## 4 Discussion
This suggested that estrone remained available to microorganisms for the entire period more than it did in fluvisol, so the question was why the enzymatic activity was lower than that in fluvisol? A possible reason could be the nutrients availability in the two soils, Table 1 showing that cambisol had lower nutrient concentrations than fluvisol; therefore, the microbial communities were probably not able to grow much. Although not clearly visible in the data, the 24 h-3 days transition was supposed to have occured; nevertheless, as the macropores (sand) would have eventually filled up and sorption would have moved to smaller pores (loam), an increase in enzymatic activity was recorded for this period (from 272 U to 314 U by day 3). Cambisol was, in general, different from fluvisol, but very similar to chernozem. Chernozem did not show any reliable pattern of biodegradation (rho = 0.14). It presented the general estrone transition after 24 h, but Figure 1 shows this soil had three main times when estrone concentrations decreased more: at 4 h, at 24 h, and at 28 days. The first decreasing period also included the half-time in estrone degradation, calculated at approx. 8 h, which was the longest of the soils. This soil started with the highest concentration at 4 h (29 ug\(\cdot\)kg\({}^{-1}\)), indicating sorption was less than in the other soils, and finished with the lowest concentration at 28 days (0.9 ug\(\cdot\)kg\({}^{-1}\)). This was also the only soil where enzymatic activity decreased at the beginning of the experiment, from 308 U at 4 h to 266 U at 24 h. It could be that estrone might have had a negative effect on the microbial communities initially, and only later (after 24 h) did they adapt to this pollutant, as this soil had its highest enzymatic activity from day 3 onwards. The hypothesis of microorganism adaptation is supported by the fact that this soil had just one predominant texture (loam); hence, the microorganisms' access to estrone could be considered constant, and not influenced by different textures. Adaptation is supported also by the nutrient characteristics of this soil (the second-best after fluvisol), which would have encouraged a good development of microbial communities. The soil presented a very clear 24 h-3 days transition, this period also demonstrating a clear separation between the enzymatic behaviour stages in the soil. In the first 24 h, as both estrone and enzymes decreased, estrone mobility was attributed to adsorption, mainly, and some microbial activity. The 24 h-3 days transition experienced a relevant increase in activity that was maintained until the end of the experiment and in fact, chernozem's highest average was registered at day 28 (379 U). Analyzed together with the corresponding estrone concentrations, it can be concluded that chernozem needed approximately 3 days to develop estrone-tolerant microbial communities. Before that, estrone was mainly adsorbed on the loam; after that, estrone transformation was mainly performed by microorganisms in a very successful way (lowest E1 values and highest enzymatic activity). Chernozem was the most similar to cambisol, but most different to fluvisol.