Ecotoxicity assessment of heavy metals and crude oil based on biological characteristics of chernozem

Soil pollution with Cr, Cu, Ni, and Pb oxides or crude oil has an adverse effect on biological properties of ordinary chernozem. The degrees of their deterioration in laboratory and field experiments do not differ statistically, indicating that the results of laboratory modeling may be correctly extrapolated to the field scale. Pollution of ordinary chernozem with oil affects biological properties of both topsoil and subsoil horizons, while Pb is harmful only for the upper soil horizon. Concentrations in excess of 25 mg/kg for Pb and 0.25% for oil in ordinary chernozem are not ecologically safe (not allowable).     

Bioremediation of oil sludge-contaminated soil

Bioremediation has become an important method for the restoration of oil-polluted environments by the use of indigenous or selected microbial flora. Several factors such as aeration, use of inorganic nutrients or fertilizers and the type of microbial species play a major role in the remediation of oil-contaminated sites. Experiments were undertaken for bioremediation of oil sludge-contaminated soil in the presence of a bacterial consortium, inorganic nutrients, compost and a bulking agent (wheat bran). Experiments were conducted in glass troughs for the 90-day period. Bulked soil showed more rapid degradation of oil compared to all other amendments. During the experimental period, wheat bran-amended soil showed 76% hydrocarbon removal compared to 66% in the case of inorganic nutrients-amended soil. A corresponding increase in the number of bacterial populations was also noticed. Addition of the bacterial consortium in different amendments significantly enhanced the removal of oil from the petroleum sludge from different treatment units.     

Preliminary exploration of the relationships between soil characteristics and PAH desorption and biodegradation

Desorption and biodegradation of pyrene (PYR) were investigated and their relationships to soil characteristics were addressed. The results indicated that maximum achievable desorption was 30.2, 10.4, and 1.0 mg/kg for soils that had 1.7, 2.2, and 4.4 wt.% of expandable clays (smectite and vermiculite), respectively. Neither dissolved organic matter (DOM) nor total clay amounts made a good prediction of the desorption trend. Subsequently, the ease of desorption facilitated a faster aqueous biodegradation rate. The slowest aqueous biodegradation rate, 0.02 l/h, was achieved for the soil system that had the greatest amount of expandable clays, whereas the soil containing 1.7% expandable clays only achieved 0.73 l/h. The soil with 2.2% expandable clays depicted 0.41 l/h of aqueous biodegradation rate. A good linear correlation was obtained between maximum achievable desorption and aqueous biodegradation rate (R(2)=0.92). Soil analysis revealed that the total (soil+water) biodegradation reached was 65%, 78.3%, and 81.8% of the initial concentration (100 mg/kg) for the sandy clay loam (Colombian), sandy loam (Ohio), and silty loam (New Mexico) soils, respectively. This biodegradation extent was also in good agreement of expandable clay amount. Although aqueous PYR bioavailability was limited due to the strong association with the expandable clays, microbial movement and adhesion to those clays seemed to result in a great extent of the soil-phase biodegradation.     

Effect of indigenous bacterial activity on arsenic mobilization under anaerobic conditions

Batch biochemical leaching tests were carried out to investigate the mobility of arsenic from a contaminated soil collected from a French gold mining site. The specific objective of this research was to examine the effect of indigenous bacterial activity on arsenic mobilization under anaerobic conditions. In a first step, physical and chemical characterizations were performed to provide data concerning the liquid-solid partitioning and mobility of arsenic and other inorganic constituents. In a second step, batch bioleaching tests were conducted in shaker flasks to determine the effect of indigenous bacterial activity under different anaerobic conditions (i.e., addition of mineral nutrients and carbon sources) on arsenic mobilization. Results indicated that arsenic release during contact with deionized water was limited by its very low solubility in the interstitial solution and by the stability of the different arsenic compounds formed with the amorphous solid phases of the soil (mainly iron (oxy)hydroxides). However, an increased mobilization potential was observed over the long term under anaerobic conditions with indigenous bacterial activity enhanced by the addition of carbon sources.     

An economic analysis of China’s domestic crude oil supply policies

ABSTRACT

China’s domestic oil production has lagged the growth in domestic oil consumption since the beginning of the 21st century, leading to a growing reliance on imports. In response, the Chinese government has introduced a number of policies, including import license constraints, to support domestic suppliers. In an effort to measure the economic impact of these policies we develop a short-run equilibrium model of China’s wholesale oil and gas market at the provincial scale. We construct counterfactual scenarios that suggest that relaxing policies that prioritize domestic production in 2016, when the average price of Chinese oil imports was US$42 per barrel (bbl), could have increased China’s import demand by 0.29 million barrels per day (MMbbl/d). This results in a substitution of 9% of China’s domestic production in 2016, and a reduction of US $2.8 billion in crude supply costs including transportation as the imported oil has more direct access to the country’s pipeline network, compared to the displaced domestic production. In addition, rising import prices since mid-2017 may provide a window of opportunity for Chinese policymakers to proceed with further deregulation of the domestic oil sector, as the short-term impact on domestic producers is reduced.     

Bioremediation of crude oil pollution in the Kuwaiti desert: The role of adherent microorganisms

Pieces of stones and other solid materials found in the oil lake sites of the Kuwaiti desert appeared clean, providing indications of surface-associated enhanced crude oil degradation. Scanning electron microscope studies revealed that such surfaces were colonized by active microbial populations. The colonization of the stone surfaces was concentrated within crevices. When enriched from washed pieces of stones from the oil lake, the resulting mixed population of adherent microorganisms degraded much more crude oil (44.4%) in the presence of inert carrier materials (styrofoam chips) in laboratory cultures, than in the absence of the inert materials (21.8%). The inert materials were found to be extensively colonized by microorganisms just as was observed with the stone and other solid samples from the oil lake.     

Distribution and migration of 95Zr in a tea plant/soil system

(95)Zr is a primary radionuclide in the radioactive liquid efflux from a pressurized water reactor and one of the main radionuclides released after nuclear accidents. The fission yield of (95)Zr is as high as 6.2%, however, its environmental behavior has not been well documented. An experiment was conducted to evaluate the accumulation and distribution of (95)Zr in a tea plant/soil system. (95)Zr was accumulated primarily in the trunk of tea plants after being taken up from the soil. The radioactivity concentration of (95)Zr in the trunk increased slowly with time, then it reached a dynamic equilibrium 14 days after application. The radioactivity concentration of (95)Zr in the other parts of the tea plant was very low; only slighter greater than the detection limit. The results indicated that (95)Zr was not readily translocated in the tea plant. About 98.9% of applied (95)Zr was found to concentrate in the upper 5 cm layer after being sprayed onto the soil surface. The results indicated that (95)Zr could not readily move downwards with percolating water due to strong adsorption to surface soil.     

Effect of soil texture on surfactant-based remediation of hydrophobic organic-contaminated soil

Surfactants may be used in remediation of subsoil and aquifer contaminated with hydrophobic compounds. The objectives of this study were to examine the effect of soil texture on hydrophobic organic contaminant (HOC; toluene, or 1,2,4-trichlorobenzene [TCB]) removal from six soils and to evaluate the optimal composition of soil texture for maximum HOC removal using aqueous surfactant solution. Selected surfactants were 4% (vol/vol) sodium diphenyl oxide disulfonate (DOSL) and 4% (wt/vol) sodium lauryl sulfate (LS). Toluene and TCB were selected as the lighter-than-water nonaqueous phase liquid (LNAPL) and denser-than-water nonaqueous phase liquid (DNAPL) model substances, respectively. Soil types used for this study were Ottawa sand and five Iowa soils (Fruitfield, Keomah, Crippin, Webster, and Galvar). The greatest recovery of toluene and TCB in batch tests was 73% and 84%, respectively, which was obtained with DOSL surfactant in Ottawa sand. The toluene removal of 95% in column tests has been achieved in the Ottawa sand and three Iowa soils (Fruitfield, Keomah, Crippin) with DOSL after effluent volume of 3750 ml (about 32 pore volume) passed. TCB removal of 98% in column tests has been achieved in Ottawa sand and three Iowa soils (Fruitfield, Keomah, Crippin) with DOSL after effluent volume of 2500 ml (about 21 pore volume) passed. These results were related with soil texture (clay content 30%), clay mineralogy (kaolinite and smectite), as a function of transported pore volume.     

Behaviors of 323Th, 238U, 228Ra and 226Ra on combustion of crude oil terminal sludge

Crude oil terminal sludge contains technologically enhanced naturally occurring radionuclides such as (232)Th, (238)U, (228)Ra and (226)Ra, thus cannot be disposed of freely without proper control. The current method of disposal, such as land farming and storing in plastic drums is not recommended because it will have a long-term impact on the environment. Due to its organic nature, there is a move to treat this sludge by thermal methods such as incineration. This study has been carried out to determine the behaviors of (232)Th, (238)U, (228)Ra and (226)Ra present in the sludge during combustion at a certain temperature and time. The percentage of volatilization was found to vary between 2% and 70%, (238)U was the most volatile in comparison with (232)Th, (228)Ra and (226)Ra. (238)U is found to be significantly volatilized above 500 degrees C, and might reach maximum volatilization at above 700 degrees C. A mathematical model was developed to predict the percentage of volatilization of (232)Th, (238)U, (228)Ra and (226)Ra contained in the sludge. With this known percentage of volatilization, the concentration of (232)Th, (238)U, (228)Ra and (226)Ra present in the bottom and filter ashes can be calculated.     

Composition of soil diatoms in zones of impact from oil production complexes

The impact of territorial oil production complexes on the species composition of soil diatom (Bacillariophyta) communities and the degree of their development has been studied. On the basis of comparisons between dominant diatom assemblages from different natural zones, suggestions are made concerning the strategy of their adaptation to extreme environmental conditions. A scheme of transformation of diatom communities under the impact of oil pollution is proposed.     

Dynamics of leaf litter and soil respiration in a complex multistrata agroforestry system,Pernambuco, Brazil

High litter inputs in agroforestry systems contribute to soil microbial activity, soil fertility and productivity. Considering that the cycling of organic matter is essential to the maintenance of physical–chemical and microbiological properties of the soil, the aims of this work were to estimate the production, accumulation and decomposition of litter, and assess soil microbial respiration in a complex multistrata agroforestry system located in the north-east of Brazil. This agroforestry system has three strata formed by forest and fruit trees and species of multiple uses. During 3 years (2011–2013), leaf litter was sampled monthly to account for litterfall and quarterly to account for litter accumulation. The rates of litter decomposition were estimated using the ratio produced-to-accumulated litter, and the correlation between litter fall and rainfall was calculated. Precipitation data were provided by the water and climate agency of Pernambuco (APAC). Soil samples (0–15 cm) were also taken quarterly, simultaneously with the litter accumulation samples, and soil microbial respiration was assessed using the capture, by a KOH solution, of the evolved CO₂. The annual production of leaf litter was stable in the 3 years of study in this agroforestry system, and the monthly input of litter to the soil was influenced by rainfall, being higher in the dry seasons. The accumulated litter on the ground was constant, as was microbial activity (respiration) through time. The estimated litter decomposition rates were 1.49 (first year), 1.33 (second year) and 1.42 (third year), being considered rapid rates of decomposition. This guarantees (to the farmer) that this system is capable of maintaining soil fertility and eliminates the need for chemical fertilizers.     

Effect of sewage sludge amendment on soil microbial activity and nutrient mineralization

An incubation experiment was performed to study the effect of sewage sludge on microbial respiration and nutrient mineralization in a sandy soil as an indication of its effects on soil biological properties and nutrient transformation. Sewage sludge was amended with a sandy soil at 0, 25, 50, 150 and 350 g kg⁻¹ fresh weight. An increase in the sludge amendment rate caused an increase in both pH and electrical conductivity (EC). However, pH decreased while EC increased and then decreased along the incubation time. Nevertheless salinity and heavy metal contents of the soil sludge mixture were all within the safety guidelines. Soluble NH₄⁺, NO₃²⁻ and PO₃²⁻ increased after amending the soil with sewage sludge, but increasing the application rate to 350 g kg⁻¹ of sludge decreased the N and P mineralization efficiency and created an adverse effect on nitrification. The daily CO₂ evolution pattern was the same in all treatments that CO₂ evolution increased initially and then decreased till the end of the incubation period. All the treatments had peak CO₂ evolution at day 7, except for the soil amended with 350 g kg⁻¹ of sludge which had peak CO₂ evolution at day 2. Similarly, the percentage of C-mineralization decreased with an increase in sludge amendment rate. The present experiment indicated that an application rate of 50–150 g kg⁻¹ sludge for sandy soil would have the optimal beneficial effect on the soil in terms of microbial activity and nutrient transformation.     

Effect of heavy metals and PAH on soil assessed via dehydrogenase assay

Dehydrogenase enzyme activity (DHA) assay method using resazurin was accommodated for measuring of toxicity of compound contaminants on uncharacterized microbial communities present in any given soil. The method was used to compare the toxic effect of heavy metal and polycyclic aromatic hydrocarbon (PAH) contaminant mixture (Cr, Pb, Cu, Cd, Pyrene) on four typical Estonian soils covering a range of compositions. The method proved to be useable on all soils; the sensitivity of soil microbiology to toxic effect of contaminants was found to have a negative correlation with Ca and organic matter (OM) content and a positive correlation with amorphous phase content of soils.     

Effect of soil properties on arsenic fractionation and bioaccessibility in cattle and sheep dipping vat sites

Historical use of high arsenic (As) concentrations in cattle/sheep dipping vat sites to treat ticks has resulted in severe contamination of soil and groundwater with this Group-A human carcinogen. In the absence of a universally applicable soil As bioaccessibility model, baseline risk assessment studies have traditionally used the extremely conservative estimate of 100% soil As bioaccessibility. Several in-vitro, as well as, in-vivo animal studies suggest that As bioaccessibility in soil can be lower than that in water. Arsenic in soils exists in several geochemical forms with varying degree of dissolution in the human digestive system, and thus, with highly varying As bioaccessibility. Earlier batch incubation studies with As-spiked soils have shown that As bioaccessibility is a function of soil physicochemical properties. We selected 12 dipping vat soils collected from USA and Australia to test the hypothesis that soil properties exert a significant effect on As bioaccessibility in As-contaminated sites. The 12 soils varied widely in terms of soil physico-chemical properties. They were subject to an As sequential fractionation scheme and two in-vitro tests (IVGS and IVGIA) to simulate soil As bioavailability in the human gastrointestinal system. Sequential As fractionation results showed that the majority of the As measured in the dipping vat soils resided either in the Fe/Al hydroxide fraction, or the Ca/Mg fractions, or in the residual fraction. Water-extractable As fraction of the 12 soils was typically <10% of the total, reaching values up to 23%, indicating minimal leaching potential, and hence, lower risk of As-contamination from exposure to groundwater, typically used as drinking water in many parts of the world. Partial individual correlations and subsequent multiple regression analyses suggested that the most significant soil factors influencing As bioaccessibility were total Ca+Mg, total P, clay content and EC. Collectively, these soil properties were able to explain 85 and 86% of the variability associated with the prediction of bioaccessible As, using IVGS and IVGIA in-vitro tests, respectively. This study showed that specific soil properties influenced the magnitude of soil As bioaccessibility, which was typically much lower than total soil-As concentrations, challenging the traditional risk assessment guideline, which assumes that soil As is 100% bioaccessible. Our study showed that total soil As concentration is unlikely to provide an accurate estimate of human health risk from exposure to dipping vat site soils.     

Effect of copper-tolerant rhizosphere bacteria on mobility of copper in soil and copper accumulation by Elsholtzia splendens

The role of rhizosphere bacteria in facilitating the solubility of copper (Cu) in contaminated soil and Cu accumulation in plant were studied. The bacteria strains were isolated from the rhizosphere of Elsholtzia splendens, a Cu accumulator growing on Tonglu Mountain copper mines. After the sandy soils containing 237 mg kg(-1) were incubated with the bacteria strains, it was indicated that rhizosphere microbes played an important role in influencing the availability of water-soluble Cu in soils. Soils had greater concentrations of water-extractable Cu compared with axenic soils inoculated with different bacterial strains. Further evidence for bacterial facilitation of increased solubility of Cu in the soil was obtained using the antibiotic ampicillin (0.1 mg g(-1)). There were 36% decreases in Cu concentration in the presence of bacterial strain MS12 and ampicillin together compared with bacterial inoculation alone. Different bacterial strains had different abilities on soil water-soluble Cu. To achieve the highest rates of plant Cu accumulation, it was necessary for bacteria to be present in the rhizosphere of E. splendens. Inoculated plants supplied with 20 micromol L(-1) CuSO4 had significantly greater concentrations of Cu in shoots and roots than uninoculated plants and bacterial strain MS2 was the most effective strain in promoting plant Cu uptake. There were 2.2-fold and 2.5-fold increases in Cu accumulation in the shoots and roots of plants inoculated with strain MS2 compared to axenic controls. Furthermore, when ampicillin and the bacterial strains were added together to the nutrient solution, the Cu concentrations in roots and shoots of ampicillin-treated plants were lower than those in inoculated plants. When ampicillin was added to the nutrient solution, Cu accumulation was inhibited by about 24-44% in shoots and 20-44% in roots. The above results provided a new insight into the phytoremediation of Cu-contaminated soil.     

Effect of elemental sulphur on solubility of soil heavy metals and their uptake by maize

A pot experiment was conducted to study the influence of elemental sulphur (S) on solubility of soil Pb, Zn and Cd and uptake by maize (Zea mays L.). Two rates of elemental sulphur (S) applied at 0 (S0) and 200 (S200) mmol kg(-1) soil with three rates of each heavy metal at Pb, 0 (Pb0), 200 (Pb200), 400 (Pb400) mg kg(-1) soil, Zn, 0 (Zn0), 100 (Zn100), 200 (Zn200) mg kg(-1) soil and Cd, 0 (Cd0), 50 (Cd50), 100 (Cd100) mg kg(-1) soil, respectively. The result showed that with S application at 200 mmol S kg(-1), soil pH decreased about 0.3 unit and the solubility of the Zn and Cd was significantly increased, but the solubility of Pb had no significant influence. The concentration of Pb, Zn and Cd in maize shoots and roots were increased with increasing rates of heavy metals. However, the concentration of Zn and Cd in shoots and roots were higher with application of S rather than without S but no significant difference was found for Pb. The highest concentration of Zn in the shoots was 2.3 times higher with application of S rather than without at the same rate of Zn, 200 mg kg(-1). Plant biomass was also significantly affected by the application of S and of heavy metals. With heavy metal addition, the shoot and root biomass were decreased with the rates of those of heavy metals increased either with or without application of S. However, the shoot biomass was significantly decreased with S application at the same rate of heavy metals except that with Zn addition. The removal of Cd and Pb by maize uptake and accumulation with application of S had no significant increase compared to that without, but the removal Zn by maize uptake from the soil increased by application of S, 90.9 microg plant(-1) contrast to 25.7 microg plant(-1) at Zn200 within a growth period of only 40 days.     

Evaluation of mixture effects in a crude extract of compost using the CALUX bioassay and HPLC fractionation

Potential synergistic interactions between polycyclic aromatic hydrocarbons in a household sewage sludge compost extract were investigated using the Dioxin-Responsive Chemical-Activated Luciferase gene eXpression (DR-CALUX) assay and reverse-phase high-performance liquid chromatography (RP-HPLC) fractionation. The biological activity of the crude extract was measured in vitro using the CALUX assay. The CALUX activity of the extract was as potent as 360-pg CALUX-TEQ (2,3,7,8-TCDD equivalent value) per g sample, this was 70 times above the WHO-TEQ value which was derived from chemical analyses of dioxins/furans and dioxin-like PCBs of the mixture. The CALUX activity pattern of the crude extract and the retention times of 26 polycyclic aromatic compounds (PACs), as determined by RP-HPLC on an octadecylsilica column, suggested that the dioxin-like compounds with the log K(OW) (n-octanol/water partition coefficient) values corresponding to 6.0-7.0 contributed highly to the whole activity. The CALUX activity of the crude extract was three times the sum of the CALUX activities of the RP-HPLC separated fractions. Mixture effects were assessed by co-exposure of each HPLC fraction and 2,3,7,8-TCDD to the cells. The four concentration levels of added 2,3,7,8-TCDD corresponded to the TEQ value in the original compost sample. The experimental CALUX activity was higher than the predicted CALUX activity for some fractions. It was demonstrated that some compounds in the compost sample interacted synergistically with 2,3,7,8-TCDD in terms of dioxin-like activity. This finding points out the necessity for detailed investigation of synergistic effects in environmental samples.     

Effects of organic acids on copper and cadmium desorption from contaminated soils

A study was conducted to investigate the effect of organic acids on Cd and Cu desorption from natural contaminated soils (NCS) with permanent contamination by metal smelters and from artificial contaminated soils (ACS) derived from an artificial amendment of Cd to three representative zonal soils in Central China. Results showed that the desorption of Cd in either NCS or ACS, with the increment of tartrate or citrate concentration in desorption solution, can be characterized as a valley-like curve. The presence of tartrate or citrate at a low concentration (< or =0.5 mmol/l) inhibited Cd desorption from these two types of soils, whereas the presence of organic acids at high concentrations (> or =2 mmol/l for citrate and about > or =15 mmol/l for tartrate) apparently promoted Cd desorption. The desorption curve of Cu by tartrate solution with different tartrate concentrations can also be characterized as a valley-like curve, while the desorption of Cu in the presence of citrate was directly enhanced with the increment of citrate concentration. With the enhancement of initial pH value from 2 to 8 in the presence of citrate, Cu desorption ratio decreased at the first stage, then increased, and then decreased again. A valley and a peak sequentially appeared in the Cd or Cu desorption curve with initial pH value increment. Compared with citrate, the desorption ratio of Cd or Cu from NCS or ACS was directly decreased in the presence of tartrate, with the enhancement of the pH value from 2 to 8. Cd or Cu desorption was clearly enhanced when the electrolyte concentration of KNO3 or KCl increased in the presence of 2 mmol/l tartrate. Moreover, a higher desorption ratio of Cd or Cu was shown with KCl electrolyte than with KNO3 electrolyte with the same concentration. Based on these observations, we suggest that bioavailabilities of heavy metal can be promoted with selected suitable types and concentrations of organic acid amendment and reasonable field condition.     

Effect of compaction on soil CO2 and CH4 fluxes from tropical peatland in Sarawak,Malaysia

Environment, Development and Sustainability - Tropical peatland stores a large amount of carbon (C) and is an important C sink. In Malaysia, about 25% of the peatland area has been converted to oil...     

Distribution and mobilization of U, Th and 226Ra in the plant-soil compartments of a mineralized uranium area in south-west Spain

The activity concentrations of natural uranium isotopes (238U and 234U), thorium isotopes (232Th, 230Th and 225Th) and 226Ra were studied in soil and vegetation samples from a disused uranium mine located in the Extremadura region in the south-west of Spain. The results allowed us to characterize radiologically the area close to the installation and one affected zone was clearly manifest as being dependent on the direction of the surface water flow from the mine. The activity concentration mean values (Bq/kg) in this zone were: 10,924, 10,900, 10,075 and 5,289 for 238U, 234U, 230Th and 226Ra, respectively, in soil samples and 1,050, 1,060, 768 and 1,141 for the same radionuclides in plant samples. In an unaffected zone, the activity concentration mean values (Bq/kg) were: 184, 190, 234 and 7251 for 235U, 234U, 230Th and 226Ra, respectively, in soil samples and 28. 29, 31 and 80 in plant samples. The activity concentrations obtained for 232Th and 228Th showed that the influence of the mine was only important for the uranium series radionuclides. The relative radionuclide mobilities were determined from the activity ratios. Correlations between radionuclide activity concentrations and stable element concentrations in the soil samples helped to understand the possible distribution paths for the natural radionuclides.