Uncontaminated Control Soil Research Articles

Evaluation of Physicochemical Parameters, Total Bacteria Count and some Heavy Metal Levels in Soil from Automobile Workshop Activities at Nnewi Local Government Area, Anambra State, Nigeria

Disposal of used motor oil and chemical substances on land leads to loss in soil quality by minimal abundance and variety of microorganisms in soil. The objective of this paper was to evalaute the physicochemical parameters, total bacteria count and some heavy metal levels in soil from automobile workshop activities at Nnewi Local Government Area, Anambra State, Nigeria. Using field survey and appropriate standard laboratory analyses, the results showed that the control uncontaminated soil samples recorded high bacteria count (6.9 x106 cfu/g). The available soil nitrogen(9.0), soil nutrients nitrate (15.10) and phosphorous (17.3) all recorded appropriate values when compared with WHO standard. The acidity of the soil using pH value as an indicator showed that the uncontaminated control soil samples were acceptable for crops also the Ec values. The heavy metals analysed indicates that the control soil samples were also moderate in heavy metals accumulation when compared with the contaminated soil samples particularly Cd, Pb (0.08) and Hg (0.01) while Cd was not detectable. These findings have shown that automobile activities can denature soil properties which could lead to soil infertility. The automobile activities has to be controled by the concerned agencies in Nigeria. Environmental education should be encouraged to reduce effects of anthropogenic activities on soil quality in the study area.

Effects of acid mine drainage and sediment contamination on soil bacterial communities, interaction patterns, and functions in alkaline desert grassland

Acid mine drainage and sediments (AMD-Sed) contamination pose serious ecological and environmental problems. This study investigated the geochemical parameters and bacterial communities in the sediment layer (A) and buried soil layer (B) of desert grassland contaminated with AMD-Sed and compared them to an uncontaminated control soil layer (CK). The results showed that soil pH was significantly lower and iron, sulfur, and electroconductivity levels were significantly higher in the B layer compared to CK. A and B were dominated by Proteobacteria and Actinobacteriota, while CK was dominated by Firmicutes and Bacteroidota. The pH, Fe, S, and potentially toxic elements (PTEs) gradients were key influences on bacterial community variability, with AMD contamination characterization factors (pH, Fe, and S) explaining 48.6 % of bacterial community variation. A bacterial co-occurrence network analysis showed that AMD-Sed contamination significantly affected topological properties, reduced network complexity and stability, and increased the vulnerability of desert grassland soil ecosystems. In addition, AMD-Sed contamination reduced C/N-cycle functioning in B, but increased S-cycle functioning. The results highlight the effects of AMD-Sed contamination on soil bacterial communities and ecological functions in desert grassland and provide a reference basis for the management and restoration of desert grassland ecosystems in their later stages.

Effects of Automobile Battery Wastes Disposal on Soil Health Indices

This study was designed to assess the impact of automobile battery waste disposal on the indices of soil health and fertility. Soil samples were collected from three major mechanic villages in Akure and Owo in Ondo State. The physicochemical parameters were analyzed using standard methods while the heavy metal content was assessed using a spectrophotometer. Also, the microbial population was determined using the pour plate method and some biochemical tests. The results show that the soil sample from Owo had the least total bacterial count of 65.10x 105 CFU/g) while the sample from Akure 2 had the highest bacterial count of 185.50 x 105 CFU/g. The probable organisms isolated from the samples were Klebsiella spp, Escherichia spp, Staphylococcus spp, Proteus spp, Pseudomonas spp, Bacillus spp, Serratia spp and Enterobacter spp. There were significant differences between the physicochemical parameters of the contaminated soil samples and the uncontaminated control soil. The electrical conductivity of the contaminated soil samples (1.20, 0.92 and 0.38) was higher significantly (p<0.05) than the uncontaminated (0.21) soil sample. The pH values were acidic (4.57) compared with the control (7.42). Other indices like C, Ca. CEC and bulk density among others have values that were different significantly (P<0.05) between the contaminated soil and the control. In addition, the levels of heavy metals such as Lead, Cadmium and Chromium in the contaminated soil were significantly higher than in the control soil sample. The study confirms that the health indicators of the battery waste-receiving soil in the studied area are highly compromised therefore it may need remediation to reduce soil pollution.

Soil Bacterial Community Tolerance to Three Tetracycline Antibiotics Induced by Ni and Zn

A laboratory work has been carried out to determine the tolerance of soil bacterial communities to Ni and Zn and co-tolerance to tetracycline antibiotics (chlortetracycline (CTC), oxytetracycline (OTC) and tetracycline (TC)) in soils individually spiked with five different concentrations of Ni or Zn (1,000, 750, 500, 250, and 125 mg kg−1), and an uncontaminated (0 mg kg−1) control soil. The PICT parameter (pollution-induced community tolerance) was estimated for the bacterial community using the tritium (3H)-labeled leucine incorporation technique, and the values corresponding to log IC50 were used as toxicity index. The mean log IC50 values observed in the uncontaminated soil samples indicate that Zn (with log IC50 = −2.83) was more toxic than Ni (log IC50 = −2.73). In addition, for the soil with the lowest carbon content (C = 1.9%), Ni-contaminated samples showed increased tolerance when the Ni concentrations added were ≥500 mg kg−1, while for the soils with higher carbon content (between 5.3% and 10.9%) tolerance increased when Ni concentrations added were ≥1,000 mg kg−1. Regarding the soils contaminated with Zn, tolerance increased in all the soils studied when the Zn concentrations added were ≥125 mg kg−1, regardless of the soil carbon content. The co-tolerance increases obtained after exposure of the bacterial suspension to TC, OTC and CTC showed an identical behavior within these tetracycline antibiotics. However, it was dependent on the heavy metal tested (Ni or Zn). In the case of soils 1 (C = 1.1%) and 2 (C = 5.3%), the soil bacterial communities showed increases in co-tolerance to TC, OTC and CTC for Ni concentrations added of ≥125 mg kg−1, while for soil 3 (with C = 10.9%) co-tolerance took place when Ni was added at ≥1,000 mg kg−1. However, in soils contaminated with Zn, increases in co-tolerance to CTC, OTC and TC occurred at Zn concentrations added of ≥125 mg kg−1 for the 3 soils tested. These results can be considered relevant when anticipating possible environmental repercussions related to the simultaneous presence of various types of pollutants, specifically certain heavy metals and antibiotics.

A meta-analysis-based evaluation of metallic element accumulation in earthworms

The responses of earthworms to excess soil element concentrations are well studied. However, published information on the metallic element accumulation in individuals is controversial. In this paper, the published data on earthworm As, Cd, Cr, Cu, Ni, Pb, and Zn whole body concentrations were evaluated in individuals collected from contaminated and uncontaminated (control) soils, using meta-analyses. The role of soil pH and exposure time as potential influencing factors on metal accumulation was also assessed. Based on the evaluations, the accumulation of each metallic element was significantly (p < 0.05) more intensive in individuals collected from contaminated soils than in ones from control soils, with minor differences in the order of accumulation intensity among the studied metallic elements. Further, major interspecific differences were indicated in the accumulation, with different species being the most intensive accumulators for individual metallic elements. Among the studied metals, Cu concentration in earthworm bodies increased significantly with increasing soil pH. As for the exposure time-dependent accumulation, Pb concentration was found to decrease significantly with time in whole body tissues of earthworms. These results suggested a high variability in metal- and species-specific accumulation-excretion patterns of earthworms, influenced also by other external factors. Based on the results highlighted in this meta-analysis, accumulation schemes raise the need for further analyses involving other additional variables (e.g., soil type, organic matter content, climatic condition) to get a better understanding of element cycle-earthworm relations.

Cowpea induced physicochemical and biological rhizosphere changes in hydrocarbon contaminated soil

PurposeTo understand the influence of cowpea on its rhizosphere physicochemical and biological conditions.MethodsPristine soil samples were contaminated with Bonny-Light crude oil and viable seeds of cowpea were planted to establish rhizosphere soil. Cowpea root exudates were collected and characterized while soil metabolic activities, physicochemical properties and rhizosphere effect were monitored following plant emergence.ResultsCowpea root exudates were composed of organic acids, phenolics, carbohydrates and hydrocarbons. High rate of soil respiration and microbial biomass carbon were observed in the contaminated rhizosphere reaching its peak on 12th week (70.56 mgCO2g−1 day−1) and 10th week (23.18 mg/Kg) respectively. Lower rates of soil respirations and microbial biomass carbon were observed in contaminated (10.28 mgCO2g−1 day−1; 1.24 mg/Kg) and uncontaminated (0.23 mgCO2g−1 day−1; 0.37 mg/Kg) non-rhizosphere control soils respectively. The metabolic properties were positively correlated with soil organic matter contents and microbial size (r = 0.98; p < 0.05). There was considerable improvement in soil physicochemical properties in the cowpea rhizosphere as compared to non-rhizosphere soil. Microbial populations were generally improved with positive rhizosphere effect values (> 1) presumably due to the presence of compounds in exudates that promote microbial growth.ConclusionThe results highlighted the influence of cowpea on its rhizosphere conditions which is a good indication for its ability to promote plant growth and environmental cleanup. Therefore, there is the need to further understand the microbial community dynamics in cowpea rhizosphere using culture-independent techniques.

Influence of Different Soil Conditioner on the Transfer and Transformation of Cadmium and Phthalate Esters in Soil

This study examines the existing common form of soil pollution, combined organic and inorganic pollution. Cadmium (Cd) is the most important inorganic element in soil pollution. Due to the widespread use of plastic film, phthalates have become the main organic pollutants in soil. Pot experiments were conducted with purple soil from southwest China, and Chinese cabbage was used as a biological indicator. Different concentration gradients of Cd and diethylhexyl phthalate (DEHP) was used as foreign pollutants. The soil was treated with one of the six common soil conditioners, namely potassium feldspar powder, oyster shell powder, biological carbon powder (biochar), calcium, potassium carbonate, and calcium phosphate, to examine the effect of conditioners on cadmium morphology, DEHP content in contaminated soil, and cadmium and DEHP absorption in Chinese cabbage. The results showed that biochar is the optimal soil conditioner for the remediation of cadmium-phthalate composite pollution in purple soil. Subsequently, the effects of soil biochar content on cadmium pollution and phthalate ester migration were studied. Uncontaminated control soil, Cd-contaminated soil, and DEHP-contaminated soil were examined by pot experiments, and biochar treatments with mass fraction of 0%, 0.5%, 1%, 3%, and 5% added to cadmium contaminated soil were used to determine its influence on Cd morphology and DEHP content of contaminated soil.

Detection and discrimination of various oil-contaminated soils using vegetation reflectance

The use of hyperspectral spectroscopy for oil detection recently sparked a growing interest for risk assessment over vegetated areas. In a perspective of image applications, we conducted a greenhouse experiment on a brownfield-established species, Rubus fruticosus L. (bramble), to evaluate the potential of vegetation reflectance to detect and discriminate among various oil-contaminated soils. The species was grown for 32 days on four different soils with mixtures of petroleum hydrocarbons and heavy metals. Additional plants were grown on either uncontaminated control or water-deficient soils for comparison. Repeated reflectance measurements indicated modified spectral signatures under both oil and water-deficit exposure, from leaf to multi-plant scales. The amplitude of the response varied with mixture composition, exposure time, acquisition scale and spectrum region. Reflectance changes were linked to alterations in chlorophyll, carotenoid and water contents using vegetation indices. These indices were used to catch spectral similarities among acquisition scales and to discriminate among treatments using Kendall's coefficient of concordance (W) and regularized logistic regression. Of the 33 vegetation indices tested, 14 were concordant from leaf to multi-plant scales (W > 0.75, p < 0.05) and strongly related to leaf biochemistry (R2 > 0.7). The 14 indices allowed discriminating between each mixture and the control treatment with no or minor confusions (≤5%) at all acquisition scales, depending on exposure time. Some of the mixtures remained difficult to discriminate among them and from the water-deficit treatment. The approach was tested at the canopy scale under natural conditions and performed well for identifying bramble exposed to either one of the experimentally-tested mixtures (90% accuracy) or to uncontaminated soil (83% accuracy). This study provided better understanding of vegetation spectral response to oil mixtures and opens up promising perspectives for future applications.

Comparison of freely dissolved concentrations of PAHs in contaminated pot soils under saturated and unsaturated water conditions

Passive sampling (PS, equally used for passive sampler) methods have successfully been applied in situ to quantify the bioavailability of hydrophobic organic compounds in air, water and sediments. However, very little is known on the applicability of PS in unsaturated soils. Here, we present the results of a greenhouse experiment in which we applied in situ PS methods in pots. Low density polyethylene (LDPE) and polydimethylsiloxane (PDMS) fibres with a newly developed PS holder were used to analyse freely dissolved polycyclic aromatic hydrocarbon (PAH) concentrations (Cfree) in a skeet shooting range soil and an uncontaminated control soil under water saturated and unsaturated conditions for up to nine months. A short exposure time of three months was not sufficient for the PDMS samplers to reach distribution equilibrium with the surrounding soil. Under saturated water conditions, the in situ results agreed well with measurements obtained from the conventional ex situ soil suspension method. They were in accordance with similar comparisons made in previous studies on sediments, as well as with model predictions. However, for unsaturated water conditions, the results differed considerably from the ex situ Cfree values, in particular for the light molecular weight (LMW) PAHs such as phenanthrene, fluoranthene, and pyrene. The results of the two in situ PS methods were in good agreement with each other under both soil water conditions, indicating that dissipation mechanisms, such as degradation or volatilization, led to a substantial decrease in Cfree under unsaturated conditions, especially for the LMW PAHs (log10KOW < 5.85) over a period of six months or more. Thus, in their current state of development, in situ PS methods can be used in soils under water-saturated conditions. However, an adequate method to correct for non-equilibrium conditions needs to be developed before they can be applied to unsaturated conditions, mainly for LMW PAHs.

Compost and biochar assisted phytoremediation potentials of Moringa oleifera for remediation of lead contaminated soil

The aim of this study was to investigate the germination, growth, tolerance and Pb accumulation potentials of Moringa oleifera in compost and biochar amended Pb-contaminated soils for possible phytoremediation. Lead slag contaminated soil (100%–32,640 mg/kg) was diluted into three Pb contamination levels (75%, 50%, and 25%) by mixing it with uncontaminated control (0%) soil. Sunflower-poultry manure compost (Compost), rice husk biochar (RHB) and groundnut shell biochar (GSB) were applied at 10 g/kg separately to the soils in triplicates and incubated for 2 weeks. Moringa oleifera seedlings were transplanted at two weeks into the incubated soils and set up in greenhouse experiments. Plant height, stem girth, leaf number and biomass were measured at 4 and 8 weeks. Plant roots and shoots were analysed. Moringa oleifera seeds planted in the contaminated and amended contaminated soils failed to germinate. Its seedlings withered off in 100% and 75% but survived in 25% and 50% amended contaminated and control soils. It tolerated Pb contamination up to 8600 mg/kg. The concentrations of Pb in the roots and shoots of the plants at 8 weeks ranged from 930 to 2100 mg/kg and 420–1120 mg/kg respectively for both contamination levels, indicating Pb phytoaccumulation potentials of M. oleifera. Compost and RHB enhanced M. oleifera roots and shoots production. The combination of compost and M. oleifera improved Pb phytoextraction efficiency. The combination of GSB and M. oleifera improved Pb phytostabilisation efficiency. Utilisation of compost, rice RHB and GSB with M. oleifera may be recommended for phytoremediation of Pb-contaminated soil.

Germination, physiological and biochemical responses of acacia seedlings (Acacia raddiana and Acacia tortilis) to petroleum contaminated soils.

Along the arid Arava, southern Israel, acacia trees (Acacia raddiana and Acacia tortilis) are considered keystone species. Yet they are threatened by the ongoing aquifer depletion for agriculture, the conversion of natural land to agricultural land, seed infestation by bruchid beetles, and the reduction in precipitation level in the region. In the acacia dominated Evrona reserve (southern Arava), adding to these threats are recurrent oil spills from an underground pipeline. We report here a study of the effects of contaminated soils, from a recent (December 2014) and a much older (1975) oil spills. The effects of local petroleum oil-contaminated soils on germination and early growing stages of the two acacia species were studied by comparisons with uncontaminated (control) soils from the same sites. For both acacia species, germination was significantly reduced in the 2014 oil-contaminated soils, whereas delayed in the 1975 oil-contaminated soil. There was no significant effect of oil volatile compounds on seed germination. At 105 days post transplanting (DPT), height, leaf number, stem diameter, and root growth were significantly smaller in the oil-contaminated soils. While photosynthetic performance (quantum yield of photosystem II) did not differ considerably between treatments, reductions of chlorophylls content and protein content were found in seedlings growing in the contaminated soils. Significant increases in superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities were found in roots of seedlings growing in oil-contaminated soils. These results demonstrate that seed germination and seedling growth of both acacia species were strongly restricted by oil contamination in soils, from both recent (2014) and a 40-year old (1975) oil spills. Such long-term effects of oil spills on local acacia seedlings could shift the structure of local acacia communities. These results should be taken into account by local authorities aiming to clean up and restore such polluted areas.

Natural attenuation of toxic metal phytoavailability in 35-year-old sewage sludge-amended soil.

Toxic heavy metals persist in agricultural soils and ecosystem for many decades after their application as contaminants in sewage sludge and fertilizer products This study assessed the potential long-term risk of cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu) in land-applied sewage sludge to food crop contamination. A sewage sludge-amended soil (SAS) aged in the field more than 35years was used in a greenhouse pot experiment with leafy vegetables (lettuce and amaranth) having strong Cd and Zn accumulation tendencies. Soil media with variable levels of available Cd, Zn, and Cu (measured using 0.01M CaCl2 extraction) were prepared by diluting SAS with several levels of uncontaminated control soil. Despite long-term aging in the field, the sludge site soil still retains large reserves of heavy metals, residual organic matter, phosphorus, and other nutrients, but its characteristics appear to have stabilized over time. Nevertheless, lettuce and amaranth harvested from the sludge-treated soil had undesirable contents of Cd and Zn. The high plant uptake efficiency for Cd and Zn raises a concern regarding the quality and safety of leafy vegetables in particular, when these crops are grown on soils that have been amended heavily with sewage sludge products at any time in their past.

The suitability of potworms (&lt;i&gt;Enchytraeidae&lt;/i&gt;) and plants to test the toxicity of oil refinery sludge

Landfarming is used in southern Africa as a tool to dispose of contaminants in the petrochemical industry. A historically landfarmed site was identified at a petroleum refinery where the sludge deposited on the site consisted of a mixture of oil and water-soluble contaminants which included several hazardous chemicals. The aim of this study was to assess the toxicity of the sludge, as well as of soil from the landfarming site, and to determine if potworms and plants could be used in bioassays since there is a need to identify a variety of test species, representing different ecological niches. We exposed a soil-dwelling potworm (Enchytraeus doerjesi) to the sludge and the landfarming soil to study their survival, growth, reproduction success and avoidance behaviour. Five plant species and their seeds were exposed to different concentrations of sludge in potting soil, and consequently germination success, growth rate and biomass were monitored. The various soils from the landfarming site were not acutely toxic to the potworms and they even showed an increase in reproduction, compared to uncontaminated control soil. They avoided heavily contaminated soil from the landfarming site. We conclude that the potworms were not as sensitive as the earthworms and springtails previously tested. They may nevertheless still be utilised for testing the toxicity and recovery status of such soils, since they represent a different ecological niche and showed an avoidance response to refinery waste. The plants were not very sensitive to refinery sludge and presented mixed results. Lettuce and grass were affected most by the sludge, while beans were the most resistant. With the addition of low concentrations of sludge to the substrate, the growth rate of beans was even stimulated.

Heavy Metal Uptake of Acacia from Tailing soil in Abandoned Jangun Mine, Korea

장군광산은 과거 갱도채굴한 폐금속광산으로 위치는 $N36^{\circ}$ 51'31.59, $E129^{\circ}$ 03'38.91에 위치하고 있다. 산사면에 적치해 놓은 광미 적치장은 상부에 오염되지 않은 토양으로 약 20 cm 정도 복토한 후 아카시아를 식재해 놓은 상태이다. 광미 적치장에 식재해 놓은 아카시아는 대략 15년생 정도이다. 광미 적치장에서 채취한 토양시료의 중금속 농도는 As (66.43-9325.34 mg/kg), Cd (0.96-1.09 mg/kg), Cu (16.90-57.60 mg/kg), Pb (57.33-945.67 mg/kg), Zn (154.48-278.61 mg/kg)으로 비오염 토양인 대조군의 As (38.98 mg/kg), Cd (0.42 mg/kg), Cu (10.26 mg/kg), Pb (8.21 mg/kg), Zn (46.74 mg/kg) 보다 훨씬 높다. 가장 오염도가 높은 토양에 식재된 아카시아의 잎에서의 As, Cd, Cu, Pb, Zn의 농도는 각각 165.95, 0.04, 10.68, 3.18, 48.11 mg/kg이다. 비오염 토양에 식재되어 있는 아카시아의 잎에서의 중금속 농도는 As 1.31mg/kg, Cu 3.90 mg/kg, Pb 0.22 mg/kg, Zn 11.01 mg/kg이다. 아카시아에서의 중금속의 농집도는 껍질과 잎에서 높으며 심재와 변재에서 낮은 경향을 나타낸다. 【Janggun mine (longitude $129^{\circ}$ 03'38.91 Latitude $36^{\circ}$ 51'31.59) had been operated as an underground mine for last few decades. As the part of the remediation process, the surface of tailing dump was covered with uncontaminated soil about 20 cm in depth and acacia trees were planted. Heavy metal uptake of acacia from tailing soil has continued for the past 15 years. Heavy metal concentration ranges of tailing soil that contaminated with As (66.43-9325.34 mg/kg), Cd (0.96-1.09 mg/kg), Cu (16.90-57.60 mg/kg), Pb (57.33-945.67 mg/kg), and Zn (154.48-278.61 mg/kg) have higher than those of control soil As (38.98 mg/kg), Cd (0.42 mg/kg), Cu (10.26 mg/kg), Pb (8.21 mg/kg), Zn (46.74 mg/kg). The As, Cd, Cu, Pb and Zn concentrations of leaf of acacia in highly contaminated tailing dump were 165.95, 0.04, 10.68, 3.18, 48.11 mg/kg, respectively. The metal contents of leaf of acacia tree that obtained from uncontaminated control soil are 1.31 of As, 3.90 of Cu, 0.22 of Pb and 11.01 mg/kg of Zn. It was investigated that in the acacia tree, heavy metals such as As, Cu, Pb and Zn tend to be more highly concentrated in bark and leaf, compared with sapwood and heartwood.】

METAL UPTAKE AND ALLOCATION IN TREES GROWN ON CONTAMINATED LAND: IMPLICATIONS FOR BIOMASS PRODUCTION

Phytostabilization aims to reduce environmental and health risks arising from contaminated soil. To be economically attractive, plants used for phytostabilization should produce valuable biomass. This study investigated the biomass production and metal allocation to foliage and wood of willow (Salix viminalis L.), poplar (Populus monviso), birch (Betula pendula), and oak (Quercus robur) on five different soils contaminated with trace elements (TE), with varying high concentrations of Cu, Zn, Cd, and Pb as well as an uncontaminated control soil. In the treatment soils, the biomass was reduced in all species except oak. There was a significant negative correlation between biomass and foliar Cd and Zn concentrations, reaching up to 15 mg Cd kg−1 and 2000 mg Zn kg −1 in willow leaves. Lead was the only TE with higher wood than foliage concentrations. The highest Pb accumulation occurred in birch with up to 135 mg kg −1 in wood and 78 mg kg −1 in foliage. Birch could be suitable for phytostabilization of soils with high Cd and Zn but low Pb concentrations, while poplars and willows could be used to stabilise soils with high Cu and Pb and low Zn and Cd concentrations.

Tomato and parsley growth, arsenic uptake and translocation in a contaminated amended soil

Mining is a source of trace element contamination of neighbouring soils. This study determined the influence of soil amendments (iron oxides, Fe; organic matter, OM; and calcium phosphate, PCa) on arsenic uptake and translocation by tomato and parsley growth in an As-contaminated soil. The original contaminated soil without amendments was collected in the vicinity of the abandoned Santo António mine (Penedono, Portugal), which was a very important gold and arsenic mining centre in the middle fifties of the last century. An uncontaminated soil was also used as control. Growth parameters measured were plant height, length of 4th leaf (tomato only) and dry matter accumulation. Arsenic concentration in plant components was also determined, and human health risks related to the edible tissues were calculated. Results showed that arsenic availability in the soil varied with the amendments applied: OM and PCa increased arsenic availability, while the opposite effect was found with Fe (at 3gkg−1). Soil amended with iron oxides showed no positive effect on plant growth compared with the original soil with no amendments. Amongst all the amendments, OM led to the best results relatively to all growth parameters measured in tomato, including dry matter accumulation and fruit yield. Parsley growth was very small except in the PCa at 12gkg−1. Parsley translocated more arsenic to shoots, while tomato retained a greater proportion in roots. The health risk for adults and adolescents was within acceptable limits with an average weekly intake of 500g of tomato and 20g of parsley, although the arsenic concentration in edible tissues was still considerable greater than in plants grown in the uncontaminated control soil.

Genetic adaptation of earthworms to copper pollution: is adaptation associated with fitness costs in Dendrobaena octaedra?

Exposure to copper pollution affects reproduction, growth and survival of earthworms. It is known that earthworms can cope with high copper burdens, but the distinction between physiological acclimation and evolutionary heritable changes and associated fitness consequences of the adaption to long-term copper exposure has rarely been studied. To investigate adaptation of earthworm populations of Dendrobaena octaedra to copper contamination, three populations from polluted soil were studied and compared to three unpolluted reference sites. Adult worms were collected at all six sites and cultured in uncontaminated control soil in the laboratory, where life-history traits were studied and F1-generations were produced. The newly hatched F1-generation worms were placed in uncontaminated control or copper-spiked soil to study if the adaptation was due to acclimation or genetic inheritance. This experiment showed that populations from polluted areas generally had a higher individual growth rate, reduced time to maturity, increased reproduction, and also increased mortality compared to the reference populations in both control and copper-spiked soil. The differences in life-history traits indicate that natural selection has resulted in genetic adaptation to copper pollution in the exposed populations. The population growth rates suggest a weak detrimental effect on population growth rate of being exposed to copper for both type of populations, but no sign of cost. On the contrary, estimates of population growth rates integrating all life-history traits showed that copper adapted populations perform on average relatively better than reference populations in both uncontaminated and copper-spiked soil.

Soil quality assessment 33 months after crude oil spillage and clean-up

A post-impact assessment, 33 months after oil spillage and initial clean-up, was conducted on selected soil quality indices. The ultimate aim of the study was to ascertain whether there was any need for further clean-up or remediation options. The results obtained showed that the mean soil pH in the oil contaminated area was 5.93±0.18, (electrical conductivity 123.15± 1.60μScm−1) total petroleum hydrocarbons (TPH, 581.02 mg kg−1) oil and grease (492.55 mg kg−1), polynuclear aromatic hydrocarbons (PAH, 20.41 mg kg−1). Pb (2.34 mg kg−1), Cd (1.93 mg kg−1) significant correlation exists between TPH, and oil and grease (0.97), TPH and PAH (0.64), TPH and hydrocarbon degrading bacteria (0.72). All these values were significantly higher than the uncontaminated (control) soils. The investigation revealed that there were significantly high levels of diffuse petroleum hydrocarbons in the contaminated area. Further monitoring and characteristics of the hydrocarbon levels is recommended while a synergistic bioremedia-tion approach should be the first step in the reclamation process.

Determination of Microbial Carbon Sources and Cycling during Remediation of Petroleum Hydrocarbon Impacted Soil Using Natural Abundance 14C Analysis of PLFA

In a petroleum impacted land-farm soil in Sarnia, Ontario, compound-specific natural abundance radiocarbon analysis identified biodegradation by the soil microbial community as a major pathway for hydrocarbon removal in a novel remediation system. During remediation of contaminated soils by a plant growth promoting rhizobacteria enhanced phytoremediation system (PEPS), the measured Delta(14)C of phospholipid fatty acid (PLFA) biomarkers ranged from -793 per thousand to -897 per thousand, directly demonstrating microbial uptake and utilization of petroleum hydrocarbons (Delta(14)C(PHC) = -1000 per thousand). Isotopic mass balance indicated that more than 80% of microbial PLFA carbon was derived from petroleum hydrocarbons (PHC) and a maximum of 20% was obtained from metabolism of more modern carbon sources. These PLFA from the contaminated soils were the most (14)C-depleted biomarkers ever measured for an in situ environmental system, and this study demonstrated that the microbial community in this soil was subsisting primarily on petroleum hydrocarbons. In contrast, the microbial community in a nearby uncontaminated control soil maintained a more modern Delta(14)C signature than total organic carbon (Delta(14)C(PLFA) = +36 per thousand to -147 per thousand, Delta(14)C(TOC) = -148 per thousand), indicating preferential consumption of the most modern plant-derived fraction of soil organic carbon. Measurements of delta(13)C and Delta(14)C of soil CO(2) additionally demonstrated that mineralization of PHC contributed to soil CO(2) at the contaminated site. The CO(2) in the uncontaminated control soil exhibited substantially more modern Delta(14)C values, and lower soil CO(2) concentrations than the contaminated soils, suggesting increased rates of soil respiration in the contaminated soils. In combination, these results demonstrated that biodegradation in the soil microbial community was a primary pathway of petroleum hydrocarbon removal in the PEPS system. This study highlights the power of natural abundance radiocarbon for determining microbial carbon sources and identifying biodegradation pathways in complex remediation systems.

Comparison of archaeal and bacterial community structures in heavily oil-contaminated and pristine soils

Archaeal and bacterial community structures in heavily oil-contaminated and pristine soils were compared using denaturing gradient gel electrophoresis and 16S rRNA gene libraries. The results showed that archaeal diversity was more complex in the contaminated soil than in the uncontaminated control soil. Archaeal populations in the contaminated soil consisted mainly of Euryarchaeota, with abundant methanogen-like operational taxonomic units (OTUs) and OTUs related to the phylogenetically diverse group, candidate division I, corresponding to rice cluster V. In contrast, only halophilic archaea were found in the pristine soil. Bacterial community structures also differed significantly between the contaminated and pristine soils. More clones from the contaminated soil were related to known hydrocarbon-degrading bacteria, implying that microorganisms with the potential to degrade petroleum were well-established. These results provide further insights into the composition of microbial communities in oil-contaminated soils.