Microbial degradation and impact of Bracken toxin ptaquiloside on microbial communities in soil

The carcinogenic and toxic ptaquiloside (PTA) is a major secondary metabolite in Bracken fern (Pteridium aquilinum (L.) Kuhn) and was hypothesized to influence microbial communities in soil below Bracken stands. Soil and Bracken tissue were sampled at field sites in Denmark (DK) and New Zealand (NZ). PTA contents of 2.1 +/- 0.5 mg g(-1) and 37.0 +/- 8.7 mg g(-1) tissue were measured in Bracken fronds from DK and NZ, respectively. In the two soils the PTA levels were similar (0-5 microg g(-1) soil); a decrease with depth could be discerned in the deeper B and C horizons of the DK soil (weak acid sandy Spodosol), but not in the NZ soil (weak acid loamy Entisol). In the DK soil PTA turnover was predominantly due to microbial degradation (biodegradation); chemical hydrolysis was occurring mainly in the uppermost A horizon where pH was very low (3.4). Microbial activity (basal respiration) and growth ([3H]leucine incorporation assay) increased after PTA exposure, indicating that the Bracken toxin served as a C substrate for the organotrophic microorganisms. On the other hand, there was no apparent impact of PTA on community size as measured by substrate-induced respiration or composition as indicated by community-level physiological profiles. Our results demonstrate that PTA stimulates microbial activity and that microorganisms play a predominant role for rapid PTA degradation in Bracken-impacted soils.     

Degradation of the herbicide dichlobenil and its metabolite BAM in soils and subsurface sediments

The worldwide used herbicide dichlobenil (2,6-dichlorobenzonitrile) has resulted in widespread presence of its metabolite 2,6-dichlorobenzamide (BAM) in surface water and groundwater. To evaluate the potential for natural attenuation of this BAM pollution in groundwater, we studied the degradation of BAM and dichlobenil in 16 samples of clayey till, unconsolidated sand and limestone, including sediments from both oxidized and reduced conditions. The degradation of dichlobenil occurred primarily in the upper few meters below surface, although dichlobenil was strongly sorbed to these sediments. However, the degradation of dichlobenil to BAM could not be correlated to either sorption, water chemistry, composition of soils or sediments. Degradation of dichlobenil to BAM was limited (<2% degraded) in the deeper unsaturated zones, and no degradation was observed in aquifer sediments. This illustrates, that dichlobenil transported to aquifers does not contribute to the BAM-contamination in aquifers. A small, but significant degradation of BAM was observed in the upper part of the unsaturated zones in sandy sediments, but no degradation was observed in the clayey till sediment or in the deeper unsaturated zones. The insignificant degradation of BAM in aquifer systems shows that BAM pollution detected in aquifers will appear for a long time; and consequently the potential for natural attenuation of BAM in aquifer systems is limited.     

Dioxin screening in fish product by pattern recognition of biomarkers

Two alternative, cost- and time-effective dioxin screening methods relying on two categories of potential lipid biomarkers were investigated. A dioxin range varying from 1.1 to 47.1 pg PCDD/F TEQ-WHO/g lipid using 64 fish meal samples was used for model calibration. The methods were based on multivariate models using either (1) fatty acid composition monitored by GC-FID or (2) fluorescence landscape signals analysed using the PARAFAC model and in both cases predicting dioxin content as pgPCDD/F TEQ-WHO/g lipid. In both cases, Partial Least Squares (PLS) regression was performed for predicting the dioxin content of a sample. The GC-FID data analyses was based on automatic peak alignment and integration, enabling extraction of the area of 140 peaks from the gas chromatograms, as opposed to the 31 fatty acids usually considered for fish oil characterisation. In addition to classic PLS employing the whole dataset for calibration, a two-step local PLS modeling approach was performed based upon an initial selection of k number of calibration samples providing the best match to the prediction sample using a so-called k Nearest Neighbors (kNN) approach, then followed by PLS calibration on these kNN selected samples for dioxin prediction. Fluorescence spectroscopy offers a promising non-invasive and ultra-rapid technique, with less than two minutes analysis time. However, fluorescence spectroscopy using the pattern recognition "kNN-PLS" yielded a correlation of 0.76 (r2) and a high root mean square error of prediction of 11.4 pg PCDD/F TEQ-WHO/g lipid. The predictions were improved when the PLS calibration was performed on all the sample with a root mean square error of prediction of 7.0 pg PCDD/F TEQ-WHO/g lipid. Unfortunately, these results failed to demonstrate the potential of fluorophore monitoring as a screening method. In contrast, the overall best screening performance was obtained with the fatty acid profile, when the kNN-PLS combination employed for pattern recognition (kNN) all the areas of the 140 detected peaks and the PLS regression used the areas of 46 selected peaks. This "kNN-PLS" prediction with three latent variables and based upon the 12 nearest neighbors selected out of the 64 x 2 fatty acid profiles (duplicate analyses), yielded a correlation of 0.85 (r2) and a root mean square error of prediction of 2.1 pg PCDD/F TEQ-WHO/g lipid and resulted in a total analysis time of one and half hour per sample.     

Use of (15)N-labelled nitrogen deposition to quantify the source of nitrogen in runoff at a coniferous-forested catchment at Gårdsjön, Sweden

To determine the source of dissolved inorganic nitrogen (N) in runoff, approx. 35kg N enriched with the stable isotope (15)N (2110 per thousand delta(15)N) was added to a mature coniferous forested catchment for one whole year. The total N input was approx. 50kg ha(-1) year(-1). The enrichment study was part of a long-term whole-catchment ammonium nitrate addition experiment at G?rdsj?n, Sweden. The (15)N concentrations in precipitation, throughfall, runoff and upper forest floor were measured prior to, during, and 3-9years following the (15)N addition. During the year of the (15)N addition the delta(15)N level in runoff largely reflected the level in incoming N, indicating that the leached NO(3)(-) came predominantly from precipitation. Only 1.1% of the incoming N was lost during the year of the tracer addition. The cumulative loss of tracer N over a 10-year period was only 3.9% as DIN and 1.1% as DON.     

Risk assessment of linear alkylbenzene sulphonates, LAS, in agricultural soil revisited: robust chronic toxicity tests for Folsomia candida (Collembola), Aporrectodea caliginosa (Oligochaeta) and Enchytraeus crypticus (Enchytraeidae)

To obtain robust data on the toxicity of LAS, tests with the collembolan Folsomia candida L., the oligochaetes Aporrectodea caliginosa Savigny (earthworm) and Enchytraeus crypticus Westheide and Graefe (enchytraeid) were performed in a sandy loam soil. Additionally limited tests with LAS spiked to sewage sludge, and subsequently mixed into soil, were performed. For the endpoint of interest, reproduction in soil, we found an EC10 of 205 mg LAS kg(-1) soil [8.6-401] [95% confidence limits] for F. candida and an EC10 of 46 mg LAS kg(-1) soil [13-80] for A. caliginosa after 28 days. E. crypticus was not affected by concentrations up to 120 mg LAS kg(-1) soil. When adding (low contaminated) non-spiked sludge to soil, high stimulation of reproduction was observed for E. crypticus and A. caliginosa but not for F. candida. We argue that this difference in stimulative response between the tested species is related to the difference in feeding behaviour. Sludge spiked with LAS did not significantly affect the reproduction of F. candida (fertility: number of juvenile offspring) and A. caliginosa (fecundity: number of cocoons) (dose equivalent to 181 g and 91 g LAS kg(-1) sludge, respectively). Significantly reduced reproduction was observed for E. crypticus (at 120 mg LAS kg(-1) soil+sludge corresponding to 72 g LAS kg(-1) sludge) compared to non-spiked sludge. The reproduction by E. crypticus was, however, comparable to the reproduction observed in the control soil without sludge. Compared to LAS directly spiked to soil, the reproductive output of organisms exposed to spiked sludge was either not significantly different (F. candida, E. crypticus) or significantly improved (A. caliginosa). More studies are needed in order to make firm conclusions on the potential effect of artificially contaminated sludge in soil systems.     

Biotic transformation of anticoccidials in soil using a lab-scale bio-reactor as a precursor-tool

Two anticoccidial agents, salinomycin and robenidine, heavily used in the worldwide veterinary meat production, were investigated for their potential biotic degradation by cultured soil bacteria. The degradation-study was performed in lab-scale bio-reactors under aerobic and anaerobic conditions incubated for 200 h with a mixed culture of soil bacteria. Samples were analyzed by LC-MS/MS and potential transformation products were tentatively identified. Salinomycin was degraded under aerobic conditions and traces could be found after 200 h, however, seems more persistent under anaerobic conditions. Four transformation products of salinomycin were discovered. Robenidine was degraded under aerobic and anaerobic conditions, however, traces of robenidine were observed after 200 h. Five biotic transformation products of robenidine were discovered.     

Temperature Dependent Depuration of Norovirus GII and Tulane Virus from Oysters (Crassostrea gigas)

Raw oysters are considered a culinary delicacy but are frequently the culprit in food-borne norovirus (NoV) infections. As commercial depuration procedures are currently unable to efficiently eliminate NoV from oysters, an optimisation of the process should be considered. This study addresses the ability of elevated water temperatures to enhance the elimination of NoV and Tulane virus (TuV) from Pacific oysters (Crassostrea gigas). Both viruses were experimentally bioaccumulated in oysters, which were thereafter depurated at 12 °C and 17 °C for 4 weeks. Infectious TuV and viral RNA were monitored weekly for 28 days by TCID₅₀ and (PMAxx-) RT-qPCR, respectively. TuV RNA was more persistent than NoV and decreased by?<?0.5 log₁₀ after 14 days, while NoV reductions were already?>?1.0 log₁₀ at this time. For RT-qPCR there was no detectable benefit of elevated water temperatures or PMAxx for either virus (p?>?0.05). TuV TCID₅₀ decreased steadily, and reductions were significantly different between the two temperatures (p?<?0.001). This was most evident on days 14 and 21 when reductions at 17 °C were 1.3–1.7 log₁₀ higher than at 12 °C. After 3 weeks, reductions?>?3.0 log₁₀ were observed at 17 °C, while at 12 °C reductions did not exceed 1.9 log₁₀. The length of depuration also had an influence on virus numbers. TuV reductions increased from?<?1.0 log₁₀ after seven days to?>?4.0 log₁₀ after 4 weeks. This implies that an extension of the depuration period to more than seven days, possibly in combination with elevated water temperatures, may be beneficial for the inactivation and removal of viral pathogens.

     

Crushed concrete as a phosphate binding material: a potential new management tool

To avoid eutrophication of receiving waters, effective methods to remove P in urban and agricultural runoff are needed. Crushed concrete may be an effective filter material to remove dissolved and particulate P. Five types of crushed concrete were tested in the laboratory to evaluate the retention capacity of dissolved P. All types removed P very effectively (5.1-19.6 g P kg(-1) concrete), while the possible release of bound P varied between 0.4 and 4.6%. The retention rate was positively related to a decreasing concrete grain size due to an increasing surface area for binding. The P retention was also related to a marked increase in pH (up to pH 12), and the highest retention was observed when pH was high. Under these circumstances, column experiments showed outlet P concentrations <0.0075 mg P L(-1). Furthermore, experiments revealed that release of heavy metals is of no importance for the treated water. We demonstrate that crushed concrete can be an effective tool to remove P in urban and agricultural runoff as filter material in sedimentation/infiltration ponds provided that pH in the treated water is neutralized or the water is diluted before outlet to avoid undesired effects caused by the high pH.     

Pesticide cocktails can interact synergistically on aquatic crustaceans

Background, aim and scope  

The ergosterol biosynthesis-inhibiting (EBI) fungicide prochloraz can enhance the effect of other pesticides in a range of animal species. Approximately 50% of the fungicides used in Denmark are EBI fungicides. Hence, if they all have synergising potential, a risk assessment of pesticide mixtures based on additivity might not suffice. This study investigates the synergising potential of six different EBI fungicides representing the imidazoles (prochloraz), the triazoles (epoxiconazole, propiconazole and tebuconazole), the piperidines (fenpropidin) and the morpholines (fenpropimorph) together with the pyrethroid insecticide alpha-cypermethrin.