Nanoparticulate Zeolitic Tuff for Immobilizing Heavy Metals in Soil: Preparation and Characterization

Nanoparticles derived from natural materials are promising compounds in the field of environmental remediation. The present study produces and characterizes Na-zeolitic tuff in the nanorange, stabilizes the nanotuff in suspension, and investigates the effect of Na-zeolitic nanotuff on sorption of Cd. Breakdown of raw zeolitic tuff with a mean particle size of 109 μm to the nanorange was achieved by attrition milling. In the first stage of grinding, a mixture of Al-oxide beads of 1 to 2.6 mm diameter was used. The milling process lasted 4 h. In the second stage, the dried powder was milled again using a mixture of a fine zirconia beads (0.1 mm) and Al-oxide beads (1.0 mm). The powder was treated with 1 M NaCl solution. Finally, the powder was sonicated in water. After this procedure, the mean and median particle diameters were 47.6 and 41.8 nm, respectively. The nanoparticulate zeolitic tuff had a surface area of 82 m² g^?1. The estimated zero charge point of the nanoparticle suspension was 3.2. The surface zeta potential was pH dependent. The Na-zeolitic nanotuff increased Cd sorption by a factor of up to 3 compared to the raw zeolitic tuff. Our results indicate that zeolitic nanoparticles can be produced by grinding using a mixture of fine beads in an attrition mill and that this procedure increases their metal immobilizing potential.     

Biogas digestates based on lignin-rich feedstock – potential as fertilizer and soil amendment

With advances in biogas technology, lignocellulosic material may be increasingly included in feedstock due to the abundance of raw materials. The main goal of this study was to evaluate fertilizing and soil amendment effects of digestates based on lignin-rich feedstock. The digestates originated from reactors fed with manure co-digested with Salix, wheat straw or sugarcane bagasse, respectively. In pot experiments with three different soils, Italian ryegrass and reed canary grass were grown with 120 kg ha^?1 total nitrogen or 150 kg ha^?1 available nitrogen, respectively, given as either mineral fertilizer or digestate. Soil chemical and physical characteristics were determined after ended experiments. Additionally, an incubation study was carried out to estimate N mineralization from one digestate over time. Digestate addition resulted in similar yields compared to mineral fertilizer, varying from 0.5 (loam) to 1 kg dry matter m^?2 (silt) for Italian ryegrass and 1.2 (loam) to 2.3 kg m^?2 (silt) for reed canary grass. Digestates contributed to a favourable pH for plant growth, reduced bulk density in the loam and improved water retention characteristics in the sand. Biogas digestates based on lignin-rich feedstock appear promising as fertilizers and for soil amelioration but results have to be verified in field experiments.     

Optimizing water,nitrogen and crop density in canola cultivation using response surface methodology and central composite design

Abstract

Optimisation of water and nitrogen use is an effective management tool to conserve resources and reduce environmental pollutions. Response surface methodology (RSM) is defined as a collection of mathematical and statistical methods that are used to develop, to improve or to optimize a product or process. In order to determine optimum levels of water, nitrogen and planting density of canola (Brassica napus L.), a 2-year experiment (2010–2011) was carried out by central composite design as RSM at the research station of Ferdowsi University of Mashhad. The treatments were designed based on low and high levels of irrigation (1500 and 4000 m³ ha^?1), nitrogen (0 and 400 kg N ha^?1) and density (50 and 150 plant m^?2) as independent variables. Furthermore, seed yield, nitrogen losses, nitrogen use efficiency (NUE) and water use efficiency (WUE) were measured as response variables in a full quadratic polynomial model. Optimum levels of irrigation, nitrogen and planting density were suggested to achieve the target range of dependent variables based on three scenarios: economic, environmental and eco-environmental. The results showed that increasing irrigation and fertilizer led to an increase in seed yield and nitrogen losses, whereas increasing canola density resulted in an increase in seed yield but a decrease in nitrogen losses. The optimum levels of water, fertilizer and density based on environmental scenario were 1802 m³ ha^?1, 11 kg N ha^?1 and 122 plant m^?2, respectively. To achieve optimum conditions under the economic scenario, it is necessary to use 3411 m³ water ha^?1, 178 kg N ha^?1 and 119 plant m^?2. Amounts of 2347 m³ water ha^?1, 92 kg N ha^?1 and 114 plant m^?2 were found to be the optimum conditions for the eco-environmental scenario. In general, it seems that resource use based on the eco-environmental scenario may be the most favorable cropping strategy for canola production.     

Soil management for raising crop water productivity in rainfed production systems in Lao PDR

This study investigated the impacts of organic- and clay-based soil amendments, and their combinations on crop water productivity (CWP) using maize as a test crop. On-station field trials were established over two consecutive years at the Naphok and Veunkham sites in Laos. At each site, 10 treatments were applied in a randomized complete block design with three replications. The treatments were control, rice husk biochar (10 t ha^?1), bentonite clay (10 t ha^?1), compost (4 t ha^?1), clay-manure compost (10 t ha^?1), rice husk biochar compost (10 t ha^?1), bentonite clay + biochar, bentonite-clay + compost, biochar + compost, and bentonite clay + biochar + compost. All treatments were applied in 2011. Significant (p < 0.05) treatment effects in CWP and growing period evapotranspiration were determined. At Naphok, differences between the amended and control plots in CWP varied between 0.1 and 0.6 kg m^?3 in 2011 and from 0.1 to 0.4 kg m^?3 in 2012, whereas differences at Veunkham varied between 0.3 and 1.0 kg m^?3 in 2011 and from 0.05 to 0.29 kg m^?3 in 2012. At both sites, CWP in 2012 was significantly lower than 2011. Our results illustrate that organic- and clay-based soil amendments improve CWP, indicating that soil-based interventions could be suitable options for improving agricultural productivity.     

A practical formula for quantifying the thermal conductivity of Tottori dune sand

Abstract

Sustainable agriculture needs appropriate management of water, chemicals and heat in soil. In this study, we focused on thermal conductivity, which is among the various soil physical properties that are crucial for the sustainable management of agricultural fields. To expand the Mochizuki model, which describes thermal conductivity as a function of water content and solution concentration, we considered the water content, solution concentration and temperature as independent variables. The thermal conductivity of Tottori dune sand was measured under conditions of various combinations of these three independent variables. We observed that the thermal conductivity increased linearly with increasing water content, 0.054–0.276 m³ m^?3, for fixed temperature and solution concentration, and varied linearly with solution concentration for fixed temperature and water content. These results are consistent with the Mochizuki model. Using the Mochizuki model, the experimental parameters, which are dependent variables of water content and solution concentration, are shown as functions of water content. From regression analyses of the relationships between the experimental parameters and temperature, we expanded the Mochizuki model into a new practical formula that quantifies the soil thermal conductivity as a function of water content, solution concentration and temperature.     

Effect of continuous and intermittent irrigation methods on rice (cv. Koohrang) yield

This study was carried out to evaluate the impact of permanent and intermittent irrigation on the yield of rice (cv. Koohrang) in Lordegan rice-growing areas in Chaharmahal and Bakhtiari Province (Iran). The experiment was set up in a randomized complete block design with four treatments and four replications during 2003 and 2004. Irrigation treatments were: I1, continuous irrigation with a 5-cm water head every day; I2, alternative irrigation with a 5-cm water head every 2 days; I3, alternative irrigation with a 5-cm water head every 4 days; and I4, alternative irrigation with a 5 cm water head every 6 days. Results showed that the paddy yield was highest under treatment I2 (5655.6 kg ha^?1) and lowest under treatment I4 (3421.3 kg ha^?1). The highest rate of water use was obtained in I1 with 17 687.5 m³ ha^?1 and the lowest in I4 with 9325 m³ ha^?1. Paddy yield, plant height, panicle length and 1000-seed weight did not show a significant difference at the 5% level among I1, I2 and I3, but differed significantly to I4. Thus irrigation treatment I3 is appropriate for paddy irrigation in the Lordegan region with 10 645 m³ ha^?1 water use and 5483.7 kg ha^?1 paddy yield.     

Measurement Uncertainty of Sulphur and Nitrogen Containing Inorganic Compounds By 1-Stage and 2-Stage Filter-pack Methods

The sampling and analysis properties of 1-stage and 2-stage filter-pack methods were studied in detail in monitoring of sulphur and nitrogen containing inorganic gases and particles (sulphur dioxide, sulphate, sum of nitric acid and nitrate and total ammonium). The limit of detection and the limit of quantitation for 24-h samples were estimated using the results of a short-term field experiment completed with available data from long-term monitoring and internal quality assurance. Furthermore, the combined expanded measurement uncertainty including sampling and analysis (U_tot) was estimated for filter-pack methods in order to give a tool for distinguishing long-term trends in air quality from the measurement variability. U_tot was found to be very near the analytical uncertainty when measuring higher air concentration levels, being ± 4.0% for sulphur concentrations?>?1.0 μg m^?3, ± 3.0% for sulphate concentrations?>?0.5 μg m^?3, ± 3.5% for the sum of nitrate and nitric acid concentrations?>?0.3 μg m^?3 and ± 4.5% for total ammonium concentrations?>?0.8 μg m^?3. At the lower air concentration range U_tot increases significantly due to the field blank values. The precision of the 24-h filter-pack sample results expressed by means of modified median absolute difference (M.MAD) and coefficient of variance (CoV) gave 8.3% for sulphur dioxide and 5.4% for particulate sulphate. For the sum of gaseous nitric acid and particulate nitrate the CoV was 5.5% and for total ammonium 4.3%. In addition the suitability of the 24-h filter-pack methods in weekly sampling was proved.     

Effect of Organic Ligands on Copper(II) Removal from Metal Plating Wastewater by Orange Peel-based Biosorbents

A neutrophilic, autotrophic bacterium that couples iron oxidation to nitrate reduction (iron-oxidizing bacteria [IOB]) under anoxic conditions was isolated from a working bioremediation site in Trail, British Columbia. The site was designed and developed primarily to treat high concentrations of Zn and As that originate from capped industrial landfill sites. The system consisted of two upflow biochemical reactor cells (BCR) followed by three vegetated wetland polishing cells with sub-surface flow and a holding pond. During a 5-year period (2003–2007), the system treated more than 19,100 m³ of contaminated water, removing and sequestering more than 10,700 kg of As, Zn and sulfate at average input water concentrations of: As, 58.6 mg?l^?1 (±39.9 mg?l^?1); Zn, 51.9 mg?l^?1 (±35.4 mg?l^?1) and SO₄ ^2?, 781.5 mg?l^?1 (±287.8 mg?l^?1). The bacterium was isolated in order to better understand the mechanisms underlying the consistent As removal that took place in the system. Analysis using Basic Local Alignment Search Tool (BLAST) database showed that the closest homologies are to Candidatus accumulibacterphosphatis (95 % homology), Dechloromonas aromatica (94 %), and Sideroxydans lithotrophicus ES-1 (92 %) Within the BCR cells, the IOB oxidized Fe²⁺ generated by iron-reducing bacteria (IRB); the source of the iron was most likely biosolids and coatings of iron oxide on locally available sand used in the matrix. We have provisionally designated the novel bacterium as TR1.     

Evaluation of a Quasi-steady-state Respiration Test in a Full-scale Biopile

A quasi steady state respiration test based on Fick’s law with a correction term for advective flux, for estimating petroleum hydrocarbon degradation rates, was evaluated in a full-scale (3,000 m³) biopile study. A contaminated clayey sand soil with an average TPH content of 1,421?±?260 mg kg^?1 soil was treated in a biopile with a fixed venting and heating system. Temperature in the biopile ranged from 12.1 to 36.6°C and soil water content from 15.2 to 35.8 m³ H₂O m^?3 soil. Oxygen concentrations in the biopile showed a rapid decrease with depth, before venting and reached constant atmospheric concentration during venting. Measured oxygen consumption in the biopile ranged from ?0.04 to ?0.68 mol O₂ m^?3 soil day^?1. Average oxygen consumption rates calculated with the quasi-steady-state method were significantly (P?<?0.05) lower then the oxygen consumption rates calculated with the transient method. It was suggested that the oxygen diffusion was underestimated by the diffusivity models used and that further research is needed to determine relative effective diffusion coefficients in biopiles. Although both respiration testing and petroleum hydrocarbon concentration showed a decrease of oxygen consumption in time, the estimated degradation rate was low compared to the actual decrease in petroleum hydrocarbon concentration. Additional work will have to be done to acquire a more precise knowledge of the relationship between respirometrically determined degradation rates and the actual change in petroleum hydrocarbon concentration in the soil.     

Anthropogenic environmental impact in the Mediterranean coastal area of Koper/Capodistria,Slovenia

Purpose

Heavy metal content in soils could be a consequence of geogenic and different anthropogenic sources. In ancient times, soils in the Mediterranean region were affected by agriculture and viticulture, whereas more recently, industry and traffic might contribute more to their pollution. The aim of the study is to determine the extent of multisource heavy metal pollution in soils within the Koper area.

Materials and methods

Along the northern Adriatic Sea coast, around the port city of Koper/Capodistria, 24 topsoil samples were collected; sets of six samples representing four possible pollution sources: intensive agriculture, viticulture, port activities and industry. The parent material of the soil is mainly derived from the Eocene flysch weathered marls and calcarenites and the soil types are eutric. The chemical composition of the samples was determined by ICP-ES for oxides and several minor elements and by ICP-MS for heavy metals. The mineral composition of the selected samples was checked using X-ray powder diffraction. Different statistical analyses were performed on the normally distributed data.

Results and discussion

The mean concentrations of all samples are: Cr 215 mg kg^?1, Ni 81 mg kg^?1, Zn 67 mg kg^?1, Cu 44 mg kg^?1 and Pb and Co 18 mg kg^?1. The ANOVA showed significant differences only in CaO, C/TOT, P₂O₅, Co and Pb between those locations within reach of the different contamination sources. The observed average values of heavy metals are well below Slovenia’s Directive limit for Cu, Pb and Zn, close to but not above it for Co and above the action value for Cr and Ni. According to Igeo, soils from all the sampling locations are uncontaminated with Co, Ni and Pb, and uncontaminated to moderately contaminated with Cu and Zn at one port location, and with Cr at all locations.

Conclusions

The very high Cr and Ni levels could still be geogenic because soils developed on Eocene flysch rocks are enriched in both metals. Cr and Ni are not correlated because of their different levels of sorption and retention in carbonate soils. Cr was retained and concentrated in the sand fraction but Ni has been mobilised in solution. The only serious threat to the environment seems to be an illegal waste dumping area near the port.     

Growth promotion by sodium in amaranthaceous plants

The amaranthaceous dwarf glasswort, Swiss chard, table beet, spinach and Mexican tea were grown in solutions containing 0, 20, 40, 80, 120, 160, 180 and 200 mol m^?3 sodium chloride (NaCl). Maximum growth and increase of biomass production compared to that at 0 mol m^?3 of dwarf glasswort was observed at 200 mol m^?3 (245%), and Swiss chard (146%), table beet (128%) and spinach (138%) at 80 mol m^?3. The growth of these species increased with increasing sodium (Na) concentration of shoot until it reached 4.18, 2.42, 1.60 and 1.58 mol kg^?1, respectively. These indicate that the order of Na-loving character is dwarf glasswort >> Swiss chard > table beet = spinach. The water contents increased with increasing Na concentration until growth reached maximum in dwarf glasswort and Swiss chard. In these highly Na-loving species, Na is activity transported to shoots and utilized for producing osmotic pressure to absorb water.     

Earthworm activity alters geogenic arsenic and soil nutrient dynamics

Environmental pollution due to arsenic (As) has been well studied and most investigations have focused on inorganic As coming from industrial areas. However, the natural rock-borne contamination of this metalloid has been underestimated and few studies focusing on annelids have addressed the question of geogenic As distribution in earthworm biogenic structures. Our study concentrated on the earthworm drilosphere and investigated the distribution of As in surface-casts and burrow-linings. In this context, we assumed that the concentration of geogenic As should differ in biogenic structures (faeces, burrow-linings) compared to non-ingested soil. To test our hypothesis, microcosms in controlled conditions were filled with soil containing 157 mg As kg^?1 from a geogenic origin. The soil was collected from a meadow in the Jura Mountains. The earthworm Aporrectodea giardi was selected because of its natural presence in the meadow and its anecic behaviour.We found that while earthworm surface-casts were enriched in carbon, nitrogen and available phosphorus compared to non-ingested soil, no enrichment was found for geogenic arsenic. The coarse sand fraction contained 3.5 times more As than silt and clay fractions but no significant difference existed between surface-casts and non-ingested soil. Iron was shown to be the main mineral bearing phase for As and predominated in the coarse sand fraction. No retention effect of organic matter on geogenic arsenic was observed. In conclusion, it appeared that geogenic As did not affect biological components and environmental aspects. These findings are particularly encouraging considering that most of the environments at an altitude of 1330 m in the Jura Mountains have exposed rocks, especially on meadows that are regularly grazed by cattle.     

Bulk density and content,density and stock of carbon,nitrogen and heavy metals in vegetable patches and lawns of allotments gardens in the northwestern Ruhr area,Germany

Purpose

In view that soils are bodies and that processes such as storage and release of water, carbon, nutrients and pollutants, and aeration and rooting happen in these bodies, it is of interest to know the density of elements and compounds in soils. On the basis of soil bulk and element density of organic carbon (OC), N, and heavy metals in soils and of horizon thickness, stocks of these elements for garden soils were calculated.

Materials and methods

Fourteen gardens in four allotments of the northwestern part of the Ruhr area, Germany were investigated. The research included 14 vegetable patches, 13 lawns, 2 compost heaps, and 1 meadow. Volume samples were taken. The soil analysis included pH, soil bulk density, and OC, N, Pb, Cd, Zn, Cu, and Ni contents.

Results and discussion

The soils were from sandy loam to loamy sand. The pH was slightly acid and C/N ratio about 20. Soil bulk density was between 0.8 and 1.4 g cm^?3 and mean bulk density was 1.1 g cm^?3. Mean OC content was for compost 7.4 %, vegetable patches 5.2 % (0–30 cm depth), and lawns and meadow 5.8 and 5.2 % (0–5 cm depth). OC density for compost was 76 mg cm^?3, vegetable patches 56 mg cm^?3, and lawns 67 mg cm^?3 (0–5 cm). Mean OC stock in 0–30 cm soil depth in vegetable patches was 16.4 kg m^?2, lawns 15.5 kg m^?2, and meadow 11.1 kg m^?2. N contents were between 0.06 and 0.46 %. For compost, the mean was 0.39 %, vegetable patches 0.27 % (0–30 cm), lawn 0.28 %, and meadow 0.26 % (0–5 cm). Mean stock of N in 0–30 cm depth for vegetable patches was 0.84 kg m^?2, lawn 0.76 kg m^?2, and meadow 0.55 kg m^?2. For heavy metals in compost, vegetable patches, lawn and meadow, Cd contents were in the range of 1.7 to 3.0 mg kg^?1, Pb 49 to 152 mg kg^?1, and Zn 52 to 1830 mg kg^?1. The amounts stored per square meters in 30 cm depth were for Cd 0.6–1.1 g, Pb 15–52 g, Zn 41–440 g, Cu 4–39 g, and Ni 1–8 g.

Conclusions

Allotment gardens have a high capacity to store CO₂ as OC. Roughly, there will be 7–8 million tons of OC stored in the 1.3 million allotment gardens of Germany. The high amount of 8000 kg N ha^?1 could damage the groundwater when released by wrong soil management. Cd, Zn, Pb, Cu, and Ni amounts of 7.8, 1000, 300, 135, and 30 kg ha^?1, respectively, are a lasting burden.

     

Growth response of Suaeda salsa (L.) Pall to graded NaCl concentrations and the role of chlorine in growth stimulation

Abstract

Growth response of a halophyte species, Suaeda salsa (L.) Pall, to graded NaCl concentrations was examined under water culture conditions. Growth increased with increasing NaCl concentration from 2 to 200 mol m^?3, but decreased at NaCl concentrations above 200 mol m^?3. Maximum growth was attained at 50 to 200 mol m^?3. The role of Na and Cl in the growth stimulation by NaCl was examined by growing S. salsa in nutrient solutions with or without Na and Cl separately at 5 and 50 mol m^?3. The growth stimulation induced by Cl was greater than that induced by Na, and Na did not significantly induce growth stimulation. The effect of Na or Cl on O₂ evolution from leaves was examined under 5 and 50 mol m^?3 concentrations using an oxygen electrode. Oxygen evolution from leaves in –Cl treatments was smaller than that in +Cl treatments both at 5 and 50 mol m^?3. The O₂ evolution in Na treatments with Cl was similar to that at NaCl. These results indicated that the mechanism of growth stimulation induced by Cl was mainly an increased photosystem II of photosynthesis in leaves. The contribution of Na on the growth stimulation of S. salsa by NaCl was smaller than Cl.     

TREATED EFFLUENT AND SALINE WATER IRRIGATION INFLUENCES SOIL PROPERTIES,YIELD, WATER PRODUCTIVITY AND SODIUM CONTENT OF SNOW PEAS AND CELERY

To determine the effects of irrigation water quality, plants were irrigated with normal potable water [0.25 dS m^?1 electrical conductivity (EC), 25 mg L^?1 sodium (Na), 55 mg L^?1 chloride (Cl)], treated effluent (0.94 dS m^?1 EC, 122 mg L^?1 Na, 143 mg L^?1 Cl) and saline water with low salinity (1.24 dS m^?1 EC, 144 mg L^?1 Na and 358 mg L^?1 Cl) and high salinity (2.19 dS m^?1 EC, 264 mg L ^?1Na and 662 mg L^?1 Cl) for snow peas, and high salinity (3.07 dS m^?1 EC, 383 mg L^?1 Na and 965 mg L^?1 Cl) and very high salinity (5.83 dS m^?1 EC, 741 mg L^?1 Na and 1876 mg L^?1 Cl) for celery. The greater salts build up in the soil and ion toxicity (Cl and Na) with saline water irrigation contributed to significantly greater reduction in root and shoot biomass, water use, yield and water productivity (yield kg kL^?1 of water used) of snow peas and celery compared with treated effluent and potable water irrigation. There was 8%, 56% and 74% reduction in celery yield respectively with treated effluent, high salinity and very high salinity saline water irrigation compared with potable water irrigation. The Na concentration in snow peas shoots increased by 54%, 234% and 501% with treated effluent, low and high salinity saline water irrigation. Similarly, the increases in Na concentration in celery shoots were 19%, 35% and 82%. The treated effluent irrigation also resulted in a significant increase in soil EC, nitrogen (N) and phosphorus (P) content compared with potable water irrigation. The heavy metals besides salts build up appears to have contributed to yield reductions with treated effluent irrigation. The study reveals strong implications for the use of saline water and treated effluent for irrigation of snow peas and celery. The salt build up within the root zone and soil environment would be critical in the long-run with the use of saline water and treated effluent for irrigation of crops. To minimize the salinity level in rhizosphere, an alternate irrigation of potable water with treated effluent or low salinity level water may be better option.     

Properties and available micronutrient status of some soils derived from Abeokuta formation in Nigeria

Available iron, zinc, copper and manganese were determined in six pedons located in upper slope, middle slope and valley bottom soils derived from Abeokuta geological materials in Nigeria. The soils had an average of 639.8 g kg^?1 sand, 241.8 g kg^?1 clay and 118.4 g kg^?1 silt. The fertility status of the soils was low–medium with a strongly acid–neutral reaction, 1.3–15.1 g kg^?1 organic carbon contents, moderate–high exchangeable bases and 1.38 mg kg^?1 available phosphorus. Both Fe (122.50 mg kg^?1) and Mn (111.40 mg kg^?1) occurred at toxic levels, whereas the mean Cu (1.27 mg kg^?1) and Zn (2.56 mg kg^?1) contents were found to be adequate for most crops grown in the region. There were significant positive correlations among the micronutrients and also between soil pH, organic carbon, particle size fractions and micronutrients. The high levels of Fe and Mn were probably due to the presence of oolitic ironstone in the parent material.     

Imperata cylindrica (Cogongrass) as an Adsorbent for Methylene Blue Dye Removal: Process Optimization

A novel sorbent, chitosan-immobilized pumice, has been prepared for the sorption of As(V) from waters prior to its determination by hydride generation atomic absorption spectrometry. The success of the immobilization has been checked with such characterization techniques as scanning electron microscopy, thermal gravimetric analysis, and elemental analysis. Points of zero charge of the sorbents were determined with potentiometric mass titration. Batch-type equilibration studies have shown that the novel sorbent can be employed at a wide pH range resulting in quantitative sorption (>90 %) at pH 3.0–7.0 and greater than 70 % sorption at pH >8.0. These results demonstrate the advantage of immobilizing chitosan onto pumice, because, under the same conditions, pumice displays <20 % sorption toward As(V), whereas chitosan gives approximately 90 % sorption only at pH 3.0. The validity of the method was verified through the analysis of ultrapure, bottled drinking, and tap water samples spiked with arsenate; the respective sorption percentages of 93.2 (±0.7), 89.0 (±1.0), and 80.9 (±1.3) were obtained by batch-type equilibration. Arsenic sorption was also examined in the presence of common interfering ions resulting in competing effects of PO₄ ^3? and NO₃ ^? on As(V) adsorption.     

Growth Response and Selenium and Boron Distribution in Broccoli Varieties Irrigated with Poor Quality Water

Abstract

Selenium (Se), and boron (B), and salinity contamination of agricultural drainage water is potentially hazardous for water reuse strategies in central California. This greenhouse study assessed tolerance and Se, B, and chloride (Cl^?) accumulation in different varieties (Emerald City, Samurai, Greenbelt, Marathon) of broccoli (Brassica oleracea L.) irrigated with water of the following different qualities: (1) non‐saline [electrical conductivity (EC) of <1 dS m^?1]; (2) Cl^?/sulfate salinity of ～5 dS m^?1, 250 µg Se L^?1, and 5 mg B L^?1; and (3) non‐saline and 250 µg Se L^?1. One hundred and ten days after transplanting, plants were harvested and dry weight (DW) yields and plant accumulation of Se, B, and Cl^? was evaluated in floret, leaf, and stem. Irrespective of treatments floret yields from var. Samurai were the lowest among all varieties, while floret yields from var. Marathon was the only variety to exhibit some sensitivity to treatments. For all varieties, plant Se concentrations were greatest in the floret (up to 51 mg kg^?1 DW) irrespective of treatment, and B and Cl^? concentrations were greatest in the leaves; 110 mg B kg^?1 DW and 5.4% Cl^?, respectively. At post harvest, treatment 2 (with salinity, B, and Se) increased soil salinity to almost 6 dS m^?1, total Se concentrations to a high of 0.64 mg kg^?1 DW soil, and water soluble B concentrations to a high of 2.3 mg B L^?1; soluble Se concentrations were insignificant. The results indicate that var. Emerald City, Greenbelt, and Marathon should be considered as recipients of moderately saline effluent enriched with Se and B under field conditions.     

Short-term impact of a wildfire on net and gross N transformation rates

Wildfires often modify soil properties, including the N status and net N mineralization rates, but their impacts on gross N fluxes have been scarcely evaluated. We aimed to ascertain the immediate effects of a medium–high severity wildfire on soil N transformations. Net and gross N rates were analytically and numerically (FLUAZ) quantified in burned (BS) and unburned (US) topsoils from the temperate–humid region (NW Spain). Analytical and numerical solutions were significantly correlated for both gross N mineralization (m) (r ²?=?0.815; p?<?0.001) and gross nitrification (n) (r ²?=?0.950; p?<?0.001). In BS, all NH₄ ⁺-N fluxes (net m, gross m and gross NH₄ ⁺-N immobilization, ‘ia’) increased, while those of NO₃ ^?-N decreased (gross n and gross NO₃ ^?-N immobilization, ‘in’) or did not vary (net n). In US and BS, gross m (0.26–3.60 and 4.70–15.42 mg N kg^?1 day^?1, respectively) predominated over gross n (0.026–2.45 and 0.001–0.002 mg N kg^?1 day^?1, respectively), and the same was true for the net fluxes. Compared with the few available data on recently burned soils (m?=?8–55 mg N kg^?1 day^?1; n?=?0.50–1.83 mg N kg^?1 day^?1), our gross m and n rates were similar and very low, respectively; gross n showed that nitrifiers were active in US and also in BS, despite the 98 % reduction observed immediately after the fire. For gross fluxes, m increased more than ia suggesting an NH₄ ⁺-N accumulation, but there is no risk of NO₃ ^?-N leaching because n decreased more than in.     

Temporal change in soil macropores measured using tension infiltrometer under different land uses and slope positions in subtropical China

Purpose

Soil macropores play a principal role in water infiltration but they are highly variable. The objectives of this study were (1) to investigate the temporal change in macropores of an Ultisol as affected by land use and slope position and (2) to analyze contribution of macropores to water infiltration.

Materials and methods

Water infiltration was measured at upper and lower slopes in citrus orchard and watermelon field once every 2 months for 1 year using tension infiltrometers at a successive pressure head from ?12, ?6, ?3, to 0 hPa.

Results and discussion

Hydraulic conductivity (K) was significantly affected by land use and slope position except at 0 hPa pressure head, showing a significant temporal variation. Effective macroporosity, derived from the increment of hydraulic conductivity between ?3 and 0 hPa, showed a significant temporal variation. Such temporal variation was land use (P?<?0.05) and slope position (P?<?0.001) dependent. Despite of low proportion in total soil volume (averaged 3.5 cm³ m^?3), the macropores contributed 47 % of water flux on average. The macroporosity was more stable and higher in the citrus orchard (2.43 cm³ m^?3, coefficient of variance (CV)?=?75 %) than in the watermelon field (1.72 cm³ m^?3, CV?=?117 %) and contributed more to infiltration in the citrus orchard (60 %, CV?=?16 %) than in the watermelon field (33 %, CV?=?43 %) as well, because tillage was operated only in the watermelon field.

Conclusions

No-tillage increased water conducting macropores but did not increase hydraulic conductivity irrespective of slope position.