1.Biodegradation of a commercial mixture of the herbicides atrazine and S-metolachlor in a multi-channel packed biofilm reactor.
Cabrera-Orozco A1, Galíndez-Nájera SP2, Ruiz-Ordaz N3, Galíndez-Mayer J4, Martínez-Jerónimo FF1. Environ Sci Pollut Res Int. 2016 Feb 20. [Epub ahead of print]
Atrazine and S-metolachlor are two of the most widely used herbicides for agricultural purposes; consequently, residues of both compounds and their metabolites had been detected in ground and superficial waters. Unlike atrazine, the complete degradation of metolachlor has not been achieved. Hence, the purpose of this research is to study the biodegradation of a commercial mixture of atrazine and S-metolachlor in a prototype of a multi-channel packed-bed-biofilm reactor (MC-PBR) designed with the aim of solving the problems of pressure drop and oxygen transfer, typically found on this type of bioreactors.Because the removal efficiency of the herbicides was increased when Candida tropicalis was added to the original microbial community isolated, the reactor was inoculated with this enriched community. The operational conditions tested in batch and continuous mode did not affect the removal efficiency of atrazine; however, this was not the case for S-metolachlor.
2.New method for the determination of metolachlor and buprofezin in natural water using orthophthalaldehyde by thermochemically-induced fluorescence derivatization (TIFD).
Mendy A1, Thiaré DD2, Sambou S1, Khonté A1, Coly A3, Gaye-Seye MD1, Delattre F4, Tine A1. Talanta. 2016 May 1;151:202-8. doi: 10.1016/j.talanta.2016.01.036. Epub 2016 Jan 18.
Herbicide metolachlor (MET) and insecticide buprofezin (BUP) were determined in natural waters by means of a newly-developed, simple and sensitive thermochemically-induced fluorescence derivatization (TIFD) method. The TIFD approach is based on the thermolysis transformation of naturally non-fluorescent pesticides into fluorescent complex O-phthalaldehyde-thermoproduct(s) in water at 70°C for MET and at 80°C for BUP. The TIFD method was optimized with respect to the temperature, pH, complex formation kinetic and pesticides concentrations. The limit of detection (LOD=0.8ngmL(-1) for MET and 3.0ngmL(-1) for BUP) and quantification (LOQ=2.6ngmL(-1) for MET and 9.5 ngmL(-1) for BUP) values were low, and the relative standard deviation (RSD) values were small (between 1.2% and 1.8%), which indicates a good analytical sensitivity and a great repeatability of TIFD method. Recovery studies were performed on spiked well, sea and draining waters samples collected in the Niayes area by using the solid phase extraction (SPE) procedure.
3.Metolachlor Sorption and Degradation in Soil Amended with Fresh and Aged Biochars.
Trigo C, Spokas K, Hall K, Cox L, Koskinen WC. J Agric Food Chem. 2016 Apr 6. [Epub ahead of print]
Addition of organic amendments such as biochar to soils can influence pesticide sorption-desorption processes, and in turn, pesticide availability and biodegradation. Availability is affected by both the physical and chemical properties of soils and pesticides, as well as soil-pesticide contact time, or aging. Changes in sorption/availability of metolachlor with aging in soil amended with three macademia nut shells biochars aged zero (BCmac-fr), 1 year (BCmac-1yr) and 2 years (BCmac-2yr) and two wood biochars aged zero (BCwood-fr) and 5 years (BCwood-5yr) was determined. Sorption coefficient (Kd) values increased with incubation time to a greater extent in amended soil as compared to unamended soils; Kd increased by 1.2X for the unamended soil, 2.0X for BCwood-fr, 1.4X for BCwood-5yr, 2.4X for BCmac-fr, 2.5X for BCmac-1yr, and 1.9X for BCmac-4yr. This increase was the result of a 15% decrease in the metolachlor extractable with CaCl2 solution with incubation time in soil as compared to a 50% decrease in amended soil.
4.Effect of sugarcane cropping systems on herbicide losses in surface runoff.
Nachimuthu G1, Halpin NV2, Bell MJ3. Sci Total Environ. 2016 Apr 2;557-558:773-784. doi: 10.1016/j.scitotenv.2016.03.105. [Epub ahead of print]
Herbicide runoff from cropping fields has been identified as a threat to the Great Barrier Reef ecosystem. A field investigation was carried out to monitor the changes in runoff water quality resulting from four different sugarcane cropping systems that included different herbicides and contrasting tillage and trash management practices. These include (i) Conventional - Tillage (beds and inter-rows) with residual herbicides used; (ii) Improved - only the beds were tilled (zonal) with reduced residual herbicides used; (iii) Aspirational - minimum tillage (one pass of a single tine ripper before planting) with trash mulch, no residual herbicides and a legume intercrop after cane establishment; and (iv) New Farming System (NFS) - minimum tillage as in Aspirational practice with a grain legume rotation and a combination of residual and knockdown herbicides. Results suggest soil and trash management had a larger effect on the herbicide losses in runoff than the physico-chemical properties of herbicides.