**6. Factors of PBDE plant uptake**

Numerous studies focused on both physico-chemical and substance specific properties affecting plant uptake and biodegradation behavior of PBDE, where PBDE specifics (vapor pressure, KOW value, air-water distribution KAW value, air-plant distribution KAP value), environmental parameters (temperature, wind rate, precipitation, temporal rain distribution, kinetics of both gaseous and particle-bound deposition), plant properties (species, lipid content, foliage morphology, ratio of non-lipid plant parts, rind thickness, contents of both sugar and fibers), as well as the presence of an microbial active rhizosphere were generally found to be highly germane. For bioavailability and thus biodegradability of PBDEs pH value and soil composition are of particular importance [18, 22, 23]. In detail, relevant parameters are:

#### **6.1 Excretion of plant solubilizers**

Easy metabolizable intermediates as amino acids, organic acids, sugars and exozenzymes are excreted by plants as detoxification strategy to improve microbial bioavailability and biodegradability of PBDE in the rhizosphere [33]. For example, hexose was excreted by *Kandelia obovate* to enhance microbial debromination of BDE-99 to Br2-BDEs and Br3-BDEs in soil [55].

#### **6.2 Plant specifics**

Plant specifics like plant morphology, wax layers of bay leaves and the lipid content of both leaf and roots strongly affect both atmospheric and soil-based uptake of PBDEs. Hence, accumulation of Br3-BDEs to Br10-BDEs in the wax layer of wheat was determined as 29–93% of the total plant uptake [25], while BDE-209 accumulation in six different plant species at initial soil levels of 4700 ng g DM−1 ranged 1822–10,933 ng plant−1 with alfalfa showing lowest and maize showing highest levels [56].
