Cape John Neil, van Dijk Netty, Tang Yuk Sim
Centre for Ecology & Hydrology, Bush Estate, Penicuik, Midlothian, UK EH26 0QB.
J Environ Monit. 2009 Feb;11(2):353-8. doi: 10.1039/b813812e. Epub 2008 Oct 31.
Bulk precipitation samplers, which are continuously open, also sample gases and particles deposited on the funnel surface. Wet-only samplers, which open only during precipitation, avoid this problem, but can be bulky (leading to disruption of air flow and droplet collection) and need electrical power. We describe here a simple battery-powered modification to a standard bulk sampler that allows the separate measurement of deposition to the funnel surface and wet deposition by washing the funnel surface when precipitation is detected. Comparison of this design with a standard bulk sampler over 3 months at a site in eastern Scotland showed that dry deposition to the funnel surface contributed around 20% of sulfate, 20-30% of nitrate and 20-40% of ammonium ions. There was also a significant loss of ammonium and nitrate in the modified sampler, presumably in the tubing, even though a biocide had been added to the sample bottles. This observation has implications for bulk samplers of similar design, with a sample bottle at ground level. Deposition of sea salts and calcium was greater to the flushing collectors than to the bulk collectors, implying that regular cleaning of funnel surfaces with 10% methanol solution subtly alters the capture efficiency for larger particles.
连续敞开的大容量降水采样器还会对沉积在漏斗表面的气体和颗粒物进行采样。仅在降水期间敞开的纯湿采样器可避免这一问题，但可能体积庞大（导致气流和液滴收集受到干扰）且需要电力。我们在此描述了一种对标准大容量采样器进行的简单电池供电改造，该改造能在检测到降水时通过冲洗漏斗表面来分别测量漏斗表面的沉积物和湿沉降。在苏格兰东部一个地点，将这种设计的采样器与标准大容量采样器进行了为期3个月的对比，结果表明，漏斗表面的干沉降对硫酸盐的贡献率约为20%，对硝酸盐的贡献率为20 - 30%，对铵离子的贡献率为20 - 40%。在改进后的采样器中，铵和硝酸盐也有显著损失，推测是在管道中损失的，尽管已在样品瓶中添加了杀菌剂。这一观察结果对类似设计且样品瓶位于地面的大容量采样器具有启示意义。海盐和钙在冲洗式收集器上的沉积量比对大容量收集器的沉积量更大，这意味着用10%甲醇溶液定期清洁漏斗表面会微妙地改变对较大颗粒的捕获效率。
