Metal Leaching from Canal-Top Photovoltaic Modules Under Outdoor Static Water Immersion: Experimental Evidence and Water-Quality Implications for a Drinking-Water Transfer Canal

Installing solar corridors (photovoltaic, PV) over drinking-water transfer canals can combine renewable power with land and water savings, but direct module-water contact raises questions about metal release and water-quality safety. Two-season outdoor static-immersion experiments were conducted with commercial crystalline-silicon modules (LONGi P-type, TOPCon and IBC; CHINT TOPCon), intact and damaged. In autumn (8 d), only As and Ni were detectable (0.22–0.35 and 0.53–2.60 µg/L); As stabilized within 12–24 h, whereas Ni rose gradually, and Pb, Cd and phenol were only sporadically detected near detection limits. In spring (66 d), Cu, Fe, Mn, Zn, As and Ni were released at µg/L levels (maxima 105, 48, 6.6, 5.9, 1.0 and 2.4 µg/L, respectively), with Cd, Cr(VI) and Hg undetectable. Cu dominated, exceeding the GB 3838-2002 Class I limit (10 µg/L) but remaining well below Class II and drinking-water limits (1.0 mg/L). Fe, Mn and Zn peaked within 6 d, whereas Cu showed a unique corrosion-driven secondary-release phase at 8–17 d, stabilizing only after 24 d. Damage severity did not monotonically control release in the single pools tested; the intact-module pool showed the highest Cu, Mn and Ni, pointing to corrosion of exposed Cu-bearing components. Scaling measured fluxes to a 350 m3/s canal discharge (1 km corridor) gives steady-state increments of ~10−4 µg/L for the campaign-average release rate and ~4 × 10−3 µg/L for the maximum observed interval-rate scenario, both far below regulatory limits, supporting a low water-quality risk for the measured analytes under the tested conditions, as measured in the context of this limited study.