Is chemical pollution the main cause of wetland water pollution?

Yes. The inflow of chemical wastewater aggravates the organic pollution of the water body in the mangrove wetland near the sewage outlet. Due to the self-purification of the water body and the purification effect of the mangrove wetland, the organic pollution of the water body in the mangrove wetland far from the sewage outlet is significantly reduced. Most of the heavy metals in chemical wastewater are deposited in the sediment near the sewage outlet. When flowing through mangrove wetlands, some heavy metals will be absorbed by plants and purify the water quality.