Barton will lead to books and some documents from the USGS and EPA. Try searching Subject Keywords combinations such as phosphorus, phosphate, environment*, anaylysis, water content. Here are some examples:
The highly acclaimed Encyclopedia of Analytical Chemistry provides a much needed professional level reference work for the 21st Century. Encyclopedia of Analytical Chemistry is the most comprehensive analytical chemistry reference available, covering all aspects from theory and instrumentation through applications and techniques. All fields of chemical research are covered: analytical, organic, physical, polymer, inorganic biomedical, environmental, pharmaceutical, industrial, petroleum, forensics and food science.