Trace metal flows and balances in small-scale vegetable production systems in periurban areas of China and Vietnam

摘要

The aim was to study sources, flows and balances of trace metals in intensive peri-urban vegetable farming systems in peri-urban areas of China and Vietnam. Animal manure was the major metal source at three study sites whereas waste water was the main metal contributor at one site. The inputs of Cu and Zn ranged between 0.4-4.0 and 2.1-5.4kg·ha<,-1>·yr<'-1>, respectively, and the outputs between 0.1-0.3 and 0.5-1.4kg·ha<,- 1>·yr<,-1> leading to high surpluses. The present soil metal concentrations were well below the national standards, but current metal load could lead to soil accumulation reaching the maximum allowable soil concentrations within a few decades. Metal contaminated inputs, e. g. trough application of biosolids and wastewater, in intensive vegetable systems might be of concern related to crop quality and food safety (mainly Cd), soil quality (mainly Cu and Zn) as well as potential impact on surface and groundwater quality.