Atrazine degradation patterns: the role of straw cover and herbicide application history

In Brazil, atrazine (ATZ) is widely applied to maize (Zea mays L.) fields for weed control. The presence of ATZ and its metabolites in soil and water matrices has become a matter of some concern for governmental authorities as well as for society at large. This study evaluated the patterns of ATZ degradation (mineralization, extractable and non-extractable ATZ residues, and metabolite formation) in a Brazilian Typic Paleudult. Soil samples from a cultivated area under a no-tillage system with a history of ATZ application were incubated with 14C-ATZ in both the presence and absence of straw cover on the soil surface, and the evolved 14CO2 was determined by liquid scintillation. Samples from an area with native vegetation, adjacent to the cultivated area, were also incubated as a control. A higher mineralization of ATZ was observed in the cultivated soil (> 85 %) in comparison with the native soil (10 %) after 85 days of incubation. In addition to the higher mineralization and hydroxyatrazine (HA) formation, a rapid decrease in the water-extractable residues was observed in the cultivated soil. When the cultivated soil was covered with straw, mineralization was reduced by up to 30 % although a small amount of remobilization to the soil occurred within the 85 days. Straw cover hindered the degradation of ATZ in cultivated soils; whereas an accelerated biodegradation was due to repeated applications of ATZ, which may have selected microbiota more skilled at biodegrading the herbicide

Comparison of Glyphosate degradation in a floodplain and an agricultural soil

Floodplain soils are often exposed to pesticides but are seldom recognized as a subject to environmental fate studies. We incubated a floodplain and an agricultural soil with 14C-position-specific labeled Glyphosate at different soil moisture contents. Our study confirms the potential of Glyphosate degradation in a floodplain soil. However, the agricultural soil, with a continuous history of Glyphosate use, was able to mineralize Glyphosate 3 times faster compared to the floodplain soil. Consequently, the mineralization kinetics of the pesticide differed significantly between the two soil types, with a half-life of 100 days for the agricultural soi

A novel isolated Terrabacter-like bacterium can mineralize2-aminopyrimidine, the principal metabolite of microbialsulfadiazine degradation

Recently we showed that during thedegradation of sulfadiazine (SDZ) by Microbacteriumlacus strain SDZm4 the principal metabolite2-aminopyrimidine (2-AP) accumulated to the samemolar amount in the culture as SDZ disappeared(Tappe et al. Appl Environ Microbiol 79:2572–2577,2013). Although 2-AP is considered a recalcitrantagent, long-term lysimeter experiments with 14Cpyrimidinelabeled SDZ ([14C]pyrSDZ) provided indicationsfor substantial degradation of the pyrimidinemoiety of the SDZ molecule. Therefore, we aimed toenrich 2-AP degrading bacteria and isolated a pureculture of a Terrabacter-like bacterium, denoted strain2APm3. When provided with 14C-labeled SDZ, M.lacus strain SDZm4 degraded [14C]pyrSDZ to [14C]2-AP. Resting cells of 2APm3 at a concentration of5 9 106 cells ml-1 degraded 62 lM [14C]2-AP tobelow the detection limit (0.6 lM) within 5 days.Disappearance of 2-AP resulted in the production of atleast two transformation products (M1 and M2) withM2 being identified as 2-amino-4-hydroxypyrimidine.After 36 days, the transformation products disappearedand 83 % of the applied [14C]2-AP radioactivitywas trapped as 14CO2. From this we concludethat a consortium of two species should be able toalmost completely degrade SDZ in soils

Characterization of Bioactive Phenolic Compounds in Seeds of Chilean Quinoa (Chenopodium quinoa Willd.) Germplasm

In recent years, quinoa (Chenopodium quinoa Willd.), an ancient Andean region crop, has received increased research attention because it is an excellent source of nutrients and also of bioactive phenolic compounds, which are potentially beneficial for human health. However, variation in the content and type of these metabolites in quinoa genetic resources remains, to a large extent, unexplored. We evaluated the composition of free and bound phenolic forms in the seeds of 111 Chilean quinoa accessions by using LC-DAD-MS/MS. The relative phenolic content ranged from 35.51 mg/100 g to 93.23 mg/100 g of seed dry weight. The free phenolic fraction accounted for 72% of the total phenolic content, while the bound fraction represented the remaining 28% of the total phenolic content. Our study also revealed a significant degree of variation in terms of individual phenolic compounds such as rutin, vanillic acid, quercetin, and their derivatives, which can have important implications for quinoa’s nutritional and functional properties. We conclude that our data reveal a significant phenotypic variation of bioactive phenolic content in the examined germplasm, which could be exploited in current and future genetic improvement programs in quinoa

Breakthrough dynamics of s-metolachlor metabolites in drinking water wells: Transport pathways and time to trend reversal

We present the results of a two years study on the contamination of the Luxembourg Sandstone aquifer by metolachlor-ESA and metolachlor-OXA, two major transformation products of s-metolachlor. The aim of the study was twofold: (i) assess whether elevated concentrations of both transformation products (up to 1000 ng/l) were due to fast flow breakthough events of short duration or the signs of a contamination of the entire aquifer and (ii) estimate the time to trend reversal once the parent compound was withdrawn from the market. These two questions were addressed by a combined use of groundwater monitoring, laboratory experiments and numerical simulations of the fate of the degradation products in the subsurface.Twelve springs were sampled weekly over an eighteen month period, and the degradation rates of both the parent compound and its transformation products were measured on a representative soil in the laboratory using a radiolabeled precursor. Modelling with the numeric code PEARL simulating pesticide fate in soil coupled to a simple transfer function model for the aquifer compartment, and calibrated from the field and laboratory data, predicts a significant damping by the aquifer of the peaks of concentration of both metolachlor-ESA and –OXA leached from the soil. The slow response time of the aquifer also imparts a waiting time of years until the return of concentrations below the legal limit of potability. The time to trend reversal following the ban of s-metolachlor in spring protection zones should be observed before the end of the decade, while the return of contaminant concentrations below the drinking water limit of 100 ng/l however is expected to last up to twelve years. The calculated contribution to total water discharge of the fast-flow component from cropland and short-circuiting the aquifer was small in most springs (median of 1.2%), but sufficient to cause additional peaks of concentration of several hundred nanograms per litre in spring water. These peaks are superimposed on the more steady contamination sustained by the baseflow, and should cease immediately once application of the parent compound stops

Atrazine degradation patterns: the role of straw cover and herbicide application history

In Brazil, atrazine (ATZ) is widely applied to maize (Zea mays L.) fields for weed control. The presence of ATZ and its metabolites in soil and water matrices has become a matter of some concern for governmental authorities as well as for society at large. This study evaluated the patterns of ATZ degradation (mineralization, extractable and non-extractable ATZ residues, and metabolite formation) in a Brazilian Typic Paleudult. Soil samples from a cultivated area under a no-tillage system with a history of ATZ application were incubated with 14C-ATZ in both the presence and absence of straw cover on the soil surface, and the evolved 14CO2 was determined by liquid scintillation. Samples from an area with native vegetation, adjacent to the cultivated area, were also incubated as a control. A higher mineralization of ATZ was observed in the cultivated soil (> 85 %) in comparison with the native soil (10 %) after 85 days of incubation. In addition to the higher mineralization and hydroxyatrazine (HA) formation, a rapid decrease in the water-extractable residues was observed in the cultivated soil. When the cultivated soil was covered with straw, mineralization was reduced by up to 30 % although a small amount of remobilization to the soil occurred within the 85 days. Straw cover hindered the degradation of ATZ in cultivated soils; whereas an accelerated biodegradation was due to repeated applications of ATZ, which may have selected microbiota more skilled at biodegrading the herbicide