The fate of sulfonamides in microenvironments of rape and hot pepper rhizosphere soil system.

Sulfonamides (SAs) in agricultural soils can be degraded in rhizosphere, but can also be taken up by vegetables, which thereby poses human health and ecological risks. A glasshouse experiment was conducted using multi-interlayer rhizoboxes to investigate the fate of three SAs in rape and hot pepper rhizosphere soil systems to examine the relationship between the accumulation and their physicochemical processes. SAs mainly entered pepper shoots in which the accumulation ranged from 0.40 to 30.64 mg kg ^-1 , while SAs were found at high levels in rape roots ranged from 3.01 to 16.62 mg kg ^-1 . The BCF _{pepper shoot} exhibited a strong positive linear relationship with log D _ow , while such relationship was not observed between other bioconcentration factors (BCFs) and log D _ow . Other than lipophilicity, the dissociation of SAs may also influence the uptake and translocation process. Larger TF and positive correlation with log D _ow indicate preferential translocation of pepper SAs. There was a significant ( p  < 0.05) dissipation gradient of SAs observed away from the vegetable roots. In addition, pepper could uptake more SAs under solo exposure, while rape accumulated more SAs under combined exposure. When SAs applied in mixture, competition between SAs might occur to influence the translocation and dissipation patterns of SAs.