Despite receiving a considerable amount of attention in the past, quantitative and systematic estimation of the source contributions for different organic carbons (OCs) in complex river systems is still challenging. In this study, we tested an integrated framework using field data of bulk elements and lipid biomarkers and hydrological modeling (hydrological simulation program FORTRAN, HSPF) for the quantitative estimation of OC loads along different land-use types of a watershed (Geumho River watershed in South Korea). Based on the specific source assignments identified from the lipid biomarker patterns in particulate organic carbon (POC) such as short/long chains of alkanes, fatty acids and alcohols, and coprostanol/cholesterol, spatial variations of the diagnostic lipids could be used as an indicator to discriminate between the contributions of natural (algae, bacteria, and terrestrial plants) and anthropogenic sources (fecal). Based on the integration of HSPF modeling, it was also found that various POC loads might be partially controlled by different water discharges within watersheds. With the increase in POC fluxes, the increase in fecal loads was also noticed, as reflected by the predominant lipid (especially coprostanol normalized by water discharges). As a straightforward approach, we developed a set of indices including fecal index-1, ratios of coprostanol, fatty acids, and alkanes, which strengthened the sensitivity for fecal contamination. Compared with the conventional HSPF results, the variations of these proposed indices were more influenced by the broadened watershed extents with increasing downstream distance, which provided a more accurate estimation of the quantitative contributions of POC loadings in the complex river system.

尽管过去受到了相当多的关注，但是对复杂河流系统中不同有机碳（OCs）的源贡献进行定量和系统的估算仍然具有挑战性。在这项研究中，我们测试了使用散装元素和脂质生物标志物的现场数据以及水文模型（水文模拟程序FORTRAN，HSPF）对流域（Geumho River流域在不同土地利用类型）上的OC负荷进行定量估算的综合框架。韩国）。根据从颗粒有机碳（POC）中的脂质生物标志物模式（例如烷烃，脂肪酸和醇的短链/长链以及香豆素/胆固醇）确定的特定来源分配，诊断脂质的空间变化可以用作区分天然（藻类，细菌和陆生植物）和人为来源（粪便）的指标。基于HSPF模型的集成，还发现流域内不同的排水量可能会部分控制各种POC负荷。随着POC通量的增加，粪便负荷也增加了，这主要是由脂质（特别是通过水排出量归一化的香豆素）所反映的。作为一种直接的方法，我们开发了一组指标，包括粪便指数-1，coprostanol，脂肪酸和烷烃的比例，从而增强了粪便污染的敏感性。与传统的HSPF结果相比，