Orange peel (OP), the main residue of the citrus industry, is usually used for animal feeding and soil fertilisation if more advanced options are lacking. In areas with warm and dry climatic conditions, OP is land-spread for solar-drying on the fields, the leachate produced is a potential pollution factor for soil especially due to the release of organic matter; heavy rainfalls could even aggravate the hazard. Since literature does not report any quantitative evaluation of this risk, this study presents three OP drainage tests in lysimeters, where OP was left releasing leachate on a soil layer. A first test was carried out on raw OP naturally draining, while, in a second and a third test, a rainfall of 100 mm was applied on already drained and solar-dried OP, respectively. After drainage, raw OP reduced its initial volume by about 90% and the leachate production accounted only for about 20% of the initial volume. The simulated rainfall produced even lower volumes of leachate (2–3% of the initial biomass volume), in spite of the high rainfall volume and long drainage time after its application. The COD concentration in the leachate from the raw OP was significantly higher than those produced after simulated rainfall. However, the COD amount released to the soil was negligible. The lysimetric tests showed that the release of leachate occurs mainly during the first phase of drainage and that rainfall is absorbed and does not produce significant leaching. Overall, the risk of soil pollution due to the natural drainage of OP is negligible, due to both limited amounts of leachate and organic loading.

中文翻译：

---

评价桔皮自然排水对土壤的污染风险：初步结果

如果缺少更高级的选择，橘子皮（OP）是柑桔工业的主要残留物，通常用于动物饲养和土壤施肥。在气候温暖干燥的地区，OP被散布到田间进行太阳能干燥，特别是由于有机物的释放，所产生的渗滤液是对土壤的潜在污染因子。暴雨甚至可能加剧这一危害。由于文献没有报告对这种风险的任何定量评估，因此本研究提出了用溶渗仪进行的3种OP排水试验，其中OP留在土壤层上释放渗滤液。第一次测试是对天然OP进行自然排水，而在第二和第三次测试中，分别对已经排水和经太阳能干燥的OP进行了100 mm的降雨。排水后 未加工的OP减少了其初始体积的90％，而渗滤液的产量仅占初始体积的20％。尽管降雨量大且施用后排水时间长，但模拟降雨产生的渗滤液量甚至更低（占初始生物量的2-3％）。原始OP中渗滤液中的COD浓度显着高于模拟降雨后产生的COD浓度。但是，释放到土壤中的化学需氧量可以忽略不计。溶解度测试表明，渗滤液的释放主要发生在排水的第一阶段，并且降雨被吸收并且不会产生明显的浸出。总体而言，由于沥滤液和有机物的含量有限，OP的自然排水导致的土壤污染风险可以忽略不计。