The multifactorial assessment of the Zn impact on high and low temperature stress towards wheat seedling growth under diverse moisture conditions (optimal and wet) in three soils

Anthropogenic activities leading to chemical contamination of soil and global climate change may increase the level of stress for plants. Recent decades studies (mainly two-factors) have reported that the ecotoxicity of soil contaminants could be modified by climate factors. To date, little is known about: the combined climate-chemical stress on plants; the interaction of chemicals with high soil moisture conditions; the impact of soil properties on the combined climate-chemical stress and questions regarding the response of organisms to combined effect of all key factors influencing the ecotoxicity of chemicals under field conditions remain unanswered. Our study sought to fill the knowledge gap on the multifactorial interaction of four main factors encounter in polluted areas (soil chemical contamination: heavy metal (Zn); temperature: 10, 23, 35 °C, moisture: 55, 80%WHC; soil properties). The assessment of combined effect of multiple stressors based on the multiple ANCOVA model (n = 108; adjusted R² = 0.68) and calculated indicators showed: 1) all studied factors significantly interacted and influenced the phytotoxic effect of Zn; 2) Zn modified the plant response to temperature stress depending on moisture conditions and soil properties. This study improves methods for assessing the hazardous effects of soil chemical contamination in the real environment.

Triad-based screening risk assessment of the agricultural area exposed to the long-term PAHs contamination

The aim of the study was ecological risk assessment (ERA) of the agricultural soils located in the vicinity of the highly industrialized area and exposed to different emission sources of polycyclic aromatic hydrocarbons (PAHs). In this study, we demonstrated the combination of generic and site-specific ERA approach for screening assessment and delineation of the area of a high ecological risk. Generic approach was based on a hazard quotient and indicated that 62% of the research area needs further assessment. For site-specific evaluation, the Triad approach was utilized. Information from three lines of evidence (LoE): chemical, ecotoxicological and ecological, was integrated into one environmental risk (EnvRI) index. The chemical risk was derived from toxic pressure coefficients based on the total PAHs concentration. The ecotoxicological LoE included an acute toxicity testing: the luminescent bacteria Aliivibrio fischeri activity in both liquid- and solid-phase samples and the ability of crustacean Thamnocephalus platyurus to food uptake. The ecological LoE comprised microbial parameters related to soil respiration and enzymatic activity. Integrated EnvRI index ranged from 0.44 to 0.94 and was mainly influenced by high values of chemical LoE risk, while the ecotoxicological and ecological LoE indicated no or low risk. Due to the relatively high uncertainty associated with the contradictory information given by LoEs, there is the need to confirm potential risk in a tier 2 analysis.

The drought and high wet soil condition impact on PAH (phenanthrene) toxicity towards nitrifying bacteria

A few previous studies showed that the low soil moisture could interact with the toxic effect of the polycyclic aromatic hydrocarbons (PAHs) towards animals (mostly invertebrates). In the present research the impact of the soil moisture in the wide range (from the drought to high moisture conditions) in three different soil materials on toxic effect of the PAH (phenanthrene) towards soil microorganisms (nitrifying bacteria activity) was evaluated. The three dry soil materials were artificially contaminated with phenanthrene (0, 1, 10, 100 and 1000 mg kg^-1 dry mass of soil) and moistened to the varied levels of the soil moisture (30% WHC (dry), 55% WHC (optimal) and 80% WHC (highly wet conditions)). After 7 days incubation, the nitrification potential was measured. The results of the proposed ANCOVA multiple regression model (adjusted R² = 0.91), showed that the increase of soil moisture enhanced the toxicity of the phenanthrene towards nitrification potential and this combined moisture-phenanthrene effect was soil dependent. Therefore, the effect of the soil moisture in combination with the soil diversity should not be missed in the ecotoxicological risk assessment of the PAHs.

Influence of temperature on phenanthrene toxicity towards nitrifying bacteria in three soils with different properties

This study focused on the combined effect of environmental conditions (temperature) and contamination (polycyclic aromatic hydrocarbons, PAHs) on the activity of soil microorganisms (nitrifying bacteria). Phenanthrene (Phe) at five contamination levels (0, 1, 10, 100 and 1000 mg kg(-1) dry mass of soil) was employed as a model PAH compound in laboratory experiments that were conducted at three temperatures (i.e., 20 °C (recommended by ISO 15685 method), 15 and 30 °C). Three soils with different properties were used in these studies, and the activity of the nitrifying bacteria was assessed based on nitrification potential (NP) determinations. For the statistical evaluation of the results, the ANCOVA (analysis of covariance) method for three independent variables (i.e., temperature, phenanthrene concentration, soil matrix (as a qualitative variable)) and their interactions was employed. The results indicated on the significant interaction of all studied factors. Temperature influenced the toxicity of Phe towards NP, and this effect was related to the Phe concentration as well as was varied for the different soils. A low content of soil organic matter (controlling bioavailability of phenanthrene to soil microorganisms) enhanced the combined effect of temperature and Phe toxicity, and a high biological activity of the soil (high NP values) increased the effect of high temperature on the Phe stimulatory influence. The results indicate that the temperature should not be neglected in tests evaluating PAH ecotoxicity, especially for reliable ecological risk assessment.

The levels and composition of persistent organic pollutants in alluvial agriculture soils affected by flooding

The concentrations and composition of persistent organic pollutants (POPs) were determined in alluvial soils subjected to heavy flooding in a rural region of Poland. Soil samples (n = 30) were collected from the upper soil layer from a 70-km(2) area. Chemical determinations included basic physicochemical properties and the contents of polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and polycyclic aromatic hydrocarbons (PAHs, 16 compounds). The median concentrations of Σ7PCB (PCB28 + PCB52 + PCB101 + PCB118 + PCB138 + PCB153 + PCB180), Σ3HCH (α-HCH + β-HCH + γ-HCH) and Σ3pp'(DDT + DDE + DDD) were 1.60 ± 1.03, 0.22 ± 0.13 and 25.18 ± 82.70 μg kg(-1), respectively. The median concentrations of the most abundant PAHs, phenanthrene, fluoranthene, pyrene, benzo[b]fluoranthene and benzo[a]pyrene were 50 ± 37, 38 ± 27, 29 ± 30, 45 ± 36 and 24 ± 22 μg kg(-1), respectively. Compared with elsewhere in the world, the overall level of contamination with POPs was low and similar to the levels in agricultural soils from neighbouring countries, except for benzo[a]pyrene and DDT. There was no evidence that flooding affected the levels of POPs in the studied soils. The patterns observed for PAHs and PCBs indicate that atmospheric deposition is the most important long-term source of these contaminants. DDTs were the dominant organochlorine pesticides (up to 99%), and the contribution of the parent pp' isomer was up to 50 % of the ΣDDT, which indicates the advantage of aged contamination. A high pp'DDE/pp'DDD ratio suggests the prevalence of aerobic transformations of parent DDT. Dominance of the γ isomer in the HCHs implies historical use of lindane in the area. The effect of soil properties on the POP concentrations was rather weak, although statistically significant links with the content of the <0.02-mm fraction, Ctotal or Ntotal were observed for some individual compounds in the PCB group.

Concentrations, sources, and spatial distribution of individual polycyclic aromatic hydrocarbons (PAHs) in agricultural soils in the Eastern part of the EU: Poland as a case study

Soils from agricultural areas receive unsatisfactory attention as regards the contamination with organic pollutants. To answer those needs the contents of the sixteen individual PAH compounds were determined (GC/MS technique) in agricultural soils in Poland. The samples (n=216) were collected from the upper layer of arable land in the year 2005. Half of the samples represented typical rural areas, while the rest derived from the territories potentially subjected to the urban/industrial pressure of various intensity. The mean (geometric) content of individual compounds varied from 1 microg kg(-1) for acenaphtylene to 55 microg kg(-1) for fluoranthene with the highest contributions (11.6%-12.9%) of phenanthrene, fluoranthene and pyrene. Higher molecular weight PAHs (4 rings) were strongly linked mutually and with the summation operator 16PAHs. They contributed substantially (73%) to the overall content of PAHs, which implies domination of anthropogenic sources. The calculated molecular indexes suggest that most of those PAHs derive from the combustion of coal, the main energy source in Poland. Simultaneously, the concentrations of lower molecular weight compounds seem to reflect the background, "natural" PAH compounds, which represent mainly atmospherically distributed emission. The division of the samples into groups describing geographical regions and landscape type enabled evaluation of the spatial trends in contamination of soils with PAH compounds. The most pronounced effect of spatial parameters corresponded to PAHs >4 rings, while lower molecular weight compounds showed more homogeneous concentration through the country.

Monitoring of the total content of polycyclic aromatic hydrocarbons (PAHs) in arable soils in Poland

The paper provides comprehensive information on the level of contamination of arable soils in Poland with polycyclic aromatic hydrocarbons (PAHs). Extensive monitoring studies were carried out to determine the content of the 16 priority PAHs in 216 soil samples collected in 2005 throughout arable lands (0-20 cm layer) in Poland. Locations of sampling points reflected the differences in regional industrialisation and urbanisation as well as in the characteristics of soils. The content of Sigma16PAHs ranged from 80 to 7264 microg kg(-1) with a median of 395 microg kg(-1) and with a dominance of 4-6 rings hydrocarbons (74% of total PAHs). Soil properties affected the PAHs content to a limited extend. The organic matter content was the only parameter correlated significantly (although weakly) with the concentrations of Sigma16PAHs; the strength of this relationship was more pronounced in soils with elevated OM content. The various molecular markers pointed to a prevailing pyrogenic origin of the PAHs in Polish arable soils, with minor contribution from liquid fuels combustion and traffic emissions. Two different Polish systems for classification of agricultural soils (providing for the content of Sigma9PAHs and Sigma13PAHs) indicate that the percentage of contaminated arable soils in Poland does not exceed 10%. Multivariate methods enabled an evaluation of spatial trends in Sigma16PAHs concentrations, an identification of regions with very low PAHs content (East part of the country), and a recognition of small industrial/urbanised areas of higher risk.

Assessing the bioavailability of phenanthrene to soil microorganisms using the Tenax extraction method

The Tenax TA extraction technique followed by gas chromatography mass spectrometry (GC-MS) determinations was used to assess the actually bioavailable fraction of phenanthrene (ABF-Phe) in three different soils freshly contaminated with this compound at levels of 10, 100, and 1,000 mg kg(-1). The results were related to the ecotoxic effect of phenanthrene on soil nitrifying bacteria. Nitrification potential measurements were applied as an ecotoxicity end point. A strong positive linear relationship (r2 = 0.95) was obtained between the content of the actually bioavailable phenanthrene fraction and the inhibition of nitrifying bacteria activity.

[Effect of the selected organic solvents on the activity of soil microorganisms]

The aim of the study was to evaluate the effect of organic solvents, commonly used in ecotoxicity studies on the activity of soil microorganisms. Two solvents, often applied in the studies of the effects of hydrophobic organic contaminants in the environment, acetone and dichloromethane, were employed in the experiments. The evaluation of the effects of the solvents was based on the measurements of two parameters describing the overall activity of soil microorganisms (activity of dehydrogenases) and the activity of the specific group of nitrification bacteria (potential of nitrification). The experiments included different laboratory conditions (soil material properties, time of contact, methods of solvent amendment). The results show that the solvents introduced to soils in the amount commonly used in the ecotoxicity studies (10-20 cm3 kg(-1)) may inhibit the activity of soils microorganisms: the effect was particularly visible in the case of potential of nitrification determinations. Employment of the method of gradual application of the solvents to soils led to significant decrease of those negative effects.

Ecotoxic effect of phenanthrene on nitrifying bacteria in soils of different properties

Information on ecotoxicity of organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs), in terrestrial environment is needed for establishing soil quality criteria and for risk assessment purposes. An ecotoxic effect of a model PAH compound (phenanthrene) toward soils microorganisms (nitrifying bacteria) was evaluated in 50 different soils. The soil samples were collected from agricultural land in four regions of Poland with varying levels of industrialization (Slaskie, Dolnoslaskie, Podlaskie, and Lubelskie voievodeships). Soils were characterized for basic physicochemical properties (texture, organic matter content, pH(KCl), total nitrogen content, total sorption capacity) and the content of contaminants including PAHs (73-800 microg kg(-1)), Pb (6-720 mg kg(-1)), and Zn (9-667 mg kg(-1)). Ecotoxicity of phenanthrene (applied at 10, 100, 500, and 1000 mg kg(-1)) to soils microorganisms was evaluated in laboratory studies in control conditions (incubation of soils for 7 d at 20 +/- 2 degrees C). Nitrification potential was used as the ecotoxicity measurements end point. The EC50 values (146-1670 mg kg(-1)) calculated from the square root-X linear regression model differed significantly in various soils, although it was difficult to establish a causative relationship between soil physicochemical characteristic and phenanthrene toxicity. A significant factor in the assessment of soils vulnerability to the effect of phenanthrene was level of soil contamination, particularly with PAHs. Soils with previous contamination were more susceptible (mean EC50, 325 mg kg(-1)) than soils from uncontaminated, rural areas (mean EC50, 603 mg kg(-1)).

Habitat function of agricultural soils as affected by heavy metals and polycyclic aromatic hydrocarbons contamination

Ecotoxic activity of soils polluted with polycyclic aromatic hydrocarbon (PAH) and heavy metals (HM) was evaluated in pot and laboratory experiments. Plants and soil microorganisms were chosen as test organisms and six different soil materials were used in the study. The applied levels of HM and PAH were aimed to reflect environmental conditions in the "worst case" situation. Zn(2+), Pb(2+) and Cd(2+) were introduced to the soils as an aqueous solution of the mixture of salts at the concentrations corresponding to 1000, 500 and 3 mg kg(-1), respectively. Mixture of four PAH compounds (flourene, anthracene, pyrene and chrysene) as a CH(2)Cl(2) solution was applied at levels of 10-100 mg summation operator 4PAH kg(-1). Population and activity of soil microflora was evaluated as measured of total bacteria counts, intensity of respiration and enzyme activity (dehydrogenases and phosphatases). Effect on plants was evaluated on the base of the growth (plant at an early stage of their development) and yield (mature plant) measurements. The results indicate that combined effect of PAH and heavy metals on soil microorganisms activity and on some plants at an early stage of their development can be stronger than in soils amended with HM or PAH separately. Reaction of tested organisms was related to soil properties, PAH concentration, time and plant species. Mature plants (maize) were insensitive to the applied levels of both group of contaminants.

The effect of temperature on the rate of disappearance of polycyclic aromatic hydrocarbons from soils

The effect of temperature on the range and rate of disappearance of four polycyclic aromatic hydrocarbons (PAHs; fluorene, anthracene, pyrene and chrysene) added as a mixture of pure compounds to two different soils (light loam and loamy sand) was investigated over 180 days in a laboratory experiment. An increase in temperature from 10 to 25 degrees C enhanced the losses of all four PAHs from both soils. The effect of temperature on the rate of PAH disappearance depended on the physico-chemical properties of the compound and of the soil. The long half-lives at lower temperatures as obtained in the laboratory tests may suggest high persistence of higher molecular weight PAHs under some field conditions.