The production and characterization of lipopeptide biosurfactant obtained from a novel bacterial strain Bacillus amyloliquefaciens C11 isolated from a biopurification system, to enhance the solubility of three pesticides of environmental concern was investigated. Biosurfactant production by B. amyloliquefaciens C11 was evaluated in a 2-L reactor and characterized by chromatographic and spectroscopic methods. Biosurfactant production was associated with bacterial growth and glucose consumption. The produced biosurfactant decreased the surface tension of water from 72 to 28 mN m-1 at 24 h of incubation, with critical micelle concentration (CMC) of 51.5 mg L-1. The polymerase chain reaction for determining the presence of srfAA gene in B. amyloliquefaciens C11 was carried out. The strain exhibited the presence of srfAA gene with amplification at 201 bp, which is specific to surfactin homologues. The production of surfactin was corroborated by high performance liquid chromatography (HPLC) and matrix-assisted laser desorption/ionization time-of flight mass spectrometry (MALDI-TOF-MS) analyses. The HPLC analysis showed six isoforms of surfactin, being the isoform D found in mayor percentage (41%). Thermal gravimetric analysis (TGA) revealed the thermostability of the biosurfactant. The obtained biosurfactant maintained its properties during exposure to temperatures in range of 30-80 degrees C and pH values in range of 5-9. The surfactin produced by B. amyloliquefaciens C11 increased the solubility in water of chlorpyrifos, iprodione and atrazine by 7.5-fold, 1.3-fold, and 1.4-fold, respectively. Our results show that the biosurfactant produced by B. amyloliquefaciens C11 improves the bioavailability of pesticides and consequently could improves the efficiency of bioremediation processes.

In this study, we selected and characterized different pesticide-tolerant bacteria isolated from a biomixture of a biopurification system that had received continuous applications of a pesticides mixture. The amplicon analysis of biomixture reported that the phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were predominant. Six strains grew in the presence of chlorpyrifos and iprodione. Biochemical characterization showed that all isolates were positive for esterase, acid phosphatase, among others, and they were identified asPseudomonas,RhodococcusandAchromobacterbased on molecular and proteomic analysis. Bacterial growth decreased as both pesticide concentrations increased from 10 to 100 mg L(-1)in liquid culture. TheAchromobactersp. strain C1 showed the best chlorpyrifos removal rate of 0.072-0.147 d(-1)a half-life of 4.7-9.7 d and a maximum metabolite concentration of 2.10 mg L(-1)at 120 h. On the other hand,Pseudomonassp. strain C9 showed the highest iprodione removal rate of 0.100-0.193 d(-1)a half-life of 4-7 d and maximum metabolite concentration of 0.95 mg L(-1)at 48 h. TheAchromobacterandPseudomonasstrains showed a good potential as chlorpyrifos and iprodione-degrading bacteria.

Mixing characteristics of an aerated coaxial mixer composed of an anchor and a central impeller was investigated using the non-invasive flow visualization technique called electrical resistance tomography (ERT). Corn syrup solutions with different viscosity were used as the viscous Newtonian fluids. Two coaxial configurations were considered: the anchor − PBD (a pitched blade downward pumping impeller) and the anchor − PBU (a pitched blade upward pumping impeller). In this study, the effects of central impeller types, speed ratios (central impeller speed/anchor speed), rotation modes, gas flow rates, and viscosity on the mixing time and power uptake were explored. It was found that in the presence of gas, the PBU-anchor coaxial combination in co-rotating mode exhibited shorter mixing times and lower power consumption than the PBD-anchor. Experiments demonstrated that the effect of aeration on the mixing time was a function of hydrodynamic regimes occurring in the tank. Using the response surface method, an effort was made to develop a quadratic model as a function of central impeller speed, anchor speed, gas flow rate, and viscosity for predicting the mixing time. Three-dimensional response surfaces were plotted to understand the main and interaction effects of these factors.

Intensive use of pesticides applied simultaneously in field to improve the effectiveness of pest control increase the environmental contamination, affecting the soil and water quality. Some of the commonly used pesticides are the insecticide chlorpyrifos and the fungicide iprodione; being thus critically essential to develop bioremediation methods to remove these contaminants by tolerant-bacteria. In this study we selected and characterized different pesticides-tolerant bacteria isolated from a biomixture of a biopurification system that had received continuous applications of a mixture of the pesticides chlorpyrifos and iprodione. Out of the 10 isolated bacterial colonies, only six strains presented adequate growth in presence of the both pesticides at 100 mg L−1. Biochemical and enzymatic characterization using API ZYM showed that all isolates (100%) were positive for esterase, leucine aminopeptidase, acid phosphatase, and naphthol-AS-BI-phosphohydrolase. According to the molecular level study of the 16S ribosomal gene and MALDI TOF/TOF MS, it was possible to determine that the isolated bacteria belong to the genera Pseudomonas , Rhodococcus and Achromobacter . Bacterial growth decreased proportionally (R2 > 0.96) as been as both pesticide concentrations increased from 10 to 100 mg L−1. Achromobacter sp. strain C1 showed the best chlorpyrifos removal (between 56–29%) after 120 h of incubation. On the other hand, the highest iprodione removal (between 91.2–98.9%) was observed for the Pseudomonas sp. strain C9, which was not detected after 48 h of incubation. According with their identification and ability to remove the contaminants, Achromobacter sp. strain C1 and Pseudomonas sp. strain C9 appear as promising microorganisms for their use in the treatment of matrices contaminated with chlorpyrifos, iprodione or their mixture. The results of this study will help to improve current technologies for the biodegradation of this commonly used insecticide and fungicide, in order to give a response to the problem of contamination by pesticides.

The dissipation of atrazine, chlorpyrifos and iprodione in a biopurification system and changes in the microbial and some biological parameters influenced by the rhizosphere of Lolium perenne were studied in a column system packed with an organic biomixture. Three column depths were analyzed for residual pesticides, peroxidase, fluorescein diacetate activity and microbial communities. Fungal colonization was analyzed by confocal laser scanning microscopy to assess the extent of its proliferation in wheat straw. The L. perenne rhizosphere enhanced pesticide dissipation and negligible pesticide residues were detected at 20–30 cm column depth. Atrazine, chlorpyrifos and iprodione removal was 82, 89 and 74% respectively in the first 10 cm depth for columns with vegetal cover. The presence of L. perenne in contaminated columns stimulated peroxidase activity in all three column depth sections. Fluorescein diacetate activity decreased over time in all column sections with the highest values in biomixtures with vegetal cover. Microbial communities, analyzed by PCR-DGGE, were not affected by the pesticide mixture application, presenting high values of similarity (>65%) with and without vegetal cover. Microbial abundance of Actinobacteria varied according to treatment and no clear link was observed. However, bacterial abundance increased over time and was similar with and without vegetal cover. On the other hand, fungal abundance decreased in all sections of columns after 40 days, but an increase was observed in response to pesticide application. Fungal colonization and straw degradation during pesticide dissipation were verified by monitoring the lignin autofluorescence loss.

A biopurification system based on the adsorption and degradation capacity of a biomixture to degrade a mixture of pesticides (atrazine, chlorpyrifos, iprodione; 50 mg kg−1 each) in repeated applications (0, 30, and 60 days) was evaluated. Tanks of 1 m3 packed with a biomixture (ρ 0.29 g mL−1) with and without vegetal cover were used. The biomixture contained soil, peat, and wheat straw in a proportion 1:1:2 by volume, respectively. Pesticide concentrations, biological activities (urease, phenoloxidase, and dehydrogenase), and microbial community changes (DGGE and qPCR) were evaluated periodically. Pesticide dissipation was higher in tanks with vegetal cover (> 95%) and no variation was observed after the three applications; contrarily, pesticide dissipation decreased in the tank without vegetal cover after each application. The presence of vegetal cover decreased the half-life of pesticides by at least twice. Biological activities were in general not affected by the application and reapplication of pesticides in the same treatment; however, they exhibited some differences between tanks containing and lacking the vegetal cover. High similarity between microbial groups (actinobacteria, bacteria, and fungi) was observed, suggesting no influence ascribable to the successive pesticide applications. The number of copies of bacteria and actinobacteria remained almost constant during the assay. However, the number of copies of fungi was significantly higher in the uncontaminated tank without vegetal cover.

The use of biopurification systems can mitigate the effects of pesticide contamination on farms. The primary aim of this study was to evaluate the effect of pesticide dissipation on microbial communities in a pilot biopurification system. The pesticide dissipation of atrazine, chlorpyrifos and iprodione (35 mg kg(-1) active ingredient [a.i.]) and biological activity were determined for 40 days. The microbial communities (bacteria, actinomycetes and fungi) were analyzed using denaturing gradient gel electrophoresis (DGGE). In general, pesticide dissipation was the highest by day 5 and reached 95%. The pesticides did not affect biological activity during the experiment. The structure of the actinomycete and bacterial communities in the rhizosphere was more stable during the evaluation than that in the communities in the control without pesticides. The rhizosphere fungal communities, detected using DGGE, showed small and transitory shifts with time. To conclude, rhizosphere microbial communities were not affected during pesticide dissipation in a pilot biopurification system.

A leaching experiment was conducted to determine the influence of four successive applications of pulp mill sludge on some parameters of an Andisol. Undisturbed soil columns were treated with pulp mill sludge (0 to 30 Mg ha(-1)) every three months during one year with a hydraulic regime of 1200 mm per year. Leachates of each treatment were analyzed periodically and, at the end of the period, columns were fractionated at three depths (0-20, 20-40 and 40-60 cm) and soil chemical parameters were analyzed. Sludge added successively to Andisol increased the nitrate concentration in leachates. After the fourth application of 30 Mg ha(-1) sludge, nitrate leaching was about 1.7 times higher than in the control column, however, this level is still lower than the limit under Chilean regulations. Low ammonium concentrations were observed in leachates as a result of nitrification processes and retention by clay and organic matter in the Andisol. In fractionated soil columns, pH, organic matter, total nitrogen and phosphorus increased as the sludge rate increased, with the highest values found in the upper part of the columns. The concentration of nitrate and ammonium in soil columns followed an inverse pattern: while ammonium concentration was the highest at 0 to 20 cm, nitrate concentration was the lowest in that fraction; sludge addition caused a linear increase in ammonium and nitrate content at the three depths analyzed.

Biochar is a source of carbon with physico-chemical and biological properties that allow it to promote microbial growth, to absorb moisture and to improve the adsorption and/or degradation of pesticides. We evaluated the effect of biochar as a partial replacement of commercial peat in the pesticide-degrading biomixtures of a biopurification system known as biobed. Each biomixture was prepared with one type of soil (clay, trumao and sandy), straw, peat and biochar in different volumetric proportions. In each biomixture, the residual pesticide (atrazine, carbendazim, chlorpyrifos, isoproturon, iprodione and diazinon) concentration, the pH, and the levels of organic carbon (OC) and total Kjeldahl nitrogen (TKN) were measured at the beginning (day 0) and at the end (day 40) of the pesticide degradation assay. The obtained results demonstrated that at day 0, the pH of the biomixtures, regardless of soil type, increased incrementally with increasing amounts of biochar, whereas the OC and TKN values remain constant. At the end of the pesticide degradation assay, changes were observed in the biomixtures that demonstrated differences among their pesticide degradation abilities. In general, pesticide degradation was higher in the control biomixtures (without biochar) than in biomixtures prepared with biochar. An exception was the pesticide iprodione, which presented a highest degradation efficicency when biochar was included in the biomixture. Although the use of biochar as a replacement of peat in the biomixtures did not significantly improve pesticide degradation, a decrease in the initial residual concentration of the pesticides was observed. Therefore, biochar may represent an interesting material to replace peat in biomixtures designed to degrade and/or adsorb pesticides.

The effect of pulp mill sludge addition (10–30Mg/ha) to soil derived from volcanic ash (Andisol) on soil characteristics, microbial community and Lolium perenne L. cv quartet. biomass production was evaluated in field assays. Soil without sludge was used as a control treatment. The sludge addition improved the chemical properties of the soil. Organic matter and phosphorous content increased in the soil with increasing amounts of sludge, obtaining 35% more organic matter content with the application of 30Mg/ha than the control soil. The phosphorous was accumulated into the soil after the end of cultivation improving the phosphorous pool in the soil. When 30Mg/ha sludge was added to the soil, a biomass of Lolium perenne, was 60% more than the control soil at the end of the experiment. The analysis of soil microbial community showed that the application of sludge did not modify greatly the microbial community of fungi and bacteria even when high doses were applied.

Quantitative information on cropland phosphorus (P) flows at the township scale is critical for developing sustainable P management measures under the smallholder farming system. This study addressed changes in cropland soil surface P budgets (i.e., net of P inputs and crop outputs), use efficiencies (i.e., the ratio between crop P uptake and total P input) and legacy P pools across 21 townships in the Yongan watershed of eastern China in 1980–2010. For the entire watershed, total P input (>98% from synthetic fertilizer and farmyard manure), crop uptake and budgets per cropland area increased from 50.4, 17.3 and 33.1 kg P ha−1 yr−1 in 1980 to 74.6, 20.5 and 55.1 kg P ha−1 yr−1 in 1995, and then sharply declined to 39.6, 11.4 and 28.2 kg P ha−1 yr−1 in 2010, respectively. Estimated P use efficiency decreased from 34% in 1980 to 26% in 1999 before slightly increasing to 28% in 2010. Although the 21 townships had similar temporal variations over the 1980–2010 period, P budgets and use efficiency showed 2–3-fold spatial variability among townships within a given year. Spatio-temporal variations in the P budget and use efficiency were mainly related to changes in P fertilization rates and patterns (i.e., ratio of applied synthetic fertilizer P and farmyard manure P) and cropland types. The 20 townships having soil data had 87–720% and 113–395% increases of Olsen-P and total P contents in the upper 20 cm of cropland soils between 1984 and 2009, respectively. Increased soil TP level between 1984 and 2009 suggested that more than 53–79% of the cumulative P budget accumulated as legacy P pools in cropland soils. Based on regression analyses, legacy soil P contribution to annual crop P uptake was estimated to increase from 0.47 kg P ha−1 yr−1 (3%) in 1980 to 3.45 kg P ha−1 yr−1 (31%) in 2010, with 52–80% from synthetic fertilizer and 2–46% from farmyard manure. Improved utilization of soil legacy P pools for crop production and increasing P use efficiency are necessary to minimize P inputs and reduce nonpoint source P pollution load. The high spatial heterogeneity in P budgets and use efficiencies across townships, as well as considerable legacy soil P pools after long-term over-application, should be considered in developing P management strategies under smallholder farm systems.

The white-rot fungus Anthracophyllum discolor immobilized on wheat grains was evaluated for chlorophenol (2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) degradation in allophanic soil columns activated by acidification. Columns without inoculation were used as the control to evaluate the adsorption capacity of the soil columns. The chlorophenols were removed efficiently in soil columns by both adsorption and degradation processes. In inoculated soil columns, 2,4-dichlorophenol was highly degraded and this degradation is associated with a high production of manganese peroxidase. 2,4,6-trichlorophenol was degraded to a lesser extent compared with 2,4-dichlorophenol. Pentachlorophenol was first removed by adsorption and then through degradation by the fungus. Manganese peroxidase activity was lowest when the column was fed with pentachlorophenol and highest when the column was fed with 2,4-dichlorophenol. Laccase was also produced by the fungus but to a lesser degree.

We studied the phosphorous (P) and molybdenum (Mo) relationship in soil and red clover (Trifolium pratense L.) in a non limed and limed acid Andisol of Southern Chile. In soil, we evaluated the effect of different liming (0 and 2000 mg kg(-1)), P (0, 200 and 400 mg kg(-1)), and Mo (0, 0.58 and 0.96 mg kg(-1)) doses supply on soil available Mo. In addition, the availability of P and Calcium (Ca) in treated soils was determinated. In red clover, we studied the Mo and P shoot concentrations and dry matter yield in response to the different treatments applied to the soil. Also, we measured the changes produced by Mo uptake in shoot Cu concentrations. The results showed that both, lime and more strongly P and Mo additions significantly (P <= 0.05) increased soil Mo availability. In contrast, soil available P was not significantly (P <= 0.05) affected by liming and Mo treatments. A significant high correlation (r = 0.579, at P <= 0.05) was observed among soil Mo availability and shoot Mo concentrations, as well as between soil available P and shoot concentration of P (r = 0.844, at P <= 0.01). In this study for all fertilization treatments, shoot Cu concentrations reached values which are considered as normal for forage species. We also shown that the simultaneous applications of high P and Mo rates could be produce red clover shoot Cu/Mo ratios that should provoke Mo-induced Cu deficiency (Molybdenosis) for the cattle. Red clover yield was no significantly different in limed and non limed soils. Nevertheless, red clover yield production increased at increasing rates of P and Mo in both, non limed and limed soil. The major practical implication of these results is that the application of Mo doses equal or superior to 200 g ha(-1) to acid Andisols, are recommendable to obtain appropriate Mo shoot content on red clover. In addition, our results shown that P supply to these soils, rather than liming, is necessary to obtain sufficient values of shoot Mo concentrations in red clover.

Sludge from kraft mill wastewater treatment was applied on two soils derived from volcanic ashes and, the effect on biological parameters of the soils was evaluated. The soils used in this study were an Andisol belonging of Gorbea Series and an Ultisol belonging of Collipulli Series. The sludge was added at rates of 0, 10, 20, 30 and 50 t ha(-1). Previously, germination of red clover (Trifolium pratense), white clover (Trifolium repens), alfalfa (Medicago sativa) and ryegrass (Lolium perenne) was tested to assess phytotoxicity of the sludge. The different soil-sludge mixtures were incubated at controlled temperature for 60 days and microbial respiration, microbial biomass carbon, fluorescein diacetate hydrolysis and acid phosphatase activity were evaluated throughout the incubation time. All biological parameters evaluated were sensitive enough to shown the effect of sewage sludge application on soil microorganisms. The sludge application at different rates increased significantly (P<0.05) the microbial activity and enzymatic activity of the sludge amended soils. The maximum levels of activity were observed between 15 and 30 days after sludge application in both Gorbea soil and Collipulli soil, obtaining the highest values when were applied between 30 and 50 t ha(-1). The results of this study suggest that sludge from kraft mill wastewater treatment may have potential as a beneficial soil amendment for improving biological properties of the soils.