Hello! Perhaps the following research articles (or references therein) will be of some assistance to you in your research endeavour:

Metallophytes in Latin America: A Remarkable Biological and Genetic Resource Scarcely Known and Studied in the Region (GINOGNOCCHIO and BAKER, 2004)

http://www.scielo.cl/pdf/rchnat/v77n1/art14.pdf

Removal Process for Arsenic in Constructed Wetlands (LIZAMA et al., 2011)

http://jlakes.org/web/removal-processes-arsenic-CW-C2011.pdf

Assessment of the Phytoremediation Efficacy of Boron Contaminated Waters by Salvinia natans (HOLSTRA et al., 2010)

http://epe.pwr.wroc.pl/2010/holtra_4-2010.pdf

Remediation of Heavy Metal Contaminated Soils: Phytoremediation as a Potentially Promising Clean-Up Technology (MARQUES et al., 2009)

http://www.biotecnologia.web.porto.ucp.pt/sites/default/files/files/Biotecnologia/investigacao/pgcmarquesrcastro.pdf

Metal Uptake, Transport and Release by Wetland Plants: Implications for Phytoremediation and Restoration (WEIS and WEIS, 2004)

http://dzumenvis.nic.in/Microbes%20and%20Metals%20Interaction/pdf/Metal%20uptake%20transport%20and%20release.pdf

some plant have capacity like this

Hello! Perhaps the following research articles (or references therein) will be of some assistance to you in your research endeavour:

Metallophytes in Latin America: A Remarkable Biological and Genetic Resource Scarcely Known and Studied in the Region (GINOGNOCCHIO and BAKER, 2004)

http://www.scielo.cl/pdf/rchnat/v77n1/art14.pdf

Removal Process for Arsenic in Constructed Wetlands (LIZAMA et al., 2011)

http://jlakes.org/web/removal-processes-arsenic-CW-C2011.pdf

Assessment of the Phytoremediation Efficacy of Boron Contaminated Waters by Salvinia natans (HOLSTRA et al., 2010)

http://epe.pwr.wroc.pl/2010/holtra_4-2010.pdf

Remediation of Heavy Metal Contaminated Soils: Phytoremediation as a Potentially Promising Clean-Up Technology (MARQUES et al., 2009)

http://www.biotecnologia.web.porto.ucp.pt/sites/default/files/files/Biotecnologia/investigacao/pgcmarquesrcastro.pdf

Metal Uptake, Transport and Release by Wetland Plants: Implications for Phytoremediation and Restoration (WEIS and WEIS, 2004)

http://dzumenvis.nic.in/Microbes%20and%20Metals%20Interaction/pdf/Metal%20uptake%20transport%20and%20release.pdf

Mash plants such as Cattail may be useful in phytoremediation of these elements.

http://cleantechnica.com/2009/05/16/cattail-army-deployed-to-fight-water-pollution/

If arsenic is present in ground water, fern trees comes under the remedial. The root of the fern trees have property to absorb arsenic from water. Some work already published in this regards.

Yes, some fern species love to soak up the arsenic and keep it in their fond (in the form of arsenate) such as Pteris vittata, Pityrogramma calomelanos.

without toxicity

Arsenic and boron are conservative contaminants/pollutants. They cannot be destroyed, only sequested or imobilized for indeterminate periods. If you remove them from one place by uptake in wetland plants, what do you then do with the plants? Remove them to lanfill where the B and As may eventually remobilize into groundwater?

The following articles includes discussion on the ways of removal of arsenic toxicity in future:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1637429/pdf/envhper00485-0071.pdf

Plants present on arsenic contaminated sites include Agrostis tenuis, Agrostis stolonifera, Agrostis canina, and Jasione Montana; Calluna vulgaris. and Holcus lanatus ; and Ceratophyllum demersum , Pteris vittata and Pityrogramma calomelanos etc. These species were found to accumulate arsenic to high concentrations, which, in some cases, approached percent levels in dry weight http://lqma.ifas.ufl.edu/Publication/Cai-02.pdf

Thank you very much!!!