Abstract：
Land use and precipitation are two major factors affecting phosphorus (P) pollution of watershed runoff. However, molecular characterization of dissolved organic phosphorus (DOP) in runoff under the joint influences of land use and precipitation remains limited. This study used Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to study the molecular characteristics of DOP in a typical P-polluted watershed with spatially variable land use and precipitation. The results showed that low precipitation and intense human activity, including phosphate mining and associated industries, resulted in the accumulation of aliphatic DOP compounds in the upper reaches, characterized by low aromaticity and low biological stability. Higher precipitation and widespread agriculture in the middle and lower reaches resulted in highly unsaturated DOP compounds with high biological stability constituting a higher proportion, compared to in the upper reaches. While, under similar precipitation, more aliphatic DOP compounds characterized by lower aromaticity and higher saturation were enriched in the lower reaches due to more influence from urban runoff relative to the middle reaches. Photochemical and/or microbial processes did result in changes in the characteristics of DOP compounds during runoff processes due to the prevalence of low molecular weight and low O/C bioavailable aliphatic DOP molecules in the upper reaches, which were increasingly transformed into refractory compounds from the upper to middle reaches. The results of this study can increase the understanding of the joint impacts of land use and precipitation on DOP compounds in watershed runoff.
摘要：
土地利用和降水是影响流域径流磷污染的两个主要因素。然而,在土地利用和降水的共同影响下，径流中溶解有机磷（DOP）的分子特征仍然有限。本研究使用傅立叶变换离子回旋共振质谱（FT-ICR-MS）研究了典型的P污染流域中DOP的分子特征，该流域具有空间可变的土地利用和降水。结果表明,降水少,人类活动强烈,包括磷酸盐开采和相关行业，导致上游脂肪族DOP化合物的积累，具有低芳香性和低生物稳定性的特点。中下游较高的降水和广泛的农业导致高度不饱和的DOP化合物具有较高的生物稳定性，与上游相比。同时,在类似的降水下，相对于中游，由于城市径流的影响更大，较低芳香性和较高饱和度的脂肪族DOP化合物在下游富集。由于上游地区普遍存在低分子量和低O/C生物可利用的脂肪族DOP分子，光化学和/或微生物过程确实导致了径流过程中DOP化合物特征的变化，从上游到中游越来越多地转化为难熔化合物。这项研究的结果可以增加对土地利用和降水对流域径流中DOP化合物的联合影响的理解。
