Effects of Linear Alkylbenzene Sulphonates (LASs) on Exogenous Organic Matter Content and Evolution in Sewage Sludge–Amended Soils

Abstract

Linear alkylbenzene sulphonates (LASs) are anionic surfactants commonly used in commercial detergents. A potential risk associated with the recycling of sewage waste materials is the presence of LASs and their primary degradation products, which could accumulate in sludge, especially during anaerobic processing. The long‐term accumulation of these contaminants in soils and especially the potential disturbance of soil functions need to be studied in more detail. In our study, the influence of the amendment added to an agricultural soil with different organic wastes containing LASs on organic matter content and nitrogen (N) content evolution and mineralization was studied in field conditions. A completely randomized 3×3 factorial arrangement, representing two sewage sludge types (composted and uncomposted) and three levels of LAS presence (0, 15, and 30 g/m²) in treated soils, was established using field plots (7×2 m); the results are compared with untreated plots. Statistical models based on covariance analysis were used to understand the dynamics of and the main factors influencing carbon (C) and N mineralization in sewage sludge amended–soils in the presence of LAS. LAS seemed to alter nitrogen mineralization, especially the nitrate dynamics.     

Quantification of Organic Matter in Agricultural Soils from the Central Region of Paraná State,Brazil

The organic matter (OM) quantity in soils is of fundamental importance for agriculture. The indirect determination of the OM through the Total Organic Carbon (TOC) quantity is performed by most soil laboratories in Brazil using the Walkley–Black (WB) method. This procedure involves oxidation with potassium dichromate which is a cancerous reagent. The objective of this study is to optimize the parameters for OM determination by the gravimetric method and to estimate the van Bemmelen factor for the studied soil. The studied region is the second and third plateau of Parana State, Brazil, from which 50 agricultural soil samples were analyzed. The temperature and exposition time in muffle were determined after a thermal analysis. The optimized parameters for the gravimetric method were 3 h at 420°C in the muffle furnace. The results for WB and gravimetric methods presented a good correlation and the van Bemmelen factor for the studied soil was 4.37.     

Changes in pH,CEC and Exchangeable Acidity of Some Forest Soils in Southern China During the Last 32–35 Years

Soil acidification has been occurred in two locations in southern China. The changes in soil pH during a 35 yr period has been about 1.0 pH ₂O) units, and about 0.58–0.71 pH (KCl) units at Wuming in Guangxi Zhuang Autonomous Region and Zhurongfeng of Mt. Heng in Hunan Province. A decrease in CEC and BS and an increase in hydrogen and aluminum ion concentrations were found in the acidified soils, and related to the acidification caused by acid deposition. Hydrogen ion concentration increased about 0.1–1.0 × 10^-6 equivalent g^-1 soil yr^-1. Cation exchangeable capacity (CEC) and base saturation (BS) decreased to 53–76 and 30–59% in the acidified soils respectively, and an increase in exchangeable acidity also occurred. Acidification in the topsoil is higher than in the subsoil.     

Influence of Dissolved Organic Matter on the Solubility of Heavy Metals in Sewage‐Sludge‐Amended Soils

Abstract

Sewage‐sludge‐amended soils generally contain elevated levels of organic matter and heavy metals compared to control soils. Because organic matter is known to complex with heavy metals, the solubility behavior of the organic matter in such soils may exert a significant influence on the solubility of the metals. Little is known about such a process. Using batch experiments in which the solubility of organic matter in a heavily sludge‐amended soil was artificially manipulated, we show that the solubilities of the heavy metals copper (Cu), nickel (Ni), and lead (Pb) show a strong positive relationship to the solubility of organic matter, particularly at high pH. The results suggest that under field conditions, spatiotemporal variations in the solid–solution partitioning of organic matter may have a bearing on the environmental significance (mobility and bioavailability) of these heavy metals.     

Influence of Organic Manure on Organic Phosphorus Fraction in Soils

The transformation of organic P(Po) from organic manures in two types of soils (ultisol and entisol) and the influences of external addition of organic substance or inorganic P(Pi) on Po under the condition of the 60% maximum water capacity were investigated.The results obtained from Po fractionation experiments indicated that all the Po fractions except for the highly resistant Po fraction decreased during incubation.Application of pig feces and cow feces could largely increase each fraction of Po in the soils.Immediately after application of organic manure into the soils a large part of labile and moderately labile Po from organic manure was transferred into moderately resistant Po,which might be due to the fact that Ca-or Mg-inositol P was precipitated into Fe-inositol P.However,the availability of Po from organic manure in the soils would increase again after incubation because of the transformation of moderately labile and resistant Po fractions into labile Po fractions.Addition of cellulose or Pi into the soils showed a good effect on increasing all the Po fractions except for the highly resistant Po,and this effect was much more pronounced when cellulose was applied in combination with Pi.Therefore,in view of the effect of organic manure on improving P nutrition to plant,attention should be paid to both the Po and the organic substances from organic manure,It is suggested that application of Pi fertilizer combined with organic manure may be referred to as an effective means of protecting Pi from chemical fixation in soil.     

Effect of Organic Matter and Salinity on Ethylenediaminetetraacetic Acid–Extractable and Solution Species of Cadmium and Lead in Three Agricultural Soils

Abstract

A study was conducted to investigate the chemical speciation of added cadmium (Cd) and lead (Pb) and their availability as influenced by fresh organic matter (OM) and sodium chloride (NaCl) in three agricultural soils. The soils were treated with 20 mg Cd/kg as cadmium nitrate [Cd(NO₃)₂ · 4H₂O], 150 mg Pb/kg as lead nitrate [Pb(NO₃)₂], 20 g/kg alfalfa powder, and 50 mmol/kg of NaCl and then incubated for 3 months at 60% water‐holding capacity (WHC) and constant temperature (25 °C). Subsamples were taken after 1, 3, 6, and 12 weeks of incubation, and electrical conductivity (EC), pH, dissolved organic carbon (DOC), and concentrations of cations and anions were determined in the 1:2.5 soil/water extract. Available Cd and Pb were determined in 0.05 M ethylenediaminetetraacetic acid (EDTA) extract. Concentrations of organic and inorganic species of Cd and Pb in soil solution were also predicted using Visual Minteq speciation program. The most prevalent species of dissolved Pb and Cd in the soils were Pb‐DOC and Cd²⁺ species, respectively. Salinity application increased the available and soluble Cd significantly in the acid and calcareous soils. It, however, had little effect on soluble Pb and no effect on available Pb. Organic‐matter application decreased availability of added Pb significantly in all soils. In contrast, it raised soluble Pb in all soils except for the acid one and approximated gradually to the added Pb with time. Impact of OM on available Cd was somewhat similar to that of Pb. Soluble Cd increased by OM application in the calcareous soil, whereas it decreased initially and then increased with time in the other soils.     

Changes in the Degree of Contamination of Organic Horizons of Al–Fe-Humus Podzols upon a Decrease in Aerotechnogenic Loads,the Kola Peninsula

Contamination levels of the organic horizon of Al–Fe-humus podzols (Albic Rustic Podzols) in the zone affected by atmospheric emissions of the Severonikel smelter (Murmansk oblast) within a 20-yearlong period are compared. The spatiotemporal changes in the total content of heavy metals in the soils in response to a decrease in aerotechnogenic loads have a complicated pattern. As the content of heavy metals in the soils varies widely, the correlation between their amount in the organic soil horizon and the distance from the contamination source is absent. In response to the ninefold decrease in the amount of atmospheric emission of Ni compounds, the bulk content of Ni in the organic horizons of podzols reliably decreased by 2.5 times. The threefold decrease in the emission of Cu compounds proved to be insufficient for a significant decrease in the Cu content in the soils. In 2016, the content of heavy metals in some sampling points even increased in comparison with the earlier periods. The Ni-to-Cu ratio in the soil samples changed significantly. In 1989–1994, bulk forms of heavy metals in the soil samples formed the sequence Ni > Cu > Co; in 2016, it changed to Cu > Ni > Co, which corresponds to the proportions of these metals in the aerial emissions. Under conditions of the continuous input of heavy metals from the atmosphere, the contamination of the organic horizons of podzols with heavy metals remains at the high or very high levels.     

Capability of Loss‐on‐Ignition as a Predictor of Total Organic Carbon in Non‐Calcareous Forest Soils

Abstract

Accurate analyses of large numbers of soil samples are needed in order to reduce the uncertainty of carbon inventories. Loss‐on‐ignition (LOI) is still considered the most convenient assessment method, but its accuracy and precision for predicting total organic carbon (TOC) is questioned. However, our estimation of measurement precision for different samples showed comparable relative standard deviations (RSDs) for LOI and TOC determinations. Highest precision was found in forest floor samples (RSD<1.2%) and lowest (RSD 5–10%) in sandy soil samples low in organic matter. Forest floor samples (n=66) and non‐calcareous mineral soil samples (n=654) were used to calibrate and validate predictive equations. Excellent linear relationships were found. For a wide range of soils the bivariate predictive equation TOC=?0.1046 Clay+0.5936 LOI (r²=0.98) was developed and validated. After correction for clay content, slopes averaged remarkably close to the traditional 0.58 conversion factor.     

Tillage Effects on Particulate and Mineral‐Associated Organic Matter in Two Tropical Brazilian Soils

Abstract

Two Ferralsols (350 and 600 g kg^?1 clay) from the Brazilian Cerrado Region were evaluated for long‐term effects (5 and 8 years) of no tillage on carbon (C) stocks in particulate (>53 µm) and mineral‐associated (<53 µm) soil organic matter (SOM) fractions. Carbon stocks in particulate SOM increased under no tillage compared with conventional tillage, and the rate was higher in the clayey soil (0.62 Mg C ha^?1 yr^?1) than in the sandy clay loam soil (0.31 Mg C ha^?1 yr^?1). In contrast, the mineral‐associated SOM in the top soil layer (0–20 cm) was not affected by tillage system. Sequestration of atmospheric C in tropical no‐tillage soils seems to be due to accumulation of C in labile SOM fractions, with highest rates in clayey soils probably due to physical protection.     

Is the Walkley–Black Method Suitable for Organic Carbon Determination in Chilean Volcanic Soils?

Although dry combustion (DC) carbon dioxide (CO₂) is an accurate method to measure total soil carbon (C), it is a rather expensive one. Therefore, wet oxidation by the Walkley–Black (WB) method is widely used in acidic Chilean volcanic soils, although there are no studies comparing both WB and DC. The aim of this article was to compare DC and WB in a range of volcanic soils containing between 2% and 9% of soil C on a regional scale. Results indicated that the recovery (R) of soil C by WB with respect to DC varied between 70% and 82%. Consequently, the correction factor (100 / R) ranged between 1.26 and 1.47. The standardized major axis regression analysis indicated that the slope and the intercept of the fitted line on volcanic soils were similar to 1:1 line. In conclusion, WB was an economically suitable method to determine the soil C content of Chilean volcanic soils.     

Soils оf Oligomesotrophic аnd Mesotrophic Bogs in the Boreal Zone of West Siberia: Possibilities of Botanical Diagnostics within the Framework of the Type of Mesotrophic Peat Soils

Eurasian Soil Science - Despite the widespread use of the taxon “mesotrophic (transitional) peat soils” in the present-day Russian and foreign pedology, including some fundamental...     

Soil Formation in the Taiga–Steppe Ecotone of the Selenga Mountains,Western Transbaikal Region

Eurasian Soil Science - A new view on the genesis and properties of soils in landscapes of the taiga–steppe ecotone in the Selenga Mountains of western Transbaikalia is suggested with due...     

Loss‐on‐Ignition in the Determination of Pools of Organic Carbon in Soils of Forests and Afforested Arable Fields

Abstract

Loss‐on‐ignition (LOI) and concentration of organic carbon (Cc) were determined on pristine forest soils and soils from afforested arable fields. The objectives were to investigate the relation between the Cc of soil estimated indirectly from LOI and true Cc from dry combustion (C_LECO) and further to evaluate how the applied analytical method affects the carbon pool estimates. According to results, LOI was a good indicator of Cc in the organic layer. As regards mineral soil, however, C_LECO/LOI ratio significantly decreased with increasing depth, and the ratio changed differently in soils underlying forest sites as opposed to the soils from former fields. The results indicate that estimation of carbon pools from conversion factors would lead to considerable bias and that direct measurement of Cc is preferable to the use of any Cc/LOI ratio. The results also emphasize the need for elimination of carbonate carbon when measuring Cc from the soil of arable fields.     

Screening of Seven Plant Species for Short‐Term Improved Fallows in the Humid Forest Zone of Cameroon

Seven short‐fallow plant species were evaluated for their aboveground biomass production, nutrient accumulation, and weed suppression potential in Nkolbisson, Cameroon. The fallow species included Arachis pintoi, Vigna radiata, Desmodium intortum, Centrosema pubescens, Indigofera hirsutus, Indigofera spicata, and Pueraria phaseoloides. The experimental design was a randomized complete block with four replications and seven treatments (fallow species). Twelve months after planting, highly significant differences (p < 0.01) were observed among fallow species for phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentrations, respectively, in plant tissue. Similarly, highly significant differences (p = 0.0013) occurred among fallow species for aboveground biomass production, which ranged between 3.12 t ha^?1 (I. spicata) and 9.16 t ha^?1 (A. pintoi). Potassium only showed highly significant differences among plant species for nutrient accumulation (p = 0.0001). However, A. pintoi, C. pubescens, I. hirsutus, and P. phaseoloides yielded substantial amounts of recycled N (>100 kg ha^?1 year^?1) that can benefit the subsequent crop. For small‐scale producers, these species are likely to supply adequate nitrogen for cereal crops. A total of 26 weed species belonging to 15 botanical families were encountered in the various plots. Weed dry weight differed significantly (p = 0.02) among the fallow plots and ranged from 0.12 t ha^?1 (in P. phaseoloides plots) to 2.32 t ha^?1 (in A. pintoi plots). Results of this study suggest that there are a wide range of plant species that could be used in improved fallow technologies aimed at improving nutrient‐degraded soils and suppressing weeds.     

Measurement of Cation Exchange Capacity of Organic‐Matter Fractions from Soils using a Modified Compulsive Exchange Method

Abstract

This article describes a modified compulsive exchange method suitable for the determination of cation exchange capacity (CEC) over a pH range on solid, separated organic‐matter fractions. The method is demonstrated to be a reproducible and relatively simple means of measuring CEC on fractions separated by physical means in conjunction with hydrofluoric acid (HF) treatment. By including a modification for measuring the residual magnesium (Mg²⁺) content by dilution and conductivity, the method is simplified to measure CEC versus pH using a single sample; the only laboratory instruments required are pH and conductivity meters and a balance. The lack of agreement between this method and the silver thiourea (AgTU) method for some fractions at low pH is attributed to the uncontrolled variation in solution ionic strength when acid is introduced to effect solution pH changes in the AgTU method.     

Dissolved Organic Matter (DOM) in Acid Forest Soils at Gådsjön (Sweden): Natural Variabilities and Effects of Increased Input of Nitrogen and of Reversal of Acidification

Effects of (1) the addition of 35 kg N ha^-1yr^-1(as NH₄NO₃) and (2) interception of throughfall and litterfall by means of a roof on concentrations, chemical characteristics and dynamics of dissolved organic matter (DOM) in acid forest soils (podzols) were studied at Gårdsjön, Sweden. A non-manipulated catchment served as a reference. After 4 yr of treatment no significant effects of either manipulation were found on concentrations and characteristics of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). The variability of these parameters within catchments appeared to be of the same order of magnitude as the variability between catchments. At all sites, DON contributed more than 70% of the total dissolved nitrogen. In general, the proportion of hydrophilic DOC increased with depth. In contrast, to other studies the C/N ratio of DOM at Gårdsjön did not show a clear pattern with depth. Other studies in SE U.S.A. have suggested that relatively low C/N ratios at depth are due to increased contribution of hydrophilic neutrals to DOC. However, this fraction appears to be small in temperate and boreal spruce forest soils, including Gårdsjön.     

Organic Matter of the Air-Dry and Water-Stable Macroaggregates (2–1 mm) of Haplic Chernozem in Contrasting Variants of Land Use

Eurasian Soil Science - The content and the composition of soil structural units of different hierarchical levels were studied for Haplic Chernozems (Loamic, Pachic) of Kursk region under...     

Composition and Characteristics of Organo—Mineral Complexes of Red Soils in South China

The objective of the present study is to reveal the composition and characteristics of organo-mineral complexes in red soils (red soil,lateritic red soil and latosol) of south China in terms of chemical dissolution and fractional peptization methos.In the combined humus,most of the extractable humus could dissolve in 0.1 M NaOH extractant and belonged to active humus (H1),and there was only a small amount of humus which could be further dissolved in 0.1 M Na4P2O7 extractant at pH 13 and was stably combined humus (H2).The H1/H2 ratio ranged from 3.3 to 33.8 in red soils,and the proportions of both H1 and total extractable organic carbon (H1 H2) in total soil organic carbon and the ratios of H1 to H2 and H1 to (H1 H2) were all higher in lateritic red soil and latosol than in red soil.The differences of combined humus composition in various red soils were directly related to the content of Fe and Al oxides.In organo-mineral complexes,the ratio of Na-dispersed fraction (G1) to Na-ground-dispersed fraction (G2) was generally smaller than 1 for red soils,but there was a higher G1/G2 ratio in red soil than in lateritic red soil and latosol.G1 fraction had a higher content of fulvic acid (FA),but G2 fraction had a higher content of humic acid (HA).The ratios of H1 to H2 and HA to FA were higher in G2 than in G1.The differences in the composition and activity of humus between G1 and G2 fractions were related to the content of free Fe and Al oxides.The quantities of complex Fe and Al,the Fe/C and Al/C atomic ratios were higher in G2 than in G1,and the ratio of Al/C was much higher than that of Fe/C.It may be deduced that aluminum plays a more important role than iron in the formation process of organo-mineral complexes in red soils.     

Enhanced Phosphorus Fertilizer (Carbond P®) Supplied to Maize in Moderate and High Organic Matter Soils

Carbond P (CBP) fertilizer often increases P uptake and crop yields in low P and organic matter soils. A glasshouse study was conducted with maize (Zea mays L.) grown in moderate or high organic matter soil with 0, 5, 15, 45, or 135 kg phosphorus pentoxide (P₂O₅) ha^?1 applied as either ammonium polyphosphate (APP) or CBP. In the high organic matter soil, both CBP and APP fertilization resulted in similar increases in biomass yield and P concentration and uptake. This was also observed in the moderate organic matter soil for maize P concentration, but biomass yield and total P uptake were significantly greater for CBP than APP at the two lowest P rates of fertilization and significantly higher for APP than CBP at the highest P application rate. The presence of high organic matter in the soil seemed to negate the effects of the organic acid bonded P found in CBP.