Mutagenic potential of municipal sewage sludge amended soils

This study was conducted to measure the mutagenic potential of municipal sewage sludge amended soil. Two separate sludge samples were collected from one municipal wastewater treatment plant and applied to undisturbed soil lysimeters over a 9 mo interval. Soil and sludge samples were collected for approximately 2 yr following sludge application. Samples were solvent extracted using methylene chloride and methanol, and the bacterial mutagenicity of the resulting residue determined using the Salmonella/microsome assay. The maximum specific activity of the sludge amended soil was 416 net revertants per 10 mg of residue induced by the methanol fraction extracted from the Weswood soil collected 154 d following the first sludge application. In the Padina sand, the maximum specific activity was 320 net revertants per 10 mg of residue induced by the methanol fraction extracted from the sample collected 154 d following the first sludge application. The specific activity of the sludge amended soil was observed to decrease slowly with time. For both the Padina and the Weswood soils, mutagenic organic chemicals were detected in soil samples collected 510 d following the second sludge application. For the Weswood soil, the mutagenic activity per unit weight of soil with metabolic activation of the samples collected 510 d after the final sludge application was decreased by 15 and 76% for the methylene chloride and methanol fractions, respectively, when compared to the maximum weighted activity observed 56 d after the final sludge application. The results indicate that municipal sewage sludges may contain organic mutagens which are persistent in the soil.     

Biodegradation of estrone and 17 β-estradiol in grassland soils amended with animal wastes

The release of endocrine disrupting chemicals into the environment is of increasing concern due to the formation of an intersex state in freshwater organisms and potential risks to human health. The aim of this study was to investigate the persistence of the naturally occurring hormones, estrone and 17 β-estradiol in three agricultural grassland soils in the presence and absence of cattle and sheep wastes (urine and manure). Biodegradation was investigated using ¹⁴C-labelled hormones which were applied to soil in three different solvents (water, artificial urine and natural sheep urine). When applied directly to soil the two hormones degraded at a similar rate, however, the speed of mineralization was soil type and solvent dependant. The half-life (t_1/2) of the hormones in soils ranged from 5 to 25 d. The hormones were also applied to the soils in sheep and cattle manure of different ages (7 d to 2 yr). Generally, the rate of degradation in the animal manure amended soils was more rapid than in the unamended soils (t_1/2=1-9 d), with mineralization being largely independent of manure age and type. We conclude that in comparison to many xenobiotics, estrogens are not persistent in agricultural soils. However, our calculations suggest that if they are lost to freshwater via runoff or leaching then they may have an appreciable effect on freshwater organisms. Assuming normal landspreading rates our results suggest that the risk of estrogen contamination of freshwater associated with manure spreading is very low.     

Arylsulphatase activity in soils amended with crop residues: Kinetic and thermodynamic parameters

Laboratory experiments were performed to determine the Michaelis-constants (K_m values) and maximum reaction velocities (V_max values) of arylsulphatase in a clay-loam and a sandy clay-loam soil. When crop residues were buried in either soil, the K_m and V_max values were altered markedly; the changes depended not only on the soil properties but also on the type of crop residue incorporated in the soils. This was confirmed at various temperatures, and data obtained were used to calculate the activation energies (E_a), and changes in enthalpy (ΔH_a) and entropy (ΔS_a) of activation. Whereas these properties were also affected by incorporating crop residues, the free energies of activation (ΔG_a) values, were similar in both soils and derived soil samples.     

Impact assessment of soils treated with refinery effluent

The effluent collected from the Panipat oil refinery was analysed for different physico-chemical properties. The systematic investigations were carried out to evaluate the effect of refinery effluent on soil fertility by assessing its impact on various soil physico-chemical and biological properties temporally using pot culture experiments. Different concentrations of effluent viz. control, 25%, 50%, 75%, 100% were used for the study. It was observed that application of effluent significantly increased pH, EC, TH, TDS, Ca²⁺, Mg²⁺, alkalinity, Cl^?, SO₄^2?, Fe, P, Na, K, heavy metals, soil dehydrogenase activity and organic content of soil during all intervals of time except bulk density and specific gravity. On the basis of the study it may be suggested that use of treated oil refinery effluent has no adverse effects on physico-chemical properties of soil and can also be used as an alternate source for irrigating crops as it increases the nutrient content of the soil which is essential for the proper growth and maintenance of crop plants.     

Nitrification in three soils amended with zinc sulfate

Zinc as ZnSO₄ was added to three soils at rates of 0, 10, 100 and 1000 μg Zn g^?1 soil. The soils were uniformly treated with 100 μg Ng^?1 as nh₄cl, incubated at 30°C and NH₄⁺-N and (NO₃^? + NO₂^?)-N determined weekly for 7 weeks. Nitrification in all three soils was totally inhibited by 1000 μg Zn g^?1. At the 100 μg Zn g^?1 rate, nitrification was significantly reduced in two of the three soils during some part of the incubation. This differential effect on nitrification at the 100 μg Zn g^?1 rate was related to differences in soil properties. These results imply that, with respect to nitrification, care should-be taken not to apply Zn-containing materials indiscriminately to soils.     

Sorption of the herbicide terbuthylazine in two New Zealand forest soils amended with biosolids and biochars

Background, aim, and scope  

Terbuthylazine is one of the most commonly used herbicides for vegetation management in forest plantations in New Zealand. Knowledge about the sorption of terbuthylazine on forest soils, especially the influence of coexisting organic amendments, remains obscure. In this study, we evaluated the effects of biosolids and biochars on the sorption of terbuthylazine to forest soils.     

Microbial and enzyme activity in soils amended with a natural source of easily available carbon

The addition of sugar beet to soils as a source of C led to an increase in the availability of easily utilizable C (glucose), which in turn markedly increased numbers of soil bacteria and of the yeast Williopsis californica. Nitrification, P solubilization, urea hydrolysis (and the subsequent nitrification of liberated NH _inf4 ^sup+ ) were stimulated by this amendment. The stimulation of nitrification may have been a result of increased heterotrophic nitrification. In contrast, the concentration of sulphate in S^o-amended soils declined following amendment, presumably as the result of enhanced S immobilization. Activity of the enzymes amylase, aryl sulphatase, invertase, phosphatase, dehydrogenase, and urease were all stimulated by the sugar beet amendment. These results suggest that sugar beet amendment could be used to increase the rate of release of plant-available ions from fertilizers such as insoluble phosphates. Problems may arise, however, from a subsequent increase in nitrification and reduced sulphate availability.     

Phosphorus availability in soils amended with wheat residue char

Plant availability and risk for leaching and/or runoff losses of phosphorus (P) from soils depend among others on P concentration in the soil solution. Water-soluble P in soil measures soil solution P concentration. The aim of this study was to understand the effect of wheat residue char (biochar) addition on water-soluble P concentration in a wide range of biochar-amended soils. Eleven agricultural fields representing dominant soil texture classes of Swedish agricultural lands were chosen. Concentrations of water-soluble P in the soils and in biochar were measured prior to biochar incorporation to soils in the laboratory. Experiments with three dominant soil textures—silt loam, clay loam, and an intermediate loam soil with different rates of biochar addition (i.e., 0.5, 1, 2, and 4 %; w/w) showed that the highest concentration of water-soluble P was achieved at an application rate of 1 %. At higher application rates, P concentrations decreased which coincided with a pH increase of 0.3–0.7 units. When the 11 soils were amended with 1 % (w/w) biochar, water-soluble P concentrations increased in most of the soils ranging from 11 to 253 %. However, much of the water-soluble P added through the biochar was retained (33–100 %). We concluded that wheat residue char can act as a source of soluble P, and low and high additions of biochar can have different effects on soil solution P concentration due to possible reactions with Ca and Mg added with biochar.     

Heavy metals in mine soils amended with sewage sludge

In order to reclaim a clay quarry, a topsoil material was mixed with gravelly spoil at different ratios and with various rates of sewage sludge. The influence of three spoil/topsoil ratios (1:1, 2:1 and 3:1) and three sludge rates (40, 80 and 120 t ha⁻¹) on chemical properties of the resulting material was investigated, with emphasis on heavy metal (Fe, Cu, Mn, Ni and Zn) contents. The mixtures topsoil/spoil/sludge were water saturated and incubated for 15 or 30 days in a chamber under controlled conditions. The incubated samples were analysed for pH, total carbon and nitrogen, and total, available, exchangeable and soluble heavy metals. The addition of spoil to the topsoil increased the volume of material available, by utilizing an inert material unsuitable by itself to grow plants. The addition of sewage sludge repaired the disadvantages of the spoil, increasing the pH and the organic matter contents. The total heavy metal contents in the mixtures followed the sequence Fe>>Mn>>Zn, Cu>Ni. All except Cu were within the ranges allowed for agricultural lands. The available heavy metals constituted a small fraction of total contents and decrease with time due to complexation and immobilization processes. The exchangeable and soluble fractions were almost negligible; only small amounts of Mn, Zn and Cu were detected. Therefore, the risk of contamination by heavy metals is insignificant in the conditions investigated. Copyright © 1999 John Wiley & Sons, Ltd.     

Sorption and desorption behaviors of diuron in soils amended with charcoal

Charcoal derived from the partial combustion of vegetation is ubiquitous in soils and sediments and can potentially sequester organic contaminants. To examine the role of charcoal in the sorption and desorption behaviors of diuron pesticide in soil, synthetic charcoals were produced through carbonization of red gum (Eucalyptus spp.) wood chips at 450 and 850 degrees C (referred to as charcoals BC450 and BC850, respectively, in this paper). Pore size distribution analyses revealed that BC850 contained mainly micropores (pores approximately 0.49 nm mean width), whereas BC450 was essentially not a microporous material. Short-term equilibration (< 24 h) tests were conducted to measure sorption and desorption of diuron in a soil amended with various amounts of charcoals of both types. The sorption coefficients, isotherm nonlinearity, and apparent sorption-desorption hysteresis markedly increased with increasing content of charcoal in the soil, more prominently in the case of BC850, presumably due to the presence of micropores and its relatively higher specific surface area. The degree of apparent sorption-desorption hystersis (hysteresis index) showed a good correlation with the micropore volume of the charcoal-amended soils. This study indicates that the presence of small amounts of charcoal produced at high temperatures (e.g., interior of wood logs during a fire) in soil can have a marked effect on the release behavior of organic compounds. Mechanisms of this apparent hysteretic behavior need to be further investigated.     

Potassium is responsible for salinity in soils amended with poultry manure

Abstract

Soil salinity increases when heavy rates of poultry manure are applied to sandy coastal plain soils. Analysis of soils involved in a poultry manure study during 1970, 1971 and 1972 has shown that soil salinity is primarily associated with a high concentration of ? in the soil solution. Although concentrations of other elements increased with the application of poultry manure also, the increases were not sufficient to account for the salinity in these soils.     

Microbial biomass C- and N-dynamics in grassland soils amended with liquid manure

Turnover and fluxes of C and N through microbial biomass were investigated on a research site in the grassland region of southwestern Germany. For a period of twelve months, biomass C was determined every 2 weeks and biomass N every 4 weeks (Fumigation-Extraction). This was done at fertilized plots as well as on plots, which had not been fertilized for eight years. Biomass C and N accounted for 1.5–7.5% of the soil C and 2–9% of the soil nitrogen. Unfertilized plots contained more biomass C and N than fertilized plots. No seasonal influence on the amount of the microbial biomass was visible. C/N ratios were not related to fertilization events. An increase of the C/N ratio with depth suggests a dominance of fungi in the subsurface horizons. Estimates of biomass C and N turnover were calculated by dividing the total measured losses of biomass by the average quantity of biomass present (McGill et al., 1986), annual fluxes of carbon and nitrogen were calculated by dividing annual mean C(N) by the average C(N) in biomass (Jenkinson and Ladd, 1981). Average turnover rates for biomass C varied between 1.4 and 4.5 a^?1, turnover rates for nitrogen were slower (1.2–3.3 a^?1). Carbon Ruxes through the microbial biomass range from 5000 to 8000 kg ha^?1 a^?1, while nitrogen fluxes range from 400 to 700 kg ha^?1 a^?1.     

Soil water relations of a Nigerian typic haplustult amended with fresh and burnt rice-mill wastes

The soils in the Abakaliki agro-ecological region of southeastern Nigeria are plagued with characteristics that impede optimal soil water conditions. Four rates (12.5, 25.0, 37.5 and 50.0 Mg ha⁻¹) of fresh (FW) and burnt (BW) rice-mill wastes were incorporated in a typic haplustult planted with maize (Zea mays L.) to improve the immediate and long-term water conditions of the soil. Results showed that significant changes in bulk density and total porosity occurred at the application rates of 25.0 and 50.0 Mg ha⁻¹ in the FW and BW amendments, respectively. At an application rate of 50.0 Mg ha⁻¹, the permanent wilting point water content (18.0%) in the FW amendment was significantly higher than the BW amendment. Similarly, the FW amendment at the same application rate resulted in the infiltration rates (i) of 2250 and 2181 mm h⁻¹ in the first and second seasons, respectively. These figures are significant improvements relative to the BW amendments and the control. Percent organic carbon (OC), dry aggregate size >0.5 mm and water stable aggregates (WSA) > 0.5 mm accounted for 43% and 77%, respectively of the improved infiltration. Sorptivity and A parameter of Philip's equation increased significantly with increasing rate of the FW amendment. Appropriate moisture conservation techniques are required to accelerate the rate of decomposition of the FW amendment in order to enhance its contribution to soil water retention.     

Carbon mineralization in an arid soil amended with organic wastes of varying degrees of stability

Abstract

This work investigated the kinetics of carbon (C) mineralization when different doses of organic materials with varying degrees of stability were added to an arid soil. Respiration assays showed that the incorporation of wastes led to a greater emission of carbon in the form of CO₂ and greater degree of microbial activity than those occurring in the control soil. Soils treated with fresh waste (municipal solid waste and sewage sludge) gave off more CO₂ than that treated with compost, with higher values being obtained at high than at low doses. Carbon dioxide emission was reduced with the length of time the organic materials remained in the soil. The data of cumulative CO₂ were fitted to the equation C=C₀(1‐e^‐Kt)+C₁. The parameters derived from this model were used as indices of organic matter decomposition, because the product of C₀ and K was more precise than either value separately. In all cases, an initial rapid phase of mineralization was clearly differentiated from a second slower phase.     

Nitrogen mineralization dynamics in acid vineyard soils amended with bentonite winery waste

An excess of available nitrogen (N) in vineyard soil is considered detrimental for vine growth, making a thorough assessment of N mineralization dynamics in vineyard soils before the addition of winery waste necessary. This study assesses the changes in N mineralization in acid vineyard soils amended with bentonite winery waste (BW). Non-amended soil (control), BW and soil-waste mixtures (SBWM) with a low (+L) or high (+H) dose of BW were incubated for six weeks. After 7, 14, 21 and 42 days of incubation, the control soils, BW and SBWM were analysed for net ammonified N, net nitrified N and net mineralized N. Parameters related to the kinetics of N mineralization were also determined. The addition of BW increased the potentially mineralizable N (N₀) in the amended soils (58–144% for the highest BW dose), although the mineralization rate was governed by the soil characteristics. Mineralizable N was only a small fraction (<4%) of the total organic nitrogen added to the soil through the BW addition, mainly due to the dominance of the nitrification process in the BW amended soils. These experimental results suggest that the addition of BW may be a suitable amendment for nitrogen fertilization in acid vineyard soil.     

Availability of triazine herbicides in aged soils amended with olive oil mill waste

Amendments are frequently added to agricultural soils to increase organic matter content. In this study, we examined the influence of alperujo, an olive oil mill waste, on the availability of two triazine herbicides, terbuthylazine and atrazine, in two different sandy soils, one from Sevilla, Spain, and the other from Minnesota. The effect of aging on herbicide sorption and bioavailability was also studied. Soils were amended with alperujo at a rate of 3-5% (w:w) in laboratory studies. Apparent sorption coefficients for the triazine herbicides were calculated as the ratio of the concentrations of each herbicide sequentially extracted with water, followed by aqueous methanol, at each sampling time. These data showed greater sorption of terbuthylazine and atrazine in amended soils as compared to nonamended soils, and an increase in the amount of herbicide sorbed with increasing aging time in nonamended soils. The triazine-mineralizing bacterium Pseudomonas sp. strain ADP was used to characterize triazine bioavailability. Less mineralization of the herbicides by Pseudomonas sp. strain ADP was observed in soils amended with alperujo, as compared to the unamended soils, and, despite the increase in sorption with aging in unamended soils, herbicide mineralization also increased in this case. This has been attributed to Pseudomonas sp. strain ADP first using alperujo as a more readily available source of N as compared to the parent triazines. In summary, addition of alperujo to the soils studied was shown to increase triazine herbicides sorption and hence to reduce its availability and potential to leach.     

Distribution of inorganic constituents in soil following land treatment of refinery wastes

To assess the impact of long term land treatment, soil profile samples were collected from treated and untreated sites at five refinery land treatment facilities. All samples were analyzed for texture, cation exchange capacity (CEC), specific conductance (EC), Na saturation (ESP), Na absorption ratio (SAR), pH, As, Cd, Cr, Hg, Pb, Ni, and V. Data show that land treatment of refinery waste had no effect on soil texture or CEC. Some sites showed small increases over background EC values of the surface 30 cm of soil. Depending on the waste characteristics and management practices, the soil pH may increase or decrease as a result of land treatment of refinery waste. Only one site was found with coil pH less than 6.5. At this site, Cr and Pb were detected below the zone of incorporation at concentrations above untreated soil. However, metal levels within the zone of incorporation at all sites remained within the ranges considered common for natural soil.     

Differential leaching of cations and sulfate in gypsum amended soils

Abstract

An adequate supply of available Ca in the soil solution of the pegging zone during fruit development is required for production of high yields of high quality peanuts (Arachis hypogaea L.). On low Ca soils, application of gypsum during early bloom is recommended in order to ascertain adequate availability of Ca. Reaction of gypsum in soils under leaching conditions vary considerably and play an important role in fruit development and yield of peanuts. A laboratory study was conducted in leaching soil columns to investigate the effects of one gypsum amendment on leaching of Ca, K, Mg, and SO₄ to a depth of 8 cm (fruiting zone of peanut). Six soils of varying physical and chemical properties representative of major peanut growing soils in Georgia were utilized. Following leaching with 15 cm water through gypsum‐amended soil columns, 50% to 56% and 74% to 77% of applied Ca and SO₄, respectively, were leached below 8 cm in the sandy‐Carnegie, Dothan, Fuquay and Tifton soils. The respective values for the sandy clay loam‐Greenville and Faceville soils were 28% to 36% and 58% to 69%. Lower initial Ca status and greater leaching of Ca from the applied gypsum in the sandy soils as compared to sandy clay loam soils suggest greater beneficial effects of supplemental gypsum application for peanut production in the former soils than in the latter soils. Leaching of K or Mg (as percentage of Mehlich 1 extractable K or Mg) in gypsum‐amended treatment was considerably greater in sandy soils than that in the sandy clay loam soils. In view of the reported adverse effects of high concentrations of soil K and Mg in the fruiting zone on the yield and quality of peanuts, greater leaching of K and Mg from the fruiting zone in gypsum amended sandy soils enable them to maintain a favorable cation balance for the production of high yields of quality peanuts.     

Phosphorus and trace metal dynamics in soils amended with poultry litter and granulates

Environmental sustainability of animal agriculture is strongly dependent upon development of approaches to minimize the potential environmental impacts of applying animal manures. The excess manure and its nutrients (primarily phosphorus) in intensive animal production regions may need to be exported to other areas to comply with increased regulations on manure management. In our previous study we generated a variety of granulated products from poultry litter to achieve export of excess litter from the southwestern Ozarks, AR, USA. Our objective in the present study was to determine the effect of the application of poultry litter and granulated litter products on phosphorus (P), arsenic (As), copper (Cu) and zinc (Zn) dynamics in two Arkansas soils (Dewitt silt loam and Hector sandy loam). Poultry litter and granulated products were mixed with the surface horizon (0–15 cm) of soils at two application rates: P‐based (100 kg total P per hectare) and N‐based (160 kg plant‐available N per hectare). Soil–litter mixtures were incubated at 25 °C for 21 days. Sub‐samples were removed at 1, 7 and 21 days to determine the solubility and availability of P, As, Cu and Zn in soils. Results suggest that when litter was applied at 100 kg total P per hectare, contents of P, As, Cu and Zn were significantly greater in the soils amended with litter and granulated products than in the control (soil alone). However, the contents of P, As, Cu and Zn did not significantly differ in the soils amended with either normal litter or granulated litter products at total P or plant‐available N‐based application rates. This suggests that poultry litter granulation is a sound management practice that can be used to reduce concerns with fresh litter transport and potentially improve P and trace element balances in intensive poultry production regions, especially when applied on a plant‐available N basis.     

Urease activity in two cultivated and non-cultivated arid soils

Summary Since urease activity in soil is believed to be relatively constant, the present study was designed to examine the effects of incubation, soil depth and the effect of cultivation on the persistence of urease activity in arid soils. Two soils were used, a Harkey (coarse, silty, mixed, calcareous, thermic, Typic Torrifluvent) and a Saneli (Clayey over sandy skeletal, montmorillonitic, calcareous, Vertic Torrifluvent), each consisting of a cultivated field and a non-cultivated roadbed site. Urease activity was much lower and more varable in the roadbed soils (40 years without cultivation) than in the cultivated field soils. Pre-incubation for 24 h with urea (with toluene) and without urea (without toluene) greatly reduced the total urease activity in all cases in relation to cell free urease activity (with toluene). Urease activity in the two field soils decreased slightly with profile depth but the decrease was greatest below the plow depth (33 cm). Protease activity or some inactivation processes must have lowered the urease content since there was substantially reduced urease activity after most pre-incubations. The extent of the urease activity decrease was so great that the addition of urea would have been required to increase the production of urease enzyme.