is a cause for concern inasmuch as preservation of nature is considered. The present study investigates the detoxification of the wastewater produced by the process of rhodamine B dyeing using oxidation processes. Ozonization (O₃), ultraviolet irradiation (UV), and O₃/UV methods were assessed. Some of the parameters used to measure the efficiency of the analyzed treatments included COD, ecotoxicity (Daphnia magna), cytotoxicity, and genotoxicity assays (Allium cepa assays). Results show predominance of negative and local environmental impacts, which are reversible in more than 70% of cases. The major proposed reversibility measures were the change in the process layout and dye wastewater segregation. Among the analyzed methods, ozonization proved to be more efficient in decolorization, with 60 min of treatment, pH = 9 and dosage of 5.705 mg O₃/mg of rhodamine B. A pseudo first-order reaction, with a kinetic constant of 7.5 × 10⁻² min⁻¹, was observed. The cytotoxic and genotoxic effects were assessed for both raw and treated wastewaters. Despite complete decolorization, cytotoxicity and genotoxicity assays revealed an EC₅₀ of 28.6, in addition to chromosome aberrations in 40% of dividing cells for the treated wastewater.     

Effects of nitrogen fertilizer application rates on nitrate nitrogen distribution in saline soil in the Hai River Basin,China

Background and Objectives  

Soil nitrate nitrogen (NO₃ ⁻-N) accumulation is related closely to NO₃ ⁻ leaching, which is an important issue in groundwater pollution, especially in intensive agricultural areas with saline soils where volumes of water are used in irrigation to avoid salt accumulation in the root zone. However, in the saline environment in Hai River Basin, China, the importance of detailed research into NO₃ ⁻-N distribution in the root zone has not been adequately recognized. Considering the impacts of eco-environmental system N and crop production, the present study aimed at contributing to an understanding of the effects of N application rate on soil NO₃ ⁻-N distribution, NO₃ ⁻-N residue, N loss, and maize (Zea mays L.) yield in this region.     

Oxidation of Chlorophenols in Aqueous Solution by Excess Potassium Permanganate

A simple spectrophotometric method was developed to quantify chlorophenol (CP) concentrations after reaction with potassium permanganate and quenching with sodium sulfite. Other quenching agents (peroxide, sodium thiosulfate and hydroxylamine hydrochloride) were found to create absorbance in the spectral range required for CP quantification. Analysis at pH 12 gave greater absorption and sensitivity for the method compared with pH 5.6. The calibration curves of the proposed methods were linear in the concentration ranges 0.0061–0.61 and 0.0078–0.78 mM with detection limit of 0.0006 and 0.0008 mM for dichlorophenols and monochlorophenols, respectively. The oxidation kinetics of five chlorophenols in aqueous solution with excess potassium permanganate were evaluated using the analytical method. The pseudo-first-order reaction rates were found to be relatively rapid 1.42 × 10⁻³ to 0.024 s⁻¹ and followed the sequence 2-chlorophenol (2-CP) > 2,6-dichlorophenol (2,6-DCP) > 4-chlorophenol (4-CP) > 2,4-dichlorophenol (2, 4-DCP) > 3-chlorophenol (3-CP). The apparent second-order rate constant was calculated from the measured pseudo-first-order rate constant with respect to CP with initial KMnO₄ concentration (1.5 mM) and follows the same sequence of pseudo-first-order rate constant. This shows that chlorine atoms in the structure of chlorophenol had a significant influence on the oxidation of chlorophenols by potassium permanganate. Permanganate can be used for the treatment of chlorophenol-contaminated soil and groundwater.     

Atmospheric Mercury Fluxes in a Southern Boreal Forest and Wetland

Total gaseous mercury (TGM) fluxes from the forest floor and a boreal wetland were measured by a flux chamber technique coupled with an automatic mercury vapour analyser. The fluxes were measured at three sampling sites in southern Finland, 61°14′ N, 25°04′ E in summer 2007, with additionally in situ TGM concentrations in the air at one of the sites and mercury bulk deposition at another. Most of the flux data were collected during the daytime. At one of the sites, diurnal flux behaviour was studied, and a clear cycle with an afternoon maximum and a night minimum was observed. The highest emissions (up to 3.5 ng m⁻² h⁻¹) were observed at the forest floor site having a moss and grass cover. At the wetland and litter-rich forest floor sites, the emissions were below 1 ng m⁻² h⁻¹ and sometimes negative (down to −1.0 ng m⁻² h⁻¹), indicating mercury uptake. The measured average fluxes in August were 0.9 ± 1.1 and 0.2 ± 0.3 ng m⁻² h⁻¹ for the forest floor sites and wetland sites, respectively. The flux data were compared with the mercury bulk deposition, which proved to be of the same magnitude, but opposite in sign. At the mossy forest floor site, the extrapolated TGM emissions were 130% of the Hg deposition in August 2007. Comparison with other studies showed that the fluxes in background areas are relatively uniform, regardless of measurement site location and method used. Airborne TGM remained at the background level during the study, with an average value of 1.3 ± 0.2 ng m⁻³; it frequently showed a diurnal cycle pattern.     

Physicochemical,including spectroscopic,and biological analyses during composting of green tea waste and rice bran

The aims of this study were to monitor the changes in physicochemical, including spectroscopic, and biological characteristics during composting of green tea waste–rice bran compost (GRC) and to define parameters suitable for evaluating the stability of GRC. Compost pile temperature reflected the initiation and stabilization of the composting process. The pH, electrical conductivity, NO₃ ⁻-N content, and carbon-to-nitrogen ratio were measured as chemical properties of the compost. The color (CIELAB variables), humification index (the absorption ratio Q _4/6 = A ₄₇₂ / A ₆₆₄ of 0.5 M NaOH extracts), absorption at 665 nm of acetone extracts, and Fourier-transform infrared (FT-IR) spectra were measured to evaluate the organic matter transformation; germination of komatsuna or tomato seeds was measured to assess the potential phytotoxicity of composting materials during composting. No single parameter was capable of giving substantial information on the composting process, the nutrient balance, phytotoxicity, and organic matter decomposition. The FT-IR spectra at 3,300, 2,930, 2,852, and 1,065 cm⁻¹ provided information on the molecular transformation of GRC during composting and they decreased over the composting. Most of the assayed parameters showed no further change after about 90 days of composting suggesting that GRC can be used for agricultural purposes after this period.     

Characterization of Swine Wastewater by Toxicity Identification Evaluation Methodology (TIE)

Since swine wastewater is used by farmers for soil fertilization, evaluation of toxic compounds or micro-contaminants of separate streams is required. This paper uses the toxicity identification evaluation (TIE) procedure for the physicochemical and ecotoxicological characterization of swine wastewater. To distinguish the most important toxic compounds, a physicochemical characterization and phase I-TIE procedure were performed. The acute toxic effect of swine wastewater and treated fractions (phase II-TIE) were evaluated using Daphnia magna determining 48-h LC₅₀. Results show a high level of conductivity (23.5 μS cm⁻¹), which is explained as due to the concentration of ions, such as ammonium (NH₄⁺–N 1.6 g L⁻¹), sulfate (SO₄²⁻ 397.3 mg L⁻¹), and chlorine (Cl⁻ 1,230.0 mg L⁻¹). The acute toxicity of the swine wastewater was evaluated on D. magna (48-h LC₅₀ = 3.4%). Results of the different water treatments indicate that anionic exchange treatments could reduce 22.5% of swine wastewater’s acute toxicity by reducing chlorine (to around 51%) and conductivity (8.5%). On the other hand, cationic exchange treatment increased acute toxicity on D. magna (% RT = −624.4%), by reducing NH₄⁺–N (around 100%) and total nitrogen (95.5%). This finding suggests that part of the toxicity comes from anionic compounds, such as chlorine.     

Nitrogen Cycling in Pinus banksiana and Populus tremuloides Stands in the Athabasca Oil Sands Region, Alberta, Canada

Elevated emissions of nitrogen oxides (NO_x) in the Athabasca Oil Sands Region, Alberta and higher foliar nitrogen (N) concentrations in jack pine (Pinus banksiana) needles close to major emission sources has led to concerns that the surrounding boreal forest may become N-saturated. Despite these concerns, N deposition and impacts on upland forests in the region is poorly quantified. The objective of this study was to characterize N cycling in five plots representing the two dominant upland forest types (jack pine and trembling aspen, Populus tremuloides) close (<30 km) to the largest mining operations in the region, during a 2-year period. Despite the high level of NO_x emissions, bulk throughfall and deposition measured at both study sites were surprisingly very low (<2 kg N ha⁻¹ year⁻¹). Internal N cycling was much greater in aspen stands; annual N input in litterfall was ten times greater, and net N mineralization rates were two to five times greater than in jack pine stands. Nitrogen use efficiency (NUE) was much greater in jack pine when calculated based on N litterfall indices, but not when N pools in biomass were considered. Despite differences in internal cycling among forest types, nitrate leaching from mineral soil in both forest types was negligible (<0.1 kg N ha⁻¹ year⁻¹) and patterns of ¹⁵N in roots, foliage, and mineral soil were typical of N-limited ecosystems, and both sites show no evidence of N saturation.