Earthworm gut digestion drives the transfer behavior of antibiotic resistance genes in layers of extracellular polymeric substances during vermicomposting of dewatered sludge.

Gut digestion by earthworms (GDE) is a crucial step in vermicomposting, affecting the fate of antibiotic resistance genes (ARGs) in vermicompost sludge. The extracellular polymeric substance (EPS) matrix of sludge is an important space for ARG transfer. However, the effect of GDE on EPS-associated ARGs remains unclear. Therefore, this study explored the role of GDE in driving the transfer of ARGs within different EPS layers in sludge. For this, the changes in intracellular ARGs and EPS-associated ARGs in sludge were analyzed after 5 days of the GDE process. The results showed that after the GDE process, both nitrate and dissolved organic carbon significantly increased in all EPS layers of sludge, while the proteins and polysaccharides only enhanced in soluble and loosely bound EPS of sludge. In addition, a 7.0% decrease in bacterial diversity was recorded after the GDE process, with a functional bacterial community structure emerging. Moreover, the absolute abundance of total ARGs and mobile genetic elements decreased by 90.71% and 61.83%, respectively, after the GDE process. Intracellular ARGs decreased by 92.1%, while EPS-associated ARGs increased by 4.9%, indicative of intracellular ARG translocation into the EPS during the GDE process. Notably, the ARGs exhibited significant enrichment in both the soluble and loosely bound EPS, whereas they were reduced in the tightly bound EPS. The structural equation modeling revealed that the GDE process effectively mitigated the ARG dissemination risk by modulating both the EPS structure and microenvironment, with the organic structure representing a primary factor influencing ARGs in the EPS.

[Contents and Health Risks of Organic Phosphorus Esters in Plastic Runway Products].

Using ultrasonic assisted extraction, column chromatograph purification and gas chromatograph-mass spectrometer(GC-MS) analysis method to quantify the contents of seven kinds of organic phosphorus ester(OPEs) in plastic tracks in Chengdu City. The recovery rates of this method ranged from 71.41% to 110.58% and the correlation coefficient (r) of the standard curve was higher than 0.99, which demonstrates satisfying quality control. Plastic track samples were collected from twelve schools in Chengdu. The results show that OPEs are detected in two-thirds of plastic track samples. TnBP[Tri-n-butyl phosphate] and TEHP[tris(2-ethylhexyl) phosphate] were detected with high frequency, while TCEP[tri(2-chloroethyl) phosphate], TDCPP[tridichloropropyl phosphate] and TPhP[triphenyl phosphate] were not detected in any samples. Contents of the total OPEs (Σ7OPEs) in the plastic track ranged from ND to 534.89 ng·g-1. TnBP was identified at the highest content levels (ND-462.18 ng·g-1). TCPP[Trichloropropyl phosphate], a chlorinated phosphate with higher toxicity, was detected in one sample with a contents of 205.94 ng·g-1. The average exposure dose for adults was 0.14 ng·(kg·d)-1, lower than that for children of 0.64 ng·(kg·d)-1. Risk quotients of OPEs for adults and children were only 10-7 -10-5 and could be ignored. These results indicate that the government should limit the consumption, as well as the type of OPEs which are added to plastic tracks, to protect population health.