Elevated Mobility of Persistent Organic Pollutants in the Soil of a Tropical Rainforest

Abstract

Semivolatile persistent organic pollutants (POP) are bioaccumulative and toxic contaminants. Their global distribution depends on source distribution, atmospheric transport, degradation, and the exchange with ocean and land surfaces. Forests are crucial terrestrial reservoirs due to the commonly envisaged high capacity of their surface soils to store and immobilize airborne contaminants bound to soil organic matter. Our results show that POPs can be unexpectedly mobile in the soil of a tropical rainforest due to fast litter turnover (leading to rapid POP transfer to the subsoil) and leaching rates exceeding degradation rates especially for more hydrophobic congeners. Co-transport in association with leaching fine particulate and dissolved organic matter appears as a relevant driver of this PCB export. A markedly different distribution pattern is displayed in this soil in comparison to soils of colder environments with lower overall storage capacity. These findings show that biogeochemistry of organic matter degradation and weathering can influence POP soil fate. Because tropical forests represent 60% of the global terrestrial productivity, the highlighted dynamics might have an implication for the general distribution of these contaminants.

Elevated Urbanization-driven Plant Accumulation and Human Intake Risks of Polycyclic Aromatic Hydrocarbons in Crops of Peri-urban Farmlands

“…This result is consistent with those of previous studies (Marques et al 2016a, b, Qu et al 2020. In urban areas with high pollution levels, soil may become the ultimate environmental fate of PAHs through atmospheric deposition (Agarwal et al 2009, Feng et al 2017, Zheng et al 2015. Some studies point out that the HMW PAHs in soil easily enter the human body through sebum (Beriro et al 2020).…”

The influence of tree species composition on the storage and mobility of semivolatile organic compounds in forest soils

“…ageing of one horizon OM to "become" (or be incorporated into) the adjacent lower horizon). Pedogenesis is expected to result in preferentially incorporating SVOCs with a higher bound to OM in the lower soil layer (Zheng et al, 2015). Within this case, the occurrence of a direct relationship will be interpreted as the effect of secondary transport processes (in the lower adjacent horizon), preferentially affecting less hydrophobic SVOCs.…”

“…We do not have evidence here suggesting sorption to humin to be a crucial process. More recently, Zheng et al have highlighted the important role of the co-transport of PCBs bound to leaching DOC when describing the fast mobilization of these compounds in tropical soils (Zheng et al, 2015).…”

Role of low-latitude forests in modulating forest filter effect on a continental scale: Long-term simulation on PCB-153 in Chinese forests

“…For example, leaves can partly buffer against variations of air temperature (Dong et al, 2017) due to evapotranspiration, requiring a physiological model to estimate POP partitioning between the air and leaf surface, However, the temperature differences between leaf and air were seldom considered in models of POPs, leading to uncertainties in the numerical simulation. Important processes, such as the fast leaching of PCBs in tropical forest (Zheng et al, 2015), bidirectional exchange between air and canopy (Nizzetto and Perlinger, 2012), and dynamic processes in litter (Terzaghi et al, 2017), were seldom considered in traditional regional models of POP fate. New models considering ecophysiological processes have been recently developed and applied to quantify air-canopy-litter-soil exchange (Nizzetto and Perlinger, 2012;Terzaghi et al, 2017).…”