**6. Conclusions**

concentrations (Section 2.4) were used for the MEC value, PNEC was calculated on the basis of the data presented in Table 2, and AF was set at 1000 to ensure reliability (see Table 4).

STZ 400 soybean *Glycine max* (L.) Merr. 42 **9.5**

The data presented in Table 4 support our above statement, as different RQs were obtained, depending on the data used in this evaluation. It seems that a single environmental concen‐ tration, which can differ in time and place, as well as the PEC values, which may also differ in different countries, can lead to the over- or underestimation of the risk posed by these

rice *Oryza sativa* L. 13 **7.7** soil microbe 7 **14.3**

rice *Oryza sativa* L. 13 0.07 soil microbe 7 0.13

rice *Oryza sativa* L. 43 0.25 soil microbe 13 0.84

rice *Oryza sativa* L. 43 0.10 soil microbe 13 0.35

**PNEC=EC50/AF**

**(AF=1000) [µg kg-1] RQ=MEC/PNEC**

**Substance**

SMX

SMZ

**MECsoil**

680 Environmental Risk Assessment of Soil Contamination

100

0.9

11

4.5

**[(µg kg-1] Organism**

**Figure 2.** Risk evaluation of sulphonamides in the terrestrial environment

**Table 4.** RQ calculations for three SAs (RQs >1 are presented in bold)

Our knowledge of the presence of SAs in soils is increasing, but information in the peerreviewed literature regarding the fate and ecotoxicological effects is still limited.

As sorption to the soil matrix governs the transport, persistence and (bio)availability of these chemicals in the environment, it can be assumed that low *Kd* values, together with the physi‐ cochemical properties of these compounds, indicate that they are highly mobile, readily bioavailable and easily transported from soil surfaces to aquifers, causing surface- and groundwater contamination. Being readily bioavailable to micro-organisms, plants and animals, SAs can affect these directly; indeed, they have the potential to affect entire terrestrial ecosystems. The literature records the effects of many SAs on soil organisms, although these are mainly microorganisms and plants; as there are few data on pedofauna, it is impossible to form any clear judgment in this respect. SAs have been detected in soils, and the evidence points to possible effects on soil organisms at environmentally relevant concentrations. Furthermore, SAs can be accumulated by several terrestrial plants, such as the willow *Salix fragilis* L., which could be employed for the phytoremediation of SA-contaminated soils. However, some vegetables are also reported to accumulate SAs, which could lead to adverse effects along the food chain, ultimately affecting human health. Nevertheless, research into bioaccumulation as well as the phytoremediation of these compounds is still needed.

The most and least sensitive endpoints in plant studies are root length and seed germination respectively. The effects of SAs on microorganisms have been studied in many ways, e.g. with single species and multispecies designs, and different endpoints. Most of the available data show a strongly dose-dependent relationship for the explored endpoints. Moreover, their toxicity can be strongly influenced by the pH in the environment and organisms. Furthermore the issue of microorganisms developing antibiotic resistance is related to SAs. Especially when SA-contaminated manure is used, there is a noticeable increase in resistance genes.

Hardly any information has been found concerning the toxicity of SA mixtures in soils. Since these compounds are almost always present in the form of mixtures in the environment, this issue is one to be addressed in the future. Furthermore, there is a lack of data relating to the long-term exposure of non-target organisms, and especially how continuous exposure for several generations may affect a whole population.

In conclusion, the presented data on the fate and potential effects of SAs in the terrestrial environment appear to indicate a possible negative impact on soil ecosystems and imply a threat to public health. However, further studies are necessary to characterize the risk completely.
