Sulfonamides are the second most used antibiotic class in veterinary medicine and applied to livestock to treat bacterial infections. Subsequently, they are spread onto agricultural soils together with the contaminated manure used as fertilizer. Both manure and antibiotics affect the soil microbial community. However, the influence of different liquid manure loads on effects of antibiotics to soil microorganisms is not well understood. Therefore, we performed a microcosm experiment for up to 32 d to clarify whether the function and structure of the soil microbial community is differently affected by interactions of manure and the antibiotic sulfadiazine (SDZ). To this end selected concentrations of pig liquid manure (0, 20, 40, 80 g kg–1) and SDZ (0, 10, 100 mg kg–1) were combined. We hypothesized that incremental manure amendment might reduce the effect of SDZ in soils, due to an increasing sorption capacity of SDZ to organic compounds. Clear dose‐dependent effects of SDZ on microbial biomass and PLFA pattern were determined, and SDZ effects interacted with the liquid manure application rate. Soil microbial biomass increased with incremental liquid manure addition, whereas this effect was absent in the presence of additional SDZ. However, activities of enzymes such as urease and protease were only slightly affected and basal respiration was not affected by SDZ application, while differences mostly depended on the concentration of liquid manure. These results illustrated that the microbial biomass and structural composition react more sensitive to SDZ contamination than functional processes. Furthermore, effects disproportionally increased with incremental liquid manure addition, although extractable amounts of SDZ declined with increasing liquid manure application.
This article deals with the following two questions. Are acoustic measurements in running waters appropriate for a highly resolved investigation of the bedload transport? Which characterizations of the bedload regarding mass and shape are possible via the acoustic signals? The signals were recorded by means of data recorders (Tascam Inc. DAP1 Portable Data Recorder) and hydrophones (International Transducer Corp. ITC-4001 A). The ITC-4001 is a shallow water omnidirectional transducer containing a flexural disc transducer utilizing Channelite-5400 ceramics mounted in a rugged corrosion-resistant housing. These hydrophones were screwed onto the bottom side of stainless steel plates, serving as a contact surface for the bedload in motion above them. After more than 100 series of tests in the laboratory, which indicated the basic relations between the dimension, shape and weight of the bedload and the resulting signal, field tests of the measuring system were conducted. By artificially produced flood waves in the small brooks Riverisbach, Olewiger Bach and by a winter flood wave in the River Moselle, it is possible to elaborate similar structures of the signal course of the bedload movement. The highest transport rates can be observed at the beginning of the increasing limbs and behind the peaks of the waves. At the beginning of the waves, the increasing transport power of the water and the loose material can be considered as the cause for this result. The high stream velocity behind the wave peaks explains the increase in the bedload transport so that material from the channel beds is unfastened and will be mobilized. The characterization of the bedload regarding the shape and mass is still limited regarding the field measurements and could be solved only for homogeneous grain sizes and single stones under laboratory conditions.
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