**6.4 Specific root and leaf surface**

A correlation between accumulation of PBDEs and high specific plant surface was clearly shown for BDE-209 in roots of radish, lettuce and taro [58, 59] and for Br2-BDE to Br10-BDE in both pine needles and eucalyptus leaves [60].

## **6.5 Lipid content**

The lipid content of a plant, especially of the roots, shows strong effects on PBDE uptake and was successfully evaluated for various mosses, lichens, ryegrass, alfalfa, maize, radish, squash, and pumpkin. A positive correlation between lipid content and PBDE uptake (RCF), as well as a negative correlation in lipid content and intrinsic PBDE mobility (TF) was observed [19, 22, 61, 62].

## **6.6 Organic content of the soil**

Similar to the lipid content an increase in organic content of soil evokes higher PBDE accumulation in the soil and, therefore, reduced PBDE plant uptake [20, 33, 63]. Exemplarily, PBDE uptake in carrots was reduced by 31.5–69.8% and soil-based biodegradation increased by 8.6–28.5% by addition of 1–4 w% of swine manure to the soil fraction [63]. Differentiation between TOC and DOC showed a clear improvement in adsorption of PBDE in the soil matrix at higher TOC levels, whereas no effect was observed in case of increased DOC levels [54].

### **6.7 Biochar**

Since biochar is insoluble and thus is considered as a TOC increase of the soil, elevated accumulation of PBDE in the soil phase may occur [64].

#### **6.8 Sewage sludge**

As sewage sludge reveals a high TOC content, but also enhanced contamination levels with PBDE or their detoxification and degradation products, sewage sludge is a dominant PBDE exposure pathway. Hence, using contaminated sludges as agricultural fertilizers, increasing concentration levels and accumulation of PBDE in the soil phase and, finally, elevated PBDE plant uptake are observed. However, relevance of this effect strongly depends on the original PBDE contamination levels of the sludge. An overview of PBDE levels in different sewage sludges was

**73**

**Figure 1.**

*Plant Uptake, Translocation and Metabolism of PBDEs in Plants*

longer PBDE load may be expected at wet locations.

previously presented [52]. Similar to both lipid content and TOC content, a negative correlation between BDE-209 uptake and organic content, implemented by sewage

In difference to sewage sludge, the PBDE load of compost and digestates is rather low as confirmed by various studies due to the low contamination levels of the plant educts (leaves, green waste, fruit and food residues). For instance, a broadly based study of biocompost, green waste compost and digestates in Baden-Wuerttemberg showed comparable median concentrations of 13 ng g DM−1, 5.4 ng g DM−1, and 13.7 ng g DM−1 and confirmed to low relevance of these materials as

As a result of the low water solubility of PBDE, high soil moisture effectively prevents evaporation of BDEs as well as plant uptake [64]. Correspondingly, a

Plastics may reveal partition coefficients of PBDEs of several orders of magnitude higher than those towards sewage sludge or soil at levels of 0.04–1.6 w% [66, 67]. In detail, accumulation of PBDEs in low density polyethylene films (LDPE), an adequate and commonly accepted model for diffusive transport phenomena across biomembranes, showed accumulation factors against the aqueous phase (KPEW) of

in case of 23 BDE congeners covering the total spectrum of bromination

*Correlation of log KOW and log BCF of 25 BDEs of high environmental relevance (*−*3,* −*7,* −*17,* −*28,* −*30,* −*47,*  −*49,* −*66,* −*85,* −*99,* −*100,* −*123,* −*153,* −*154,* −*155,* −*183,* −*184,* −*191,* −*197,* −*201,* −*202,* −*206,* −*207,* −*208,* 

−*209) applying simple mathematical models with/without correction.*

[68]. Furthermore, a curvilinear correlation between the log KPEW and log KOW factor, very similar to the correlation of BCF and log KOW shown in **Figure 1** was observed and explained by energy barriers for diffusive transport into the LDPE structure [68]. The statement of rising KPEW levels at higher lipophilicity of BDE congeners was further confirmed [67]. However, KPEW levels are strongly affected

*DOI: http://dx.doi.org/10.5772/intechopen.95790*

sludge out, was observed [37].

**6.9 Compost and digestate**

PBDE emissions sources [65].

**6.10 Soil humidity**

**6.11 Plastic particles**

105 –107 previously presented [52]. Similar to both lipid content and TOC content, a negative correlation between BDE-209 uptake and organic content, implemented by sewage sludge out, was observed [37].
