No effect of digestate amendment on Cs-137 and Sr-90 translocation in lysimeter experiments.

The soil-plant transfer of Cs-137 and Sr-90 in different crops was determined with respect to the present-day amendment practice of using digestate from biogas fermenters. The studies were performed using large lysimeters filled with undisturbed luvisol monoliths. In contrast to the conservative tracer, Br-, neither of the studied radionuclides showed a significant vertical translocation nor effect of the applied digestate amendment compared to a non-amended control was found. Furthermore, no significant plant uptake was measured for both nuclides in wheat or oat as indicated by the low transfer factors between soil-shoot for Cs-137 (TF 0.001-0.010) and for Sr-90 (0.10-0.51). The transfer into nutritionally relevant plant parts was even lower with transfer factors for soil-grain for Cs-137 (TF 0.000-0.001) and for Sr-90 (0.01-0.06). Hence, the amendment with biogas digestate is unfortunately not an option to further reduce plant uptake of these radionuclides in agricultural crops, but it does not increase plant uptake either.

Dissipation of bentazone, pyrimethanil and boscalid in biochar and digestate based soil mixtures for biopurification systems.

Biopurification systems, such as biofilters, are biotechnological tools to prevent point sources of pesticide pollution stemming from on-farm operations. For the purification processes pesticide sorption and mineralization and/or dissipation are essential and both largely depend on the type of filling materials and the pesticide in use. In this paper the mineralization and dissipation of three contrasting (14)C-labeled pesticides (bentazone, boscalid, and pyrimethanil) were investigated in laboratory incubation experiments using sandy soil, biochar produced from Pine woodchips, and/or digestate obtained from anaerobic digestion process using maize silage, chicken manure, beef and pig urine as feedstock. The results indicate that the addition of digestate increased pesticide mineralization, whereby the mineralization was not proportional to the digestate loads in the mixture, indicating a saturation effect in the turnover rate of pesticides. This effect was in correlation with the amount of water extractable DOC, obtained from the digestate based mixtures. Mixing biochar into the soil generally reduced total mineralization and led to larger sorption/sequestration of the pesticides, resulting in faster decrease of the extractable fraction. Also the addition of biochar to the soil/digestate mixtures reduced mineralization compared to the digestate alone mixture but mineralization rates were still higher as for the biochar/soil alone. In consequence, the addition of biochar to the soil generally decreased pesticide dissipation times and larger amounts of biochar led to high amounts of non-extractable residues of pesticide in the substrates. Among the mixtures tested, a mixture of digestate (5%) and biochar (5%) gave optimal results with respect to mineralization and simultaneous sorption for all three pesticides.

Atrazine soil core residue analysis from an agricultural field 21 years after its ban.

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) groundwater monitoring in the Zwischenscholle aquifer in western Germany revealed concentrations exceeding the threshold value of 0.1 µg L and increasing concentration trends even 20 yr after its ban. Accordingly, the hypothesis was raised that a continued release of bound atrazine residues from the soil into the Zwischenscholle aquifer in combination with the low atrazine degradation in groundwater contributes to elevated atrazine in groundwater. Three soil cores reaching down to the groundwater table were taken from an agricultural field where atrazine had been applied before its ban in 1991. Atrazine residues were extracted from eight soil layers down to 300 cm using accelerated solvent extraction and analyzed using liquid chromatography-tandem mass spectrometry. Extracted atrazine concentrations ranged between 0.2 and 0.01 µg kg for topsoil and subsoil, respectively. The extracted mass from the soil profiles represented 0.07% of the applied mass, with 0.01% remaining in the top layer. A complete and instantaneous remobilization of atrazine residues and vertical mixing with the groundwater body below would lead to atrazine groundwater concentrations of 0.068 µg L. Considering the area where atrazine was applied in the region and assuming instantaneous lateral mixing in the Zwischenscholle aquifer would result in a mean groundwater concentration of 0.002 µg L. A conservative estimation suggests an atrazine half-life value of about 2 yr for the soil zone, which significantly exceeds highest atrazine half-lives found in the literature (433 d for subsurface soils). The long-term environmental behavior of atrazine and its metabolites thus needs to be reconsidered.

Transfer of atrazine degradation capability to mineralize aged ¹4C-labeled atrazine residues in soils.

The degradation of environmentally long-term aged (22 years) ¹4C-labeled atrazine residues in soil stimulated by inoculation with atrazine-adapted soil from Belgium, the United States (U.S.), and Brazil at two different moisture regimes (50% WHCmax/slurried conditions) was evaluated. Inoculation of the soil containing the aged ¹4C-labeled atrazine residues with 5, 50, and 100% (w/w) Belgian, U.S., or Brazilian atrazine-adapted soil increased ¹4C-atrazine residue mineralization by a factor of 3.1-13.9, depending upon the amount of atrazine-adapted soil inocula and the moisture conditions. Aged ¹4C-atrazine residue mineralization varied between 2 and 8% for Belgian and between 1 and 2% for U.S. and Brazilian soil inoculum at 50% WHCmax but was increased under slurried conditions, accounting for 8-10% (Belgian soil), 2-7% (Brazilian soil), and 3% (American soil). The results show that an increased degradation of long-term aged ¹4C-labeled atrazine residues is possible by the transfer of atrazine-adapted soil microflora from different soils and regions to non-adapted soil.

Radiation-induced impacts on the degradation of 2,4-D and the microbial population in soil microcosms.

In a soil microcosm experiment, the influence of low-level (137)Cs and (90)Sr contamination on the degradation of (14)C-ring-labeled 2,4-dichlorophenoxyacetic acid (2,4-D) was studied. Two differently treated soils (one native soil and one soil sterilized and reinoculated with a biotic soil aliquot) were artificially contaminated with various concentrations of (137)Cs and (90)Sr as nitrate salts. The cumulative doses increased up to 4 Gy for 30 days of incubation in soil microcosms. Changes in microbial community structure were observed with help of the denaturing gradient gel electrophoresis (DGGE). A radiation-induced impact appeared only in the microcosms treated with 30 times the maximum contamination appearing in the exclusion zone around reactor 4 in Chernobyl. In contrast to the less contaminated soils, the mineralization of 2,4-D was delayed for 4 days before it recovered. Slight shifts in the microbial communities could be traced to radiation effects. However, other parameters had a major impact on mineralization and community structure. Thus the sterilization and reinoculation and, of course, application of the 2,4-D were predominantly reflected in the (14)CO(2) emissions and the DGGE gel patterns.

Biochar-mediated [14C]atrazine mineralization in atrazine-adapted soils from Belgium and Brazil.

Biochar addition to soil has been reported to reduce the microbial degradation of pesticides due to sorption of the active compound. This study investigated whether the addition of hardwood biochar alters the mineralization of (14)C-labeled atrazine in two atrazine-adapted soils from Belgium and Brazil at different moisture regimens. Biochar addition resulted in an equally high or even in a significantly higher atrazine mineralization compared to the soils without biochar. Statistical analysis revealed that the extent of atrazine mineralization was more influenced by the specific soil than by the addition of biochar. It was concluded that biochar amendment up to 5% by weight does not negatively affect the mineralization of atrazine by an atrazine-adapted soil microflora.

Do Chernobyl-like contaminations with (137)Cs and (90)Sr affect the microbial community, the fungal biomass and the composition of soil organic matter in soil?

(137)Cs and (90)Sr are the main radionuclides responsible for contamination of agricultural soils due to core melts in nuclear power plants such as Chernobyl or Fukushima. The present study focused on effects of Chernobyl-like contaminations on the bacterial and fungal community structure, the fungal biomass and the formation of soil organic matter in native and in sterilized and reinoculated soils. 2% wheat straw [m/m] was applied to a typical agricultural soil, artificially contaminated with (137)Cs and (90)Sr, and it was then incubated in microcosms for three months at 20 °C and 50% of the water-holding capacity. The development of the microbial communities was monitored with 16S and 18S rDNA denaturing gradient gel electrophoresis (DGGE). The quantification of the ergosterol content was used as a proxy for changes in the fungal biomass. Changes in the soil organic matter were determined using the (13)C cross polarization/magic angle spinning nuclear magnet resonance technique ((13)C-CP/MAS NMR). Slight but significant population shifts in the DGGE gel patterns could be related to the applied radionuclides. However, radiation-induced impacts could not be seen in either the chemical composition of the soil organic matter or in the development of the fungal biomass. Impacts caused by sterilization and reinoculation prevailed in the microcosms of the present study. Contaminations with (137)Cs or (90)Sr up to 50-fold that of the hotspots occurring in Chernobyl led to minor changes in soil microbial functions suggesting a strong resilience of natural soils with respect to radioactive contamination.

Dry-wet cycles increase pesticide residue release from soil.

Soil drying and rewetting may alter the release and availability of aged pesticide residues in soils. A laboratory experiment was conducted to evaluate the influence of soil drying and wetting on the release of pesticide residues. Soil containing environmentally long-term aged (9-17 years) (14) C-labeled residues of the herbicides ethidimuron (ETD) and methabenzthiazuron (MBT) and the fungicide anilazine (ANI) showed a significantly higher release of (14) C activity in water extracts of previously dried soil compared to constantly moistened soil throughout all samples (ETD: p < 0.1, MBT and ANI: p < 0.01). The extracted (14) C activity accounted for 44% (ETD), 15% (MBT), and 20% (ANI) of total residual (14) C activity in the samples after 20 successive dry-wet cycles, in contrast to 15% (ETD), 5% (MBT), and 6% (ANI) in extracts of constantly moistened soils. In the dry-wet soils, the dissolved organic carbon (DOC) content correlated with the measured (14) C activity in the aqueous liquids and indicated a potential association of DOC with the pesticide molecules. Liquid chromatography MS/MS analyses of the water extracts of dry-wet soils revealed ETD and MBT in detectable amounts, accounting for 1.83 and 0.01%, respectively, of total applied water-extractable parent compound per soil layer. These findings demonstrate a potential remobilization of environmentally aged pesticide residue fractions from soils due to abiotic stresses such as wet-dry cycles.

Long-term persistence of various 14C-labeled pesticides in soils.

The fate of the 14C-labeled herbicides ethidimuron (ETD), methabenzthiazuron (MBT), and the fungicide anilazine (ANI) in soils was evaluated after long-term aging (9-17 years) in field based lysimeters subject to crop rotation. Analysis of residual 14C activity in the soils revealed 19% (ETD soil; 0-10 cm depth), 35% (MBT soil; 0-30), and 43% (ANI soil; 0-30) of the total initially applied. Accelerated solvent extraction yielded 90% (ETD soil), 26% (MBT soil), and 41% (ANI soil) of residual pesticide 14C activity in the samples. LC-MS/MS analysis revealed the parent compounds ETD and MBT, accounting for 3% and 2% of applied active ingredient in the soil layer, as well as dihydroxy-anilazine as the primary ANI metabolite. The results for ETD and MBT were matching with values obtained from samples of a 12 year old field plot experiment. The data demonstrate the long-term persistence of these pesticides in soils based on outdoor trials.

Effects of low-level radioactive soil contamination and sterilization on the degradation of radiolabeled wheat straw.

After the explosion of reactor 4 in the nuclear power plant near Chernobyl, huge agricultural areas became contaminated with radionuclides. In this study, we want to elucidate whether (137)Cs and (90)Sr affect microorganisms and their community structure and functions in agricultural soil. For this purpose, the mineralization of radiolabeled wheat straw was examined in lab-scale microcosms. Native soils and autoclaved and reinoculated soils were incubated for 70 days at 20 °C. After incubation, the microbial community structure was compared via 16S and 18S rDNA denaturing gradient gel electrophoresis (DGGE). The radioactive contamination with (137)Cs and (90)Sr was found to have little effect on community structure and no effect on the straw mineralization. The autoclaving and reinoculation of soil had a strong influence on the mineralization and the community structure. Additionally we analyzed the effect of soil treatment on mineralization and community composition. It can be concluded that other environmental factors (such as changing content of dissolved organic carbon) are much stronger regulating factors in the mineralization of wheat straw and that low-level radiation only plays a minor role.

Still present after all these years: persistence plus potential toxicity raise questions about the use of atrazine.

As one of the worlds' most heavily applied herbicides, atrazine is still a matter of controversy. Since it is regularly found in ground and drinking water, as well as in sea water and the ice of remote areas, it has become the subject of continuous concern due to its potential endocrine and carcinogenic activity. Current findings prove long-held suspicions that this compound persists for decades in soil. Due to the high amount applied annually all over the world, the soil burden of this compound is considered to be tremendous, representing a potential long-term threat to the environment. The persistence of chemicals such as atrazine has long been underestimated: Do we need to reconsider the environmental risk?

Metabolism and persistence of atrazine in several field soils with different atrazine application histories.

To assess the potential occurrence of accelerated herbicide degradation in soils, the mineralization and persistence of (14)C-labeled and nonlabeled atrazine was evaluated over 3 months in two soils from Belgium (BS, atrazine-treated 1973-2008; BC, nontreated) and two soils from Germany (CK, atrazine-treated 1986-1989; CM, nontreated). Prior to the experiment, accelerated solvent extraction of bulk field soils revealed atrazine (8.3 and 15.2 µg kg(-1)) in BS and CK soils and a number of metabolites directly after field sampling, even in BC and CM soils without previous atrazine treatment, by means of LC-MS/MS analyses. For atrazine degradation studies, all soils were incubated under different moisture conditions (50% maximum soil water-holding capacity (WHC(max))/slurried conditions). At the end of the incubation, the (14)C-atrazine mineralization was high in BS soil (81 and 83%) and also unexpectedly high in BC soil (40 and 81%), at 50% WHC(max) and slurried conditions, respectively. In CK soil, the (14)C-atrazine mineralization was higher (10 and 6%) than in CM soil (4.7 and 2.7%), but was not stimulated by slurried conditions. The results revealed that atrazine application history dramatically influences its degradation and mineralization. For the incubation period, the amount of extractable atrazine, composed of residues from freshly applied atrazine and residues from former field applications, remained significantly greater (statistical significance = 99.5 and 99.95%) for BS and CK soils, respectively, than the amount of extractable atrazine in the bulk field soils. This suggests that (i) mostly freshly applied atrazine is accessible for a complex microbial community, (ii) the applied atrazine is not completely mineralized and remains extractable even in adapted soils, and (iii) the microbial atrazine-mineralizing capacity strongly depends on atrazine application history and appears to be conserved on long time scales after the last application.

Accelerated degradation of (14)C-atrazine in brazilian soils from different regions.

The repeated use of a given pesticide may induce a selection of the soil microbial population, resulting in a rapid degradation of the respective xenobiotic. Patterns of atrazine degradation (mineralization, formation of metabolites and nonextractable residues (NER)) were evaluated in two Brazilian soils with a history of atrazine application. Results were compared with those obtained from soils that had no agricultural use or herbicide application history. (14)C-Atrazine mineralization in unsaturated treated soils was high. By the 85th day of incubation, 82% of the applied (14)C-atrazine was mineralized in the Rhodic Hapludox and 74% in the Xanthic Haplustox. Mineralization remained low in nontreated soils (

Persistence of 14C-labeled atrazine and its residues in a field lysimeter soil after 22 years.

Twenty-two years after the last application of ring-14C-labeled atrazine at customary rate (1.7 kg ha(-1)) on an agriculturally used outdoor lysimeter, atrazine is still detectable by means of accelerated solvent extraction and LC-MS/MS analysis. Extractions of the 0-10 cm soil layer yielded 60% of the residual 14C-activity. The extracts contained atrazine (1.0 microg kg(-1)) and 2-hydroxy-atrazine (42.5 microg kg(-1)). Extractions of the material of the lowest layer 55-60 cm consisting of fine gravel yielded 93% of residual 14C-activity, of which 3.4 microg kg(-1) was detected as atrazine and 17.7 microg kg(-1) was 2-hydroxy-atrazine. The detection of atrazine in the lowest layer was of almost four times higher mass than in the upper soil layer. These findings highlight the fact that atrazine is unexpectedly persistent in soil. The overall persistence of atrazine in the environment might represent a potential risk for successive groundwater contamination by leaching even after 22 years of environmental exposure.

Different influences of DNA purity indices and quantity on PCR-based DGGE and functional gene microarray in soil microbial community study.

Based on the comparative study of the DNA extracts from two soil samples obtained by three commercial DNA extraction kits, we evaluated the influence of the DNA quantity and purity indices (the absorbance ratios A260/280 and A260/230, as well as the absorbance value A320 indicating the amount of humic substances) on polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) and a functional gene microarray used in the study of microbial communities. Numbers and intensities of the DGGE bands are more affected by the A260/280 and A320 values than by the ratio A260/230 and conditionally affected by the DNA yield. Moreover, we demonstrated that the DGGE band pattern was also affected by the preferential extraction due to chemical agents applied in the extraction. Unlike DGGE, microarray is more affected by the A260/230 and A320 values. Until now, the successful PCR performance is the mostly used criterion for soil DNA purity. However, since PCR was more influenced by the A260/280 ratio than by A260/230, it is not accurate enough any more for microbial community assessed by non-PCR-based methods such as microarray. This study provides some useful hints on how to choose effective DNA extraction method for the subsequent assessment of microbial community.

Spatial distribution and characterization of long-term aged 14C-labeled atrazine residues in soil.

The long-term behavior of the herbicide atrazine and its metabolites in the environment is of continued interest in terms of risk assessment and soil quality monitoring. Aqueous desorption, detection, and quantification of atrazine and its metabolites from an agriculturally used soil were performed 22 years after the last atrazine application. A lysimeter soil containing long-term aged atrazine for >20 years was subdivided into 10 and 5 cm layers (at the lysimeter bottom: soil 0-50 and 50-55 cm; fine gravel 55-60 cm depth, implemented for drainage purposes) to identify the qualitative and quantitative differences of aged (14)C-labeled atrazine residues depending on the soil profile and chemico-physical conditions of the individual soil layers. Deionized water was used for nonexhaustive cold water shaking extraction of the soil. With increasing soil depth, the amount of previously applied (14)C activity decreased significantly from 8.8% to 0.7% at 55-60 cm depth whereas the percentage of desorbed (14)C residues in each soil layer increased from 2% to 6% of the total (14)C activity in the sample. The only metabolite detectable by means of LC-MS/MS was 2-hydroxyatrazine while most of the residual (14)C activity was bound to the soil and was not desorbed. The amount of desorbed 2-hydroxyatrazine decreased with increasing soil depth from 21% to 10% of the total desorbed (14)C residue fraction. The amount of (14)C residues in the soil layers correlated well with the carbon content in the soil and in the aqueous soil extracts ( p value = 0.99 and 0.97, respectively), which may provide evidence of the binding behavior of the aged atrazine residues on soil carbon. The lowest coarse layer (55-60 cm) showed increased residual (14)C activity leading to the assumption that most (14)C residues were leached from the soil column over time.

Bioaccessibility of environmentally aged 14C-atrazine residues in an agriculturally used soil and its particle-size aggregates.

After 22 years of aging under natural conditions in an outdoor lysimeter the bioaccessibility of 14C-labeled atrazine soil residues to bacteria was tested. Entire soil samples as well as sand-sized, silt-sized, and clay-sized aggregates (>20, 20-2, and <2microm aggregate size, respectively) were investigated under slurried conditions. The mineralization of residual radioactivity in the outdoor lysimeter soil reached up to 4.5% of the total 14C-activity after 16 days, inoculated with Pseudomonas sp. strain ADP. The control samples without inoculated bacteria showed a mineralization maximum of only about 1% after 44 days of incubation. Mineralization increased in the clay-sized aggregates up to 6.2% of the total residual 14C-activity within 23 days. With decreasing soil aggregate sizes, residual 14C-activity increased per unit of weight, but only minor differences of the mineralization in the soil and soil size aggregates using mineral-media for incubation was observed. Using additional Na-citrate in the incubation, the extent of mineralization increased to 6.7% in soil after 23 days following incubation with Pseudomonas sp. strain ADP. These results show that long-term aged 14C-atrazine residues are still partly accessible to the atrazine degrading microorganism Pseudomonas sp. strain ADP.

Regiões homogêneas e tamanho de amostra para atributos do clima no Estado de São Paulo, Brasil / Homogeneous regions and sample size for attributes of the climate in São Paulo State, Brazil

Os objetivos deste trabalho foram demarcar regiões homogêneas e estimar o número de anos de avaliações para as variáveis insolação, radiação solar global e radiação fotossinteticamente ativa para o Estado de São Paulo. Utilizaram-se dados da média mensal de insolação, radiação solar e radiação fotossinteticamente ativa de 18 locais do Estado de São Paulo. A homogeneidade das variâncias entre os meses do ano para os 18 locais (variabilidade temporal) e a homogeneidade das variâncias entre os locais em cada mês (variabilidade espacial) foram testadas pelo teste de homogeneidade de Bartlett. Estimou-se o tamanho de amostra para cada local durante o ano. Como resultados há variabilidade temporal e espacial para as estimativas de insolação, radiação solar e radiação fotossinteticamente ativa para os 18 municípios avaliados. Além disso, a variabilidade do tamanho de amostra para a insolação, radiação solar e radiação fotossinteticamente ativa depende do local e da época do ano no Estado de São Paulo.

The purpose of this study was to separate homogeneous regions and to estimate the numbers of years necessary to evaluate the variables: sunshine, global solar radiation and photossintetically active radiation in Sao Paulo State. Monthly data of sunshine, solar radiation and photossintetically active radiation for 18 places in Sao Paulo State were used in the analysis. The homogeneity of the variances among the months for the 18 places (seasonal variability) and the homogeneity of variances among places in each month (spatial variability) were tested by the test of homogeneity of Bartlett. In addition, the sample size for each place was calculated during the year. The results show the existence of seasonal and spatial variability in the estimates of sunshine, solar radiation and photossintetically active radiation for the 18 cities evaluated in Sao Paulo State. Moreover, the variability of the sample size for sunshine, solar radiation and photossintetically active radiation depend on the site and season of the year in Sao Paulo State.

Growth-inhibitory effects of sulfonamides at different pH: dissimilar susceptibility patterns of a soil bacterium and a test bacterium used for antibiotic assays.

The ionic speciation of sulfonamides is pH-driven and this may be crucial for their bioavailability and sorption to soil constituents, as well as for their uptake into bacterial cells. The inhibition behaviour of a bacterial test strain (Pseudomonas aeruginosa; DSM 1117), which was grown in the presence of different concentrations of 8 sulfonamides at pH values from 5 to 8, could be predicted by models that take the speciation of sulfonamides in- and outside of bacterial cells into account. Assuming a pH of 7.5 inside the cells (pH homeostasis), the strongest inhibition was predicted for the lowest external pH and for sulfonamides with the lowest pK(a) values. Growth experiments with Ps. aeruginosa basically reflected this predicted behaviour. However, Pantoea agglomerans -- a bacterial strain isolated from arable soil -- behaved surprisingly different regarding its pH dependency: all sulfonamides showed the strongest effects at pH 7 to 8 instead of being most effective at lowest pH, although the pK(a) dependencies followed the same pattern. Experimental and modeling results could be brought into good agreement for P. agglomerans if the cell-internal pH was admitted to approximate the external pH instead of implying pH homeostasis for modeling calculations. Thus, besides the actual concentration of sulfonamides, the pH dependent mode of reaction of different bacteria to sulfonamides may additionally govern the population dynamics in soils.