Evaluation of Sampling Strategies for Pesticides in a Macroporous Sandy Loam Soil

It is not straightforward to sample and demonstrate the presence and transport of pesticides in heterogeneous soil. Following leaching experiments with four differently structured 50-cm-long soil columns (tilled and untilled soil), the objective of this study was to investigate the extent that visual tracing of the dye Brilliant Blue could support in soil sampling for two strongly sorbing pesticides (¹⁴C-labeled glyphosate and pendimethalin). About 830 samples were collected. No pesticide was found below 10– 25 cm depth by random sampling, even though 0.21–0.31% of the applied amounts were leached, and 0.18% of the soil volume was sampled. With similar sampling efforts, the pesticides could generally be traced throughout the columns by sampling from stained soil volumes, only. None of the two particular sampling strategies for pesticides produced accurate mass balances or balances that were obviously better than the other. No pesticide was detected outside stained soil volumes, except for glyphosate in one sample. Below 30 cm, stained soil comprized on average 5% of the total soil volume, leaving 95% as expectedly pesticide-free. The results suggest that much more efficient sampling for sorbing pesticides can be obtained by using the dye and focusing on stained soil volumes.     

Immobilization of penicillin G acylase on macro-mesoporous silica spheres

In this study, macro-mesoporous silica spheres were prepared with a micro-device and used as the support for the immobilization of penicillin G acylase (PGA). To measure the enzymatic activity, the silica spheres with immobilized PGA were placed into a packed-bed reactor, in which the hydrolysis of penicillin G was carried out. The influences of the residence time, the initial concentration of the substrate, the accumulation of the target product 6-aminopenicillanic acid, and the enzyme loading amount on the performance of the immobilized PGA were investigated. The introduction of macropores increased the enzyme loading amount and decreased the internal mass transfer resistance, and the results showed that the enzyme loading amount reached 895 mg/g (dry support), and the apparent enzymatic activity achieved up to 1033 U/g (dry support). In addition, the immobilized PGA was found to have great stability.